Increased exercise SaO2 independent of ventilatory acclimatization at 4,300 m

1989 ◽  
Vol 66 (6) ◽  
pp. 2733-2738 ◽  
Author(s):  
P. R. Bender ◽  
R. E. McCullough ◽  
R. G. McCullough ◽  
S. Y. Huang ◽  
P. D. Wagner ◽  
...  
Keyword(s):  
Time Course ◽  
Submaximal Exercise ◽  
Co2 Production ◽  
O2 Consumption ◽  
Moderate Exercise ◽  
O2 Uptake ◽  
Cycle Exercise ◽  
State Cycle ◽  
Arterial O2 Saturation ◽  
Male Subjects

Arterial O2 saturation (Sao2) decreases in hypoxia in the transition from rest to moderate exercise, but it is unknown whether other several weeks at high altitude SaO2 in submaximal exercise follows the same time course and pattern as that of ventilatory acclimatization in resting subjects. Ventilatory acclimatization is essentially complete after approximately 1 wk at 4,300 m, such that improvement in submaximal exercise SaO2 would then require other mechanisms. On days 2, 8, and 22 on Pikes Peak (4,300 m), 6 male subjects performed prolonged steady-state cycle exercise at 79% maximal O2 uptake (VO2 max). Resting SaO2 rose from day 1 (78.4 +/- 1.6%) to day 8 (87.5 +/- 1.4%) and then did not increase further by day 20 (86.4 +/- 0.6%). During exercise, SaO2 values (mean of 5-, 15-, and 30-min measurements) were 72.7% (day 2), 78.6% (day 8), and 82.3% (day 22), meaning that all of the increase in resting SaO2 occurred from day 1 to day 8, but exercise SaO2 increased from day 2 to day 8 (5.9%) and then increased further from day 8 to day 22 (3.7%). On day 22, the exercise SaO2 was higher than on day 8 despite an unchanged ventilation and O2 consumption. The increased exercise SaO2 was accompanied by decreased CO2 production. The mechanisms responsible for the increased exercise SaO2 require further investigation.

Effect of duration of exercise on excess postexercise O2 consumption

1987 ◽  
Vol 62 (2) ◽  
pp. 485-490 ◽  
Author(s):  
R. Bahr ◽  
I. Ingnes ◽  
O. Vaage ◽  
O. M. Sejersted ◽  
E. A. Newsholme
Keyword(s):  
Rectal Temperature ◽  
Time Course ◽  
Control Experiment ◽  
Respiratory Exchange Ratio ◽  
Exercise Duration ◽  
Cycle Ergometer ◽  
O2 Consumption ◽  
Work Intensity ◽  
O2 Uptake ◽  
Male Subjects

This study was undertaken to determine the effect of exercise duration on the time course and magnitude of excess postexercise O2 consumption (EPOC). Six healthy male subjects exercised on separate days for 80, 40, and 20 min at 70% of maximal O2 consumption on a cycle ergometer. A control experiment without exercise was performed. O2 uptake, respiratory exchange ratio (R), and rectal temperature were monitored while the subjects rested in bed 24 h postexercise. An increase in O2 uptake lasting 12 h was observed for all exercise durations, but no increase was seen after 24 h. The magnitude of 12-h EPOC was proportional to exercise duration and equaled 14.4 +/- 1.2, 6.8 +/- 1.7, and 5.1 +/- 1.2% after 80, 40, and 20 min of exercise, respectively. On the average, 12-h EPOC equaled 15.2 +/- 2.0% of total exercise O2 consumption (EOC). There was no difference in EPOC:EOC for different exercise durations. A linear decrease with exercise duration was observed in R between 2 and 24 h postexercise. No change was observed in recovery rectal temperature. It is concluded that EPOC increases linearly with exercise duration at a work intensity of 70% of maximal O2 consumption.

