Resistance Training For Seniors -

Resistance Training for Seniors

Seniors undergo significant physiological changes as they age, including hormonal secretions, muscle atrophy, and decreased bone density. These changes can have a profound impact on their overall function and independence. An effective resistance training program can help mitigate these physiological declines, enhance physical capabilities, and improve the quality of life for seniors. The key principle is that systems, tissues, and cells improve only when they are actively used, and this holds true for skeletal muscles and other bodily systems.

Benefits for Seniors: Seniors, regardless of age, can benefit from properly designed resistance training programs. This includes both men and women, even those of advanced age. While age is a factor, it is just one component among many, including nutrition and physical activity level, that can be modified to enhance physical capabilities. Despite the nonmodifiable factors like age, genotype, and sex, exercise remains a crucial modifiable determinant of physiological function. Resistance training can positively influence physiological function at various levels, from cellular to whole-body performance. It offers numerous advantages for seniors, even those with chronic illnesses, by improving health, functional abilities, and overall quality of life.

Preservation of Independent Living: One of the most significant outcomes of resistance training for seniors is the potential to improve their level of normal life or spontaneous physical activity. This contributes to preserving independent living, which is highly valuable for a wide segment of the senior population.

Physiological Changes with Age: Designers of programs for seniors must have a deep understanding of the physiological changes that occur as individuals age. Endocrine secretions of hormones like testosterone, growth hormone, and estrogen tend to decrease with age, impacting various aspects of health and physical performance. The section begins by discussing the hormonal changes associated with resistance exercise.

Changes in Body Composition: Another section delves into age-related changes in body composition, which often involve increased fat mass and decreased muscle and connective tissue quality. These changes can significantly affect physical performance and health outcomes.

Age-Related Performance Changes: The section then examines age-related performance changes and how resistance training adaptations can enhance physical capabilities, including strength, endurance, and mobility.

Principles for Resistance Training Program Design: The final section presents fundamental principles for designing resistance training programs specifically tailored to the senior population. This includes considerations for exercise selection, intensity, volume, and progression. These principles are essential to maximize the benefits of resistance training for seniors, ensuring safe and effective programs that promote health, function, and independence.

Hormonal Changes With Age and Their Relationship to Resistance Training

Aging is marked by a natural decline in the endocrine system’s ability to secrete hormones. The endocrine glands, like other structures in the body, go through a process of cellular aging. Resistance exercise and training can potentially offset the extent of this decline by stimulating endocrine glands to synthesize and release hormones necessary for metabolic homeostasis during exercise and anabolic signaling during recovery.

Endocrine System in Aging: As individuals age, their endocrine system’s capacity to release hormones in response to exercise diminishes. This natural aging process can be mitigated through regular exercise. In the absence of exercise, the decline can be even more pronounced due to disuse. The compromised function of the endocrine system leads to decreased resting levels of hormones, including anabolic hormones. Older adults may exhibit a reduced responsiveness to resistance exercise stimuli, as observed in early studies on testosterone and growth hormone. This indicates the importance of exercise in maintaining hormone balance and function. Increases in catabolic hormones and inflammatory cytokines can also occur with age, contributing to heightened protein breakdown and inflammation. These changes are particularly concerning for seniors due to their decreased ability to promote protein synthesis and combat inflammatory processes. A well-structured resistance training program can help counteract these age-related hormonal changes.

Role of Anabolic Hormones: Anabolic hormones like growth hormone play a vital role in mediating various physiological mechanisms and facilitating muscle tissue remodeling and growth. These hormones can be stimulated during and after resistance exercise, effectively signaling the body to adapt to training stimuli. The section provides insight into the age-related changes in hormones and explores their interaction with resistance exercise. Resistance training serves as a powerful tool to modulate these hormonal changes, promoting better health and physical well-being in seniors.

Hormonal Changes With Age: Testosterone and Resistance Training

Testosterone as a Key Hormonal Signal: Testosterone plays a crucial role in regulating various physiological functions, cellular growth, and homeostasis. It acts as a messenger to target tissues like muscles and bones, affecting their development and function. The concentration of testosterone in the blood is linked to the amounts released, degraded, or bound to target receptors. Binding proteins can extend the half-life of a hormone circulating in the bloodstream. Circulatory changes are responsive to these factors, and increases in the blood imply that hormone production has surpassed breakdown and binding to target tissues, leading to lower blood concentration. Elevated resting hormonal concentrations typically result in small regulatory adjustments in normal homeostatic function.

Testosterone Changes With Age: Resting testosterone concentrations and the magnitude of their response to acute resistance exercise tend to decrease with age, especially in men. Studies have shown that older untrained men (62-70 years) experience significantly lower increases in blood concentrations of free and total testosterone in response to resistance exercise when compared to younger men (≤32 years). However, resistance training has been shown to enhance the magnitude of the exercise-induced testosterone response in older men, though not to the level of younger individuals. Short-term training doesn’t appear to affect resting testosterone concentrations.

Free Testosterone: Free testosterone, which is not bound to a binding protein, is essential for binding with receptors and mediating various physiological processes. The amount of free testosterone depends on the total hormone concentration in circulation. In some cases, short-term periodized training has been found to increase resting free testosterone in younger men but not in older men.

Hormonal Changes in Middle-Aged Men: Studies have yielded mixed results regarding hormonal responses in middle-aged men. While some have observed increased total testosterone in response to exercise, others haven’t found changes in resting or exercise-induced testosterone concentrations with resistance training.

Hormonal Responses in Women: Women typically have much lower testosterone concentrations compared to men. In women, testosterone is secreted primarily by the adrenal cortex and to a lesser extent by the ovaries. Older women do not show acute increases in testosterone following resistance exercise. Younger women, however, have displayed significant increases in total and free testosterone after resistance exercise, although these concentrations are notably lower than those in men. The age of women seems to be a determining factor, with younger women exhibiting greater testosterone responses to resistance exercise compared to older women.

Significance of Anabolic Signaling: The age-related decrease in resting and exercise-induced testosterone responses to resistance exercise can have an impact on physiological targets like skeletal muscles, satellite cells, and motor neurons. Despite these declines, even small improvements in signaling appear to benefit the adaptive changes in tissues needed to mitigate the aging process and the associated deterioration in cellular structure and function.

