For example, in the Westcott and Guy (1996) study, the 341 older adults added 2.4 pounds of muscle and lost 4.1 pounds of fat after two months of single-set strength training. Perhaps more important, 95 percent of the participants continued to strength train after completion of the exercise program. Of course, as the senior exercisers become better conditioned, they may perform additional training sets if they desire to do so.

Training Resistance
There is a range of training weightloads, generally between 60 to 90 percent of maximum resistance, that is productive for developing muscle size and strength. Weightloads below 60 percent of maximum are relatively light and provide less muscle building stimulus. Conversely, weightloads above 90 percent of maximum are relatively heavy and may present more injury risk.

For most practical purposes, training with 70 to 80 percent of maximum resistance represents a safe and effective weightload range. In fact, many of the studies with senior subjects have successfully used 70 to 80 percent of maximum resistance in their training programs (Frontera et al 1988, Nelson et al 1994, Fiatarone et al 1994, Westcott and Guy 1996). As these studies have reported no training-related injuries and high rates of muscle development, exercise weightloads between 70 and 80 percent of maximum resistance are recommended for senior strength training programs.

Training Repetitions
Research (Westcott 1995) indicates that most people can perform about 8 repetitions with 80 percent of their maximum resistance, and about 12 repetitions with 70 percent of their maximum resistance. This represents a moderate number of repetitions per set, and requires about 50 to 70 seconds of continuous training effort when performed at a moderate movement speed. The recommended number of training repetitions for senior exercisers is therefore between 8 and 12 repetitions per set.

Training Progression
Although it is not problematic to train with more than 12 repetitions, the key to muscle development is progressive increases in the exercise resistance. Therefore, it is advisable to add a little weight whenever 12 repetitions can be completed in proper form. The recommended training approach is to work with a given resistance until 12 repetitions are performed, then to raise the weightload by five percent or less. For most senior exercisers, this corresponds to about 2.5 to 5.0 pounds more weight, which in turn reduces the number of repetitions that can be completed. This double-progressive training system gradually increases the exercise demands and reduces the risk of doing too much, too soon.

Training Speed
There is general consensus that older adults should use controlled movement speeds when performing strength exercise. One study (Westcott 1994) showed excellent and almost equal strength gains for subjects training with four-second, six-second, and eight-second repetitions, indicating that there is a range of effective training speeds. Because six-second repetitions have a long and successful history, this repetition speed is recommended for senior exercisers. The preferred cadence is two seconds for the more demanding lifting phase (concentric muscle action), and four seconds for the less demanding lowering phase (eccentric muscle action).

Training Range
Due to age-related decreases in muscle function and joint flexibility, it is important for seniors to develop strength throughout their full range of joint movement. Research has shown that full-range exercise movements are necessary for building full-range muscle strength (Jones et al 1988). That is, strength gains appear to be limited to the movement range that is trained. For best results, seniors should perform each strength exercise through the complete range of joint movement, working the muscles from their fully stretched position to their fully-contracted position. However, if any part of the exercise action causes discomfort, the movement range should be abbreviated accordingly.

Training Technique
In addition to controlled movement speed and full movement range, exercise technique is a critical training factor for older adults. Seniors should always practice proper posture when performing strength exercises, with particular emphasis on position stability and back support. To avoid unnecessary blood pressure elevation older adults should breathe continuously throughout every repetition. The preferred breathing pattern is to exhale during the more demanding lifting movement (concentric muscle action), and to inhale during the less demanding lowering movement (eccentric muscle action). Most important, senior strength trainers should never hold their breath (valsalva effect) or hold the resistance in a static position (isometric effect).

Summary There are many reasons that men and women over 50 years of age should perform regular strength training. These include physiological benefits for the muscular system, skeletal system, cardiovascular system, and digestive system.

However, the major advantage of strength exercise is to replace the muscle tissue that is lost at the rate of about one pound per year in older adults. Regular strength training has been shown to increase muscle mass by more than one pound per month and to increase resting metabolism by over two percent per month, thereby reversing some of the degenerative processes associated with aging.

Senior exercisers should follow general guidelines for safe, sensible, effective and efficient strength training programs. The basic recommendation for successful strength training experiences are: (1) including exercises for all of the major muscle groups; (2) training two or three non-consecutive days per week; (3) performing one set of each exercise; (4) using between 70 and 80 percent of maximum resistance; (5) performing between 8 and 12 repetitions per set; (6) adding five percent more resistance whenever 12 repetitions are completed; (7) using moderate movement speeds, such as six seconds per repetition; (8) exercising through the full range of joint movement; (9) practicing proper posture; and (10) breathing continuously throughout every exercise repetiton.

Research indicates that 95 percent of previously sedentary seniors who complete a well-designed, short-term strength training program continue to do strength exercise.

Wayne L. Westcott, Ph.D., is fitness research director at the South Shore YMCA and author of several books including, Building Strength and Stamina and Strength Training Past 50.

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