Remote ischemic preconditioning increases accumulated oxygen deficit in middle-distance runners

Determining minimum cuff pressure required to reduce arterial blood flow at rest

The aim of our study was to determine the minimum cuff pressure to induce alterations in the brachial and popliteal blood flow (BF). Forty-two healthy men underwent an incremental cuff pressure protocol at rest. The cuff was positioned at the proximal part of the right arm (9 cm width, brachial artery) and thigh (13 cm width, superficial femoral artery) in a randomized order. Pressure increments started at 0 mmHg, increased by 20 mmHg up to 100 mmHg, and then by 10 mmHg until total occlusion of BF. Each pressure was held for 30 s to stabilize BF and measurements were carried out on brachial (BA) and popliteal (PA) arteries using a 2-D B-mode ultrasound. Mean arterial occlusion pressure (AOP) was 161 ± 18 mmHg in BA and 150 ± 15 mmHg for the PA. At 20-100 mmHg, the mean BF changes were 4% (BA) and 11% (PA), without significant BF reductions compared to baseline values. Reductions in BF vs. baseline (p < 0.05) were found from 120 mmHg (BA) and 110 mmHg (PA) cuff pressures. Calculations of the minimal clinically important differences showed meaningful changes beginning at 110 mmHg for BA and 100 mmHg for PA. Experimental approaches requiring BF restriction should use cuff pressures greater than 69% (BA) and 67% (PA) of AOP to promote significant reductions in blood flow.

The effect of ischemic preconditioning on physical fitness and performance: a meta-analysis in healthy adults

PURPOSE

This meta-analysis aims to assess the impact of ischemic preconditioning (IPC) on physical fitness and performance, with a focus on its specific role in aerobic endurance, anaerobic endurance, explosive power and strength.

METHODS

Systematic searches were conducted across multiple databases (CNKI, CBM, Cochrane Library, Web of Science, PubMed, and Embase) up to September 6, 2023. We included studies that employed randomized controlled trial methods and sham ischemic preconditioning as the placebo group, and two reviewers independently screened literature and extracted data, using Review Manager 5.3 for analysis.

RESULTS

This meta-analysis comprises 27 articles with 405 individuals, selected according to specified criteria. IPC significantly increased the blood lactate concentration after anaerobic speed endurance exercise (MD = 0.74, P = 0.03), the blood lactate concentration after incremental exercise (MD = 0.49, P = 0.04), the blood lactate concentration after muscular endurance exercise (MD = 0.68, P = 0.02), and the one-repetition maximum (MD = 1.38, P = 0.00001). Furthermore, it also significantly shortened completion time of the exercises primarily powered by glycolysis (MD =  - 0.49, P = 0.01) and completion time of the exercises primarily powered by aerobic system (MD =  - 7.27, P = 0.05), while marginally prolonging time to exhaustion (MD = 22.68, P = 0.08). However, IPC had no significant effect on maximum oxygen uptake, blood lactate concentration in fixed-load aerobic endurance exercise, peak power, or peak aerobic power, nor on completion time of the exercises primarily powered by phosphagen system.

CONCLUSION

IPC could serve as a method to enhance physical performance, particularly for exercises primarily powered by aerobic system and glycolysis. Future research might explore how various cycles, locations, and widths of IPC affect the physical performance of participants with different activity levels.

Effect of Ischemic Preconditioning on Endurance Running Performance in the Heat

Ischemic preconditioning (IPC) is a strategy that may enhances endurance performance in thermoneutral environments. Exercising in the heat increases thermoregulatory and cardiovascular strain, decreasing endurance performance. The current study aimed to determine whether IPC administration improves endurance performance in the heat. In a randomized crossover design, 12 healthy subjects (V̇O2max: 54.4 ± 8.1 mL·kg-1·min-1) underwent either IPC administration (220 mmHg) or a sham treatment (20 mmHg), then completed a moderate-intensity 6-min running (EX1) and a high-intensity time-to-exhaustion running test (EX2) in a hot environment (35 °C, 50 % RH). Cardiac function, oxygen consumption (V̇O2), and core body temperature (TCORE) were measured. During EX2, IPC administration increased the total running time in the heat compared to the sham treatment (IPC: 416.4 ± 61.9 vs. sham 389.3 ± 40.7 s, P = 0.027). IPC administration also increased stroke volume (IPC: 150.4 ± 17.5 vs. sham: 128.2 ± 11.6 ml, P = 0.008) and cardiac output (IPC: 27.4 ± 1.7 vs. sham: 25.1 ± 2.2 ml min-1, P = 0.007) during 100% isotime of EX2. End-exercise V̇O2 (IPC: 3.72 ± 0.85 vs. sham: 3.54 ± 0.87 L·min-1, P = 0.017) and slow phase amplitude (IPC: 0.57 ± 0.17 vs. sham: 0.72 ± 0.22 L·min-1, P = 0.016) were improved. When compared with the baseline period, an increase in TCORE was less in the IPC condition during EX1 (IPC: 0.18 ± 0.06 vs. sham: 0.22 ± 0.08 °C, P = 0.005) and EX2 (IPC: 0.87 ± 0.10 vs. sham: 1.03 ± 0.10 °C, P < 0.001). IPC improves high-intensity endurance performance in the heat by 6.9 %. This performance benefit could be associated with improved cardiac and thermoregulatory function engendered by IPC administration.