Age plays a significant role in determining the effects of resistance exercise on testosterone levels, but other factors, such as genetics, prior training history, and diet, may also contribute to the extent of changes. The age at which these changes become evident, referred to as “gonadopause” in men, requires further research to establish.

Cortisol and Its Role in Aging and Resistance Training

As individuals age, complex interactions take place among inflammatory processes, the immune system, and the adrenal cortex. Exercise, which can induce stress and inflammation in the body, plays a significant role in these processes, especially in the context of aging. Cortisol, a stress hormone with various roles in the body, is involved in these interactions.

Cortisol’s Multiple Roles: Cortisol, often referred to as a stress hormone, serves various functions in the body. It acts as an anti-inflammatory agent and helps protect glycogen stores. Increased cortisol concentrations in the body are associated with a range of catabolic influences, such as inhibiting the anabolic signals of testosterone at the gene level in cell nuclei, inactivating immune cells crucial for tissue repair, blocking downstream signaling systems for protein synthesis (e.g., mTOR), and promoting protein breakdown to conserve glycogen usage.

Resistance Training and Cortisol: Resistance training has been explored as a means to reduce resting cortisol concentrations and, in some cases, diminish the cortisol response to various stressors, including exercise and environmental or psychological stress.

It’s important to note that intense exercise stressors, such as high-intensity aerobic exercise or weightlifting involving significant muscle groups and multiple sets, can lead to an increase in cortisol levels in the bloodstream. Some studies have indicated that resistance exercise training can lead to changes in the blood cortisol response, resulting in an improvement in the “testosterone-cortisol ratio” in older men, although this effect is not as evident in older women. Research has shown that short-term resistance exercise training can lead to reduced resting cortisol concentrations in the blood in older men (62 years). Even after training, the magnitude of the cortisol response to resistance exercise stress is diminished, signifying a reduction in the stress response.

While these findings suggest the potential for resistance training to influence cortisol levels, further research is needed to better understand the interactions between testosterone and cortisol in the context of the anabolic and catabolic signaling pathways, particularly in aging individuals.

Growth Hormones and Aging: Implications for Resistance Training

Growth hormone (GH) has garnered attention in the context of aging, with many claims regarding its use in anti-aging therapies. While the public has shown interest in GH for anti-aging, the scientific support for its benefits remains limited. Claims about GH administration often lack strong empirical evidence. For example, some of the reported increases in lean tissue attributed to GH may be due to water retention rather than true muscle growth. It’s worth noting that exogenous GH administration has not demonstrated a greater increase in muscle mass compared to resistance training in elderly individuals who do not receive GH.

Exogenous GH use, which is the administration of GH from an external source, carries certain risks, and its potential benefits are not as significant as previously believed. Given these risks and the limited benefits, optimizing resistance training programs may be a more favorable approach to address the effects of aging.

As discussed previously, natural GH consists of over 100 variants beyond the classic 191 amino acid 22 kD monomer produced by the anterior pituitary. It is suggested that many of these GH variants, especially the higher-molecular-weight aggregates, have important anabolic functions due to their relatively high concentrations. However, these higher-molecular-weight bioactive GH variants are believed to diminish with age, further contributing to age-related hormonal changes.

GH is involved in complex physiological processes, and studies examining GH responses in older individuals have mainly focused on the 22 kD isoform. It is important to note that the acute responses of GH to resistance exercise differ with age. In response to acute 10RM resistance exercise, younger men tend to experience an increase in GH levels, while this response is not as prominent in older men or women.

In scenarios where both older and younger men are matched for activity levels and subjected to a 10RM protocol with four sets, both groups exhibit increased post-exercise GH levels. However, the increase is significantly higher in younger individuals (around 30 years) compared to older individuals (around 62 years). With 8 to 10 weeks of training, limited acute GH changes are observed in older men, suggesting that more extended training periods (e.g., over six months) may be required for substantial alterations to occur. It is important to note that other GH variants may change on a faster timeline than what can be captured by the adaptations seen in the 22 kD isoform. Thus, further research is needed to unravel the complexity of the anterior pituitary gland’s responses.

When comparing older and younger individuals, higher GH values are typically a result of higher work or metabolic capacity in younger individuals. The ability to increase GH concentrations after a resistance exercise session can be enhanced with training in older individuals, although typically not to the same extent as in younger individuals. These observations suggest that the aging process affects the hypothalamic-pituitary axis, limiting its capacity to produce GH or its variants.

Insulin and Insulin-Like Growth Factor I in Aging and Resistance Training

In individuals of all ages, an increase in body fat can have detrimental effects on insulin sensitivity. Resistance exercise, however, has been shown to enhance insulin sensitivity, particularly in older individuals with diabetes or compromised insulin sensitivity due to conditions like obesity. An acute response to resistance exercise includes a decrease in insulin concentrations in the fasted state. Longer-term training, such as six months, has demonstrated improved insulin sensitivity in older individuals aged 65-74, who had developed insulin resistance due to physical inactivity and obesity. Moreover, resistance training in the 7- to 9-repetition maximum (RM) zone over a 26-week period led to reduced levels of glycosylated hemoglobin (HbA1c) in diabetic men and women aged 39 to 70. These positive effects on insulin resistance and blood sugar control are particularly significant since many individuals with conditions like diabetes can safely engage in resistance training.

As individuals age, resting concentrations of insulin-like growth factor I (IGF-I) tend to decrease. In a 10-week training program, IGF-I levels were consistently higher in younger men compared to older men, both before and after training, in the acute post-exercise phase and at rest. Additionally, only the younger men showed an increase in IGF-I binding protein-3 after training. It’s worth noting that frail elderly individuals have displayed increased IGF-I staining in muscle following chronic resistance training, linked to increased type II muscle hypertrophy.

In the case of older men aged 67-80, who performed two sets of 12RM and four sets of 5RM, increases in blood total and free IGF-I levels were observed immediately after a workout and six hours post-exercise. However, no changes were detected in the binding proteins. Interestingly, with training, resting IGF-I and binding proteins displayed no significant alterations, implying that the acute response of IGF-I might play a more critical role in IGF-I-related adaptations, with acute signaling to nuclear DNA being the key to endocrine function.

For older women around 68 years of age with low bone mineral density, resistance training had a notable impact. Before training, concentrations of IGF-I, along with the binding proteins, were significantly lower than in age-matched healthy women. The resistance training program resulted in increased resting IGF-I concentrations, but no changes were noted in the binding proteins. It was hypothesized that in women with low bone mineral density, stimulating IGF-I through training might contribute to improved physiological function.