Measurement of metabolic rate in hyperoxia

1981 ◽  
Vol 51 (3) ◽  
pp. 725-731 ◽  
Author(s):  
H. G. Welch ◽  
P. K. Pedersen
Keyword(s):  
Metabolic Rate ◽  
Submaximal Exercise ◽  
Co2 Production ◽  
O2 Uptake ◽  
Vo2 Max ◽  
Conventional Calculation ◽  
Mixing Chamber ◽  
Douglas Bag ◽  
Douglas Bag Method ◽  
Fick Equation

The conventional Douglas bag calculation for estimating O2 uptake (VO2) during exercise in normoxia and hyperoxia, VO2 = VE . (FIO2 . FEN2/FIN2 - FEO2), was tested against two other valid calculations: the Fick equation, VO2 = VI . FIO2 - VE . FEO2, and the equation VO2 = VI - VE - VCO2 (VE and VI are expired and inspired ventilation, respectively; FEO2 and FIO2 are expired and inspired O2 contents, respectively; FEN2 and FIN2 are expired and inspired N2 contents, respectively; and VCO2 is CO2 production.). These calculations are based on different assumptions, in part, and are affected to a varying degree of errors in volume or gas fraction measurements. With the conventional Douglas bag technique, we found evidence of an overestimate of VO2 during hyperoxia. After the introduction of a mixing chamber for sampling expired air, the means of the three methods were not significantly different. The variability among the methods was least with the conventional calculation but increased with higher O2 fractions. The average VO2 for submaximal exercise in hyperoxia was not significantly different from that of normoxia. VO2 max was significantly higher in hyperoxia. The increased variability of the Douglas bag method in hyperoxia may lead to overestimates of VO2 max unless special precautions are taken.

Muscle metabolism during exercise in the heat in unacclimatized and acclimatized humans

1985 ◽  
Vol 59 (5) ◽  
pp. 1350-1354 ◽  
Author(s):  
D. S. King ◽  
D. L. Costill ◽  
W. J. Fink ◽  
M. Hargreaves ◽  
R. A. Fielding
Keyword(s):  
Muscle Glycogen ◽  
Respiratory Exchange Ratio ◽  
Muscle Metabolism ◽  
Submaximal Exercise ◽  
Intense Exercise ◽  
O2 Uptake ◽  
Heat Acclimatization ◽  
Fuel Selection ◽  
Muscle Ph ◽  
Male Subjects

The effect of heat acclimatization on aerobic exercise tolerance in the heat and on subsequent sprint exercise performance was investigated. Before (UN) and after (ACC) 8 days of heat acclimatization, 10 male subjects performed a heat-exercise test (HET) consisting of 6 h of intermittent submaximal [50% of the maximal O2 uptake] exercise in the heat (39.7 degrees C dB, 31.0% relative humidity). A 45-s maximal cycle ride was performed before (sprint 1) and after (sprint 2) each HET. Mean muscle glycogen use during the HET was lower following acclimatization [ACC = 28.6 +/- 6.4 (SE) and UN = 57.4 +/- 5.1 mmol/kg; P less than 0.05]. No differences were noted between the UN and ACC trials with respect to blood glucose, lactate (LA), or respiratory exchange ratio. During the UN trial only, total work output during sprint 2 was reduced compared with sprint 1 (24.01 +/- 0.80 vs. 21.56 +/- 1.18 kJ; P less than 0.05). This reduction in sprint performance was associated with an attenuated fall in muscle pH following sprint 2 (6.86 vs. 6.67, P less than 0.05) and a reduced accumulation of LA in the blood. These data indicate that heat acclimatization produced a shift in fuel selection during submaximal exercise in the heat. The observed sparing of muscle glycogen may be associated with the enhanced ability to perform highly intense exercise following prolonged exertion in the heat.

Effects of beta-adrenergic blockade on O2 uptake during submaximal and maximal exercise

1983 ◽  
Vol 54 (4) ◽  
pp. 901-905 ◽  
Author(s):  
P. A. Tesch ◽  
P. Kaiser
Keyword(s):  
Heart Rate ◽  
Maximal Exercise ◽  
Pulmonary Ventilation ◽  
Submaximal Exercise ◽  
Beta Blockade ◽  
Adrenergic Blockade ◽  
Maximal Heart Rate ◽  
O2 Consumption ◽  
O2 Uptake ◽  
Beta Adrenergic

