Physiological Responses to Supramaximal Running Exercise with End-Expiratory Breath Holding up to the Breaking Point

This study aimed to assess the physiological responses to repeated running exercise performed at supramaximal intensity and with end-expiratory breath holding (EEBH) up to the breaking point. Eight male runners participated in two running testing sessions on a motorized treadmill. In the first session, participants performed two sets of 8 repetitions at 125% of maximal aerobic velocity and with maximum EEBH. Each repetition started at the onset of EEBH and ended at its release. In the second session, participants replicated the same procedure, but with unrestricted breathing (URB). The change in cerebral and muscle oxygenation (Delta[Hbdiff]), total haemoglobin concentration (Delta[THb]) and muscle reoxygenation were continuously assessed. End-tidal oxygen (PETO2) and carbon dioxide pressure (PETCO2), arterial oxygen saturation (SpO2) and heart rate (HR) were also measured throughout exercise. On average, EEBH was maintained for 10.1 +/- 1 s. At the breaking point of EEBH, PETO2 decreased to 54.1 +/- 8 mmHg, whereas PETCO2 increased to 74.8 +/- 3.1 mmHg. At the end of repetitions, SpO2 (nadir values 74.9 +/- 5.0 vs. 95.7 +/- 0.8%) and HR were lower with EEBH than with URB. Cerebral and muscle Delta[Hbdiff] were also lower with EEBH, whereas this condition induced higher cerebral and muscle Delta[THb] and greater muscle reoxygenation. This study showed that performing repeated bouts of supramaximal running exercises with EEBH up to the breaking point induced a fall in arterial, cerebral and muscle oxygenation compared with the URB condition. These phenomena were accompanied by increases in regional blood volume likely resulting from compensatory vasodilation to preserve oxygen delivery to the brain and muscles.