Exposure to impacts and vibrations has been shown to be detrimental to cross country mountain bike performance and health. Therefore, any strategy aimed at attenuating such exposure is useful to participants and/or industry. The purpose of this study was to assess the influence of tyre size and tyre inflation pressure on exposure to impacts. Participants completed nine trials of a technical section (controlled for initial speed and route taken) including nine separate conditions involving three tyre sizes and three tyre inflation pressures normalised per tyre. Performance was determined by time to negotiate the technical section while triaxial accelerometers recorded accelerations (128 Hz) to quantify impact exposure and the subsequent effects on soft tissue response. Increases in tyre size within the range used improved performanceP<0.0001while changes to tyre inflation pressure had no effectP=0.6870on performance. Larger tyre sizes and lower tyre inflation pressures significantlyP<0.0001reduced exposure to impacts which could be augmented or negated due to an interaction between tyre size and inflation pressureP<0.0001. It is recommended that mountain bikers use larger tyres, inflated to the moderate pressures used within this study, in order to increase performance and reduce the risk of overuse injuries.

Brief ReportPage 174 ABSTRACTThe aim of this brief study was to establish the efficacy of waist depth water Aquatic treadmill (ATM) running during a 28-day injury period where normal land based training was not possible. Synchronized tri-axial accelerometers were used to identify running dynamics while expired air and heart rate were sampled on a breath-by-breath basis for physiological variable collection throughout a 15-minute sub-maximal constant speed trial performed pre-injury, 28-days following initial injury (ATM training), and a further 10-days following a return to normal land based training. Water treadmill running altered spatio-temporal parameters that positively enhanced measures of running efficiency while reducing stress on the passive structures of the lower limbs. On cessation of ATM spatio-temporal parameters returned to normal while running efficiency remained greater than pre-injury values. As such, if water treadmill running does not hamper the rehabilitation process or negatively alter running technique it is a useful means of maintaining fitness following injury.