The maintenance of adequate muscle strength and muscle power is vital as both have been associated with physical function in older adults,17, 23, 27, 28 and 29 although there is currently no consensus as to which has a stronger contribution to overall physical function.26 According to the Centers for Disease Control and Prevention, Proteasome inhibitor PA is defined as any bodily movement produced by skeletal muscle contractions that results in energy expenditure above an individual’s basal level. In contrast, exercise is defined as planned, structured,

or repetitive PA performed to either maintain or improve one or more components of physical fitness.30 Advancing age is associated with declines in PA,31 including total volume of PA,32, 33 and 34 intensity of PA,33, 35 and 36 and increases in sedentary time,35 which is particularly evident in older women.35 Furthermore, a recent cross-sectional study among older adults reported that individuals 70–80 years are less active than individuals 60–69 years in all domains, including leisure-time activity, work-related, Inhibitor Library price and housework.37 PA recommendations

for older adults include both aerobic exercise and resistance training. However, statistics indicate that only 51.1% and 21.9% of older adults meet the aerobic and resistance training guidelines, respectively.38 Moreover, a sex difference exists such that older men are more active than older women.39 In 2004, the percentage of women aged 18–24 years who reported no engaging in resistance training

was 20.1%. However, among older women, the percentage decreased considerably to only 10.7% (compared to 14.1% for older males).40 Globally, longitudinal studies report conflicting results in the PA trends of older adults. Some studies have reported increases41, 42 and 43 while others have reported declines in PA.44 and 45 In general, a review by Sun and colleagues39 found that among older adults, there tends to be a rise in leisure-time PA, yet most older adults do not engage in a sufficient volume of PA to promote health benefits.39 Despite Sun’s conclusions, the percent of older men and women engaging in resistance training in the United States increased significantly between 1998 and 2004 (11.0% to 14.1% for men and 6.8% to 10.7% for women).40 In summary, older adults (especially women) are not meeting the recommended PA guidelines, particularly as they relate to resistance training. Though not the focus of this review, profound changes in body composition (sarcopenia and increased adiposity) are also present during the aging process. In both older men and women, there tends to be an age-related increase in overall adiposity, which has been reported as a leading cause of disability.8 and 10 Moreover, there is a noticeable decline in skeletal muscle mass at ∼45 years of age in both sexes, although the age-associated decrease is greater in men compared to women.