The effect of ischemic preconditioning on repeated sprint cycling performance: a randomized crossover study

BACKGROUND

Ischemic preconditioning (IPC) has been suggested to improve exercise performance by 1-8%. Prior research concerning its impact on short-duration exercises, such as sprints, has been limited and yielded conflicting results. The aim of this study, which included a non-occlusion-based placebo control, was to determine whether IPC improves repeated sprint performance in a manner that accounted for psychophysiological effects.

METHODS

Twenty-two healthy males participated in this study, which employed a randomized crossover design. Following the 10-min baseline period, participants received intervention under four different conditions: 1) no-intervention control (CON); 2) non-occlusion-based placebo control (SHAM); 3) remote IPC (RIPC); and 4) local IPC (LIPC). Participants then performed a standardized repeated sprint cycling (5×10s maximal cycling sprint, separated by a 40-s rest in each set).

RESULTS

Repeated sprint performance, as indexed by average power output, peak power output, and total work, the improvement was observed in the RIPC and LIPC during the initial phase (set 1-3) when compared with CON (P<0.05). SHAM condition also showed an increase in peak power output in the set 1 (CON 9.97±1.05 vs. SHAM 10.30±1.13 w/kg, P<0.05), which may represent a psychophysiological component in the IPC-induced improvement. Higher lactate concertation was found in the SHAM and LIPC groups, than in the CON group, 5 minutes after the exercise (CON 15.72±0.68 vs. SHAM 16.82±0.41 vs. LIPC 17.19±0.39 mmol/L, P<0.0001 for both, respectively).

CONCLUSIONS

In conclusion, LIPC enhanced repeated sprint cycling performance during the initial phase, beyond what could be accounted for entirely by a psychophysiological effect. The improvement associated with RIPC, however, did not surpass the effect of a placebo intervention.

Improvement of restless leg syndrome in maintenance hemodialysis patients with limb ischemic preconditioning: a single-center randomized controlled clinical trial

OBJECTIVE

This study evaluated the efficacy and safety of limb ischemic preconditioning (LIPC) in treating restless leg syndrome (RLS) in maintenance hemodialysis (MHD) patients.

METHODS

A total number of 45 patients participated in the study. They were randomly divided into LIPC group and control group. The LIPC was performed by inflating the limb ischemic preconditioning training device in the patient's thigh to 200 mmHg to create transient ischemia, whereas control group inflated the device to 20 mmHg. International Restless Legs Syndrome (IRLS), Clinical Global Impression Scale (CGI-S), and Medical Outputs Study Sleep Scale were employed to evaluate LIPC effectiveness. The primary endpoint was the 'rate of clinical improvement in RLS severity', defined as the percentage of patients who had an IRLS score decrease of ≥5 points in each group.

RESULTS

After intervention, the rate of clinical improvement in RLS severity was 56.5% in the LIPC group and 13.6% in the control group (13 (56.5) vs 3 (13.6), p = 0.003). In addition, the LIPC group's IRLS, CGI-S scores, the sleep disturbance and somnolence scores showed a significant downward trend compared to the control group (-5.5 ± 5.3 vs - 1.0 ± 3.8, p = 0.002; -1.7 ± 1.2 vs - 0.5 ± 1.4, p = 0.003; -15.5 ± 17.8 vs 3.7 ± 12.0, p < 0.001; -9.9 ± 18.8 vs - 2.4 ± 8.6, p = 0.003). During the study, there were no serious adverse event in any of the patients.

CONCLUSIONS

LIPC could be employed to effectively and safely alleviate the RLS symptoms in MHD patients.

