The illness of being sedentary
Exercise,  Fitness tips

Seniors: The illness of being sedentaryThis article is a 7 min read

A senior who does not engage in regular resistance training experiences rapid losses in muscle quality, mass, and function. These losses are directly tied with chronic illness and problems of movement and balance. The losses of muscle mass are associated with a decrease in the production of myokines which have endocrine like effects on body organs and may play a role in exercise related protection against chronic illness (Jacobs, 2018; Tipton, 2009). Simultaneously, chronic disease in of itself creates a viscous cycle for the fitness of individuals. Minus the factors of normal aging, diseases such as heart failure, diabetes, obstructive lung disease, liver failure, cancer, and AIDS may all lead to a loss of function and subsequent sarcopenia (Jacobs, 2018).

The illness of being sedentary

Conversely even without these chronic conditions the “illness of being sedentary” has grave effects of the magnitude of the disorders themselves or possibly leading to some of them (Jacobs, 2018; McArdle, Katch, & Katch, 2015). Strength seems to peak between the ages of 20 to 30 (Fleck & Kraemer, 2014). After the age of 30, in the untrained individual, muscle mass is lost at a rate of about 3%-8% a decade (Jacobs, 2018). Following the age of 50 this rate of muscle attrition is greatly increased to 5%-10% a decade in people who do not resistance train (Jacobs, 2018). By the age of 60, people who do not resistance train, have lost about 1 pound of muscle for every year of life (Jacobs, 2018). The muscle loss is associated with a loss in bone tissue further compromising the musculoskeletal system (Fleck & Kraemer, 2014; Jacobs, 2018; McArdle, Katch, & Katch, 2015). Other factors that play into the aging adult is loss of flexibility, reduced function in the brain and nervous system which impact functional abilities.

Older adults experience strength and power loss

The current data on strength loss for older adults is clear, compared to their younger counterparts, older adults score significantly lower on many strength tests. For example, in the Copenhagen City Heart Study knee extensor strength for eighty-year-old men and women was 30% then a previous report in the same study evaluating 70-year-old men and women (Fleck & Kraemer, 2014). This indicates a large decline in one decade alone. There is a kaleidoscope of factors that play into age related strength loss some of which have been elucidated above. The most significant factor in the loss of strength may be loss of motor units. There has been a correlation of strength loss and muscle cross sectional area and reduction of muscle fibers in older adults and changes may be muscle group dependent (Fleck & Kraemer, 2014). Proper nutrition, or there lack of, may play a role in strength and power decreases (Fleck & Kraemer, 2014). As mentioned above chronic illness have an impact. Many chronic illnesses in the older adult lead to disuse atrophy and other changes that impact strength and power. The use of medications to treat some disorders can increase fatigue, interfere with nutrition, cause problems with movement and balance making the ability for the older adult to remain active even worse.

As one ages the ability to produce power decreases and this may be more important in regards to dynamic function than muscular strength (Fleck & Kraemer, 2014). It has been demonstrated that power is directly related to stair climbing, chair rising, gait speed, and balance in the older adult (Hazell, Kenno, & Jakobi, 2007). It seems that power begins to decrease after the age of 40 and it is estimated that a rate of 3.5% loss per year for the lower-limbs occurs between 65 and 85 years old (Fleck & Kraemer, 2014). Some of the factors related to strength loss are related to loss of power. This makes sense since the equation for power (Power = work / time) includes the ability to generate work (force x the distance) which includes a degree of strength (force). Given that, muscle atrophy, muscle mass loss, loss of type II muscle fibers, and a reduction in rate of voluntary activation play a role in power deficits (Fleck & Kraemer, 2014). It has been demonstrated that the contraction speed of actin and myosin is reduced up to 25% in older adults (Fleck & Kraemer, 2014). Myosin heavy chains move toward slower types with aging, and a subsequent loss of fast MHC proteins (Fleck & Kraemer, 2014). Additionally, the muscles connective tissue may see age related changes that reduce the ability to participate in power generation (Fleck & Kraemer, 2014).

