added 15 research items
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.
The current manuscript sets out a series of guidelines for blood flow restriction exercise, focusing on the methodology, application and safety of this mode of training. With the emergence of this technique and the wide variety of applications within the literature, the aim of this review is to set out a current research informed guide to blood flow restriction training to practitioners. This covers the use of blood flow restriction to enhance muscular strength and hypertrophy via training with resistance and aerobic exercise and preventing muscle atrophy using the technique passively. The authorship team for this article was selected from the researchers focused in blood flow restriction training research with expertise in exercise science, strength and conditioning and sports medicine.
Blood flow restriction (BFR) training involves the intentional reduction of blood flow during exercise and is increasingly recognized as an effective method for inducing muscular adaptation when using low-load resistance exercise (LL-RE). Previous work has demonstrated LL-RE to induce similar adaptations to low-load BFR when both are performed to repetition failure and when the restriction is applied continuously from the first to last set (LL-CONT). However, LL-CONT results in considerably more pain than LL-RE, and could prevent individuals from reaching maximal repetitions. Repetitionmatched LL-RE with intermittent BFR during rest periods (LL-INT) has been shown to reduce the pain compared with LL-CONT. Thus, LL-INT may offer BFR benefits while maximizing exercise quality and quantity by reducing pain. The purpose of this study was to examine the physiological and performance related effects caused by variations of continuous and intermittent BFR performed to repetition failure. Nine participants completed 3 sets of unilateral squats to failure under 3 conditions: LL-RE, LL-CONT, and LL-INT. Perceived pain was measured with a visual analog scale after each set and rest. Muscular stress was quantified using exercise volume and tissue saturation via nearinfrared spectroscopy. There was a rest x condition interaction for pain during rest between exercise sets (p<0.05). Following the rest period after the second set ratings of pain were greater in LL-CONT than LL-INT (LL-CONT:331±220a.u., LL-INT:270±146a.u; p=0.06) and were lower in LL-REG than LL-INT (LL-INT:270±146a.u, LLRE: 134±144a.u; p=0.04). Exercise volume to failure differed across all three groups (LLCONT: 933±369kg, LL-INT: 1306±468kg, LL-RE:1475±548kg; all p<0.05) and tissue saturation index (TSI) was similarly low during exercise under all conditions (LLCONT: 45±5%, LL-INT:45 ± 6%, LL-RE:47±6%; p=0.4). During rest periods, TSI was reduced in LL-CONT and LL-INT compared to LL_RE (LL-CONT: 55±7%, LL-INT: 50±8%, LL-RE: 63±3%; all p<0.05) due to greater deoxygenated hemoglobin content (DeoxyHb; LL-CONT:36.5±10.2μM, LL-INT:40.1±13.7μM, LL RE:24.0±5.7μM; all p<0.05). These results suggest that LL-INT allows for greater exercise volume than LLCONT and similar muscular stress to LL-CONT. Future work should evaluate if different adaptations occur between modalities with repeated exposure.
Ischemic pre-conditioning (IPC) was initially developed to protect the myocardium from ischemia through altered cardiocyte metabolism. Due to the observed effects on metabolism and oxygen kinetics, IPC gained interest as a potential ergogenic aid in sport. Limited research evaluating the effects of IPC on maximal short-duration activities has been performed and of the existing literature, mixed outcomes resulting from intra-subject variation may have clouded the efficacy of this technique for enhancing sprint performance. Therefore, the current study employed a randomized repeated-measures crossover design with IPC, placebo (SHAM), and control conditions while using sprint-trained athletes (n=18) to determine the effect of IPC (3 x 5 min occlusions, with 5min reperfusion), concluding fifteen minutes prior to maximal 10 and 20 m sprinting. A visual analogue scale was used in conjunction with the sprint trials to evaluate any possible placebo effect on performance. Despite a "significantly beneficial" perception of the IPC treatment compared with the SHAM trials (P < 0.001), no changes in sprint performance were observed following either the IPC or SHAM conditions over 10 m (IPC Δ = <0.01s ± 0.02s, SHAM Δ = <0.01s ± 0.02s) or 20 m (IPC Δ = -0.01s ± 0.03s, SHAM Δ = <0.01s ± 0.03s) compared to control. Thus, an IPC protocol does not improve 10 or 20 m sprint performance in sprint-trained athletes.
