Characterization of muscle oxygenation response to vascular occlusion: implications for remote ischaemic preconditioning and physical Performance

Influence of cuff stiffness on hemodynamics and perceived cuff pressure in the upper extremities in males and females: implications for practical blood flow restriction training

BACKGROUND

Practical blood flow restriction (pBFR) during exercise is a cost-saving alternative to traditional blood flow restriction using pneumatic cuffs, particularly when exercising in a group setting. Depending on the pBFR technique, several factors (e.g., cuff width, limb circumference) have already been shown to be of importance when applying the pBFR pressure. Given that elastic cuffs are often used for pBFR, the cuff stiffness might be an additional influencing factor. Therefore, the present study compared the acute effects of three elastic cuffs with identical width but different stiffness (high stiffness (HS), medium stiffness (MS), and low stiffness (LS)) on hemodynamic measures and perceived cuff pressure at rest.

METHODS

In a randomized, counter-balanced cross-over study, 36 young and normotensive participants completed three experimental trials. After a 10-min rest period in supine position, the cuff was loosely and proximally applied to the right upper arm. Following baseline data recording, the cuff was successively tightened in 10%-increments with respect to the limb circumference (%overlap) until arterial blood flow was occluded. At baseline and during each %overlap, systolic peak blood flow velocity of the brachial artery, rating of perceived cuff pressure, as well as muscle oxygen saturation and total hemoglobin concentration of the biceps brachii muscle were recorded.

RESULTS

The %overlap required to occlude arterial blood flow was different between the three cuffs (HS: 30.9 ± 3.8%, MS: 43.9 ± 6.1%, LS: 54.5 ± 8.3%). Furthermore, at 30% overlap, systolic peak blood flow velocity was lower when applying the HS (9.0 ± 10.9 cm∙s- 1) compared to MS (48.9 ± 21.9 cm∙s- 1) and LS cuff (62.9 ± 19.1 cm∙s- 1). Rating of perceived cuff pressure at 30% overlap was higher when using the HS (6.5 ± 1.5 arbitrary unit (a.u.)) compared to MS (5.1 ± 1.4 a.u.) and LS cuff (4.9 ± 1.5 a.u.) with no difference between the MS and LS cuff. However, muscle oxygen saturation and total hemoglobin concentration were not different between the three cuffs.

CONCLUSIONS

The present study revealed that the cuff stiffness influenced blood flow velocity and arterial occlusion pressure. Therefore, cuff stiffness seems an important factor for the application of pBFR.

Effects of blood flow restriction on mechanical properties of the rectus femoris muscle at rest

Introduction: This study examined the effects of blood flow restriction (BFR) and reperfusion on the mechanical properties of the rectus femoris muscle at rest (frequency and stiffness). Methods: Fourteen trained men (body weight = 81.0 ± 10.3 kg; BMI = 25 ± 3.0 m/kg2; height = 181 ± 4 cm; training experience = 6.0 ± 2.2 years) participated in an experimental session involving their dominant (BFR) and non-dominant leg (control). Muscle mechanical properties were measured using Myoton's accelerometer at the midpoint of the rectus femoris muscle at five time points. In the BFR leg, an 80% arterial occlusion pressure was applied by a cuff for 5 min. No cuff was applied in the control leg. Femoral Myoton measurements were taken from both legs 2 and 4 min after the start of BRF as well as 30 s and 2 min after the end of the occlusion period. Results: The two-way ANOVA revealed a statistically significant interaction effect for stiffness and frequency (p < 0.001; η2 > 0.67). The post hoc analysis showed that both stiffness and frequency increased during BFR compared with rest and then dropped to the resting levels post BFR period. Also, stiffness and frequency were higher than control only during the BFR period, and similar during rest and post BFR. Conclusion: These results indicate that the application of BFR at rest leads to significant changes in mechanical properties of the rectus femoris muscle.

Ischemic preconditioning and exercise performance: are the psychophysiological responses underestimated?

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.

Physiological ischemic training improves cardiac function through the attenuation of cardiomyocyte apoptosis and the activation of the vagus nerve in chronic heart failure

Purpose

This study investigated the functional outcomes of patients with chronic heart failure (CHF) after physiological ischemic training (PIT), identified the optimal PIT protocol, evaluated its cardioprotective effects and explored the underlying neural mechanisms.

