Eccentric Exercise Alters The Kinematic Structure Of Pointing Movements

Abstract

It is known that the performance of eccentric muscle contractions often leads to delayed muscle soreness accompanied by declines in strength and isometric force steadiness. However, the effect of eccentric exercise on the performance of a dynamic motor task is not clear. PURPOSE: To examine the effects of a bout of eccentric exercise on kinematic measures related to accuracy (i.e. submovements) during spatially-constrained pointing movements. METHODS: 17 untrained subjects (10 M, 7 F; 26 ± 3 yrs.) performed 20 rapid discrete elbow-extension pointing movements with their right arm before, immediately after (fatigue and muscle damage), and 24-hours after (muscle damage only) fatiguing eccentric exercise on a isokinetic dynamometer. Endpoint (fingertip) movement kinematics were obtained for each pointing trial and examined for secondary submovements indentified by zero crossings in the tangential velocity and acceleration profiles. RESULTS: MVC force declined by 44% immediately after eccentric exercise and remained depressed (22%) 24-hrs after the exercise indicating the existence of muscle damage. Movement times were slower and peak velocity decreased immediately after, and only partially recovered 24-hrs after the exercise compared with before (222 ± 40, 248 ± 37 and 238 ± 42ms, P<0.05; 3.4 ± 0.6, 3.1 ± 0.6 and 3.3± 0.7m/s, P<0.01). Only 8% of the trials exhibited submovements before the eccentric exercise, however that number grew to 87% of trials immediately afterward and 29% of trials 24 hrs after. In those trials requiring submovements, subjects traveled 85 ± 8, 64 ± 6 and 72 ± 11% (P<0.001) of the total movement time before using a secondary submovement. CONCLUSIONS: These results demonstrate that kinematic measures associated with movement accuracy are altered from eccentric exercise and only partially restored after 24 hrs.