Additionally, some research has shown that despite increased strength, power, and muscle size in women aged 64 years, there were no significant changes in resting IGF-I after 21 weeks of training.

Estrogen and its Implications in Aging and Resistance Training

In a manner analogous to how testosterone decreases in aging men, women also experience a decline in the sex hormone estrogen as they age. This decrease in estrogen levels coincides with a period known as menopause, signifying the cessation of the menstrual cycle. The reduction in estrogen plays a substantial role in the age-related loss of strength, muscle mass, and bone mineral density in women.

Resistance exercise, particularly when performed at high intensity (around 80% of one-repetition maximum or 1RM), has demonstrated its ability to preserve bone mineral density in postmenopausal women. In addition to the preservation of bone density, resistance exercise has been linked to strength and muscle mass gains in postmenopausal women. The importance of periodized resistance training with heavier resistances is emphasized, as it seems to be instrumental in optimizing the desired outcomes on estrogen’s target tissues in women.

Implications of Endocrine Changes with Age

Chronic engagement in a resistance training program alone cannot fully maintain endocrine function, especially regarding resting endocrine concentrations. While the acute hormonal responses to resistance exercise workouts may be diminished in older men and women, training tends to improve post-exercise responses. Hormones in the body, such as those discussed in the earlier sections, play crucial roles in muscle regeneration after mechanical damage, which is relevant for both younger and older individuals. The changes in acute responses to resistance exercise can enhance endocrine secretions when they are most needed, directly following mechanical stimulation of muscle, tissue, and bone. This effect potentially contributes to the strength and muscle fiber changes observed in seniors.

It’s crucial to understand that resistance training programs do not exclusively train skeletal muscle but also affect other systems, tissues, and, as discussed here, endocrine glands. To combat the effects of aging and disuse, these glands must be challenged similarly to skeletal muscle. Proper implementation and design of a resistance training program, which involves personalization, periodization, and appropriate progression, are essential to create an effective exercise stimulus while minimizing the potential for injuries or overreaching and overtraining syndromes.

Understanding the acute hormonal responses to exercise is valuable for comprehending the adaptations that take place in muscle, bone, and other tissues during resistance training. This understanding also aids in interpreting changes in body composition, the subject of the subsequent section.

Effects of Body Composition Changes on Aging and Resistance Training

Body composition refers to the distribution of fat mass and various components of fat-free mass, including muscle, bone, tissue, and organs in the body. As individuals age, various elements of body composition undergo changes, which are discussed in this section. The focus includes the effects of these changes on resting metabolic rate and a conversation about the alterations in bone, tissue, and muscle with aging. The section also delves into how resistance training can counteract these changes, particularly in terms of metabolic rate, muscle, bone, and tendon, in order to help individuals maintain function as they age. The overall performance implications of these age-related muscle and body composition changes will be addressed later in this section.

Resting Metabolic Rate and Its Reduction with Age

One key factor influencing body composition in seniors is the resting metabolic rate (RMR), which represents the energy expended during complete rest for essential physiological functions like heart rate and breathing. RMR tends to be lower in older adults (aged over 60) compared to their younger counterparts (aged 20-35), even after accounting for factors like fat-free mass, fat mass, and smoking history. Notably, some studies have found that women who lived to at least 95 years of age had surprisingly low RMRs in comparison to middle-aged women. This suggests that very old women’s overall health rather than age alone influenced their RMR. Research has also shown that RMR typically decreases by about 5% each decade in men and 4% in women. Additionally, this decrease is more pronounced in men aged 70 to 80 compared to those aged 40 to 50.

Increased fat deposition often coincides with a decrease in metabolic rate. As people burn fewer calories at rest due to their reduced metabolic rate, aging can make individuals more prone to increased fat mass. It’s essential to note that RMR is closely associated with fat-free mass, and resistance training can help increase or slow the decline in fat-free mass, making it a valuable lifestyle intervention to offset the age-related decline in RMR.

Lean tissue mass is a significant factor linked to metabolic rate. Various factors, including muscle mass and lean tissue, influence RMR. The decrease in metabolic rate is often accompanied by a decrease in muscle tissue, leading to a reduction in the mass of other tissues and organs and their specific metabolic rates. Skeletal muscle is estimated to account for roughly 18-25% of resting energy expenditure. Resistance training can optimize metabolic rate among older adults. A study observed that a 24-week resistance training program increased resting metabolic rate by 9% in both young and older men, though not in younger or older women. The absence of a metabolic response in women might be attributed to the training program’s ineffectiveness in increasing lean tissue mass, as the low-volume training protocol used in the study was insufficient to stimulate significant lean tissue gains in women.

Bone Density Changes in Seniors and the Impact of Resistance Exercise

Aging is accompanied by a decrease in bone density, which is especially evident in postmenopausal women but is a significant concern for both sexes. This decline in bone density is associated with conditions like osteoporosis, which can lead to hip, wrist, and rib fractures, with hip fractures being a particular concern among the elderly. It’s noteworthy that only about half of seniors regain independence after experiencing a hip fracture, and one-year mortality rates after a hip fracture can range from 15 to 24%. Notably, these fractures often occur from a standing position, highlighting the importance of taking proactive measures to maintain healthy bone density. Fractures are a considerable worry, but other joint concerns also affect seniors.

Resistance training is an effective strategy to increase bone density in seniors, with the potential to yield a yearly bone density increase of 1% to 3%. In contrast, those who do not engage in resistance exercise may experience a decrease of about 1% to 3% in bone density over the same period. This positive impact of resistance training on bone density can be attributed to its ability to enhance markers of bone formation and decrease markers of bone resorption, ultimately leading to greater bone formation. However, it’s crucial to prescribe resistance training appropriately, as bone adaptation is closely tied to the strain imposed on it, including the strain induced by muscle activity during resistance exercise. This underscores the importance of using a resistance level that is sufficiently challenging to elicit bone adaptations.

