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Abstract
Ultra-long distance running, from marathons and greater distances require large amounts of nutrition and especially hydration. Many athletes that race these greater running distances wear hydration packs, which alters the dynamics of their gait. It is not known whether the added weight could lead to potential injuries. This study investigated the ground reaction forces while running with a rear mounted hydration pack, to assess whether an increased injury risk was present while wearing the pack. Twenty participants (age = 26.7 ± 2.6 years) completed 8 total trials while wearing the pack; two trials at each of the four water reservoir weights, corresponding to empty, 0.5L, 1.5L, and 2.5L of water. Peak ground reaction force data in the vertical, mediolateral and anteroposterior directions were collected from two force plates mounted at the center of the running track. Analysis of variance indicated that the hydration packs did not significantly increase ground reaction forces as the weight of the pack increased. However, decreased ground reaction forces were seen with a heavier pack in the vertical direction. This decrease in peak force in the vertical direction could likely be due to adjustments the participants made to their gait or perhaps due to the wobbling mass of the pack, dampening the peak force. In either case, this study suggests that wearing a hydration pack does not appear to increase the risk of injury while running longer distances as long as athletes train with the pack prior to racing, to allow for gait adjustments.