Methods

Patients with CHF were randomly divided into experimental group (n = 25, PIT intervention + regular treatment) and control group (n = 25, regular treatment). The outcomes included the left ventricular ejection fraction (LVEF), brain natriuretic peptide (BNP) and cardiopulmonary parameters. LVEF and cardiac biomarkers in CHF rats after various PIT treatments (different in intensity, frequency, and course of treatment) were measured to identify the optimal PIT protocol. The effect of PIT on cardiomyocyte programmed cell death was investigated by western blot, flow cytometry and fluorescent staining. The neural mechanism involved in PIT-induced cardioprotective effect was assessed by stimulation of the vagus nerve and muscarinic M₂ receptor in CHF rats.

Results

LVEF and VO₂max increased while BNP decreased in patients subjected to PIT. The optimal PIT protocol in CHF rats was composed of five cycles of 5 min ischemia followed by 5 min reperfusion on remote limbs for 8 weeks. LVEF and cardiac biomarker levels were significantly improved, and cardiomyocyte apoptosis was inhibited. However, these cardioprotective effects disappeared after subjecting CHF rats to vagotomy or muscarinic M₂ receptor inhibition.

Conclusion

PIT improved functional outcomes in CHF patients. The optimal PIT protocol required appropriate intensity, reasonable frequency, and adequate treatment course. Under these conditions, improvement of cardiac function in CHF was confirmed through cardiomyocyte apoptosis reduction and vagus nerve activation.

Does sex influence near-infrared spectroscopy-derived indicators of microvascular reactivity and the response to acute dietary capsaicin

Endothelial dysfunction is associated with cardiovascular disease development, nitric oxide (NO) deficiencies, and may be limb or sex-specific. Prior in vitro work indicated that the transient receptor potential vanilloid channel-1 (TRPV₁) is expressed in human arteries and the TRPV₁ agonist capsaicin alters vasodilation in an endothelium-dependent manner; however, it is unknown if this translates in vivo or is limb or sex-dependent. Therefore, we sought to determine if there was limb or sex-specificity in the effect of capsaicin on microvascular function using near-infrared spectroscopy (NIRS)-derived tissue oxygen saturation (StO₂) reperfusion slope. In a blinded placebo-controlled crossover design, 45 young males (M: n = 25) and females (F: n = 20), the reperfusion slopes of the forearm and quadriceps were assessed, and a urine sample obtained to assay for nitrate/nitrite (NOx) concentrations and antioxidant capacity after acutely ingesting placebo or capsaicin. Under placebo, females had greater reperfusion rates in both the forearm (M: 0.44 ± 0.24 vs. F: 0.98 ± 0.46 %/sec; p = 0.002, d = -1.50) and quadricep (M: 0.86 ± 0.31 vs. F: 1.17 ± 0.43 %/sec; p = 0.010, d = -0.85). Capsaicin decreased microvascular responsiveness in the forearm of females (placebo: 0.98 ± 0.45 vs. capsaicin: 0.84 ± 0.45 %/sec) as compared to males (placebo: 0.45 ± 0.24 vs. capsaicin: 0.38 ± 0.16 %/sec, interaction p < 0.001, η² = 0.475). There was a sex*treatment interaction for NOx concentrations, where males increased (placebo: 21.13 ± 12.83 vs. capsaicin: 23.82 ± 13.34 μM), while females decreased (placebo: 22.78 ± 14.40 vs. capsaicin: 14.43 ± 10.01 μM; p = 0.037, η² = 0.042). Using NIRS to assess microvascular function, there is apparent limb and sex-specificity, and, for the first-time, document that acute oral capsaicin alters reperfusion slope in a sexually divergent manner.

Effectiveness of either short-duration ischemic pre-conditioning, single-set high-resistance exercise, or their combination in potentiating bench press exercise performance

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.

Potential physiological responses contributing to the ergogenic effects of acute ischemic preconditioning during exercise: A narrative review

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.

Ischaemic preconditioning improves upper-body endurance performance without altering ⩒O2 kinetics

PURPOSE

Whilst pre-exercise ischaemic preconditioning (IPC) can improve lower-body exercise performance, its impact on upper-limb performance has received little attention. This study examines the influence of IPC on upper-body exercise performance and oxygen uptake (⩒O₂) kinetics.

