Contralateral Repeated Bout Effect of the Knee Flexors

Area of Science:

• Exercise Physiology
• Muscle Physiology
• Sports Science

Background:

• Eccentric exercise can cause muscle damage.
• The contralateral repeated bout effect (CL-RBE) demonstrates that prior eccentric exercise in one limb can protect the contralateral limb from subsequent muscle damage.
• Previous research established CL-RBE for elbow flexors, but its existence for knee flexors was unknown.

Purpose of the Study:

• To investigate if a contralateral repeated bout effect (CL-RBE) exists for knee flexors (KF).
• To determine the time course of KF CL-RBE at 1, 7, and 28 days after the initial bout of eccentric exercise.
• To compare the magnitude of KF CL-RBE with previously reported CL-RBE for elbow flexors.

Main Methods:

• Young, untrained men performed 60 maximal knee flexor eccentric contractions (60MaxEC) with one leg.
• Participants were assigned to groups that repeated the 60MaxEC with the contralateral leg after 1, 7, or 28 days.
• A control group repeated the exercise after 14 days, and indirect muscle damage markers were analyzed.

Main Results:

• Initial muscle damage markers were similar across groups after the first bout.
• Subsequent bouts showed reduced muscle damage in the 1-day and 7-day groups compared to the initial bout.
• The magnitude of CL-RBE for knee flexors was comparable to that observed for elbow flexors in prior studies.

Conclusions:

• Contralateral repeated bout effect (CL-RBE) is evident for knee flexors, mirroring findings for elbow flexors.
• The protective effect of CL-RBE for knee flexors persists for at least 7 days but diminishes by 28 days.
• The contralateral effect on knee flexors is less pronounced than the ipsilateral repeated bout effect.