Pulmonary functions and anthropometric parameters of young male and female adults participating in moderate aerobic exercise

Respiratory disorders may be one of the adverse effects of sedentary lifestyle. This study investigated respiratory functions (FEV1, FVC and PEFR) and anthropometric parameters (body weight and body mass index) of healthy young males and females participating in moderate aerobic exercise. Forty young healthy untrained non-athletes, twenty males and twenty females (age, 25 ± 5.6 years; body weight, 65 ± 4.0 kg; body height, 176.9 ± 2.5 cm) volunteered to participate in this study. The exercise regimen was of moderate intensity lasting for 20 min daily on a treadmill consistently at the speed of 13 km/h for 14 days. The weight and height of participants were measured using medical scale and wall-mounted stadiometer respectively. The forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and peak expiratory flow rate (PEFR) were assessed using digital spirometer. The results showed a significant (p < 0.05) decrease in body weight and body mass index of female participants after 14 days of exercise regimen. The FEV1, FVC and PEFR were significantly increased (p < 0.05) in both male and female subjects after exercise. The Pearson correlation showed a significant (p < 0.05) positive correlation between BMI with FEVI/FVC% in female participants. There was an increase in calories burnt from day 4 of the study in both male and female participants. It is concluded that moderate aerobic exercise improved respiratory functions (FEV1, FVC and PEFR) in both male and female subjects with greater improvement in females while reducing body weight and body mass index in females.

Ischemic Preconditioning Acutely Improves Functional Sympatholysis during Handgrip Exercise in Healthy Males but not Females

PURPOSE

Ischemic preconditioning (IPC), a procedure that involves the cyclic induction of limb ischemia and reperfusion via tourniquet inflation, has been reported to improve exercise capacity and performance, but the underlying mechanisms remain unclear. During exercise, sympathetically mediated vasoconstriction is dampened in active skeletal muscle. This phenomenon, termed functional sympatholysis, plays a critical role in maintaining oxygen delivery to working skeletal muscle and may contribute to determining exercise capacity. Herein, we investigate the effects of IPC on functional sympatholysis in humans.

METHODS

In 20 (10M/10F) healthy young adults, forearm blood flow (Doppler ultrasound) and beat-to-beat arterial pressure (finger photoplethysmography) were measured during lower body negative pressure (LBNP; -20 mm Hg) applied at rest and simultaneously during rhythmic handgrip exercise (30% maximum contraction) before and after local IPC (4 × 5-min 220 mm Hg) or sham (4 × 5-min 20 mm Hg). Forearm vascular conductance (FVC) was calculated as forearm blood flow/mean arterial pressure and the magnitude of sympatholysis as the difference of LBNP-induced changes in FVC between handgrip and rest.

RESULTS

At baseline, LBNP decreased FVC (females [F] = ∆-41% ± 19%; males [M] = ∆-44% ± 10%), and these responses were attenuated during handgrip (F = ∆-8% ± 9%; M = ∆-8% ± 7%). After IPC, LBNP induced similar decreases in resting FVC (F = ∆-37% ± 19%; M = ∆-44% ± 13%). However, during handgrip, this response was further attenuated in males (∆-3% ± 9%, P = 0.02 vs pre) but not females (∆-5% ± 10%, P = 0.13 vs pre), which aligned with an IPC-mediated increase in sympatholysis (M-pre = 36% ± 10% vs post = 40% ± 9%, P = 0.01; F-pre = 32% ± 15% vs post = 32% ± 14%, P = 0.82). Sham IPC had no effect on any variables.

CONCLUSIONS

These findings highlight a sex-specific effect of IPC on functional sympatholysis and provide evidence of a potential mechanism underlying the beneficial effects of IPC on human exercise performance.

Potential physiological responses contributing to the ergogenic effects of acute ischemic preconditioning during exercise: A narrative review

Ischemic preconditioning (IPC) has been reported to augment exercise performance, but there is considerable heterogeneity in the magnitude and frequency of performance improvements. Despite a burgeoning interest in IPC as an ergogenic aid, much is still unknown about the physiological mechanisms that mediate the observed performance enhancing effects. This narrative review collates those physiological responses to IPC reported in the IPC literature and discusses how these responses may contribute to the ergogenic effects of IPC. Specifically, this review discusses documented central and peripheral cardiovascular responses, as well as selected metabolic, neurological, and perceptual effects of IPC that have been reported in the literature.

