Ischemic Preconditioning: Modulating Pain Sensitivity and Exercise Performance

Blood flow restriction as a post-exercise recovery strategy: A systematic review of the current status of the literature

The aim of this study was to systematically review the current literature on blood flow restriction (BFR) as a post-exercise recovery strategy. Experimental studies investigating the effect of BFR on recovery after exercise were included. Only studies meeting the following inclusion criteria were selected: (a) studies investigating about BFR as a post-exercise recovery strategy in athletes and healthy individuals; (b) the full text being available in English; (c) experimental research study design. Studies that exclusively analyzed BFR as a recovery strategy during the exercise (e.g., recovery strategy between bouts of exercise) were excluded. A literature review was conducted on the PubMed, Cochrane, and Web of Science electronic databases up until May 7th, 2023. The main findings were that (i) 9 studies investigated passive BFR as a post-exercise recovery strategy, which shows a significant lack of research in both team and individual sports (especially in female populations), and only 2 studies used active BFR protocols; (ii) although a high quality range of studies was observed, there were methodological limitations such as BFR interventions that were usually conducted after fatiguing protocols or fitness tests, which may not represent the real exercise (e.g., a sprint session of 6 sets of 50 m may induce muscle damage but it does not represent the demands of a team sport like rugby or soccer); (iii) there is a lack of consistency in BFR protocols (e.g., number of cycles or duration of the occlusion-reperfusion periods) for recovery; (iv) some studies showed beneficial effects while others found no positive or detrimental effects of BFR as a post-exercise recovery strategy in comparison with the control/SHAM group. In conclusion, only 11 studies investigated BFR as a post-exercise recovery strategy and there is not any significant amount of evidence in team or individual sports (especially in female populations). BFR could be a potential post-exercise recovery strategy, but practitioners should use caution when applying this method of recovery for their athletes and clients. In addition, it would be of interest for high performance-related practitioners to have a better understanding of the benefits of BFR interventions combined with either active or passive forms of exercise as a post-exercise recovery strategy.

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 38(5): 864-872, 2024-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.

Remote ischaemic preconditioning increase tolerance to experimentally induced cold pain

Ischaemic preconditioning (IPC) applied locally and remotely has been shown to reduce pain which may underpin its ergogenic effect on exercise performance, however, it is unclear how many IPC cycles are needed to induce hypoalgesia. Therefore the purpose of this study was to examine the number of cycles of IPC on experimental pain perception. Sixteen healthy participants underwent four, randomised, experimental sessions where they either underwent a sham protocol (1 × 5 min at 20 mmHg), and 1, 2 or 3 cycles × 5 min of remote IPC at 105% of limb occlusion pressure. Ten minutes post-intervention, participants underwent a cold-pressor test where pain threshold, pain tolerance and pain intensity were examined and compared between conditions with a one-way repeated measure analysis of variance. Pain threshold was not different between conditions (P = 0.065); but pain tolerance was increased by ∼30% in the 1 × 5 condition, 2 × 5 condition, and 3 × 5 condition compared to the sham condition. No differences in pain tolerance were seen between the different numbers of cycles (all P > 0.05). There was also no difference in the perception of pain 30 s into the cold pressor test (P = 0.279). Remote IPC appears to significantly improve tolerance to pain which may have significant implications for endurance performance and exercise rehabilitation, but this warrants further investigation.

Intra- and interindividual reliability of muscle pain induced by an intramuscular injection of hypertonic saline injection into the quadriceps

BACKGROUND

Intramuscular injections of hypertonic saline are commonly used to induce experimental muscle pain, but reliability data on this technique are lacking. This study investigated the intra- and interindividual reliability of pain measures from a hypertonic saline injection into the vastus lateralis.

METHODS

Fourteen healthy participants (6 female) attended three laboratory visits where they received an intramuscular injection of 1 mL hypertonic saline into the vastus lateralis. Changes in pain intensity were recorded on an electronic visual analogue scale, and pain quality was assessed after pain had resolved. Reliability was assessed with the coefficient of variation (CV), minimum detectable change (MDC) and intraclass correlation coefficient (ICC) with 95% CIs.

RESULTS

Mean pain intensity displayed high levels of intraindividual variability (CV = 16.3 [10.5-22.0]%) and 'poor' to 'very good' relative reliability (ICC = 0.71 [0.45-0.88]) but had a MDC of 11 [8-16] au (out of 100). Peak pain intensity exhibited high levels of intraindividual variability (CV = 14.8 [8.8-20.8]%) with 'moderate' to 'excellent' levels of relative reliability (ICC = 0.81 [0.62-0.92]), whereas the MDC was 18 [14-26] au. Measures of pain quality exhibited good reliability. Interindividual variability in pain measures was high (CV > 37%).

CONCLUSIONS

Intramuscular injections of 1 mL of hypertonic saline into the vastus lateralis display substantial levels of interindividual variability, but MDC is below the clinically important changes in pain. This model of experimental pain is suitable for studies involving repeated exposures.

SIGNIFICANCE

Many pain research studies have performed intramuscular injections of hypertonic saline to investigate responses to muscle pain. However, the reliability of this technique is not well established. We examined the pain response over three repeated sessions of a hypertonic saline injection. The pain induced by hypertonic saline has considerable interindividual variability but has largely acceptable intraindividual reliability. Therefore, the injections of hypertonic saline to induce muscle pain are a reliable model of experimental muscle pain.