Effects of hyperoxia during recovery from 5×30-s bouts of maximal-intensity exercise

Acute psycho-physiological responses to submaximal constant-load cycling under intermittent hypoxia-hyperoxia vs. hypoxia-normoxia in young males

Background

Hypoxia and hyperoxia can affect the acute psycho-physiological response to exercise. Recording various perceptual responses to exercise is of particular importance for investigating behavioral changes to physical activity, given that the perception of exercise-induced pain, discomfort or unpleasure, and a low level of exercise enjoyment are commonly associated with a low adherence to physical activity. Therefore, this study aimed to compare the acute perceptual and physiological responses to aerobic exercise under intermittent hypoxia-hyperoxia (IHHT), hypoxia-normoxia (IHT), and sustained normoxia (NOR) in young, recreational active, healthy males.

Methods

Using a randomized, single-blinded, crossover design, 15 males (age: 24.5 ± 4.2 yrs) performed 40 min of submaximal constant-load cycling (at 60% peak oxygen uptake, 80 rpm) under IHHT (5 × 4 min hypoxia and hyperoxia), IHT (5 × 4 min hypoxia and normoxia), and NOR. Inspiratory fraction of oxygen during hypoxia and hyperoxia was set to 14% and 30%, respectively. Heart rate (HR), total hemoglobin (tHb) and muscle oxygen saturation (SmO2) of the right vastus lateralis muscle were continuously recorded during cycling. Participants' peripheral oxygen saturation (SpO2) and perceptual responses (i.e., perceived motor fatigue, effort perception, perceived physical strain, affective valence, arousal, motivation to exercise, and conflict to continue exercise) were surveyed prior, during (every 4 min), and after cycling. Prior to and after exercise, peripheral blood lactate concentration (BLC) was determined. Exercise enjoyment was ascertained after cycling. For statistical analysis, repeated measures analyses of variance were conducted.

Results

No differences in the acute perceptual responses were found between conditions (p ≥ 0.059, ηp 2 ≤ 0.18), while the physiological responses differed. Accordingly, SpO2 was higher during the hyperoxic periods during the IHHT compared to the normoxic periods during the IHT (p < 0.001, ηp 2 = 0.91). Moreover, HR (p = 0.005, ηp 2 = 0.33) and BLC (p = 0.033, ηp 2 = 0.28) were higher during IHT compared to NOR. No differences between conditions were found for changes in tHb (p = 0.684, ηp 2 = 0.03) and SmO2 (p = 0.093, ηp 2 = 0.16).

Conclusion

IHT was associated with a higher physiological response and metabolic stress, while IHHT did not lead to an increase in HR and BLC compared to NOR. In addition, compared to IHT, IHHT seems to improve reoxygenation indicated by a higher SpO2 during the hyperoxic periods. However, there were no differences in perceptual responses and ratings of exercise enjoyment between conditions. These results suggest that replacing normoxic by hyperoxic reoxygenation-periods during submaximal constant-load cycling under intermittent hypoxia reduced the exercise-related physiological stress but had no effect on perceptual responses and perceived exercise enjoyment in young recreational active healthy males.

Post-Exercise Hyperbaric Oxygenation Improves Recovery for Subsequent Performance

Background: The improvement of athletes' recovery seems crucial to maintaining a high-performance level. Since hyperbaric oxygenation (HBO) could be a valuable recovery method, this study aimed at determining the effects of post-exercise HBO at modest pressure (97% O₂; 1.3 ATA) on physiological response and subsequent cycling performance compared to passive recovery (PR; 21% O₂; 1 ATA). Methods: Twelve trained cyclists completed two testing sessions in a random crossover design. Both sessions consisted of one fatiguing exercise immediately followed by either HBO or PR recovery intervention (75 minutes), then a 5-minute maximal cycling effort. Cycling power output, heart rate variability (HRV) during recovery, blood lactate, and the rating of perceived exertion (RPE) were analyzed and compared between conditions. Results: Compared with PR, the cycling power output was significantly higher after HBO (307.5 ± 19.0 W vs 314.5 ± 19.3 W; p = .005; ES = 0.11 [-0.70-0.90]). Moreover, several HRV indices revealed an improvement in HRV recovery in HBO condition. Blood lactate was not significantly different between conditions, neither following the fatiguing exercise nor the maximal effort. HBO decreased RPE after maximal cycling effort and improved the perceived recovery the day after testing sessions (p < .001). Conclusion: This study suggests that HBO is an efficient strategy to improve cardiac parasympathetic reactivation and is beneficial for subsequent performance.

