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

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-1 ; d = 1.02 ± 0.46, P < 0.01) and SHAM (3.0 ± 3.7 μmol l-1 ; 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.