Notably, muscular strength and lean body mass are among the most reliable predictors of bone mineral density. Despite engaging in activities that exert stress on their lower body bones, such as running, runners tend to have lower bone density than sedentary individuals, but this deficiency can be addressed through resistance exercise. In older women aged 45-65, a 24-week linear periodized resistance training program yielded no changes in bone density, despite improvements in muscular strength, suggesting that a longer training duration may be required to influence bone density. On the other hand, older men who followed a linear periodization program for 24 weeks displayed an increase in spinal bone density, largely attributed to the ability to work at higher absolute training intensities compared to older women. In older women, more intense resistance training programs (e.g., 80% of 1RM for 8-10 repetitions) have shown significant increases in femoral and lumbar spine bone density. This, however, might require a year or more of consistent training to produce observable bone density improvements. Moreover, resistance training can improve balance, overall physical activity levels, and muscle mass, which are all beneficial for older adults.

Tendon Changes With Age and the Role of Resistance Exercise

Tendons are crucial connective tissues that link muscles to bones and play a significant role in transmitting muscular force to the skeletal system. The muscle-tendon complex (MTC) describes the intricate relationship between muscles and tendons. Muscle-tendon stiffness, in particular, is the force required to lengthen a tendon to a specific extent, and increased stiffness indicates a stiffer MTC. As individuals age, the dynamics of muscle architecture and tendon mechanical properties go through alterations. However, several months of resistance training can potentially lead to enhancements in both muscle force production and tendon mechanical properties. For instance, a study demonstrated that 14 weeks of resistance training resulted in a 10% increase in muscle fiber fascicle length and a remarkable 64% increase in tendon stiffness. It’s important to note that resistance training didn’t affect the relative length-tension properties of the muscle, implying that the increased tendon stiffness and fascicle length balanced each other out.

Tendons are in parallel with muscles, and their mechanical properties, including stiffness, significantly impact the efficiency of force transmission as well as the force-length-velocity relationship within the functional unit. A study observed that the patella tendon in elderly individuals (with an average age of 74.3 years) increased in stiffness following 14 weeks of resistance training compared to sedentary controls (average age of 67.1 years). The resistance training program included leg press and leg extension exercises comprising two sets of 10 repetitions at 80% of 5RM, three times a week. Researchers concluded that these gains in tendon stiffness might contribute to a reduction in tendon injuries and potentially improve functional task completion times. Although the optimal resistance training protocols for enhancing tendon strength and stiffness have not been fully elucidated, there is evidence to suggest that resistance training may be beneficial in reducing tendon injuries, enhancing tendon stiffness, and consequently improving overall force transmission in the elderly population.

Tendinopathy, which is the degeneration of tendons and often manifests without symptoms, is best addressed with an eccentric exercise program. This approach has been employed at the Achilles, patella, and rotator cuff tendons. In the case of young individuals, it has been linked to clinical success, such as the absence of pain during activities and the restoration of more normal tendon structure. However, it’s important to note that the effectiveness of eccentric training in elderly populations has not been thoroughly investigated. Additionally, the ideal eccentric training program for targeting tendons has yet to be fully established.

Loss of Muscle With Age and Its Implications

A well-established phenomenon is the age-related changes in muscle properties. Numerous studies have shown a decline in muscle mass as individuals grow older. While various terms like “sarcopenia” have been used to describe this loss of muscle mass and muscle strength or function, there is no universally accepted definition for it. Sarcopenia is often associated with several factors, including the replacement of muscle fibers with fat (a phenomenon seen in the marbled sections of red meat), fibrosis, increased inflammatory responses, obesity, reduced anabolic signaling, and the degradation of the neuromuscular junction. Consequently, there is a constellation of catabolic influences that contribute to muscle aging.

As people age, the number of motor units decreases. A study using computerized EMG single motor unit analyses estimated a 47% reduction in the number of motor units in older individuals aged 60 to 81. The quadriceps cross-sectional area of muscle in women in their 70s was found to be 77% of that in women in their 20s. This decline in muscle mass is due to a reduction in the cross-sectional area of individual muscle fibers, the loss of individual muscle fibers, or both. This loss of muscle mass becomes more noticeable after the age of 50, although it starts becoming apparent around age 30.

Notably, the muscle fibers lost due to aging are often replaced by fat or fibrous connective tissue. In addition to the reduction in muscle mass, intramuscular fat increases, particularly in women. Older individuals tend to have twice as much non-contractile tissue in their muscles compared to younger individuals. Hence, changes in muscle composition, beyond just the loss of muscle mass, are taking place in aging muscles.

Furthermore, there appears to be a preferential loss of type II muscle fibers with aging, which is detrimental to power capabilities. The number of muscle fibers in the vastus lateralis, an area in the quadriceps muscle, was found to be lower by approximately 23% in elderly men aged 70-73 compared to young men aged 19-37. The decline is more pronounced in type II muscle fibers, causing a compression of motor units and fibers. This compression can adversely affect strength, power, speed, and functional abilities.

A range of mechanisms might contribute to the loss of muscle fibers with aging. These mechanisms include muscle cell death (apoptosis), loss of nerve connections with muscles (denervation), and the restoration of these connections with increased activity (re-innervation). Denervation of motor units occurs with age, leading to the death of alpha motor units and their associated muscle fibers. This loss of muscle fibers compromises the ability of individual motor units to produce force and impacts the basic metabolic functions of the entire muscle, leading to a reduced resting metabolic rate due to decreased muscle mass. Although resistance exercise can lead to the hypertrophy of existing muscle fibers, motor unit loss is irreversible.

Changes in Physical Performance With Age

The changes in body composition and muscle loss, particularly the loss of type II motor units, play a crucial role in determining physical performance as individuals age. Several key aspects of these changes are described in this section.

Patterns of Strength Loss With Age:

Strength is a fundamental factor in maintaining functional abilities, even though the loss of muscle strength may not always be the primary contributor to a reduction in physical performance. In fact, a study found that relative strength was a critical predictor of physical performance in older men, while body mass index (BMI) was a more important predictor in older women. Muscle weakness can reach a point where an elderly person cannot perform basic daily activities, which can increase the likelihood of nursing home placement.

Typically, strength peaks between the ages of 20 and 30, after which it remains relatively stable or slightly decreases over the next two decades. A more significant drop in strength occurs in the sixth decade of life, particularly after age 70. This decrease may be more pronounced in women. The average strength loss due to aging for individuals in their seventh and eighth decades is around 20% to 40%, and in some cases, even greater losses (50% or more) have been reported for those in their ninth decade and beyond. One study found that the knee-extensor strength of healthy 80-year-old individuals was 30% lower than that of 70-year-olds. Furthermore, it’s been demonstrated that muscle strength declines by approximately 15% per decade in the sixth and seventh decades and about 30% thereafter.

