Attenuation of Neuromuscular Fatigue by Ischemic Preconditioning with Moderate Cuff Pressure is Not Related to Muscle Oxygen Saturation in Men

Ischemic preconditioning (IPC) has been an excellent strategy for enhancing sports performance recovery, although there is still no consensus on the ideal protocol. Thus, this study aimed to evaluate the effects of IPC with different cuff pressures (low pressure, medium pressure, and high pressure) on the attenuation of neuromuscular fatigue after an isometric test protocol. And to verify whether this improvement was related to muscle oxygen saturation during the test protocol. Thirty males (18-35 years old) with experience in resistance training were allocated to three different groups: low pressure (20 mmHg), medium pressure (100 mmHg), and high pressure (190 mmHg). The individual occlusion pressure of each participant was identified using ultrasound. Each participant performed two test protocols (8 maximal isometric contractions lasting 20-s with a 10-s rest interval) in an extension chair; after the first test protocol, the participant received the IPC intervention with a low, medium, or high cuff pressure or received the noncuff intervention (randomized order). Only the medium-pressure group showed a smaller decrease in mean force change compared to the no-cuff condition (-4.40% vs. -13.10%, p=0.01, respectively), and the low- and high-pressure groups did not exhibit significant pressure differences (IPC vs. noncuff: -8.40% vs. -13.10%, p=0.11 and -9.10% vs. -14.70%, p=0.12, respectively). Muscle oxygen saturation across test protocols showed no significant differences in all IPC conditions (p>0.05). Although, IPC with medium pressure was effective at optimizing the recovery of neuromuscular performance, this improvement is not related to an increase in muscle oxygen saturation during exercise.

Is Ischemic Preconditioning Intervention Occlusion-Dependent to Enhance Resistance Exercise Performance?

ABSTRACT

de Souza, HLR, Arriel, RA, Hohl, R, da Mota, GR, and Marocolo, M. Is ischemic preconditioning intervention occlusion-dependent to enhance resistance exercise performance? J Strength Cond Res 35(10): 2706-2712, 2021-Ischemic preconditioning is a rising technique with potential to improve performance. Currently, its effects are still controversial, and a placebo effect seems to have a role. In this sense, this study evaluated the effect of high-pressure (HP) and low-pressure (LP) cuffing on resistance exercise performance during repeated 5-day intervention. Twenty healthy trained men (24.0 ± 4.4 years; 80.1 ± 12.2 kg; and 176.9 ± 6.6 cm) performed a 1 repetition maximum (1RM) test before interventions. Maximal isometric force test, number of repetitions (75% 1RM), total workload (sets × reps × load), fatigue index (FI) ([set 1 - set 3]/set 1 × 100), and perceived scales were assessed during knee extension preceded by HP (3 × 5-minute unilateral leg occlusion at 50 mm Hg above systolic blood pressure), LP (3 × 5-minute unilateral leg occlusion at 20 mm Hg), or control ([CON] 30-minute resting). The main effect of cuff intervention was significant for total workload (F(1,16) = 4.2, p = 0.03) after adjusting for baseline (analysis of covariance). Adjusted means (confidence interval) and effect sizes (ES) indicate that HP (1778 kg [1,613-1944]; ES: 0.29) and LP (1761 kg [1,590-1932]; ES: 0.34) significantly increased total workload compared with CON (1,452 kg [1,262-1,643]; ES: 0.17). Finally, isometric force and FI were similar for all conditions (HP, LP, and CON) with no difference from baseline performance. In conclusion, the short-term (5-day) intervention of HP and LP cuffing increases the total workload. This effect in muscle endurance performance is nondependent of blood flow occlusion, since LP is not able to obstruct arterial blood flow. A likely motivational effect cannot be ruled out.

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.

Ischemic preconditioning improves performance and accelerates the heart rate recovery

BACKGROUND

Previous studies have assessed the effects of ischemic preconditioning (IPC) on exercise performance and physiological variables, such as lactate and muscle deoxygenation. In this study, we verified the IPC effects on performance and heart rate during and immediately after a maximal incremental cycling test (ICT).

METHODS

Eighteen recreationally trained cyclists (28±4 years) were allocated to one of three groups: IPC, SHAM and Control. After the first visit to familiarization, cyclists attended the laboratory on two separate occasions to perform an ICT: in the 1^st visit they performed the reference test (baseline), and in 2^nd the test ischemic preconditioning (2 cycles of 5-min occlusion [at 50 mm Hg above systolic arterial pressure]/ 5-min reperfusion), SHAM (identical to ischemic preconditioning, but at 20 mm Hg) or control (no occlusion) interventions (post intervention). During the ICT, heart rate, power output and perceived exertion were measured and the heart rate was monitored throughout the recovery.

RESULTS

Only ischemic preconditioning group improved performance time by 4.9±4.0% and decreased heart rate at submaximal point during ICT, of 170±8 to 166±8 bpm (P<0.05). Also, IPC promoted faster heart rate recovery, mainly on first minute (from 151±9 to 145±8 bpm; P<0.05), compared to baseline. No differences for other parameters were found.

CONCLUSIONS

Two cycles of five minutes of ischemia were relevant to produce positive effects on performance and alter the heart rate during and soon after ICT.