Acute transcutaneous CO2 exposure: A feasibility study for the future investigation of CO2-specific exercise adaptations.

Blood flow restricted (BFR) exercise induces musculoskeletal adaptations at reduced exercise loads. The role of hypercapnia during BFR remains unclear, due to difficulties in isolating this factor in vivo. We evaluated a hypercapnic model designed to raise CO2 levels similar to low-intensity exercise, while minimizing other exercise-induced effects (e.g. hypoxia, lactate accumulation). In a crossover design, 18 participants were administered pure CO₂ (EXP) or room air (CON) transcutaneously from the neck down for 90 min. Ventilatory and blood markers (V̇CO2, ETCO2, V̇E, pH, and PCO2) were measured throughout. The area under the curve of ETCO2 was higher during EXP compared to CON (75.5 ± 83.7 vs. 32.8 ± 57.5 a.u., p = 0.05), confirming successful CO2 administration. However, there was no significant effect on PCO2 (p = 0.09), despite a trend toward reduced pH (p = 0.059).

CONCLUSION

While transcutaneous CO2 absorption induced a physiological response, the magnitude was small, and this model shows limited ecological validity to simulate exercise-like conditions.