Maximal Oxygen Uptake, Muscular Oxidative Capacity, and Ventilatory Threshold in Amateur Triathletes: Eight-Month Training Follow-Up

Purpose: Endurance sports performance is influenced by several factors, including maximal oxygen uptake (⩒O₂max), the percentage of ⩒O₂max that can be sustained in endurance events, running economy, and body composition. Traditionally, ⩒O₂max can be measured as an absolute value, adjusted for body mass, reflecting the athlete’s central capacity (maximal cardiac output), or adjusted for lean mass (LM), reflecting the athlete’s peripheral capacity (muscular oxidative capacity). The present study aims to evaluate absolute, total body mass, and lower limb LM-adjusted ⩒O₂max, ventilatory thresholds (VT), respiratory compensation points (RCP), and body composition during two training periods separated by 8 months.
Patients and Methods: Thirteen competitive amateur triathletes [seven men (40.7± 13.7 years old, 76.3± 8.3kg, and 173.9± 4.8cm) and six women (43.5± 6.9 years old, 55.0± 2.7kg, 164.9± 5.2cm)] were evaluated for body composition with dual-energy X-ray absorptiometry and ⩒O₂max, VT, RPC, and maximal aerobic speed (MAS) with a cardiorespiratory maximal treadmill test.
Results: The absolute ⩒O₂max (p = 0.003, d = 1.05), body mass–adjusted ⩒O₂max (p < 0.001, d = 1.2859), and MAS (p = 0.047, d = 0.6139) values differed significantly across evaluation periods. Lower limb LM–adjusted ⩒O₂max (p = 0.083, d = − 0.0418), %⩒O₂max at VT (p = 0.541, d = − 0.1746), speed at VT (p = 0.337, d = − 0.2774), % ⩒O₂max at RCP (p = 0.776, d = 0.0806), and speed at RCP (p = 0.436, d = 0.2234) showed no difference.
Conclusion: The sensitivities of ⩒O₂max adjusted for body mass and ⩒O₂max adjusted for LM to detect changes in physical training state differ. Furthermore, decreases in physical fitness level, as evaluated by ⩒O₂max values, are not accompanied by changes in VT.

Keywords: amateur triathletes, skeletal muscle oxidative capacity, triathlon, performance