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The Impact of Different Ischemic Preconditioning Pressures on Pain Sensitivity and Resistance Exercise Performance
Abstract
Kataoka, R, Song, JS, Yamada, Y, Hammert, WB, Seffrin, A, Spitz, RW, Wong, V, Kang, A, and Loenneke, JP. The impact of different ischemic preconditioning pressures on pain sensitivity and resistance exercise performance. J Strength Cond Res XX(X): 000–000, 2023—To determine (a) the impact of ischemic preconditioning pressures (applied as a % of arterial occlusion pressure [AOP]) on pressure pain threshold (PPT) and resistance exercise performance and (b) whether changes in performance could be explained by changes in PPT. Subjects ( n = 39) completed 4 protocols in a randomized order: (a) ischemic preconditioning (IPC) at 110% AOP (IPC 110%), (b) IPC at 150% AOP (IPC 150%), (c) IPC at 10% AOP (Sham), and (d) time-matched control (CON). Each protocol included 4 cycles of 5 minutes of occlusion followed by 5 minutes of reperfusion. Pressure pain threshold was taken before and after. Discomfort ratings were given at the end of each cycle. Every visit finished with 2 sets of 75-second maximal isokinetic unilateral elbow flexion or extension. Overall, IPC 110% and IPC 150% resulted in similar increases in PPT relative to CON [110%: difference of 0.36 (0.18, 0.54) kg·m ⁻² ; 150%: difference of 0.377 (0.15, 0.59) kg·m ⁻² ] and Sham. Both resulted in greater discomfort than Sham and CON, with IPC 150% inducing greater discomfort than IPC 110% (BF 10 : 14.74). There were no differences between the conditions for total work (BF 10 : 0.23), peak torque (BF 10 : 0.035), or average power (BF 10 : 0.159). We did not find evidence that PPT mediated performance. We did not detect changes in performance with 2 different relative pressures greater than AOP. Our mean applied pressures were lower than those used previously. There might be a minimal level of pressure (e.g., >150% of AOP) that is required to induce ergogenic effects of ischemic preconditioning.
... Initially, work by Pereira et al. (2020) found that IPC in the contralateral arm and leg reduced the intensity of pain during a sustained pressure stimulus on the finger when compared to sham and control conditions, and this reduction in pain was related to an improvement in exercise performance. However, recent work (Kataoka et al. 2022) has demonstrated increases in PPTs after IPC, but this did not translate to improved maximal isokinetic elbow flexion performance. Conversely, Angius et al. (2022) found that IPC did not significantly increase PPTs or decrease pain during a fixed intensity knee-extensor exercise task compared to a sham, but IPC did reduce the pain intensity experienced during post-exercise circulatory occlusion. ...
... Similarly, PPTs were greater in IPC compared to sham for the contralateral leg, indicating that IPC can also induce non-local hypoalgesia, although there is less certainty around these results, given that IPC did not differ to control. Our results extend from those of Kataoka et al. (2022) who also demonstrated a hypoalgesic effect of IPC, but in the upper limb using greater relative pressures (110% and 150% LOP). However, these findings are in contrast to recent work (Angius et al. 2022) who demonstrated no differences in local or remote PPTs after lower limb IPC compared to a low-pressure, sham protocol. ...
... However, these findings are in contrast to recent work (Angius et al. 2022) who demonstrated no differences in local or remote PPTs after lower limb IPC compared to a low-pressure, sham protocol. However, in their study, PPTs were measured shortly after each IPC cycle, whereas in the present study we recorded PPTs 10 min after the entire intervention (Kataoka et al. 2022) and adjusted for baseline day-to-day variability in PPT which may explain differences in results. The prolonged and high level of pressure placed on the leg musculature by IPC likely activates the group III afferent nociceptors which preferentially respond to mechanical deformation/pressure. Therefore, the current data supports the notion that IPC can reduce the sensitivity of group III cutaneous/deep tissue afferents in the treated limb. ...
The aim of this study was to assess if ischaemic preconditioning (IPC) can reduce pain perception and enhance corticospinal excitability during voluntary contractions. In a randomised, within-subject design, healthy participants took part in three experimental visits after a familiarisation session. Measures of pressure pain threshold (PPT), maximum voluntary isometric force, voluntary activation, resting twitch force, corticospinal excitability and corticospinal inhibition were performed before and ≥10 min after either, unilateral IPC on the right leg (3 × 5 min); a sham protocol (3 × 1 min); or a control (no occlusion). Pain perception was then assessed in response to a hypertonic saline injection into the vastus lateralis muscle. In the right (occluded) leg, PPT was 10% greater after IPC compared to sham (P = 0.004). PPTs were also 9.5% greater in the contralateral leg for IPC compared to sham (P = 0.031). Maximum voluntary force, voluntary activation and resting twitch force were not different between conditions (all P ≥ 0.133). Measures of corticospinal excitability and inhibition also revealed no significant differences between conditions (all P ≥ 0.240). Hypertonic saline evoked pain revealed no difference in reported intensity or duration between conditions (P ≥ 0.082). IPC can reduce pain sensitivity in local and remote areas but does not subsequently impact neurophysiological measures of excitability or inhibition.
... These mechanisms interact with each other and collectively improve the muscle's explosive power, endurance, and neuromuscular coordination, thereby enabling subjects to exhibit superior athletic performance in subsequent high-intensity training or competitive events. Currently, numerous scholars have explored the role of IPC in sports training from a methodological perspective, including aspects such as the site of occlusive intervention, the magnitude of occlusive pressure, the duration of IPC application, the cycling period of IPC, the differential effects of IPC usage, and its impact on athletic performance [7][8][9][10][11]. The performance-enhancing effects of IPC are primarily manifested in two areas: strength endurance and explosive power. ...
Objective: This study designed experiments to explore the effects of ischemic preconditioning (IPC) intervention with different cycling periods on the upper limb strength performance of college male bodybuilding athletes. Methods: Ten bodybuilding athletes were recruited for a randomized, double-blind, crossover experimental study. All subjects first underwent pre-tests with two sets of exhaustive bench presses at 60% of their one-repetition maximum (1RM) to assess upper limb strength performance. They then experienced three different IPC intervention modes (T1: 1 × 5 min, T2: 2 × 5 min, T3: 3 × 5 min), as well as a non-IPC intervention mode (CON), followed by a retest of the bench press. An Enode pro device was used to record the barbell’s velocity during the bench press movement (peak velocity (PV), mean velocity (MV)); power (peak power (PP), mean power (MP)); and time under tension (TUT) to evaluate upper limb strength performance. Results: PV values: T1 showed significant increases compared to pre-tests in the first (p = 0.02) and second (p = 0.024) tests, and were significantly greater than the CON (p = 0.032); T2 showed a significant increase in PV in the first test (p = 0.035), with no significant differences in other groups. MV values: T1 showed a significant increase in MV in the first test compared to the pre-test (p = 0.045), with no significant differences in other groups. PP values: T1 showed a highly significant increase in PP in the first test compared to the pre-test (p = 0.001), and was significantly higher than the CON (p = 0.025). MP values: T1 showed highly significant increases in MP in both the first (p = 0.004) and second (p = 0.003) tests compared to the pre-test; T2 showed a highly significant increase in MP in the first test (p = 0.039) and a significant increase in the second test (p = 0.039). T1’s MP values were significantly higher than the CON in both tests; T2’s MP values were significantly higher than the CON in the first (p = 0.005) and second (p = 0.024) tests. TUT values: T1 showed highly significant increases in TUT in the first (p < 0.001) and second (p = 0.002) tests compared to the pre-test, and were significantly higher than the CON. Conclusions: (1) Single-cycle and double-cycle IPC interventions both significantly enhance upper limb strength performance, significantly improving the speed and power in exhaustive bench press tests, with the single-cycle IPC intervention being more effective than the double-cycle IPC intervention. (2) The triple-cycle IPC intervention does not improve the upper limb strength performance of bodybuilding athletes in exhaustive bench presses.
