Ammonia uptake in inactive muscles during exercise in humans

1996 ◽  
Vol 270 (1) ◽  
pp. E101-E106 ◽  
Author(s):  
J. Bangsbo ◽  
B. Kiens ◽  
E. A. Richter
Keyword(s):  
Ammonium Uptake ◽  
Early Recovery ◽  
Arm Exercise ◽  
Ammonia Uptake ◽  
Exercise Period ◽  
Net Uptake ◽  
Leg Muscle ◽  
Arterial Plasma ◽  
Male Subjects ◽  
Exercise In Humans

The present study examined NH3 (ammonia and ammonium) uptake in resting leg muscle. Six male subjects performed intermittent arm exercise at various intensities in two separate 32-min periods (part I and part II) and in one subsequent 20-min period in which one-legged exercise was also performed (part III). The arterial plasma NH3 concentration was 79.6 +/- 9.6 (SE) mumol/l at rest and 88.1 +/- 9.1, 98.1 +/- 8.1, and 210.2 +/- 7.5 mumol/l after 10 min of exercise in parts I, II, and III, respectively. The corresponding NH3 uptakes in the resting leg were 3.3 +/- 1.3 (rest), 7.8 +/- 1.5, 14.0 +/- 4.5, and 57.7 +/- 18.3 mumol/min. Throughout each exercise period a net uptake of NH3 was observed in the resting leg (P < 0.05), but uptake decreased to resting values within 5 min of termination of exercise. The muscle NH3 concentration of 195.1 +/- 15.0 mumol/kg wet wt at rest was largely unchanged throughout the experiment. The present data suggest that resting muscles extract NH3 and contribute significantly to clearance of NH3 during exercise and in early recovery from exercise. The extracted NH3 appears to be metabolized within the resting muscles.

Contributions of working muscle to whole body lipid metabolism are altered by exercise intensity and training

2007 ◽  
Vol 292 (1) ◽  
pp. E107-E116 ◽  
Author(s):  
Anne L. Friedlander ◽  
Kevin A. Jacobs ◽  
Jill A. Fattor ◽  
Michael A. Horning ◽  
Todd A. Hagobian ◽  
...  
Keyword(s):  
Lipid Metabolism ◽  
Lipid Oxidation ◽  
Exercise Intensity ◽  
Whole Body ◽  
Body Lipid ◽  
Muscle Lipid ◽  
Before And After ◽  
Net Uptake ◽  
Leg Muscle ◽  
Male Subjects

To evaluate the contribution of working muscle to whole body lipid oxidation, we examined the effects of exercise intensity and endurance training (9 wk, 5 days/wk, 1 h, 75% V̇o2 peak) on whole body and leg free fatty acid (FFA) kinetics in eight male subjects (26 ± 1 yr, means ± SE). Two pretraining trials [45 and 65% V̇o2 max (45UT, 65UT)] and two posttraining trials [65% of pretraining V̇o2 peak (ABT), and 65% of posttraining V̇o2 peak (RLT)] were performed using [1-13C]palmitate infusion and femoral arteriovenous sampling. Training increased V̇o2 peak by 15% (45.2 ± 1.2 to 52.0 ± 1.8 ml·kg−1·min−1, P < 0.05). Muscle FFA fractional extraction was lower during exercise (EX) compared with rest regardless of workload or training status (≈20 vs. 48%, P < 0.05). Two-leg net FFA balance increased from net release at rest (≈−36 μmol/min) to net uptake during EX for 45UT (179 ± 75), ABT (236 ± 63), and RLT (136 ± 110) ( P < 0.05), but not 65UT (51 ± 127). Leg FFA tracer measured uptake was higher during EX than rest for all trials and greater during posttraining in RLT (716 ± 173 μmol/min) compared with pretraining (45UT 450 ± 80, 65UT 461 ± 72, P < 0.05). Leg muscle lipid oxidation increased with training in ABT (730 ± 163 μmol/min) vs. 65UT (187 ± 94, P < 0.05). Leg muscle lipid oxidation represented ∼62 and 30% of whole body lipid oxidation at lower and higher relative intensities, respectively. In summary, training can increase working muscle tracer measured FFA uptake and lipid oxidation for a given power output, but both before and after training the association between whole body and leg lipid metabolism is reduced as exercise intensity increases.

scholarly journals Cerebral ammonia uptake and accumulation during prolonged exercise in humans

2005 ◽  
Vol 563 (1) ◽  
pp. 285-290 ◽  
Author(s):  
Lars Nybo ◽  
Mads K. Dalsgaard ◽  
Adam Steensberg ◽  
Kirsten Møller ◽  
Niels H. Secher
Keyword(s):  
Prolonged Exercise ◽  
Ammonia Uptake ◽  
Exercise In Humans

