Drupal
Athletic development specialists dedicated to the art and science of excellence in movement

Review: Fatigue and Stability in Elite Gymnasts

Here’s a chicken or the egg problem for today…does a weak trunk cause fatigue or does fatigue impair the trunk?  You can make compelling arguments in both directions.  Perhaps weak trunk musculature causes inefficient movements elsewhere in the body, leading to premature fatigue.  Alternatively, any activity when performed to fatigue (even if not isolated to the core) may impair the trunk.  Perhaps too, the trunk is merely the proxy by which many choose to measure stability in the nervous system.

One recent study from The Netherlands (van Dieën 2012) addressed these questions with a study of nine elite female gymnasts (average age = 12 years).  Overall, the evidence how fatigue may affect trunk stability is inconsistent…some found fatigue did have an effect, but others did not (more on why below). 

In this study, to induce fatigue, the gymnasts performed four series of five dump handstands on the uneven bar.  Before and after these trials, gymnasts performed two seated balance tasks: one measuring the ability to remain still without external perturbations; and one measuring their ability to adjust to external perturbations.

Results:

“unperturbed seated balancing performance was decreased in the anterior–posterior direction as evidenced by a larger amplitude and lower frequency.”  (In other words, while trying to remain still, their front to back-sway increased)

“no effect was found on sway in the frontal plane.”  (but no side-to-side sway)

“the maximum displacement after the perturbation was larger and the recovery of balance was slower after the exercise than before. “ (gymnasts lost their position to a greater degree and were slower to recover while fatigued)

What does this Mean?

Above we noted that studies conflict on whether fatigue will significantly affect trunk stability.  One reason for this conflict is that compensatory movement may create an impression of motor control when in fact the body is simply working harder to achieve a satisfactory visual result.  Some people are great “compensators,” and may explain why some previous studies have not captured the effect of external fatigue on core control.  (“It was suggested that compensatory mechanisms such as increased cocontraction and increased reflex gains could explain the absence of fatigue effects in some of these studies.”) 

Someone can use excess tension to retain normal upright posture yet visually appear perfectly relaxed.  This is yet another reason why superficial “form coaching” is wholly inadequate without consideration of underlying movement patterns and the body’s underlying physical state of fatigue or rest.  In fact, authors specifically designed this experiment to avoid the effects of compensatory movement.

“we used a dynamic balancing task to test trunk stability. In this task, the center of mass unavoidably sways beyond the surface of support, which is the point of contact of the hemisphere on the force plate. Trunk moments, accelerating the upper body relative to the pelvis and seat, must then be used to bring the center of mass back over the surface of support, while stiffening the trunk would not be effective It has previously been shown that cocontraction, which would stiffen the trunk is not effective in this task.”

Authors note several implications of fatigue on trunk stability:

  • Increase in force is needed to react to fatigue
  • Fatigue will likely slow down muscular responses due to increased proprioceptive thresholds
  • Increased proprioceptive thresholds might be reflected specifically in an increase in the maximum displacement after the perturbation
  • Fatigue could be associated with an increased respiratory challenge, which might affect trunk stability  

These gymnasts performed a relatively simple task (for them) of repeated handstands, but the trunk stability impairment was significant.  What’s critical is that many forms of trunk stability training may be teaching athletes to compensate better, when we mustn’t forget the value of preventing the onset of fatigue.  In fact, some would suggest practicing ways to compensate better under fatigue states may impair motor learning.  As Dr. Rushall reminds us, 

"The body does not have the capacity to learn movement patterns when highly stressed/fatigued. This factor is not related to the specificity of training principle associated with overload adaptation in energy systems. The specificity principle of physiological adaptation does not apply to motor learning. To learn skilled movement patterns that are to be executed under fatigued conditions, that learning has to occur in non-fatigued states"   (Williams 1979)

Realistically, it’s neither practical nor advisable to halt training at very first sign of fatigue, but this study does quantify the effect that fatigue has on trunk stability and reinforces that trunk stability is more a reactive quality than one to be trained directly.  Ultimately, trunk stability training can be seen as an insurance policy but we must not get too enamored with trunk stability training lest we lose sight of an overall training picture to avoid the deterioration of movement quality.    

Finally, also consider the injury implications.  Although it was not studied specifically, we might infer that joint position may also be affected in the same manner as the overall trunk whenever a perturbation occurs.  Instability in this study manifested itself as an impaired ability to “recover” from a perturbation.  Authors only looked at the trunk as a whole, but the perturbation effects may also apply within the joint and possibly lead to injury.    

References

Williams, L. R., McEwan, E. A., Watkins, C. D., Gillespie, L., & Boyd, H. (1979). Motor learning and performance and physical fatigue and the specificity principle. Canadian Journal of Applied Sport Sciences, 4, 302-308. 

van Dieën JH, Luger T, van der Eb J.  Effects of fatigue on trunk stability in elite gymnasts.  Eur J Appl Physiol. 2012 Apr;112(4):1307-13. Epub 2011 Jul 23.

Comments

Post new comment

The content of this field is kept private and will not be shown publicly.
CAPTCHA
This question is for testing whether you are a human visitor and to prevent automated spam submissions.
Image CAPTCHA
Enter the characters shown in the image.