This study compared the effects of short-duration ischemic preconditioning, a single-set high-resistance exercise and their combination on subsequent bench press performance. Twelve men (age: 25.8 ± 6.0 years, bench press 1-RM: 1.21 ± 0.17 kg kg⁻¹ body mass) performed four 12 s sets as fast as possible, with 2 min of recovery between sets, against 60% 1-RM, after: a) 5 min ischemic preconditioning (IPC; at 100% of full arterial occlusion pressure), b) one set of three bench press repetitions at 90% 1-RM (PAPE), c) their combination (PAPE + IPC) or d) control (CTRL). Mean barbell velocity in ischemic preconditioning was higher than CTRL (by 6.6–9.0%, p < 0.05) from set 1 to set 3, and higher than PAPE in set 1 (by 4.4%, p < 0.05). Mean barbell velocity in PAPE was higher than CTRL from set 2 to set 4 (by 6.7–8.9%, p < 0.05), while mean barbell velocity in PAPE + IPC was higher than CTRL only in set 1 (+5.8 ± 10.0%). Peak barbell velocity in ischemic preconditioning and PAPE was higher than CTRL (by 7.8% and 8.5%, respectively; p < 0.05). Total number of repetitions was similarly increased in all experimental conditions compared with CTRL (by 7.0–7.9%, p < 0.05). Rating of perceived exertion was lower in ischemic preconditioning compared with CTRL (p < 0.001) and PAPE (p = 0.045), respectively. These results highlight the effectiveness of short-duration ischemic preconditioning in increasing bench press performance, and suggest that it may be readily used by strength and conditioning coaches during resistance training due to its brevity and lower perceived exertion.
The findings of the ischemic preconditioning (IPC) on exercise performance are mixed regarding types of exercise, protocols and participants' training status. Additionally, studies comparing IPC with sham (i.e., low-pressure cuff) and/or control (i.e., no cuff) interventions are contentious. While studies comparing IPC versus a control group generally show an IPC significant effect on performance, sham interventions show the same performance improvement. Thus, the controversy over IPC ergogenic effect may be due to limited discussion on the psychophysiological mechanisms underlying cuff maneuvers. Psychophysiology is the study of the interrelationships between mind, body and behavior, and mental processes are the result of the architecture of the nervous system and voluntary exercise is a behavior controlled by the central command modulated by sensory inputs. Therefore, this narrative review aims to associate potential IPC-induced positive effects on performance with sensorimotor pathways (e.g., sham influencing bidirectional body-brain integration), hemodynamic and metabolic changes (i.e., blood flow occlusion reperfusion cycles). Overall, IPC and sham-induced mechanisms on exercise performance may be due to a bidirectional body–brain integration of muscle sensory feedback to the central command resulting in delayed time to exhaustion, alterations on perceptions and behavior. Additionally, hemodynamic responses and higher muscle oxygen extraction may justify the benefits of IPC on muscle contractile function.
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.
Purpose
This study investigated the effect of ischemic preconditioning (IP) on metaboreflex activation following dynamic leg extension exercise in a group of healthy participants.
Method
Seventeen healthy participants were recruited. IP and SHAM treatments (3 × 5 min cuff occlusion at 220 mmHg or 20 mmHg, respectively) were administered in a randomized order to the upper part of exercising leg’s thigh only. Muscle pain intensity (MP) and pain pressure threshold (PPT) were monitored while administrating IP and SHAM treatments. After 3 min of leg extension exercise at 70% of the maximal workload, a post-exercise muscle ischemia (PEMI) was performed to monitor the discharge group III/IV muscle afferents via metaboreflex activation. Hemodynamics were continuously recorded. MP was monitored during exercise and PEMI.
Results
IP significantly reduced mean arterial pressure compared to SHAM during metaboreflex activation (mean ± SD, 109.52 ± 7.25 vs. 102.36 ± 7.89 mmHg) which was probably the consequence of a reduced end diastolic volume (mean ± SD, 113.09 ± 14.25 vs. 102.42 ± 9.38 ml). MP was significantly higher during the IP compared to SHAM treatment, while no significant differences in PPT were found. MP did not change during exercise, but it was significantly lower during the PEMI following IP (5.10 ± 1.29 vs. 4.00 ± 1.54).
Conclusion
Our study demonstrated that IP reduces hemodynamic response during metaboreflex activation, while no effect on MP and PPT were found. The reduction in hemodynamic response was likely the consequence of a blunted venous return.
Purpose The purpose of this study was to examine whether an individual’s IPC-mediated change in cold pain sensitivity is associated with the same individual’s IPC-mediated change in exercise performance.
Methods Thirteen individuals (8 males; 5 females, 27 ± 7 years, 55 ± 5 ml.kgs–1.min–1) underwent two separate cold-water immersion tests: with preceding IPC treatment and without. In addition, each participant undertook two separate 5-km cycling time trials: with preceding IPC treatment and without. Pearson correlation coefficients were used to assess the relationship between an individual’s change in cold-water pain sensitivity following IPC with their change in 5-km time trial performance following IPC.
Results During the cold-water immersion test, pain intensity increased over time (p < 0.001) but did not change with IPC (p = 0.96). However, IPC significantly reduced the total time spent under pain (−9 ± 7 s; p = 0.001) during the cold-water immersion test. No relationship was found between an individual’s change in time under pain (r = −0.2, p = 0.6) or pain intensity (r = −0.3, p = 0.3) following IPC and their change in performance following IPC.
Conclusion These findings suggest that IPC can modulate sensitivity to a painful stimulus, but this altered sensitivity does not explain the ergogenic efficacy of IPC on 5-km cycling performance.
This study examined the effects of a simultaneous ischemic preconditioning (IPC) and SHAM intervention to reduce the placebo effect due to a priori expectation on the performance of knee extension resistance exercise. Nine moderately trained men were tested in three different occasions. Following the baseline tests, subjects performed a first set of leg extension tests after the IPC (3 X 5 min 50 mmHg above systolic blood pressure) on right thigh and the SHAM (same as IPC, but 20 mmHg) on left thigh. After 48 hours, the subjects performed another set of tests with the opposite applications. Number of repetitions, maximal voluntary isometric contraction (MVIC) and perceptual indicators were analyzed. After IPC and SHAM intervention performed at the same time, similar results were observed for the number of repetitions, with no significant differences between conditions (baseline x IPC x SHAM) for either left (p = 0.274) or right thigh (p = 0.242). The fatigue index and volume load did not show significant effect size after IPC and SHAM maneuvers. In contrast, significant reduction on left tight MVIC was observed (p = 0.001) in SHAM and IPC compared to baseline, but not for right thigh (p = 0.106). Results from the current study may indicate that applying IPC prior to a set of leg extension does not result in ergogenic effects. The placebo effect seems to be related to this technique and its dissociation seems unlikely, therefore including a SHAM or placebo group in IPC studies is strongly recommended.