METHODS

Eleven recreationally-active males (24 ± 2 years) completed an arm-crank graded exercise test to exhaustion to determine the power outputs at the ventilatory thresholds (VT1 and VT2) and ⩒O_2peak (40.0 ± 7.4 ml·kg^-1·min^-1). Four main trials were conducted, two following IPC (4 × 5-min, 220 mmHg contralateral upper-limb occlusion), the other two following SHAM (4 × 5-min, 20 mmHg). The first two trials consisted of a 15-minute constant work rate and the last two time-to-exhaustion (TTE) arm-crank tests at the power equivalents of 95% VT1 (LOW) and VT2 (HIGH), respectively. Pulmonary ⩒O₂ kinetics, heart rate, blood-lactate concentration, and rating of perceived exertion were recorded throughout exercise.

RESULTS

TTE during HIGH was longer following IPC than SHAM (459 ± 115 vs 395 ± 102 s, p = 0.004). Mean response time and change in ⩒O₂ between 2-min and end exercise (Δ⩒O₂) were not different between IPC and SHAM for arm-cranking at both LOW (80.3 ± 19.0 vs 90.3 ± 23.5 s [p = 0.06], 457 ± 184 vs 443 ± 245 ml [p = 0.83]) and HIGH (96.6 ± 31.2 vs 92.1 ± 24.4 s [p = 0.65], 617 ± 321 vs 649 ± 230 ml [p = 0.74]). Heart rate, blood-lactate concentration, and rating of perceived exertion did not differ between conditions (all p≥0.05).

CONCLUSION

TTE was longer following IPC during upper-body exercise despite unchanged ⩒O₂ kinetics.

Intra- and Inter-Day Reliability of the NIRS Portamon Device after Three Induced Muscle Ischemias

(1) Background: Near-infrared spectroscopy (NIRS) is an innovative and non-invasive technology used to investigate muscular oxygenation. The aim of this study is to assess the within- and between-session reliability of the NIRS Portamon (Artinis, Elst, Netherlands) device following three sets of induced muscle ischemia. (2) Methods: Depending on the experimental group (G1, G2 or G3), a cuff was inflated three times on the left upper arm to 50 mmHg (G1), systolic blood pressure (SBP) + 50 mmHg (G2) or 250 mmHg (G3). Maximum, minimum and reoxygenation rate values were assessed after each occlusion phase, using a Portamon device placed on the left brachioradialis. Reliability was assessed with intraclass correlation coefficient (ICC) value and ICC 95% confidence interval (CI-95%), coefficient of variation (CV) and standard error of measurement (SEM) (3) Results: Our results showed a good to excellent reliability for maximums and minimums within-session. However, the reoxygenation rate within sessions as well as measurements between sessions cannot predominantly show good reliability. (4) Conclusions: Multiple measurements of maximums and minimums within a single session appeared to be reliable which shows that only one measurement is necessary to assess these parameters. However, it is necessary to be cautious with a comparison of maximum, minimum and reoxygenation rate values between sessions.

Ischemic preconditioning has no effect on maximal arm cycling exercise in women

PURPOSE

We investigated the effect of ischemic preconditioning (IPC) on performance of a 3 min maximal effort arm ergometer test in young women.

METHODS

Twenty healthy women (23.1 (SD 3.3) years) performed a 3 min maximal effort arm cycling exercise, preceded by IPC on both arms or SHAM in a counterbalanced randomized crossover design. Both blood flow (via high resolution ultrasound; n = 17) and muscle oxygenation/deoxygenation (via near infrared spectroscopy; n = 5) were measured throughout the IPC/SHAM. Performance and perceptual/physiological (i.e., heart rate, blood lactate, rating of perceived exertion, and triceps brachialis oxygenation) parameters were recorded during the exercise test.

RESULTS

Occlusion during IPC completely blocked brachial artery blood flow, decreased oxygenated hemoglobin/myoglobin (Δ[oxy(Hb + Mb)]), and increased deoxygenated Hb/Mb (Δ[deoxy(Hb + Mb)]). There were no differences (P > 0.797) in performance (peak, mean, and end power output) or in any perceptual/physiological variables during the 3 min all-out test between IPC/SHAM. During exercise, Δ[oxy(Hb + Mb)] initially decreased with no differences (P ≥ 0.296) between conditions and returned towards baseline by the completion of the test while Δ[deoxy(Hb + Mb)] increased with no differences between conditions and remained elevated until completion of the test (P ≥ 0.755).

