Intercostal Muscles Oxygenation and Breathing Pattern during Exercise in Competitive Marathon Runners

The study aimed to evaluate the association between the changes in ventilatory variables (tidal volume (Vt), respiratory rate (RR) and lung ventilation (VE)) and deoxygenation of m.intescostales (Delta SmO2-m.intercostales) during a maximal incremental exercise in 19 male high-level competitive marathon runners. The ventilatory variables and oxygen consumption (VO2) were recorded breath-by-breath by exhaled gas analysis. A near-infrared spectroscopy device (MOXY (R)) located in the right-hemithorax allowed the recording of SmO2-m.intercostales. To explore changes in oxygen levels in muscles with high demand during exercise, a second MOXY (R) records SmO2-m.vastus laterallis. The triphasic model of exercise intensity was used for evaluating changes in SmO2 in both muscle groups. We found that ASmO(2)-m.intercostales correlated with VO2-peak (r = 0.65; p = 0.002) and the increase of VE (r = 0.78; p = 0.001), RR (r = 0.54; p = 0.001), but not Vt (p = 0.210). The interaction of factors (muscles x exercise-phases) in SmO2 expressed as an arbitrary unit (a.u) was significant (p = 0.005). At VT1 there was no difference (p = 0.177), but SmO2-m.intercostales was higher at VT2 (p < 0.001) and VO2-peak (p < 0.001). In high-level competitive marathon runners, the m.intercostales deoxygenation during incremental exercise is directly associated with the aerobic capacity and increased lung ventilation and respiratory rate, but not tidal volume. Moreover, it shows less deoxygenation than m.vastus laterallis at intensities above the aerobic ventilatory threshold.

Automated summary

The study found that deoxygenation of m.intercostales during incremental exercise in high-level competitive marathon runners is directly associated with aerobic capacity and increased lung ventilation and respiratory rate, but not tidal volume. Furthermore, m.intercostales shows less deoxygenation than m.vastus laterallis at intensities above the aerobic ventilatory threshold.