Ischemic preconditioning does not improve peak exercise capacity at sea level or simulated high altitude in trained male cyclists

2015 ◽  
Vol 40 (1) ◽  
pp. 65-71 ◽  
Author(s):  
Elizabeth A. Hittinger ◽  
Jennifer L. Maher ◽  
Mark S. Nash ◽  
Arlette C. Perry ◽  
Joseph F. Signorile ◽  
...  
Keyword(s):  
Blood Flow ◽  
High Altitude ◽  
Sea Level ◽  
Exercise Capacity ◽  
Ischemic Preconditioning ◽  
Oxygen Delivery ◽  
Peak Exercise ◽  
Arterial Hypoxemia ◽  
Cardiovascular Hemodynamics ◽  
Simulated High Altitude

Ischemic preconditioning (IPC) may improve blood flow and oxygen delivery to tissues, including skeletal muscle, and has the potential to improve intense aerobic exercise performance, especially that which results in arterial hypoxemia. The aim of the study was to determine the effects of IPC of the legs on peak exercise capacity (Wpeak), submaximal and peak cardiovascular hemodynamics, and peripheral capillary oxygen saturation (SpO2) in trained males at sea level (SL) and simulated high altitude (HA; 13.3% FIO2, ∼3650 m). Fifteen highly trained male cyclists and triathletes completed 2 Wpeak tests (SL and HA) and 4 experimental exercise trials (10 min at 55% altitude-specific Wpeak then increasing by 30 W every 2 min until exhaustion) with and without IPC. HA resulted in significant arterial hypoxemia during exercise compared with SL (73% ± 6% vs. 93% ± 4% SpO2, p < 0.001) that was associated with 21% lower Wpeak values. IPC did not significantly improve Wpeak at SL or HA. Additionally, IPC failed to improve cardiovascular hemodynamics or SpO2 during submaximal exercise or at Wpeak. In conclusion, IPC performed 45 min prior to exercise does not improve Wpeak or systemic oxygen delivery during submaximal or peak exercise at SL or HA. Future studies must examine the influence of IPC on local factors, such as working limb blood flow, oxygen delivery, and arteriovenous oxygen difference as well as whether the effectiveness of IPC is altered by the volume of muscle made ischemic, the timing prior to exercise, and high altitude acclimatization.

Ischemic Preconditioning Does Not Improve Peak Exercise Capacity at Sea Level or Simulated High Altitude

2015 ◽  
Vol 47 ◽  
pp. 828
Author(s):  
Kevin A. Jacobs ◽  
Elizabeth A. Hittinger ◽  
Jennifer L. Maher ◽  
Mark S. Nash ◽  
Arlette C. Perry ◽  
...  
Keyword(s):  
High Altitude ◽  
Sea Level ◽  
Exercise Capacity ◽  
Ischemic Preconditioning ◽  
Peak Exercise ◽  
Simulated High Altitude

scholarly journals Global REACH 2018: renal oxygen delivery is maintained during early acclimatization to 4,330 m

2020 ◽  
Vol 319 (6) ◽  
pp. F1081-F1089
Author(s):  
Andrew R. Steele ◽  
Michael M. Tymko ◽  
Victoria L. Meah ◽  
Lydia L. Simpson ◽  
Christopher Gasho ◽  
...  
Keyword(s):  
Blood Flow ◽  
Renal Function ◽  
High Altitude ◽  
Renal Blood Flow ◽  
Sea Level ◽  
Oxygen Delivery ◽  
Acid Base ◽  
Altitude Acclimatization ◽  
High Altitude Acclimatization ◽  
Renal Oxygen

