Twenty-four men and 26 women (25 +/- 5 years) participating in 10 weeks (n = 27) and 18 weeks (n = 23) of variable resistance strength training programs were recruited to complete 12 weeks of reduced training. Training consisted of one set of 7-10 bilateral knee extensions performed to volitional failure. Prior to the reduced training phase of the project, the subjects were training either 2 days.week-1 (n = 23) or 3 days.week-1 (n = 18). The subjects who trained 3 days.week-1 reduced training frequency to 2 days.week-1 (n = 9), 1 day.week-1 (n = 7), or 0 days.week-1 (n = 2). The subjects who trained 2 days.week-1 reduced training frequency to 1 day.week-1 (n = 12) or 0 days.week-1 (n = 11). Nine subjects served as controls and did not train. Isometric knee extension strength was assessed at 9, 20, 35, 50, 65, 80, 95, and 110 degrees of knee flexion on two separate occasions prior to and immediately post-training and following reduced training. After training, mean relative increases in peak isometric knee extension strength and dynamic training weight were 21.4% +/- 17.5% (P less than or equal to 0.01) and 49.5% +/- 14.7% (P less than or equal to 0.01), respectively. The subjects who stopped training (0 days.week-1) lost 68% (P less than or equal to 0.01) of the isometric strength gained during training.(ABSTRACT TRUNCATED AT 250 WORDS)

in younger adults (Kohrt et al. 1991). The interrelationships of age, \i02max, and training status are evident when the loss inVO,max with age is compared for active and sedentary individuals (Figure 3-5). When the cardiorespiratory responses of an older adult are coinpared with those of a young or middle-aged adult at the same absolute submaximal rate of work, stroke volume for an older person is generally lower and heart rate is higher from the attempt to maintain cardiac output. Because this attempt is generally insufficient, the A-+0, difference must increase to provide the same submaximal oxygen uptake (Raven and Mitchell 1980; Thompson and Dorsey 1986). Some researchers have shown, however , that cardiac output can be maintained at both submaximal and maximal rates of work through a higher stroke volume in older adults (Rodeheffer et al. 1984). The deterioration in physiological function normally associated with aging is, in fact, caused by a combination of reduced physical activity and the aging process itself. By maintaining an active lifestyle, or by increasing levels of physical activity if previously sedentary, older persons can maintain relatively high levels of cardiovascular and metabolic function, including irO,max (Kohrt et al. 199 1)) and of skeletal muscle function (Rogers and Evans 1993). For example, Fiatarone and colleagues (1994) found an increase of 113 percent in the strength of elderly men and women (mean age of 87.1 years) following a lo-week training program of progressive resistance exercise. Cross-sectional thigh muscle area was increased, as was stair-climbing power, gait velocity, and level of spontaneous activity. Increasing endurance and strength in the elderly contributes to their ability to live independently. Differences by Sex For the most part, women and men who participate in exercise training have similar responses in car-diovascular, respiratory, and metabolic function (providing that size and activity level are normal-iced). Relative increases in\jO,max are equivalent Figure 3-5. Changes in 00, max with aging, comparing an active population and sedentary population (the figure also illustrates the expected increase in VO, max when a previously sedentary person begins an exercise program) A-Active adults R&&on in activity plus weight gain Sedentary adults Physiologic Responses and Long-Term Adaptations to Exercise for women and men (Kohrt et al. 1991; Mitchell et al. 1992). Some evidence suggests that older women accomplish this increase inVO,max mainly through an increase in the AGO, difference, whereas younger women and men have substantial increases in stroke volume, which …