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Field and laboratory correlates of performance in competitive cross-country mountain bikers. Prins, L., Terblanche, E. & Myburg, K.H. Journal of Sport Science, June 2007; 25 (8) 927-935 The amount of research on the physiological responses to mountain biking is relatively small, only handful of studies have been conducted. Mountain biking (MTB)is different from road cycling in many ways. The intensity of cross country racing is high, similar to time trial event, but much higher than a typical road race. The riding style is also different due to the different terrain. Because of these differences laboratory tests used to predict performance in road cyclist would not be particularly revealing for a mountain biker. The purpose of this study was to design and evaluate a laboratory test to simulate cross country mountain bike performance and to compare the predictive power of variables from common laboratory tests as well as the new non traditional test, and finally to determine what test is most relevant to mountain bikers. Methods Eight competitive male cross-country mountain bikes participated in an outdoor mountain bike competition. Within four weeks of the competition they then completed four laboratory test and an outdoor time trail. The laboratory test included: 1) an incremental exercise test to determine VO2max and peak power output 2) A 1-km time trail performance in a fresh condition (TT0) 3) A variable fixed intensity bout lasting 26 minutes and followed immediately by a 1-km time trial (TT1) 4) A variable fixed intensity test consisting of two consecutive bouts each lasting 26 minutes and followed immediately by a 1-km time trial (TT2) The 1-km time trial is an all sprint that lasts approximately 90s and was supposed to represent the frequent sustained burst of power seen in MTB. The later two tests represent included a pre-fatiguing protocol that may better simulate MTB racing than 1-km time trial alone. The testing was conducted on separate days with a maximum of 7 days between tests. Peak power, VO2max, Power at lactate threshold , Results. Average relative VO2max, peak power, and relative peak power for the MTB riders was 63.6 + 5.7 ml/O2/min, 372 + 37 watts, and 5.1 + 0.0 watts/kg respectively. The average time for TT0, TT1, and TT2 were 83.4+5.2s, 88+5.7s, and 87.4+5.4s respectively. Of the variables studied, the best correlate with outdoor performance and the outdoor time trial was relative peak power (r=-.83) Conclusion Despite the authors attempt to create a test that closely simulated the cross-country MTB event the best predictor of race performance was the traditional graded exercise test to measure VO2 max. The peak power at the end of test corrected for body weight was the best predictor of performance of the variables studied. This study does have some limitations in that the sample size is small. With only eight subjects it is hard to expand these finding to other populations as well. But this finding is consistent with other research done on runners and road cyclist, where peak speed and peak power were excellent predictors of performance l. This data may be useful for anyone whishing to compete in MTB racing, were is it seems that inorder to be competitive, at least at the regional level , a relative peak power of 5.1+ watts/kg would be necessary. And just for the sake of comparison, international caliber road cyclists have a relative peak power of 7.1 watts/kg.
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The effect of consecutive days of exercise on markers of oxidative stress. Shing, CM, Peake, JM, Ahern, SM, Strobet, NA, Wilson, G, Jenkins, DG, and Coombes, JS. Appl. Physiol Nutr. Metab. 32:677-685 (2007) Exercise is known to produce free radicals and reactive oxygen species (ROS). ROS have been linked to lipid peroxidation of cell membranes and tissue inflammation, muscle fatigue, and impaired recovery. Most of the research up to date has investigated the oxidative stress in response to acute exercise. The purpose of the present study was to determine the effect of three consecutive days of intense aerobic and anaerobic exercise on markers of oxidative stress and antioxidant status
The subjects of this study were eight highly trained road cyclists with a VO2max of 76 + 4 ml/kg/min. The subjects underwent a maximal graded exercise test to determine peak power output. On day one the subjects performed interval training that included nine 30s bouts at 150% of peak power with 4.5 minutes of low intensity exercise during recovery. On days two and three the subjects performed 30K time trials on a stationary wind trainer. Five days after the second time trail, subjects performed a submaximal ride on a wind trainer that resulted in an equal amount of total oxygen consumed compared to the interval training session. Urine and blood were collected before and after each exercise session to measure markers of oxidative stress and antioxidant enzyme activity.
The results of this study indicated that oxidative stress was apparent following the initial day of intense exercise, as was to be expected. However, there was no accumulative effect during successive days of high intensity exercise. Furthermore, the authors found that Total Antioxidant Status was elevated for 24 hours following the interval training session that may have offered some protection against subsequent bouts of activity. The author noted that antioxidant defense systems were not depleted during the three days of high intensity exercise and highly trained cyclist appear to have robust antioxidant defense systems against consecutive days of intense exercise.
This study supports the notion that exercise provides protection against free radical activity. The subjects in this study were highly trained; we may not see such an effect in untrained subjects. Noting that the antioxidant systems were not depleted and antioxidant activity remained elevated through the study, it begs the question is antioxidant dietary supplementation necessary, would it provide added protection? |
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Denadal, B., Ortiz, M., Greco, C., and Meilo, M. (2006). Interval training at 95% and 100% of the velocity at VO2max: effects on aerobic physiological indexes and running performance. Applied Physiology, Nutrition, and Metabolism. 31: 737 – 743. This study analyzed the effects of two different high intensity interval training (HIT) programs on physiological indicators and running performance in well trained athletes. It has been established previously that in well trained endurance athletes, HIT training is necessary to improve performance i.e. cycling power or running speed and VO2max. It was established that the training intensity that caused the greatest improvement was the running velocity or cycling power at VO2max. This study compared the effects of the interval training conducted at the running velocity that corresponded with 100% VO2max versus 95% VO2max. The subjects of this study were well trained, but not considered elite (VO2max = 59 +6.0 ml/kg/min). The subjects trained for a period of four weeks, each week included one session at the lactate threshold, three continuous submaximal sessions, and two interval training sessions at their designated intensity. At the end of four weeks, both groups had significantly increased their lactate threshold, and 5K running time. But only the group that trained at the velocity that corresponded to 100%VO2max increased their VO2max and increased 1.5K time. The results of this study are important for a number of reasons. First, it is commonly believed that VO2max cannot be increased in well trained athletes. This study and others indicate that VO2max can be improved but only when training is conducted at an intensity (speed or power) that corresponds with VO2max. Second, even training a running speed 0.5 mph slower does produce the same results. However, HIT increases the risk of injury and overtraining, it is important for this type of training to be incorporated carefully into a periodized program and monitored by a professional coach or trainer The bottom line is: to maximize results, even in non-elite athletes, physiological assessment of performance is necessary. The only way that VO2max and lactate threshold can be measured accurately/precisely is in the laboratory setting. Field tests are good for monitoring progress, and are good for predicting performance, but do not correlate well with true power or running velocity which is necessary to produce the results seen in this study.
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