The decline in strength appears to be more problematic for women as they pass the age of 60. This may be due to the lower starting point for muscle tissue mass in women compared to men. While there are conflicting reports concerning the magnitude of strength loss with age, much of it stems from the use of cross-sectional and longitudinal data. Cross-sectional studies tend to underestimate strength loss, and longitudinal studies reveal more significant losses.

Long-term engagement in strength training can offset the magnitude of strength loss, but declines may still occur even in competitive weightlifters. Interestingly, the aging curve for fitness parameters among “master athletes” indicates that maintaining training throughout life can lead to better strength and power performances than untrained individuals who are 10 to 20 years younger. The rate of decline in peak oxygen consumption with aging was not significantly different from that of sedentary individuals, suggesting that training is essential for maintaining higher physiological and functional abilities.

Despite variations by gender, sex, and individual muscles or muscle groups, it is evident that strength decreases with age. Women generally demonstrate slower rates of decline in elbow extensor and flexor strength, and the loss is more substantial in lower extremities than in upper extremities for both sexes. Strength loss will occur with age, but continued training can mitigate this decline and the extent of loss varies across muscle groups and genders.

Causes of Decreased Strength With Age

The reduction in muscle strength that occurs with age is attributed to various factors. One primary factor is the loss of motor units, even in healthy and active individuals. This loss of motor units is a significant contributor to the age-associated reductions in strength. Moreover, there may be a loss of force per cross-sectional area as a result of unknown intrinsic factors in contractile proteins.

The impact of aging on muscle strength may also vary in different muscle groups. For example, for leg tasks, other factors beyond lean tissue are involved in the force production loss, while in arm flexors, the loss of lean tissue explains the functional decline in strength.

Several factors have been associated with age-related muscle weakness:

Natural Musculoskeletal Changes: Aging is accompanied by various natural musculoskeletal changes.
Accumulation of Chronic Diseases: Chronic diseases can accumulate over time, further affecting muscle function.
Medications: The use of medications to treat these diseases can also have an impact.
Disuse Atrophy: Lack of physical activity and muscle disuse can lead to muscle atrophy.
Undernourishment: Poor nutrition and undernourishment can weaken muscles.
Reductions in Hormonal Secretions: Changes in hormonal levels, including testosterone, can contribute to muscle loss.
Nervous System Changes: Aging can result in changes to the nervous system.
Changes in Bone Density: Osteoporosis and changes in bone density can affect muscle function.
Loss of Muscle Fibers: The loss of muscle fibers is a fundamental factor in muscle weakening.

Although it’s unclear whether older people can activate their muscles maximally (i.e., recruit all muscle fibers to their full capacity), evidence suggests that both older and young people can do so. However, it’s important to note that the activation of muscles for dynamic activities may differ from activation for isometric muscle actions.

Patterns of Muscular Power Loss With Age

The ability to produce force rapidly and relax quickly, referred to as muscular power, plays a vital role in functional abilities and is a major factor in injury prevention for older adults. Muscle power is essential for various everyday activities, including walking, climbing stairs, and lifting objects.

Studies have found that leg-extensor power in elderly individuals is significantly correlated with activities such as chair-rising speed, stair-climbing speed and power, and walking speed. The ability to produce force rapidly is also crucial for preventing injuries from falls, which are a significant public health concern among seniors.

Muscle power has been identified as a key indicator of functional ability and disability in seniors. Power production, especially in explosive movements, diminishes significantly with age, more so than maximal strength. Research has estimated that lower-limb power capabilities may decline at a rate of 3.5% per year from the age of 65 to 84.

Cross-sectional data indicate a loss of maximal voluntary contraction and speed of contraction in women by the age of 40, while speed of relaxation decreases by the age of 50. This reduced ability to produce rapid force early in the force-time curve has been observed in older women. Peak anaerobic power in master endurance and power athletes decreases linearly with age, meaning that a 75-year-old individual may have only 50% of the anaerobic power of a 20-year-old.

Given the importance of power capabilities for health and functional abilities, improving muscular power should be a primary training goal for older populations.

Causes of Decreased Power With Age

Much like the age-related loss of strength, the reduction in muscular power in older adults can be attributed to several factors. These include muscle atrophy, loss of muscle mass, the decline of type II muscle fibers, and decreases in the rate of voluntary muscle activation. However, the loss of muscle power can also be influenced by factors related to the quality of muscle.

One critical factor impacting the decline in muscle power is the reduction in contraction speed of actin and myosin, the contractile proteins in muscle cells. Research has shown that this contraction speed can decrease by up to 25% in older adults. Myosin heavy chains (MHC), which play a crucial role in muscle contraction, shift to slower types as people age. This shift can affect the speed of myosin and actin cross-bridge cycling during muscle actions. Interestingly, engaging in weight training can help mitigate some of these changes, as seniors undergoing resistance training exhibit a similar transformation in MHC as younger individuals do with training.

The loss of type II muscle fibers, which are known for their fast-twitch properties, further contributes to the decline in muscle power with age. These fibers contain fast MHC proteins that enable rapid force generation. With aging, the quantity and quality of these proteins are diminished.

Additionally, a decrease in myosin ATPase activity, which is essential for muscle contraction, occurs with aging. This enzyme’s reduced activity negatively impacts the ability to generate rapid force during muscle actions.

Another factor influencing the loss of muscle power may involve changes in the elastic properties of connective tissue. Research by Bosco and Komi in 1980 found that there was a decrease in countermovement vertical jump heights with increasing age. The performance of depth jumps, which involve a stretch-shortening cycle, resulted in even greater reductions in vertical jump ability with aging. This suggests that the effects of aging on the elastic and contractile components of muscle, including non-contractile proteins and connective tissue, lead to a decrease in inherent power.

Resistance Training Adaptations in Seniors

Resistance training holds great promise for seniors as a means to counteract the age-related decline in muscle mass and strength, commonly known as sarcopenia. While there is often a tendency to approach resistance training for seniors with caution, assuming they are frail or weak, evidence suggests that seniors can make remarkable gains in strength and muscle size. This section explores the adaptations that occur in seniors who engage in resistance training.

