PERCEIVED EFFORT IN UNILATERAL AND BILATERAL ISOMETRIC EXERTIONS

Abstract

Listen

Translate article

Subjects produce larger unilateral forces than bilateral forces for the same perceived submaximal effort. This submaximal bilateral deficit has been attributed to physiological and perceptual components. PURPOSE To examine the perceived effort of unilateral and bilateral exertions when absolute force was held constant. METHODS Forty-two healthy subjects (22.8±3.5 yrs. 171.0±26.4 cm, 69.4±10.7 kg) without upper extremity injury performed three 3-second trials each of bilateral (B), unilateral dominant (UD) and non-dominant (UN) elbow flexion at 100%, 80%, 60%, 40%, and 20% of maximal effort. Subjects matched force production to a target force using visual feedback from a realtime display. Subjects indicated perceived effort for that trial using a standardized measurement scale. RESULTS The mean coefficient of variation of force for maximal effort trials ranged from 4.8–5.8% and 1.6–2.3% for submaximal effort trials. The bilateral index at 100% effort (−8.6±5.6%) was significantly less than zero but was small (< 1%) for submaximal trials. Unilaterally, subjects matched the target force of 80% maximum effort most closely (79.6±10.9% and 79.0±7.9%, UD and UN, respectively). At the 60% target force subjects slightly overestimated the effort they were producing in UD and UN (63.7±9.2% and 62.1±8.8%, respectively). This overestimation increased at the 40% and 20% target forces in UD and UN (47.1±9.6%, 46.5±7.6%, 27.8±11.5%, and 26.0±11.3%, respectively). The perception of effort in bilateral trials was consistently and significantly (p < 0.01) higher than recorded in unilateral trials. Perceived effort at 80% and 60% target force was 7.9–9.6% higher in bilateral trials than unilateral trials (87.2±8.1% and 71.6±9.1%, respectively). The elevated perception of effort in bilateral trials was slightly less at the 40% and 20% target forces but still ranged from 5.5–7.2% higher than in unilateral trials (52.6±9.7% and 33.3±10.4%, respectively). CONCLUSION Force production was perceived to be more strenuous when performed bilaterally suggesting that the submaximal bilateral deficit contains a perceptual component.