RESUMEN
OBJECTIVES: To investigate the influence of BMX helmets and neck braces on translational and rotational accelerations in youth riders. DESIGN: Mixed model, repeated measure and correlation. METHODS: Twenty three competitive youth BMX riders classified by age group (6-9 years, 10-13 years and 14-18 years) completed 6 laps of an indoor BMX track at race pace, 3 laps without a neck brace (NB) and 3 without brace (WB). A triaxial accelerometer with gyroscope was placed behind the right ear to determine the mean number of accelerations, translational and rotational, of the head between conditions and by age group. RESULTS: Significant reductions by condition (p=0.02) and by age (p=0.04) were found for the number of accelerations, though no interactions (condition×age) were revealed. Significant increases by age (p=0.01) were revealed for translational accelerations, whilst significant increases by condition (p=0.02) were found for rotational accelerations. In addition, significant correlations were revealed between relative helmet mass and age (r=0.83; p=0.001) and relative helmet mass and number of accelerations (r=0.46; p=0.03). CONCLUSIONS: Accelerations at the head decreased with increased age, possibly due to the influence of greater stabilising musculature. Additionally, neck braces also significantly reduced the number of accelerations. However, the magnitude of accelerations may be influenced by riding dynamics. Therefore, the use of neck braces combined with strength work to develop neck strength, could aid in the reduction of head accelerations in youth BMX riders.
Asunto(s)
Aceleración/efectos adversos , Ciclismo/lesiones , Tirantes , Vértebras Cervicales/fisiología , Fuerza Muscular/fisiología , Traumatismos del Cuello/prevención & control , Acelerometría , Adolescente , Estudios de Casos y Controles , Niño , Dispositivos de Protección de la Cabeza/efectos adversos , Humanos , Rango del Movimiento Articular/fisiología , Rotación/efectos adversos , Dispositivos Electrónicos VestiblesRESUMEN
Rylands, LP, Hurst, HT, Roberts, SJ, and Graydon, RW. The effect of "pumping" and "nonpumping" techniques on velocity production and muscle activity during field-based BMX cycling. J Strength Cond Res 31(2): 445-450, 2017-The aim of the current study was to determine if a technique called "pumping" had a significant effect on velocity production in Bicycle Motocross (BMX) cycling. Ten National standard male BMX riders fitted with surface electromyography (sEMG) sensors completed a timed lap of an indoor BMX track using the technique of pumping, and a lap without pumping. The lap times were recorded for both trials and their surface sEMG was recorded to ascertain any variation in muscle activation of the biceps brachii, triceps brachii, vastus lateralis, and medial gastrocnemius. The findings revealed no significant differences between any of muscle groups (p > 0.05). However, significant differences (p < 0.001) were observed between the pumping and nonpumping trials for both mean lap velocity (42 ± 1.8 km·h, 33 ± 2.9 km·h, respectively) and lap times (43.3 ± 3.1 seconds, 34.7 ± 1.49 seconds, respectively). The lap times recorded for the pumping trials were 19.50 ± 4.25% lower than the nonpumping, whereas velocity production was 21.81 ± 5.31% greater in the pumping trial compared with the nonpumping trial. The technique of pumping contributed significantly to velocity production, although not at the cost of additional muscle activity. From a physiological and technical perspective, coaches and riders should prioritize this technique when devising training regimes.
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Ciclismo/fisiología , Músculo Esquelético/fisiología , Adulto , Electromiografía , Humanos , Masculino , Fenómenos Fisiológicos Musculoesqueléticos , Músculo Cuádriceps/fisiología , Adulto JovenRESUMEN
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 140 revs · 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 3 tests were recorded. The BMX riders produced peak power (1105 ± 139 W) at 100 revs · min-1 with lower peak power produced at 80 revs · min-1 (1060 ± 69 W, (F(2,15) = 3.162; P = .266; η2 = 0.960), 120 revs · min-1 (1077 ± 141 W, (F(2,15) = 4.348; P = .203; η2 = 0.970) and 140 revs · min-1 (1046 ± 175 W, (F(2,15) = 12.350; P = 0.077; η2 = 0.989). The shortest time to power production was attained at 120 revs · min-1 in 2.5 ± 1.07 s. Whilst a cadence of 80 revs · min-1 (3.5 ± 0.8 s, (F(2,15) = 2.667; P = .284; η2 = 0.800) 100 revs · min-1 (3.00 ± 1.13 s, (F(2,15) = 24.832; P = .039; η2 = 0.974) and 140 revs · min-1 (3.50 ± 0.88 s, (F(2,15) = 44.167; P = .006; η2 = 0.967)) all recorded a longer time to peak power production. The results indicate that the optimal cadence for producing peak power output and reducing the time to peak power output are attained at comparatively low cadences for sprint cycling events. These findings could potentially inform strength and conditioning training to maximise dynamic force production and enable coaches to select optimal gear ratios.