One key misconception to dispel is that older adults cannot achieve substantial strength gains. In fact, masters-level male and female powerlifters over the age of 65 have demonstrated impressive lifting capabilities, with some lifting well over 300 pounds in squats and 250 pounds in bench presses. These seasoned lifters underscore that seniors can indeed maintain significant strength with appropriate training.

Studies conducted on very old individuals, both men and women aged 87-96 years, who engaged in resistance training for eight weeks showed that training adaptations are preserved even in extremely old age. These adaptations included a 17% increase in leg press strength and a significant reduction in falls among older women. Notably, muscle size increased as determined by CAT scans.

Substantial strength gains and muscle hypertrophy were observed in sedentary older men (60-72 years) who underwent a 12-week high-intensity resistance training regimen. This regimen included three sets of eight repetitions at 80% of their one-repetition maximum (1RM) three days per week.

Similarly, a study involving 49- to 74-year-old women following a 21-week resistance training program, with six to eight exercises in each biweekly session, showed increased strength and hypertrophy.

While there is a distinction between young and older individuals at the beginning of a resistance training program, both men and women, irrespective of age, exhibited increases in type II muscle fibers with heavy resistance training. The extent of muscle fiber size increase can vary, but it is achievable for seniors through proper training.

An examination of muscle fiber types in seniors showed that they could increase the size of both type I and type II muscle fibers with resistance training, and even the percentage of type IIx fibers reduced, transitioning to type IIa fibers due to repeated recruitment during heavy resistance training.

The myosin heavy chain composition in seniors undergoing resistance training reflects the same transitional change as observed in younger individuals. This change is partly due to more dynamic physiological systems in younger individuals.

Moreover, resistance training is beneficial for seniors even if they are over 70 years old. Six months of resistance exercise (three days per week) resulted in strength increases in the leg press, bench press, and bench pull, along with a 6% increase in maximal workload.

While some studies show that very old individuals can maintain type I muscle fiber size and composition as a compensatory response to age-related loss of motor units, resistance training has been shown to lead to the hypertrophy of both type I and type II muscle fibers in seniors. This hypertrophy depends on the intensity and volume of the resistance exercise protocols used in the training program.

Some studies examining long-term adaptations to resistance training in seniors have found that strength continually improves over the course of a year of training, with no evidence of plateauing. The rate of strength gains may reduce over time, but there is no clear evidence that older individuals cannot achieve substantial and consistent improvements in strength over extended periods.

Power and Training in Seniors

Resistance exercise is an effective means to develop muscular power in seniors, and it is recommended as a low-cost intervention to reduce fall risk among the elderly. Power training, focusing on the velocity component of the power equation, is particularly beneficial for both elderly men and women. Furthermore, it is safe and well-tolerated by seniors.

Studies have shown that high-velocity resistance training significantly improves muscle power in the elderly. For instance, a program with a mean participant age of 77 years, emphasizing leg press exercise with a relatively high percentage of body mass (60-70%), led to substantial increases in muscle power. These improvements were accompanied by enhanced walking ability, though the effects on chair rise time and balance were smaller and non-significant, highlighting that the success of a training program can vary depending on the specific movements it involves.

While some studies have shown that power can increase with resistance training, the relationship between training loads and power outcomes can be complex. For example, a twelve-week training program at 80% of one-repetition maximum (1RM) with two sets of eight repetitions and a third set to volitional fatigue resulted in power increases but not necessarily specific to the 80% of 1RM resistance used in training. Knee extension power significantly increased at 20%, 40%, and 60% of 1RM but not at 80% of 1RM. Similar trends were observed in other studies.

However, there’s evidence that power improvements in older individuals can be achieved through proper training. Studies have shown that older adults improved their power over a 16-week training period due to improvements in both strength and concentric velocity. This differs from younger individuals who improved power primarily due to increased strength alone.

The effectiveness of power development in seniors may depend on the duration and type of resistance training program employed. Some studies suggest that older men, despite similar percentage changes in thigh cross-sectional area and strength as younger men, might not see significant improvements in power.

A key distinction is made between power training (emphasizing velocity) and strength training (emphasizing maximal force). Power training, with its high-velocity, low-intensity movements over time, may be more beneficial in enhancing physical function in older individuals. The specificity of training in power exercises may help optimize functional abilities, benefit the neuromuscular system, and even impact other physiological systems such as connective tissue.

Neural Adaptations and Protein Synthesis in Seniors

In the context of resistance training and its impact on seniors, both neural adaptations and protein synthesis play crucial roles in mediating strength and muscle changes. Neural adaptations, particularly the size principle of motor unit recruitment, are maintained even in the elderly. This principle suggests that motor units are recruited in an orderly fashion, from smaller to larger units, depending on the required force. Neural adaptations significantly contribute to improvements in strength in the initial weeks of resistance training.

For instance, frail older individuals who participated in high-intensity resistance training programs (e.g., 80% of one-repetition maximum) for ten weeks saw substantial increases in strength without significant muscle size gains. These improvements in strength were linked to enhanced gait speed, stair-climbing power, balance, and overall spontaneous activity. This suggests that short-term training may lead to strength gains, but longer durations might be needed to induce muscle hypertrophy in seniors.

Classic studies with older men have shown that resistance training programs emphasizing intensity and volume could enhance strength without necessarily increasing muscle size. For example, a study involving 72-year-old men found that training with two sets of ten repetitions at 66% of one-repetition maximum for elbow flexors increased strength but not muscle size. Longer training periods may be necessary to stimulate muscle hypertrophy in seniors. More research is required to understand the roles of intensity, volume, and training duration for different age groups of seniors.

Matching for activity levels and using the same relative intensity in resistance training for ten weeks resulted in increased muscle size and strength in both younger and older men. However, the isometric rate of force production did not change in older men, indicating potential challenges in developing power with short-term training. These findings suggest that neural factors play a significant role in the early phases of strength improvements in both middle-aged and older adults.

Another aspect of resistance training in seniors is its impact on protein synthesis and metabolism. Research in this area is ongoing, focusing on the effects of training and protein intake. Studies have shown that resistance training can increase nitrogen retention and the rate of whole-body protein synthesis in older adults. One study compared older and younger individuals and found that the older group had a lower rate of muscle protein synthesis. However, resistance training led to a significant increase in muscle protein synthesis in both younger and older participants.

