Acid-base regulation during exercise and recovery in humans

1992 ◽  
Vol 72 (3) ◽  
pp. 954-961 ◽  
Author(s):  
W. Stringer ◽  
R. Casaburi ◽  
K. Wasserman
Keyword(s):  
Respiratory Acidosis ◽  
Normal Subjects ◽  
Cycle Ergometer ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Exercise Tests ◽  
Cycle Ergometer Exercise ◽  
Arterial Ph ◽  
Ergometer Exercise ◽  
Exercise In Humans

Arterial pH, PCO2, standard bicarbonate, lactate, and ventilation were measured with a high sampling density during rest, exercise, and recovery in normal subjects performing upright cycle ergometer exercise. Three 6-min constant-work exercise tests (moderate, heavy, and very heavy) were performed by each subject. We found a small respiratory acidosis during the moderate-intensity exercise and an early respiratory acidosis followed by a metabolic acidosis for the heavy- and very-heavy-intensity exercise. During recovery, arterial pH rapidly returned to the preexercise value for the moderate-intensity work. However, arterial pH decreased further during the first 2 min of recovery for the heavy- and very-heavy-intensity work, before a slower return toward the resting values. We conclude that arterial acidosis is the consistent arterial pH reaction for moderate-, heavy-, and very-heavy-intensity cycle ergometer exercise in humans and that this acidosis is blunted but not eliminated by the ventilatory response. During recovery, the return to resting arterial pH and PCO2 and standard bicarbonate appears to be determined by the rate of lactate decline.

Mediation of reduced ventilatory response to exercise after endurance training

1987 ◽  
Vol 63 (4) ◽  
pp. 1533-1538 ◽  
Author(s):  
R. Casaburi ◽  
T. W. Storer ◽  
K. Wasserman
Keyword(s):  
Endurance Training ◽  
Venous Blood ◽  
Normal Subjects ◽  
Cycle Ergometer ◽  
Work Rate ◽  
Exercise Tests ◽  
Average Decrease ◽  
Cycle Ergometer Exercise ◽  
Ergometer Exercise ◽  
The Difference

To investigate the mechanism by which ventilatory (VE) demand is modulated by endurance training, 10 normal subjects performed cycle ergometer exercise of 15 min duration at each of four constant work rates. These work rates represented 90% of the anaerobic threshold (AT) work rate and 25, 50, and 75% of the difference between maximum O2 consumption and AT work rates for that subject (as determined from previous incremental exercise tests). Subjects then underwent 8 wk of strenuous cycle ergometer exercise for 45 min/day. They then repeated the four constant work rate tests at work rates identical to those used before training. During tests before and after training, VE and gas exchange were measured breath by breath and rectal temperature (Tre) was measured continuously. A venous blood sample was drawn at the end of each test and assayed for lactate (La), epinephrine (EPI), and norepinephrine (NE). We found that the VE for below AT work was reduced minimally by training (averaging 3 l/min). For the above AT tests, however, training reduced VE markedly, by an average of 7, 23, and 37 l/min for progressively higher work rates. End-exercise La, NE, EPI, and Tre were all lower for identical work rates after training. Importantly, the magnitude of the reduction in VE was well correlated with the reduction in end-exercise La (r = 0.69) with an average decrease of 5.8 l/min of VE per milliequivalent per liter decrease in La. Correlations of VE with NE, EPI, and Tre were much less strong (r = 0.49, 0.43, and 0.15, respectively).

Peripheral Chemoreflex Drive in Moderate-Intensity Exercise

1996 ◽  
Vol 21 (4) ◽  
pp. 285-300 ◽  
Author(s):  
Claudette M. St. Croix ◽  
David A. Cunningham ◽  
Donald H. Paterson ◽  
John M. Kowalchuk
Keyword(s):  
Peak Level ◽  
Cycle Ergometer ◽  
Open Loop ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Peripheral Chemoreceptor ◽  
Carotid Bodies ◽  
Ergometer Exercise ◽  
End Tidal ◽  
Peripheral Chemoreflex