Pro- and macroglycogenolysis: relationship with exercise intensity and duration

2001 ◽  
Vol 90 (3) ◽  
pp. 873-879 ◽  
Author(s):  
T. E. Graham ◽  
K. B. Adamo ◽  
J. Shearer ◽  
I. Marchand ◽  
B. Saltin
Keyword(s):  
Skeletal Muscle ◽  
Metabolic Regulation ◽  
Human Skeletal Muscle ◽  
Exercise Period ◽  
Group 3 ◽  
Group 2 ◽  
Male Subjects ◽  
Muscle Biopsies ◽  
Over Time ◽  
Group 1

We examined the net catabolism of two pools of glycogen, proglycogen (PG) and macroglycogen (MG), in human skeletal muscle during exercise. Male subjects ( n = 21) were assigned to one of three groups. Group 1 exercised 45 min at 70% maximal O2 uptake (V˙o 2 max) and had muscle biopsies at rest, 15 min, and 45 min. Group 2 exercised at 85%V˙o 2 max to exhaustion (45.4 ± 3.4 min) and had biopsies at rest, 10 min, and exhaustion. Group 3 performed three 3-min bouts of exercise at 100%V˙o 2 max separated by 6 min of rest. Biopsies were taken at rest and after each bout. Group 1 had small MG and PG net glycogenolysis rates (ranging from 3.8 ± 1.0 to 2.4 ± 0.6 mmol glucosyl units · kg−1 · min−1) that did not change over time. In group 2, the MG glycogenolysis rate remained low and unchanged over time, whereas the PG rate was initially elevated (11.3 ± 2.3 mmol glucosyl units · kg−1 · min−1) and declined ( P ≤ 0.05) with time. During the first 10 min, PG concentration ([PG]) declined ( P ≤ 0.05), whereas MG concentration ([MG]) did not. Similarly, in group 3, in both the first and the second bouts of exercise [PG] declined ( P ≤ 0.05) and [MG] did not, although by the end of the second exercise period the [MG] was lower ( P ≤ 0.05) than the rest level. The net catabolic rates for PG in the first two exercises were 22.6 ± 6.8 and 21.8 ± 8.2 mmol glucosyl units · kg−1 · min−1, whereas the corresponding values for MG were 17.6 ± 6.0 and 10.8 ± 5.6. The MG pool appeared to be more resistant to mobilization, and, when activated, its catabolism was inhibited more rapidly than that of PG. This suggests that the metabolic regulation of the two pools must be different.

Volume changes in the legs of paraplegic subjects during arm exercise

1993 ◽  
Vol 75 (5) ◽  
pp. 2079-2083 ◽  
Author(s):  
M. T. Hopman ◽  
P. H. Verheijen ◽  
R. A. Binkhorst
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Lesion ◽  
Volume Changes ◽  
Arm Exercise ◽  
Cord Injury ◽  
Exercise Period ◽  
Exercise Muscle ◽  
Cord Lesion ◽  
Volume Decrease

The purpose of this study was to examine the inability of paraplegic (P) subjects to redistribute fluid below the spinal cord lesion during arm exercise, with emphasis on the role of the sympathetic system in this redistribution failure. Fifteen male P and 15 male able-bodied [control (C)] subjects performed arm cranking exercise, and volume changes in the calf were measured by strain gauge plethysmography before, during, and after exercise. Muscle pump activity in the legs of C subjects was eliminated. The rate of calf volume decrease at the beginning and halfway points of the exercise period, the total volume decrease during exercise, and the volume increase during recovery were significantly lower in P than in C subjects. Whereas completeness of the lesion had no influence on leg volume changes, the rate of calf volume decrease at the beginning of exercise and the total volume decrease during exercise were significantly correlated with the level of the spinal cord lesion. This study confirms that P subjects are unable to redistribute fluid effectively below the spinal cord injury during arm exercise, which is partly caused by a loss of sympathetically induced vasoconstriction and which appears to be independent of the completeness of the lesion but dependent on its level.

