Muscle Damage Indicated by Maximal Voluntary Contraction Strength Changes From Immediately to 1 Day After Eccentric Exercise of the Knee Extensors.

Akihiro Kanda,Ryota Akagi,Mikio Shoji,Kazunori Nosaka,Kosuke Hirata,Ryoichi Ema

doi:10.3389/fphys.2021.775157

Abstract

The present study examined if the magnitude of changes in indirect muscle damage markers could be predicted by maximal voluntary isometric contraction (MVIC) torque changes from immediately to 1 day after eccentric exercise. Twenty-eight young men performed 100 maximal isokinetic (60°/s) eccentric contractions of the knee extensors. MVIC torque, potentiated doublet torque, voluntary activation (VA) during MVIC, shear modulus of rectus femoris (RF), vastus medialis and lateralis, and muscle soreness of these muscles were measured before, immediately after, and 1–3 days post-exercise. Based on the recovery rate of the MVIC torque from immediately to 1-day post-exercise, the participants were placed to a recovery group that showed an increase in the MVIC torque (11.3–79.9%, n = 15) or a no-recovery group that showed no recovery (−71.9 to 0%, n = 13). No significant difference in MVIC torque decrease immediately post-exercise was found between the recovery (−33 ± 12%) and no-recovery (−32 ± 9%) groups. At 1–3 days, changes in MVIC torque (−40 to −26% vs. −22 to −12%), potentiated doublet torque (−37 to −22% vs. −20 to −9%), and proximal RF shear modulus (29–34% vs. 8–15%) were greater (p < 0.05) for the no-recovery than recovery group. No significant group differences were found for muscle soreness. The recovery rate of MVIC torque was correlated (p < 0.05) with the change in MVIC torque from baseline to 2 (r = 0.624) or 3 days post-exercise (r = 0.526), or peak change in potentiated doublet torque at 1–3 days post-exercise from baseline (r = 0.691), but not correlated with the changes in other dependent variables. These results suggest that the recovery rate of MVIC torque predicts changes in neuromuscular function but not muscle soreness and stiffness following eccentric exercise of the knee extensors.

Highlights

Unaccustomed eccentric exercises induce muscle damage that is accompanied by symptoms such as prolonged strength loss, delayed onset muscle soreness (DOMS), and increased muscle stiffness (Clarkson et al, 1992)
The results showed that the decreases in MVIC torque and potentiated doublet torque, FIGURE 1 | Changes in maximal voluntary isometric contraction (MVIC) torque (A), potentiated doublet torque (B), and voluntary activation (VA) during the MVIC (C) before, immediately after (0), and 1–3 days after eccentric exercise for the recovery and no-recovery groups. * Indicates a significant difference from baseline. † Shows a significant difference between groups. # Demonstrates a significant interaction effect. ns shows no significant interaction effect
The present study found large individual differences in the recovery rate of MVIC torque from immediately to 1 day after knee extensor eccentric exercise

Summary

Introduction

Unaccustomed eccentric exercises induce muscle damage that is accompanied by symptoms such as prolonged strength loss, delayed onset muscle soreness (DOMS), and increased muscle stiffness (Clarkson et al, 1992). Muscle strength is considered the best indirect muscle damage marker (Paulsen et al, 2012), but a decrease in muscle strength is not solely due to muscle damage, since it is a consequence of neuromuscular fatigue (Souron et al, 2018). Changes in muscle strength are affected by central and peripheral functions, with prolonged strength loss being mainly due to peripheral damage (Hubal et al, 2007; Souron et al, 2018). It is important to predict the magnitude of symptoms of muscle damage such as DOMS and loss of muscle function with the assessment of central and peripheral factors in days after eccentric exercises

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Discussion

Conclusion