Influence of ascent speed on rock climbing economy

Abstract

In some types of human and animal locomotion, speed influences the amount of metabolic energy expended per unit mass and distance (energy cost, EC) and as speed decreases or increases away from a healthy person’s self-selected speed (SS_S), the EC increases. When asked to climb a vertical wall using their preferred speed, similar to walking, climbers with the same level of skill spontaneously select comparable speeds. The present research was designed to investigate how speed of ascent affects the EC of climbing; we were also interested in finding out whether climbers with the same level of skill exhibit a common SS_S and if it is correlated with optimal economy (i.e. minimum EC). A representative experimental set-up was prepared to quantify the economy of rock climbing by measuring steady-state oxygen intake (VO₂) in very skilled climbers while climbing at their SS_S and at higher (H_S) and lower (L_S) speed, and computing the relative EC. The main findings were: (a) climbers with the same level of skill exhibited the same preferred climbing speed (10.2 ± 1.5 m·min⁻¹) at the same fraction of their maximum VO₂ (VO_2peak) measured on a cycle ergometer (71.7 ± 15.2%), and (b) climbing economy continuously increased as speed increased from L_S to H_S. Thus climbing at the SSS does not correspond to the optimal economy. A possible explanation for these findings may be that although it does not match the minimum EC, the SS_S would be the best compromise between the need to reduce the time spent in isometric work (useless and costly) and the need to avoid early muscle fatigue due to increased speed and frequency of muscle contraction.