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Skeletal muscle, which represents up to 40% of total body weight, influences a variety of metabolic risk factors, including obesity, dyslipidemia, type 2 diabetes, and cardiovascular disease ( 124). Muscle loss increases to 5% to 10% each decade after age 50 ( 95), averaging approximately 0.4 kg per year after the fifth decade of life ( 101). Muscle mass declines between 3% and 8% each decade after age 30 ( 46), averaging approximately 0.2 kg of lean weight loss per year ( 49,50). It is therefore likely that an even higher percentage of the older adult population has excess body fat (above 22% for males and above 32% for females) ( 4). These percentages are based on body mass index calculations that do not account for age-related sarcopenia ( 50).

WESTCOTT STUDY CENTER SERIES

The series of events that seem to be associated with a large number of illnesses, injuries, and infirmities are 1) muscle loss, 2) leading to metabolic rate reduction, 3) followed by fat gain that places almost 80% of men and 70% of women 60 years of age and older in the undesirable categories of overweight or obese ( 47). Given the serious problem of sarcopenia in an increasingly sedentary and aging population ( 71), and the accumulating evidence that resistance exercise promotes muscle gains in men and women of all ages ( 144), it is understandable that leading researchers have advocated a public health mandate for sensible resistance training ( 109).

More recently, attention has been given to age-related muscle loss ( 68,95) and associated physiological problems such as bone loss ( 101), metabolic decline ( 142), fat gain ( 124), diabetes ( 46), metabolic syndrome ( 125), and all-cause mortality ( 45). However, the overwhelming emphasis was on aerobic activity with little encouragement for resistance training ( 29). Average individuals saw no reason to engage in weight training, and participants in other sports typically felt that lifting weights actually would hinder their athletic performance.ДЄs American lifestyle became more sedentary and heart disease became the leading cause of death, regular exercise was promoted for attaining physical fitness, desirable body weight, and cardiorespiratory health. It was obvious that these athletes required high levels of strength and muscularity to excel in their chosen sport and that their mesomorphic physiques responded favorably to heavy resistance training with barbells and dumbbells. Not long ago, the muscle-building activity known as weight training generally was considered to be the domain of exceptionally strong men who competed in sports such as powerlifting, Olympic lifting, bodybuilding, and football. Resistance training may be effective for reducing low back pain and easing discomfort associated with arthritis and fibromyalgia and has been shown to reverse specific aging factors in skeletal muscle.

Resistance training may promote bone development, with studies showing 1% to 3% increase in bone mineral density. Resistance training may enhance cardiovascular health, by reducing resting blood pressure, decreasing low-density lipoprotein cholesterol and triglycerides, and increasing high-density lipoprotein cholesterol. Resistance training may assist prevention and management of type 2 diabetes by decreasing visceral fat, reducing HbA 1c, increasing the density of glucose transporter type 4, and improving insulin sensitivity. Benefits of resistance training include improved physical performance, movement control, walking speed, functional independence, cognitive abilities, and self-esteem. Ten weeks of resistance training may increase lean weight by 1.4 kg, increase resting metabolic rate by 7%, and reduce fat weight by 1.8 kg.

Inactive adults experience a 3% to 8% loss of muscle mass per decade, accompanied by resting metabolic rate reduction and fat accumulation.

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