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.
Background
Ischemic preconditioning (IPC) is suggested to decrease fatigability in some individuals but not others. Sex differences in response to IPC may account for this variability and few studies systematically investigated the effects of IPC in men and women. The goal of this study was to determine if time to task failure, perception of pain, and neuromuscular mechanisms of fatigability were altered by IPC in men and women.
Methods
Ten women (29 ± 5 years old) and 10 men (28 ± 6 years old) performed isometric contractions with the plantar flexor muscles of the dominant leg at 20% of maximal voluntary contraction until task failure. We used a repeated measures design where each individual performed 3 randomized and counterbalanced test sessions: (A) IPC session, cuff inflation and deflation (5 min each repeated 3 times) performed before the exercise by inflating cuffs to the non-dominant leg and arm; (B) sham session, cuffs were inflated for a short period (1 min); and (C) control session, no cuffs were involved.
Results
Compared with control, IPC increased time to task failure in men (mean difference, 5 min; confidence interval (CI) of mean difference, 2.2; 7.8 min; P = 0.01) but not women (mean difference, − 0.6 min; CI of mean difference, − 3.5; 2.4 min; P = 0.51). In men, but not women, the IPC-induced increase in time to task failure was associated with lower response to pressure pain ( r = − 0.79). IPC further exposed sex differences in arterial pressure during fatiguing contractions (session × sex: P < 0.05). Voluntary activation, estimated with the twitch interpolation technique, and presynaptic inhibition of leg Ia afferents were not altered after IPC for men and women. The tested variables were not altered with sham.
Conclusions
The ergogenic effect of IPC on time to task failure was observed only in men and it was associated with reductions in the perception of pain. This pilot data suggest the previously reported inter-individual variability in exercise-induced fatigability after IPC could be a consequence of the sex and individual response to pain.
Introduction:
Neuromuscular fatigue reduces the temporal structure, or complexity, of muscle torque output, purportedly through an effect on motor unit behaviour. Ischaemic pre-conditioning (IPC), an emerging ergogenic aid, has been demonstrated to have a potent effect on muscular output and endurance. We therefore tested the hypothesis that IPC would attenuate the fatigue-induced loss of muscle torque complexity.
Methods:
Ten healthy participants (6 male/4 female) performed intermittent isometric knee extension contractions (6 s contraction, 4 s rest) to task failure at 40% maximal voluntary contraction (MVC). Contractions were preceded by either IPC (three bouts of 5 minutes proximal thigh occlusion at 225 mmHg, interspersed with 5 minutes rest) or SHAM (as IPC, but occlusion at only 20 mmHg) treatments. Torque and EMG signals were sampled continuously. Complexity and fractal scaling were quantified using approximate entropy (ApEn) and the detrended fluctuation analysis (DFA) α scaling exponent. Muscle oxygen consumption (mV[Combining Dot Above]O2) was determined using near-infrared spectroscopy.
Results:
IPC increased time to task failure by 43 ± 13% (mean ± SEM, P = 0.047). Complexity decreased in both trials (decreased ApEn, increased DFA α; both P < 0.001), though the rate of decrease was significantly lower following IPC (ApEn, -0.2 ± 0.1 vs. -0.4 ± 0.1, P = 0.013; DFA α, 0.2 ± 0.1 vs. 0.3 ± 0.1, P = 0.037). Similarly, the rates of increase in EMG amplitude (P = 0.022) and mV[Combining Dot Above]O2 (P = 0.043) were significantly slower following IPC.
Conclusion:
These results suggest the ergogenic effect of IPC observed here is of neural origin and accounts for the slowing of the rates of change in torque complexity, EMG amplitude and muscle oxygen consumption as fatigue develops.
The aim of this study was to investigate the acute effect of ischemic preconditioning (IPC) in a resistance exercise (RE) training session on the number of repetitions performed, total volume, and rating of perceived exertion in recreationally trained and normotensive men. Sixteen recreationally trained and normotensive men completed three RE sessions in a counter-balanced and randomized order: a) No IPC (control) followed by RE (CON), b) IPC protocol using 220 mmHg followed by RE (IPC), and c) IPC cuff control protocol with 20 mmHg followed by RE (CUFF). RE was performed with three sets of each exercise (bench press (BP), leg press (LP), lateral pulldown (LPD), hack machine squat (HM), shoulder press (SP), and smith back squat (SS)) until concentric muscular failure, at 80% of one repetition maximum, with 90 seconds of rest between sets and two minutes of rest between exercises. IPC and CUFF consisted of 4 cycles of 5 minutes of occlusion/sham alternating with 5 min of no occlusion (0 mmHg) using a pneumatic tourniquet applied around the subaxillary region of the upper arm. For each condition, the number of repetitions completed, total volume of work performed, and rating of perceived exertion were determined. Finally, no significant difference was found for rating of perceived exertion between any experimental protocol. IPC significantly (p<0.05) increased the number of repetitions across exercises. Consequently, total volume of work performed was significantly higher in IPC (46169.9) compared to CON (34068.9) and CUFF (36590.4) across all exercises. This work may have important implications for athletic populations, as it demonstrates increase in muscle performance outcomes during a single RE session. Therefore, performing IPC before RE could be an important exercise prescription recommendation to increase maximum repetition performance and total volume of work performed and thus potentially increase desired training adaptations (i.e., strength and hypertrophy).
Ischemic preconditioning (IPC) has been suggested as a potential ergogenic aid to improve exercise performance, although controversial findings exist. The controversies may be explained by several factors, including the mode of exercise, the ratio between the magnitude of improvement, or the error of measurement and physiological meaning. However, a relevant aspect has been lacking in the literature: the interpretation of the findings considering statistical tests and adequate effect size (ES) according to the fitness level of individuals. Thus, we performed a systematic review with meta-analysis to update the effects of IPC on exercise performance and physiological responses, using traditional statistics (P values), ES, and smallest worth change (SWC) approach contextualizing the IPC application to applied Sports and Exercise performance. Forty-five studies met the inclusion criteria. Overall, the results show that IPC has a minimal or nonsignificant effect on performance considering the fitness level of the individuals, using statistical approaches (i.e., tests with P value, ES, and SWC). Therefore, IPC procedures should be revised and refined in future studies to evaluate if IPC promotes positive effects on performance in a real-world scenario with more consistent interpretation.
Purpose:
Ischemic preconditioning (IPC) through purposeful circulatory occlusion may enhance exercise performance. The value of IPC for improving performance is controversial owing to challenges with employing effective placebo controls. This study examines the efficacy of IPC vs a deceptive sham protocol for improving performance to determine whether benefits of IPC are attributable to true physiological effects. It was hypothesized that IPC would favorably alter performance more than a sham treatment and that physiological responses to exercise would be affected only after IPC treatment.
