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An examination of individual responses to ischemic preconditioning and the effect of repeated ischemic preconditioning on cycling performance

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Purpose: To use repeated control trials to measure within-subject variability and assess the existence of responders to ischemic preconditioning (IPC). Secondly, to determine whether repeated IPC can evoke a dosed ergogenic response. Methods: Twelve aerobically fit individuals each completed three control and three IPC 5-km cycling time trials. IPC trials included: (i) IPC 15-min preceding the trial (traditional IPC), (ii) IPC 24-h and 15-min preceding (IPC × 2), (iii) IPC 48-h, 24-h, and 15-min preceding (IPC × 3). IPC consisted of 3 × 5-min cycles of occlusion and reperfusion at the upper thighs. To assess the existence of a true response to IPC, individual performance following traditional IPC was compared to each individual's own 5-km TT coefficient of variation. In individuals who responded to IPC, all three IPC conditions were compared to the mean of the three control trials (CONavg) to determine whether repeated IPC can evoke a dosed ergogenic response. Results: 9 of 12 (75%) participants improved 5-km time (-1.8 ± 1.7%) following traditional IPC, however, only 7 of 12 (58%) improved greater than their own variability between repeated controls (true responders). In true responders only, we observed a significant mean improvement in 5-km TT completion following traditional IPC (478 ± 50 s), IPC × 2 (481 ± 51 s), and IPC × 3 (480.5 ± 49 s) compared to mean CONavg (488 ± 51s; p < 0.006), with no differences between various IPC trials (p > 0.05). Conclusion: A majority of participants responded to IPC, providing support for a meaningful IPC-mediated performance benefit. However, repeated bouts of IPC on consecutive days do not enhance the ergogenic effect of a single bout of IPC.
... Some past research has indicated the potential that there are responders and non-responders to IPC (34,55), which is common with other types of exercise interventions and ergogenic aids (21). More work is needed to understand characteristics of responders to IPC in order to tailor IPC protocols to those most likely to benefit. ...
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Some evidence indicates that ischemic preconditioning (IPC) may positively affect endurance exercise performance, but IPC's effect on running performance is unclear. This study's purpose was to examine the effect of IPC on running performance in recreational runners. Participants (n=12) completed IPC, a sham (SH) condition, and a leg elevation without blood restriction (LE) control condition on separate days (order randomized). For IPC, blood was restricted using blood pressure cuffs inflated to 220 mmHg at the thigh. For SH, the cuffs were inflated to only 20 mmHg. For LE, participants positioned their legs at 90 degrees against a wall while laying supine. The duration of each protocol was 30 minutes (three 5-minute bouts with 5-minute breaks). Following each protocol, participants ran 2.4 kilometers as fast as possible on a motorized treadmill. Run time, heart rate, and perceived exertion were measured and statistically compared, using repeated-measures ANOVA, each 0.8 kilometers. There were no differences in heart rate or time trial performance across protocols (p>0.05; IPC, 612.5±61.2 sec; SH, 608.1±57.9 sec; LE, 612.7±59.1 sec). Rating of perceived exertion at 0.8 kilometers was significantly lower for the IPC protocol than SH in females only (~5.7%, or ~0.8 points on a 6-20 scale; p<0.05). Our IPC protocol did not improve running performance or physiological parameters during a time trial run in recreational runners. The performance benefit seen in this study's most fit individuals suggests that fitness level may influence IPC's efficacy for improving endurance running performance.
