Is Gross Efficiency Lower at Acute Simulated Altitude Than at Sea Level?

2013 ◽  
Vol 8 (3) ◽  
pp. 319-322 ◽  
Author(s):  
Dionne A. Noordhof ◽  
Thijs Schoots ◽  
Derk H. Hoekert ◽  
Jos J. de Koning
Keyword(s):  
Heart Rate ◽  
Sea Level ◽  
Exercise Intensity ◽  
Respiratory Exchange Ratio ◽  
Submaximal Exercise ◽  
Specific Power ◽  
Simulated Altitude ◽  
Cycling Exercise ◽  
Gross Efficiency ◽  
Specific Power Output

Purpose:The purpose of this study was to test the assumption that gross efficiency (GE) at sea level (SL) is representative of GE at altitude (AL). It was hypothesized that an increased cost of ventilation and heart rate, combined with a higher respiratory-exchange ratio, at AL might result in a decrease in GE.Methods:Trained men (N = 16) completed 2 maximal incremental tests and 2 GE tests, 1 at SL and 1 at an acute simulated AL of 1500 m (hypobaric chamber). GE was determined during submaximal exercise at 45%, 55%, and 65% of the altitude-specific power output attained at VO2max.Results:GE determined at the highest submaximal exercise intensity with a mean RER ≤1.0, matched for both conditions, was significantly lower at AL (AL 20.7% ± 1.1% and SL 21.4% ± 0.8%, t15 = 2.9, P < .05).Conclusion:These results demonstrate that moderate AL resulted in a significantly lower GE during cycling exercise than SL. However, it might be that the lower GE at AL is caused by the lower absolute exercise intensity.

scholarly journals Cycling at Altitude: Lower Absolute Power Output as the Main Cause of Lower Gross Efficiency

2019 ◽  
Vol 14 (8) ◽  
pp. 1117-1123
Author(s):  
Dennis van Erck ◽  
Eric J. Wenker ◽  
Koen Levels ◽  
Carl Foster ◽  
Jos J. de Koning ◽  
...  
Keyword(s):  
Sea Level ◽  
Exercise Intensity ◽  
Power Output ◽  
High Intensity ◽  
High Intensity Exercise ◽  
Simulated Altitude ◽  
Absolute Power ◽  
Gross Efficiency ◽  
Relative Exercise Intensity ◽  
Negative Effect

Background: Although cyclists often compete at altitude, the effect of altitude on gross efficiency (GE) remains inconclusive. Purpose: To investigate the effect of altitude on GE at the same relative exercise intensity and at the same absolute power output (PO) and to determine the effect of altitude on the change in GE during high-intensity exercise. Methods: Twenty-one trained men performed 3 maximal incremental tests and 5 GE tests at sea level, 1500 m, and 2500 m of acute simulated altitude. The GE tests at altitude were performed once at the same relative exercise intensity and once at the same absolute PO as at sea level. Results: Altitude resulted in an unclear effect at 1500 m (−3.8%; ±3.3% [90% confidence limit]) and most likely negative effect at 2500 m (−6.3%; ±1.7%) on pre-GE, when determined at the same relative exercise intensity. When pre-GE was determined at the same absolute PO, unclear differences in GE were found (−1.5%; ±2.6% at 1500 m; −1.7%; ±2.4% at 2500 m). The effect of altitude on the decrease in GE during high-intensity exercise was unclear when determined at the same relative exercise intensity (−0.4%; ±2.8% at 1500 m; −0.7%; ±1.9% at 2500 m). When GE was determined at the same absolute PO, altitude resulted in a substantially smaller decrease in GE (2.8%; ±2.4% at 1500 m; 5.5%; ±2.9% at 2500 m). Conclusion: The lower GE found at altitude when exercise is performed at the same relative exercise intensity is mainly caused by the lower PO at which cyclists exercise.

