Shock attenuation, spatio-temporal and physiological parameter comparisons between land treadmill and water treadmill running

Purpose: The purpose of this study was to compare shock attenuation, spatio-temporal and physiological parameters during water immersed(depth: anterior superior iliac spine) aquatic treadmill(ATM) running and land based treadmill(LTM) running matched for speed.Methods: Six participants completed 15 min running under 2 conditions(LTM and ATM) in a randomised and balanced order, matched for speed.Synchronised tri-axial accelerometers placed at the distal tibia, lumbar region, and forehead were used to identify running dynamics and measure acceleration on impact and its attenuation. Expired respiratory gases and heart rate were sampled on a breath-by-breath basis for physiological variable collection throughout each trial.Results: Participants experienced reduced accelerations on impact at the distal tibia(p < 0.0001) but not the lower back(p = 0.1363) or forehead(p = 0.0551) during ATM compared to LTM. Consequently, large reductions in shock attenuation occurred during the ATM compared to LTM(p = 0.0001). Stride frequency was greater(p < 0.0001) and stride length was shorter(p = 0.0341) as a result of reduced swing time(p = 0.0201)for LTM, whilst ATM running increased physiological demand for both heart rate(p < 0.0001) and O2(p < 0.0001) compared to LTM.Conclusion: These findings show ATM reduces impact stress on the passive structures of the lower limbs whilst increasing physiological demand when running at matched speeds.