CONCLUSIONS

We verified the successful application of IPC via blood flow and NIRS measures but found no effects on performance of a 3 min maximal effort arm cranking test in young women.

Effects of inspiratory muscle warm-up on locomotor muscle oxygenation in elite speed skaters during 3000 m time trials

PURPOSE

It has been shown that an inspiratory muscle warm-up (IMW) could enhance performance. IMW may also improve the near-infrared spectroscopy (NIRS)-derived tissue oxygen saturation index (TSI) during cycling. However, there exists contradictory data about the effect of this conditioning strategy on performance and muscle oxygenation. We examined the effect of IMW on speed skating performance and studied the underpinning physiological mechanisms related to muscle oxygenation.

METHODS

In a crossover, randomized, single-blind study, eight elite speed skaters performed 3000 m on-ice time trials, preceded by either IMW (2 × 30 breaths, 40% maximal inspiratory pressure) or SHAM (2 × 30 breaths, 15% maximal inspiratory pressure). Changes in TSI, oxyhemoglobin-oxymyoglobin ([O₂HbMb]), deoxyhemoglobin-deoxymyoglobin ([HHbMb]), total hemoglobin-myoglobin ([THbMb]) and HHbMbdiff ([O₂HbMb]-[HHbMb]) in the right vastus lateralis muscle were monitored by NIRS. All variables were compared at different time points of the race simulation with repeated-measures analysis of variance. Differences between IMW and SHAM were also analyzed using Cohen's effect size (ES) ± 90% confidence limits, and magnitude-based inferences.

RESULTS

Compared with SHAM, IMW had no clear impact on skating time (IMW 262.88 ± 17.62 s vs. SHAM 264.05 ± 21.12 s, effect size (ES) 0.05; 90% confidence limits, - 0.22, 0.32, p = 0.7366), TSI, HbMbdiff, [THbMb], [O₂HbMb] and perceptual responses.

CONCLUSIONS

IMW did not modify skating time during a 3000 m time trial in speed skaters, in the conditions of our study. The unchanged [THbMb] and TSI demonstrate that the mechanisms by which IMW could possibly exert an effect on performance were unaffected by this intervention.

Oxygenation time course and neuromuscular fatigue during repeated cycling sprints with bilateral blood flow restriction

The aim was to evaluate changes in peripheral and cerebral oxygenation, cardiorespiratory, and performance differences, as well as neuromuscular fatigue across multiple levels of blood flow restriction (BFR) during a repeated cycling sprint test to exhaustion (RST). Participants performed three RST (10-sec maximal sprints with 20-sec recovery until exhaustion) with measurements of power output and V̇O2peak as well as oxygenation (near-infrared spectroscopy) of the vastus lateralis and prefrontal cortex. Neuromuscular fatigue was assessed by femoral nerve stimulation to evoke the vastus lateralis. Tests were conducted with proximal lower limb bilateral vascular occlusion at 0%, 45%, and 60% of resting pulse elimination pressure. Total work decreased with BFR (52.5 ± 22.9% at 45%, 68.6 ± 32.6% at 60%, P < 0.01 compared with 0%) as V̇O2peak (12.6 ± 9.3% at 45%, 18.2 ± 7.2% at 60%, compared with 0%, P < 0.01). Decreased changes in muscle deoxyhemoglobin (∆[HHb]) during sprints were demonstrated at 60% compared to 0% (P < 0.001). Changes in total hemoglobin concentrations (∆[tHb]) increased at both 45% and 60% compared with 0% (P < 0.001). Cerebral ∆[tHb] increased toward exhaustion (P < 0.05). Maximal voluntary contraction (MVC), voluntary activation level (VAL), and root mean square (RMS)/M-wave ratio decreased at 60% compared with 0% (P < 0.001, all). MVC and VAL decreased between 45% and 60% (P < 0.05, both). The application of BFR during RST induced greater changes in tissue perfusion (via blood volume, ∆[tHb]) suggesting a possible stimulus for vascular blood flow regulation. Additionally, high-intensity sprint exercise with partial ischemia may challenge cerebral blood flow regulation and influence local fatigue development due to protection of cerebral function.

