Effect of exercise intensity on the variability of cycling economy

Abstract

The aim of this study was to assess the effects of intensity on the reliability of VO2, VCO2, RER, VE, tidal volume (V(T)) respiratory rate (RR), heart rate (HR) and cycling efficiency (CE), during submaximal constant intensity exercise. Therefore, six healthy men which mean (±SD) ages, heights, weights and percent body fat were: 22.3 ± 0.8 years, 174.6 ± 2.7 cm, 66.5 ± 6.8 kg, 10.2 ± 3.9%, were tested on seven separate days. The first three sessions were used for familiarization, the 4th to perform an incremental exercise test to exhaustion (40 w/3 min) and the last three to assess the aforementioned ergoespirometric variables at the following intensities: 80, 100, 110, 120, 130, 140, 150, 160, 180, 200 and another time 100 w. The VO2 at each intensity was similar across test, yet the economy regression line was indistinguishable among the last three test. HR was the most reproducible variable, thus the intra-subjects variation coefficient (VCi) lied between 3.5 and 4.8%. Variability across intensities was similar for all the aforementioned variables, but VO2 and CE that showed less reproducible values at intensities lowest than 50% of VO2 peak (i.e. < 110 w; VCi: 6-8%), than at highest intensities (CVi: 3-5%). No significant difference was seen between VCi in the first and in the last 100 w bout (8.0 ± 4.0 y 6.2 ± 2.0%, respectively). In conclusion, at low intensities, both cycling economy and cycling efficiency were less reliable. However, the reliability of VCO2, RER, V(E), V(T), RR and HR was independent on exercise intensity, during constant intensity submaximal exercise, at intensities lying between 40 and 75% of VO2 peak.