O2 saturation in the intercostal space during moderate and heavy constant-load exercise

Area of Science:

• Exercise Physiology
• Respiratory Muscle Physiology

Background:

• Minute ventilation (VE) increases during exercise to meet metabolic demands.
• The oxygen saturation in intercostal muscles (SO2IC) may be affected by increased VE and oxygen consumption.

Purpose of the Study:

• To investigate if the relationship between VE and SO2IC is consistent across different exercise protocols.
• To determine the impact of exercise intensity and type on intercostal muscle deoxygenation.

Main Methods:

• Measured VE and SO2IC during ramp incremental exercise tests (RIET) and constant-load exercise tests (CET) in six male subjects.
• Compared SO2IC responses during moderate (CET_MOD) and heavy (CET_HVY) constant-load exercise with RIET.

Main Results:

• SO2IC decreased from the start of both CET_MOD and CET_HVY.
• SO2IC was significantly lower during CET_HVY compared to CET_MOD.
• At similar VE levels, SO2IC was higher during CET_HVY than during RIET.

Conclusions:

• The decrease in SO2IC during exercise is influenced by factors beyond increased oxygen consumption in intercostal muscles.
• Reduced oxygen supply to intercostal muscles likely contributes to deoxygenation during heavy exercise.