Blood-Flow Restricted Warm-Up Alters Muscle Hemodynamics and Oxygenation during Repeated Sprints in American Football Players

Abstract

Team-sport athletes and coaches use varied strategies to enhance repeated-sprint ability (RSA). Aside from physical training, a well-conducted warm-up enhances RSA via increased oxidative metabolism. Strategies that impede blood flow could potentiate the effects of a warm-up due to their effects on the endothelial and metabolic functions. This study investigated whether performing a warm-up combined with blood-flow restriction (WFR) induces ergogenic changes in blood volume, muscle oxygenation, and RSA. In a pair-matched, single-blind, pre-post parallel group design, 15 American football players completed an RSA test (12 × 20 m, 20 s rest), preceded by WFR or a regular warm-up (SHAM). Pressure was applied on the athletes’ upper thighs for ≈15 min using elastic bands. Both legs were wrapped at a perceived pressure of 7 and 3 out of 10 in WFR and SHAM, respectively. Changes in gastrocnemius muscle oxygen saturation (SmO2) and total hemoglobin concentration ([THb]) were monitored with near-infrared spectroscopy. Cohen’s effect sizes (ES) were used to estimate the impact of WFR. WFR did not clearly alter best sprint time (ES −0.25), average speed (ES 0.25), total time (ES −0.12), and percent decrement score (ES 0.39). While WFR did not meaningfully alter average SmO2 and [THb], the intervention clearly increased the maximum [THb] and the minimum and maximum SmO2 during some of the 12 sprint/recovery periods (ES 0.34–1.43). Results indicate that WFR positively alters skeletal muscle hemodynamics during an RSA test. These physiological changes did not improve short-term RSA, but could be beneficial to players during longer activities such as games.

Impact of Active and Passive Hypoxia as Re-Warm-Up Activities on Rugby Players’ Performance

“…Further support for a perfusion-related mechanism is provided by the muscle oxygenation data. In fact, during the RSA test, the mean values of Hb were significantly greater after AH than RH, which probably indicates a greater O 2 delivery to the muscle during the test [27]. This finding is in accordance with a recent study on American football players, where the authors found an enhancement in muscle reoxygenation after a warm-up with local hypoxia (blood flow restriction) during a subsequent RSA test [27].…”

“…In fact, during the RSA test, the mean values of Hb were significantly greater after AH than RH, which probably indicates a greater O 2 delivery to the muscle during the test [27]. This finding is in accordance with a recent study on American football players, where the authors found an enhancement in muscle reoxygenation after a warm-up with local hypoxia (blood flow restriction) during a subsequent RSA test [27]. In addition, in the present study, there was a significantly higher muscle deoxygenation of the vastus lateralis during the RSA test after an AH re-warm-up strategy than in AN, RH and RN.…”

Commentary: Active Preconditioning With Blood Flow Restriction or/and Systemic Hypoxic Exposure Does Not Improve Repeated Sprint Cycling Performance

“…We read with great interest the study of Aebi et al (2019) on the lively topic of hypoxic conditioning for sport performance. We congratulate the authors for their excellent work, which confirms, to some extent, some of our previous findings (Fortin and Billaut, 2019), and we also wish to comment on two points of importance: (i) the differences between ischemic preconditioning (IPC) and blood flow restricted exercise (BFR) as well as (ii) the importance of the practical nature of preconditioning protocols (i.e., warm-up) used in sport-oriented studies.…”

“…Hence, we certainly acknowledge the complexity of the experimental design (with separate and combined stresses) used by Aebi et al and appreciate the difficulty of juggling with terms that do not quite qualify to introduce new concepts. To this end, we have proposed the socalled acronym "WFR" to define a blood flow-restricted situation specifically applied to warm-up for preconditioning purposes (Fortin and Billaut, 2019).…”

“…While extensive research has been devoted to improving the effects of a warm-up, the application of blood flow restriction (with its hemodynamic/hypoxic effects mimicking those of high-intensity exercise) is new and appealing. To our best knowledge, our laboratory reported the first data of the effects of a warm-up combined with BFR (Fortin and Billaut, 2019). Warming-up with blood flow restriction (WFR), albeit using elastic bands and a perceived pressure rather than a more expensive cuff system to try and maintain a constant pressure, enhanced muscle hemodynamics and oxygenation (derived from near-infrared spectroscopy) during twelve 20-m running sprints in trained American football players.…”