Early acclimatization to high altitude is characterized by various respiratory, hematological, and cardiovascular adaptations that serve to restore oxygen delivery to tissue. However, less is understood about renal function and the role of renal oxygen delivery (RDO2) during high altitude acclimatization. We hypothesized that 1) RDO2 would be reduced after 12 h of high altitude exposure (high altitude day 1) but restored to sea level values after 1 wk (high altitude day 7) and 2) RDO2 would be associated with renal reactivity, an index of acid-base compensation at high altitude. Twenty-four healthy lowlander participants were tested at sea level (344 m, Kelowna, BC, Canada) and on day 1 and day 7 at high altitude (4,330 m, Cerro de Pasco, Peru). Cardiac output, renal blood flow, and arterial and venous blood sampling for renin-angiotensin-aldosterone system hormones and NH2-terminal pro-B-type natriuretic peptides were collected at each time point. Renal reactivity was calculated as follows: (Δarterial bicarbonate)/(Δarterial Pco2) between sea level and high altitude day 1 and sea level and high altitude day 7. The main findings were that 1) RDO2 was initially decreased at high altitude compared with sea level (ΔRDO2: −22 ± 17%, P < 0.001) but was restored to sea level values on high altitude day 7 (ΔRDO2: −6 ± 14%, P = 0.36). The observed improvements in RDO2 resulted from both changes in renal blood flow (Δ from high altitude day 1: +12 ± 11%, P = 0.008) and arterial oxygen content (Δ from high altitude day 1: +44.8 ± 17.7%, P = 0.006) and 2) renal reactivity was positively correlated with RDO2 on high altitude day 7 ( r = 0.70, P < 0.001) but not high altitude day 1 ( r = 0.26, P = 0.29). These findings characterize the temporal responses of renal function during early high altitude acclimatization and the influence of RDO2 in the regulation of acid-base balance.

Improvement in lung diffusion by endothelin A receptor blockade at high altitude

2012 ◽  
Vol 112 (1) ◽  
pp. 20-25 ◽  
Author(s):  
Claire de Bisschop ◽  
Jean-Benoit Martinot ◽  
Gil Leurquin-Sterk ◽  
Vitalie Faoro ◽  
Hervé Guénard ◽  
...  
Keyword(s):  
High Altitude ◽  
Sea Level ◽  
Exercise Capacity ◽  
Barometric Pressure ◽  
Membrane Component ◽  
Alveolar Volume ◽  
Double Blind ◽  
Lung Diffusion ◽  
Endothelin A Receptor ◽  
Endothelin A

Lung diffusing capacity has been reported variably in high-altitude newcomers and may be in relation to different pulmonary vascular resistance (PVR). Twenty-two healthy volunteers were investigated at sea level and at 5,050 m before and after random double-blind intake of the endothelin A receptor blocker sitaxsentan (100 mg/day) vs. a placebo during 1 wk. PVR was estimated by Doppler echocardiography, and exercise capacity by maximal oxygen uptake (V̇o2 max). The diffusing capacities for nitric oxide (DLNO) and carbon monoxide (DLCO) were measured using a single-breath method before and 30 min after maximal exercise. The membrane component of DLCO (Dm) and capillary volume (Vc) was calculated with corrections for hemoglobin, alveolar volume, and barometric pressure. Altitude exposure was associated with unchanged DLCO, DLNO, and Dm but a slight decrease in Vc. Exercise at altitude decreased DLNO and Dm. Sitaxsentan intake improved V̇o2 max together with an increase in resting and postexercise DLNO and Dm. Sitaxsentan-induced decrease in PVR was inversely correlated to DLNO. Both DLCO and DLNO were correlated to V̇o2 max at sea level ( r = 0.41–0.42, P < 0.1) and more so at altitude ( r = 0.56–0.59, P < 0.05). Pharmacological pulmonary vasodilation improves the membrane component of lung diffusion in high-altitude newcomers, which may contribute to exercise capacity.

scholarly journals Cerebral Blood Flow, Oxygen Delivery, and Pulsatility Responses to Oxygen Inhalation at High Altitude: Highlanders vs. Lowlanders

2019 ◽  
Vol 10 ◽  
Author(s):  
Chang-Yang Xing ◽  
Jorge M. Serrador ◽  
Allan Knox ◽  
Li-Hua Ren ◽  
Ping Zhao ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
High Altitude ◽  
Oxygen Delivery ◽  
Oxygen Inhalation

Altitude-induced erythrocytic 2,3-DPG and hemoglobin changes in rats of various ages

1975 ◽  
Vol 39 (2) ◽  
pp. 258-261 ◽  
Author(s):  
L. G. Martin ◽  
J. M. Connors ◽  
J. J. McGrath ◽  
J. Freeman
Keyword(s):  
High Altitude ◽  
Sea Level ◽  
Age Groups ◽  
Altitude Exposure ◽  
Simulated High Altitude ◽  
Erythropoietic Response ◽  
2,3 Dpg

