The effect of ischaemic preconditioning on central and peripheral fatiguing mechanisms in humans following sustained maximal isometric exercise

Abstract

Ischaemic preconditioning (IPC) is thought to inhibit neural feedback from metabolically sensitive muscle afferents during exercise. It was hypothesized that IPC could affect mechanisms associated with centrally mediated fatigue after a maximally fatiguing protocol. Eleven resistance-trained men completed three 2 min maximal voluntary contractions (MVCs) via an isometric leg extension preceded by treatments of IPC (three bouts of 5 min bilateral leg occlusions at 220 mmHg), SHAM (three bouts of 5 min at 20 mmHg) or CON (30 min passive rest). Femoral nerve stimulation was used to explore central and peripheral fatigue pathways. These pathways were profiled at baseline (BL), before the 2 min MVC (Pre) and 10 s afterwards (Post). Tissue oxygenation was measured throughout the 2 min MVCs via near-infrared spectroscopy. The Pre to Post MVC (-71 ± 56 Nm; d = 1.33 ± 0.51, P < 0.01) and twitch torque (-51 ± 20 Nm; d = 3.76 ± 0.84, P < 0.01) levels declined without differences between conditions (MVC, P = 0.67; twitch torque, P = 0.39). Voluntary activation was also unaffected by condition (P = 0.80). Peak deoxyhaemoglobin concentrations were elevated in the IPC trials relative to CON (3.7 ± 3.0 μmol l ; d = 1.02 ± 0.46, P < 0.01) and SHAM (3.0 ± 3.7 μmol l ; d = 0.82 ± 0.57, P < 0.05). These findings demonstrate that IPC does not affect central or peripherally mediated mechanisms of fatigue during a sustained 2 min maximal effort isometric leg-extension task.

The effect of IPC on central and peripheral fatiguing mechanisms in humans following maximal single limb isokinetic exercise

“…Additionally, and in contrast to our previous findings under isometric conditions (Halley et al. ), IPC did not increase hemoglobin volume or accelerate oxygen dissociation (Table ). We believe this disparate outcome in tissue saturation kinetics may be related to the severity of peripheral fatigue induced by the isometric protocol.…”

“…; Halley et al. ), and theoretically allow the IPC to promote the acute upregulation of vasodilatory factors such as adenosine and nitric oxide (Horimoto et al. ; Kontos ; Kimura et al.…”

“…Despite the shorter duration of the isometric protocol (2 vs. 3 min) (Halley et al. ), declines in muscle contractility were far greater than in the dynamic leg extension protocol (RT ~ 32% lower and ½ RT ~ 33% longer) (Halley et al. ).…”

“…neural drive) associated with maintaining task performance (Halley et al. ). Contrary to previous reports (Cruz et al.…”

“…A notable point of difference between these studies, however, was our use of a static, prolonged maximal voluntary contraction (Halley et al. ) while the cycling tasks were more dynamic in nature (Cruz et al. , ).…”