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Induction and Assessment of Exertional Skeletal Muscle Damage in Humans
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Muscle activation during leg-press exercise with or without eccentric overload.

F Sarto1, M V Franchi2, P A Rigon1

  • 1Institute of Physiology, Department of Biomedical Sciences, University of Padua, Padua, Italy.

European Journal of Applied Physiology
|May 25, 2020
PubMed
Summary

Eccentric overload training significantly increases vastus lateralis (VL) muscle motor unit recruitment during leg press. This new machine overcomes normal motor unit derecruitment in the eccentric phase, enhancing neuromuscular responses.

Keywords:
Concentric exerciseEccentric exerciseElectromyographyNeural driveResistance trainingVoluntary muscle activation

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Area of Science:

  • Biomechanics
  • Exercise Physiology
  • Neuromuscular Adaptations

Background:

  • Electromyographic (EMG) activity during resistance exercise is crucial for understanding muscle activation.
  • Conventional leg press machines may not optimize motor unit recruitment during the eccentric phase.
  • New equipment allows for controlled eccentric overloading.

Purpose of the Study:

  • To investigate the electromyographic (EMG) activity of the vastus lateralis (VL) muscle during concentric-eccentric exercise.
  • To evaluate the effect of a new leg press machine with preset eccentric overloading.
  • To compare EMG activity with and without eccentric overload.

Main Methods:

  • Ten young males performed leg press exercises at 70% and 80% of 1-RM.
  • Exercise included sets with (ECC+) and without (ISOW) 150% eccentric overload.
  • Surface EMG of the VL muscle was recorded and integrated (iEMG).

Main Results:

  • Integrated EMG (iEMG) was significantly higher with eccentric overload (ECC+) compared to ISOW (approx. 30% increase).
  • No significant differences in EMG were found between concentric and eccentric phases in ECC+ conditions.
  • Higher motor unit recruitment was observed with eccentric overload.

Conclusions:

  • Training with 150% eccentric overload enhances VL muscle motor unit recruitment during leg press.
  • The Biostrength® machine overcomes the typical derecruitment of motor units during the eccentric phase.
  • This approach may be important for maximizing neuromuscular adaptations in strength training.