The effect of resting blood flow occlusion on exercise tolerance and W′

Abstract

It has previously been postulated that the anaerobic work capacity (W=) may be utilized during resting blood flow occlusion in the absence of mechanical work. We tested the hypothesis that W= would not be utilized during an initial range of time following the onset of resting blood flow occlusion, after which W= would be utilized progressively more. Seven men completed blood flow occlusion constant power severe intensity handgrip exercise to task failure following 0, 300, 600, 900, and 1,200 s of resting blood flow occlusion. The work performed above critical power (CP) was not significantly different between the 0-, 300-, and 600-s conditions and was not significantly different from the total W= available. Significantly less work was performed above CP during the 1,200-s condition than the 900-s condition (P Ͻ 0.05), while both conditions were significantly less than the 0-, 300-, and 600-s conditions (P Ͻ 0.05). The work performed above CP during these conditions was significantly less than the total W= available (P Ͻ 0.05). The utilization of W= during resting blood flow occlusion did not begin until 751 Ϯ 118 s, after which time W= was progressively utilized. The current findings demonstrate that W= is not utilized during the initial ϳ751 s of resting blood flow occlusion, but is progressively utilized thereafter, despite no mechanical work being performed. Thus, the utilization of W= is not exclusive to exercise, and a constant amount of work that can be performed above CP is not the determining mechanism of W=.W=; critical power; exercise tolerance; blood flow occlusion SEVERE INTENSITY EXERCISE tolerance is defined by a hyperbolic relationship between power and time to exhaustion (21,22,26), and this power-duration relationship is of paramount importance in the field of integrative physiology (25). Critical power (CP) is the power asymptote of this relationship and is the defining boundary between the heavy-and severe-exercise intensity domains (2,6,17,24,26), while the anaerobic work capacity (W=) dictates the tolerable duration of severe intensity exercise (5, 10, 13, 19 -21). The mechanisms determining W= are associated with the depletion of intramuscular energy stores [e.g., phosphocreatine (PCr), glycogen, and O 2 stores] (17, 19 -21) and the accumulation of fatigue-inducing metabolites [e.g., inorganic phosphate (Pi) and hydrogen ions (H ϩ )] (5, 10, 13, 17). Thus, the magnitude of the W= is related to factors that may constrain or arise from these alterations in the myofiber milieu, such as the breadth of the severe intensity domain, the magnitude of the oxygen uptake slow component, and the development of fatigue (3,4,23,30,31 [PCr] depletion for the same duration of resting blood flow occlusion. These findings suggest that resting metabolism is maintained via aerobic energy production utilizing tissue oxygen stores over the initial several minutes of resting blood flow occlusion, after which resting metabolism must be maintained via supplemental anaerobic energy production. The depletion of int...

Critical Power

“…70). In agreement with this schema, when Broxterman et al (14) applied the graphical Wagner analysis (80) to the increased peak V̇ O 2 they noted that the DO 2 measured during the 20% duty cycle condition contributed ~3-fold more to the greater V̇ O 2 peak than did the rise in perfusive O 2 conductance.…”

“…When the power-duration curve is measured, W′ has units of work, and thus only a small jump of logic is required to extrapolate this “amount of work” to a biological equivalent of stored energy. The early work of Monod and Scherrer (61) implied that this stored energy was of non-oxidative origin: a proposal recently supported by Broxterman et al (12,14) using occluded handgrip exercise. Intramuscular energy stores such as muscle glycogen and PCr are obvious targets, and indeed the cycle-ergometry W′ is increased following creatine supplementation (58,c.f., 101) and decreased following glycogen depletion (59).…”

Influence of blood flow occlusion on muscular recruitment and fatigue during maximal‐effort small muscle‐mass exercise

“…P i and H + ) are described by the mathematical curvature constant ( W ′) of the intensity‐duration relationship that exists above CP (Monod & Scherrer, 1965; Broxterman et al . 2015 a , b ; Poole et al . 2016).…”

Prediction of Critical Power and W′ in Hypoxia: Application to Work-Balance Modelling

“…Collectively, these findings have led to the theory that within a given task, peripheral muscle fatigue may be regulated via group III/IV afferent feedback, which limits central motor drive to the locomotor muscle (Hureau et al, 2016 ). The existence of such a feedback loop might explain why W′ appears to resemble a fixed capacity within a given task (Broxterman et al, 2015 ). From a mathematical perspective, a fixed value of W′ allows performance during high-intensity tasks to be predicted using the 2-parameter CP model.…”