Influence of wheel size on muscle activity and tri-axial accelerations during cross-country mountain biking.

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.

The effect of mountain bike wheel size on cross-country performance.

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 26″, 27.5″ and 29″ 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 26″ and 29″ 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.

Eating Disorders and Disordered Eating in Competitive Cycling: A Scoping Review.

This article reports on the findings from a scoping review on eating disorders and disordered eating in competitive cycling. The review was informed by a scoping review methodological framework as well as the Preferred Reporting Items for Systematic Reviews and Meta-analysis extension for scoping reviews (PRISMA-ScR) reporting guidelines. PubMed, SPORTDiscus and Web of Science were used to identify relevant literature for review. Fourteen studies met the eligibility criteria and were included in the full review. A narrative synthesis was used to summarise the main findings and themes across the included literature. Findings from the review are presented under the following themes: cycling as an 'at-risk' discipline; power to weight ratio; energy requirements and risk of low energy availability; the social environment of cycling; nutrition support provision; relationship between eating disorders/disordered eating and exercise addiction; and recommendations made in identified literature. Overall, the literature suggests competitive cycling is a sport with a high prevalence of disordered eating and/or eating disorders and a sport with unique risk factors that contribute to this. Crucially, more research is needed in this area. The article concludes with the gaps in the literature highlighted, implications for future research, and applications to policy and practice suggested.

An Investigation into Helmet Use, Perceptions of Sports-Related Concussion, and Seeking Medical Care for Head Injury amongst Competitive Cyclists.

The purpose of this study was to investigate competitive cyclists' helmet use, perceptions of sports-related concussion (SRC), and medical-care-seeking behaviors. A mixed-method approach was used with qualitative and quantitative data presented. The study comprised of a cross-sectional analysis of 405 competitive cyclists who completed an online survey. Results indicated that most participants believed a bicycle helmet protects against SRC (79.5%) and considerable numbers of participants would not seek medical care for potential head injury in scenarios where this would be recommended. It was also discovered that marketing of concussion reduction technology influences cyclists' helmet-purchasing behaviors. With the data presented, it is recommended that governing bodies in cycling need to develop educational resources to address gaps in knowledge regarding SRC amongst cyclists. We also suggest that more independent research on concussion reduction technologies in bicycle helmets is needed, with advertising supported by clear scientific evidence to avoid negatively influencing head injury management and reporting behaviors amongst cyclists.

The influence of different footwear on 3-D kinematics and muscle activation during the barbell back squat in males.

The barbell back squat is commonly used by athletes participating in resistance training. The barbell squat is typically performed using standard athletic shoes, or specially designed weightlifting footwear, although there are now a large number of athletes who prefer to squat barefoot or in barefoot-inspired footwear. This study aimed to determine how these footwear influence 3-D kinematics and muscle activation potentials during the barbell back squat. Fourteen experienced male participants completed squats at 70% 1 rep max in each footwear condition. 3-D kinematics from the torso, hip, knee and ankle were measured using an eight-camera motion analysis system. In addition, electromyographical (EMG) measurements were obtained from the rectus femoris, tibialis anterior, gastrocnemius, erector spinae and biceps femoris muscles. EMG parameters and joint kinematics were compared between footwear using repeated-measures analyses of variance. Participants were also asked to subjectively rate which footwear they preferred when performing their squat lifts; this was examined a chi-squared test. The kinematic analysis indicated that, in comparison to barefoot the running shoe was associated with increased squat depth, knee flexion and rectus femoris activation. The chi-squared test was significant and showed that participants preferred to squat barefoot. This study supports anecdotal evidence of athletes who prefer to train barefoot or in barefoot-inspired footwear although no biomechanical evidence was found to support this notion.

The Reliability of Electromyographic Normalization Methods for Cycling Analyses.

Electromyography (EMG) is normalized in relation to a reference maximum voluntary contraction (MVC) value. Different normalization techniques are available but the most reliable method for cycling movements is unknown. This study investigated the reliability of different normalization techniques for cycling analyses. Twenty-five male cyclists (age 24.13 ± 2.79 years, body height 176.22 ± 4.87 cm and body mass 67.23 ± 4.19 kg, BMI = 21.70 ± 2.60 kg·m-1) performed different normalization procedures on two occasions, within the same testing session. The rectus femoris, biceps femoris, gastrocnemius and tibialis anterior muscles were examined. Participants performed isometric normalizations (IMVC) using an isokinetic dynamometer. Five minutes of submaximal cycling (180 W) were also undertaken, allowing the mean (DMA) and peak (PDA) activation from each muscle to serve as reference values. Finally, a 10 s cycling sprint (MxDA) trial was undertaken and the highest activation from each muscle was used as the reference value. Differences between reference EMG amplitude, as a function of normalization technique and time, were examined using repeated measures ANOVAs. The test-retest reliability of each technique was also examined using linear regression, intraclass correlations and Cronbach's alpha. The results showed that EMG amplitude differed significantly between normalization techniques for all muscles, with the IMVC and MxDA methods demonstrating the highest amplitudes. The highest levels of reliability were observed for the PDA technique for all muscles; therefore, our results support the utilization of this method for cycling analyses.

The effect of different durations of carbohydrate mouth rinse on cycling performance.

Carbohydrate (CHO) mouth rinse has been shown to improve time trial performance. Although the exact mechanism remains un-established, research postulates that there are oral cavity receptors which increase neural drive. Increasing the duration of the mouth rinse could potentially increase stimulation of these receptors. The aim of the current investigation was to determine whether the duration of mouth rinse with 6.4% CHO affected 30-min self-selected cycling performance. Eleven male participants (age =24.1±3.9 years) performed three 30-min self-paced trials. On one occasion water was given as a mouth rinse for 5 s without being ingested placebo (PLA), on the other two occasions a 6.4% CHO solution was given for 5 and 10 s. Distance cycled, heart rate, ratings of perceived exertion, cadence, speed and power were recorded throughout all trials. The main findings were that distance cycled during the 10-s mouth rinse trial (20.4±2.3 km) was significantly greater compared to the PLA trial (19.2±2.2 km; P<0.01). There was no difference between the 5- and 10-s trials (P=0.15). However, 10 out of 11 participants cycled further during the 5-s trial compared to PLA, and eight cycled further during the 10-s trial compared to the 5 s. In conclusion, although there was an improvement in distance cycled with the 5-s mouth rinse compared to the PLA it was only significant with 10 s suggesting a dose response to the duration of mouth rinse.

Power output of field-based downhill mountain biking.

The purpose of this study was to assess the power output of field-based downhill mountain biking. Seventeen trained male downhill cyclists (age 27.1 +/- 5.1 years) competing nationally performed two timed runs of a measured downhill course. An SRM powermeter was used to simultaneously record power, cadence, and speed. Values were sampled at 1-s intervals. Heart rates were recorded at 5-s intervals using a Polar S710 heart rate monitor. Peak and mean power output were 834 +/- 129 W and 75 +/- 26 W respectively. Mean power accounted for only 9% of peak values. Paradoxically, mean heart rate was 168 +/- 9 beats x min(-1) (89% of age-predicted maximum heart rate). Mean cadence (27 +/- 5 rev x min(-1)) was significantly related to speed (r = 0.51; P < 0.01). Analysis revealed an average of 38 pedal actions per run, with average pedalling periods of 5 s. Power and cadence were not significantly related to run time or any other variable. Our results support the intermittent nature of downhill mountain biking. The poor relationships between power and run time and between cadence and run time suggest they are not essential pre-requisites to downhill mountain biking performance and indicate the importance of riding dynamics to overall performance.