Isokinetic and isotonic measurements of knee extension and flexion, in that they involve translating a weight along an arc of motion within a given time interval, are measures of muscle power (although they are mostly reported as joint torques

in feet pounds or Newton meters) whereas isometric measurements involve purely the ability to generate force. Because these loading conditions are more relevant to human motion, most studies have reported results of isokinetic and isotonic exercise. Table 1 summarizes results of cross-sectional AZD4547 in vivo studies of lower-extremity muscle function [68–73]. In cross-sectional studies comparing young normal subjects in the 20–40-year age range to healthy elders in the 70–80-year age range, declines in knee

extensor torque and power have ranged from 20% to 40%, with RepSox greater losses in the 50% range reported for individuals in their 1990s [74–78]. Over the lifetime, men have inherently greater knee extensor power and torque than women, but on a percentage basis, age-related losses are similar between genders, with losses in men incurring greater absolute losses because they start with AZD5363 manufacturer higher baseline values. Compared to the abundance of cross-sectional studies, there are fewer longitudinal studies of knee extensor properties with aging. Hughes et al. examined a cohort of 52 elderly men and 68 women who had been examined 10 years earlier, finding similar declines in the knee extensors and flexors ranging from 12% to 18% per decade [79]. Longitudinal studies of smaller cohorts have shown variable results, with one study reporting losses of roughly 3% per year in 23 men aged 73–86 at baseline [80], and another study which reported no changes in strength of either men or women over an 8-year follow-up

[81]. Cross-sectional studies Resveratrol of isometric measurements of ankle plantar flexion have shown age-related declines similar to those measured for knee extension torque and power. Studies of age-related muscle strength in the upper extremities show essentially similar results to the lower extremities, with cross-sectional studies reporting declines of 20–40% in measures such as hand-grip strength and elbow extension torque between healthy younger subjects and elderly subjects and longitudinal studies showing yearly declines ranging from 1% to 5% [17]. Table 1 Age-related changes in muscle power and muscle strength Study Gender Measurement/joint/movement Age range (years) Study design Changes with aginga Dean et al. 2004 [73] F IK/hip/FLX, EXT 21–82 CS ↓22–33% Johnson et al. 2004 [72] F IK, IM/hip/AD, AB 21–91 CS ↓24–34% IK, ↓44–56% IM Kubo et al. 2007 [71] M IM/ankle/PF 20–77 CS ↓40% Morse et al. 2005 [70] M IM/ankle/PF 25.3 ± 3.5–73.8 ± 3.5 CS ↓47% Petrella et al.