Methods:
In a randomized order, 16 participants performed incremental exercise to exhaustion on a cycle ergometer in control conditions and after sham and IPC treatments. Participants rated their belief as to the efficacy of each treatment compared with control.
Results:
TTE was greatest after IPC (control 1331 ± 270 s, IPC 1429 ± 300 s, sham 1343 ± 255 s, P = .02,) despite negative performance expectations after IPC and positive expectation after sham. Maximal aerobic power remained unchanged after both SHAM and IPC (control 42.0 ± 5.2, IPC 41.7 ± 5.5, sham 41.6 ± 5.5 mL·kg-1·min-1, P = .7), as did submaximal lactate concentration (control 8.9 ± 2.6, sham 8.0 ± 1.9, IPC 7.7 ± 2.1 mmol, P = .1) and oxygen uptake (control 37.8 ± 4.8, sham 37.5 ± 5.3, IPC 37.5 ± 5.5 mL·kg-1·min-1, P = .6).
Conclusions:
IPC before cycling exercise provides an ergogenic benefit that is not attributable to a placebo effect from positive expectation and that was not explained by traditionally suggested mechanisms.
Ischemic preconditioning (IPC) has been suggested to preserve neural drive during fatiguing dynamic exercise, however, it remains unclear as to whether this may be the consequence of IPC‐enhanced muscle oxygenation. We hypothesized that the IPC‐enhanced muscle oxygenation during a dynamic exercise task would subsequently attenuate exercise‐induced reductions in voluntary activation. Ten resistance trained males completed three 3 min maximal all‐out tests (AOTs) via 135 isokinetic leg extensions preceded by treatments of IPC (3 × 5 min bilateral leg occlusions at 220 mmHg), SHAM (3 × 5 min at 20 mmHg) or CON (30 min passive rest). Femoral nerve stimulation was utilized to assess voluntary activation and potentiated twitch torque during maximal voluntary contractions (MVCs) performed at baseline (BL), prior to the AOT (Pre), and then 10 sec post (Post). Tissue oxygenation (via near‐infrared spectroscopy) and sEMG activity was measured throughout the AOT. MVC and twitch torque levels declined (MVC: −87 ± 23 Nm, 95% CI = −67 to −107 Nm; P < 0.001, twitch: −30 ± 13 Nm; 95% CI = −25 to −35 Nm; P < 0.001) between Pre and Post without reductions in voluntary activation (P = 0.72); there were no differences between conditions (MVC: P = 0.75, twitch: P = 0.55). There were no differences in tissue saturation index (P = 0.27), deoxyhemoglobin concentrations (P = 0.86) or sEMG activity (P = 0.92) throughout the AOT. These findings demonstrate that IPC does not preserve neural drive during an all‐out 3 min isokinetic leg extension task. This study aimed to investigate how ischemic preconditioning (IPC)‐enhanced muscle oxygenation influences reductions in neural drive induced by a maximal dynamic exercise test. Our results show that pre‐post declines in neural drive were unaffected by IPC and furthermore, neither surface electromyography nor measures of skeletal muscle oxygenation were influenced by IPC throughout the exercise test.
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.
Prior peripheral hypoxia induced via remote ischemic preconditioning (IPC) can improve physical performance in male athletes through improved O2 delivery and utilization. Since females may have an innate protective mechanism against ischemia-reperfusion injury, and since muscle metabolism during contraction differs between sexes, it is relevant to examine the impact of sex in response to IPC to determine whether it is also ergogenic in females. In a randomized, crossover, single-blind study, we investigated muscle performance, hemodynamic and O2 uptake in strength-trained males (n = 9) and females (n = 8) performing five sets of 5 maximum voluntary knee extensions on an isokinetic dynamometer, preceded by either IPC (3 × 5-min ischemia/5-min reperfusion cycles at 200 mmHg) or SHAM (20 mmHg). Changes in deoxy-hemoglobin (Δ[HHb], expressed in percentage of arterial occlusion and considered an index of O2 extraction), and total hemoglobin (Δ[THb]) concentrations of the vastus lateralis muscle were continuously monitored by near-infrared spectroscopy. The metabolic efficiency of the contractions was calculated as the average force/Δ[HHb]avg ratio. Cohen's effect sizes (ES) ± 90% confidence limits were used to estimate IPC-induced changes and sex differences. IPC increased total muscular force in males only (13.0%, ES 0.64, 0.37;0.90), and this change was greater than in females (10.4% difference, ES 0.40, 0.10;0.70). Percent force decrement was only attenuated in females (−19.8%, ES −0.38, −0.77;0.01), which was clearly different than males (sex difference: ES 0.45, −0.16;1.07). IPC also induced different changes between sexes for average muscle O2 uptake in set 2 (males: 6.4% vs. females: −16.7%, ES 0.21, −0.18;0.60), set 3 (males: 7.0% vs. females: −44.4%, ES 0.56, −0.17;1.29), set 4 (males: 9.1% vs. females: −40.2%, ES 0.51, −0.10;1.13), and set 5 (males: 10.2% vs. females: −40.4%, ES 0.52, −0.04;1.09). However, metabolic efficiency was not meaningfully different between conditions and sexes. IPC increased muscle blood volume (↑[THb]) at rest and during recovery between sets, to the same extent in both sexes. Despite a similar IPC-induced initial increase in O2 delivery in both sexes, males displayed greater peripheral O2 extraction and greater strength enhancement. This ergogenic effect appears to be mediated in part via an up regulated oxidative function in males. We conclude that strength-trained males might benefit more from IPC than their female counterparts during repeated, maximal efforts.
Objective: Rating of perceived exertion scales are commonly used in resistance training (RT)though most suffer from conflation of perceptions of both effort and discomfort by participants. The aim of this study was to examine reliability of trainee ratings of perceived effort (RPE-E) and discomfort (RPE-D) using these two novel scales in addition to reliability and validity of trainer RPE-E.
Design: Participants underwent 3 RT trials over a period of three weeks.
Methods: Seventeen participants (males n = 6, females n = 11, age 63+16 years) completed 5 RT exercises for a single set using a load permitting a self-determined 6 repetition maximum (meaning they determined inability to complete further repetitions if attempted i.e. they predicted momentary failure on the next repetition). Trainers completed their rating of RPE-E, followed by participants reporting of RPE-E and RPE-D immediately after completion of the exercises. Spearman’s correlations examined the relationship between RPE-E and RPE-D. Reliability was examined as standard error of measurement (SEM) calculated for each outcome across the 3 trials (Intra-rater), in addition to agreement between trainers (Inter-rater), and agreement between trainer and trainee RPE-E.
Results: Correlations between RPE-E and RPE-D were significant but weak (r = .373 to 0.492; p< 0.01). Intra-rater SEMs for trainee RPE-E ranged from 0.64 to 0.85, trainee RPE-D ranged from 0.60 to 1.00, and trainer RPE-E ranged from 0.56 to 0.71. Inter-rater SEMs for trainer RPE-E ranged 0.25 to 0.66. SEMs for agreement between trainer and trainee RPE-E ranged from 1.03 to 1.25.
Conclusions: Results suggest participants were able to differentiate RPE-E and RPE-D and that the reliability for both trainee measures of RPE-E and RPE-D, in addition to trainer RPE-E is acceptable. Further, trainer RPE-E appeared to have acceptable validity compared to trainee RPE-E. These scales might be adopted in research examining the dose-response nature of effort upon RT outcomes and that trainers might use them to inform programming.