Fluid homoeostasis during prolonged low-intensity walking on consecutive days

1988 ◽  
Vol 75 (1) ◽  
pp. 63-70 ◽  
Author(s):  
J. B. Leiper ◽  
K. McCormick ◽  
J. D. Robertson ◽  
P. H. Whiting ◽  
R. J. Maughan
Keyword(s):  
Plasma Volume ◽  
Fluid Intake ◽  
Sodium Concentration ◽  
Daily Exercise ◽  
Daily Change ◽  
Exercise Period ◽  
Unrestricted Access ◽  
The Difference ◽  
Male Subjects ◽  
Food And Fluid Intake

1. The effect on fluid homoeostasis of walking 37 km on each of 4 consecutive relatively cool days was studied in six male subjects. The daily exercise intensity was consistent and was equivalent to 17(1)% [mean (se)] of maximum oxygen uptake for these subjects. 2. The diet during the study consisted of a mainly carbohydrate breakfast, consumed immediately before each day‘s exercise, and unrestricted access to a normal mixed diet after completion of each day's exercise. Water was allowed ad libitum during the walk. Food and fluid intake were recorded. 3. Body weight remained constant over the 4-day walk. The difference between total daily fluid intake and the corresponding 24 h urine output was 1684 (250) ml, 1621 (522) ml, 1107 (252) ml and 1406 (208) ml, respectively, on each of the 4 exercise days. 4. There was a calculated increase of 21.3(6.6)% in plasma volume over the 4-day walk; the largest daily change [11.3(2.9)%] occurred during the walk on day 1. The increase in plasma volume was maintained for at least 4 days after completion of the walk. 5. From day 2, serum sodium concentration tended to increase during the exercise period and fell to the pre-exercise concentration during the overnight rest periods. The concentration of the other measured serum constituents remained relatively constant, and serum osmolality did not alter over the study period.

Aminophylline and interstitial adenosine during sustained exercise hyperemia

1986 ◽  
Vol 251 (6) ◽  
pp. H1232-H1243 ◽  
Author(s):  
L. P. Thompson ◽  
M. W. Gorman ◽  
H. V. Sparks
Keyword(s):  
Interstitial Fluid ◽  
Standard Dose ◽  
Adenosine Release ◽  
Adenosine Receptor Antagonist ◽  
Adenosine Concentration ◽  
Exercise Hyperemia ◽  
Before And After ◽  
Exercise Period ◽  
Arterial Plasma ◽  
Plasma Adenosine

We tested the hypothesis that an increase in interstitial fluid (ISF) adenosine concentration contributes to vasodilation of high oxidative skeletal muscle during sustained free-flow exercise. Canine calf muscles were stimulated at 3 Hz for 10 min before and after the infusion of the adenosine receptor antagonist aminophylline (10 mg/kg). The vasodilation that occurred during aminophylline infusion was allowed to decay before the postaminophylline exercise period was begun. This dose of aminophylline shifted the response to infused adenosine 20-fold during rest and reduced the response to a standard dose by 90% during exercise. Aminophylline had no significant effect on blood flow or on O2 consumption at rest or during exercise. Adenosine release (venous minus arterial plasma concentration times plasma flow) increased during 3-Hz exercise both before and after aminophylline infusion, but venous plasma adenosine concentration did not increase in either case. We developed a mathematical model of adenosine movement between ISF and plasma to help us judge whether to use adenosine release or venous concentration as an index of ISF adenosine and decided that venous concentration should be used. We conclude that aminophylline has no effect on sustained 3-Hz exercise hyperemia because under these conditions ISF adenosine concentration does not increase.

scholarly journals Hyperoxia decreases muscle glycogenolysis, lactate production, and lactate efflux during steady-state exercise

2006 ◽  
Vol 290 (6) ◽  
pp. E1180-E1190 ◽  
Author(s):  
Trent Stellingwerff ◽  
Paul J. LeBlanc ◽  
Melanie G. Hollidge ◽  
George J. F. Heigenhauser ◽  
Lawrence L. Spriet
Keyword(s):  
Venous Blood ◽  
Lactate Production ◽  
Flow Measurements ◽  
Lactate Accumulation ◽  
Pyruvate Oxidation ◽  
Exercise Period ◽  
Lactate And Pyruvate ◽  
Exercise Muscle ◽  
Blood Flow Measurements ◽  
Male Subjects

The aim of this study was to determine whether the decreased muscle and blood lactate during exercise with hyperoxia (60% inspired O2) vs. room air is due to decreased muscle glycogenolysis, leading to decreased pyruvate and lactate production and efflux. We measured pyruvate oxidation via PDH, muscle pyruvate and lactate accumulation, and lactate and pyruvate efflux to estimate total pyruvate and lactate production during exercise. We hypothesized that 60% O2 would decrease muscle glycogenolysis, resulting in decreased pyruvate and lactate contents, leading to decreased muscle pyruvate and lactate release with no change in PDH activity. Seven active male subjects cycled for 40 min at 70% V̇o2 peak on two occasions when breathing 21 or 60% O2. Arterial and femoral venous blood samples and blood flow measurements were obtained throughout exercise, and muscle biopsies were taken at rest and after 10, 20, and 40 min of exercise. Hyperoxia had no effect on leg O2 delivery, O2 uptake, or RQ during exercise. Muscle glycogenolysis was reduced by 16% with hyperoxia (267 ± 19 vs. 317 ± 21 mmol/kg dry wt), translating into a significant, 15% reduction in total pyruvate production over the 40-min exercise period. Decreased pyruvate production during hyperoxia had no effect on PDH activity (pyruvate oxidation) but significantly decreased lactate accumulation (60%: 22.6 ± 6.4 vs. 21%: 31.3 ± 8.7 mmol/kg dry wt), lactate efflux, and total lactate production over 40 min of cycling. Decreased glycogenolysis in hyperoxia was related to an ∼44% lower epinephrine concentration and an attenuated accumulation of potent phosphorylase activators ADPf and AMPf during exercise. Greater phosphorylation potential during hyperoxia was related to a significantly diminished rate of PCr utilization. The tighter metabolic match between pyruvate production and oxidation resulted in a decrease in total lactate production and efflux over 40 min of exercise during hyperoxia.

