Ischemic Preconditioning and Muscle Force Capabilities

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.

Can Adipose Tissue Influence the Evaluation of Thermographic Images in Adolescents?

Infrared thermography (IRT) is a technology easy to use for clinical purposes as a pre-diagnostic tool for many health conditions. However, the analysis process of a thermographic image needs to be meticulous to make an appropriate decision. The adipose tissue is considered a potential influence factor in the skin temperature (Tsk) values obtained by IRT. This study aimed to verify the influence of body fat percentage (%BF) on Tsk measured by IRT in male adolescents. A total of 100 adolescents (16.79 ± 0.97 years old and body mass index of 18.41 ± 2.32 kg/m²) was divided into two groups through the results of a dual-energy X-ray absorptiometry analysis: obese (n = 50, %BF 30.21 ± 3.79) and non-obese (n = 50, %BF 11.33 ± 3.08). Thermograms were obtained by a FLIR T420 infrared camera and analyzed by ThermoHuman^® software version 2.12, subdividing the body into seven regions of interest (ROI). The results showed that obese adolescents presented lower mean Tsk values than the non-obese for all ROIs (p < 0.05), with emphasis on the global Tsk (0.91 °C) and anterior (1.28 °C) and posterior trunk (1.18 °C), with "very large" effect size values. A negative correlation was observed in all the ROI (p < 0.01), mainly in the anterior (r = -0.71, p < 0.001) and posterior trunk (r = -0.65, p < 0.001). Tables of thermal normality were proposed for different ROIs according to the classification of obesity. In conclusion, the %BF affects the registered Tsk values in male Brazilian adolescents assessed by IRT.

Correlation between the range of motion of the tibiotarsal joint and blood circulation in the lower limbs in diabetic individuals

OBJECTIVE

The aim of this study was to evaluate the relationship between the range of motion and lower-limb hemodynamic indices in the tibiotarsal joint of individuals with diabetic neuropathy.

METHODS

Twenty volunteers of both sexes, with a mean age of 61.45±7.05 years, were diagnosed with type 2 diabetes mellitus and diabetic peripheral neuropathy. Arterial blood flow was assessed using Doppler ultrasound, and the variables such as average velocity, pulsatility index, and resistivity index were also evaluated. A range of dorsiflexion and plantar flexion joint movements were assessed using digital goniometry before and after exercise. Data distribution was assessed using the Shapiro-Wilk test, followed by Pearson's correlation for normal data and Spearman's correlation for non-normal data, in order to verify the association between variables.

RESULTS

A moderate correlation was found between dorsiflexion and pulse rate on two occasions before (rs=0.497) and after initial evaluation (rs=0.511). A low correlation was found between plantar flexion and mean velocity (rs=-0.357), pulsatility index (rs=0.439), and resistivity index (rs=0.328); dorsiflexion and mean velocity (rs=0.374), pulse rate (rs=0.332), and resistance index (rs=0.327) before evaluation, and peak (rs=0.346) was observed after the evaluation of blood circulation.

CONCLUSION

There is a correlation between the range of motion of the tibiotarsal joint and the blood circulation of diabetics, ranging from moderate to poor for the different variables evaluated.

THE INFLUENCE OF ISCHEMIC PRECONDITIONING ON NEUROMUSCULAR PERFORMANCE

ABSTRACT Introduction: Ischemic preconditioning (IPC) has been described in the literature as a resource capable of improving physical performance. Objective: The purpose of this randomized double-blind study was to evaluate the influence of IPC on the neuromuscular performance of trained individuals. Methods: Twenty-four (24) resistance training participants (6 of them women) with a mean age of 25.8 ± 4.6 years were selected and divided into two groups: the upper limb group (ULG) composed of 12 individuals (4 women) and the lower limb group (LLG) composed of 12 individuals (2 women). The maximum repetitions test was applied in the bench press for the ULG and in the 45° leg press for the LLG, with 50% of the one-repetition maximum under control, placebo and IPC conditions, at a random interval of 72 hours between tests. The IPC was applied four hours before the tests by means of an analog sphygmomanometer cuff inflated to 220 mmHg on the arm for the ULG and on the thigh for LLG, with three cycles of five minutes each of ischemia and reperfusion, alternating between the right and left sides. For the placebo, the cuff was inflated to 40 mmHg without causing ischemia. The significance level for the Wilcoxon test was p <0.017, due to the Bonferroni correction. The effect size (ES) was also analyzed. Results: With IPC, the ULG performed 34.8 ± 4.8 repetitions, representing an improvement of 11.29% (IPC vs. control, ES = 0.68 and p = 0.002) and the LLG performed 40.5 ± 15.7 repetitions, representing an improvement of 37.47% (IPC vs. control, ES = 0.84 and p = 0.002). No significant improvements were observed for the placebo in either group. Conclusion: Our data showed that IPC positively influenced neuromuscular performance of both the upper and lower limbs. Level of evidence II; Therapeutic studies investigating the results of treatment (Prospectived comparative studye).

Does ischemic preconditioning really improve performance or it is just a placebo effect?

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.

Methodological Variations Contributing to Heterogenous Ergogenic Responses to Ischemic Preconditioning

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