Original articles  EXERCISE PHYSIOLOGY AND BIOMECHANICS 

The Journal of Sports Medicine and Physical Fitness 2003 March;43(1):51-6

Copyright © 2009 EDIZIONI MINERVA MEDICA

lingua: Inglese

Influence of the base-line determination on work efficiency during submaximal cycling

Hintzy-Cloutier F. ¹, Zameziati K. ², Belli A. ²

¹ Laboratoire de Modélisation des Activités Sportives Bourget du Lac, France 2 Laboratoire de Physiologie, GIP Exercice St. Etienne, France

Aim. The pur­pose of ­this ­study was to com­pare ­work effi­ciency ­values (WE = ­work accom­plished/­energy expen­di­ture ­above exer­cising ­with 0 ­load) ­among dif­ferent ­unloaded ­base-­line cor­rec­tion tech­niques for dif­ferent ­power out­puts.
­Methods. ­Twelve ­healthy men per­formed 6 5-min ­steady-­state exer­cises of 0 (­unloaded), 40, 80, 120, 160 and 200 W at a ped­alling ­rate of 90 rpm on a ­cycle ergom­eter. ­Three dif­ferent ­unloaded ­base-­line cor­rec­tions ­were ­used for WE cal­cu­la­tion: an ­actual meas­ure­ment of V.O2 cor­re­sponding to the ­unloaded ped­alling exer­cise, the y-inter­cept ­value of the ­linear regres­sion ­between V.O2 and ­power ­output and the y-inter­cept ­value of the cur­vi­linear V.O2-­power regres­sion.
­Results. The ­present ­study dem­on­strated ­that WE was sig­nif­i­cantly ­higher ­when deter­mined ­using the ­actual meas­ure­ment of the ­unloaded V.O2 ­than y-inter­cept ­values of the ­linear (p<0.001) and cur­vi­linear (p<0.05) V.O2-­power regres­sions. WE ­based on theo­ret­ical deter­mi­na­tions (­linear vs cur­vi­linear regres­sions) ­were not sig­nif­i­cantly dif­ferent. The ­power ­output sig­nif­i­cantly ­affected all WE ­index, ­with ­higher WE ­being meas­ured ­when the ­power ­output was low and ­lower WE ­when ­power ­output was ­high.
Con­clu­sion. The ­high WE ­values deter­mined ­using the ­actual V.O2 meas­ure­ment ­could be ­explained by (i) the addi­tional ­energy ­expended to stab­ilise the ­body in addi­tion to the ­energy expen­di­ture of ­moving the ­lower ­limbs ­without ­power pro­duc­tion and by (ii) the dif­fi­culty to experi­men­tally repro­duce the ­unloaded con­di­tion. The ­large ­range of WE ­values meas­ured in the ­present ­study is due to dif­fer­ences in the pro­ce­dures ­used to deter­mine the ­unloaded V.O2 (and ­thus dif­fer­ences in ­unloaded V.O2 ­values) as ­well as dif­fer­ences in the ­cycling inten­sities.