Speeding of oxygen uptake kinetics is not different following low-intensity blood-flow-restricted and high-intensity interval training

A Review of the Efficacy and Mechanisms of Blood Flow Restriction Training in Enhancing Somatic Function and Preventing Falls in Older Adults

Falls have become an important public health problem that seriously affects the quality of survival of older adults and are a major cause of fractures, death, and reduced quality of life. With the advent of an aging society, the social, economic, and medical burdens of falls in older adults are increasing. Currently, there is a lack of effective means to prevent falls in older adults, and traditional health education and clinical interventions are not effective. It is urgent to find a safe and effective training method that can improve balance function and is suitable for the elderly. Low-intensity blood flow restriction training (BFRT) is an emerging training modality that, by restricting blood flow to the limbs and combining it with low-intensity exercise, can effectively improve muscle mass, aerobic capacity, and bone density, and has been shown to enhance somatic function in older adults. However, the effectiveness and specific mechanisms of BFRT in preventing falls in older adults are unclear. Based on recent research progress, this paper explores the possibility of BFRT in preventing falls in older adults by analyzing its positive effects on muscle mass, balance function, and cognitive function, the risk factors of falling in the elderly are summarized, as well as its potential role in reducing fall risk factors. It aims to provide new thinking for academia and clinical practice and to provide a scientific basis for reducing the risk of falls in the elderly.

Aerobic capacity and [Formula: see text] kinetics adaptive responses to short-term high-intensity interval training and detraining in untrained females

PURPOSE

This study investigated the physical fitness and oxygen uptake kinetics (τ[Formula: see text]) along with the O2 delivery and utilization (heart rate kinetics, τHR; deoxyhemoglobin/[Formula: see text] ratio, ∆[HHb]/[Formula: see text]) adaptations of untrained female participants responding to 4 weeks of high-intensity interval training (HIIT) and 2 weeks of detraining.

METHODS

Participants were randomly assigned to HIIT (n = 11, 4 × 4 protocol) or nonexercising control (n = 9) groups. Exercising group engaged 4 weeks of treadmill HIIT followed by 2 weeks of detraining while maintaining daily activity level. Ramp-incremental (RI) tests and step-transitions to moderate-intensity exercise were performed. Aerobic capacity and performance (maximal oxygen uptake, [Formula: see text]; gas-exchange threshold, GET; power output, PO), body composition (skeletal muscle mass, SMM; body fat percentage, BF%), muscle oxygenation status (∆[HHb]), [Formula: see text], and HR kinetics were assessed.

RESULTS

HIIT elicited improvements in aerobic capacity ([Formula: see text], + 0.17 ± 0.04 L/min; GET, + 0.18 ± 0.05 L/min, P < 0.01; PO-[Formula: see text], ± 23.36 ± 8.37 W; PO-GET, + 17.18 ± 3.07 W, P < 0.05), body composition (SMM, + 0.92 ± 0.17 kg; BF%, - 3.08% ± 0.58%, P < 0.001), and speed up the τ[Formula: see text] (- 8.04 ± 1.57 s, P < 0.001) significantly, extending to better ∆[HHb]/[Formula: see text] ratio (1.18 ± 0.08 to 1.05 ± 0.14). After a period of detraining, the adaptation in body composition and aerobic capacity, as well as the accelerated τ[Formula: see text] were maintained in the HIIT group, but the PO-[Formula: see text] and PO-GET declined below the post-training level (P < 0.05), whereas no changes were reported in controls (P > 0.05). Four weeks of HIIT induced widespread physiological adaptations in females, and the majority of improvements were preserved after 2 weeks of detraining except for power output corresponding to [Formula: see text] and GET.

Adaptations to 4 weeks of high-intensity interval training in healthy adults with different training backgrounds

PURPOSE

This study investigated the physical fitness and oxygen uptake kinetics ([Formula: see text]) along with the exercise-onset O₂ delivery (heart rate kinetics, τHR; changes in normalized deoxyhemoglobin/[Formula: see text] ratio, Δ[HHb]/[Formula: see text]) adaptations of individuals with different physical activity (PA) backgrounds responding to 4 weeks of high-intensity interval training (HIIT), and the possible effects of skeletal muscle mass (SMM) on training-induced adaptations.

METHODS

Twenty subjects (10 high-PA level, HIIT-H; 10 moderate-PA level, HIIT-M) engaged in 4 weeks of treadmill HIIT. Ramp-incremental (RI) test and step-transitions to moderate-intensity exercise were performed. Cardiorespiratory fitness, body composition, muscle oxygenation status, VO₂ and HR kinetics were assessed at baseline and post-training.

