Characterizing Steady-State Cardiovascular and Metabolic Responses of Recreational Climbers during Motorized Treadmill Climbing

Abstract

Given that the popularity of indoor climbing exceeds that of outdoor climbing, health professionals need a better understanding of how these indoor climbing activities can be used to prescribe exercise. The primary goal of this study was to characterize both cardiovascular and metabolic responses of motorized treadmill climbing with respect to thresholds for heart rate as a percent of maximum (%HR) and metabolic equivalents (METs). Additionally, this study used these data to generate MET and energy expenditure (EE) prediction equations for prescription purposes. Methods: Twenty non-competitive recreational climbers (16 men; 4 women) were recruited to climb six combinations of “slow” and “fast” climbing speed (4.6-9.1 m/min) across three treadmill grades: vertical (90°), overhang or negative incline (85-80°), positive incline (95-100°). A portable metabolic system was worn by climbers during testing to measure HR and oxygen uptake (VO2), the latter of which was converted to EE and METs using standard formulae. Mean HR% and MET values were compared to intensity thresholds (65%, or 3 and 6 METs) using one-sample t-tests, while standard multiple regression techniques were used to predict EE and METs from a pool of variables (climbing treadmill speed and grade, body mass, gender. Results: HR% (70.0-85.4%) was >65% at all test conditions (P<0.01) and mean MET values exceeded the 3-MET threshold and was ≥6-MET threshold at all conditions (6.0-8.5 METs; P<0.01). Multiple prediction equations for both EE (R2=0.81; SEE=±0.83 kcals/min; P<0.001) and METs (R2=0.73; SEE=±0.6 METs; P<0.001) included speed, grade, and gender. Conclusions: The vigorous metabolic intensity for motorized treadmill climbing (≥6 METs) in this study was clearly sufficient to promote positive health and metabolic fitness in healthy adults. In addition, health professionals can use the EE and MET prediction equations to prescribe specific motorized treadmill climbing intensities to clients, as well as generate climbing-specific testing protocols.