Changes in cardiorespiratory variables and perceived rate of exertion (RPE) were studied in 13 trained men performing cycling exercise before and after beta-adrenergic blockade. Propranolol (Inderal, 80 mg) was administered orally 2 h prior to standardized maximal and submaximal exercises. Muscle biopsies were obtained from vastus lateralis at rest for subsequent histochemical analyses of muscle fiber type distribution and capillary supply. During submaximal exercise O2 consumption decreased from 2.76 to 2.59 l . min-1 following blockade (P less than 0.01), whereas heart rate decreased from 157 to 113 beats . min-1 (P less than 0.001). Maximal O2 uptake was lowered from 3.79 to 3.26 l . min-1 (P less than 0.001) and maximal heart rate was reduced from 192 to 142 beats . min-1 (P less than 0.001) as a result of the blockade. Pulmonary ventilation was unaltered in both exercise conditions. “Local” RPE was higher (P less than 0.001) than “central” RPE after beta-blockade in both submaximal and maximal exercise. During normal condition this difference did not appear. Changes in both local and central RPE during submaximal exercise were positively correlated to changes in O2 uptake. Individual variations in the metabolic profile of the exercising muscle had no influence on beta-blockade-induced changes in O2 uptake. It is concluded that blockade of beta-adrenergic receptors reduces O2 consumption during submaximal (approximately 73% maximal O2 uptake) and maximal exercise in habitually trained men.

Epinephrine-induced changes in muscle carbohydrate metabolism during exercise in male subjects

1986 ◽  
Vol 60 (5) ◽  
pp. 1466-1470 ◽  
Author(s):  
E. Jansson ◽  
P. Hjemdahl ◽  
L. Kaijser
Keyword(s):  
Submaximal Exercise ◽  
Glycogen Depletion ◽  
Cycle Exercise ◽  
Before And After ◽  
Arterial Plasma ◽  
Induced Changes ◽  
Male Subjects ◽  
Muscle Biopsies ◽  
Healthy Males ◽  
Epinephrine Concentration

Epinephrine increases glycogenolysis in resting skeletal muscle, but less is known about the effects of epinephrine on exercising muscle. To study this, epinephrine was given intraarterially to one leg during two-legged cycle exercise in nine healthy males. The epinephrine-stimulated (EPI) and non-stimulated (C) legs were compared with regard to glycogen, glucose, glucose 6-phosphate (G6P), alpha-glycerophosphate (alpha-GP), and lactate contents in muscle biopsies taken before and after the 45-min submaximal exercise, as well as brachial arterial-femoral venous (a-fv) differences for epinephrine, norepinephrine, lactate, glucose, and O2 during exercise. During exercise the arterial plasma epinephrine concentration was 4.8 +/- 0.8 nmol/l and the femoral venous epinephrine concentrations were 10.3 +/- 2.1 and 3.9 +/- 0.6 nmol/l, respectively, in the EPI and C leg. During exercise the a-fv difference for lactate was greater (-0.41 +/- 0.14 vs. -0.21 +/- 0.14 mmol/l; P less than 0.001), and the a-fv difference for glucose was smaller (0.07 +/- 0.12 vs. 0.24 +/- 0.12 mmol/l; P less than 0.01) in the EPI than in the C leg, but the a-fv differences for O2 were similar. Muscle glycogen depletion (137 +/- 63 vs. 99 +/- 43 mmol/kg dry muscle; P less than 0.1) and the muscle concentrations of glucose (P less than 0.05), alpha-GP (P less than 0.1), G6P (P greater than 0.1), and lactate (P greater than 0.1) tended to be higher in the EPI than the C leg after exercise. These findings suggest that physiological concentrations of epinephrine may enhance muscle glycogenolysis during submaximal exercise in male subjects.

