The impact of eccentric muscle contractions on peripheral nerve integrity.

Abstract

Background and aims: Besides muscle damage, eccentric contractions also impose significant mechanical loads on peripheral nerves. However, the impact of eccentric contractions on peripheral nerve properties remains unclear. We aimed to reveal the immediate (i.e., <2 h and short-term (i.e., <10 days) effects of eccentric contractions on functional, structural, morphological, physiological and biomechanical properties of peripheral nerves.

Methods: Four electronic databases (PubMed, Science Direct, PEDro and Cochrane) were searched for animal and human studies which evaluated the immediate and/or short-term impact of eccentric contractions of upper or lower limb muscles on outcomes related functional, structural, morphological, physiological and biomechanical properties of peripheral nerves.

Results: From a total of 2415 articles, two human and two animal studies met the selection criteria. Several signs of nerve damage following eccentric exercises were observed, such as reductions in myelin sheath thickness, nerve fibre diameter, sensory and motor nerve conduction velocity, and protein zero levels, alongside increased levels of macrophage-related protein and tropomyosin receptor kinase C. No significant changes were identified in growth-associated protein 43. It is worth noting that some variables exhibited differences in their time course between human and animal studies. Animal studies revealed that the effects were more pronounced when eccentric contractions were performed at higher velocities.

Conclusion: Current evidence is suggestive that eccentric contractions has the potential to alter the peripheral nerves structural, morphological, functional and physiological properties, which are indicative of nerve damage.

Systematic review registration: CRD42021285767.