RESULTS

HIIT improved fitness status for HIIT-H ([Formula: see text], + 0.26 ± 0.07 L/min; SMM, + 0.66 ± 0.70 kg; body fat, - 1.52 ± 1.93 kg; [Formula: see text], - 7.11 ± 1.05 s, p < 0.05) and HIIT-M ([Formula: see text], 0.24 ± 0.07 L/min, SMM, + 0.58 ± 0.61 kg; body fat, - 1.64 ± 1.37 kg; [Formula: see text], - 5.48 ± 1.05 s, p < 0.05) except for visceral fat area (p = 0.293) without between-group differences (p > 0.05). Oxygenated and deoxygenated hemoglobin amplitude during the RI test increased for both groups (p < 0.05) except for total hemoglobin (p = 0.179). The Δ[HHb]/[Formula: see text] overshoot was attenuated for both groups (p < 0.05) but only eliminated in HIIT-H (1.05 ± 0.14 to 0.92 ± 0.11), and no change was observed in τHR (p = 0.144). Linear mixed-effect models presented positive effects of SMM on absolute [Formula: see text] (p < 0.001) and ΔHHb (p = 0.034).

CONCLUSION

Four weeks of HIIT promoted positive adaptations in physical fitness and [Formula: see text] kinetics, with the peripheral adaptations attributing to the observed improvements. The training effects are similar between groups suggesting that HIIT is effective for reaching higher physical fitness levels.

Blood flow restriction accelerates aerobic training-induced adaptation of [Formula: see text] kinetics at the onset of moderate-intensity exercise

It is unclear whether blood flow restriction (BFR) accelerates the adaptation of the time constant (τ) of phase II oxygen uptake ([Formula: see text]) kinetics in the moderate-intensity exercise domain via moderate-intensity aerobic training. Therefore, healthy participants underwent moderate-intensity [45-60% [Formula: see text] Reserve] aerobic cycle training with or without BFR (BFR group, n = 9; CON group, n = 9) for 8 weeks to evaluate [Formula: see text] kinetics during moderate-intensity cycle exercise before (Pre) and after 4 (Mid) and 8 (Post) weeks of training. Both groups trained for 30 min, 3 days weekly. BFR was performed for 5 min every 10 min by applying cuffs to the upper thighs. The τ significantly decreased by Mid in the BFR group (23.7 ± 2.9 s [Pre], 15.3 ± 1.8 s [Mid], 15.5 ± 1.4 s [Post], P < 0.01) and by Post in the CON group (27.5 ± 2.0 s [Pre], 22.1 ± 0.7 s [Mid], 18.5 ± 1.9 s [Post], P < 0.01). Notably, the BFR group's τ was significantly lower than that of the CON group at Mid (P < 0.01) but not at Post. In conclusion, BFR accelerates the adaptation of the [Formula: see text] kinetics of phase II by moderate-intensity aerobic training.

The Effect of Endurance Training on Pulmonary V˙O2 Kinetics in Solid Organs Transplanted Recipients

Background: We investigated the effects of single (SL-ET) and double leg (DL-ET) high-intensity interval training on O2 deficit (O2Def) and mean response time (MRT) during square-wave moderate-intensity exercise (DL-MOD), and on the amplitude of V˙O2p slow component (SCamp), during heavy intensity exercise (DL-HVY), on 33 patients (heart transplant = 13, kidney transplanted = 11 and liver transplanted = 9). Methods: Patients performed DL incremental step exercise to exhaustion, two DL-MOD tests, and a DL-HVY trial before and after 24 sessions of SL-ET (n = 17) or DL-ET (n = 16). Results: After SL-ET, O2Def, MRT and SCamp decreased by 16.4% ± 13.7 (p = 0.008), by 15.6% ± 13.7 (p = 0.004) and by 35% ± 31 (p = 0.002), respectively. After DL-ET, they dropped by 24.9% ± 16.2 (p < 0.0001), by 25.9% ± 13.6 (p < 0.0001) and by 38% ± 52 (p = 0.0003), respectively. The magnitude of improvement of O2Def, MRT, and SCamp was not significantly different between SL-ET and DL-ET after training. Conclusions: We conclude that SL-ET is as effective as DL-ET if we aim to improve V˙O2p kinetics in transplanted patients and suggest that the slower, V˙O2p kinetics is mainly caused by the impairment of peripherals exchanges likely due to the immunosuppressive medications and disuse.

Muscle Fatigue Is Attenuated When Applying Intermittent Compared With Continuous Blood Flow Restriction During Endurance Cycling

PURPOSE

The aim of this study was to identify a blood-flow-restriction (BFR) endurance exercise protocol that maximizes metabolic strain and minimizes muscle fatigue.