Coupling of muscle phosphorylation potential to glycolysis during work after short-term training

1994 ◽  
Vol 76 (6) ◽  
pp. 2586-2593 ◽  
Author(s):  
J. Cadefau ◽  
H. J. Green ◽  
R. Cusso ◽  
M. Ball-Burnett ◽  
G. Jamieson
Keyword(s):  
Muscle Glycogen ◽  
Needle Biopsy ◽  
Vastus Lateralis ◽  
O2 Uptake ◽  
Cycle Exercise ◽  
Short Term ◽  
Metabolic Adaptations ◽  
Before And After ◽  
Male Subjects ◽  
Pyruvate Ratio

To examine whether the metabolic adaptations to short-term training are expressed over a range of submaximal levels of mitochondrial respiration, seven untrained male subjects [maximal O2 uptake (VO2max) = 45.9 +/- 1.9 (SE) ml.kg-1.min-1] performed a progressive three-stage protocol of cycle exercise at 60% (20 min), 79% (20 min), and 92% (11 min) of pretraining VO2max before and after training. Training consisted of 5–6 days of cycling for 2 h/day at 65% VO2max. Muscle tissue rapidly obtained from the vastus lateralis by needle biopsy indicated that training blunted (P < 0.05) the increase in lactate observed at 60% (23.4 +/- 6.5 vs. 12.4 +/- 2.9 mmol/kg dry wt), 79% (48.9 +/- 5.1 vs. 25.6 +/- 5.2 mmol/kg dry wt), and 92% (68.3 +/- 6.4 vs. 41.5 +/- 6.5 mmol/kg dry wt) of VO2max. Training also resulted in a higher phosphocreatine and lower creatine and P(i) concentrations at both 79% (P < 0.05) and 92% (P < 0.05) of VO2max and higher muscle glycogen levels (P < 0.05). These changes were accompanied by small but significant reductions (P < 0.05) in O2 uptake at the two higher exercise intensities. Given that the lactate-to-pyruvate ratio and the calculated free ADP and AMP were also reduced (P < 0.05), it would appear that short-term training results in a tighter metabolic control over a range of mitochondrial respiratory rates.

Effect of feeding and fasting on excess postexercise oxygen consumption

1991 ◽  
Vol 71 (6) ◽  
pp. 2088-2093 ◽  
Author(s):  
R. Bahr ◽  
O. M. Sejersted
Keyword(s):  
Time Course ◽  
Exercise Bout ◽  
Strenuous Exercise ◽  
O2 Consumption ◽  
O2 Uptake ◽  
Fed State ◽  
Thermic Effect Of Food ◽  
Effect Of Food ◽  
The Difference ◽  
Excess Postexercise Oxygen Consumption

This study was undertaken to determine the effect of fasting on the magnitude and time course of the excess postexercise O2 consumption (EPOC). Six lean untrained subjects were studied in the fasted state for 7 h after a previous strenuous exercise bout (80 min at 75% of maximal O2 uptake) and in a control experiment. The results were compared with identical control and exercise experiments where the subjects were fed a 4.5-MJ test meal after 2 h of rest. EPOC was calculated as the difference in O2 uptake between the corresponding control and exercise experiments. The total EPOC (0–7 h postexercise) was 20.9 +/- 4.5 (fasting) and 21.1 +/- 3.6 liters (food, NS). A significant prolonged EPOC component was observed in the fasted and in the fed state. The thermic effect of food (TEF) was calculated from O2 consumption and respiratory exchange ratio as the difference in energy expenditure between the corresponding food and fasting experiments. The total TEF (0–5 h postprandial) was 321 +/- 32.0 (control) and 280 +/- 37.7 kJ/5 h (exercise, NS). It is concluded that the prolonged component of EPOC is present in the fasting state. Furthermore, no major interaction effects between food intake and exercise on the postexercise O2 consumption could be detected.

Induced lactacidemia does not affect postexercise O2 consumption

1988 ◽  
Vol 65 (3) ◽  
pp. 1045-1049 ◽  
Author(s):  
D. A. Roth ◽  
W. C. Stanley ◽  
G. A. Brooks
Keyword(s):  
Blood Flow ◽  
Blood Lactate ◽  
Time Course ◽  
Cycle Ergometer ◽  
Base Line ◽  
O2 Consumption ◽  
Total Recovery ◽  
Lactate Levels ◽  
Male Subjects ◽  
Blood Lactate Levels

