Breath holding during and after muscular exercise

Breath holding was performed a) at rest, b) at the beginning of muscular work, c) during the steady state of work and d) immediately after work. End-expiratory air was analyzed for CO2 and O2 tensions. At breaking point the PaCOCO2 values were similar in a) and b) (below 52 mm Hg with air breathing) and in c) and d, respectively. The higher the work load the higher the PaCOCO2 in c) and d) (above 70 mm Hg at heavy work load breathing air; after O2 breathing above 90 mm Hg). The PaOO2 values obtained were lower during and after work than at rest. These events and the increased ‘tolerance’ for high CO2 and low O2 in breath holding during and immediately after exercise are discussed in light of the theory that proprioreceptive impulses from working limbs are important in the control of respiration during exercise. Submitted on October 2, 1959