Oxygen uptake (VO₂) kinetics during moderate constant-workrate (WR) exercise (>lactate-threshold (θ¸L)) are well described as exponential. Aboveθ¸L, these kinetics are more complex, consequent to the development of a delayed slow component (VO₂sc), whose aetiology remains controversial. To assess the extent of the contribution to the VO₂sc from arm muscles involved in postural stability during cycling, six healthy subjects completed an incremental cycle-ergometer test to the tolerable limit for estimation of θ¸L and determination of peak VO₂. They then completed two constant-WR tests at 90% of θ¸L and two at 80% of ∆ (difference between θ¸L and VO_2peak). Gas exchange variables were derived breath-by-breath. Local oxygenation profiles of the vastus lateralis and biceps brachii muscles were assessed by near-infrared spectroscopy, with maximal voluntary contractions (MVC) of the relevant muscles being performed post-exercise to provide a frame of reference for normalising the exercise-related oxygenation responses across subjects. Above supra-θ¸L, VO₂ rose in an exponential-like fashion ("phase 2), with a delayed VO₂sc subsequently developing. This was accompanied by an increase in [reduced haemoglobin] relative to baseline (∆[Hb]), which attained 79 ± 13 % (mean, SD) of MVC maximum in vastus lateralis at end-exercise and 52 ± 27 % in biceps brachii. Biceps brachii ∆[Hb] was significantly correlated with VO₂ throughout the slow phase. In contrast, for sub- L exercise, VO₂ rose exponentially to reach a steady state with a more modest increase in vastus lateralis ∆[Hb] (30 ± 11 %); biceps brachii ∆[Hb] was minimally affected (8 ± 2 %). That the intramuscular O₂ desaturation profile in biceps brachii was proportional to that for VO₂sc during supra-θ¸L cycle ergometry is consistent with additional stabilizing arm work contributing to the VO₂sc.