Arterial haemoglobin oxygen saturation is affected by F1O2 at submaximal running velocities in elite athletes
ABSTRACT 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.
SourceAvailable from: Laurie Rauch[Show abstract] [Hide abstract]
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.Arbeitsphysiologie 12/2007; 101(6):771-781. DOI:10.1007/s00421-007-0458-z · 2.30 Impact Factor
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ABSTRACT: The regulation of the pacing strategy remains poorly understood, because much of classic physiology has focused on the factors that ultimately limit, rather than regulate, exercise performance. When exercise is self-paced and work rate is free to vary in response to external and internal physiological cues, then a complex system is proposed to be responsible for alterations in exercise intensity, possibly through altered activation of skeletal muscle motor units. The present review evaluates the evidence for such a complex system by investigating studies in which interventions such as elevated temperature, altered oxygen content of the air, reduced fuel availability and misinformation about distance covered have resulted in alterations to the pacing strategy. The review further investigates how such a pacing strategy might be regulated for optimal performance, while ensuring that irreversible physiological damage is not incurred.British journal of sports medicine 03/2009; 43(6):e1. DOI:10.1136/bjsm.2009.057562 · 4.17 Impact Factor
Article: Current trends in altitude training.[Show abstract] [Hide abstract]
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 high-intensity workouts at moderate altitude (1860m/6100ft) and endurance perfor- mance 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 4575 m/15006 ft and 4270 m/14005 ft, 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.Sports Medicine 02/2001; 31(4):249-65. DOI:10.2165/00007256-200131040-00002 · 5.32 Impact Factor