The Acute Effect of Hyperoxia on Onset of Blood Lactate Accumulation (OBLA) and Performance in Female Runners during the Maximal Treadmill Test

The objective of this study was to analyze the acute effect of hyperoxia during the maximal treadmill test (MTT) of runners. Participants included 10 female street runners who performed the MTT under two different conditions: hyperoxia (HYPX), inhaling oxygen (60% O₂) every 3 min; and normoxia (NORM), without additional oxygen inhalation. Both groups performed the MTT with increases in the slope of the run every 3 min until voluntary exhaustion. The variables of lactate concentration, the onset of blood lactate accumulation (OBLA), peripheral oxygen saturation (SpO₂), heart rate (HR), and Borg scale were evaluated. It was verified after the comparison (HYPX vs. NORM) that stage 3 (p = 0.012, Cohen’s d = 1.76) and stage 4 (p < 0.001; Cohen’s d = 5.69) showed a reduction in lactate under the HYPX condition. OBLA under the HYPX condition was identified at a later stage than NORM. There were no differences in Borg scale, SpO₂, and HR between the different conditions. It was concluded that the HYPX condition contributed to a reduction in lactate concentration and delayed OBLA in runners.

Can Hyperoxic Preconditioning in Normobaric Hypoxia (3500 m) Improve All-Out Exercise Performance in Highly Skilled Skiers? A Randomized Crossover Study

BACKGROUND

The altering effects of hypoxia on aerobic/anaerobic performance are well documented and form the basis of this study. Application of hyperoxic gases (inspiratory fraction of oxygen [FiO2] > 0.2095) prior to competition or training (hyperoxic preconditioning) can compensate for the negative influence of acute hypoxia.

PURPOSE

To investigate whether oxygen supplementation immediately prior to exercise (FiO2 = 1.0) improves all-out exercise performance in normobaric hypoxia (3500 m) in highly skilled skiers.

METHODS

In this single-blind, randomized, crossover study, 17 subjects performed a 60-second constant-load, all-out test in a normobaric hypoxic chamber. After a short period of adaptation to hypoxia (60 min), they received either pure oxygen or chamber air for 5 minutes prior to the all-out test (hyperoxic preconditioning vs nonhyperoxic preconditioning). Capillary blood was collected 3 times, and muscle oxygenation was assessed with near-infrared spectroscopy.

RESULTS

Absolute and relative peak power (P = .073 vs P = .103) as well as mean power (P = .330 vs P = .569) did not significantly differ after the hyperoxic preconditioning phase. PaO2 increased from 51.3 (3) to 451.9 (89.0) mm Hg, and SaO2 increased from 88.2% (1.7%) to 100% (0.2%) and dropped to 83.8% (4.2%) after the all-out test. Deoxygenation (P = .700) and reoxygenation rates (P = .185) did not significantly differ for both preconditioned settings.

CONCLUSIONS

Therefore, the authors conclude that hyperoxic preconditioning did not enhance 60-second all-out exercise performance in acute hypoxia (3500 m).

The effects of hyperoxia on repeated sprint cycling performance & muscle fatigue

OBJECTIVES

Hyperoxia (>21% oxygen) can evoke performance improvements in aerobic and anaerobic exercise. The aims of the current study were to determine the effects of breathing hyperoxic gas (fraction of inspired oxygen [F_iO₂] 1.00) on repeated cycle performance, and to assess the nature and extent of fatigue after intermittent sprinting.

DESIGN & METHODS

Testing (n=14 males) comprised two visits to the laboratory. Each session involved 10×15s repeated cycle sprints breathing FiO₂ 1.00 (hyperoxia) or FiO₂ 0.21 (normoxia). Muscle fatigue was measured pre and post sprints using Maximal Voluntary Contraction (MVC), voluntary activation (VA) and potentiated doublet twitch (PTF). Blood lactate (BLa) was taken between sprints. Paired samples t-tests were used to examine difference between conditions in power output (peak and mean Watts) and BLa. Two-way ANOVA was used to examine fatigue variables pre and post sprints according to condition.

RESULTS

Mean power output was 4% greater in hyperoxia (p<0.01), with no difference in peak power (p>0.05). There was a significant increase in BLa in hyperoxia compared with normoxia (p<0.01) in sprints 4 and 8, as well as meaningful difference in sprints 4-10. There was no significant difference in fatigue factors (MVC, VA and PTF) (p>0.05) in response to the cycling, although a large drop in PTF occurred in both conditions.