Submaximal exercise intensity modulates acute post-exercise heart rate variability

2016 ◽  
Vol 116 (4) ◽  
pp. 697-706 ◽  
Author(s):  
Scott Michael ◽  
Ollie Jay ◽  
Mark Halaki ◽  
Kenneth Graham ◽  
Glen M. Davis
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Exercise Intensity ◽  
Submaximal Exercise ◽  
Exercise Heart Rate ◽  
Post Exercise

Recovery of Cycling Gross Efficiency After Time-Trial Exercise

2018 ◽  
Vol 13 (8) ◽  
pp. 1028-1033 ◽  
Author(s):  
Sjors Groot ◽  
Lars H.J. van de Westelaken ◽  
Dionne A. Noordhof ◽  
Koen Levels ◽  
Jos J. de Koning
Keyword(s):  
High Intensity ◽  
Time Course ◽  
Time Trial ◽  
Exercise Bout ◽  
Submaximal Exercise ◽  
High Intensity Exercise ◽  
Cycling Exercise ◽  
Gross Efficiency ◽  
Before And After ◽  
The Difference

Background: Research has shown that gross efficiency (GE) declines during high-intensity exercise, but the time course of recovery of GE after high-intensity exercise has not yet been investigated. Purpose: To determine the time course of the recovery of GE after time trials (TTs) of different lengths. Methods: Nineteen trained male cyclists participated in this study. Before and after TTs of 2000 and 20,000 m, subjects performed submaximal exercise at 55% of the power output attained at maximal oxygen uptake (PVO2max). The postmeasurement continued until 30 min after the end of the TT, during which GE was determined over 3-min intervals. The magnitude-based-inferences approach was used for statistical analysis. Results: GE decreased substantially during the 2000-m and 20,000-m TTs (−11.8% [3.6%] and −6.2% [4.0%], respectively). A most likely and very likely recovery of GE was found during the first half of the submaximal exercise bout performed after the 2000-m, with only a possible increase in GE during the first part of the submaximal exercise bout performed after the 20,000-m. After both distances, GE did not fully recover to the initial pre-TT values, as the difference between the pre-TT value and average GE value of minutes 26–29 was still most likely negative for both the 2000- and 20,000-m (−6.1% [2.8%] and −7.0% [4.5%], respectively). Conclusions: It is impossible to fully recover GE after TTs of 2000- or 20,000-m during 30 min of submaximal cycling exercise performed at an intensity of 55% PVO2max.

Substrate Metabolism during Exercise in Children and the “Crossover Concept”

1999 ◽  
Vol 11 (1) ◽  
pp. 12-21 ◽  
Author(s):  
Glen E. Duncan ◽  
Edward T. Howley
Keyword(s):  
Energy Source ◽  
Exercise Intensity ◽  
Respiratory Exchange Ratio ◽  
Fat Oxidation ◽  
Submaximal Exercise ◽  
Substrate Metabolism ◽  
Response To Exercise ◽  
And Training

This review addresses issues related to substrate metabolism in children and how this information compares and contrasts to that of adults. The relative percent of fat and carbohydrate (CHO) utilized by an individual can be estimated from respiratory exchange ratio (RER) values between 0.7 (100% fat, 0% CHO) and 1.0 (100% CHO, 0% fat). The rise in RER towards 1.0 in relation to increased exercise intensity demonstrates the augmented role of CHO as an energy source for muscle; however, fat oxidation also represents a major source of energy during exercise of moderate-to-heavy intensity. Preliminary reports suggest that children demonstrate patterns of fat and CHO use in response to exercise intensity similar to those of adults and also show a reduction in RER at submaximal exercise intensities after training. The use of the “crossover concept" may simplify the presentation of how metabolism is affected by exercise intensity and training.

Ventilatory and cardiac responses to hypoxia at submaximal exercise are independent of altitude and exercise intensity

2012 ◽  
Vol 112 (4) ◽  
pp. 566-570 ◽  
Author(s):  
François J. Lhuissier ◽  
Maxime Brumm ◽  
Didier Ramier ◽  
Jean-Paul Richalet
Keyword(s):  
Exercise Intensity ◽  
Aerobic Power ◽  
Arterial Oxygen Saturation ◽  
Submaximal Exercise ◽  
Maximal Aerobic Power ◽  
Arterial Oxygen ◽  
Simulated Altitude ◽  
Cardiac Responses ◽  
The Individual ◽  
Hypoxic Exercise

