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Alterations of neuromuscular function after an ultramarathon
G Y Millet1, R Lepers, N A Maffiuletti
1Groupe Analyse du Mouvement, Faculté des Sciences du Sport, Université de Bourgogne, 21078 Dijon Cedex, France. gmillet@u-bourgogne.fr
Journal of Applied Physiology (Bethesda, Md. : 1985)
|January 18, 2002
Summary
Ultramarathon running significantly reduced maximal voluntary force due to lower muscle activation. However, muscle twitch response was unexpectedly enhanced, indicating complex neuromuscular fatigue after endurance events.
Area of Science:
- Exercise Physiology
- Neuromuscular Function
- Sports Science
Background:
- Understanding neuromuscular fatigue mechanisms is crucial for optimizing athletic performance and recovery.
- Ultramarathon running presents a unique challenge to the neuromuscular system, necessitating detailed investigation.
Purpose of the Study:
- To characterize neuromuscular fatigue in knee extensor (KE) and plantar flexor (PF) muscles post-ultramarathon.
- To investigate changes in maximal voluntary contraction (MVC), voluntary activation, and evoked twitch properties.
Main Methods:
- Nine well-trained runners completed a 65-km ultramarathon.
- Neuromuscular function of KE and PF muscles was assessed before and after the race using nerve stimulation.
- Measurements included MVC, superimposed twitches for voluntary activation, and peak twitch characteristics.
Main Results:
- Significant decreases in MVC (-30.2%) and maximal voluntary activation (-27.7%) were observed post-race.
- Surprisingly, peak twitch force increased for both KE and PF muscles.
- Contraction and relaxation times shortened, while M-wave characteristics remained largely unchanged, except for the soleus.
Conclusions:
- Ultramarathon running severely impairs maximal voluntary force primarily through reduced voluntary activation.
- The study observed a potentiation of the muscle twitch mechanical response, contrary to typical fatigue patterns.
- Neuromuscular fatigue after 65 km of running affects voluntary drive more than peripheral nerve excitability.