Context: The importance of maintaining a euhydrated state for human survival has been well documented. Researchers have also sought to describe the effects dehydration has on muscular endurance, strength and power in varying climactic conditions. There is a paucity of published works exploring the impact dehydration plays on the physiological and mechanical properties of muscle and connective tissues which may affect athletic performance and injury risk. Objective: To measure the effects dehydration has on the mechanical properties of the muscles and connective tissues of teh posterior leg. It was hypothesized that when dehydrated, the mechanical properties of the connective and muscular tissues of the posterior leg would be negatively affected. Design: A crossover design. Setting: Laboratory. Patients or Other Participants: Nineteen male collegiate runners between the ages of 18-25 years old with no history of lower leg injury in the past 6 months. Main Outcome Measure(s): Each subject attended three sessions: baseline, dehydration and euhydration conditions. The order of testing, eurhydrated vs. dehydrated, was randomly assigned and the lead researcher was blinded to the testing conditions. Sit and reach (SnR) scores and terminal leg raise (TSLR) measurements were analyzed using a MANOVA. Posterior leg stiffness (PLS) was analyzed using a repeated measures ANOVA for each of the three tesing conditions. Results: Dehydrated 18-25 year old male runners demonstrated statistically significant decreases in mean SnR scores, P=0.001, and mean TSLR, P=0.001, with a concurrent increase in mean PLS, P=0.001, as compared to when they were euhydrated. Conclusions: The observed increase in stiffness combined with decreased flexibility may be linked to an increase in risk for lower extremity injury.
