Aerobic and Anaerobic Thresholds Determined from Venous Lactate or from Ventilation and Gas Exchange in Relation to Muscle Fiber Composition*

Abstract

The aerobic and anaerobic thresholds determined from venous lactate (AerT_La and AnT_La) or from ventilation and gas exchange (AerT_r and AnT_r) in relation to muscle fiber composition were compared. Twelve subjects were studied in double exercise tests carried out until voluntary exhaustion. They were divided into two groups according to their muscle fiber type in the vastus lateralis muscle: ST group with a majority of slow-twitch fibers (ST% = 66.0% ± 7.3%) and FT group with a majority of fast-twitch fibers (ST% = 27.7% ± 8.4%). A 2-min incremental exercise test protocol on a bicycle was used. There were no significant differences between the ST and FT groups in the V̇O_2max or inthe La_max. Neither the AerT nor the AnT related to the V̇O_2max (%) differed between the ST and FT groups. In the FT group the AnT_La occurred 0.70 min in the first test and 1.06 min in the second test earlier than the AnT_r, whereas in the ST group the AnT_La occurred at the same time or 0.44 min later, respectively, than the AnT_r (P < 0.05). Expressed as V̇O₂ the differences between thresholds were not so distinct. The results demonstrated that the mutual relation between the AnT_La and AnT_r seemed to be dependent on the fiber type majority in exercising muscles (vastus lateralis) among untrained men.

Key words

aerobic threshold - anaerobic threshold - blood lactate - muscle fiber types - ventilation