Neuromuscular Fatigue Aetiology Comparison Between Prepubertal Boys and Adults
Condition: Neuromuscular Fatigue
MeSH terms: Fatigue
Study type: Observational

Summary: 
      Potential factors involved in neuromuscular fatigue were classified into two categories: 1)
      central factors involving the central nervous system and neural pathways, and 2) peripheral
      factors occurring within the muscle beyond the neuromuscular junction. In adults, it has been
      shown that peripheral factors contribute to a large part of the fatigue induced by repeated
      maximal contractions. However in children, central factors could account for the development
      of fatigue to a greater extent. Force-generating capacity and musculotendinous stiffness
      could be two of the discriminatory factors accounting for the differences in the
      neuromuscular fatigue between children and adults.

      Force production capacity and musculotendinous stiffness vary as function of muscle length.
      Naturally, they could differ depending on the muscle groups studied. The main aim of the
      present protocol is to compare the effect of knee extensors and ankle plantarflexors length
      on the development and aetiology of neuromuscular fatigue, in children and adults. The
      investigators formulated the hypotheses that at short muscle length force and low
      musculotendinous stiffness, differences in force between children and adults would be
      reduced. Thus neuromuscular fatigue development and aetiology would be similar between both
      groups. The results of the present protocol will allow to better understanding of the
      aetiology of neuromuscular fatigue in children and help improving training or rehabilitation
      programs.
    

Detailed description: 
      The study of neuromuscular fatigue in children is a recently topic in the field of sport
      sciences. Such knowledge could improve the efficiency and security of training and
      rehabilitation in healthy children and children with diseases like obesity.

      The LENGTH-FATIG study will provide knowledge about the peripheral and central mechanisms of
      the neuromuscular fatigue in children and adults. Fatigue will test for different muscle
      groups (knee extensors and ankle plantar flexors) at different muscle lengths (short, optimal
      and long).

      During high-intensity exercise, prepubertal children are more resistant to fatigue than
      adults. Contributions of the central and peripheral components to the development of
      neuromuscular fatigue are also different between both populations. The reduced children's
      fatigue coud be particularly related to a lower peripheral (i.e. muscular) fatigue. This
      might be attributed to the fact that prepubertal children rely more on oxidative than
      anaerobic metabolism than adults during fatiguing exercise. On the other hand, nervous
      factors could also explain differences in fatigue between children and adults. However, this
      topic is scarcely documented and still controversial. To our knowledge, no study has still
      compared the aetiology of central fatigue (supra-spinal vs. spinal) between children and
      adults. Only the voluntary activation level had been studied in children, conventionally used
      to assess central fatigue. But this factor doesn't differentiate spinal and supra-spinal
      contributions to neuromuscular fatigue development.

      The LENGTH-FATIG research project is a physiological and observational study comparing two
      age groups (adults and children). Subjects will have to perform three randomized fatigue
      protocols at three muscle lengths (short, optimal and long) with the knee extensors and the
      ankle plantar flexors.

      Data will be analyzed using LabChart 7.3 Pro software (ADInstrument, New South Wales,
      Australia) and Statistica 8.0 software (StatSoft, Inc.) and significance will be accepted at
      a two-sided alpha level of p<.05. The normality and homogeneity of the variables will be
      checked respectively from a Shapiro-Wilk test and a Barlett test.

      If normality and homogeneity of the variables are verified, absolute values of variables
      (Force, EMG, NIRS, etc.) will be compared using three factors (age x muscle length x muscle
      group) analyses of variance (ANOVA) with repeated measures. If analyses reveal a significant
      effect of any factor or interaction of factors, post-hoc Newman-Keuls tests will be performed
      to determine differences between the different conditions.

      If, on the contrary, normality and homogeneity of the variables are not verified, the effects
      of muscle length, muscle group and age will be evaluated using a Friedman test. If the tests
      show significant effects, comparisons of the different conditions will be performed using
      Mann-Whitney and Wilcoxon tests.
    

Intervention name(s): neuromuscular fatigue
Intervention type(s): Other
Intervention description(s): The main aim of the present protocol is to compare the effect of knee extensors and ankle plantarflexors length on the development and aetiology of neuromuscular fatigue, in children and adults
Observational model: Other
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        prepubertal boys and adults
      
Keywords: Children; Neuromuscular fatigue; Muscle group; Magnetic Nerve stimulation; Muscle length; Stiffness; prepubertal children; adults