PHYSIOLOGICAL RESPONSES OF WELL-TRAINED CYCLISTS TO FIELD AND LABORATORY MOUNTAIN BIKE RACE SIMULATIONS

Abstract

High power output (W.kg-1) of short duration is important in mountain bike (MTB) racing during the mass start, steep hill climbing, and sprints. Research examining the physiological demands of MTB racing is limited. PURPOSE To simulate a field MTB race in the laboratory to measure the physiological and metabolic responses associated with MTB racing. METHODS Five well-trained male MTB cross-country cyclists (VO2max 72.0 ± 4.6 ml.kg-1.min-1, maximum power output (MPO) 5.40 ± 0.30 W.kg-1, maximum heart rate (HRmax) 189 ± 7 bpm) performed two laps of a MTB course in the field using their race bikes with MTB SRM power cranks fitted. A laboratory MTB race simulation was performed using a wind braked ergometer. Cyclists attempted to match the average and peak power output (W.kg-1) achieved in the field trial in the laboratory. Power output, heart rate and cadence were measured during field and laboratory trials, while oxygen uptake (VO2) was determined only during the laboratory simulation. RESULTS Mean power output and heart rate between the field and laboratory trials were similar (4.18 ± 0.55 vs 4.22 ± 0.19 W.kg-1 respectively, 175 ± 9 vs 170 ± 8 bpm, p > 0.05). Time spent below 2 W.kg-1 and above 6 W.kg-1 for the field and laboratory trials accounted for ~32% and ~30% of the total time respectively. During field and laboratory trials cyclists utilised 77.4% vs 78.1% of MPO, 93.0% vs 90.1% of HRmax respectively. There was a significant difference between mean cadence in the field and laboratory trials (60.3 ± 9.1 vs 75.2 ± 7.0 rpm, respectively, p < 0.05). Mean and peak VO2 for the simulation were 57.5 ± 3.3 and 69.3 ± 4.4 ml.kg-1 · min-1 respectively, with cyclists sustaining an average of ~80% VO2max. CONCLUSION Although it is possible to reproduce the power output and heart rate responses of MTB racing in the laboratory, the power-cadence relationships appear more difficult to replicate.