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Comparison of the lactate and ventilatory thresholds during prolonged work

The purpose of this investigation was to compare the ventilatory threshold (T(vent)) with the lactate threshold (T(lact)) during 60 minutes of steady-state exercise at the calculated thresholds. Eight trained, male
cyclists (mean age=23.3 yrs, ht=176.4 cm, wt=70.7 kg, VO₂max=61.02
ml/kg‧minˉ¹) performed a 23 W/min progressive intensity cycling test for determination of T(lact) and T(vent). T(vent) was determined by the non-linear increase in excess CO₂ (ExCO₂) while T(lact) was calculated by
the 'individual anaerobic threshold' (IAT) method. Subsequently, subjects performed up to 60 minutes steady-state exercise at the threshold workloads. Results at T(vent) and T(lact) indicate significant differences
(p<0.01; T(lact)>T(vent)) between VO₂, ExCO₂, HR, [BLa] and workload as
calculated by Hotelling's T²-test. During the steady state exercise at each
specified workload, VO₂, [BLa], heart rate and ExCO₂ were measured at 15
minute intervals. All subjects completed the steady-state exercise at T(vent) (VSS) while only 2 subjects completed the steady-state exercise at T(lact) (LSS) (avg time=48.4 min). Comparison of metabolic variables

using MANOVA and multiple comparisons revealed significant differences between VSS and LSS for HR and VO₂ at all time intervals, for [BLa] at 30
and 45 minute intervals and for ExCO₂ at the 30 minute interval. Furthermore, examination of [BLa] over time using trend analysis revealed a stabilization during VSS ([formula omitted]=3.05 mmol‧Lˉ¹) whereas [BLa] continuously increased over time during LSS. Findings indicate that T(lact) (IAT method) overestimates the ability to perform prolonged work over 45 min. while T(vent) (ExCO) allows for steady-state exercise greater than 60 minutes. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

Identiferoai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/30153
Date January 1991
CreatorsLoat, Christopher Eino Russell
PublisherUniversity of British Columbia
Source SetsUniversity of British Columbia
LanguageEnglish
Detected LanguageEnglish
TypeText, Thesis/Dissertation
RightsFor non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.

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