Hypoxia Does Not Impair Resistance Exercise Performance or Amplify Post-Exercise Fatigue.

Purpose: To determine whether performing resistance exercise in hypoxia acutely reduces performance and increases markers of fatigue, and whether these responses are exaggerated if exercising at high versus low work rates (i.e., exercising to failure or volume matched non-failure). Methods: Following a within-subject design, 20 men completed two trials in hypoxia (13% oxygen) and two in normoxia (21% oxygen). The first session for hypoxic and normoxic conditions comprised six sets of bench press and shoulder press to failure (high work rate), while subsequent sessions involved the same volume distributed over 12 sets (low work rate). Physical performance (concentric velocity) and perceptual responses were measured during exercise and for 72 hr post-exercise. Neuromuscular performance (bench throw velocity) was assessed pre- and post-session. Results: Hypoxia did not affect physical performance, neuromuscular performance, and perceptual recovery when exercising at high or low work rates. Higher work rate exercise caused greater acute decrements in physical performance and post-exercise neuromuscular performance and increased perceived exertion and muscle soreness (p ≤ 0.006), irrespective of hypoxia. Conclusions: Hypoxia does not impact on resistance exercise performance or increase markers of physical and perceptual fatigue. Higher exercise work rates may impair physical performance, and exaggerate fatigue compared to low work rate exercise, irrespective of environmental condition. Practitioners can prescribe hypoxic resistance exercise without compromising physical performance or inducing greater levels of fatigue. For athletes who are required to train with high frequency, decreasing exercise work rate may reduce post-exercise markers of fatigue for the same training volume.

Blood flow restricted walking alters gait kinematics.

This study investigated the impact of blood flow restriction (BFR) during treadmill walking on gait kinematics. Twenty-one participants completed one familiarisation and four experimental sessions, including two walking speeds (moderate [5.0 ± 0.3km·h-1] and fast [6.4 ± 0.4km·h-1]) and two occlusion conditions (BFR [60% of arterial occlusion pressure] and unrestricted). For each exercise intensity, the BFR session was performed first. Participants were instructed to walk as long as possible, with sessions capped at 20 min. Unrestricted sessions were time-matched, and the order of exercise intensity was randomised. Kinematics were collected over 10s every minute using retro-reflective markers affixed to specific body landmarks. Ratings of perceived exertion and discomfort were collected every two minutes. Blood samples were collected from the fingertip pre-exercise and the finger and toe post-exercise, and were analysed for lactate, electrolytes, and markers of cell-membrane damage. During the BFR sessions the cuffs remained inflated while the blood samples were collected. Fast-walk BFR sessions exhibited higher anterior trunk flexion (p = 0.001) and knee flexion during stance (p = 0.001) compared to all other sessions. Step width was increased during BFR sessions (p = 0.001), but no difference in step length (p = 0.300) or cadence (p = 0.922) were observed. The time required to elicit change in anterior trunk flexion and plantar-flexion angle at toe-off was shorter during BFR sessions (p = 0.024). The BFR sessions elicited the highest ratings of perceived exertion and discomfort, as well as blood lactate concentration (p ≤ 0.001). Application of BFR during moderate and fast treadmill walking modifies gait kinematics and exacerbates exercise-related sensations as well as blood lactate concentration.

Applying blood flow restriction changes walking kinematics, causing an overall increase in anterior trunk flexion and knee flexion during stance while simultaneously reducing plantar-flexion angle at toe-off and ankle joint velocity.Applying blood flow restriction exacerbate exercise-related sensations of exertion and discomfort.Sample site does not influence the level of post-exercise blood lactate or markers of cell-membrane potential and damage.

Low- to moderate-intensity blood flow restricted walking is not an acute equivalent for unrestricted jogging in young active adults.