Influence and reliability of lower-limb arterial occlusion pressure at different body positions

Background

Total arterial occlusive pressure (AOP) is used to prescribe pressures for surgery, blood flow restriction exercise (BFRE) and ischemic preconditioning (IPC). AOP is often measured in a supine position; however, the influence of body position on AOP measurement is unknown and may influence level of occlusion in different positions during BFR and IPC. The aim of this study was therefore to investigate the influence of body position on AOP.

Methods

Fifty healthy individuals (age = 29 ± 6 y) underwent AOP measurements on the dominant lower-limb in supine, seated and standing positions in a randomised order. AOP was measured automatically using the Delfi Personalised Tourniquet System device, with each measurement separated by 5 min of rest.

Results

Arterial occlusive pressure was significantly lower in the supine position compared to the seated position (187.00 ± 32.5 vs 204.00 ± 28.5 mmHg, p < 0.001) and standing position (187.00 ± 32.5 vs 241.50 ± 49.3 mmHg, p < 0.001). AOP was significantly higher in the standing position compared to the seated position (241.50 ± 49.3 vs 204.00 ± 28.5 mmHg, p < 0.001).

Discussion

Arterial occlusive pressure measurement is body position dependent, thus for accurate prescription of occlusion pressure during surgery, BFR and IPC, AOP should be measured in the position intended for subsequent application of occlusion.

Factors affecting occlusion pressure and ischemic preconditioning

PURPOSE

To determine the effect of limb selection (upper/lower), cuff width (small (6 cm)/medium (13 cm) upper; medium/large (18 cm) lower) and anthropometry on arterial occlusion pressure (AOP) in ischemic preconditioning (IPC).

METHODS

Twenty athletes (10 females and 10 males) had surface anthropometry and dual x-ray absorptiometry (DXA) assessments before using Doppler ultrasound to confirm AOP for each limb. Subsequently, 5 min of occlusion occurred, with near-infrared spectroscopy (NIRS) measuring muscle oxygenation changes. Resultant AOP was compared between sexes, limbs and cuff sizes using linear regression models.

RESULTS

Mean AOP was higher in the lower limbs than the upper limbs (161 ± 18 vs. 133 ± 12 mm Hg; p < .001), and with smaller cuffs in upper (161 ± 16 vs. 133 ± 12 mm Hg; p < .001), but not lower limbs (161 ± 16 vs. 170 ± 26 mm Hg; p = .222). Sex and resting systolic blood pressure (SBP) accounted for 77% (small cuff) to 83% (medium cuff) of variance in AOP for upper limbs, and 61% (medium cuff) to 63% (large cuff) in lower limbs. Including anthropometry accounted for 82% (small cuff) to 89% (medium cuff) and 78% (medium cuff) to 79% (large cuff) of variance for upper and lower limbs, respectively. Adding DXA variables improved the explained variance up to 83% (small cuff) to 91% (medium cuff) and 79% (medium cuff) to 87% (large cuff) for upper and lower limbs, respectively. NIRS data showed significantly greater tissue oxygenation changes in upper versus lower limbs.

CONCLUSIONS

The AOP in athletes is dependent on limb occluded, sex, SBP, limb and cuff size, and body composition.

Exercise-Induced Cardioprotection and the Therapeutic Potential of RIPC

In the search for innovative solutions to treat ischemic heart disease, recent basic science and clinical approaches have focused on remote ischemic preconditioning (RIPC). Remote ischemic preconditioning involves short intervals of limb blood flow occlusion by the application of a blood pressure cuff inflated to a suprasystolic pressure. The promise of RIPC in the development of new cardioprotective therapies is founded on the premise that it is cost-effective, technically simple, and overcomes many logistical and biochemical hurdles associated with other ischemic preconditioning approaches. However, RIPC as a research subarea is still in its infancy and clinical applications for individuals at high risk of cardiovascular disease remain elusive. The thesis of the current review is that observational and mechanistic similarities between exercise-induced preconditioning and RIPC may reveal novel therapeutic links to cardioprotection. While reductionist understanding of the exercised heart is still in the formative stages, available mechanistic knowledge of exercise-induced cardioprotection is juxtaposed to RIPC and potential implications discussed. In total, additional research is needed in order to fully appreciate the mechanistic and translative connections between exercise and RIPC. Nonetheless, existing rationale are strong and suggest that RIPC approaches may be helpful in the development and application to pharmacologic interventions in those with ischemic heart disease.