The capacity of older men and women to adapt to regularly performed exercise has been demonstrated by many laboratories. Aerobic exercise results in improvements in functional capacity and reduced risk of developing type II diabetes in the elderly. High-intensity resistance training (above 60% of the 1 repetition maximum) has been demonstrated to cause large increases in strength in the elderly. In addition, resistance training results in significant increases in muscle size in elderly men and women. Resistance training has also been shown to significantly increase energy requirements and insulin action of the elderly. We have recently demonstrated that resistance training has a positive effect on multiple risk factors for osteoporotic fractures in previously sedentary post-menopausal women. Since the sedentary lifestyle of a long-term care facility may exacerbate losses of muscle function, we have applied this same training program to frail, institutionalized elderly men and women. In a population of 100 nursing home residents, a randomly assigned high-intensity strength training program resulted in significant gains in strength and functional status. In addition, spontaneous activity, measured by activity monitors, increased significantly in those participating in the exercise program, while there was no change in the sedentary control group. The fact that significant muscle hypertrophy was seen in this population indicates that age does not decrease the capacity to adapt to a progressive resistance training program. Therefore, exercise may minimize or reverse the syndrome of physical frailty which is so prevalent among the oldest old.(ABSTRACT TRUNCATED AT 250 WORDS)