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Rendimiento Atlético/fisiología , Ciclismo/fisiología , Fenómenos Biomecánicos , Humanos , Masculino , Análisis y Desempeño de Tareas , Factores de Tiempo , Adulto JovenRESUMEN
This study aimed to investigate the influence of different mountain bike wheel diameters on muscle activity and whether larger diameter wheels attenuate muscle vibrations during cross-country riding. Nine male competitive mountain bikers (age 34.7 ± 10.7 years; stature 177.7 ± 5.6 cm; body mass 73.2 ± 8.6 kg) participated in the study. Riders performed one lap at race pace on 26, 27.5 and 29 inch wheeled mountain bikes. sEMG and acceleration (RMS) were recorded for the full lap and during ascent and descent phases at the gastrocnemius, vastus lateralis, biceps brachii and triceps brachii. No significant main effects were found by wheel size for each of the four muscle groups for sEMG or acceleration during the full lap and for ascent and descent (P > .05). When data were analysed between muscle groups, significant differences were found between biceps brachii and triceps brachii (P < .05) for all wheel sizes and all phases of the lap with the exception of for the 26 inch wheel during the descent. Findings suggest wheel diameter has no influence on muscle activity and vibration during mountain biking. However, more activity was observed in the biceps brachii during 26 inch wheel descending. This is possibly due to an increased need to manoeuvre the front wheel over obstacles.
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Aceleración , Ciclismo/fisiología , Músculo Esquelético/fisiología , Equipo Deportivo , Vibración , Adulto , Electromiografía , Diseño de Equipo , Humanos , Extremidad Inferior/fisiología , Masculino , Extremidad Superior/fisiologíaRESUMEN
The purpose of this study was to determine the influence of different wheel size diameters on indicators of cross-country mountain bike time trial performance. Nine competitive male mountain bikers (age 34.7 ± 10.7 years; stature 177.7 ± 5.6 cm; body mass 73.2 ± 8.6 kg) performed 1 lap of a 3.48 km mountain bike (MTB) course as fast as possible on 26â³, 27.5â³ and 29â³ wheeled MTB. Time (s), mean power (W), cadence (revs · min-1) and velocity (km · h-1) were recorded for the whole lap and during ascent and descent sections. One-way repeated measure ANOVA was used to determine significant differences. Results revealed no significant main effects for any variables by wheel size during all trials, with the exception of cadence during the descent (F(2, 16) = 8.96; P = .002; P2 = .53). Post hoc comparisons revealed differences lay between the 26â³ and 29â³ wheels (P = .02). The findings indicate that wheel size does not significantly influence performance during cross-country when ridden by trained mountain bikers, and that wheel choice is likely due to personal choice or sponsorship commitments.
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Rendimiento Atlético/fisiología , Ciclismo/fisiología , Equipo Deportivo , Adulto , Índice de Masa Corporal , Diseño de Equipo , Humanos , MasculinoRESUMEN
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 Bicycle Motocross (BMX) cyclists. Eight male elite BMX riders volunteered for the study. Each rider performed three, 10-s 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 and 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 = .010) and peak torque (F(2,14) = 4.777; p = .026), but no significant difference was found for time to peak power (F(2,14) = 0.200; p = .821). When comparing gear ratios, the results showed a 45/16 gear ratio elicited the highest peak power,1658 ± 221â W, compared to 1436 ± 129â W and 1380 ± 56â 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 -0.01â s and a 45/16 in 0.22â 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.
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Rendimiento Atlético/fisiología , Ciclismo/fisiología , Fenómenos Biomecánicos/fisiología , Adulto , Humanos , Masculino , Factores de Tiempo , Torque , Adulto JovenRESUMEN
The aim of this study was to ascertain the variation in elite male bicycle motocross (BMX) cyclists' peak power, torque, and time of power production during laboratory and field-based testing. Eight elite male BMX riders volunteered for the study, and each rider completed 3 maximal sprints using both a Schoberer Rad Messtechnik (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 with 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.