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Determining The Electromyographic Fatigue Threshold Following a Single Visit Exercise Test
Published on: July 27, 2015
Spring-mass behavior and electromyographic activity evolution during a cycle-run test to exhaustion in triathletes
1Research Department, National Institute of Sport, Expertise and Performance, 75012 Paris, France.
Summary
This study examined spring-mass (SM) behavior and electromyographic (EMG) activity in triathletes after cycling. Leg stiffness increased initially but decreased during the run, with muscle activity changes correlating to SM behavior.
Area of Science:
- Sports Science
- Biomechanics
- Exercise Physiology
Background:
- Understanding the biomechanical and neuromuscular responses to prolonged exercise is crucial for athlete performance and injury prevention.
- The transition from cycling to running in triathletes presents unique physiological demands.
- Previous research has explored fatigue but less is known about the specific interplay of spring-mass mechanics and muscle activation during a simulated triathlon cycle-run transition.
Purpose of the Study:
- To evaluate spring-mass (SM) behavior and associated electromyographic (EMG) activity during a run to exhaustion after a preceding cycle exercise in trained triathletes.
- To investigate the neuromuscular adaptations and biomechanical changes occurring during the transition from cycling to running.
Main Methods:
- Ten trained triathletes underwent maximal aerobic capacity (V˙O(2max)) and lactate threshold (LT) assessments.
- Participants completed a control run (C-Run) at LT and a cycle-to-run test to exhaustion (T-Run) involving 30 minutes of cycling followed by a run at LT.
- Spring-mass behavior and EMG signals from nine lower limb muscles were recorded during the running portions of both tests.
Main Results:
- Immediately post-cycling, leg stiffness was 12.1% higher compared to the C-Run, with increased knee extensor EMG activity during pre-contact.
- During the T-Run, leg stiffness decreased by 7.3%, and EMG activity in knee extensors and ankle flexors decreased during pre-contact and braking phases.
- No significant changes in overall SM parameters or muscle activity were observed between the C-Run and the end of the T-Run, suggesting fatigue did not drastically alter these measures by the end of the exhaustive run.
Conclusions:
- Spring-mass behavior during the cycle-run test was consistent with observed changes in EMG activity, indicating a coordinated neuromuscular response to fatigue.
- The cessation of exercise in this protocol was not associated with significant alterations in overall leg stiffness or EMG activity, suggesting a maintained capacity to regulate these parameters even at exhaustion.
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