Muscle activation during leg-press exercise with or without eccentric overload

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.