Ischemic Preconditioning with High and Low Pressure Enhances Maximum Strength and Modulates Heart Rate Variability

Background: The application of ischemic preconditioning (IPC) to resistance exercise has attracted some attention, owing to increases in muscle performance. However, there is still no consensus on the optimal occlusion pressure for this procedure. This study compared the acute effects of IPC with high and low pressure of occlusion on upper and lower limb maximal strength and heart rate variability in recreationally trained individuals. Methods: Sixteen recreationally trained men (25.3 ± 1.7 years; 78.4 ± 6.2 kg; 176.9 ± 5.4 cm; 25.1 ± 1.5 m2 kg−1) were thoroughly familiarized with one repetition maximum (1 RM) testing in the following exercises: bench press (BP), front latissimus pull-down (FLPD), and shoulder press (SP) for upper limbs, and leg press 45º (LP45), hack machine (HM), and Smith Squat (SS) for lower limbs. The 1 RM exercises were then randomly performed on three separate days: after a high pressure (220 mmHg, IPChigh) and a low pressure (20 mmHg, IPClow) IPC protocol and after no intervention (control, CON). Heart rate variability was also measured at rest, during and after the entire IPC protocol, and after the exercises. Results: Maximal strength was significantly (p < 0.05) higher in both IPChigh and IPClow compared with CON in all upper- and lower-limb exercises. There was no difference between the two experimental conditions. No significant differences were found in the comparison across the different experimental conditions for LFnu, HFnu, LF/HF ratio, and RMSSDms. Conclusions: IPC performed with both high and low pressures influenced heart rate variability, which may partly explain the maximal strength enhancement.

Effect of ischemic preconditioning on maximum accumulated oxygen deficit in 400-meter runners

The main aim of this study was to examine the influence of ischemic preconditioning (IPC) on maximal accumulated oxygen deficit (MAOD). We conducted a three-arm and assessor-blinded randomized, controlled crossover study. Sixteen 400-meter running male athletes (19.9±1.3 years; 1.78±0.05 m; 67.9±5.5 kg) completed three supramaximal intensity tests separated with Control, Local (legs), and Remote (arms) IPC interventions. IPC was induced on the limbs on both sides (4×5 min alternating unilateral occlusion 220 mmHg and reperfusion; arms or thighs; right side first) before participants performed the supramaximal intensity test on a treadmill at 110% VO_2max intensity to exhaustion. During each test, indices of respiratory gas exchange, blood lactate, and heart rate were determined. The MAOD was calculated as the difference between the theoretical VO₂ demand and the actual VO₂ during the supramaximal intensity test. Differences from three trials were analyzed using ANOVA with repeated measures. IPC increased MAOD (RIPC, 59±17 ml/kg/min, p=0.018; LIPC, 57±15 ml/kg/min, p=0.037; p<0.05) compared with Control (49±9 ml/kg/min). Time to exhaustion was enhanced after IPC (Control: 257.2±69.5 s, RIPC, 292.3±66.6 s, p= 0.048; LIPC, 291.6±79.2 s, p=0.042; p<0.05). In contrast, the enhancements of RIPC and LIPC trials were similar (p=1.000). Blood lactate concentrations were similar across the three intervention conditions (p>0.05). Acute IPC improved MAOD and supramaximal intensity exercise capacity in 400-meter running athletes. The increased MAOD indicated greater anaerobic capacity, which can be the potential mediator for improvement in exhaustion time.

Remote Ischemic Preconditioning Reduces Marathon-Induced Oxidative Stress and Decreases Liver and Heart Injury Markers in the Serum

Clinical studies continue to provide evidence of organ protection by remote ischemic preconditioning (RIPC). However, there is lack of insight into impact of RIPC on exercise-induce changes in human organs' function. We here aimed to elucidate the effects of 10-day RIPC training on marathon-induced changes in the levels of serum markers of oxidative stress, and liver and heart damage. The study involved 18 male amateur runners taking part in a marathon. RIPC training was performed in the course of four cycles, by inflating and deflating a blood pressure cuff at 5-min intervals (RIPC group, n=10); the control group underwent sham training (n=8). The effects of RIPC on levels of oxidative stress, and liver and heart damage markers were investigated at rest after 10 consecutive days of training and after the marathon run. The 10-day RIPC training decreased the serum resting levels of C-reactive protein (CRP), alanine transaminase (ALT), γ-glutamyl transpeptidase (GGT), and malondialdehyde (MDA). After the marathon run, creatinine kinase MB (CK-MB), lactate dehydrogenase (LDH), cardiac troponin level (cTn), aspartate aminotransferase (AST), alkaline phosphatase (ALP), ALT, total bilirubin (BIL-T), and MDA levels were increased and arterial ketone body ratio (AKBR) levels were decreased in all participants. The changes were significantly diminished in the RIPC group compared with the control group. The GGT activity remained constant in the RIPC group but significantly increased in the control group after the marathon run. In conclusion, the study provides evidence for a protective effect of RIPC against liver and heart damage induced by strenuous exercise, such as the marathon.

