Arterial haemoglobin oxygen saturation is affected by F(I)O2 at submaximal running velocities in elite athletes
This study was conducted to determine whether arterial desaturation would occur at submaximal workloads in highly trained endurance athletes and whether saturation is affected by the fraction of oxygen in inspired air (F1O2). Six highly trained endurance athletes (5 women and 1 man, aged 25 ± 4 yr, VO2max 71.3 ± 5.0 ml · kg−1· min−1) ran 4 × 4 min on a treadmill in normoxia (F1O2 0.209), hypoxia (F1O2 0.155) and hyperoxia (F1O2 0.293) in a randomized order. The running velocities corresponded to 50, 60, 70 and 80% of their normoxic maximal oxygen uptake (VO2max). In hypoxia, the arterial haemoglobin oxygen saturation percentage (SpO2%) was significantly lower than in hyperoxia and normoxia throughout the test, and the difference became more evident with increasing running intensity. In hyperoxia, the Sp2% was significantly higher than in normoxia at 70% running intensity as well as during recovery. The lowest values of SpO2% were 94.0±3.8% (P<0.05, compared with rest) in hyperoxia, 91.0±3.6% (P<0.001) in normoxia and 72.8 ± 10.2% (P<0.001) in hypoxia. Although the SpO2% varied with the F1O2, the VO2 was very similar between the trials, but the blood lactate concentration was elevated in hypoxia and decreased in hyperoxia at the 70% and 80% workloads. In conclusion, elite endurance athletes may show an F1O2-dependent limitation for arterial O2 saturation even at submaximal running intensities. In hyperoxia and normoxia, the desaturation is partly transient, but in hypoxia the desaturation worsens parallel with the increase in exercise intensity.
Available from: Aurélien Pichon
- "It is therefore possible, as recently suggested (Woorons et al., 2007), that a training with VH may actually enhance the lactate concentration in the working muscles and finally help to maintain the power of glycolytic metabolism. Furthermore, it has already been shown that performing exercises with similar intensities and Sp O 2 can induce higher [La] than exercises with normal Sp O 2 (Peltonen et al., 1999). Nevertheless, a placebo effect cannot be ruled out. "
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ABSTRACT: This study investigated the effects of training with voluntary hypoventilation (VH) at low pulmonary volumes. Two groups of moderately trained runners, one using hypoventilation (HYPO, n=7) and one control group (CONT, n=8), were constituted. The training consisted in performing 12 sessions of 55 min within 4 weeks. In each session, HYPO ran 24 min at 70% of maximal O(2) consumption ( [V(02max)) with a breath holding at functional residual capacity whereas CONT breathed normally. A V(02max) and a time to exhaustion test (TE) were performed before (PRE) and after (POST) the training period. There was no change in V(O2max), lactate threshold or TE in both groups at POST vs. PRE. At maximal exercise, blood lactate concentration was lower in CONT after the training period and remained unchanged in HYPO. At 90% of maximal heart rate, in HYPO only, both pH (7.36+/-0.04 vs. 7.33+/-0.06; p<0.05) and bicarbonate concentration (20.4+/-2.9 mmolL(-1) vs. 19.4+/-3.5; p<0.05) were higher at POST vs. PRE. The results of this study demonstrate that VH training did not improve endurance performance but could modify the glycolytic metabolism. The reduced exercise-induced blood acidosis in HYPO could be due to an improvement in muscle buffer capacity. This phenomenon may have a significant positive impact on anaerobic performance.
Available from: Laurie Rauch
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ABSTRACT: Increasing inspiratory oxygen tension improves exercise performance. We tested the hypothesis that this is partly due to changes
in muscle activation levels while perception of exertion remains unaltered. Eleven male subjects performed two 20-km cycling
time-trials, one in hyperoxia (HI, FiO2 40%) and one in normoxia (NORM, FiO2 21%). Every 2km we measured power output, heart rate, blood lactate, integrated vastus lateralis EMG activity (iEMG) and
ratings of perceived exertion (RPE). Performance was improved on average by 5% in HI compared to NORM (P<0.01). Changes in heart rate, plasma lactate concentration and RPE during the trials were similar. For the majority of
the time-trials, power output was maintained in HI, but decreased progressively in NORM (P<0.01) while it increased in both trials for the last kilometre (P<0.0001). iEMG was proportional to power output and was significantly greater in HI than in NORM. iEMG activity increased
significantly in the final kilometer of both trials (P<0.001). This suggests that improved exercise performance in hyperoxia may be the result of increased muscle activation
leading to greater power outputs. The finding of identical RPE, lactate and heart rate in both trials suggests that pacing
strategies are altered to keep the actual and perceived exercise stress at a similar level between conditions. We suggest
that a complex, intelligent system regulates exercise performance through the control of muscle activation levels in an integrative
manner under conditions of normoxia and hyperoxia.
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ABSTRACT: Recently, endurance athletes have used several novel approaches and modalities for altitude training including: (i) normobaric hypoxia via nitrogen dilution (hypoxic apartment); (ii) supplemental oxygen; (iii) hypoxic sleeping devices; and (iv) intermittent hypoxic exposure (IHE).
A normobaric hypoxic apartment simulates an altitude environment equivalent to approximately 2000 to 3000m (6560 to 9840ft). Athletes who use a hypoxic apartment typically ‘live and sleep high’ in the hypoxic apartment for 8 to 18 hours a day, but complete their training at sea level, or approximate sea level conditions. Several studies suggest that using a hypoxic apartment in this manner produces beneficial changes in serum erythropoietin (EPO) levels, reticulocyte count and red blood cell (RBC) mass, which in turn may lead to improvements in postaltitude endurance performance. However, other studies failed to demonstrate significant changes in haematological indices as a result of using a hypoxic apartment. These discrepancies may be caused by differences in methodology, the hypoxic stimulus that athletes were exposed to and/or the training status of the athletes.
Supplemental oxygen is used to simulate either normoxic (sea level) or hyperoxic conditions during high-intensity workouts at altitude. This method is a modification of the ‘high-low’ strategy, since athletes live in a natural terrestrial altitude environment but train at ‘sea level’ with the aid of supplemental oxygen. Limited data regarding the efficacy of hyperoxic training suggests that highintensity workouts at moderate altitude (1860m/6100ft) and endurance performance at sea level may be enhanced when supplemental oxygen training is utilised at altitude over a duration of several weeks.
Hypoxic sleeping devices include the Colorado Altitude Training (CAT) Hatch™ (hypobaric chamber) and Hypoxico Tent System™ (normobaric hypoxic system), both of which are designed to allow athletes to sleep high and train low. These devices simulate altitudes up to approximately 4575m/15006ft and 4270m/14005ft, respectively. Currently, no studies have been published on the efficacy of these devices on RBC production, maximal oxygen uptake and/or performance in elite athletes.
IHE is based on the assumption that brief exposures to hypoxia (1.5 to 2.0 hours) are sufficient to stimulate the release of EPO, and ultimately bring about an increase in RBC concentration. Athletes typically use IHE while at rest, or in conjunction with a training session. Data regarding the effect of IHE on haematological indices and athletic performance are minimal and inconclusive.
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