Editorial: Exercise Strategies Should Be Designed to Increase Muscle Power

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Abstract
THE age-related decrease in muscle mass (referred to as “sarcopenia”) and strength has been well characterized. Indeed, sarcopenia has been demonstrated to be associated with decreased functional capacity among very old individuals and decreased energy needs. What is less well understood is the relationship between muscle size and strength and the development of power. Power is the product of force generation and speed of muscle contraction. Bassey and colleagues (1) demonstrated that among frail nursing home residents, leg muscle power is more important than strength for performing daily activities such as stair climbing, rising from a chair, and walking. Older men and women who required the use of assistive aids to perform these tasks had 42–54% less leg extensor power than those who could complete these tasks without assistance. The ability to generate force rapidly is a critical component of ambulation. Preservation of strength and prevention of sarcopenia, while important, may not result in a preservation of the ability to perform mobility-related activities of daily living. Indeed, muscle quality (defined as the amount of force production/unit of muscle) decreases with advancing age (2), and muscle power decreases to a greater extent than does muscle strength (3). Although sarcopenia has been demonstrated to be a predictor of disability in older people (4), the strongest predictor of late-life mobility-related disability appears to be body fatness (5)(6)(7). While a number of studies have indicated that low body weight or weight loss is associated with an increase in the risk of hip fracture (8)(9)(10), increased body weight and body fat has also recently been shown to increase the risk for a hip fracture in older White women (11). The explanation for this may be in the greatly reduced ability to generate power with increased amounts of body fat. Reduced muscle quality and decreased power production are also risk factors for hip fractures among older people (12). In addition, weight loss without resistance exercise will likely result in an exaggerated loss of muscle mass in older people.