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Weston ME, Armstrong N, Bond B, Tomlinson OW, Williams CA, Barker AR. The Influence of Acute Hypoxia on Oxygen Uptake and Muscle Oxygenation Kinetics During Cycling Exercise in Prepubertal Boys. Pediatr Exerc Sci 2024:1-8. [PMID: 38925533 DOI: 10.1123/pes.2023-0089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 04/30/2024] [Accepted: 05/05/2024] [Indexed: 06/28/2024]
Abstract
PURPOSE To examine the effect of normobaric hypoxia on pulmonary oxygen uptake (V˙O2) and muscle oxygenation kinetics during incremental and moderate-intensity exercise in children. METHODS Eight prepubertal boys (9-11 y) performed incremental cycle tests to exhaustion in both normoxia and hypoxia (fraction of inspired O2 of 15%) followed by repeat 6-minute transitions of moderate-intensity exercise in each condition over subsequent visits. RESULTS Maximal oxygen uptake (V˙O2max) was reduced in hypoxia compared with normoxia (1.69 [0.20] vs 1.87 [0.26] L·min-1, P = .028), although the gas exchange threshold was not altered in absolute terms (P = .33) or relative to V˙O2max (P = .78). During moderate-intensity exercise, the phase II V˙O2 time constant (τ) was increased in hypoxia (18 [9] vs 24 [8] s, P = .025), with deoxyhemoglobin τ unchanged (17 [8] vs 16 [6], P ≥ .28). CONCLUSIONS In prepubertal boys, hypoxia reduced V˙O2max and slowed V˙O2 phase II kinetics during moderate-intensity exercise, despite unchanged deoxyhemoglobin kinetics. These data suggest an oxygen delivery dependence of V˙O2max and moderate-intensity V˙O2 kinetics under conditions of reduced oxygen availability in prepubertal boys.
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Affiliation(s)
- Max E Weston
- Children's Health and Exercise Research Center, Public Health and Sports Sciences, Faculty of Health and Life Sciences, University of Exeter, Exeter,United Kingdom
- Department of Physiology, School of Medicine, Trinity College Dublin, Dublin,Ireland
| | - Neil Armstrong
- Children's Health and Exercise Research Center, Public Health and Sports Sciences, Faculty of Health and Life Sciences, University of Exeter, Exeter,United Kingdom
| | - Bert Bond
- Children's Health and Exercise Research Center, Public Health and Sports Sciences, Faculty of Health and Life Sciences, University of Exeter, Exeter,United Kingdom
| | - Owen W Tomlinson
- Children's Health and Exercise Research Center, Public Health and Sports Sciences, Faculty of Health and Life Sciences, University of Exeter, Exeter,United Kingdom
| | - Craig A Williams
- Children's Health and Exercise Research Center, Public Health and Sports Sciences, Faculty of Health and Life Sciences, University of Exeter, Exeter,United Kingdom
| | - Alan R Barker
- Children's Health and Exercise Research Center, Public Health and Sports Sciences, Faculty of Health and Life Sciences, University of Exeter, Exeter,United Kingdom
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Geng Z, Wang J, Cao G, Tan C, Li L, Qiu J. Differential impact of heat and hypoxia on dynamic oxygen uptake and deoxyhemoglobin parameters during incremental exhaustive exercise. Front Physiol 2024; 14:1247659. [PMID: 38260100 PMCID: PMC10801013 DOI: 10.3389/fphys.2023.1247659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 12/13/2023] [Indexed: 01/24/2024] Open
Abstract
Purpose: This study aims to explore the relationship between the dynamic changes in oxygen uptake (V ˙ O 2 ) and deoxyhemoglobin (HHb) and peripheral fatigue in athletes during incremental exhaustive exercise under different environmental conditions, including high temperature and humidity environment, hypoxic environment, and normal conditions. Methods: 12 male modern pentathlon athletes were recruited and performed incremental exhaustive exercise in three different environments: normal condition (23°C, 45%RH, FiO2 = 21.0%, CON), high temperature and humidity environment (35°C, 70%RH, FiO2 = 21.0%, HOT), and hypoxic environment (23°C, 45%RH, FiO2 = 15.6%, HYP). Gas metabolism data of the athletes were collected, and muscle oxygen saturation (SmO2) and total hemoglobin content in the vastus