Citation

Macdermid PW, Stannard S. J. Sports Sci. 2012; 30(14): 1491-1501.

Copyright

(Copyright © 2012, Informa - Taylor and Francis Group)

DOI

10.1080/02640414.2012.711487

PMID

unavailable

Abstract

The purpose was to assess the mechanical work and physiological responses to cross country mountain bike racing. Participants (n = 7) cycled on a cross country track at race speed whilst (V) over dotO(2), power, cadence, speed, and geographical position were recorded. Mean power during the designated start section (68.5 +/- 5.5 s) was 481 +/- 122 W, incurring an O-2 deficit of 1.58 +/- 0.67 L - min(-1) highlighting a significant initial anaerobic (32.4 +/- 10.2%) contribution. Complete lap data produced mean (243 +/- 12 W) and normalised (279 +/- 15 W) power outputs with 13.3 +/- 6.1 and 20.7 +/- 8.3% of time spent in high force-high velocity and high force-low velocity, respectively. This equated to, physiological measures for %(V) over dotO(2max) (77 +/- 5%) and % HRmax (93 +/- 2%). Terrain (uphill vs downhill) significantly (P < 0.05) influenced power output (70.9 +/- 7.5 vs 41.0 +/- 9.2% W-max), the distribution of low velocity force production, VO2 (80 +/- 1.7 vs 72 +/- 3.7%) and cadence (76 + 2 vs 55 +/- 4 rpm) but not heart rate (93.8 +/- 2.3 vs 91.3 +/- 0.6% HRmax) and led to a significant difference between anaerobic contribution and terrain (uphill, 6.4 +/- 3.0 vs downhill, 3.2 +/- 1.8%, respectively) but not aerobic energy contribution. Both power and cadence were highly variable through all sections resulting in one power surge every 32 s and a supra-maximal effort every 106 s. The results show that cross country mountain bike racing consists of predominantly low velocity pedalling with a large high force component and when combined with a high oscillating work rate, necessitates high aerobic energy provision, with intermittent anaerobic contribution. Additional physical stress during downhill sections affords less recovery emphasised by physiological variables remaining high throughout.

Language: en