Muscle ischemia and reperfusion induced by ischemic preconditioning (IPC) can improve performance in various activities. However, the underlying mechanisms are still poorly understood. The purpose of this study was to examine the effects of IPC on muscle hemodynamics and oxygen (O2) uptake during repeated maximal contractions. In a cross-over, randomized, single-blind study, 10 strength-trained men performed 5 sets of 5 maximal voluntary knee extensions of the right leg on an isokinetic dynamometer, preceded by either IPC of the right lower limb (3×5-min compression/5-min reperfusion cycles at 200 mm Hg) or sham (20 mm Hg). Changes in deoxyhemoglobin, expressed as a percentage of arterial occlusion, and total hemoglobin ([THb]) concentrations of the vastus lateralis muscle were monitored continuously by near-infrared spectroscopy. Differences between IPC and sham were analyzed using Cohen’s effect size (ES) ± 90% confidence limits, and magnitude-based inferences. Compared with sham, IPC likely increased muscle blood volume at rest (↑[THb], 46.5%; ES, 0.56; 90% confidence limits for ES, –0.21, 1.32). During exercise, peak force was almost certainly higher (11.8%; ES, 0.37; 0.27, 0.47), average force was very likely higher (12.6%; ES, 0.47; 0.29, 0.66), and average muscle O2 uptake was possibly increased (15.8%; ES, 0.36; –0.07, 0.79) after IPC. In the recovery periods between contractions, IPC also increased blood volume after sets 1 (23.6%; ES, 0.30; –0.05, 0.65) and 5 (25.1%; ES, 0.32; 0.09, 0.55). Three cycles of IPC immediately increased muscle perfusion and O2 uptake, conducive to higher repeated force capacity in strength-trained athletes. This maneuver therefore appears relevant to enhancing exercise training stimulus.
Remote Ischemic Preconditioning (RIPC) is a non-invasive cardioprotective intervention that involves brief cycles of limb ischemia and reperfusion. This is typically delivered by inflating and deflating a blood pressure cuff on one or more limb(s) for several cycles, each inflation-deflation being 3-5 min in duration. RIPC has shown potential for protecting the heart and other organs from injury due to lethal ischemia and reperfusion injury, in a variety of clinical settings. The mechanisms underlying RIPC are under intense investigation but are just beginning to be deciphered. Emerging evidence suggests that RIPC has the potential to improve exercise performance, via both local and remote mechanisms. This review discusses the clinical studies that have investigated the role of RIPC in cardioprotection as well as those studying its applicability in improving athletic performance, while examining the potential mechanisms involved.
This study evaluated the effect of ischemic preconditioning (IPC) on resistance exercise (RE) performance in the lower limbs. Thirteen men participated in a randomized crossover design that involved 3 separate sessions (ischemic preconditioning, placebo and control). A 12-RM load for the leg extension exercise was assessed through test and retest sessions prior to the first experimental session. The IPC session consisted of 4 cycles of 5 minutes occlusion at 220 mmHg of pressure alternated with 5 minutes of reperfusion at 0 mmHg for a total of 40 minutes. The PLACEBO session consisted of 4 cycles of 5 minutes of cuff administration at 20 mmHg of pressure alternated with 5 minutes of pseudo-reperfusion at 0 mmHg for a total of 40 minutes. The occlusion and reperfusion phases were conducted alternately between the thighs, with subjects remaining seated. No ischemic pressure was applied during the control (CON) session and subjects sat passively for 40 minutes. Eight minutes following IPC, PLACEBO or CON, subjects performed three repetition maximum sets of the leg extension (2min rest between sets) with the pre-determined 12-RM load. Four minutes following the third set for each condition, blood lactate was assessed. The results showed that for the first set, the number of repetitions significantly increased for both the IPC (13.08 ± 2.11; p = 0.0036) and PLACEBO (13.15 ± 0.88; p = 0.0016) conditions, but not the CON (11.88 ± 1.07; p > 0.99) condition. Additionally, the IPC and PLACEBO conditions resulted insignificantly greater repetitions versus the CON condition on the 1set (p=0.015; p=0.007) and 2set (p=0.011; p=0.019), but not the 3 set (p=0.68; p>0.99). No difference (p=0.465) was found in the fatigue index and lactate concentration between conditions. These results indicate that IPC and PLACEBO ischemic preconditioning may have small beneficial effects on repetition performance over a CON condition. Due to potential for greater discomfort associated with the IPC condition, it is suggested that ischemic pre-conditioning might be practiced gradually to assess tolerance and potential enhancements to exercise performance.
Repeated episodes of ischemia followed by reperfusion, commonly referred to as ischemic preconditioning (IPC), represent an endogenous protective mechanism that delays cell injury. IPC also increases blood flow and improves endothelial function. We hypothesize that IPC will improve physical exercise performance and maximal oxygen consumption. The purpose of the study was to examine the effect of ischemic preconditioning in leg skeletal muscles on cycling exercise performance in healthy individuals. Fifteen healthy, well-trained subjects performed two incremental maximal exercise tests on a bicycle ergometer. Power output, oxygen consumption, ventilation, respiratory quotient, and heart rate were measured continuously. Blood pressure and blood lactate were measured before and after the test. One exercise test was performed after the application of ischemic preconditioning, using a protocol of three series of 5-min ischemia at both legs with resting periods of 5 min in between. The other maximal cycling test served as a control. Tests were conducted in counterbalanced order, at least 1 week apart, at the same time of the day. The repeated ischemic periods significantly increased maximal oxygen consumption from 56.8 to 58.4 ml/min per kg (P = 0.003). Maximal power output increased significantly from 366 to 372 W (P = 0.05). Ischemic preconditioning had no effect on ventilation, respiratory quotient, maximal heart rate, blood pressure or on blood lactate. Repeated short-term leg ischemia prior to an incremental bicycle exercise test improves maximal oxygen consumption by 3% and power output by 1.6%. This protocol, which is suggested to mimic the effects of ischemic preconditioning, may have important implications for exercise performance.
Muscle fatigue is an exercise-induced reduction in maximal voluntary muscle force. It may arise not only because of peripheral changes at the level of the muscle, but also because the central nervous system fails to drive the motoneurons adequately. Evidence for "central" fatigue and the neural mechanisms underlying it are reviewed, together with its terminology and the methods used to reveal it. Much data suggest that voluntary activation of human motoneurons and muscle fibers is suboptimal and thus maximal voluntary force is commonly less than true maximal force. Hence, maximal voluntary strength can often be below true maximal muscle force. The technique of twitch interpolation has helped to reveal the changes in drive to motoneurons during fatigue. Voluntary activation usually diminishes during maximal voluntary isometric tasks, that is central fatigue develops, and motor unit firing rates decline. Transcranial magnetic stimulation over the motor cortex during fatiguing exercise has revealed focal changes in cortical excitability and inhibitability based on electromyographic (EMG) recordings, and a decline in supraspinal "drive" based on force recordings. Some of the changes in motor cortical behavior can be dissociated from the development of this "supraspinal" fatigue. Central changes also occur at a spinal level due to the altered input from muscle spindle, tendon organ, and group III and IV muscle afferents innervating the fatiguing muscle. Some intrinsic adaptive properties of the motoneurons help to minimize fatigue. A number of other central changes occur during fatigue and affect, for example, proprioception, tremor, and postural control. Human muscle fatigue does not simply reside in the muscle.