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RESUMO: O pré-condicionamento isquêmico [do termo em inglês ischemic preconditioning (IPC)] é uma estratégia caracterizada por breves ciclos de restrição do fluxo sanguíneo seguidos de reperfusão, realizados nos membros superiores ou inferiores com o objetivo de melhorar o desempenho físico. Essa intervenção tem chamado atenção devido a sua característica não invasiva, seu baixo custo e a fácil aplicação. Uma vez que não há um consenso sobre a sua efetividade como uma estratégia ergogênica, o objetivo deste estudo foi investigar o seu estado atual de produção científica, o efeito sobre o desempenho físico e o efeito do nível de treinamento dos participantes e diferentes exercícios/testes utilizados para avaliação do desempenho. Sessenta e sete artigos, envolvendo 984 participantes (177 mulheres) de diferentes níveis de treinamento, preencheram os critérios de inclusão. Sete exercícios (ciclismo, exercício resistido, corrida, natação, patinação, futebol, remo) e cinco níveis de treinamento (destreinados, recreacionalmente treinados, treinados, bem treinados, profissional) foram identificados. A maioria da produção científica sobre IPC e desempenho físico foi publicada a partir de 2015. Mais da metade dos estudos apresentaram um efeito positivo do IPC sobre o desempenho físico (59,7%, n=40). O teste exato de Fischer mostrou que existe uma relação entre o efeito do IPC sobre o desempenho físico e o nível de treinamento dos participantes [X2(8) = 15,149; p = 0,026], mas não entre o efeito do IPC e exercício/teste [X2(12) = 19,528; p = 0,129]. Na última década, houve um aumento substancial na produção cientifica sobre IPC e desempenho físico. Nossos achados sustentam um efeito benéfico do IPC na melhora do desempenho físico, sendo este efeito mais pronunciado em indivíduos destreinados e recreacionalmente treinados, independente do exercício/teste realizado.
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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.
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Purpose: While the possible ergogenic benefits of remote ischemic preconditioning (RIPC) make it an attractive training modality, the mechanisms of action remain unclear. Alterations in neural tone have been demonstrated in conjunction with circulatory occlusion, yet investigation of the autonomic nervous system following RIPC treatment has received little attention. We sought to characterize alterations in autonomic balance to both RIPC and augmented RIPC (RIPC aug) performed while cycling, using acute and sustained autonomic indices. Methods: Thirteen participants (8M:5F) recorded baseline waking heart rate variability (HRV) for 5 days prior to treatment. Participants then completed control exercise (CON), RIPC, and RIPC aug interventions in a randomized cross-over design. Cardiovascular measurements were recorded immediately before and after each intervention at rest, and during an orthostatic challenge. Waking HRV was repeated the morning after each intervention. Results: RIPC resulted in acutely reduced resting heart rates (HR) (∆ − 4 ± 6 bpm, P = 0.02) and suppressed HR 30 s following the orthostatic challenge compared to CON (64 ± 10 vs 74 ± 9 bpm, P = 0.003). RIPC aug yielded elevated HRs compared to CON and RIPC prior to (P = 0.003) and during the orthostatic challenge (P = 0.002). RIPC aug reduced LnSDNN (Baseline 4.39 ± 0.27; CON 4.44 ± 0.39; RIPC 4.41 ± 0.34; RIPC aug 4.22 ± 0.29, P = 0.02) and LnHfa power (Baseline 7.82 ± 0.54; CON 7.73 ± 1.11; RIPC 7.89 ± 0.78; RIPC aug 7.23 ± 0.87, P = 0.04) the morning after treatment compared to all other conditions. Conclusions: Our data suggest that RIPC may influence HR acutely, possibly through a reduction in cardiac sympathetic activity, and that RIPC aug reduces HRV through cardiac vagal withdrawal or increased cardiac sympathetic modulation, with alterations persisting until the following morning. These findings imply a dose-response relationship with potential for optimization of performance.
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PurposeAlthough ischaemic preconditioning (IPC), induced by cycles of transient limb ischaemia and reperfusion, seems to improve exercise performance, the optimal duration of ischaemia–reperfusion cycles is not established. The present study investigated the effect of ischaemia–reperfusion duration within each IPC cycle on performance in a 2000-m rowing ergometer test. Methods After incremental and familiarization tests, 16 trained rowers (mean ± SD: age, 24 ± 11 years; weight, 74.1 ± 5.9 kg; \(\dot{V}{\text{O}}_{{\text{2}}}\) peak, 67.2 ± 7.4 mL·kg−1·min−1) were randomly submitted to a 2000-m rowing test preceded by intermittent bilateral cuff inflation of the lower limbs with three cycles of ischaemia–reperfusion, lasting 5 min (IPC-5) or 10 min (IPC-10) at 220 or 20 mmHg (control). Power output, \(\dot{V}{\text{O}}_{{\text{2}}}\), heart rate, blood lactate concentration, pH, ratings of perceived exertion (RPE), and near-infrared spectroscopy-derived measurements of the vastus lateralis muscle were continuously recorded. ResultsNo differences among treatments were found in the 2000-m test (control: 424 ± 17; IPC-5: 425 ± 16; IPC-10: 424 ± 17 s; P = 0.772). IPC-10 reduced the tissue saturation index and oxy-haemoglobin concentration during exercise compared with control. The power output during the last 100-m segment was significantly lower with IPC-10. The IPC treatments increased the heart rate over the first 500 m and decreased the pH after exercise. No alterations were observed in \(\dot{V}{\text{O}}_{{\text{2}}}\), blood lactate, or RPE among the trials. Conclusion In conclusion, IPC does not improve the 2000-m rowing ergometer performance of trained athletes regardless of the length of ischaemia–reperfusion cycles.
