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OVERVIEW. Definitions Where are we at? Central measures of fatigue Peripheral measures of fatigue Summation Research suggestions References. DEFINITIONS. Central fatigue
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1. PERFORMANCE BASED MEASURES OF RECOVERY IN POWER/SPEED SPORTS
2. OVERVIEW Definitions
Where are we at?
Central measures of fatigue
Peripheral measures of fatigue
Summation
Research suggestions
References
3. DEFINITIONS Central fatigue insufficient neural drive to the muscles (Garrandes et al. 2005)
Peripheral fatigue changes beyond the neuromuscular junction (Garrandes et al. 2005)
Neural plasticity - the process whereby patterns of impulses into mature synapses can cause long-lasting changes in the magnitude of the subsequent stimulation (Armstrong & VanHeest, 2002)
4. WHERE ARE WE AT? Most research has concentrated on metabolic & biochemical markers
Neural processes are not well understood, particularly how they respond to exercise
Techniques to measure NCV, neural drive & reflex response need consistency & refinement
Most research admits difficulty in differentiating between central & peripheral fatigue
Markers showing promise include power decrement, EMG:force ratio, reflex inhibition, NCV
5. CENTRAL MEASURES Noakes (2000):
Brain [neurotransmitter] alters rate coding during exercise
CNS deactivates as a protective mechanism (some support for this theory)
Hautier et al. (2000) constant EMG:force ratio concurrent with force decrease
Ross et al. (2001) NCV is promising
Koceja et al. (2004) Hmax:mmax ratio
Reflex sensitivity most support in literature but can be affected by metabolic by-products
CMJ research inconclusive but promising
6. PERIPHERAL MEASURES High frequency model impaired AP propagation along muscle fibre
Paasuke et al. (1999) electromechanical delay
Glaister et al. (2005) - metabolic acidosis is not a limiting factor in excitation-contraction coupling (no EMG)
Jereb and Strojnik (2003) imbalance of [Na+] & [K] impair AP propagation
7. SINGLE-LEG HOP STUDY
8. SUMMARY Trial & error with a combination of markers (ie PT reflex inhibition & power decrement)
Power decrement assessment is simple & results are immediate (event implications)
The central vs peripheral debate appears academic (what are the practical implications?)
Consider neural plasticity vs fatigue for different sports & individuals
9. RESEARCH SUGGESTIONS Correlations between biochemical & neural markers
More studies using trained subjects & dynamic fatigue protocols
Efficacy of simple reaction-time tests in the field
Validity of field measures (single-leg hop) compared to lab tests
10. REFERENCES 1. Armstrong, L.E. and VanHeest, J.L. The unknown mechanism of the overtraining syndrome. Clues from depression and psychoneuroimmunology. Sports Med. 32(3):185-209, 2002.
2. Garrandes, F., Colson, S.S., Pensini, M. and Legros, P. Neuromuscular fatigue kinetics are sport specific. Computer Methods in Biomechanics and Biomedical Engineering. Supplement 1:113-114, 2005.
3. Augustsson, J., Thomee, R., Linden, C., Folkesson, M., Tranberg, R. and Karlsson, J. Single-leg hop testing following fatiguing exercise: reliability and biomechanical analysis. Scandinavian Journal of Medicine and Science in Sports. 16:111-120, 2006.
4. Hautier, C.A., Arsac, L.M., Deghdegh, K., Souquet, J., Belli, A. and Lacour, J. Influence of fatigue on EMG/force ratio and cocontraction in cycling. Medicine and Science in Sports and Exercise. 32(4):839-843, 2000.
5. Koceja, D.M., Davison, E. and Robertson, C.T. Neuromuscular characteristics of endurance-and power-trained athletes. Research Quarterly for Exercise and Sport.75(1):23-30, 2004.
6. Noakes, T.D. Physiological models to understand exercise fatigue and the adaptations that predict or enhance athletic performance. Scandinavian Journal of Medicine and Science in Sports. 10:123-145, 2000.
7. Paasuke, M., Ereline, J. and Gapeyeva, H. Neuromuscular fatigue during repeated exhaustive submaximal static contractions of knee extensor muscles in endurance-trained, power-trained and untrained men. Acta Physiol Scand. 166:319-326, 1999.
8. Ross, A., Leveritt, M. and Riek, S. Neural influences on sprint running. Training adaptations and acute responses. Sports Med. 31(6):409-425, 2001.
9. Jereb, B. and Strojnik, V. Neuromuscular fatigue after short maximal cycling exercise. Kinesiology. 35(2):135-142, 2003.
10. Glaister, M., Stone, M., Stewart, A.M., Hughes, M. and Moir, G.L. The influence of recovery duration on multiples sprint cycling performance. Journal of Strength and Conditioning Research. 19(4):831-837, 2005.