Abstract
The aim was to evaluate changes in peripheral and cerebral oxygenation, cardiorespiratory, and performance differences, as well as neuromuscular fatigue across multiple levels of blood flow restriction (BFR) during a repeated cycling sprint test to exhaustion (RST). Participants performed three RST (10‐sec maximal sprints with 20‐sec recovery until exhaustion) with measurements of power output and V̇O2peak as well as oxygenation (near‐infrared spectroscopy) of the vastus lateralis and prefrontal cortex. Neuromuscular fatigue was assessed by femoral nerve stimulation to evoke the vastus lateralis. Tests were conducted with proximal lower limb bilateral vascular occlusion at 0%, 45%, and 60% of resting pulse elimination pressure. Total work decreased with BFR (52.5 ± 22.9% at 45%, 68.6 ± 32.6% at 60%, P < 0.01 compared with 0%) as V̇O2peak (12.6 ± 9.3% at 45%, 18.2 ± 7.2% at 60%, compared with 0%, P < 0.01). Decreased changes in muscle deoxyhemoglobin (∆[HHb]) during sprints were demonstrated at 60% compared to 0% (P < 0.001). Changes in total hemoglobin concentrations (∆[tHb]) increased at both 45% and 60% compared with 0% (P < 0.001). Cerebral ∆[tHb] increased toward exhaustion (P < 0.05). Maximal voluntary contraction (MVC), voluntary activation level (VAL), and root mean square (RMS)/M‐wave ratio decreased at 60% compared with 0% (P < 0.001, all). MVC and VAL decreased between 45% and 60% (P < 0.05, both). The application of BFR during RST induced greater changes in tissue perfusion (via blood volume, ∆[tHb]) suggesting a possible stimulus for vascular blood flow regulation. Additionally, high‐intensity sprint exercise with partial ischemia may challenge cerebral blood flow regulation and influence local fatigue development due to protection of cerebral function.
Highlights
Repeated sprinting at maximal intensity with incomplete recoveries elicits the early development of fatigue (~33–35% power decrement), impacting performance especially when exercising to exhaustion (Bishop et al 2004)
The study’s main findings were that (1) performance decreased with increased blood flow restriction (BFR), which was concomitant with a decreased peak oxygen consumption; (2) muscle blood volume changes (Δ[tHb]) increased with both levels of BFR while smaller changes in peripheral deoxygenation (Δ[HHb]) were demonstrated with the 60% condition; (3) changes in cerebral blood volume (Δ[tHb]) increased near exhaustion no matter the condition; and (4) the BFR conditions induced large decrements of Maximal voluntary contraction (MVC), voluntary activation level (VAL), and root mean square (RMS)/M-wave
As expected, repeated sprint performance declined as the BFR severity increased
Summary
Repeated sprinting at maximal intensity with incomplete recoveries (work to rest ratio < 1:4) elicits the early development of fatigue (~33–35% power decrement), impacting performance especially when exercising to exhaustion (Bishop et al 2004). The limiting factors at the muscular level encompass (1) muscle excitability due to ionic disturbances (Clausen et al 1998), (2) energy supply from the phosphocreatine availability, as well as anaerobic glycolysis, and oxidative metabolism as the sprints continue (Gaitanos et al 1993). The contribution of these factors limits performance and is exaggerated when there are environmental stresses such as altitude (reduced oxygen availability) (Balsom et al 1994; Brosnan et al 2000).
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