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The concept of personalised nutrition and exercise prescription represents a topical and exciting progression for the discipline given the large inter-individual variability that exists in response to virtually all performance and health related interventions. Appropriate interpretation of intervention-based data from an individual or group of individuals requires practitioners and researchers to consider a range of concepts including the confounding influence of measurement error and biological variability. In addition, the means to quantify likely statistical and practical improvements are facilitated by concepts such as confidence intervals (CIs) and smallest worthwhile change (SWC). The purpose of this review is to provide accessible and applicable recommendations for practitioners and researchers that interpret, and report personalised data. To achieve this, the review is structured in three sections that progressively develop a statistical framework. Section 1 explores fundamental concepts related to measurement error and describes how typical error and CIs can be used to express uncertainty in baseline measurements. Section 2 builds upon these concepts and demonstrates how CIs can be combined with the concept of SWC to assess whether meaningful improvements occur post-intervention. Finally, Section 3 introduces the concept of biological variability and discusses the subsequent challenges in identifying individual response and non-response to an intervention. Worked numerical examples and interactive supplementary material are incorporated to solidify concepts and assist with implementation in practice.
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Introduction: Ischaemic preconditioning (IPC) may enhance endurance performance. No previous study has directly compared distinct IPC protocols for optimal benefit. The aim of this study was to determine whether a specific IPC protocol (i.e. number of cycles, amount of muscle tissue, and local vs remote occlusion) elicits greater performance outcome. Methods: Twelve cyclists performed five different IPC protocols 30-min prior to a blinded 375 kJ cycling time trial (TT) in a laboratory. Responses to traditional IPC (4x5-min legs) were compared to: i. 8x5-min legs and SHAM ("dose-cycles"), ii. 4x5-min unilateral legs ("dose-tissue"), and iii. 4x5-min arms ("remote"). RPE and blood lactate were recorded at each 25% TT completion. Power (watts), heart rate (bpm), and V̇O2 (ml.kg.min(-1)) were measured continuously throughout TT's. Magnitude based inference statistics were employed to compare variable differences to the minimal practically important difference. Results: Traditional IPC was associated with a 17 (0, 34) secs faster TT time compared to SHAM. Applying more "dose-cycles" (8x5-min) had no impact on performance. Traditional IPC was associated with "likely trivial" higher blood lactate and "possibly beneficial" lower V̇O2 responses vs. SHAM. Unilateral IPC was associated with 18 (-11, 48) secs slower performance compared to bilateral ("dose-tissue"). TT times following remote and local IPC were not different [0 (-16, 16) secs]. Conclusion: The traditional 4x5-min (local or remote) IPC stimulus resulted in the fastest TT time compared to SHAM, there was no benefit of applying a greater number of cycles or employing unilateral IPC.
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The current study examined the adaptive response to both endurance (END) and sprint interval training (SIT) in a group of twenty-one recreationally active adults. All participants completed three weeks (four days/ week) of both END (30 minutes at ~65% VO2peak work rate (WR) and SIT (eight, 20-second intervals at ~170% VO2peak WR separated by 10 seconds of active rest) following a randomized crossover study design with a three-month washout period between training interventions. While a main effect of training was observed for VO2peak, lactate threshold, and submaximal heart rate (HR), considerable variability was observed in the individual responses to both END and SIT. No significant positive relationships were observed between END and SIT for individual changes in any variable. Non-responses were determined using two times the typical error (TE) of measurement for VO2peak (0.107 L/min), lactate threshold (15.7 W), and submaximal HR (10.7bpm). Non-responders in VO2peak, lactate threshold, and submaximal HR were observed following both END and SIT, however, the individual patterns of response differed following END and SIT. Interestingly, all individuals responded in at least one variable when exposed to both END and SIT. These results suggest that the individual response to exercise training is highly variable following different training protocols and that the incidence of non-response to exercise training may be reduced by changing the training stimulus for non-responders to three weeks of END or SIT.