Rats of various ages (2, 12, 24, and 40 mo of age) were exposed for 4 wk to either a simulated high altitude of 23,000 ft or to a Peoria, Ill., altitude of 650 ft above sea level. Hematocrit ratios, hemoglobin, and erythrocytic 2,3-diphospho-glycerate (2,3-DPG) concentrations were measured. Hematocrit and hemoglobin determinations revealed a decrease in erythrocytic content with increasing age, and the augmented erythropoietic response was seen in all age groups of animals as a result of altitude exposure. The maximal erythrocytic content of hemoglobin in the 40-mo-old animals was significantly lower than that of all other age groups. Erythrocytic 2,3-DPG levels were significantly changed by aging alone. In the 40-mo-old group there was a 35% increase over the next highest sea-level value. However, while erythrocytic 2,3-DPG content increased significantly in all other age groups following altitude exposure, it decreased 46% in the 40-mo-old group.

Cardiovascular autonomic modulation and activity of carotid baroreceptors at altitude

1998 ◽  
Vol 95 (5) ◽  
pp. 565-573 ◽  
Author(s):  
Luciano BERNARDI ◽  
Claudio PASSINO ◽  
Giammario SPADACINI ◽  
Alessandro CALCIATI ◽  
Robert ROBERGS ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Systolic Blood Pressure ◽  
High Altitude ◽  
Sea Level ◽  
Skin Blood Flow ◽  
Low Frequency ◽  
Sympathetic Activation ◽  
High Altitude Natives

1.To assess the effects of acute exposure to high altitude on baroreceptor function in man we evaluated the effects of baroreceptor activation on R–R interval and blood pressure control at high altitude. We measured the low-frequency (LF) and high-frequency (HF) components in R–R, non-invasive blood pressure and skin blood flow, and the effect of baroreceptor modulation by 0.1-Hz sinusoidal neck suction. Ten healthy sea-level natives and three high-altitude native, long-term sea-level residents were evaluated at sea level, upon arrival at 4970 ;m and 1 week later. 2.Compared with sea level, acute high altitude decreased R–R and increased blood pressure in all subjects [sea-level natives: R–R from 1002±45 to 775±57 ;ms, systolic blood pressure from 130±3 to 150±8 ;mmHg; high-altitude natives: R–R from 809±116 to 749±47 ;ms, systolic blood pressure from 110±12 to 125±11 ;mmHg (P< 0.05 for all)]. One week later systolic blood pressure was similar to values at sea level in all subjects, whereas R–R remained elevated in sea-level natives. The low-frequency power in R–R and systolic blood pressure increased in sea-level natives [R–R-LF from 47±8 to 65±10% (P< 0.05), systolic blood pressure-LF from 1.7±0.3 to 2.6±0.4 ln-mmHg2 (P< 0.05)], but not in high-altitude natives (R–R-LF from 32±13 to 38±19%, systolic blood pressure-LF from 1.9±0.5 to 1.7±0.8 ln-mmHg2). The R–R-HF decreased in sea-level natives but not in high-altitude natives, and no changes occurred in systolic blood pressure-HF. These changes remained evident 1 week later. Skin blood flow variability and its spectral components decreased markedly at high altitude in sea-level natives but showed no changes in high-altitude natives. Neck suction significantly increased the R–R- and systolic blood pressure-LF in all subjects at both sea level and high altitude. 3.High altitude induces sympathetic activation in sea-level natives which is partially counteracted by active baroreflex. Despite long-term acclimatization at sea level, high-altitude natives also maintain active baroreflex at high altitude but with lower sympathetic activation, indicating a persisting high-altitude adaptation which may be genetic or due to baroreflex activity not completely lost by at least 1 year's sea-level residence.

Pulmonary Vascular Reserve and Exercise Capacity at Sea Level and at High Altitude

2013 ◽  
Vol 14 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Adriana Pavelescu ◽  
Vitalie Faoro ◽  
Hervé Guenard ◽  
Claire de Bisschop ◽  
Jean-Benoit Martinot ◽  
...  
Keyword(s):  
High Altitude ◽  
Sea Level ◽  
Exercise Capacity ◽  
Vascular Reserve
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