Superimposed Tendon Vibration Increases Time to Task Failure During Intermittent Isometric Knee Extensions: Effects...

Area of Science:

• Biomechanics
• Exercise Physiology
• Neuromuscular Function

Background:

• Muscle fatigue limits physical performance and is influenced by contraction intensity and duration.
• Superimposed local vibration (SLV) is a technique explored for its potential to modulate muscle responses during exercise.
• Understanding factors that enhance muscular endurance is crucial for optimizing training and rehabilitation.

Purpose of the Study:

• To evaluate if superimposed local vibration (SLV) increases time to task failure (TTF) during submaximal isometric knee extensor contractions.
• To assess the impact of SLV at low (30% MVIC) and moderate (50% MVIC) intensities.
• To determine if the effects of SLV on TTF differ between sexes.

Main Methods:

• Fifty-two healthy adults performed intermittent isometric knee extension tasks until task failure under SLV and control conditions.
• Participants were assigned to 30% or 50% Maximal Voluntary Isometric Contraction (MVIC) intensity groups.
• Torque and electromyographic activity (EMG) were recorded; TTF was defined as a >10% drop in torque.

Main Results:

• SLV significantly increased TTF by approximately 9.5% compared to the control condition (p < 0.001).
• Torque Time Integral (TTI) was also significantly higher with SLV (p < 0.001).
• These benefits were observed irrespective of contraction intensity or sex, with no significant interactions.

Conclusions:

• Superimposed local vibration effectively enhances time to task failure and force production during submaximal intermittent isometric contractions.
• The positive effects of SLV on endurance are consistent across different intensities and between sexes.
• Further research is needed to explore the mechanisms behind unchanged EMG despite improved performance with SLV.