Purpose: To identify the combined effect of increasing tissue level oxygen consumption and metabolite accumulation on the ergogenic efficacy of ischemic preconditioning (IPC) during both maximal aerobic and maximal anaerobic exercise. Methods: Twelve healthy males (22 ± 2 years, 179 ± 2 cm, 80 ± 10 kg, 48 ± 4 ml.kg−1.min⁻¹) underwent four experimental conditions: (i) no IPC control, (ii) traditional IPC, (iii) IPC with EMS, and (iv) IPC with treadmill walking. IPC involved bilateral leg occlusion at 220 mmHg for 5 min, repeated three times, separated by 5 min of reperfusion. Within 10 min following the IPC procedures, a 30 s Wingate test and subsequent (after 25 min rest) incremental maximal aerobic test were performed on a cycle ergometer. Results: There was no statistical difference in anaerobic peak power between the no IPC control (1211 ± 290 W), traditional IPC (1209 ± 300 W), IPC + EMS (1206 ± 311 W), and IPC + Walk (1220 ± 288 W; P = 0.7); nor did VO2max change between no IPC control (48 ± 2 ml.kg⁻¹.min⁻¹), traditional IPC (48 ± 6 ml.kg⁻¹.min⁻¹), IPC + EMS (49 ± 4 ml.kg⁻¹.min⁻¹) and IPC + Walk (48 ± 6 ml.kg⁻¹.min⁻¹; P = 0.3). However, the maximal watts during the VO2max increased when IPC was combined with both EMS (304 ± 38 W) and walking (308 ± 40 W) compared to traditional IPC (296 ± 39 W) and no IPC control (293 ± 48 W; P = 0.02). Conclusion: This study shows that in a group of participants for whom a traditional IPC stimulus was not effective, the magnification of the IPC stress through muscle contractions while under occlusion led to a subsequent exercise performance response. These findings support that amplification of the ischemic preconditioning stimulus augments the effect for exercise capacity.
There is a growing body of research suggesting that low intensity resistance training, completed under reduced blood flow by external compressive force on the vasculature, can elicit adaptations similar to traditional resistance training, but at a significantly reduced exercise intensity. Blood flow restriction (BFR) training was developed as a method of maintaining skeletal muscle mass in the ageing population, but advances in this area of research have broadened its application for use in both performance and rehabilitative populations. There are several proposed mechanistic theories; however, a definitive explanation is still unclear. The purpose of this narrative review is to discuss the use of blood flow restriction in performance and rehabilitative applications, examine potential mechanisms of action, and review areas of limitation within research practices. This article also examines BFR training during transient involuntary muscle contractions evoked by transcutaneous electrical muscle stimulation as a novel training intervention for individuals with reduced motor capability. BFR is an attractive training method that could be considered as an effective modality for use by appropriately trained health and fitness practitioners, especially those working with individuals that require modified resistance training programming.
Objectives: To systematically search and assess studies that have combined blood flow restriction (BFR) with exercise, and to perform meta-analysis of the reported results to quantify the effectiveness of BFR exercise on muscle strength and hypertrophy. Design: A systematic review. Methods: A computer assisted database search was conducted for articles investigating the effect of exercise combined with BFR on muscle hypertrophy and strength. A total of 916 hits were screened in order based on title, abstract, and full article, resulting in 47 articles that fit the review criteria. Results: A total of 400 participants were included from 19 different studies measuring muscle strength increases when exercise is combined with BFR. Exercise was separated into aerobic and resistance exercise. Resulting from BFR aerobic exercise, there was a mean strength improvement of 0.4Nm between the experimental group and control group, while BFR resistance exercise resulted in a mean improvement of 0.3kg. A total of 377 participants were included in 19 studies measuring muscle size increase (cross sectional area) when exercise was combined with BFR. The mean difference in muscle size between the experimental group and control group was 0.4cm(2). Conclusion: Current evidence suggests that the addition of BFR to dynamic exercise training is effective for augmenting changes in both muscle strength and size. This effect was consistent for both resistance training and aerobically-based exercise, although the effect sizes varied. The magnitude of observed changes are noteworthy, particularly considering the relatively short duration of the average intervention.
Background Ischemic preconditioning (IPC) is the exposure to brief periods of circulatory occlusion and reperfusion in order to protect local or systemic organs against subsequent bouts of ischemia. IPC has also been proposed as a novel intervention to improve exercise performance in healthy and diseased populations. Objective The purpose of this systematic review is to analyze the evidence for IPC improving exercise performance in healthy humans. Methods Data were obtained using a systematic computer-assisted search of four electronic databases (MEDLINE, PubMed, SPORTDiscus, CINAHL), from January 1985 to October 2015, and relevant reference lists. Results Twenty-one studies met the inclusion criteria. The collective data suggest that IPC is a safe intervention that may be capable of improving time-trial performance. Available individual data from included studies demonstrate that IPC improved time-trial performance in 67 % of participants, with comparable results in athletes and recreationally active populations. The effects of IPC on power output, oxygen consumption, rating of perceived exertion, blood lactate accumulation, and cardiorespiratory measures are unclear. The within-study heterogeneity may suggest the presence of IPC responders and non-responders, which in combination with small sample sizes, likely confound interpretation of mean group data in the literature. Conclusion The ability of IPC to improve time-trial performance is promising, but the potential mechanisms responsible require further investigation. Future work should be directed toward identifying the individual phenotype and protocol that will best exploit IPC-mediated exercise performance improvements, facilitating its application in sport settings.