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We developed a technique for measuring patient limb occlusion pressure (LOP) through a tourniquet cuff that overcomes many limitations of existing LOP measurement techniques. The purpose of the study is to determine whether the LOP measured by the proposed technique is statistically or clinically different from that measured by the gold standard Doppler ultrasound technique. The study used randomized crossover multicenter trials. 143 pre- and post-surgical patients with a mean age of 54 years (range 17–86 years) were enrolled in the study. Pneumatic cuffs were applied to the non-operative upper and lower limbs and LOP was measured using the proposed technique and the Doppler ultrasound technique. From a total of 252 usable measurements for each technique (134 for upper limbs and 118 for lower limbs), the mean difference in LOP between the two techniques was 1 ± 8 mmHg for the upper limbs, 0 ± 15 mmHg for the lower limbs, and 1 ± 12 mmHg overall. The differences between the proposed technique and the Doppler technique were neither statistically nor clinically significant. The simplicity, effectiveness, and accuracy of the proposed technique should lead to broader clinical usage and acceptance of LOP measurement, thus leading to safer, personalized pressures in surgical tourniquet applications.
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Purpose: Recent studies have reported ischemic preconditioning (IPC) can acutely improve endurance exercise performance in athletes. However, placebo and nocebo effects have not been sufficiently controlled, and the effect on aerobic metabolism parameters that determine endurance performance [e.g., oxygen cost of running, lactate threshold, and maximal oxygen uptake (V[Combining Dot Above]O2max)] has been equivocal. Thus, we circumvented limitations from previous studies to test the effect of IPC on aerobic metabolism parameters and endurance performance in well-trained runners. Methods: Eighteen runners (14 men/4 women) were submitted to three interventions, in random order: IPC; sham intervention (SHAM); and resting control (CT). Subjects were told both IPC and SHAM would improve performance compared to CT (i.e., similar placebo induction) and IPC would be harmless despite circulatory occlusion sensations (i.e., nocebo avoidance). Next, pulmonary ventilation and gas exchange, blood lactate concentration, and perceived effort were measured during a discontinuous incremental test on a treadmill. Then, a supramaximal test was used to verify the V[Combining Dot Above]O2max and assess endurance performance (i.e., time to exhaustion). Results: Ventilation, oxygen uptake, carbon dioxide output, lactate concentration, and perceived effort were similar among IPC, SHAM, and CT throughout the discontinuous incremental test (P > 0.05). Oxygen cost of running, lactate threshold, and V[Combining Dot Above]O2max were also similar among interventions (P > 0.05). Time to exhaustion was longer after IPC (mean ± SEM, 165.34 ± 12.34 s) and SHAM (164.38 ± 11.71 s) than CT (143.98 ± 12.09 s; P = 0.02 and 0.03, respectively), but similar between IPC and SHAM (P = 1.00). Conclusions: IPC did not change aerobic metabolism parameters, whereas improved endurance performance. The IPC improvement, however, did not surpass the effect of a placebo intervention.
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This pilot study aimed to evaluate the differential effects of a remote ischemic preconditioning (rIPC) manoeuvre on performance and red blood cell (RBC) deformability compared to a sham control and a placebo setting. Ten male subjects performed three test settings in a single-blind, crossover, and randomized control design. All settings started with 20 min of rest and were followed by 4 cycles of occlusion/reperfusion consisting of 5 min each. During rIPC and placebo, the cuff pressure was inflated to 200 mmHg and 120 mmHg, respectively. During the sham control setting, 10 mmHg pressure was applied. All tests were followed by a cycle exercise with lactate diagnostics. Power at 2 and 4 mmol/l lactate thresholds were calculated. RBC deformability was measured before and after the respective manoeuvre. Results showed that no effect resulted from any manoeuvre on performance values or RBC deformability. But 6 subjects showed a higher power at the 2 mmol/l threshold, and 5 subjects exerted higher power at the 4 mmol/l threshold when the rIPC manoeuvre preceded the exercise. In these responsive subjects, RBC deformability also improved. Hence, rIPC effects are much influenced by the subjects’ responsiveness, and improved RBC deformability might contribute to enhanced performance in responsive subjects.