CONCLUSION

Hyperoxia can elicit improvements in mean cycling power, with no significant change in post exercise muscle fatigue. Hyperoxia as a training aid may provide performance enhancing effects during repeated sprint cycling by reducing concurrent muscle fatigue, primarily via peripheral factors.

Impact of Hyperoxic Preconditioning in Normobaric Hypoxia (3500 m) on Balance Ability in Highly Skilled Skiers: A Randomized, Crossover Study

It is well known that acute hypoxia has negative effects on balance performance. An attempt to compensate for the influence of hypoxia on competition performance was made by the application of hyperoxic gases (inspiratory fraction of oxygen > 0.2095) prior to exercise.

PURPOSE

To investigate whether hyperoxic preconditioning (pure-oxygen supplementation prior to exercise) improves balance ability and postural stability during normobaric hypoxia (3500 m) in highly skilled skiers.

METHODS

In this single-blind randomized, crossover study, 19 subjects performed a 60-s balance test (MFT S3-Check) in a normobaric hypoxic chamber. After a short period of adaptation to hypoxia (60 min), they received either pure oxygen or chamber air for 5 min prior to a balance test (hyperoxic preconditioning vs nonhyperoxic preconditioning). Capillary blood was collected 3 times.

RESULTS

Balance performance, indexed by sensory (P = .097), stability (P = .937), and symmetry (P = .202) scores, was not significantly different after the hyperoxic preconditioning phase. Balance performance decreased over time (no group difference). After hyperoxic preconditioning, arterial partial pressure of oxygen increased from 52.7 (4.5) mm Hg to 212.5 (75.8) mm Hg, and oxygen saturation of hemoglobin increased from 85.8% (3.5%) to 98.9% (0.7%) and remained significantly elevated to 90.1% (2.0%) after the balance test.

CONCLUSION

A hyperoxic preconditioning phase does not affect balance performance under hypoxic environmental conditions. A performance-enhancing effect, at least in terms of coordinative functions, was not supported by this study.

The Effects of Hyperoxia on Sea-Level Exercise Performance, Training, and Recovery: A Meta-Analysis

BACKGROUND

Acute exercise performance can be limited by arterial hypoxemia, such that hyperoxia may be an ergogenic aid by increasing tissue oxygen availability. Hyperoxia during a single bout of exercise performance has been examined using many test modalities, including time trials (TTs), time to exhaustion (TTE), graded exercise tests (GXTs), and dynamic muscle function tests. Hyperoxia has also been used as a long-term training stimulus or a recovery intervention between bouts of exercise. However, due to the methodological differences in fraction of inspired oxygen (F_iO₂), exercise type, training regime, or recovery protocols, a firm consensus on the effectiveness of hyperoxia as an ergogenic aid for exercise training or recovery remains unclear.

OBJECTIVES

The aims of this study were to (1) determine the efficacy of hyperoxia as an ergogenic aid for exercise performance, training stimulus, and recovery before subsequent exercise; and (2) determine if a dose-response exists between F_iO₂ and exercise performance improvements.

DATA SOURCE

The PubMed, Web of Science, and SPORTDiscus databases were searched for original published articles up to and including 8 September 2017, using appropriate first- and second-order search terms.

STUDY SELECTION

English-language, peer-reviewed, full-text manuscripts using human participants were reviewed using the process identified in the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement.

DATA EXTRACTION

Data for the following variables were obtained by at least two of the authors: F_iO₂, wash-in time for gas, exercise performance modality, heart rate, cardiac output, stroke volume, oxygen saturation, arterial and/or capillary lactate, hemoglobin concentration, hematocrit, arterial pH, arterial oxygen content, arterial partial pressure of oxygen and carbon dioxide, consumption of oxygen and carbon dioxide, minute ventilation, tidal volume, respiratory frequency, ratings of perceived exertion of breathing and exercise, and end-tidal oxygen and carbon dioxide partial pressures.

DATA GROUPING

Data were grouped into type of intervention (acute exercise, recovery, and training), and performance data were grouped into type of exercise (TTs, TTE, GXTs, dynamic muscle function), recovery, and training in hyperoxia.

DATA ANALYSIS

Hedges' g effect sizes and 95% confidence intervals were calculated. Separate Pearson's correlations were performed comparing the effect size of performance versus F_iO₂, along with the effect size of arterial content of oxygen, arterial partial pressure of oxygen, and oxygen saturation.

