Purpose: To assess tissue oxygenation, along with metabolic and physiological responses during blood flow restriction (BFR, bilateral vascular occlusion) and systemic hypoxia conditions during submaximal leg- versus arm-cycling exercise. Methods: In both legs and arms, 4 randomized sessions were performed (normoxia 400 m, fraction of inspired oxygen [FIO2] 20.9% and normobaric hypoxia 3800 m, FIO2 13.1% [0.1%]; combined with BFR at 0% and 45% of resting pulse elimination pressure). During each session, a single 6-minute steady-state submaximal exercise was performed to measure physiological changes and oxygenation (near-infrared spectroscopy) of the muscle tissue in both the vastus lateralis (legs) and biceps brachii (arms). Results: Total hemoglobin concentration ([tHb]) was 65% higher (P < .001) in arms versus legs, suggesting that arms had a greater blood perfusion capacity than legs. Furthermore, there were greater changes in tissue blood volume [tHb] during BFR compared with control conditions (P = .017, F = 5.45). The arms elicited 7% lower tissue saturation (P < .001) and were thus more sensitive to the hypoxia-induced reduction in oxygen supply than legs, no matter the condition. This indicates that legs and arms may elicit different regulatory hemodynamic mechanisms (ie, greater blood flow in arms) for limiting the decreased oxygen delivery during exercise with altered arterial oxygen content. Conclusions: The combination of BFR and/or hypoxia led to increased [tHb] in both limbs likely due to greater vascular resistance; further, arms were more responsive than legs. This possibly influences the maintenance of oxygen delivery and enhances perfusion pressure, suggesting greater vascular reactivity in arms than in legs.
Sarah J. Willis, Grégoire P. Millet and Fabio Borrani
Sarah J. Willis, Jules Gellaerts, Benoît Mariani, Patrick Basset, Fabio Borrani and Grégoire P. Millet
Purpose: To examine the net oxygen cost, oxygen kinetics, and kinematics of level and uphill running in elite ultratrail runners. Methods: Twelve top-level ultradistance trail runners performed two 5-min stages of treadmill running (level, 0%, men 15 km·h−1, women 13 km·h−1; uphill, 12%, men 10 km·h−1, women 9 km·h−1). Gas exchanges were measured to obtain the net oxygen cost and assess oxygen kinetics. In addition, running kinematics were recorded with inertial measurement unit motion sensors on the wrist, head, belt, and foot. Results: Relationships resulted between level and uphill running regarding oxygen uptake (
Joana F. Reis, Gregoire P. Millet, Davide Malatesta, Belle Roels, Fabio Borrani, Veronica E. Vleck and Francisco B. Alves
The aim of this study was to compare VO2 kinetics during constant power cycle exercise measured using a conventional facemask (CM) or a respiratory snorkel (RS) designed for breath-by-breath analysis in swimming.
VO2 kinetics parameters—obtained using CM or RS, in randomized counterbalanced order—were compared in 10 trained triathletes performing two submaximal heavy-intensity cycling square-wave transitions. These VO2 kinetics parameters (ie, time delay: td1, td2; time constant: τ1, τ2; amplitude: A1, A2, for the primary phase and slow component, respectively) were modeled using a double exponential function. In the case of the RS data, this model incorporated an individually determined snorkel delay (ISD).
Only td1 (8.9 ± 3.0 vs 13.8 ± 1.8 s, P < .01) differed between CM and RS, whereas all other parameters were not different (τ1 = 24.7 ± 7.6 vs 21.1 ± 6.3 s; A1 = 39.4 ± 5.3 vs 36.8 ± 5.1 mL·min−1·kg−1; td = 107.5 ± 87.4 vs 183.5 ± 75.9 s; A2' (relevant slow component amplitude) = 2.6 ± 2.4 vs 3.1 ± 2.6 mL·min−1·kg−1 for CM and RS, respectively).
Although there can be a small mixture of breaths allowed by the volume of the snorkel in the transition to exercise, this does not appear to significantly influence the results. Therefore, given the use of an ISD, the RS is a valid instrument for the determination of VO2 kinetics within submaximal exercise.