Massey University, School of Sport and Exercise, Palmerston North, New Zealand.
J Sports Sci. 2012;30(14):1491-501. doi: 10.1080/02640414.2012.711487. Epub 2012 Aug 10.
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 VO2, 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 O2 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 %VO(2max) (77 ± 5%) and % HR(max) (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% HR(max)) 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.
本研究旨在评估越野山地自行车比赛中的机械功和生理反应。参与者（n=7）以比赛速度在越野赛道上骑行，同时记录 VO2、功率、踏频、速度和地理位置。指定起始段（68.5±5.5s）的平均功率为 481±122W，导致 O2 亏损 1.58±0.67L-min(-1)，表明初始无氧（32.4±10.2%）贡献显著。完整的圈速数据产生平均（243±12W）和归一化（279±15W）功率输出，分别有 13.3±6.1%和 20.7±8.3%的时间处于高力量-高速度和高力量-低速度区间。这相当于，生理测量的 %VO(2max)（77±5%）和 % HR(max)（93±2%）。地形（上坡与下坡）显著（P<0.05）影响功率输出（70.9±7.5 与 41.0±9.2%W(max)）、低速度力产生的分布、VO2（80±1.7 与 72±3.7%）和踏频（76+2 与 55±4rpm），但不影响心率（93.8±2.3 与 91.3±0.6%HR(max)），导致无氧贡献与地形（上坡 6.4±3.0%与下坡 3.2±1.8%）之间存在显著差异，但有氧能量贡献没有差异。整个比赛中，功率和踏频都有很高的变异性，导致每 32s 出现一次功率激增，每 106s 出现一次超最大努力。结果表明，越野山地自行车比赛主要由低速度踩踏组成，具有较大的高力量成分，当与高摆动工作率结合时，需要高有氧能量供应，间歇性无氧贡献。下坡段的额外物理压力导致生理变量在整个比赛中保持较高水平，恢复时间较少。