Loss of strength and power impacts function

As one can see building adequate muscle mass, strength, and power well prior to the third decade in life is optimal for preventing much of the loss associated with aging. For the older adult, changes in muscle strength and power is significant when considering functional abilities and the capability to perform activities of daily living (Fleck & Kraemer, 2014). The ability to maintain a static posture requires the ability to interpret and respond to information to maintain center of gravity. Without an intact sensory network, the older adult is at a disadvantage in maintaining static posture as inputs are either absent or misinterpreted (Levangie & Norkin, 2015). If the individual’s ability to respond is also compromised the risk for falling is greatly increased. The adult whose musculoskeletal system is lacking adequate neural control, strength and probably most importantly, ability to act quickly with power is at risk for falling (Levangie & Norkin, 2015).

Whether maintaining a static posture is from synergies (muscles working together to resist changes in equilibrium) or strategies (stepping forward, backward, sideways, grasping to resist changes in equilibrium) it requires an intact neuromuscular system (Levangie & Norkin, 2015).  As muscle weakness increases deviations from optimal posture may occur. These deviations if maintained for long periods of time may cause alteration in muscle structure and lead to increased energy expenditure and fatigue and cause compensatory postures which will then need correction (Levangie & Norkin, 2015). Thus, for the older adult it may not simply be improving strength and power but also likely postural deviations. It should be noted though that it has been posited that with reduced bone mineral density, some falls may be due to a fracture rather then the fracture being caused by the fall (Jacobs, 2018). Consequently, bone health is a critical part of the clinical picture as many of the fractures occur with minor movements.

Reduced function and problems walking

Walking is complex. The gait cycle includes lower limb right and left stance, right and left swing, right single support, left single support, double support (Levangie & Norkin, 2015). Additionally, angle of foot strikes, stride length, duration, cadence, joint angles, ground reaction forces, etc. all play a role (Levangie & Norkin, 2015). A person’s walking movement also requires coordination of the upper body segments to maintain center of gravity (Levangie & Norkin, 2015). Finally, there are interindividual differences in preferred gait and how one generates speed. Means for walking in healthy older adults’ range between 5000 – 6000 step/day. The ability to walk is helpful in prevention of various chronic diseases. The capability of walking 400 meters in a period of time is related to mortality. Research has demonstrated that ankle plantar flexor power and dorsiflexor range of motion are important in maintaining gait in older adults (Levangie & Norkin, 2015). Other data suggest that hip flexor strength is correlated with gait speed (Levangie & Norkin, 2015). Finally, reduced efficiency in gait could be due to increased antagonist cocontraction (Levangie & Norkin, 2015). Programs emphasizing strength and conditioning of the kinetic chain (functional training) have shown promise in improving gait in older adults (Levangie & Norkin, 2015).

Regular resistance training in older men and women can improve muscle quality and strength.

With resistance training increases in type I and II fibers and increases in muscle cross sectional area have been observed (Fleck & Kraemer, 2014). Although strength improvements can occur at low intensity thresholds, there seems to be a “optimal” threshold for training benefits with use of multiple sets and higher intensity work at 70-80% of 1 RM and greater success with periodization (Fleck & Kraemer, 2014). However, each person should be evaluated and have an individualized exercise prescription written based on a needs analysis. Viewing the dynamics associated with static posture control and gait one can see how resistance training for both strength and power can play a role in helping the older adult remain independent and healthy.

References

Fleck, S. J., & Kraemer, W. J. (2014). Designing resistance training programs (4th ed.). Champaign, IL: Human Kinetics.

Hazell, T., Kenno, K., & Jakobi, J. (2007). Functional Benefit of Power Training for Older Adults. Journal of Aging and Physical Activity, 15(3), 349-359. doi:10.1123/japa.15.3.349

Jacobs, P. L. (2018). NSCA’s essentials of training special populations. Champaign, IL: Human Kinetics.

Levangie, P. K., & Norkin, C. C. (2015). Joint structure and function: A comprehensive analysis (5th ed.). Philadelphia, PA: F.A. Davis Company.

McArdle, W. D., Katch, F. I., & Katch, V. L. (2015). Exercise physiology: Nutrition, energy, and human performance (8th ed.). Philadelphia, PA: Wolters Kluwer Health/Lippincott Williams & Wilkins.

Tipton, C. M. (2009). ACSM’s advanced exercise physiology. Philadelphia, PA: Lippincott Williams & Wilkins.