Effect of 10 consecutive days of remote ischemic preconditioning on local neuromuscular performance

BACKGROUND

Most studies focus on the effects of a single remote ischemic preconditioning (RIPC) session on performance. However, the training-like effect of repeat RIPC sessions performed on consecutive days could potentially be even more beneficial to neuromuscular performance than a single RIPC session. Therefore, aim of the study was to assess the impact of 10 days of RIPC on local neuromuscular performance.

METHODS

Thirty-seven male participants performed 10 days of either RIPC or sham-controlled condition. Before and after procedure, the maximal voluntary contraction and muscle fatigue were assessed by dynamometry and surface electromyography (EMG) of the isometric extension of the knee joint. The following neuromuscular outcomes were investigated: peak torque (PKTQ); rate of force development (RTD); time to failure; and the slope of median frequency of power spectrum (MDF) and EMG amplitude.

RESULTS

After RIPC, while there was no change in PKTQ and time to failure, the late RTD and MDF slope were significantly affected. The RTD at 0-100 and 0-200 ms showed 24 and 16% increase, respectively, while the MDF slope showed 24% decrease in rectus femoris.

CONCLUSIONS

10 days of RIPC induced neuromuscular performance changes in the quadriceps muscle. Even though there were no changes in task to failure performance, RIPC showed EMG changes limited to rectus femoris and increased late RTD in MVC task.

Methodological Variations Contributing to Heterogenous Ergogenic Responses to Ischemic Preconditioning

Ischemic preconditioning (IPC) has been repeatedly reported to augment maximal exercise performance over a range of exercise durations and modalities. However, an examination of the relevant literature indicates that the reproducibility and robustness of ergogenic responses to this technique are variable, confounding expectations about the magnitude of its effects. Considerable variability among study methodologies may contribute to the equivocal responses to IPC. This review focuses on the wide range of methodologies used in IPC research, and how such variability likely confounds interpretation of the interactions of IPC and exercise. Several avenues are recommended to improve IPC methodological consistency, which should facilitate a future consensus about optimizing the IPC protocol, including due consideration of factors such as: location of the stimulus, the time between treatment and exercise, individualized tourniquet pressures and standardized tourniquet physical characteristics, and the incorporation of proper placebo treatments into future study designs.

Reduced effect of ischemic preconditioning against endothelial ischemia-reperfusion injury with cardiovascular risk factors in humans

The extent that clustered CVD risk factors interfere with ischemic preconditioning (IPC) to protect against microvascular endothelial dysfunction with ischemia-reperfusion (I/R) injury in humans is unclear. We hypothesized that adults with a clustered burden of ≥3 CVD risk factors would demonstrate a reduced capacity of IPC to protect endothelial function with I/R injury. Twenty-two (age: 45 ± 14 year) adults [12 healthy controls; 10 raised risk (10-year FRS risk score ~3%)] were studied using a 2 × 2 randomized cross-over design. Pulse arterial tonometry was used to assess microvascular endothelium-dependent vasodilation during reactive hyperemia in response to endothelial I/R injury (20 min brachial artery occlusion/45 min reperfusion) that was preceded by remote IPC (3 × 5 min ischemia/reperfusion) or mock IPC. In both groups, microvascular reactive hyperemia was reduced ~20% (both P < 0.01) after endothelial I/R injury without remote IPC. However, in control subjects remote IPC prevented endothelial I/R injury (from baseline reactive hyperemic ratio: 2.1 ± 0.4 AU to post I/R injury: 2.5 ± 0.5 AU; P = 0.09). In contrast, the reactive hyperemia ratio in raised risk subjects was significantly reduced from 2.2 ± 0.6 AU to 1.9 ± 0.5 AU (P = 0.0087) despite attempts to induce protection by remote IPC, with the magnitude of reduction similar to their mock IPC trial. The magnitude of remote IPC-mediated endothelial protection against I/R injury was inversely related to the number of risk factors. CVD risk factors diminish the effect of IPC to protect the microvasculature from I/R injury in humans. Translating IPC to clinical practice for vasculoprotection will continue to be challenging in patients with increased CVD risk.