Symptomatic and functional responses to concentric-eccentric isokinetic versus eccentric-only isotonic exercise

Area of Science:

• Exercise Physiology
• Sports Medicine
• Rehabilitation Science

Background:

• Eccentric resistance exercise, especially with loads exceeding 100% of 1-repetition maximum, enhances muscle function.
• The specific mode of eccentric exercise (isokinetic vs. isotonic) may influence delayed-onset muscle soreness and functional recovery.

Purpose of the Study:

• To compare functional and symptomatic responses between an eccentric-only (ECC) isotonic protocol and a concentric-eccentric (CON-ECC) isokinetic protocol.
• Both protocols were matched for total exercise volume to isolate the effects of exercise mode.

Main Methods:

• A controlled laboratory study involving 24 healthy, untrained college-aged participants (12 men, 12 women).
• Participants were randomized to either the ECC isotonic or CON-ECC isokinetic elbow flexor exercise group.
• Measurements included isometric strength, elbow flexion/extension range of motion, and muscle tenderness, assessed at baseline and days 2, 4, 7, and 14 post-exercise.

Main Results:

• The ECC isotonic group experienced significant strength deficits (30-36%) and reduced range of motion (5-8%) on days 2 and 4.
• The CON-ECC isokinetic group showed no significant changes in strength or range of motion compared to baseline.
• Muscle tenderness increased in both groups on days 2 and 4, with no significant difference between the groups.

Conclusions:

• Eccentric-only isotonic exercise resulted in more substantial functional impairments than CON-ECC isokinetic exercise when matched for volume.
• The findings highlight the importance of exercise mode in managing functional recovery and symptoms after eccentric resistance training.