Kataoka, R, Song, JS, Bell, ZW, Wong, V, Spitz, RW, Yamada, Y, and Loenneke, JP. Effect of increased pressure pain threshold on resistance exercise performance with blood flow restriction. J Strength Cond Res XX(X): 000-000, 2022-This study aimed to examine whether increasing pressure pain threshold (PPT) through isometric handgrip exercise (HG) affects the number of repetitions completed and discomfort with knee extension exercise (KE) with blood flow restriction (BFR), and examine whether performing additional exercise leads to a further increase in PPT. Forty-one participants completed 2 trials: rest followed by low-load KE with BFR at 80% of resting arterial occlusion pressure (Rest + KE BFR) and low-intensity (30% of maximal strength) HG exercise followed by KE with BFR (HG + KE BFR). Pressure pain threshold was measured before and after exercise at the forearm and tibialis anterior. Results are presented as median difference (95% credible interval). Pressure pain threshold increased at the forearm (Bayes factor [BF 10 ]: 5.2 3 10 7) and tibialis anterior (BF 10 : 1.5 3 10 6) after HG exercise. However, this did not lead to greater repetitions being completed with BFR exercise (0.2 [20.1, 0.6] repetitions, BF 10 : 0.07). Pressure pain threshold after BFR exercise was not augmented over that observed with HG exercise (0.02 [20.15, 0.2] kg·cm 22 , BF 10 : 0.175) at the forearm. More data are needed in the lower body to determine which model best fits the data (BF 10 : 0.84). Discomfort with BFR exercise was not different between conditions (1.0 [22.3, 4.4] arbitrary units, BF 10 : 0.10). The pain-reducing effect of prior exercise did not change the repetitions completed with BFR exercise, suggesting that the change in PPT may not have been great enough to alter performance. Performing additional exercise did not elicit further increases in PPT nor was perceived discomfort to BFR exercise altered by changes in PPT.
Context:
Blood flow restricted exercise involves the use of external pressure to enhance fatigue and augment exercise adaptations. The mechanisms by which blood flow restricted exercise limits muscular endurance are not well understood.
Objective:
To determine how increasing blood flow restriction pressure impacts local muscular endurance, discomfort, and force steadiness when the contractions are already occlusive.
Design:
Within-participant, repeated-measures crossover design.
Setting:
University laboratory.
Patients:
A total of 22 individuals (13 males and 9 females).
Intervention:
Individuals performed a contraction at 30% of maximal isometric elbow flexion force for as long as possible. One arm completed the contraction with 100% of arterial occlusion pressure applied, while the other arm had 150% of arterial occlusion pressure applied. At the end of the protocol, individuals were asked to rate their perceived discomfort.
Main outcome measures:
Time to task failure, discomfort, and force steadiness.
Results:
Individuals had a longer time to task failure when performing the 100% arterial occlusion condition compared with the 150% arterial occlusion pressure condition (time to task failure = 82.4 vs 70.8 s; Bayes factors = 5.77). There were no differences in discomfort between the 100% and 150% conditions (median discomfort = 5.5 vs 6; Bayes factors = 0.375) nor were there differences in force steadiness (SD of force output 3.16 vs 3.31 N; Bayes factors = 0.282).
Conclusion:
The results of the present study suggest that, even when contractions are already occlusive, increasing the restriction pressure reduces local muscle endurance but does not impact discomfort or force steadiness. This provides an indication that mechanisms other than the direct alteration of blood flow are contributing to the increased fatigue with added restrictive pressure. Future studies are needed to examine neural mechanisms that may explain this finding.
Aim:
This study aimed to investigate and compare the magnitude of exercise-induced hypoalgesia (EIH) with low intensity blood flow restriction (BFR) resistance exercise (RE) at varying pressures to other intensities of resistance exercise and examine endogenous mechanisms of pain reduction.
Methodology:
Twelve individuals performed four experimental trials involving unilateral leg press exercise in a randomised crossover design: low load RE at 30% of one repetition maximum (1RM), high load RE (70% 1RM) and BFR-RE (30% 1RM) at a low and high pressure. BFR pressure was prescribed relative to limb occlusion pressure at 40% and 80% for the low- and high-pressure trials. Pressure pain thresholds (PPT) were assessed before, 5-min and 24-h following exercise in exercising and non-exercising muscles. Venous blood samples were collected at the same timepoints to determine plasma concentrations of beta-endorphin and 2-arachidonoylglycerol.
Results:
High pressure BFR-RE increased PPTs in the exercising limb to a greater extent than all other trials. Comparable systemic EIH effects were observed with HLRE and both BFR-RE trials. PPTs in the exercising limb remained elevated above baseline at 24-h post-exercise following both BFR-RE trials. Post-exercise plasma beta-endorphin concentration was elevated during the BFR-RE trials. No changes to 2-arachidonoylglycerol concentration were observed.
Conclusion:
High pressure BFR-RE causes a greater EIH response in the exercising limb that persists for up to 24-h following exercise. The reduction in pain sensitivity with BFR-RE is partly driven by endogenous opioid production of beta-endorphin. BFR-RE should be introduced as a possible pain-modulation tool in individuals with acute and chronic pain.
Objectives:
The aim of this study was to compare the acute effects of isometric versus dynamic resistance exercise on pain during a pain-provoking activity, and exercise-induced hypoalgesia in participants with patellar tendinopathy.
Design:
This study was a pre-registered randomised crossover study. Participants were blinded to the study hypothesis.
Methods:
Participants (N = 21) performed a single session of high load isometric resistance exercise or dynamic resistance exercise, in a randomised order separated by a 7-day washout period. Outcomes were assessed before, immediately after, and 45 min post-exercise. The primary outcome was pain intensity scored on a numeric pain rating scale (NRS; 0-10) during a pain-provoking single leg decline squat (SLDS). Secondary outcomes were pressure pain thresholds (PPTs) locally, distally and remotely, as well as tendon thickness.
Results:
There was a significant decrease in pain NRS scores (mean reduction 0.9, NRS 95%CI 0.1-1.7; p = 0.028), and increase in PPTs at the tibialis anterior muscle (mean increase 34 kPa 95%CI 9.5-58.5; p = 0.009) immediately post-exercise. These were not sustained 45 min post-exercise for pain (NRS) or PPTs (p > 0.05). There were no differences between exercise on any outcome.
Conclusions:
While patients with patellar tendinopathy decreased pain during SLDS in response to resistance training, but the magnitude was small. Contraction mode may not be the most important factor in determining the magnitude of pain relieving effects. Similarly, there were only small increases in PPTs at the tibialis anterior which were not superior for isometric exercise.
Objective:
To investigate the influence of cuff width, sex, and applied pressure on the perceived discomfort associated with blood flow restriction at rest and following exercise.
