Muscle conduction velocity, surface electromyography variables, and echo intensity during concentric and eccentric...

Area of Science:

• Exercise Physiology
• Muscle Physiology
• Biomechanics

Background:

• Concentric (CON) and eccentric (ECC) muscle contractions may differentially affect sarcolemma integrity and action potential propagation.
• Understanding these differences is crucial for exercise science and rehabilitation.

Purpose of the Study:

• To compare the effects of CON and ECC contractions on muscle function and damage.
• To investigate alterations in action potential transmission and muscle quality following different contraction types.

Main Methods:

• Muscle conduction velocity (CV), surface electromyography (sEMG), muscle quality (echo intensity), and blood lactate were measured during and after CON and ECC actions.
• Analysis focused on changes in these parameters between the two contraction types.

Main Results:

• CON exercise resulted in greater force loss, elevated blood lactate, and more significant sEMG alterations compared to ECC.
• Both CON and ECC protocols showed similar reductions in muscle CV.
• Muscle damage, indicated by higher echo intensity, was more pronounced after ECC exercise 2 days post-activity.

Conclusions:

• The impact of ECC-induced muscle damage on action potential transmission (CV) may be comparable to the effect of hydrogen accumulation from CON exercise.
• CON exercise leads to greater force loss and sEMG changes than ECC, potentially due to higher lactate accumulation.