Effects of submaximal eccentric exercise on muscle activity at different elbow joint angles

Area of Science:

• Biomechanics
• Exercise Physiology
• Muscle Physiology

Background:

• Eccentric exercise (ECC) is known to cause reductions in maximal voluntary contraction (MVC) torque and muscle soreness.
• The specific contributions of electrical and mechanical factors to these deficits, and their dependence on elbow joint angle, remain incompletely understood.

Purpose of the Study:

• To investigate whether factors contributing to torque reduction and muscle soreness after ECC are elbow-joint-angle specific.
• To determine the extent to which joint angle influences antagonist coactivation's role in torque reduction.

Main Methods:

• Maximal isometric torque (MIT), muscle soreness, agonist electromechanical activity, and antagonist coactivation were measured.
• Measurements were taken at elbow joint angles of 60°, 90°, and 150° before ECC, immediately after, and at 24, 48, 72, and 120 hours post-exercise.

Main Results:

• ECC induced immediate MIT decrease and increased antagonist coactivation across all tested angles.
• Antagonist coactivation normalized by 24 hours post-exercise, irrespective of joint angle.
• The most rapid torque recovery and highest pain threshold during force generation were observed following ECC at a 60° elbow joint angle.
• Mechanomyography showed no changes during recovery, while electrical activity varied between joint angles.

Conclusions:

• The effects of eccentric exercise on torque production and muscle soreness are influenced by elbow joint angle.
• Specific joint angles, like 60°, may facilitate faster recovery of muscle function after eccentric contractions.
• While antagonist coactivation normalizes quickly, underlying electrical activity differences suggest angle-dependent neuromuscular adaptations during recovery.