RESULTS

Fifty-one manuscripts were reviewed. The most common F_iO₂ for acute exercise was 1.00, with GXTs the most investigated exercise modality. Hyperoxia had a large effect improving TTE (g = 0.89), and small-to-moderate effects increasing TTs (g = 0.56), GXTs (g = 0.40), and dynamic muscle function performance (g = 0.28). An F_iO₂ ≥ 0.30 was sufficient to increase general exercise performance to a small effect or higher; a moderate positive correlation (r = 0.47-0.63) existed between performance improvement of TTs, TTE, and dynamic muscle function tests and F_iO₂, but not GXTs (r = 0.06). Exercise training and recovery supplemented with hyperoxia trended towards a large and small ergogenic effect, respectively, but the large variability and limited amount of research on these topics prevented a definitive conclusion.

CONCLUSION

Acute exercise performance is increased with hyperoxia. An F_iO₂ ≥ 0.30 appears to be beneficial for performance, with a higher F_iO₂ being correlated to greater performance improvement in TTs, TTE, and dynamic muscle function tests. Exercise training and recovery supplemented with hyperoxic gas appears to have a beneficial effect on subsequent exercise performance, but small sample size and wide disparity in experimental protocols preclude definitive conclusions.

The Impact of Hyperoxia on Human Performance and Recovery

Hyperoxia results from the inhalation of mixtures of gas containing higher partial pressures of oxygen (O₂) than normal air at sea level. Exercise in hyperoxia affects the cardiorespiratory, neural and hormonal systems, as well as energy metabolism in humans. In contrast to short-term exposure to hypoxia (i.e. a reduced partial pressure of oxygen), acute hyperoxia may enhance endurance and sprint interval performance by accelerating recovery processes. This narrative literature review, covering 89 studies published between 1975 and 2016, identifies the acute ergogenic effects and health concerns associated with hyperoxia during exercise; however, long-term adaptation to hyperoxia and exercise remain inconclusive. The complexity of the biological responses to hyperoxia, as well as the variations in (1) experimental designs (e.g. exercise intensity and modality, level of oxygen, number of participants), (2) muscles involved (arms and legs) and (3) training status of the participants may account for the discrepancies.

Hyperoxia Extends Time to Exhaustion During High-Intensity Intermittent Exercise: a Randomized, Crossover Study in Male Cyclists

BACKGROUND

Some endurance athletes exhibit exercise-induced arterial hypoxemia during high-intensity exercise. Inhalation of hyperoxic gas during exercise has been shown to counteract this exercise-associated reduction in hemoglobin oxygen saturation (S_aO₂), but the effects of hyperoxic gas inhalation on performance and S_aO₂ during high-intensity intermittent exercise remain unclear. This study investigated the effects of hyperoxic gas inhalation on performance and S_aO₂ during high-intensity intermittent cycling exercise.

METHODS

Eight male cyclists performed identical intermittent exercise tests (five sets of 3-min high-intensity cycling alternated with 3-min active recovery periods) under two different inspired air conditions, hyperoxia (HO; FIO₂ = 0.36) and normoxia (NO; FIO₂ = 0.21). The fifth set of each test was terminated at exhaustion, and the exercise time to exhaustion was recorded. Variables associated with arterial oxygen saturation (SpO₂) were measured using an ear pulse oximeter.

RESULTS

Time to exhaustion under HO conditions was significantly longer than under NO conditions (34.9 ± 4.6 vs. 30.0 ± 2.5 min, P = 0.004, ES = 1.32). SpO₂ was maintained under HO conditions but decreased under NO conditions.

CONCLUSIONS

Hyperoxic gas inhalation during the entire high-intensity intermittent exercise enhanced exercise performance in male cyclists.

