Spontaneous pacing during overground hill running.

PURPOSE: To investigate speed regulation during overground running on undulating terrain.
METHODS: After an initial laboratory session to calculate physiological thresholds, eight experienced runners completed a spontaneously paced time trial over three laps of an outdoor course involving uphill, downhill, and level sections. A portable gas analyzer, global positioning system receiver, and activity monitor were used to collect physiological, speed, and stride frequency data.
RESULTS: Participants ran 23% slower on uphills and 13.8% faster on downhills compared with level sections. Speeds on level sections were significantly different for 78.4 +/- 7.0 s following an uphill and 23.6 +/- 2.2 s following a downhill. Speed changes were primarily regulated by stride length, which was 20.5% shorter uphill and 16.2% longer downhill, whereas stride frequency was relatively stable. Oxygen consumption averaged 100.4% of runner's individual ventilatory thresholds on uphills, 78.9% on downhills, and 89.3% on level sections. Approximately 89% of group-level speed was predicted using a modified gradient factor. Individuals adopted distinct pacing strategies, both across laps and as a function of gradient.
CONCLUSIONS: Speed was best predicted using a weighted factor to account for prior and current gradients. Oxygen consumption (VO2) limited runner's speeds only on uphill sections and was maintained in line with individual ventilatory thresholds. Running speed showed larger individual variation on downhill sections, whereas speed on the level was systematically influenced by the preceding gradient. Runners who varied their pace more as a function of gradient showed a more consistent level of oxygen consumption. These results suggest that optimizing time on the level sections after hills offers the greatest potential to minimize overall time when running over undulating terrain.