No 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 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.

The ability to quantify power within the sport of slalom kayaking would provide coaches and athletes objective data to monitor performance. This study determined the validity of a kayak paddle power meter and subsequent relationship between work rate and stroke kinetics. One participant completed multiple trials of a flat-water, straight-line sprint and a sequence of slalom gates at numerous intensities to attain the velocity:power relationship. Laboratory results identified the kayak paddles’ strain gauges were valid and reliable, and field tests presented a cubic relationship for power as a function of velocity in the straight-line sprint (R 2 =0.982) and the slalom-specific test (R 2 =0.993). Further analysis of stroke kinetics identified velocity of hand movement at individual peak force capability to be critical in the highest work rates achieved for both slalom and flat-water sprinting. It was concluded that the kayak paddle power meter tested is a valid means of recording work rate and stroke kinetics during kayaking in the field.

This study compared a training diet recommended for endurance athletes (H-CHO) with an isoenergetic high protein (whey supplemented), moderate carbohydrate (H-Pro) diet on endurance cycling performance. Over two separate 7-d periods subjects (n = 7) ingested either H-CHO (7.9 +/- 1.9 g x kg(-1) x d(-1) carbohydrate; 1.2 +/- 0.3 g x kg(-1) x d(-1) fat; 1.3 +/- 0.4 g x kg(-1) x d(-1) protein) or H-Pro (4.9 +/- 1.8 g x kg(-1) x d(-1); 1.3 +/- 0.3 g x kg(-1) x d(-1); 3.3 +/- 0.4 g x kg(-1) x d(-1)) diet in a randomized, balanced order. On day 8 subjects cycled (self-paced) for a body weight dependent (60 kJ/bm) amount of work. No differences occurred between energy intake (P = 0.422) or fat intake (P = 0.390) during the two dietary conditions. Performance was significantly (P = 0.010) impaired following H-Pro (153 +/- 36) compared with H-CHO (127 +/- 34 min). No differences between treatments were observed for physiological measures taken during the performance trials. These results indicate an ergolytic effect of a 7-d high protein diet on self-paced endurance cycling performance.

No abstract

For any athlete competing at the highest level it is vital to understand the components that lead to successful performance. World cup cross-country mountain biking is a complex sport involving large numbers of athletes (100-200) competing for positional advantage over varied off-road terrain. The start has been deemed a major part of performance outcome in such races. The purpose of the present study was to establish the relationship between start and finish position in cross-country mountain bike World Cup events over a 10 year (1997-2007) period and to make comparisons with a model manipulating start position based on predicted athletic capabilities. Data collection and comparisons included results from World Cup events from 1997 to 2007 (males and females), and modelled race data based on potential performance capabilities over the same period. Analyses involved the association of annual plus pooled start and finish position (Kendall's tau) along with banded mean, standard deviation for number of changes in position, while non-constrained linear regression enabled comparison between seasons. Actual race data showed significant positive correlations between starting position and finishing position (P < 0.01) in all cases but less than the model. A mean 57.4% (s = 5.6) of males changed < 15 positions, while 62.9% (s = 9.1) of females changed < 10 positions compared with modelled data (83.6%, s = 0.8 and 91.6%, s = 1.5 for males and females respectively). Individual season comparisons show general patterns to be identical (P > 0.05) for both males and females. In conclusion, finishing position is highly dependent on start position and strategies need to be devised for competing athletes to progress in the sport.

The purpose of this investigation was to compare the effects of vibrations experienced during off-road and road cycling. It was hypothesised that additional damping will be expressed through a greater work demand and increased physiological markers when travelling at the same speed over an identical terrain profile. Participants ascended a tar-sealed road climb and a single-track off-road climb at a predetermined speed. Time, speed, power, cadence, heart rate and V̇ O2 were sampled and logged every second while tri-axial accelerometers recorded accelerations (128 Hz) to quantify vibrations experienced. Statistical analysis indicated accelerations to be greater during the off-road condition (p<0.0001) with post-hoc analysis exposing differences (p<0.001) for handlebar, arm, leg and seat post but not the lower back or head. The increased accelerations during off-road riding are associated with the increased vibrations and rolling resistance experienced. This led to increases in the work done (road: 280±69 vs. off-road: 312±74 W, p=0.0003) and, consequentially, a significant increase in the physiological markers V̇ O2 (road: 48.5±7.5 off-road 51.4±7.3 ml·kg(-1)·min(-1), p=0.0033) and heart rate (road: 161±10 off-road 170±10 bpm, p=0.0001) during the off-road condition. Such physiological differences and their causes are important to understand in order to provide suitable training recommendations or technological interventions for improving competitive performance or recreational enjoyment.

The aim of this study was to determine the differential effects of three commonly used crank lengths (170, 172.5 and 175 mm) on performance measures relevant to female cross-country mountain bike athletes (n = 7) of similar stature. All trials were performed in a single blind and balanced order with a 5- to 7-day period between trials. Both saddle height and fore-aft position to pedal axle distance at a crank angle of 90 degrees was controlled across all trials. The laboratory tests comprised a supra-maximal (peak power-cadence); an isokinetic (50 rpm) test; and a maximal test of aerobic capacity. The time to reach supra-maximal peak power was significantly (P < 0.05) shorter in the 170 mm (2.57 +/- 0.79 s) condition compared to 175 mm (3.29 +/- 0.76 s). This effect represented a mean performance advantage of 27.8% for 170 mm compared to 175 mm. There was no further inter-condition differences between performance outcome measurements derived for the isokinetic (50 rpm) maximum power output, isokinetic (50 rpm) mean power output or indices of endurance performance. The decreased time to peak power with the greater rate of power development in the 170 mm condition suggests a race advantage may be achieved using a shorter crank length than commonly observed. Additionally, there was no impediment to either power output produced at low cadences or indices of endurance performance using the shorter crank length and the advantage of being able to respond quickly to a change in terrain could be of strategic importance to elite athletes.