Metabolic Field Measurements – Repeated-sprint Ability

Introduction: In most countries, the sports with the highest levels of participation and popularity are team sports (e.g., soccer, rugby and hockey). As a result, there have been many time-motion analyses conducted on these sports. Subsequently, a number of tests have been designed which propose to replicate the demands of team sports and aim to assess important fitness characteristics of team-sport athletes6. However, although average time-motion analysis data provides valuable information on the over-all physiological demands of team sports, it provides only a limited insight into the physiology of ‘repeated-sprint ability’. Indeed, consistent with other reports, we have recently shown that on average, elite field-hockey players perform a sprint every 2 minutes7. However, on a number of occasions during a game, players are required to perform a ‘repeated-sprint’ bout (defined as a minimum of three sprints, with mean recovery duration between sprints < 21 s). Based on these and other observations, our laboratory has been utilising a RSA test consisting of 5, all-out 6-s sprints every 30 s to assess this important fitness component.

Validity and reliability: The RSA test is both a valid and reliable test of repeated-sprint ability. There is a strong correlation between repeated-sprint performance on the cycle and when running1. In our laboratory, the co-efficient of variation for this test is 3.9% and 3.7% for peak power and total work respectively.

Metabolic Measurements: Two important determinants of RSA may be the ability to resynthesise PCr stores4 and to buffer hydrogen ions (H+)3. While both of these measurements require the use of invasive muscle biopsies, field measurements may provide an indication of these qualities. In particular, we have shown that change in plasma [H+] is related to change in muscle [H+] following the RSA test. An important finding of this study was that the relationship was significant when the blood samples were taken 5 min, but not immediately, following the RSA test. As PCr resynthesis occurs primarily by oxidative processes, various tests of aerobic fitness may also be useful to give an indication of the ability to resynthesise PCr stores. However, it is important to note that the association between aerobic fitness and repeated-sprint ability is greater in untrained subjects3 than elite team-sport athletes (Australian Women’s hockey team)2.

Strength and power: We have recently shown that peak power output (Pmax) (measured during a jump squat against a load equivalent to 30% 1RM) is related to both single-sprint performance and repeated-sprint performance5. An additional interesting finding from this study was the strong correlation between Pmax on the jump squat and peak power output during the RSA test (r=0.72; P<0.0001). This suggests that that the RSA test may also be used to provide an indication of the strength and power of team-sport athletes.

Future research: On average, 95% of the recovery during repeated-sprint bouts in a field-hockey match is of an active nature7. This suggests that it may be important to incorporate active recovery into future RSA tests. We are also currently investigating the validity and reliability of a running-based RSA test.

References
1.Bishop D. et al.(2001) Journal of Science and Medicine in Sport. 4(1): 19-29
2.Bishop, D. et al. (2003) Journal of Science and Medicine in Sport. 6(2): 199-209.
3.Bishop, D. et al. (2004) European Journal of Applied Physiology. (Accepted).
4.Bogdanis, G.C. et al. (1996). J Appl Physiol. 80(3): 876-884
5.Edge, J. et al. (2004). European Congress of Sport Science, Claremont-Ferrand
6.Nicholas, C. W. et al. (1995). Journal of Sport Sciences. 13:283-290.
7.Spencer, M. et al. (2004). Journal of Sport Sciences. (In Press).

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