Article
The effect of ischemic preconditioning (IPC) on swimming performance was examined. Using a randomized, crossover design, National-and International-level swimmers (n=20; 14 males, 6 females) participated in three trials (Con, IPC-2h, IPC-24h). Lower-body IPC (4 x 5 min bi-lateral blood-flow restriction at 160-228 mmHg, and 5 min reperfusion) was used 2- (IPC-2h) or 24-h (IPC-24h) before a self-selected (100 m, n=15; 200 m, n=5) swimming time-trial (TT). The Con trial used a sham intervention (15 mmHg) 2h prior to exercise. All trials required a 40-min standardized pre-competition swimming warm-up (followed by 20-min rest; replicating pre-competition call room procedures) 1h before TT. Capillary blood (pH, blood gases and lactate concentrations) was taken immediately pre-and post-IPC, pre-TT and post-TT. No effects on TT for 100 m (P=0.995; IPC-2h: 64.94±8.33 s; IPC-24h: 64.67±8.50 s; Con: 64.94± 8.24 s), 200 m (P=0.405; IPC-2h: 127.70±10.66 s; IPC-24h: 129.26±12.99 s; Con: 130.19±10.27 s) or combined total time (IPC-2h: 84.27±31.52 s; IPC-24h: 79.87±29.72 s; Con: 80.55±31.35 s) were observed following IPC. Base excess (IPC-2h: -13.37±8.90 mmol⋅L; Con: -13.35±7.07 mmol⋅L; IPC-24h: -16.53±4.65 mmol⋅L), pH (0.22±0.08; all conditions), bicarbonate (IPC-2h: -11.66±3.52 mmol⋅L; Con: -11.62±5.59 mmol⋅L; IPC-24h: -8.47±9.02 mmol⋅L), total carbon dioxide (IPC-2h: -12.90±3.92 mmol⋅L; Con: -11.55±7.61 mmol⋅L; IPC-24h: 9.90±8.40 mmol⋅L), percentage oxygen saturation (IPC-2h: -0.16±1.86%; Con: +0.20±1.93%; IPC-24h: +0.47±2.10%) and blood lactate (IPC-2h: +12.87±3.62 mmol⋅L; Con: +12.41±4.02 mmol⋅L; IPC-24h: +13.27±3.81 mmol⋅L) were influenced by swimming TT (P<0.001), but not condition (all P>0.05). No effect of IPC was seen when applied 2- or 24-h before swimming TT on any indices of performance or physiological measures recorded.
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Purpose: Endurance athletes often compete and train at altitude where exercise capacity is reduced. Investigating acclimation strategies is therefore critical. Ischemic preconditioning (IPC) can improve endurance performance at sea level through improved O2 delivery and utilization, which could also prove beneficial at altitude. However, data are scarce and there is no study at altitudes commonly visited by endurance athletes. Methods: In a randomized, crossover study, we investigated performance and physiological responses in thirteen male endurance cyclists during four 5-km cycling time trials (TT), preceded by either IPC (3x5-minutes ischemia/5-minutes reperfusion cycles at 220 mmHg) or SHAM (20 mmHg) administered to both thighs, at simulated low (FIO2 0.180, ~1200 m) and moderate (FIO2 0.154, ~2400 m) altitudes. Time to completion, power output, cardiac output (Q), arterial O2 saturation (SpO2), quadriceps tissue saturation index (TSI) and ratings of perceived exertion (RPE) were recorded throughout the TT. Differences between IPC and SHAM were analyzed at every altitude using Cohen's effect size (ES) and compared to the smallest worthwhile change. Results: At low altitude, IPC possibly improved time to complete the TT (-5.2sec, -1.1%, Cohen's ES ± 90% confidence limits -0.22, -0.44;0.01), power output (2.7%, ES 0.21, -0.08;0.51) and Q (5.0%, ES 0.27, 0.00;0.54), but did not alter SpO2, muscle TSI and RPE. At moderate altitude, IPC likely enhanced completion time (-7.3sec, -1.5%, ES -0.38, -0.55;-0.20) and power output in the second half of the TT (4.6%, ES 0.28, -0.15;0.72), increased SpO2 (1.0%, ES 0.38, -0.05;0.81), and decreased TSI (-6.5%, ES -0.27, -0.73;0.20) and RPE (-5.4%, ES -0.27, -0.48;-0.06). Conclusion: IPC may provide an immediate and effective strategy to defend SpO2 and enhance high-intensity endurance performance at moderate altitude.