Evidence of a contralateral repeated bout effect after maximal eccentric contractions

Area of Science:

• Exercise Physiology
• Sports Science
• Muscle Physiology

Background:

• Eccentric muscle contractions can lead to muscle damage, soreness, and reduced strength.
• The repeated bout effect (RBE) describes the protective phenomenon against subsequent muscle damage after an initial bout of exercise.
• The neural and mechanical mechanisms underlying the RBE are not fully understood, especially concerning contralateral effects.

Purpose of the Study:

• To investigate the presence and magnitude of a contralateral repeated bout effect following maximal eccentric exercise.
• To compare the protective effects observed in the contralateral limb versus the ipsilateral limb.

Main Methods:

• Sixteen male subjects performed 45 maximal eccentric contractions of the elbow flexors.
• Subjects were divided into an ipsilateral (IL) group performing the same-arm exercise again and a contralateral (CL) group performing the exercise with the opposite arm after 14 days.
• Measurements included serum creatine kinase (CK), muscle soreness, maximal voluntary contraction (MVC), and range of motion (ROM).

Main Results:

• Both IL and CL groups showed significant attenuation in CK, muscle soreness, and MVC during the repeated bout.
• The magnitude of protection (reduction in CK, soreness, MVC, ROM) was significantly less in the CL group compared to the IL group.
• Range of motion (ROM) was also significantly attenuated in the repeated bout for the IL group, with a lesser but significant attenuation in the CL group.

Conclusions:

• A single bout of maximal eccentric exercise induces a protective effect in the contralateral limb.
• The contralateral repeated bout effect is less pronounced than the ipsilateral repeated bout effect.
• Neural mechanisms are hypothesized to be the primary mediators of the contralateral repeated bout effect, warranting further investigation.