FUNCTIONAL EVALUATION SECTION   

Medicina dello Sport 2001 March;54(1):9-16

Copyright © 2001 EDIZIONI MINERVA MEDICA

language: English

Variability of physiological responses during 12 min of heavy cycling

Mognoni P. ¹, Grassi B. ¹, Sassi A. ², Impellizzeri F. ², Morelli A. ²

¹ Istituto Tecnologie Biomediche Avanzate, CNR, Segrate (Milano); ² Sport Service Mapei, Castellanza (Milano)

Background. The ven­til­a­to­ry anaer­o­bic thresh­olds are ­often eval­u­at­ed dur­ing incre­men­tal ­tests (.Winc), lead­ing to exhaus­tion in ­less ­than 15 min­utes.1 Main aim of ­this ­work is to ­assess the var­i­abil­ity of the rela­tion­ship ­between phys­io­log­i­cal respons­es dur­ing .Winc and con­stant ­load exer­cise (.Wcons).
Methods. Thirteen ­elite moun­tain­bik­ers per­formed a .Winc ­with 26 W . min-1 ­steps and 5 min of ­warm up at 135 W. Mechanical pow­er cor­re­spond­ing to 3.5 mM of ­blood lac­tate con­cen­tra­tion ([LA]cap) was cho­sen for a .Wcons ­with a 12 min tar­get ­time.
Results. Ten sub­jects ­were ­able to per­form the ­task. At the end of . Wcons ­heart ­rate (HR ) and [LA]cap ­were sim­i­lar to ­those ­found at the end of .Winc but O2 ­uptake (V.O2) and ven­ti­la­tion (V.e) ­were sig­nif­i­cant­ly low­er (–8.0% and –11.8%, respec­tive­ly). During . Wcons, HR and V.e ­increased ­from 6th to 12th min and [LA]cap ­from 4th to 12th but V.O2 did not ­change. All phys­io­log­i­cal var­i­ables at the end of .Wcons ­were com­put­ed as a frac­tion of the ­same var­i­ables at the end of .Winc. These frac­tions had larg­er SDs for [LA]cap (0.43) ­than for V.e (0.012), V.O2 (0.06) or HR (0.03). [LA]cap ­increased and end-­tidal pCO2 (PET­CO2) ­decreased ­almost lin­e­ar­ly dur­ing . Wcons. The SD of (PET­CO2) was ­about 3 mmHg and the inter­sub­jec­tive vari­abil­ities of (PET­CO2) and [LA]cap ­were unre­lat­ed.
Conclusions. In ­well-­trained endu­rance ath­letes 1) the rela­tion­ship ­between phys­io­log­i­cal var­i­ables meas­ured dur­ing . Winc, and . Wcons do not ­seem ­very ­strict, 2) the V.O2 ­slow com­po­nent dur­ing ­heavy ­work is insig­nif­i­cant, 3) the res­pir­a­to­ry com­pen­sa­tion to meta­bol­ic aci­do­sis is var­i­able.