lateralis muscles (VL) were measured to calculate the deoxyhemoglobin content. Linear and nonlinear function models were used to fit the characteristic parameters of V ˙ O 2 and HHb changes. Results: The results showed that compared to the CON, V ˙ O 2 , V ˙ CO 2 , and exercise time were decreased in the HOT and HYP (p < 0.05). Δ E V ˙ O 2 and OUES were reduced in the HOT and HYP compared to the CON (p < 0.05). The Gas exchange threshold in the CON corresponded to higher V ˙ O 2 than in the HYP and HOT (p < 0.05). Δ E V ˙ O 2 - 1 was reduced in the HOT compared to the HYP (p < 0.05). ΔEHHb was higher in the HOT compared to the CON (p < 0.05). ΔEHHb-1 was increased in the HYP compared to the CON (p < 0.05). There was a negative correlation between ΔEHHb and corresponding V ˙ O 2 max in the HOT (r = -0.655, p < 0.05), and a negative correlation between ΔEHHb-1 and corresponding V ˙ O 2 max in the HYP (r = -0.606, p < 0.05). Conclusion: Incremental exhaustive exercise in hypoxic environment and high temperature and humidity environments inhibits gas exchange and oxygen supply to skeletal muscle tissue in athletes. For athletes, the accelerated deoxygenation response of skeletal muscles during incremental exhaustive exercise in high temperature and humidity environments, as well as the excessive deoxygenation response before BP of deoxyhemoglobin in hypoxic environment, may be contributing factors to peripheral fatigue under different environmental conditions.
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Affiliation(s)
- Zhizhong Geng
- School of Sports and Health, Shanghai University of Sport, Shanghai, China
| | - Jinhao Wang
- Shanghai Research Institute of Sports Science, Shanghai, China
| | - Guohuan Cao
- Shanghai Research Institute of Sports Science, Shanghai, China
| | - Chenhao Tan
- Shanghai Research Institute of Sports Science, Shanghai, China
| | - Longji Li
- School of Sports and Health, Shanghai University of Sport, Shanghai, China
| | - Jun Qiu
- Shanghai Research Institute of Sports Science, Shanghai, China
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Chopra K, Jeffries O, Tallent J, Heffernan S, Kilduff L, Gray A, Waldron M. Repeated Ischemic Preconditioning Effects on Physiological Responses to Hypoxic Exercise. Aerosp Med Hum Perform 2022; 93:13-21. [PMID: 35063051 DOI: 10.3357/amhp.5919.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
INTRODUCTION: Repeated ischemic preconditioning (IPC) can improve muscle and pulmonary oxygen on-kinetics, blood flow, and exercise efficiency, but these effects have not been investigated in severe hypoxia. The aim of the current study was to evaluate the effects of 7 d of IPC on resting and exercising muscle and cardio-pulmonary responses to severe hypoxia.METHODS: A total of 14 subjects received either: 1) 7 d of repeated lower-limb occlusion (4 × 5 min, 217 ± 30 mmHg) at limb occlusive pressure (IPC) or SHAM (4 × 5 min, 20 mmHg). Subjects were tested for resting limb blood flow, relative microvascular deoxyhemoglobin concentration ([HHB]), and pulmonary oxygen (Vo2p) responses to steady state and incremental exercise to exhaustion in hypoxia (fractional inspired O₂ = 0.103), which was followed by 7 d of IPC or SHAM and retesting 72 h post-intervention.RESULTS: There were no effects of IPC on maximal oxygen consumption, time to exhaustion during the incremental test, or minute ventilation and arterial oxygen saturation. However, the IPC group had higher delta efficiency based on pooled results and lower steady state Δ[HHB] (IPC ∼24% vs. SHAM ∼6% pre to post), as well as slowing the [HHB] time constant (IPC ∼26% vs. SHAM ∼3% pre to post) and reducing the overshoot in [HHB]: Vo₂ ratio during exercise onset.CONCLUSIONS: Collectively, these results demonstrate that muscle O₂ efficiency and microvascular O₂ distribution can be improved by repeated IPC, but there are no effects on maximal exercise capacity in severe hypoxia.Chopra K, Jeffries O, Tallent J, Heffernan S, Kilduff L, Gray A, Waldron M. Repeated ischemic preconditioning effects on physiological responses to hypoxic exercise. Aerosp Med Hum Perform. 2022; 93(1):13-21.
