Ischaemic preconditioning does not alter the determinants of endurance running performance in the heat

Purpose: Ischaemic preconditioning (IP) has been shown to be ergogenic for endurance performance in normothermic conditions and alleviate physiological strain under hypoxia, potentially through haemodynamic and/or metabolic mechanisms. Exertional hyperthermia is characterised by competition for blood flow between the muscles and skin, an enhanced metabolic strain and impaired endurance performance. This study investigated the effect of IP on the determinants of endurance performance, through an incremental exercise test in the heat. Method: Eleven males completed two graded exercise tests in the heat (32°C, 62% RH) until volitional exhaustion, preceded by IP (4x5 min 220 mmHg bilateral upper leg occlusion) or a control (CON) condition (4x5-min 50 mmHg bilateral). Result: IP did not improve running speeds at fixed blood lactate concentrations of 2 and 4 mMol.L-1 (p=0.828), or affect blood glucose concentration throughout the trial (mean [±SD]; CON 5.03 [0.94] mMol.L-1, IP 5.47[1.38] mMol.L-1, p=0.260). There was no difference in V̇O2max (CON-55.5 [3.7] mL.kg-1min-1, IP 56.0 [2.6] mL.kg-1min-1, p=0.436), average running economy (CON 222.3 [18.0] mL.kg-1.km-1, IP 218.9 [16.5] mL.kg-1.km-1, p=0.125), or total running time during graded exercise (CON 347 [42] s, IP 379 [68] s, p=0.166). The IP procedure did not change muscle temperature (CON ∆= 0.55 [0.57]°C, IP ∆=0.78 [0.85]°C, p=0.568), but did reduce TCORE during exercise (~-0.1°C, p=0.001). Conclusion: The novel application of IP prior to exercise in the heat, does not enhance the determinants of endurance performance. For events where IP appears ergogenic, muscle warming strategies are unnecessary as IP does not influence deep muscle temperature.