Comparison of contraction intensity and perceived intensity between dominant and non-dominant leg in sedentary adults

Introduction
Accurate measurement of isometric contraction intensity is a prerequisite for establishing an exercise program and developing a rehabilitation plan. Despite numerous studies performed previously, there is no research on sedentary populations susceptible to injury during exercise. Additionally, although dominant and non-dominant legs showed differences in muscle properties, the legs were not separately investigated. The purposes of this study were to compare the contraction intensity with target intensity and with perceived intensity across 3 different target intensities in sedentary adults and examine the difference between the dominant and non-dominant leg.

Methods
Voluntary isometric contractions were performed with resistance provided by a sling rope and measured with a strain gauge during hip extension. First, maximum voluntary contraction (MVC) was executed; subsequently, submaximal contractions at target intensities (75%, 50%, and 25% of MVC) were randomly performed. Perceived intensity was measured at each target intensity.

Results
Hip extension forces were significantly different across the 3 intensities (p < 0.001), with no significant difference between target intensity and contraction intensity or between perceived intensity and contraction intensity. There was no significant difference between the dominant and non-dominant leg. Bland-Altman analysis of the agreement between perceived and contraction intensities revealed a proportional bias for the values within each target intensity (mean bias: –1.15%, standard deviation of bias: 20.96).

Conclusions
Sedentary subjects were able to distinguish 3 different contraction intensities. Perceived intensity could statistically significantly predict contraction intensity. However, clinicians should note that under- or overestimation can occur regardless of the level of target intensity.