The hypoxic exercise test combining a 4,800-m simulated altitude and a cycloergometer exercise at 30% of normoxic maximal aerobic power (MAP) is used to evaluate the individual chemosensitivity to hypoxia in submaximal exercise conditions. This test allows the calculation of three main parameters: the decrease in arterial oxygen saturation induced by hypoxia at exercise (ΔSae) and the ventilatory (HVRe) and cardiac (HCRe) responses to hypoxia at exercise. The aim of this study was to determine the influence of altitude and exercise intensity on the values of ΔSae, HVRe, and HCRe. Nine subjects performed hypoxic tests at three simulated altitudes (3,000 m, 4,000 m, and 4,800 m) and three exercise intensities (20%, 30%, and 40% MAP). ΔSae increased with altitude and was higher for 40% MAP than for 20% or 30% ( P < 0.05). For a constant heart rate, the loss in power output induced by hypoxia, relative to ΔSae, was independent of altitude (4,000–4,800 m) and of exercise intensity. HVRe and HCRe were independent of altitude (3,000–4,800 m) and exercise intensity (20%-40% MAP). Moreover, the intraindividual variability of responses to hypoxia was lower during moderate exercise than at rest ( P < 0.05 to P < 0.001). Therefore, we suggest that HVRe and HCRe are invariant parameters that can be considered as intrinsic physiological characteristics of chemosensitivity to hypoxia.

O2 extraction maintains O2 uptake during submaximal exercise with β-adrenergic blockade at 4,300 m

1998 ◽  
Vol 85 (3) ◽  
pp. 1092-1102 ◽  
Author(s):  
Eugene E. Wolfel ◽  
Mark A. Selland ◽  
A. Cymerman ◽  
George A. Brooks ◽  
Gail E. Butterfield ◽  
...  
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Stroke Volume ◽  
High Altitude ◽  
Sea Level ◽  
Submaximal Exercise ◽  
Whole Body ◽  
Exercise Heart Rate ◽  
Adrenergic Blockade ◽  
Mixed Venous

Whole body O2 uptake (V˙o 2) during maximal and submaximal exercise has been shown to be preserved in the setting of β-adrenergic blockade at high altitude, despite marked reductions in heart rate during exercise. An increase in stroke volume at high altitude has been suggested as the mechanism that preserves systemic O2 delivery (blood flow × arterial O2 content) and thereby maintainsV˙o 2 at sea-level values. To test this hypothesis, we studied the effects of nonselective β-adrenergic blockade on submaximal exercise performance in 11 normal men (26 ± 1 yr) at sea level and on arrival and after 21 days at 4,300 m. Six subjects received propranolol (240 mg/day), and five subjects received placebo. At sea level, during submaximal exercise, cardiac output and O2 delivery were significantly lower in propranolol- than in placebo-treated subjects. Increases in stroke volume and O2 extraction were responsible for the maintenance of V˙o 2. At 4,300 m, β-adrenergic blockade had no significant effect onV˙o 2, ventilation, alveolar Po 2, and arterial blood gases during submaximal exercise. Despite increases in stroke volume, cardiac output and thereby O2 delivery were still reduced in propranolol-treated subjects compared with subjects treated with placebo. Further reductions in already low levels of mixed venous O2 saturation were responsible for the maintenance ofV˙o 2 on arrival and after 21 days at 4,300 m in propranolol-treated subjects. Despite similar workloads and V˙o 2, propranolol-treated subjects exercised at greater perceived intensity than subjects given placebo at 4,300 m. The values for mixed venous O2 saturation during submaximal exercise in propranolol-treated subjects at 4,300 m approached those reported at simulated altitudes >8,000 m. Thus β-adrenergic blockade at 4,300 m results in significant reduction in O2delivery during submaximal exercise due to incomplete compensation by stroke volume for the reduction in exercise heart rate. Total bodyV˙o 2 is maintained at a constant level by an interaction between mixed venous O2 saturation, the arterial O2-carrying capacity, and hemodynamics during exercise with acute and chronic hypoxia.

