ORCID Profile
0000-0002-8271-8969
Current Organisation
Ara Institute of Canterbury
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Publisher: Springer Science and Business Media LLC
Date: 18-06-2018
DOI: 10.1007/S00421-007-0616-3
Abstract: In a placebo-controlled study, the effects of intermittent hypoxic exposures (IHE) or a placebo control for 10 days, were examined on the extent of exercise-induced hypoxemia (EIH), cerebral and muscle oxygenation (near-infrared spectroscopy) and VO(2peak). Eight athletes who had previously displayed EIH (fall in saturation of arterial oxygen (SaO(2)) of >4% from rest) during an incremental maximal exercise test, volunteered for the present research. Prior to (baseline), and 2 days following (post) the IHE or placebo, an incremental maximal exercise test was performed whilst SaO(2), heart rate, cerebral and muscle oxygenation and respiratory gas exchange were measured continuously. After IHE, but not placebo, EIH was less pronounced at VO(2peak) (IHE group, SaO(2) at VO(2peak) baseline 91.23 +/- 1.10%, post 94.10 +/- 2.19% P < 0.01, mean +/- SD). This reduction was reflected in an increased ventilation (NS), a lower end-tidal CO(2) (P < 0.01), and lowered cerebral TOI during heavy exercise (90% VO(2peak): -6.1 +/- 6.0 Delta%, P = 0.04). Conversely, muscle tHb at maximal exercise, was increased (2.4 +/- 1.8 DeltamicroM, P = 0.01, mean +/- 95 CL) following IHE, whilst de-oxygenated Hb at 90% of VO(2peak) was reduced (-0.9 +/- 0.8 DeltamicroM, P = 0.02). These data indicate that exposure to IHE can attenuate the degree of EIH. Despite a potential compromise in cerebral oxygenation, exposure to IHE may induce some positive physiological adaptations at the muscle tissue level. We speculate that the unchanged VO(2peak) following IHE might reflect a balance between these central (cerebral) and peripheral (muscle) adaptations.
Publisher: Canadian Science Publishing
Date: 06-2010
DOI: 10.1139/H10-044
Abstract: The effects of intermittent hypoxic exposure (IHE) on cerebral and muscle oxygenation, arterial oxygen saturation (SaO 2 ), and respiratory gas exchange during a 20-km cycle time trial (20TT) were examined (n = 9) in a placebo-controlled randomized design. IHE (7:3 min hypoxia to normoxia) involved 90-min sessions for 10 days, with SaO 2 cl ed at ∼80%. Prior to, and 2 days after the intervention, a 20TT was performed. During the final minute of the 20TT, in the IHE group only, muscle oxyhemoglobin (oxy-Hb) was elevated (mean ± 95% confidence interval 1.3 ± 1.2 ΔµM, p = 0.04), whereas cerebral oxy-Hb was reduced (–1.9% ± 1.0%, p 0.01) post intervention compared with baseline. The 20TT performance was unchanged between groups (p = 0.7). In the IHE group, SaO 2 was higher (1.0 ± 0.7Δ%, p = 0.006) and end-tidal PCO 2 was lower (–1.2 ± 0.1 mm Hg, p = 0.01) during the final stage of the 20TT post intervention compared with baseline. In summary, reductions in muscle oxy-Hb and systemic SaO 2 occurring at exercise intensities close to maximal at the end of a 20TT were offset by IHE, although this was not translated into improved performance.
Publisher: Wiley
Date: 13-07-2010
DOI: 10.1111/J.1600-0838.2009.00946.X
Abstract: This study aimed to verify whether the "live low, train high" approach is beneficial for endurance and/or anaerobic cycling performance. Sixteen well-trained athletes completed 90 min of endurance training (60-70% of heart rate reserve), followed by two 30-s all-out sprints (Wingate test), daily, for 10 consecutive days. Nine subjects [intermittent hypoxic training (IHT) group] trained with an F(I)O(2) set to produce arterial oxygen saturations of approximately 88-82%, while seven subjects (placebo group) trained while breathing a normal gas mixture (F(I)O(2)=0.21). Four performance tests were conducted at sea level including a familiarization and baseline trial, followed by repeat trials at 2 and 9 days post-intervention. Relative to the placebo group, the mean power during the 30-s Wingate test increased by 3.0% (95% confidence limits, CL +/- 3.5%) 2 days, and 1.7% (+/- 3.8%) 9 days post-IHT. Changes in other performance variables (30 s peak power, 20 km mean power and 20 km oxygen cost) were unclear. During the time trial, the IHT participants' blood lactate concentration, respiratory exchange ratio, and SpO(2), relative to the placebo group, was substantially increased at 2 days post-intervention. The addition of IHT to the normal training program of well-trained athletes produced worthwhile gains in 30 s sprint performance possibly through enhanced glycolysis.
Publisher: Public Library of Science (PLoS)
Date: 18-03-2014
Publisher: Frontiers Media SA
Date: 07-02-2017
No related grants have been discovered for Helen Marshall.