The purpose of this study was to measure the contribution of the peripheral chemoreceptor (pRc) to [Formula: see text] during the steady-state of moderate-intensity cycle ergometer exercise using continuous hyperoxic suppression of pRc drive, while stabilizing the drive from the central chemoreceptor by clamping end-tidal PCO2 (PETCO2) at the peak level attained during the hyperoxic period of a poikilocapnic ride. In the isocapnic protocol, the PETCO2 was maintained at a constant level by a negative feedback, open loop system. Five subjects completed four repetitions of each of the poikilocapnic and isocapnic protocols. In the poikilocapnic protocol, [Formula: see text] declined following the step into hyperoxia and then began to increase, whereas the decline in [Formula: see text] was maintained in the isocapnic protocol. However, the mean decrease in [Formula: see text] was not significantly different between the poikilocapnic (16.1 ± 5.0%) and isocapnic (14.9 ± 4.4%) protocols. These results suggest that the declining phase of [Formula: see text] is fully complete before the secondary central stimulating actions of hyperoxia on [Formula: see text] and that the pRc contributes about 15% of the drive to breathe in moderate intensity exercise. Key words: ventilatory control, carotid bodies, hyperoxia

scholarly journals Oxygen Cost of Recreational Horse-Riding in Females

2015 ◽  
Vol 12 (6) ◽  
pp. 808-813 ◽  
Author(s):  
Louisa Beale ◽  
Neil S Maxwell ◽  
Oliver R Gibson ◽  
Rosemary Twomey ◽  
Becky Taylor ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Cycle Ergometer ◽  
Peak Oxygen Consumption ◽  
Moderate Intensity ◽  
Oxygen Cost ◽  
Metabolic Demand ◽  
Moderate Intensity Exercise ◽  
The Public ◽  
Horse Riding ◽  
Ergometer Exercise

Background:The purpose of this study was to characterize the physiological demands of a riding session comprising different types of recreational horse riding in females.Methods:Sixteen female recreational riders (aged 17 to 54 years) completed an incremental cycle ergometer exercise test to determine peak oxygen consumption (VO2peak) and a 45-minute riding session based upon a British Horse Society Stage 2 riding lesson (including walking, trotting, cantering and work without stirrups). Oxygen consumption (VO2), from which metabolic equivalent (MET) and energy expenditure values were derived, was measured throughout.Results:The mean VO2 requirement for trotting/cantering (18.4 ± 5.1 ml·kg-1·min-1; 52 ± 12% VO2peak; 5.3 ± 1.1 METs) was similar to walking/trotting (17.4 ± 5.1 ml·kg-1·min-1; 48 ± 13% VO2peak; 5.0 ± 1.5 METs) and significantly higher than for work without stirrups (14.2 ± 2.9 ml·kg-1·min-1; 41 ± 12% VO2peak; 4.2 ± 0.8 METs) (P = .001).Conclusion:The oxygen cost of different activities typically performed in a recreational horse riding session meets the criteria for moderate intensity exercise (3-6 METs) in females, and trotting combined with cantering imposes the highest metabolic demand. Regular riding could contribute to the achievement of the public health recommendations for physical activity in this population.

Effects of sleep deprivation on thermoregulation during exercise

1984 ◽  
Vol 246 (1) ◽  
pp. R72-R77 ◽  
Author(s):  
M. N. Sawka ◽  
R. R. Gonzalez ◽  
K. B. Pandolf
Keyword(s):  
Sleep Deprivation ◽  
Sweat Rate ◽  
Thermal Conductance ◽  
Cycle Ergometer ◽  
Moderate Intensity ◽  
Control Test ◽  
Moderate Intensity Exercise ◽  
Ergometer Exercise ◽  
Total Body ◽  
And Control