Participation in a 1,000-mile race increases the oxidation of carbohydrate in Alaskan sled dogs

2015 ◽  
Vol 118 (12) ◽  
pp. 1502-1509 ◽  
Author(s):  
Benjamin F. Miller ◽  
Joshua C. Drake ◽  
Frederick F. Peelor ◽  
Laurie M. Biela ◽  
Raymond Geor ◽  
...  
Keyword(s):  
Exercise Intensity ◽  
Respiratory Exchange Ratio ◽  
Exercise Bout ◽  
Endurance Performance ◽  
Submaximal Exercise ◽  
Energy Sources ◽  
Long Distance ◽  
Sled Dogs

The Alaskan Husky has been specifically bred for endurance performance and is capable of extreme endurance performance. We examined sled dogs in the trained state at the beginning of the race season and after a 1,600-km race (Iditarod). Our hypothesis was that lipids would be the predominant substrate during submaximal exercise in long-distance racing sled dogs, and a 1,600-km race would increase the reliance on lipids during an exercise bout at the same absolute exercise intensity. The experiments were completed over three testing periods, which were completed in January of two different years before participation in a 1,600-km race, or in March shortly after completion of a 1,600-km race. After determination of H13CO3− recovery, the dogs were tested with primed continuous infusions of [1,1,2,3,3-2H]glycerol, [3-13C]lactate, or [6,6-2H2]glucose. During exercise, respiratory exchange ratio was significantly higher in raced (0.92 ± 0.01) compared with nonraced (0.87 ± 0.01) dogs. During exercise, glucose rate of appearance was potentially sustained by a large glycerol rate of disappearance with an increase in lactate rates of oxidation after a 1,600-km race. Therefore, contrary to our hypothesis, the sled dogs were dependent on carbohydrate energy sources, a reliance that increased further after participation in a 1,600-km race.

Improved running economy in elite runners after 20 days of simulated moderate-altitude exposure

2004 ◽  
Vol 96 (3) ◽  
pp. 931-937 ◽  
Author(s):  
P. U. Saunders ◽  
R. D. Telford ◽  
D. B. Pyne ◽  
R. B. Cunningham ◽  
C. J. Gore ◽  
...  
Keyword(s):  
Heart Rate ◽  
Respiratory Exchange Ratio ◽  
Minute Ventilation ◽  
Lactate Concentration ◽  
Blood Lactate Concentration ◽  
Running Economy ◽  
Moderate Altitude ◽  
Simulated Altitude ◽  
Distance Runners ◽  
Altitude Exposure

To investigate the effect of altitude exposure on running economy (RE), 22 elite distance runners [maximal O2 consumption (V̇o2) 72.8 ± 4.4 ml·kg-1·min-1; training volume 128 ± 27 km/wk], who were homogenous for maximal V̇o2 and training, were assigned to one of three groups: live high (simulated altitude of 2,000–3,100 m)-train low (LHTL; natural altitude of 600 m), live moderate-train moderate (LMTM; natural altitude of 1,500–2,000 m), or live low-train low (LLTL; natural altitude of 600 m) for a period of 20 days. RE was assessed during three submaximal treadmill runs at 14, 16, and 18 km/h before and at the completion of each intervention. V̇o2, minute ventilation (V̇e), respiratory exchange ratio, heart rate, and blood lactate concentration were determined during the final 60 s of each run, whereas hemoglobin mass (Hbmass) was measured on a separate occasion. All testing was performed under normoxic conditions at ∼600 m. V̇o2 (l/min) averaged across the three submaximal running speeds was 3.3% lower ( P = 0.005) after LHTL compared with either LMTM or LLTL. V̇e, respiratory exchange ratio, heart rate, and Hbmass were not significantly different after the three interventions. There was no evidence of an increase in lactate concentration after the LHTL intervention, suggesting that the lower aerobic cost of running was not attributable to an increased anaerobic energy contribution. Furthermore, the improved RE could not be explained by a decrease in V̇e or by preferential use of carbohydrate as a metabolic substrate, nor was it related to any change in Hbmass. We conclude that 20 days of LHTL at simulated altitude improved the RE of elite distance runners.

Assessing Overreaching With Heart-Rate Recovery: What Is the Minimal Exercise Intensity Required?

