Reliability of a high-intensity endurance cycling test

This study assessed the reproducibility of performance and selected metabolic variables during a variable high-intensity endurance cycling test. 8 trained male cyclists (age: 35.97.7 years, maximal oxygen uptake: 54.33.9mLkg ¹min ¹) completed 4 high-intensity cycling tests, performed in consecutive weeks. The protocol comprised: 20min of progressive incremental exercise, where the power output was increased by 5% maximal workload (Wmax) every 5min from 70% Wmax to 85% Wmax; ten 90s bouts at 90% Wmax, separated by 180s at 55% Wmax; 90% Wmax until volitional exhaustion. Blood samples were drawn and heart rate was monitored throughout the protocol. There was no significant order effect between trials for time to exhaustion (mean: 4113.060.8s) or total distance covered (mean: 46126.21968.7m). Total time to exhaustion and total distance covered showed very high reliability with a mean coefficient of variation (CV) of 1.6% (95% Confidence Intervals (CI) 0.0124.3s) and CV of 2.2% (95% CI 0.0 1904.9m), respectively. Variability in plasma glucose concentrations across the time points was very small (CV 0.464.3%, mean 95% CI 0.00.33 to 0.00.94mmolL ¹). Plasma lactate concentrations showed no test order effect. The reliability of performance and metabolic variables makes this protocol a valid test to evaluate nutritional interventions in endurance cycling.