Characteristics of Muscle Oxygenation of the Upper and Lower Limb During Moderate-Intensity Upper Limb Crank...

[Purpose] To characterize oxygenated hemoglobin (O₂Hb), deoxygenated hemoglobin (HHb), total hemoglobin (THb), and muscle oxygen saturation (StO₂) changes in the upper and lower limb muscles during moderate-intensity upper limb crank exercise. [Methods] Fifteen healthy males (mean age, height, and weight: 21.1 ± 0.4 years, 172.2 ± 5.9 cm, and 63.3 ± 8.0 kg, respectively) were recruited. The experimental protocol consisted of a 4-min rest, 4-min warm-up, and 20-min constant-load exercise, followed by 10 min of post-exercise rest. O₂Hb, HHb, THb, and StO₂ of the triceps (TR), vastus lateralis (VL), and gastrocnemius muscles (GM) were measured using near-infrared spectroscopy. Changes from rest (ΔO₂Hb, ΔHHb, ΔTHb, ΔStO₂) were analyzed using a repeated-measures ANOVA. [Results] TR ΔO₂Hb significantly decreased at 1-3 min of warm-up and significantly increased from 5 min into exercise. The TR HHb significantly increased from 2 min after starting the warm-up to the end of exercise. VL ΔO₂Hb and ΔTHb significantly increased immediately after exercise onset. GM ΔO₂Hb and ΔTHb increased from 7 to 9 min after exercise onset. The VL ΔHHb increased from 14 to 15 min to the end of exercise, and the GM ΔHHb increased post-exercise. [Conclusion] This study elucidates the influence of systemic circulatory responses on oxygenation dynamics in non-active muscles during upper limb exercise, offering novel insights into whole-body hemodynamic adaptations to localized exercise.