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Increases in M-wave latency of biceps brachii after elbow flexor eccentric contractions in women

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Abstract

Purpose

Eccentric contractions (ECCs) induce muscle damage that is indicated by prolonged loss of muscle function and delayed onset muscle soreness. It is possible that ECCs affect motor nerves, and this may contribute to the prolonged decreases in force generating capability. The present study investigated the hypothesis that M-wave latency of biceps brachii would be increased after maximal elbow flexor ECCs resulting in prolonged loss of muscle strength.

Methods

Fifteen women performed exercise consisting of 60 maximal ECCs of the elbow flexors using their non-dominant arm. M-wave latency was assessed by the time taken from electrical stimulation applied to the Erb’s point to the onset of M-wave of the biceps brachii before, immediately after, and 1–4 days after exercise. Maximal voluntary isometric contraction (MVC) torque, range of motion (ROM) and muscle soreness using a numerical rating scale were also assessed before and after exercise.

Results

Prolonged decreases in MVC torque (1–4 days post-exercise: −54 to −15 %) and ROM (1–2 days: −32 to −22 %), and increased muscle soreness (peak: 4.2 out of 10) were evident after exercise (p < 0.05). The M-wave latency increased (p < 0.01) from 5.8 ± 1.0 ms before exercise to 6.5 ± 1.7 ms at 1 day and 7.2 ± 1.5 ms at 2 days after exercise for the exercised arm only. No significant changes in M-wave amplitude were evident after exercise.

Conclusion

The increased M-wave latency did not fully explain the prolonged decreases in MVC torque after eccentric exercise, but may indicate reversible motor nerve impairment.

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Abbreviations

CK:

Creatine kinase

CNT:

Control conduction

CV:

Coefficient of variation

DOMS:

Delayed onset muscle soreness

E–C coupling:

Excitation contraction coupling

ECCs:

Eccentric contractions

mdx:

Muscular dystrophy

MFCV:

Muscle fiber conduction velocity

MsN:

Musculocutaneous nerve

NCV:

Nerve conduction velocity

NMJ:

Neuromuscular junction

NRS:

Numerical rating scale

ROM:

Range of motion

SD:

Standard deviation

SR:

Sarcoplasmic reticulum

t-tubule:

Transverse tubule

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Authors and Affiliations

Authors

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Correspondence to Karina Kouzaki.

Additional information

Communicated by Toshio Moritani.

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Cite this article

Kouzaki, K., Nosaka, K., Ochi, E. et al. Increases in M-wave latency of biceps brachii after elbow flexor eccentric contractions in women. Eur J Appl Physiol 116, 939–946 (2016). https://doi.org/10.1007/s00421-016-3358-2

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  • DOI: https://doi.org/10.1007/s00421-016-3358-2

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