In conclusion, neural adaptations are key mechanisms mediating strength gains in the early stages of resistance training for seniors. Protein synthesis also plays a role, and resistance training has been shown to increase nitrogen retention and the rate of whole-body protein synthesis. These findings underscore the importance of tailored resistance training programs for seniors, considering factors like intensity, volume, and duration, to optimize strength, muscle size, and overall physical function in aging individuals.

Muscle Damage and Resistance Training in Seniors

Muscle damage and subsequent repair and remodeling are integral aspects of the process of rebuilding skeletal muscle tissue. Resistance training is known to induce muscle damage, and understanding the extent of this damage in older individuals compared to younger ones is crucial to tailor effective training programs for seniors.

One study involved both young (20-30 years) and older (65-75 years) men in a pneumatic knee extensor training program conducted three days a week for nine weeks. This program consisted of five sets of knee extensor exercises, ranging from 5 to 20 repetitions, with each repetition requiring maximal effort. Biopsies were obtained from both the trained and control limbs to assess muscle damage using electron microscopy. The results revealed that strength increased in both age groups in the trained limb by approximately 27%. Prior to training, muscle analysis showed that both younger and older men had no more than 3% damage to muscle fibers. After training, this damage doubled to around 6-7% in the trained thighs of both age groups. Remarkably, there were no significant differences in the extent of myofibrillar damage between the younger and older men. However, a follow-up study involving women found that older women exhibited higher levels of muscle damage than younger women using a similar approach.

Markers of oxidative damage to DNA in both men and women showed significantly greater oxidative damage in the older individuals following an eccentric exercise bout. Interestingly, older men displayed higher levels of oxidative damage than older women. In older women, resistance training appeared to offer a protective mechanism against muscle damage during eccentric exercise, with post-training muscle damage showing no significant difference when compared to younger untrained women.

Furthermore, a six-month study showed that resistance exercise, with intensities ranging from 50% to 80% of one-repetition maximum (1RM), reduced exercise-induced oxidative stress and homocysteine concentrations in overweight and obese older adults.

Developing a Resistance Training Program for Seniors

Designing a resistance training program for seniors involves applying the same fundamental principles as for any age group. However, due to variations in the functional capacity and medical concerns of older individuals, the best programs are those that are individualized to meet their specific needs. Periodized training has been used with older adults in some cases, but simple and effective programs can yield positive results, especially in the early phases of training.

When the goal for older adults is to progress towards higher levels of muscular strength and hypertrophy, evidence supports the use of variation in the resistance training program. It’s crucial to introduce progression gradually to prevent acute injury and allow sufficient adaptation time. Additionally, programs should consider medical aspects such as cardiovascular problems and arthritis. Some older individuals may require a period of basic conditioning before engaging in more intense training.

Prior to prescribing exercises, evaluating an older person’s strength, body composition, functional ability (e.g., the ability to lift or get out of a chair), muscle size, nutrition, and pre-existing medical conditions is essential. The American College of Sports Medicine (ASCM) recommends consulting a physician before starting strength training for those in category III. Strength testing using as much as 75% of one-repetition maximum (1RM) has been shown to result in fewer cardiopulmonary symptoms than graded treadmill exercise tests in cardiac patients with good left ventricular function.

1RM testing is considered safe and effective for evaluating older adults, provided they are familiar with the protocol. The risk of injury during resistance training in seniors is generally low, with the greatest risk during testing, especially when exceeding 80% of 1RM. In some cases, submaximal testing can be used in seniors to predict their 1RM for training monitoring purposes.

A note of caution when conducting strength tests and interpreting study results is that older individuals may require more familiarization sessions with maximal strength testing to gain accurate information. Without adequate familiarization, some of the significant percentage strength gains in older individuals may be attributed to learning how to perform the exercise with heavier loads.

Proper exercise technique is critical for the safe implementation of a resistance training program. While some believe that machines are safer than free weights, it’s essential to emphasize proper technique for both types of equipment. With machines, individuals may push longer and strain harder during repetitions, even when technique fails, which can lead to muscle strains or pulls. However, free weight exercises, which require balance and control in multiple planes of motion, naturally prevent the continuation of an exercise if improper technique is used, thus minimizing potential issues. Technique training and supervision are essential components of a resistance training program for seniors, regardless of whether machines or free weights are utilized, as they help ensure safety and effectiveness.

Needs Analysis for Resistance Training in Seniors

Designing a resistance training program for older adults involves several important considerations:

Individualized Approach: People respond differently to resistance training based on their current training status, past experience, and response to training stress. To create an effective program, a needs analysis is crucial. This process involves pretesting, setting personalized goals, program design, and developing evaluation methods. Competent supervision is essential to optimize strength and conditioning programs, and certifications like the National Strength and Conditioning Association’s (NSCA) Certified Strength and Conditioning Specialist (CSCS) are valuable for trainers working with seniors. It’s essential to recognize that resistance training should be part of a lifelong fitness lifestyle for older adults, necessitating continual reevaluations of program goals and designs.
Risk Classification: The American College of Sports Medicine (ACSM) classifies people starting an exercise program into three risk categories: apparently healthy with fewer than one coronary risk factor, at higher risk with more than two coronary risk factors or disease symptoms, and previously diagnosed with diseases like cardiovascular, pulmonary, or metabolic conditions. Consultation with a medical professional and diagnostic exercise testing may be needed based on individual risk levels and clinical guidelines. Careful attention to exercise prescription elements such as warming up, cooling down, gradual progression of exercise volume and intensity, and proper training technique is important for reducing musculoskeletal and cardiovascular disease risks during exercise.
Frequency: Proper progression to avoid injury or acute overuse is a major concern for older adults. Their muscles may require longer recovery periods between exercise sessions, so it’s crucial to vary the intensity and volume to ensure recovery, especially after workouts that cause significant muscle damage. Resistance training two to three days a week is generally recommended, but three days a week offers more options for program design. Research has suggested that two weekly sessions may be as efficient as three for older individuals. For optimal results, it’s advised to include at least one session of high resistance (e.g., 80% of 1RM) each week.
Choice of Exercise: The selection of exercises should focus on major muscle groups and include compound, large-muscle-group exercises like squats, deadlifts, bench presses, and seated rows. These exercises help activate a significant portion of the skeletal muscle mass for adaptation. Upper-body exercises that stimulate muscles attached to primary bone sites of concern (e.g., spinal bone density) should also be included. While heavy weight may not be suitable for twisting and turning movements, exercises that incorporate these motions can improve functional abilities. It’s important to use exercise equipment that fits the individual’s functional capacity, and mobility training may be necessary for those with limited range of motion.
Functional Resistance Training: Functional resistance training mimics everyday functional activities and can help improve seniors’ ability to perform activities of daily living. Exercises like stair climbing, carrying groceries, and squat movements can enhance independence and functional abilities. Balance training is effective for reducing falls in older adults, but it should involve dynamic balance tasks like step-ups, walking lunges, and unstable surface exercises, as these have more functional carryover.
Balancing Challenges: Traditional balance training is less effective for seniors, especially in preventing slips and trips, which are common causes of falls. Perturbation-based training, where seniors experience gentle pushes or disturbances while engaging in balance exercises, can be more beneficial. Seniors can also benefit from resistance exercises that focus on stability and balance. Functional resistance training is an essential component of a broader resistance exercise practice, not a replacement for it.

