The aims of this study were to analyse the optimal cadence for peak power production and time to peak power in bicycle motocross (BMX) riders. Six male elite BMX riders volunteered for the study. Each rider completed 3 maximal sprints at a cadence of 80, 100, 120 and 140revs·min -1 on a laboratory Schoberer Rad Messtechnik (SRM) cycle ergometer in isokinetic mode. The riders' mean values for peak power and time of power production in all three tests were recorded. The BMX riders produced peak power (1105± 139W) at 100revs·min -1 with lower peak power produced at 80revs·min -1 (1060± 69W), 120revs·min -1 (1077± 141W) and 140revs·min -1 (1046± 175W).The lowest time of power production was attained at 120revs·min -1 in 2.5± 1.07s.Whilst cadence of 80revs·min -1 (3.5 ± 0.8) 100revs·min -1 (3.00 ± 1.13) and 140revs·min -1 (3.50 ± 0.88) all recorded a higher time of power production. The results indicate that the optimal cadence for producing peak power and reducing the time to peak power is attained at a comparatively low cadence for a cycling sprint event. These findings will both enable riders to select optimal gear ratios and have an impact on training focus.

1Objectives 2 To investigate the influence of BMX helmets and neck braces on translational and 3 rotational accelerations in youth riders. 4 Design 5Mixed model, repeated measure and correlation. 6 Methods 7Twenty three competitive youth BMX riders classified by age group (6-9 yrs, 10-13 yrs 8 and 14-18 yrs) completed 6 laps of an indoor BMX track at race pace, 3 laps without a 9 neck brace (NB) and 3 without brace (WB). A triaxial accelerometer with gyroscope was 10 placed behind the right ear to determine the mean number of accelerations, translational 11 and rotational, of the head between conditions and by age group. 12 Results 13Significant reductions by condition (p = 0.02) and by age (p = 0.04) were found for the 14 number of accelerations, though no interactions (condition x age) were revealed. 15Significant increases by age (p = 0.01) were revealed for translational accelerations, whilst 16 significant increases by condition (p = 0.02) were found for rotational accelerations. In 17 addition, significant correlations were revealed between relative helmet mass and age (r 18 = 0.83; p 0.001) and relative helmet mass and number of accelerations (r = 0.46; p = 0.03). 19 Conclusions 20Accelerations at the head decreased with increased age, possibly due to the influence of 21 greater stabilising musculature. Additionally, neck braces also significantly reduced the 22 number of accelerations. However, the magnitude of accelerations may be influenced by 23 riding dynamics. Therefore, the use of neck braces combined with strength work to 24 2 develop neck strength, could aid in the reduction of head accelerations in youth BMX 25 riders. 26 27

The aim of this study was to ascertain the variation in elite male BMX cyclists' peak power, torque and time of power production during laboratory and fieldbased testing. Eight male elite BMX riders volunteered for the study and each rider completed 3 maximal sprints using both an SRM ergometer in the laboratory, and a portable SRM power meter on an Olympic standard indoor BMX track. The results revealed a significantly higher peak power (p = < 0.001, 34 ± 9 %) and reduced time of power production (p = < 0.001, 105 ± 24 %) in the field tests when compared to laboratory derived values. Torque was also reported to be lower in the laboratory tests, but not to an accepted level of significance (p = 0.182, 6 ± 8 %).These results suggest that field based testing may be a more effective and accurate measure of a BMX rider's peak power, torque and time of power production.

.372, P <0.01.) for both male and female riders respectively. In conclusion, a strong correlation exists between riders position 8-10 s into a race. Therefore, focusing on a riders' ability to gain placings at the start of a race will have an effect on their finish line position.

The aim of this study was to ascertain if gear ratio selection would have an effect on peak power and time to peak power production in elite BMX cyclists. Eight male elite BMX riders volunteered for the study. Each rider performed three, 10 second maximal sprints on an Olympic standard indoor BMX track. The riders' bicycles were fitted with a portable SRM power meter. Each rider performed the three sprints using gear ratios of 41/16, 43/16, 45/16 tooth. The results from the 41/16 and 45/16 gear ratios were compared to the current standard 43/16 gear ratio. Statistically significant differences were found between the gear ratios for peak power (F(2,14) = 6.448; p = 0.010) and peak torque (F(2,14) = 4.777; p = 0.026), but no significant difference was found for time to peak power (F (2,14) = 0.200; p = 0.821). When comparing gear ratios, the results showed a 45/16 gear ratio elicited the highest peak power,1658 ± 221 W, compared to 1436 ± 129 W and 1380 ± 56 W, for the 43/16 and 41/16 ratios, respectively. The time to peak power showed a 41/16 tooth gear ratio attained peak power in -0.01 s and a 45/16 in 0.22 s compared to the 43/16. The findings of this study suggest that gear ratio choice has a significant effect on peak power production, though time to peak power output is not significantly affected. Therefore, selecting a higher gear ratio results in riders attaining higher power outputs without reducing their start time.