Resistance and Repetitions
There is an inverse relationship between the amount of resistance used and the number of repetitions performed. The productive resistance range for strength development is generally considered 60 to 90 percent of maximum resistance, with a standard recommendation of approximately 75 percent of maximum resistance (2, 16). Research indicates that most adults can complete between 8 and 12 repetitions with 75 percent of their maximum resistance, and the majority of senior strength training studies have incorporated this exercise protocol (4, 7, 9, 13, 17, 18).
Although 8 to 12 repetitions with 75 percent of maximum resistance has proven to be a safe and productive strength training protocol for men and women between 50 and 90 years of age, the American College of Sports Medicine recommends that seniors perform 10 to 15 repetitions per set with slightly less resistance (1). This more conservative training approach is most appropriate for beginning exercisers. However, as higher levels of strength fitness are attained, most seniors can safely progress to lower repetition exercise protocols. The textbook, Strength Training for Seniors, recommends the following training progressions for seniors who prefer to use heavier resistance (16).
- Beginner Exercisers 12 to 16 repetitions with about 65 percent
of maximum resistance.
- Intermediate Exercisers 8 to 12 repetitions with about 75 percent of maximum resistance.
- Advanced Exercisers 4 to 8 repetitions with about 85 percent of
maximum resistance, periodically.
The key factor in strength development is progressive resistance. For continued progress, seniors must gradually increase the training load as the muscles become stronger. A safe approach to more challenging training sessions is known as the double progressive program, in which clients increase the number of repetitions before they increase the exercise resistance. For example, seniors following an 8 to 12 repetition protocol should use the same resistance until they can complete 12 good repetitions, at which point they should increase the resistance by 5 percent or less.
The two major factors in exercise technique are movement speed and movement range. Although research has not revealed an optimal speed for strength training, studies with senior subjects have incorporated relatively slow movement speeds, typically averaging about 6 seconds per repetition (13, 18). At about 6 seconds per repetition, a set of 10 repetitions requires approximately one-minute of continuous muscle action/tension, which provides a productive stimulus for strength development (16). Because slower movement speeds involve less momentum they provide more controlled and consistent stress to the musculoskeletal system, thereby reducing the risk of injury.
Seniors should develop strength throughout the full-range of every joint action, if they can do so without discomfort. Research indicates that full-range strength requires full-range repetitions, as strength gains are specific to the exercise movement patterns (11). Consequently, most strength exercises should be performed throughout the full-range of pain-free movement to maximize muscle development and maintain joint integrity.
Strength training is recommended on non-consecutive days, as the muscle microtrauma that results from resistance exercise generally requires about two recovery days for tissue remodeling and strength building (1). Research with more than 1,100 adults and seniors showed more muscle development from three-day-per-week training than from two -day-per-week training (18). However, the difference was relatively small (about 10%), indicating that twice-a-week strength training is highly effective.