Creating a resistance training program for older adults that takes into account these considerations can help improve strength, functional abilities, and overall health while minimizing the risk of injury. Properly tailored programs can enhance the quality of life for seniors as they age.

Order of Exercise, Resistance (Load), and Repetitions in Seniors’ Resistance Training

Resistance training programs for seniors should follow general principles when it comes to the order of exercise, resistance (load), and repetitions, but there are specific considerations for this population.

Order of Exercise:

The order of exercises for seniors is generally the same as for any age group. After a warm-up, large-muscle-group exercises typically come at the beginning of the workout. This arrangement minimizes fatigue, allowing participants to use higher intensities or greater resistances in these exercises.
Prioritizing the optimal stimulation of large muscle groups in the lower and upper body is crucial. Exercises like leg presses, bench presses, and seated rows are top priorities in senior exercise programs.
Large-muscle-group exercises are followed by smaller-muscle-group exercises and cool-down activities. In total-body workouts, exercises can be alternated between the upper and lower body, as well as between opposing muscle groups.

Resistance (Load):

The most common percentage range examined for resistance training in seniors is 50 to 85% of their one-repetition maximum (1RM) or a 6- to 12RM zone. Heavier loads in the 12RM or higher range have been used in the most effective investigations.
Lighter resistances (e.g., 30% and heavier) are recommended for high-velocity power movements.
The starting level of strength fitness in frail elderly individuals may be minimal, with a maximal force capability of only a few pounds (~1.3 kg).
It’s essential for trainers and program designers to use equipment that allows for small increments of resistance.
While lower-intensity resistance exercises are safe and beneficial for seniors, it’s important to note that the risk of injury is greater when using loads above 80% of 1RM, particularly in exercises above this intensity level.
Loads closer to 80% are crucial for optimizing training adaptations, including bone adaptation.
Using light elastic cords or hand weights may not achieve the same magnitude of adaptation as free weights, especially in older adults.

Repetitions:

Fewer repetitions are generally performed with heavier loads.
Improvements in local muscular endurance are important for seniors and can enhance their ability to perform submaximal work and recreational activities.
Caution is necessary when employing high-repetition, low-load programs, as excessive repetition volume with lighter resistances or inadequate rest between sets and exercises can lead to problems.
Sets should end when there is a break in proper exercise technique.
Safety considerations are crucial for seniors, given the prevalence of cardiovascular problems. Performing sets to concentric failure may lead to higher blood pressure and heart rates, particularly in the 70 to 90% of 1RM range. Seniors, especially those with cardiovascular issues, should avoid sets to concentric failure, especially when beginning a program. The performance of a Valsalva maneuver (suppressing one’s breath), typical in sets to failure, should also be discouraged in this population.

Lifting Velocity, Number of Sets, and Rest Between Sets and Exercises in Senior Resistance Training

In designing resistance training programs for seniors, several factors need to be considered, including lifting velocity, the number of sets, and the rest periods between sets and exercises.

Lifting Velocity:

For strength and hypertrophy training, moderate, volitional lifting velocities are recommended. This means that exercises should be performed with controlled and deliberate movements.
Power training, which focuses on increasing the rate of force development and explosive movements, requires light loads and faster lifting velocities.
Proper equipment, such as pneumatic resistance machines, and specific exercises, like Olympic-style movements or plyometric medicine ball exercises, are essential for power development.

Number of Sets:

The recommended minimal starting point for sets in senior resistance training consists of at least one set per exercise. However, progression can occur over time.
Seniors can gradually progress from one to three sets per exercise, depending on the number of exercises in their routine.
It’s important to note that even frail elderly individuals can tolerate three sets, so this is a reasonable goal to work towards.
The number of sets is closely related to exercise volume. Initially, some seniors may tolerate only a low exercise volume, making single-set programs a simple starting point.
The principle of progressive resistance training allows for an increase in exercise volume by adding sets or repetitions per set, helping individuals adapt to a higher workload.
Typically, programs for older adults don’t involve more than three sets per exercise. If more stimulation is needed for a muscle group, another exercise targeting that group can be added to the program.
Many programs also include a warm-up set with much lighter resistance than the working sets. This warm-up allows participants to get accustomed to the exercise movement and detect any unusual sensations, such as joint or muscle pain, before engaging with heavier training resistance.

Rest Between Sets and Exercises:

The rest periods between sets and exercises have a significant impact on the metabolic intensity of a resistance training session.
Older individuals generally have lower tolerance for anaerobic acidic conditions compared to younger individuals.
Typically, rest periods of 2-3 minutes between sets and exercises can be used in resistance training programs for seniors.
Continuous monitoring for any symptoms of discomfort, such as nausea or dizziness, is essential, and the program should be adjusted if symptoms occur. Tolerance of the workout is a priority for optimizing training outcomes.
Short rest intervals are sometimes used to enhance local muscular endurance and improve acid-base balance. However, caution is needed to prevent overexertion, especially in older adults.
The length of rest periods should align with program goals, resistance levels, and exercise tolerance. Shorter rest periods are suitable for circuit-style programs, while heavier resistances may require longer rest intervals.
The specific medical or physical conditions of an individual may also dictate the rest period length. For those with specific goals, such as strength gains, rest duration should be carefully controlled to avoid excessive metabolic stress.
Ultimately, the key to an effective program design is the individual’s tolerance of the workout, taking into account the progression toward specific fitness goals. Rest period length is a crucial element in achieving this goal.