Myocellular triacylglycerol breakdown in females but not in males during exercise

2002 ◽  
Vol 282 (3) ◽  
pp. E634-E642 ◽  
Author(s):  
Charlotte H. Steffensen ◽  
Carsten Roepstorff ◽  
Marianne Madsen ◽  
Bente Kiens
Keyword(s):  
Peak Oxygen Uptake ◽  
Activity Level ◽  
Training Status ◽  
Plasma Insulin Concentration ◽  
Training History ◽  
Males And Females ◽  
Arterial Plasma ◽  
Male Subjects ◽  
And Training ◽  
Epinephrine Concentration

The resting content and use of myocellular triacylglycerol (MCTG) during 90 min of submaximal exercise [60% of peak oxygen uptake (V˙o 2 peak)] were studied in 21 eumenorrheic female and 21 male subjects at different training levels [untrained (UT), moderately trained (MT), and endurance trained (END)]. Males and females were matched according to theirV˙o 2 peak expressed relative to lean body mass, physical activity level, and training history. All subjects ingested the same controlled diet for 8 days, and all females were tested in the midfollicular phase of the menstrual cycle. Resting MCTG, measured with the muscle biopsy technique, averaged 48.4 ± 4.2, 48.5 ± 8.4, and 52.2 ± 5.8 mmol/kg dry wt in UT, MT, and END females, respectively, and 34.1 ± 4.9, 31.6 ± 3.3, and 38.4 ± 3.0 mmol/kg dry wt in UT, MT, and END males, respectively ( P < 0.001, females vs. males in all groups). Exercise decreased MCTG content in the female subjects by an average of 25%, regardless of training status, whereas in the male groups MCTG content was unaffected by exercise. The arterial plasma insulin concentration was higher ( P < 0.05) and the arterial plasma epinephrine concentration was lower ( P < 0.05) in the females than in the males at rest and during exercise. MCTG use was correlated to the resting concentration of MCTG ( P < 0.001). We conclude that resting content and use of MCTG during exercise are related to gender and furthermore are independent of training status.

scholarly journals Life-long endurance exercise in humans: Circulating levels of inflammatory markers and leg muscle size

2013 ◽  
Vol 134 (11-12) ◽  
pp. 531-540 ◽  
Author(s):  
U.R. Mikkelsen ◽  
C. Couppé ◽  
A. Karlsen ◽  
J.F. Grosset ◽  
P. Schjerling ◽  
...  
Keyword(s):  
Endurance Exercise ◽  
Inflammatory Markers ◽  
Muscle Size ◽  
Leg Muscle ◽  
Long Endurance ◽  
Circulating Levels ◽  
Exercise In Humans

EFFECTS OF EXERCISE AND A CHOLESTEROL-FREE DIET ON HUMAN SERUM LIPIDS

1966 ◽  
Vol 44 (4) ◽  
pp. 575-580 ◽  
Author(s):  
R. C. Goode ◽  
J. B. Firstbrook ◽  
R. J. Shephard
Keyword(s):  
Serum Cholesterol ◽  
Serum Triglycerides ◽  
Animal Fats ◽  
Cholesterol Levels ◽  
Daily Energy ◽  
Exercise Period ◽  
Small Rise ◽  
And Control ◽  
Caloric Balance ◽  
Male Subjects

Six male subjects were maintained on a diet free of all animal fats for 54 days; carbohydrate intake was increased to maintain an approximate caloric balance. Serum cholesterol decreased progressively to a low plateau over the first 3 weeks, and thereafter showed a small rise, suggesting increased synthesis. Treadmill exercise sufficient to increase daily energy expenditure by a sixth was carried out for 14 days during the phase of increased synthesis. Serum cholesterol levels did not differ significantly between exercised and control subjects, but serum triglycerides decreased significantly (P < 0.05) over the exercise period.

Sign in / Sign up

Export Citation Format

Share Document