Approach:
Experiment 1 (n = 96) consisted of four sets of biceps exercise to failure with a narrow and wide cuff inflated to the same relative pressure. Experiment 2 (n = 87) compared two wide cuffs, one of which was inflated to a relative pressure obtained from a narrow cuff. Experiment 3 (n = 50) compared the discomfort of wide and narrow cuffs at rest. Effects are presented as median δ (95% credible interval).
Main results:
There was no sex effect for any variable of interest. In Experiment 1, the narrow cuff resulted in less discomfort than the wide cuff (39.3 versus 42.5; median δ -0.388 (-0.670, -0.109)). Participants also rated the narrow cuff as more preferable. Experiment 2 found that a wide cuff inflated to a narrow cuffs pressure resulted in greater discomfort than a wide cuff (44 versus 40.9; median δ: 0.420 (0.118, 0.716)). Experiment 3 found no difference between cuff widths.
Significance:
Blood flow restricted exercise with a narrow cuff results in less discomfort than a wider cuff inflated to the same relative pressure. This effect is not observed at rest and suggests that the wide cuff produces a differential environment compared to a narrow cuff when combined with exercise. Additionally, applying a pressure meant for a narrow cuff to a wide cuff augments the applied pressure and subsequent discomfort to blood flow restricted exercise.
This study analyzed the effects of ischemic preconditioning (IPC) on muscle force capabilities. 16 male subjects participated in this randomized, cross-over, sham-controlled study. They were assigned to either IPC (3x5 minutes at 220 mmHg in both arms with 5 minute-rests) or a sham intervention (SHAM) (occlusion pressure set at 10 mmHg). 40 minutes later, their force capabilities on the bench press exercise were assessed (load-velocity relationship with light, moderate and heavy loads [30, 50 and 70% body weight, respectively]; one repetition maximum [1RM]; and number of repetitions to failure in three sets with 60%RM). The skin temperature (Tsk) of the pectoral and biceps muscles was analyzed as a secondary endpoint by means of infrared thermography. A significant decrease in the Tsk of the pectoral and biceps muscles was observed after the intervention (p<0.01) and before the warm-up (p<0.05) in IPC, but not in SHAM. However, exercise resulted in a similar Tsk increase in the pectoral muscles in both conditions (p>0.05). No significant differences (p>0.05 for all) were observed between conditions in the mean velocity attained with light (1.11±0.11 and 1.09±0.14 m·s-1, respectively), moderate (0.83±0.14 and 0.83±0.16 m·s-1) nor heavy loads (0.56±0.17 and 0.54±0.16 m·s-1), in 1RM (75.0±18.9 and 73.1±15.0 kg for IPC and SHAM, respectively; p=0.181), nor in the number of repetitions performed (52±13 and 54±16 repetitions, p=0.492). In summary, IPC decreased Tsk locally (biceps) and remotely (pectoral). However, it did not alter muscle force capabilities nor the Tsk response to exercise.
Objective:
To evaluate if a single blood flow restriction (BFR)-exercise bout would induce hypoalgaesia in patients with anterior knee pain (AKP) and allow painless application of therapeutic exercise.
Design:
Cross-sectional repeated measures design.
Setting:
Institutional out-patients physiotherapy clinic.
Patients:
Convenience sample of 30 AKP patients.
Intervention:
BFR was applied at 80% of complete vascular occlusion. Four sets of low-load open kinetic chain knee extensions were implemented using a pain monitoring model.
Main outcome measurements:
Pain (0-10) was assessed immediately after BFR application and after a physiotherapy session (45 min) during shallow and deep single-leg squat (SSLS, DSLS), and step-down test (SDT). To estimate the patient rating of clinical effectiveness, previously described thresholds for pain change (≥40%) were used, with appropriate adjustments for baseline pain levels.
Results:
Significant effects were found with greater pain relief immediate after BFR in SSLS (d = 0.61, p < 0.001), DSLS (d = 0.61, p < 0.001), and SDT (d = 0.60, p < 0.001). Time analysis revealed that pain reduction was sustained after the physiotherapy session for all tests (d(SSLS) = 0.60, d(DSLS) = 0.60, d(SDT) = 0.58, all p < 0.001). The reduction in pain effect size was found to be clinically significant in both post-BFR assessments.
Conclusion:
A single BFR-exercise bout immediately reduced AKP with the effect sustained for at least 45 min.
originally developed with the aim of protecting cardiac muscle fibers from sustained ischemic insults, local or remote acute ischemic preconditioning (IP) consists of a potent endogenous mechanism that has been shown to protect various tissues and organs against ischemia-reperfusion injury ([16][1
Ischemic preconditioning (IPC) enhances whole-body exercise endurance. However, it is poorly understood whether the beneficial effects originate from systemic (e. g., cardiovascular system) or peripheral (e. g., skeletal muscle) adaptations. The present study examined the effects of IPC on local muscle endurance during fatiguing isometric exercise. 12 male subjects performed sustained isometric unilateral knee-extension exercise at 20% of maximal voluntary contraction until failure. Prior to the exercise, subjects completed IPC or control (CON) treatments. During exercise trial, electromyography activity and near-infrared spectroscopy-derived deoxygenation in skeletal muscle were continuously recorded. Endurance time to task failure was significantly longer in IPC than in CON (mean±SE; 233±9 vs. 198±9 s, P<0.001). Quadriceps electromyography activity was not significantly different between IPC and CON. In contrast, deoxygenation dynamics in the quadriceps vastus lateralis muscle was significantly faster in IPC than in CON (27.1±3.4 vs. 35.0±3.6 s, P<0.01). The present study found that IPC can enhance muscular endurance during fatiguing isometric exercise. Moreover, IPC accelerated muscle deoxygenation dynamics during the exercise. Therefore, we suggest that the origin of beneficial effects of IPC on exercise performance may be the enhanced mitochondrial metabolism in skeletal muscle.
© Georg Thieme Verlag KG Stuttgart · New York.
Purpose:
This study investigated the effects of ischemic preconditioning (IPC) on the ratings of perceived exertion (RPE), surface electromyography (EMG), and pulmonary oxygen uptake (V̇O2) onset kinetics during cycling until exhaustion at the peak power output attained during an incremental test (PPO).
Methods:
A group of 12 recreationally trained cyclists volunteered for this study. After determination of PPO, they were randomly subjected on different days to a performance protocol preceded by intermittent bilateral cuff pressure inflation to 220 mm Hg (IPC) or 20 mm Hg (control). To increase data reliability, the performance visits were replicated, also in a random manner.
Results:
There was an 8.0% improvement in performance after IPC (Control: 303 s, IPC 327 s, factor SDs of ×/÷1.13, P = 0.01). This change was followed by a 2.9% increase in peak V̇O2 (Control: 3.95 L·min(-1), IPC: 4.06 L·min(-1), factor SDs of ×/÷ 1.15, P = 0.04) owing to a higher amplitude of the slow component of the V̇O2 kinetics (Control: 0.45 L·min(-1), IPC: 0.63 L·min(-1), factor SDs of ×/÷ 2.21, P = 0.05). There was also an attenuation in the rate of increase in RPE (P = 0.01) and a progressive increase in the myoelectrical activity of the vastus lateralis muscle (P = 0.04). Furthermore, the changes in peak V̇O2 (r = 0.73, P = 0.007) and the amplitude of the slow component (r = 0.79, P = 0.002) largely correlated with performance improvement.
