Comparaison des données bioénergétiques observées lors d'un exercice musculaire sur bicyclettes équipées de plateaux rond ou «Harmonic

Introduction

In order to “harmonise” the constraints of pedalling (attenuate top dead centre and bottom dead centre), a non circular chain ring called “Harmonic” has been put on the market. The purpose of this study is to understand bioenergetic repercussions of this type of non circular chain ring during muscular exercise upon a bicycle.

Method

Thirteen regional level cyclists took part in this study. Each subject performed two maximal oxygen uptake exercise tests, one with a circular chain ring, the other with a “Harmonic” chain ring with the same cogwheel (52 tooth). They were performed on a cyclo-simulator. Speeds (km·h^t-1) and/or simulated slopes (%) increased every 2 min 30 s. They were, respectively: 28-2, 30-2, 35-2, 37.5-2, 40-2, 40-3, 42.5-3. O₂ uptake (VO₂), pulmonary ventilation and heart rate were measured continuously; and blood lactate concentration was measured during the last 30 s of each level.

Results

Regardless of speeds and slopes, there was no significant difference for VO₂, pulmonary ventilation, heart rate and blood lactate concentration between the two chain rings.

Conclusion

If the chain ring in question is supposed to attenuate top dead centre and bottom dead centre pedalling, it does not present any lessened energy expenditure during muscular exercise.