Acute Apnea Does Not Improve 3-km Cycling Time Trial Performance

Abstract

ABSTRACT Purpose Intense exercise evokes a spleen contraction releasing red blood cells into blood circulation. The same mechanism is found after acute apnea, increasing hemoglobin concentration ([Hb]) by 2% to 5%. The aim of this study was twofold: [1] to identify the optimal apnea modalities to acutely increase [Hb] and [2] use these modalities to examine whether prerace apnea can improve a 3-km time trial (TT). Methods In part 1, 11 male subjects performed 12 different apnea protocols based on three modalities: mode, frequency, and intensity. Venous blood samples for [Hb] were collected before, immediately, and 5 min after each protocol. In part 2, 12 recreationally active subjects performed 3-km cycling TT in three different conditions: apnea, control, and placebo, after a 10-min warm-up. Power output, HR, and oxygen uptake (V˙O 2 ) were continuously measured. Venous [Hb] was sampled at baseline, after warm-up, and before TT. Additionally, these subjects performed constant cycling at Δ25 (25% between gas exchange threshold and V˙O 2 max) in two conditions (control and apnea) to determine V˙O 2 kinetics. Results Although including one single apnea in the warming up evoked a positive change in [Hb] pattern ( P = 0.049) and one single apnea seemed to improve V˙O 2 kinetics in constant submaximal cycling (τ: P = 0.060, mean response time: P = 0.064), performance during the 3-km TT did not differ between conditions ( P = 0.840; apnea, 264.8 ± 14.1 s; control, 263.9 ± 12.9 s, placebo, 264.0 ± 15.8 s). Average normalized power output ( P = 0.584) and V˙O 2 , HR, and lactate did not differ either ( P > 0.05). Conclusions These results suggest that potential effects of apnea, that is, speeding of V˙O 2 kinetics through a transient increase in [Hb], are overruled by a warming-up protocol.