AUTHOR=Grossman Kevin J. , Lim David J. , Murias Juan M. , Belfry Glen R. 

TITLE=The Effect of Breathing Patterns Common to Competitive Swimming on Gas Exchange and Muscle Deoxygenation During Heavy-Intensity Fartlek Exercise

JOURNAL=Frontiers in Physiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2021.723951

DOI=10.3389/fphys.2021.723951

ISSN=1664-042X

ABSTRACT=<p>During competitive freestyle swimming, the change of direction requires a turn followed by ∼15 m of underwater kicking at various intensities that require a ∼5 s breath-hold (BH). Upon surfacing, breathing must be regulated, as head rotation is necessary to facilitate the breath while completing the length of the pool (∼25 s). This study compared the respiratory and muscle deoxygenation responses of regulated breathing vs. free breathing, during these 25–5 s cycles. It was hypothesized that with the addition of a BH and sprint during heavy-intensity (HVY) exercise, oxygen uptake (VO<sub>2</sub>) and oxygen saturation (S<sub>at</sub>O<sub>2</sub>) would decrease, and muscle deoxygenation ([HHb]) and total hemoglobin ([Hb<sub>tot</sub>]) would increase. Ten healthy male participants (24 ± 3 years) performed 4–6 min trials of HVY cycling in the following conditions: (1) continuous free breathing (CONLD); (2) continuous with 5 s BH every 25 s (CONLD-BH); (3) Fartlek (FLK), a 5 s sprint followed by 25 s of HVY; and (4) a combined Fartlek and BH (FLK-BH). Continuous collection of VO<sub>2</sub> and S<sub>at</sub>O<sub>2</sub>, [Hb<sub>tot</sub>], and [HHb] <italic>via</italic> breath-by-breath gas analysis and near-infrared spectroscopy (normalized to baseline) was performed. Breathing frequency and tidal volumes were matched between CONLD and CONLD-BH and between FLK and FLK-BH. As a result, VO<sub>2</sub> was unchanged between CONLD (2.12 ± 0.35 L/min) and CONLD-BH (2.15 ± 0.42 L/min; <italic>p</italic> = 0.116) and between FLK (2.24 ± 0.40 L/min) and FLK-BH (2.20 ± 0.45 L/min; <italic>p</italic> = 0.861). S<sub>at</sub>O<sub>2</sub> was higher in CONLD (63 ± 1.9%) than CONLD-BH (59 ± 3.3%; <italic>p</italic> &lt; 0.001), but was unchanged between FLK (61 ± 2.2%) and FLK-BH (62 ± 3.1%; <italic>p</italic> = 0.462). Δ[Hb<sub>tot</sub>] is higher in CONLD (3.3 ± 1.6 μM) than CONLD-BH (-2.5 ± 1.2 μM; Δ177%; <italic>p</italic> &lt; 0.001), but was unchanged between FLK (2.0 ± 1.6 μM) and FLK-BH (0.82 ± 1.4 μM; <italic>p</italic> = 0.979). Δ[HHb] was higher in CONLD (7.3 ± 1.8μM) than CONLD-BH (7.0 ± 2.0μM; Δ4%; <italic>p</italic> = 0.011) and lower in FLK (6.7 ± 1.8μM) compared to FLK-BH (8.7 ± 2.4 μM; <italic>p</italic> &lt; 0.001). It is suggested that the unchanged VO<sub>2</sub> between CONLD and CONLD-BH was supported by increased deoxygenation as reflected by decreased Δ[Hb<sub>tot</sub>] and blunted Δ[HHb], <italic>via</italic> apneic-driven redistribution of blood flow away from working muscles, which was reflected by the decreased S<sub>at</sub>O<sub>2</sub>. However, the preserved VO<sub>2</sub> during FLK-BH vs. FLK has been underpinned by an increase in [HHb].</p>