Central and peripheral contributions to fatigue after electrostimulation training.

Area of Science:

• Exercise Physiology
• Neuromuscular Physiology
• Rehabilitation Science

Background:

• Neuromuscular electrical stimulation (NMES) is used to enhance muscle function.
• Understanding the impact of NMES on task failure and underlying physiological mechanisms is crucial for optimizing training protocols.

Purpose of the Study:

• To investigate the effects of 4 and 8 weeks of NMES training on knee extensor endurance time.
• To determine how NMES training influences the mechanisms contributing to task failure.

Main Methods:

• Ten males performed fatiguing isometric knee extensor contractions at 20% maximal voluntary contraction (MVC) until exhaustion.
• Central and peripheral fatigue were assessed using electromyography (EMG) and evoked contractions before and after fatiguing tasks.
• Measurements were taken before NMES training (B), at 4 weeks (WK4), and at 8 weeks (WK8).

Main Results:

• Knee extensor MVC torque significantly increased with NMES training (26% from B to WK8).
• Endurance time significantly decreased over the training period (493s at B, 408s at WK4, 338s at WK8).
• Despite reduced endurance, the magnitude of central and peripheral fatigue, and single-twitch properties remained unaffected.

Conclusions:

• NMES training for 4 and 8 weeks led to a shorter endurance time, primarily due to increased absolute contraction intensity.
• NMES training did not alter the physiological contributions to task failure or the overall amount of fatigue experienced.