Ischemic preconditioning accelerates muscle deoxygenation dynamics and enhances exercise endurance during the work-to-work test

Abstract

Ischemic preconditioning (IPC) improves maximal exercise performance. However, the potential mechanism(s) underlying the beneficial effects of IPC remain unknown. The dynamics of pulmonary oxygen uptake (VO2) and muscle deoxygenation during exercise is frequently used for assessing O2 supply and extraction. Thus, this study examined the effects of IPC on systemic and local O2 dynamics during the incremental step transitions from low- to moderate- and from moderate- to severe-intensity exercise. Fifteen healthy, male subjects were instructed to perform the work-to-work cycling exercise test, which was preceded by the control (no occlusion) or IPC (3 × 5 min, bilateral leg occlusion at >300 mmHg) treatments. The work-to-work test was performed by gradually increasing the exercise intensity as follows: low intensity at 30 W for 3 min, moderate intensity at 90% of the gas exchange threshold (GET) for 4 min, and severe intensity at 70% of the difference between the GET and VO2 peak until exhaustion. During the exercise test, the breath-by-breath pulmonary VO2 and near-infrared spectroscopy-derived muscle deoxygenation were continuously recorded. Exercise endurance during severe-intensity exercise was significantly enhanced by IPC. There were no significant differences in pulmonary VO2 dynamics between treatments. In contrast, muscle deoxygenation dynamics in the step transition from low- to moderate-intensity was significantly faster in IPC than in CON (27.2 ± 2.9 vs. 19.8 ± 0.9 sec, P < 0.05). The present findings showed that IPC accelerated muscle deoxygenation dynamics in moderate-intensity exercise and enhanced severe-intensity exercise endurance during work-to-work test. The IPC-induced effects may result from mitochondrial activation in skeletal muscle, as indicated by the accelerated O2 extraction.

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

“…Occlusion pressure for the group was between 160-170 mmHg, therefore 220 mmHg ensured the pressure was at least 50 mmHg above systolic blood pressure. This pressure is supported by similar IP literature (Bailey, Jones, et al 2012;de Groot et al 2010;Sharma et al 2015), however recent near infrared spectroscopy data indicates arterial pulses may be observed up to 300 mmHg (Kido et al 2015). Pilot data, collected using Doppler ultrasound, as well as published literature (Gibson et al 2013), identified 50 mmHg as an appropriate control pressure, as it provides a sensation of pressure, without impairing arterial flow.…”

Ischemic preconditioning: Potential impact on exercise performance and underlying mechanisms

“…IPC had no beneficial effects on the mean V ・ O2, V ・ E, and HR during a 5 km running time trial 22) , the submaximal V ・ O2 during maximal incremental leg cycling 13,14) , or during leg cycling at an exercise intensity of 90% V ・ O2peak at the gas exchange threshold 12) . However, IPC decreased LA at the submaximal running speed compared to SHAM 21) .…”

“…In fact, the maximal or peak oxygen uptake (V ・ O2max or V ・ O2peak) was not improved with IPC during maximal incremental exercise and during constant-load leg cycling at a work load of 130% peak power 10) or at 70% of the difference between the V ・ O2 at the gas exchange threshold and V ・ O2peak 12) . Likewise, the heart rate peak (HRpeak) was not increased with IPC during maximal incremental leg cycling 13) , during constant load leg cycling until exhaustion 11,12) , maximal HR during a 5 km running time trial 21) , and 100 m swimming 19) . Additionally, maximum pulmonary ventilation (V ・ Emax) during maximal incremental leg cycling 13,14) was not affected by IPC.…”

“…Findings on the impact of IPC on maximal incremental or constant load cycling performance have been equivocal. IPC prolonged the time to failure during maximal incremental leg cycling 10) and constant load leg cycling 11,12) . Similarly, IPC improved peak power output during maximal incremental leg cycling 10,13) .…”

“…IPC also resulted in increases in HRmax and V ・ Epeak during maximal incremental leg cycling exercise 10) . Because the peak values of blood lactate concentration (LApeak) after exercise may be an indicator of anaerobic capacity, several studies compared the LApeak between IPC and the control (or SHAM), and no effect in LApeak after exercise with IPC was found 4,[9][10][11][12][13][14]18,19,22) . Two studies focused on muscle activity, assessed by electromyography (EMG), between IPC and CON, and no differences in EMG were found during cycle sprints 4) or isometric leg extension 26) .…”