Researchers wanted to know if TheraBand CLX elastic bands could be used to estimate shoulder strength using submaximal contractions. This method would offer advantages of portability and less expense than manual muscle dynamometers. In addition, submaximal testing may be beneficial when testing individuals with pain, where maximal muscle testing may not be possible.
9 healthy male subjects performed shoulder abduction exercise with TheraBand CLX bands at different intensities. Multiple bands were combined to increase the resistance. The researchers found that the number of repetitions and intensity of exercise were related to maximal abduction strength, allowing them to estimate shoulder torque. They calculated an equation to predict the relative torque (the percent of maximal strength, or % of 1RM) based on the number of repetitions performed: % 1RM = -1.1628(Repetitions) + 98.789
This equation predicts that as the number of repetitions increase, the intensity as a relative percentage of maximal strength decreases linearly (more repetitions equates to less intensity). Therefore, if the individual was able to complete 10 repetitions with the resistance, they were predicted to be at 87% of their maximal intensity, or 87% 1RM.
The data has implications not only in predicting muscle strength, but also in prescribing TheraBand resistance exercises. For example, if the clinician wants to prescribe an intensity of shoulder abduction exercise about 75% of 1RM, they should use a resistance that allows them to complete 20 repetitions (20RM).
Micheletti JK et al. 2017. Determination of Shoulder Abduction Strength Using a Submaximal Elastic Band J Perform Health Res 1(2):31-39.
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