METHODS

Twelve healthy participants accomplished 5 different interval cycling endurance exercises (2-min work, 1-min rest) in a randomized order: (1) control, low intensity with unrestricted blood flow (CON30); (2) low intensity with intermittent BFR (i-BFR30, ∼150 mm Hg); (3) low intensity with continuous BFR (c-BFR, ∼100 mm Hg); (4) unloaded cycling with i-BFR0 (∼150 mm Hg); and (5) high intensity (HI) with unrestricted blood flow. Force production, creatine kinase activity, antioxidant markers, blood pH, and potassium (K+) were measured in a range of 5 minutes before and after each cycling exercise protocol.

RESULTS

HI showed the highest reduction (Δ = -0.26 [0.05], d = 5.6) on blood pH. Delta pH for c-BRF30 (Δ = -0.02 [0.03], d = 0.8) and Δ pH for i-BRF30 (Δ = -0.04 [0.03], d = 1.6) were different from each other, and both were higher compared with CON30 (Δ = 0.03 [0.03]). There was significant before-to-after force loss following HI (Δ = 55 [40] N·m-1, d = 1.5) and c-BFR30 (Δ = 27 [21] N·m-1, d = 0.7) protocols only, which were accompanied by significant increases in K+ (HI: Δ = 0.94 [0.65] mmol·L-1, d = 1.8; c-BFR30: Δ = 0.72 [0.85] mmol·L-1, d = 1.2). Moreover, all BFR conditions elicited slight increases in plasma creatine kinase, but not for HI and CON30. Glutathione changes from before to after were significant for all BFR conditions and HI, but not for CON30.

CONCLUSIONS

The attenuation in fatigue-induced reductions in maximal force suggests that i-BFR exercise could be preferable to c-BFR in improving exercise capacity, with considerably less biologic stress elicited from HI exercises.

Moderate-intensity exercise with blood flow restriction on cardiopulmonary kinetics and efficiency during a subsequent high-intensity exercise in young women: A cross-sectional study

Blood flow restriction (BFR) training applied prior to a subsequent exercise has been used as a method to induce changes in oxygen uptake pulmonary kinetics (O2P) and exercise performance. However, the effects of a moderate-intensity training associated with BFR on a subsequent high-intensity exercise on O2P and cardiac output (QT) kinetics, exercise tolerance, and efficiency remain unknown.This prospective physiologic study was performed at the Exercise Physiology Lab, University of Brasilia. Ten healthy females (mean ± SD values: age = 21.3 ± 2.2 years; height = 1.6 ± 0.07 m, and weight = 55.6 ± 8.8 kg) underwent moderate-intensity training associated with or without BFR for 6 minutes prior to a maximal high-intensity exercise bout. O2P, heart rate, and QT kinetics and gross efficiency were obtained during the high-intensity constant workload exercise test.No differences were observed in O2P, heart rate, and QT kinetics in the subsequent high-intensity exercise following BFR training. However, exercise tolerance and gross efficiency were significantly greater after BFR (220 ± 45 vs 136 ± 30 seconds; P < .05, and 32.8 ± 6.3 vs 27.1 ± 5.4%; P < .05, respectively), which also resulted in lower oxygen cost (1382 ± 227 vs 1695 ± 305 mL min-1).We concluded that moderate-intensity BFR training implemented prior to a high-intensity protocol did not accelerate subsequent O2P and QT kinetics, but it has the potential to improve both exercise tolerance and work efficiency at high workloads.

Blood flow restriction training and the high-performance athlete: science to application

The manipulation of blood flow in conjunction with skeletal muscle contraction has greatly informed the physiological understanding of muscle fatigue, blood pressure reflexes, and metabolism in humans. Recent interest in using intentional blood flow restriction (BFR) has focused on elucidating how exercise during periods of reduced blood flow affects typical training adaptations. A large initial appeal for BFR training was driven by studies demonstrating rapid increases in muscle size, strength, and endurance capacity, even when notably low intensities and resistances, which would typically be incapable of stimulating change in healthy populations, were used. The incorporation of BFR exercise into the training of strength- and endurance-trained athletes has recently been shown to provide additive training effects that augment skeletal muscle and cardiovascular adaptations. Recent observations suggest BFR exercise alters acute physiological stressors such as local muscle oxygen availability and vascular shear stress, which may lead to adaptations that are not easily attained with conventional training. This review explores these concepts and summarizes both the evidence base and knowledge gaps regarding the application of BFR training for athletes.