Sato T; Department of Physical Therapy, Fukushima Medical University, Fukushima City, Japan.
Sagawa S; Kataoka D; Igarashi M; Ishibashi R; Endo Y; Tsubaki A; Tamiya H; Morishita S

Advances in Experimental Medicine & Biology. 1498:271-275, 2026.
VI 1

PURPOSE: We aimed to clarify the compensatory changes in oxygenation in
non-active versus active muscles during incremental exercise.

METHODS: Fifteen male volunteers (age, 21.1 +/- 0.5 years) underwent
cardiopulmonary exercise testing (CPET) using a cycle ergometer ramp
protocol, while maintaining the left upper extremity in a drooping
position. We continuously recorded oxygenated hemoglobin (O2Hb),
deoxygenated hemoglobin (HHb), total hemoglobin (THb), and tissue oxygen
saturation (StO2) in the left vastus lateralis (active muscle) and triceps
brachii (non-active muscle), as well as cardiopulmonary parameters, during
the test.

RESULTS: There were significant interactions between time and muscles for
all changes in O2Hb (p < 0.001), HHb (p < 0.001), THb (p < 0.001), and
StO2 (p < 0.001). In the non-active muscle, O2Hb and StO2 remained higher
than at rest until the 40% point of the test, unlike in the active muscle.
HHb increased from the 80% point in the non-active muscle, but it
increased immediately after the start of the test in the active muscle.
THb showed no significant change in the non-active muscle, but it
continued to increase immediately after the start of the test in the
active muscle.

CONCLUSION: During CPET, O2Hb and StO2 in the non-active muscle remained
higher in the low- to moderate-intensity phases than in the rest phase and
decreased in the high-intensity phase, unlike in the active muscle.