Effect of eccentric exercise on position sense at the human forearm in different postures

Area of Science:

• Neuroscience
• Human Physiology
• Biomechanics

Background:

• Proprioception, the sense of limb position, is vital for motor control.
• The role of the sense of effort in proprioception, especially concerning forearm position sense, remains incompletely understood.
• Eccentric exercise is known to induce muscle fatigue and alter force production, potentially impacting sensory feedback.

Purpose of the Study:

• To investigate the contribution of the sense of effort to forearm position sense.
• To determine if eccentric exercise-induced changes in force production affect forearm position matching accuracy.
• To differentiate the influence of effort on position sense in gravity-dependent versus gravity-neutral tasks.

Main Methods:

• Human subjects performed forearm position matching tasks under different conditions: unsupported, counterweighted, and horizontal.
• Subjects' ability to match forearm position was assessed before and after eccentric exercise.
• Maximum voluntary muscle torque was measured to quantify exercise-induced strength deficits.

Main Results:

• Unsupported forearm position matching showed significantly higher accuracy (smaller errors) compared to counterweighted or horizontal matching prior to exercise.
• Eccentric exercise significantly increased matching errors in the unsupported task, but not in counterweighted or horizontal tasks.
• A decrease in maximum voluntary muscle torque was observed after exercise, correlating with increased errors in unsupported matching.

Conclusions:

• The sense of effort plays a significant role in forearm position sense, particularly when supporting the limb against gravity.
• Eccentric exercise-induced reductions in muscle force necessitate greater effort for limb stabilization, leading to proprioceptive errors in gravity-dependent tasks.
• Proprioceptive accuracy in gravity-neutral tasks is less affected by changes in the effort-force relationship following exercise.