This study investigated whether walking with blood flow restriction (BFR) increases acute cardio-respiratory demands to the point that it can be considered an alternative for jogging. Sixteen physically active adults completed five experimental sessions (order randomised), comprising 10 min of treadmill exercise. Two sessions included unrestricted walking, two sessions required walking with BFR cuffs positioned on the lower limbs inflated to 60% of individualised arterial occlusion pressure, and one session was conducted at a jogging pace. Comfortable walking and jogging speeds were calculated during the familiarisation session. Walking speeds were individualised to either 100% (speed: 6.0 ± 0.3km·h-1[low-intensity]) or 120% (speed: 7.2 ± 0.3km·h-1[moderate-intensity]) of comfortable walking speed. The jogging session was unrestricted (speed: 9.1 ± 0.7km·h-1). Initial analysis compared walking conditions across heart rate, left cardiac work index, systolic blood pressure, relative oxygen consumption, minute ventilation, rating of perceived exertion and limb discomfort. Secondary analysis compared the walking session with the highest cardio-respiratory demands to jogging. Initial analysis identified that moderate-intensity with BFR induced the highest cardio-respiratory and perceptual responses compared with any other walking sessions (p < 0.01). Secondary analysis revealed that all cardio-respiratory measures were higher during jogging when compared with moderate-intensity with BFR (p < 0.01), except systolic blood pressure (p = 0.10). All perceptual measures were higher during moderate-intensity with BFR (p < 0.01) compared with jogging. Low- to moderate-intensity BFR-walking produces lower acute cardio-respiratory responses at higher ratings of perceived exertion and discomfort compared with jogging. Overall, BFR-walking does not seem to provide an equivalent exercise modality for unrestricted jogging in physically active adults.HighlightsIn young active adults, walking with blood flow restriction increases cardio-respiratory demands, yet not to a level equivalent to jogging.Moderate-intensity blood flow restricted walking elicits higher exercise-related sensation of exertion and leg discomfort than jogging.Blood flow restriction application increases exercise severity whereby moderate-intensity BFR-walking and jogging are both considered vigorous-intensity exercise.

Does the application of blood flow restriction during walking exercise influence the accuracy of indirect calorimetry?

OBJECTIVES: Identify whether the application of blood flow restriction (BFR) during walking influences fraction of expired oxygen (FeO2) and carbon dioxide (FeCO2) measures, key variables in the calculation of oxygen consumption (V̇O2) via indirect calorimetry. DESIGN: Randomised cross-over. METHODS: On separate visits, sixteen participants completed four experimental sessions (order randomised), each comprising 10 min of treadmill exercise; i.e., with or without BFR (60% arterial occlusion pressure) combined with two different intensity levels (100% or 120% comfortable walking speed). For data analysis, walking speeds within the same condition (with or without BFR) were pooled, and the speed variance was controlled within the statistical model. The FeO2, FeCO2, V̇O2, volume of carbon dioxide production, minute ventilation (V̇E) and respiratory exchange ratio were extracted from the metabolic cart from the fifth min of the exercise period to the 3 min post-exercise. Measures were averaged across 2 min increments during exercise and 1 min increments post-exercise. RESULTS: Condition × time interactions were observed for FeO2 (p < 0.01) and FeCO2 (p < 0.01). Post hoc analysis identified within the BFR condition an increase in FeO2 (p < 0.01) during the exercise period and for 2 min post-exercise, while FeCO2 was decreased (p < 0.01) during the exercise period and 1 min post-exercise. A main effect of BFR and time was observed for V̇E (p ≤ 0.044) and V̇O2 (p ≤ 0.01). CONCLUSIONS: The increase of FeO2 and decrease of FeCO2 during BFR walking likely reduces the validity of V̇O2 values calculated via indirect calorimetry.

Sessional work-rate does not affect the magnitude to which simulated hypoxia can augment acute physiological responses during resistance exercise.

PURPOSE: To investigate whether performing resistance exercise in hypoxia augments physiological and perceptual responses, and if altering work-rate by performing repetitions to failure compared to sub-maximally increases the magnitude of these responses. METHODS: Twenty male university students (minimum of 2 year resistance training experience) completed four sessions, two in hypoxia (fraction of inspired oxygen [FiO2] = 0.13), and two in normoxia (FiO2 = 0.21). For each condition, session one comprised three sets to failure of shoulder press and bench press (high work-rate session), while session two involved the same volume load, distributed over six sets (low work-rate session). Muscle oxygenation (triceps brachii), surface electromyographic activity (anterior deltoid, pectoralis major, and triceps brachii), heart rate (HR), and arterial blood oxygen saturation were recorded. Blood lactate concentration ([Bla-]) was recorded pre-exercise and 2 min after each exercise. Muscle thickness was measured pre- and post-exercise via ultrasound. RESULTS: Muscle oxygenation values during sets and inter-set rest periods were lower in hypoxia vs normoxia (p = 0.001). Hypoxia caused greater [Bla-] during the shoulder press of failure sessions (p = 0.003) and both shoulder press (p = 0.048) and bench press (p = 0.005) of non-failure sessions. Hypoxia increased HR during non-failure sessions (p < 0.001). There was no effect of hypoxia on muscular swelling, surface electromyographic activity, perceived exertion, or number of repetitions performed. CONCLUSIONS: Hypoxia augmented metabolite accumulation, but had no impact on any other physiological or perceptual response compared to the equivalent exercise in normoxia. Furthermore, the magnitude to which hypoxia increased the measured physiological responses was not influenced by sessional work-rate.