Effects Of Incline And Decline Surfaces On Spatio-Temporal Characteristics During Running

Previous investigations examining the spatio-temporal changes (STC) associated with uphill (UH) and downhill (DH) running, including ground contact time (GCT), and stride frequency (SF), have reported varying results. Additionally, step width (SW) has been suggested to influence lower extremity loading. PURPOSE: This study aimed to compare STC, particularly GCT, SF, and SW, between UH, DH, and level running. METHODS: Healthy runners achieving at least 16.1 km/wk of training for the past 6 months (12 females, 11 males) completed 60 seconds of treadmill running bouts at 90% 5 K pace at 0°, ±3°, ±6°, and ± 9°. Prior to data collection (>72 hrs), participants completed a familiarization session to become accustomed to procedures and verify their ability to complete the targeted pace under each condition. During the data collection session, reflective marker clusters placed on the right and left feet were captured by a motion capture system and used to compute ground contact/off, followed by SF, SW and dominant limb GCT from 5 strides once steady state reached. Separate analysis of variance models were followed by polynomial contrasts to determine responses across conditions (+9° to -9°). RESULTS: Significant condition effects were revealed for all outcome measures (P < .002). The significant GCT quadratic trend (P < .001, d = 1.0) revealed an increase from +9° to +3° (.36 ± .04 s to .38 ± .05 s) followed by a decrease +3° to -9° (.38 ± .05 s to .32 ± .06 s). The significant SF quadratic trend (P < .001, d = 1.1) identified a decline from +9° to -3° (1.5 ± .1 to 1.4 ± .1 Hz) followed by an increase from -3° to -9° (1.4 ± .1 to 1.5 ± .1 Hz). A significant SW linear increase (P = .001, d = .80) existed across +9° to -9° (.04 ± .09 to .08 ± .10 m). CONCLUSIONS: These results confirm some previous reports of UH to DH changes regarding GCT and SF. The current SW results suggest surface inclination could be a potent factor in lower extremity loading. Future research examining external load carry on similar characteristics is warranted.