Conclusion:
These findings provide a link between improved aerobic metabolism and enhanced severe-intensity cycling performance after IPC. Furthermore, the delayed exhaustion after IPC under lower RPE and higher skeletal muscle activation suggest they have a role on the ergogenic effects of IPC on endurance performance.
Although the amount of evidence demonstrating the beneficial effects of ischemic preconditioning (IPC) on exercise performance is increasing, conclusions about its efficacy cannot yet be drawn. Therefore, the purposes of this review were to determine the effect of IPC on exercise performance and identify the effects of different IPC procedures, exercise types, and subjects' characteristics on exercise performance. The analysis comprised 19 relevant studies from 2000-2015, 15 of which were included in the meta-analyses. Effect sizes (ES) were calculated as the standardized mean difference. Overall, IPC had a small beneficial effect on exercise performance (ES = 0.43; 90% confidence interval [CI], 0.28-0.51). The largest ES were found for aerobic (ES = 0.51; 90% CI, 0.35 - 0.67) and anaerobic (ES = 0.23; 90% CI, -0.12 - 0.58) exercise. In contrast, an unclear effect was observed in power and sprint performance (ES = 0.16; 90% CI, -0.20 - 0.52). In conclusion, IPC can effectively enhance aerobic and anaerobic exercise performance.
Purpose:
To determine what factors should be accounted for when setting the blood flow restriction (BFR) cuff pressure for the upper and lower body.
Methods:
One hundred and seventy one participants visited the laboratory for one testing session. Arm circumference, muscle (MTH) and fat (FTH) thickness were measured on the upper arm. Next, brachial systolic (SBP) and diastolic (DBP) blood pressure measurements were taken in the supine position. Upper body arterial occlusion was then determined using a Doppler probe. Following this, thigh circumference and lower body arterial occlusion were determined. Models of hierarchical linear regression were used to determine the greatest predictor of arterial occlusion in the upper and lower body. Two models were employed in the upper body, a Field (arm size) and a Laboratory model (arm composition).
Results:
The Laboratory model explained 58 % of the variance in arterial occlusion with SBP (β = 0.512, part = 0.255), MTH (β = 0.363, part = 0.233), and FTH (β = 0.248, part = 0.213) contributing similarly to explained variance. The Field model explained 60 % of the variance in arterial occlusion with arm circumference explaining the greatest amount (β = 0.419, part = 0.314) compared to SBP (β = 0.394, part = 0.266) and DBP (β = 0.147, part = 0.125). For the lower body model the third block explained 49 % of the variance in arterial occlusion with thigh circumference (β = 0.579, part = 0.570) and SBP (β = 0.281, part = 0.231) being significant predictors.
Conclusions:
Our findings indicate that arm circumference and SBP should be taken into account when determining BFR cuff pressures. In addition, we confirmed our previous study that thigh circumference is the greatest predictor of arterial occlusion in the lower body.
Ischemic preconditioning (IPC) of one or two limbs improves performance of exercise that recruits the same limb(s). However, it is unclear whether IPC application to another limb than that in exercise is also effective and which mechanisms are involved. We investigated the effect of remote IPC (RIPC) on muscle fatigue, time to task failure, forearm hemodynamics, and deoxygenation during handgrip exercise. Thirteen men underwent RIPC in the lower limbs or a control intervention (CON), in random order, and then performed a constant load rhythmic handgrip protocol until task failure. Rates of contraction and relaxation (ΔForce/ΔTime) were used as indices of fatigue. Brachial artery blood flow and conductance, besides forearm microvascular deoxygenation, were assessed during exercise. RIPC attenuated the slowing of contraction and relaxation throughout exercise (P < 0.05 vs CON) and increased time to task failure by 11.2% (95% confidence interval: 0.7–21.7%, P <0.05 vs CON). There was no significant difference in blood flow, conductance, and deoxygenation between conditions throughout exercise (P > 0.05). In conclusion, RIPC applied to the lower limbs delayed the development of fatigue during handgrip exercise, prolonged time to task failure, but was not accompanied by changes in forearm hemodynamics and deoxygenation.
To remain independent and healthy, an important factor to consider is the maintenance of skeletal muscle mass. Inactivity leads to measurable changes in muscle and bone, reduces exercise capacity, impairs the immune system, and decreases the sensitivity to insulin. Therefore, maintaining physical activity is of great importance for skeletal muscle health. One form of structured physical activity is resistance training. Generally speaking, one needs to lift weights at approximately 70% of their one repetition maximum (1RM) to have noticeable increases in muscle size and strength. Although numerous positive effects are observed from heavy resistance training, some at risk populations (e.g. elderly, rehabilitating patients, etc.) might be advised not to perform high-load resistance training and may be limited to performance of low-load resistance exercise. A technique which applies pressure cuffs to the limbs causing blood flow restriction (BFR) has been shown to attenuate atrophy and when combined with low intensity exercise has resulted in an increase in both muscle size and strength across different age groups. We have provided an evidence based model of progression from bed rest to higher load resistance training, based largely on BFR literature concentrating on more at risk populations, to highlight a possible path to recovery.
We have previously shown that a brief episode of ischemia slows the rate of ATP depletion during subsequent ischemic episodes. Additionally, intermittent reperfusion may be beneficial to the myocardium by washing out catabolites that have accumulated during ischemia. Thus, we proposed that multiple brief ischemic episodes might actually protect the heart from a subsequent sustained ischemic insult. To test this hypothesis, two sets of experiments were performed. In the first set, one group of dogs (n = 7) was preconditioned with four 5 min circumflex occlusions, each separated by 5 min of reperfusion, followed by a sustained 40 min occlusion. The control group (n = 5) received a single 40 min occlusion. In the second study, an identical preconditioning protocol was followed, and animals (n = 9) then received a sustained 3 hr occlusion. Control animals (n = 7) received a single 3 hr occlusion. Animals were allowed 4 days of reperfusion thereafter. Histologic infarct size then was measured and was related to the major baseline predictors of infarct size, including the anatomic area at risk and collateral blood flow. In the 40 min study, preconditioning with ischemia paradoxically limited infarct size to 25% of that seen in the control group (p less than .001). Collateral blood flows were not significantly different in the two groups. In the 3 hr study, there was no difference between infarct size in the preconditioned and control groups. The protective effect of preconditioning in the 40 min study may have been due to reduced ATP depletion and/or to reduced catabolite accumulation during the sustained occlusion. These results suggest that the multiple anginal episodes that often precede myocardial infarction in man may delay cell death after coronary occlusion, and thereby allow for greater salvage of myocardium through reperfusion therapy.
Ischaemic preconditioning (short periods of ischaemia with intermittent reperfusion) has been shown paradoxically to protect the myocardium from a subsequent longer ischaemic insult. The protection associated with preconditioning is one of the most powerful mechanisms of protection known and has been shown in every animal species investigated. However, there is no direct evidence that ischaemic preconditioning occurs in the human heart. We studied whether it was possible to precondition the human heart in a setting of coronary artery bypass surgery. The measurement of adenosine triphosphate in biopsy specimens was used as our endpoint. We believe that our results are the first to show that it may be possible to precondition and protect the human myocardium with short controlled periods of intermittent ischaemia and reperfusion.
