Muscular Strength Testing

Many studies have shown that maintaining or increasing muscular strength and endurance throughout the lifespan is important for preventing disease, maintaining health and preserving the ability to perform normal life activities.

Muscular strength is defined as the maximal force that can be generated by a specific muscle or muscle group during a single movement (ACSM 2005b; Heyward 2002; Howley & Franks 2003). The force generated is specific to the muscles involved, as well as the type (e.g., isometric or isotonic, concentric or eccentric), speed and joint angle of the contraction (ACSM 2005b). The muscular strength test results are usually expressed in terms of the amount of weight lifted during the test. The muscular strength test that will be discussed in this section is the one-repetition maximum (1RM). Other strength tests include handgrip dynamometer (isometric) and isokinetic testing.

1RM Testing. The 1RM is the heaviest weight that can be lifted one time while maintaining good form. This type of maximal strength testing is considered the gold standard for evaluating dynamic strength (ACSM 2005b). Because this type of testing involves the use of isotonic or dynamic muscular contractions, it translates well to real-life situations, as well as exercise performance.

Any exercise can be used to determine a 1RM. The procedures are as follows (ACSM 2005b; Heyward 2002; Howley & Franks 2003):

1. After a period of familiarization with the movement, have the client perform a light warm-up of 5–10 reps at 40%– 60% of his or her perceived maximum resistance (light to moderate exertion).

2. After a 1-minute (min) rest with light stretching, cue the client to perform 3–5 reps at 60%–80% of perceived maximum resistance (moderate to heavy exertion).

3. Add 5–10 pounds (lb). If the client is successful at lifting that weight, allow a rest period of 3–5 min and add another 5–10 lb. Continue this process until a failed attempt occurs. Record the last successfully completed lift as the 1RM.

4. Express the results relative to the client’s body weight (dividing the 1RM by the client’s weight).

The goal is to find the 1RM within a maximum of five attempts. A good familiarization period and clear communication between you and the client are key to an accurate and timely result.

Is 1RM testing safe for everyone? Research has demonstrated that if appropriate procedures are followed, this test is safe for all ages and even for individuals with various clinical conditions, such as cardiovascular disease, diabetes, obesity and pulmonary disease (Heyward 2002). However, many professionals in the fitness or rehabilitation setting do not use the 1RM test to a great extent, preferring to be cautious with clients who have pre-existing conditions. With these clients, using one of the prediction equations, which employ a much lower resistance, is a very helpful alternative. For a list of 1RM prediction equations, see Heyward 2002, page 128.