Endurance, Strength, Power
In resistance training, three aspects of muscle performance to consider are muscular endurance, muscular strength, and muscular power. While all these are important, you might consider the relative importance of each of these as we age – and to consider which of these we are losing more rapidly as we age.
When working with older adults, often fitness trainers encourage their clients to perform exercise in a way designed to increase muscular endurance (lower resistance with higher repetitions performed relatively slowly), the (mistaken) idea being that lifting heavier weights will lead to injury in older adults. But this may not be the best approach in terms of maintaining independent functioning.
First some definitions. . .
Muscular endurance: the ability to sustain repeated contractions against a resistance. In short, you can perform many repetitions of an exercises, such as 25 bicep curls.
Muscular strength: ability to develop a maximal force against a resistance in a single contraction. Muscular strength is measured through a test called the one-repetition maximum. Muscular strength is trained for by performing exercises with a resistance heavy enough that you can perform only 6-8 repetitions of the exercise before reaching fatigue/failure.
Muscular power: the ability to exert maximal force in as short a time as possible. Muscular power is the skill required in acceleration (think of coming out of the blocks at the start of a race), jumping, throwing, a golf swing, or a pickleball stroke. It is also the skill we need to propel ourselves up out of a chair. Exercises to develop muscular power use relatively light resistance (30% to 50% of the maximum that could be lifted), but with exercises performed quickly.
Although each of these muscular qualities declines with aging, muscular power declines earlier and more rapidly. But it is also muscular power that may be of the greatest importance in maintaining independent functioning and quality of life. Research has shown that muscle power is a more important factor than strength or endurance for performing tasks such as climbing stairs and rising from a chair (Reid and Fielding, 2012), skills that are essential for independent functioning.
Training each of these types of muscle qualities (endurance, strength, and power) requires a different type of training. All are important but be sure you are including some training for muscular power. Before beginning a resistance training program for muscular power, you should have a period of at least 4-6 weeks working on basic exercises to develop muscular strength and endurance.
If you are just starting out with a resistance training program, it is a good idea to consult with a qualified fitness professional who can evaluate your current muscular skills and design a safe, effective program to meet your needs.
Reid, K. F., & Fielding, R. A. (2012). Skeletal muscle power: a critical determinant of physical functioning in older adults. Exercise and Sport Sciences Reviews, 40(1), 4-12.