THE EFFECT OF DOWNHILL RUNNING ON RUNNING ECONOMY AND RUN MECHANICS:

Downhill running can be associated with significant muscle damage, transient impairment of muscle function, and soreness in the days following the exercise. This study was designed to examine the effects of a single bout of downhill running on measures of running economy, running mechanics and indices of physiological stress. Running economy was assessed on five, well-trained, male, distance runners (VO2max = 58.78 ± 9.66 ml·kg−1·min−1) approximately 48 hours prior to (PRE) performing a 30 minute downhill run (−10% slope at 70% VO2max) and 48 hours after completing the downhill run (POST). Running economy (0% grade) was assessed at treadmill velocities corresponding to 65, 75, and 85% of VO2max. Stride length (SL) was measured by two-dimensional kinematic analysis using markers placed at the foot, ankle, knee and hip. Two-way ANOVA was used to examine alterations in VO2, lactate, heart rate (HR) and SL. Soreness ratings (six point scale) were anlyzed using one-way ANOVA, with measures collected prior to the downhill run, and at 24 and 48 hours after the downhill run. Significant time effects (p < 0.05) were found for HR (PRE = 155 ± 3.43, POST = 159 ± 3.42 bpm), SL (PRE = 2.56 ± 0.10, POST = 2.51 ± 0.10 m/stride) and soreness, where PRE (0.0 ± 0.0) was different from the 24 (3.9 ± 0.29) and 48 hour (2.8 ± 0.51) measures. A trend (p = 0.08) was present for VO2 to be higher at POST (PRE = 44.41 ± 2.21, POST = 45.21 ± 2.26 ml·kg−1·min−1). Lactate concentrations were non-significantly elevated at POST (p = 0.14). Based on these preliminary data, a single bout of downhill running has been found to elicit changes in measures of physiological stress and gait mechanics that tend to result in a higher energy expenditure while running at fixed treadmill velocities.