2017 ◽  
Vol 12 (4) ◽  
pp. 569-573 ◽  
Author(s):  
Yann Le Meur ◽  
Martin Buchheit ◽  
Anaël Aubry ◽  
Aaron J Coutts ◽  
Christophe Hausswirth
Keyword(s):  
Heart Rate ◽  
Exercise Intensity ◽  
Perceived Exertion ◽  
Maximal Exercise ◽  
Heart Rate Recovery ◽  
Submaximal Exercise ◽  
Rating Of Perceived Exertion ◽  
Training Period ◽  
Maximal Heart Rate ◽  
Warm Up

Purpose:Faster heart-rate recovery (HRR) after high to maximal exercise (≥90% of maximal heart rate) has been reported in athletes suspected of functional overreaching (f-OR). This study investigated whether this response would also occur at lower exercise intensity.Methods:Responses of HRR and rating of perceived exertion (RPE) were compared during an incremental intermittent running protocol to exhaustion in 20 experienced male triathletes (8 control subjects and 13 overload subjects led to f-OR) before and immediately after an overload training period and after a 1-wk taper.Results:Both groups demonstrated an increase in HRR values immediately after the training period, but this change was very likely to almost certainly larger in the f-OR group at all running intensities (large to very large differences, eg, +16 ± 7 vs +3 ± 5 beats/min, in the f-OR and control groups at 11 km/h, respectively). The highest between-groups differences in changes in HRR were reported at 11 km/h (13 ± 4 beats/min) and 12 km/h (10 ± 6 beats/min). A concomitant increase in RPE at all intensities was reported only in the f-OR group (large to extremely large differences, +2.1 ± 1.5 to +0.7 ± 1.5 arbitrary units).Conclusion:These findings confirm that faster HRR does not systematically predict better physical performance. However, when interpreted in the context of the athletes’ fatigue state and training phase, HRR after submaximal exercise may be more discriminant than HRR measures taken after maximal exercise for monitoring f-OR. These findings may be applied in practice by regularly assessing HRR after submaximal exercise (ie, warm-up) for monitoring endurance athletes’ responses to training.

Effects of carvedilol on oxygen uptake and heart rate kinetics in patients with chronic heart failure at simulated altitude

2011 ◽  
Vol 19 (3) ◽  
pp. 444-451 ◽  
Author(s):  
Marlus Karsten ◽  
Mauro Contini ◽  
Claudia Cefalù ◽  
Gaia Cattadori ◽  
Pietro Palermo ◽  
...  
Keyword(s):  
Heart Failure ◽  
Heart Rate ◽  
Oxygen Uptake ◽  
Sea Level ◽  
Cardiopulmonary Exercise Test ◽  
Moderate Intensity ◽  
Moderate Exercise ◽  
Simulated Altitude ◽  
Peripheral Effect ◽  
Clinical Conditions

Background: The response to moderate exercise at altitude in heart failure (HF) is unknown. Methods and results: We evaluated 30 HF patients, (NYHA I-III, 25 M/5 F; 59 ± 10 years; LVEF = 39.6 ± 7.1%), in stable clinical conditions, treated with carvedilol at the maximal tolerated dose. We performed a maximal cardiopulmonary exercise test (CPET) with ramp protocol at sea level to evaluate patients’ performance and two moderate intensity constant workload CPETs (50% of peak workload) at sea level (normoxia) and simulated altitude (hypoxia). Oxygen uptake ([Formula: see text]) and heart rate (HR) on-kinetics at constant workload were assessed calculating the time constant (τ) with a monoexponential equation. [Formula: see text] and HR were higher in hypoxia (0.944 ± 0.233 vs 1.031 ± 0.264 l/min; 100 ± 23 vs 108 ± 22 bpm; p < 0.001). On-kinetics showed a different behavior of τ being [Formula: see text] faster in hypoxia (67.1 ± 23.0 vs. 56.3 ± 19.7 s; p = 0.026) and HR faster in normoxia (49.3 ± 19.4 vs. 62.2 ± 22.5 s; p = 0.018). Ten patients, who lowered oxygen kinetics in hypoxia, had greater HR increase during maximal CPET suggesting lower functional betablockade. The higher τ of [Formula: see text] in hypoxia is likely to be due to a peripheral effect of carvedilol mediated either by β- or α-receptor. Conclusion: HF patients performing moderate exercise at 2000 m simulated altitude have 20% [Formula: see text] increase without trouble at the beginning of exercise when treated with carvedilol.

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