The effect of inspired oxygen fraction on peak oxygen uptake during arm exercise

Comparison of Mitochondrial Respiration in M. triceps brachii and M. vastus lateralis Between Elite Cross-Country Skiers and Physically Active Controls

Rationale

The main purposes of this study were to compare mitochondrial respiration in M. triceps brachii and M. vastus lateralis between elite cross-country (XC) skiers and physically active controls (CON), and to explore the associations between mitochondrial respiration in these muscles and peak oxygen uptake ( V ˙ O_2peak) in arm- and leg-dominant exercise modes.

Methods

Thirteen male elite XC skiers (age: 25 ± 4; peak oxygen uptake ( V ˙ O_2peak): 75.5 ± 4.2 mL⋅kg^-1⋅min^-1) and twelve CON (age: 26 ± 3; V ˙ O_2peak: 57.2 ± 6.4 mL⋅kg^-1⋅min^-1) had microbiopsies taken from M. vastus lateralis and M. triceps brachii, which were analyzed for various measures of mitochondrial respiration using high-resolution respirometry. Thereafter, all participants tested V ˙ O_2peak in both running (RUN) and upper body poling (UBP).

Results

XC skiers had generally higher mitochondrial respiration in M. triceps brachii compared to CON (P < 0.001), whereas no significant group-differences in mitochondrial respiration in M. vastus lateralis were revealed. XC skiers had higher mitochondrial respiration in M. triceps brachii compared to M. vastus lateralis (P = 0.005-0.058), whereas in CON, most mitochondrial respiration measures were higher in M. vastus lateralis than in M. triceps brachii (P < 0.01). When all athletes were pooled, there was a strong positive correlation between V ˙ O_2peak in UBP and mitochondrial respiration in M. triceps brachii on several measures (P < 0.01), whereas no correlation was found for RUN.

Conclusion

The higher mitochondrial respiration found in M. triceps brachii compared to M. vastus lateralis among our elite XC skiers demonstrates the potential for the arm muscles to adapt to aerobic endurance training. The opposite pattern found in CON, clearly showed lower mitochondrial respiration in M. triceps brachii compared to XC skiers, whereas respiration in M. vastus lateralis did not differ between groups. The strong positive correlation between mitochondrial respiration in M. triceps brachii and V ˙ O_2peak in UBP indicate that arm muscles' respiratory function may be a limiting factor for V ˙ O_2peak in arm-dominant exercise modes.

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.

Physiological mechanism underlying the improvement in visuospatial performance due to 30% oxygen inhalation

This study investigated the effect of 30% oxygen inhalation on visuospatial cognitive performance, blood oxygen saturation, and heart rate. Six male (25.8(mean)+/-1.0(SD) years) and six female (23.8+/-1.9 years) college students participated in this experiment. Two psychological tests were developed to measure the performance level of visuospatial cognition. The experiment consisted of two runs: one was a visuospatial cognition task under normal air (21% oxygen) condition and the other under hyperoxic air (30% oxygen) condition. The experimental sequence in each run consisted of four phases, that were Rest1 (1min), Control (1min), Task (4min), and Rest2 (4min). Blood oxygen saturation and heart rate were measured throughout the course of four phases. The analysis of behavioral performance with 30% oxygen administration when compared to 21% oxygen revealed that the mean performance was improved. When supplied 30% oxygen in the air, the blood oxygen saturation was increased while the heart rate was decreased compared to those under 21% oxygen condition. We conclude that 30% oxygen inhalation enhanced visuospatial performance by the increased the oxygen saturation in the blood.

Why do arms extract less oxygen than legs during exercise?

To determine whether conditions for O2 utilization and O2 off-loading from the hemoglobin are different in exercising arms and legs, six cross-country skiers participated in this study. Femoral and subclavian vein blood flow and gases were determined during skiing on a treadmill at approximately 76% maximal O2 uptake (V(O2)max) and at V(O2)max with different techniques: diagonal stride (combined arm and leg exercise), double poling (predominantly arm exercise), and leg skiing (predominantly leg exercise). The percentage of O2 extraction was always higher for the legs than for the arms. At maximal exercise (diagonal stride), the corresponding mean values were 93 and 85% (n = 3; P < 0.05). During exercise, mean arm O2 extraction correlated with the P(O2) value that causes hemoglobin to be 50% saturated (P50: r = 0.93, P < 0.05), but for a given value of P50, O2 extraction was always higher in the legs than in the arms. Mean capillary muscle O2 conductance of the arm during double poling was 14.5 (SD 2.6) ml.min(-1).mmHg(-1), and mean capillary P(O2) was 47.7 (SD 2.6) mmHg. Corresponding values for the legs during maximal exercise were 48.3 (SD 13.0) ml.min(-1).mmHg(-1) and 33.8 (SD 2.6) mmHg, respectively. Because conditions for O2 off-loading from the hemoglobin are similar in leg and arm muscles, the observed differences in maximal arm and leg O2 extraction should be attributed to other factors, such as a higher heterogeneity in blood flow distribution, shorter mean transit time, smaller diffusing area, and larger diffusing distance, in arms than in legs.

The effect of varied fractional inspired oxygen on arm exercise performance in spinal cord injury and able-bodied persons

OBJECTIVE

To examine the effect of different levels of fractional inspired oxygen (FiO(2)) (15%, 21%, 50%) on peak oxygen consumption (VO(2)peak) during arm exercise in persons with spinal cord injury and in able-bodied controls.

DESIGN

Case-control study.

SETTING

University medical center in the Netherlands.

PARTICIPANTS

Ten able-bodied controls, 6 persons with paraplegia, and 6 persons with tetraplegia.

INTERVENTIONS

Inspiration of 15%, 21%, and 50% oxygen during a 15-minute period before and during arm exercise.

MAIN OUTCOME MEASURES

Oxygen uptake (VO(2)peak, VO(2)peak/kg), power output, ventilation, and base excess.

RESULTS

In the able-bodied controls, significant FiO(2) dependency was seen in power output, VO(2)peak, and VO(2)peak/kg. Persons with paraplegia showed significant FiO(2) dependency in VO(2) and VO(2)/kg. In persons with tetraplegia, no FiO(2) dependency was observed; however, VO(2) and VO(2)/kg were significantly higher at 50% than at 15% FiO(2). Ventilation and base excess did not change in able-bodied controls or in persons with paraplegia with different levels of FiO(2). In persons with tetraplegia, ventilation was significantly higher at 15% than at 50% FiO(2), and base excess did not change. No significant interactions between groups and FiO(2) were observed.

CONCLUSIONS

Oxygen consumption during peak arm-cranking exercise is enhanced with an increased inspiratory oxygen fraction in able-bodied controls as well as in persons with paraplegia and to a lesser extent in persons with tetraplegia, indicating that peak oxygen consumption during arm exercise is limited by oxygen supply rather than by the small muscle mass and related biochemical limitations.