To study the effects of circulatory occlusion on the time course and magnitude of postexercise O2 consumption (VO2) and blood lactate responses, nine male subjects were studied twice for 50 min on a cycle ergometer. On one occasion, leg blood flow was occluded with surgical thigh cuffs placed below the buttocks and inflated to 200 mmHg. The protocol consisted of a 10-min rest, 12 min of exercise at 40% peak O2 consumption (VO2 peak), and a 28-min resting recovery while respiratory gas exchange was determined breath by breath. Occlusion (OCC) spanned min 6-8 during the 12-min work bout and elicited mean blood lactate of 5.2 +/- 0.8 mM, which was 380% greater than control (CON). During 18 min of recovery, blood lactate after OCC remained significantly above CON values. VO2 was significantly lower during exercise with OCC compared with CON but was significantly higher during the 4 min of exercise after cuff release. VO2 was higher after OCC during the first 4 min of recovery but was not significantly different thereafter. Neither total recovery VO2 (gross recovery VO2 with no base-line subtraction) nor excess postexercise VO2 (net recovery VO2 above an asymptotic base line) was significantly different for OCC and CON conditions (13.71 +/- 0.45 vs. 13.44 +/- 0.61 liters and 4.93 +/- 0.26 vs. 4.17 +/- 0.35 liters, respectively). Manipulation of exercise blood lactate levels had no significant effect on the slow ("lactacid") component of the recovery VO2.

Effects of preexercise snack feeding on endurance cycle exercise

1986 ◽  
Vol 60 (3) ◽  
pp. 980-985 ◽  
Author(s):  
J. T. Devlin ◽  
J. Calles-Escandon ◽  
E. S. Horton
Keyword(s):  
Muscle Glycogen ◽  
Endurance Performance ◽  
Snack Food ◽  
Base Line ◽  
O2 Consumption ◽  
Glycogen Depletion ◽  
Cycle Exercise ◽  
Healthy Human ◽  
Exercise Period ◽  
Male Subjects

We studied the effects of ingesting either a snack food (S) (260 kcal) or placebo (P) 30 min before intermittent cycle exercise at 70% maximal O2 consumption on endurance performance and muscle glycogen depletion in eight healthy human males. Immediately before exercise there were significantly greater increases in plasma glucose (PG) (S +28 +/- 9.7; P +0.1 +/- 0.8 mg/dl) and insulin (S +219 +/- 61.5; P -7 +/- 5.5 pmol/l) (P less than 0.05) following S feeding compared with P. These differences were no longer present by the end of the first exercise period. There were no differences in endurance times (S 52 +/- 6.4; P 48 +/- 5.6 min) or in the extent of muscle glycogen depletion following exercise (S 56 +/- 14.7; P 50 +/- 15.5 micrograms/mg protein) between the two groups. PG was maintained at base-line (prefeeding) concentrations following S, whereas there was a tendency for PG to steadily decrease after P. Total grams of carbohydrate oxidized during exercise did not differ between the two groups (S 120; P 118 g). These results demonstrate that the ingestion of a mixed-macronutrient snack 30 min before exercise does not impair endurance performance nor increase the extent of muscle glycogen depletion during high-intensity cycle exercise in untrained adult male subjects.

Effect of exercise on plasma interferon levels

1985 ◽  
Vol 59 (2) ◽  
pp. 426-428 ◽  
Author(s):  
A. Viti ◽  
M. Muscettola ◽  
L. Paulesu ◽  
V. Bocci ◽  
A. Almi
Keyword(s):  
Blood Lactate ◽  
Plasma Protein ◽  
Bicycle Ergometer ◽  
Submaximal Exercise ◽  
O2 Consumption ◽  
Before And After ◽  
Interferon Activity ◽  
Male Subjects ◽  
Alpha Type ◽  
Acid Labile

The effect of exercise on plasma interferon activity was studied on eight male subjects before and after exercise on a bicycle ergometer for 1 h at 70% of their maximal O2 consumption (VO2 max). Acid-labile interferon, alpha-type according to immunological characterization, rose significantly from a preexercise value of 3 +/- 1 to 7 +/- 2 IU/ml postexercise. Negligible changes were recorded for plasma protein, lipid, and glucose concentrations, whereas blood lactate slightly increased only at the end of exercise. According to hematocrit and plasma protein values before and after exercise, hemoconcentration did not occur. These data provide evidence that plasma interferon activity increased following a bout of submaximal exercise.

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