Influence of Hypoxic Interval Training and Hyperoxic Recovery on Muscle Activation and Oxygenation in Connection with Double-Poling Exercise

Here, we evaluated the influence of breathing oxygen at different partial pressures during recovery from exercise on performance at sea-level and a simulated altitude of 1800 m, as reflected in activation of different upper body muscles, and oxygenation of the m. triceps brachii. Ten well-trained, male endurance athletes (25.3±4.1 yrs; 179.2±4.5 cm; 74.2±3.4 kg) performed four test trials, each involving three 3-min sessions on a double-poling ergometer with 3-min intervals of recovery. One trial was conducted entirely under normoxic (No) and another under hypoxic conditions (Ho; F_iO₂ = 0.165). In the third and fourth trials, the exercise was performed in normoxia and hypoxia, respectively, with hyperoxic recovery (HOX; F_iO₂ = 1.00) in both cases. Arterial hemoglobin saturation was higher under the two HOX conditions than without HOX (p<0.05). Integrated muscle electrical activity was not influenced by the oxygen content (best d = 0.51). Furthermore, the only difference in tissue saturation index measured via near-infrared spectroscopy observed was between the recovery periods during the NoNo and HoHOX interventions (P<0.05, d = 0.93). In the case of HoHo the athletes’ P_mean declined from the first to the third interval (P < 0.05), whereas P_mean was unaltered under the HoHOX, NoHOX and NoNo conditions. We conclude that the less pronounced decline in P_mean during 3 x 3-min double-poling sprints in normoxia and hypoxia with hyperoxic recovery is not related to changes in muscle activity or oxygenation. Moreover, we conclude that hyperoxia (F_iO₂ = 1.00) used in conjunction with hypoxic or normoxic work intervals may serve as an effective aid when inhaled during the subsequent recovery intervals.

Recovery effects of repeated exposures to normobaric hyperoxia on local muscle fatigue

Reported recovery effects of hyeroxia are conflicted. This study aimed to identify the effects and the mechanisms of normobaric hyperoxia on the recovery of local muscle fatigue, which is the most commonly encountered form of fatigue both daily and in training and competitions. Twelve male subjects performed 3 × 3 × no less than 30 seconds of isometric quadriceps exercise at 70% of maximum voluntary isometric contraction (MVIC) separated by two 15-minute recovery sessions under 1 of 2 different atmospheric oxygen concentrations, one in normoxia (NOX; 20.9% O2) and another in hyperoxia (HOX; 30.0% O2). To assess the degree of fatigue and recovery, 4 parameters were used; MVIC, endurance time to exhaustion, blood lactate, and perceived exertion measured by a visual analog scale (VAS). Maximum voluntary isometric contraction improved an average by approximately 14% in HOX compared with NOX at the conclusion of the second recovery session. However, this was not associated with changes in other parameters because changes in endurance time, blood lactate, and VAS during the trials were similar. Based on our findings, we conclude that 2 sets of 15-minute recovery session in normobaric hyperoxia are effective for restoring MVIC from local muscle fatigue induced by intermittent intense exercises. For quicker recovery, athletes are recommended to repeat 15-minute recovery process under 30.0% hyperoxia.

Does hyperoxic recovery during cross-country skiing team sprints enhance performance?

PURPOSE

This study aimed to determine the acute responses of breathing oxygen-enriched air during the recovery periods of a simulated 3 × 3-min cross-country skiing team sprint competition at simulated low altitude.

METHODS

Eight well-trained male endurance athletes performed two 3 × 3-min team sprint simulations on a double-poling ergometer at simulated altitude set at ∼ 1800 m. During the recovery periods between the 3 × 3-min sprints, all the athletes inhaled either hyperoxic (FiO2 = 1.00) or hypoxic (FiO2 ∼ 0.165) air in randomized and single-blind order. The mean total power output (P(mean tot)) and the mean power output of each sprint (P(mean) 1,2,3) were determined. Perceived exertion, capillary oxygen saturation of hemoglobin, partial pressure of oxygen, and blood lactate concentration were measured before and after all the sprints.

RESULTS

No differences in P(mean tot) were found between hyperoxic (198.4 ± 27.1 W) and hypoxic (200.2 ± 28.0 W) recovery (P = 0.57, effect size [d] = 0.07). P(mean) 1,2,3 (P > 0.90, d = 0.04-0.09) and RPE (P > 0.13, d = 0.02-0.63) did not differ between hyperoxic and hypoxic recovery. The partial pressure of oxygen (P < 0.01, d = 0.06-5.45) and oxygen saturation (P < 0.01, d = 0.15-5.40) during hyperoxic recovery were higher than those during hypoxic recovery. The blood lactate concentration was also lower directly after the third sprint (P = 0.03, d = 0.54) with hyperoxic recovery.

CONCLUSION

Results indicate that trained endurance athletes who inhale 100% oxygen during recovery periods in a cross-country skiing team sprint at low altitude do not exhibit enhanced performance despite the improvement in the key physiological variables of endurance performance.