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Rizzoto G, Hall C, Tyberg JV, Thundathil JC, Caulkett NA, Kastelic JP. Increased testicular blood flow maintains oxygen delivery and avoids testicular hypoxia in response to reduced oxygen content in inspired air. Sci Rep 2018; 8:10905. [PMID: 30026599 PMCID: PMC6053420 DOI: 10.1038/s41598-018-29248-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 07/09/2018] [Indexed: 11/09/2022] Open
Abstract
Despite a long-standing assertion that mammalian testes operate near hypoxia and increased testicular temperature causes frank hypoxia, we have preliminary evidence that changes are due to hyperthermia per se. The objective was to determine how variations in inspired oxygen concentration affected testicular blood flow, oxygen delivery and extraction, testicular temperature and lactate production. Eight rams were maintained under general anesthesia, with successive decreases in oxygen concentration in inspired air (100, 21 and 13%, respectively). As oxygen concentration decreased from 100 to 13%, there were increases in testicular blood flow (9.6 ± 1.7 vs 12.9 ± 1.9 ml/min/100 g of testis, P < 0.05; mean ± SEM) and conductance (normalized flow; 0.46 ± 0.07 to 1.28 ± 0.19 ml/min/mm Hg/100 g testis (P < 0.05). Increased testicular blood flow maintained oxygen delivery and increased testicular temperature by ~1 °C; this increase was correlated to increased testicular blood flow (r = 0.35, P < 0.0001). Furthermore, oxygen utilization increased concomitantly and there were no significant differences among oxygen concentrations in blood pH, HCO3− or base excess, and no effects of venous-arterial differences in lactate production. In conclusion, under acute hypoxic conditions, testes maintained oxygen delivery and uptake by increasing blood flow and oxygen extraction, with no evidence of anaerobic metabolism. However, additional studies are needed to determine longer-term responses and potential evidence of anaerobic metabolism at the molecular level.
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Affiliation(s)
- G Rizzoto
- Faculty of Veterinary Medicine, Department of Production Animal Health, University of Calgary, Calgary, AB, Canada
| | - C Hall
- Departments of Cardiac Sciences and Physiology/Pharmacology, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada
| | - J V Tyberg
- Departments of Cardiac Sciences and Physiology/Pharmacology, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada
| | - J C Thundathil
- Faculty of Veterinary Medicine, Department of Production Animal Health, University of Calgary, Calgary, AB, Canada
| | - N A Caulkett
- Faculty of Veterinary Medicine, Department of Veterinary Clinical and Diagnostic Sciences, University of Calgary, Calgary, AB, Canada
| | - J P Kastelic
- Faculty of Veterinary Medicine, Department of Production Animal Health, University of Calgary, Calgary, AB, Canada.
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Colosio AL, Pogliaghi S. Quantification of energy expenditure of military loaded runs: what is the performance of laboratory-based equations when applied to the field environment? J ROY ARMY MED CORPS 2018; 164:253-258. [DOI: 10.1136/jramc-2017-000887] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 02/15/2018] [Accepted: 02/16/2018] [Indexed: 11/04/2022]
Abstract
IntroductionPerformance during army loaded runs provides a synthetic indicator of a soldier’s capacity to move while carrying loads and thereby remain able to execute a mission. The aim of this study was to estimate and compare the energy expenditure (EE) of army loaded runs, conducted in a field environment using laboratory-based equations and HR index (HRindex).Methods45 Ranger recruits had HR monitored during three loaded runs (10, 15 and 20 km) in full military equipment in the field environment. EE was calculated using reference equations (EE-Eq) and estimates of oxygen consumption based on HRindex (EE-HRindex). Correspondence between EE-Eq and EE-HRindex estimates was evaluated using a two-way analysis of variance, correlation test and Bland-Altman analysis.ResultsEE-Eq relative to time and weight was significantly higher for the 10 km (0.175±0.016) compared with 15 and 20 km (0.163±0.016 and 0.160±0.013 kcal/kg/min, not different). The overall EE-Eq increased significantly with distance (1129±59, 1703±80 and 2250±115 kcal for 10, 15 and 20 km). EE-Eq was not different from and highly correlated with EE-HRindex, with a small and non-significant bias and good precision between methods.ConclusionsOur study provides the first comprehensive data on HR and EE during long-distance loaded army runs, in full combat equipment, in actual field conditions. Equation-based estimates of EE during these heavy-intensity activities were not significantly different from and highly correlated with HR-based estimates. This corroborates the general applicability of the predictive equations in the field environment. Furthermore, our study suggests that time-resolved HR-based estimates of EE during army runs can be used to evaluate for the effects of context specificity, individual variability and fatigue in movement economy.
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