Abstract
The aerobic cost of running (CR), an important determinant of running performance, is usually measured during constant speed running. However, constant speed does not adequately reflect the nature of human locomotion, particularly competitive races, which include stochastic variations in pace. Studies in non-athletic individuals suggest that stochastic variations in running velocity produce little change in CR. This study was designed to evaluate whether variations in running speed influence CR in trained runners. Twenty competitive runners (12 m, VO2max = 73 ± 7 mL/kg; 8f, VO2max = 57 ± 6 mL/kg) ran four 6-minute bouts at an average speed calculated to require ~90% ventilatory threshold (VT) (measured using both v-slope and ventilatory equivalent). Each interval was run with minute-to-minute pace variation around average speed. CR was measured over the last 2 min. The coefficient of variation (CV) of running speed was calculated to quantify pace variations: ±0.0 m∙s−1 (CV = 0%), ±0.04 m∙s−1 (CV = 1.4%), ±0.13 m∙s−1(CV = 4.2%), and ±0.22 m∙s−1(CV = 7%). No differences in CR, HR, or blood lactate (BLa) were found amongst the variations in running pace. Rating of perceived exertion (RPE) was significantly higher only in the 7% CV condition. The results support earlier studies with short term (3s) pace variations, that pace variation within the limits often seen in competitive races did not affect CR when measured at running speeds below VT.
Highlights
As defining features of human performance, world record (WR) performances have been of interest to physiologists
Given that VO2 max has largely been unchanged in elite runners over the last half-century, and evidence is lacking on systematic changes in anaerobic capacity, only ventilatory threshold (VT), fractional utilization and cost of running (CR) provide reasonable candidates for the continuing improvement in running records
The pace variations were expressed in relation to the coefficient of variation (CV) of running velocity to allow for individual differences in running speed and to show the extent of variability around each runner’s average speed at ~90%VT
Summary
As defining features of human performance, world record (WR) performances have been of interest to physiologists. A number of physiological determinants have emerged as indicators of performance. These determinants include maximal aerobic capacity, fractional utilization of aerobic capacity, lactate threshold, and the aerobic cost of running (CR) [1]. Pacing strategy has emerged as a potential determinant of performance, as contemporary records have been achieved with a relatively more even [3] or unchanged pacing strategy [4], important head-to-head competitive events are typically contested with highly stochastic pacing patterns [5]. Fractional utilization is of established importance within competitive runners [6] and is high in the most elite runners [7,8]. The CR is thought to vary meaningfully amongst runners and is low in elite runners [8,9]
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