Five fit men completed a practice, control, and sleep deprivation exercise test. Two nights of normal sleep preceded the control test, and 33 h of wakefulness preceded the sleep deprivation test. These tests consisted of 20 min of rest followed by 40 min of cycle-ergometer exercise (50% of peak O2 uptake, VO2) in a temperate (ambient temperature, 28 degrees C; relative humidity, 30%)-environment. Esophageal temperature (Tes), local sweat rate (mds), and chest thermal conductance (kch) were continuously measured. During exercise a 0.7 and 0.5 degrees C rise in Tes was found for the sleep deprivation and control tests, respectively. This increase in Tes values from rest to the end of exercise was greater (P = 0.08) for the sleep deprivation than control test. Total body sweat rate, calculated from Potter balance measurements, was 27% less (P less than 0.01) for the sleep deprivation than the control test. Both mds and kch values were lower (P less than 0.05) during the final 20 min of exercise for the sleep deprivation than control test. Final exercise mds values were 19% lower (P less than 0.05) for the sleep deprivation than control test. An asynchronous rather than a normal synchronous mds pattern was frequently observed during the sleep deprivation test. During the sleep deprivation test, the mds sensitivity (delta mds X delta Tes-1) was 38% lower (P less than 0.01) and kch sensitivity (delta kch X delta Tes-1) was 42% lower (P less than 0.05) than during the control test. These data indicate that sleep deprivation decreases evaporative and dry heat loss during moderate-intensity exercise.

Epinephrine infusion during moderate intensity exercise increases glucose production and uptake

2000 ◽  
Vol 278 (5) ◽  
pp. E949-E957 ◽  
Author(s):  
Stuart H. Kreisman ◽  
Nicholas Ah Mew ◽  
Mylène Arsenault ◽  
Sharon J. Nessim ◽  
Jeffrey B. Halter ◽  
...  
Keyword(s):  
Plasma Catecholamines ◽  
Glucose Production ◽  
Cycle Ergometer ◽  
Moderate Intensity ◽  
Metabolic Clearance ◽  
Moderate Exercise ◽  
Moderate Intensity Exercise ◽  
Epinephrine Infusion ◽  
Ergometer Exercise ◽  
Male Subjects

The glucoregulatory response to intense exercise [IE, >80% maximum O2 uptake (V˙o 2 max)] comprises a marked increment in glucose production (Ra) and a lesser increment in glucose uptake (Rd), resulting in hyperglycemia. The Ra correlates with plasma catecholamines but not with the glucagon-to-insulin (IRG/IRI) ratio. If epinephrine (Epi) infusion during moderate exercise were able to markedly stimulate Ra, this would support an important role for the catecholamines' response in IE. Seven fit male subjects (26 ± 2 yr, body mass index 23 ± 0.5 kg/m2,V˙o 2 max 65 ± 5 ml ⋅ kg− 1 ⋅ min− 1) underwent 40 min of postabsorptive cycle ergometer exercise (145 ± 14 W) once without [control (CON)] and once with Epi infusion [EPI (0.1 μg ⋅ kg− 1 ⋅ min− 1)] from 30 to 40 min. Epi levels reached 9.4 ± 0.8 nM (20× rest, 10× CON). Ra increased ∼70% to 3.75 ± 0.53 in CON but to 8.57 ± 0.58 mg ⋅ kg− 1 ⋅ min− 1in EPI ( P < 0.001). Increments in Ra and Epi correlated ( r 2 = 0.923, P ≤ 0.01). In EPI, peak Rd (5.55 ± 0.54 vs. 3.38 ± 0.46 mg ⋅ kg− 1 ⋅ min− 1, P = 0.006) and glucose metabolic clearance rate (MCR, P= 0.018) were higher. The Ra-to-Rdimbalance in EPI caused hyperglycemia (7.12 ± 0.22 vs. 5.59 ± 0.22 mM, P = 0.001) until minute 60 of recovery. A small and late IRG/IRI increase ( P = 0.015 vs. CON) could not account for the Ra increase. Norepinephrine (∼4× increase at peak) did not differ between EPI and CON. Thus Epi infusion during moderate exercise led to increments in Ra and Rd and caused rises of plasma glucose, lactate, and respiratory exchange ratio in fit individuals, supporting a regulatory role for Epi in IE. Epi's effects on Rd and MCR during exercise may differ from its effects at rest.

scholarly journals Modified Total-Body Recumbent Stepper Exercise Test for Assessing Peak Oxygen Consumption in People With Chronic Stroke

2008 ◽  
Vol 88 (10) ◽  
pp. 1188-1195 ◽  
Author(s):  
Sandra A Billinger ◽  
Benjamin Y Tseng ◽  
Patricia M Kluding
Keyword(s):  
Oxygen Consumption ◽  
Exercise Test ◽  
Health Care Professionals ◽  
Cycle Ergometer ◽  
Peak Oxygen Consumption ◽  
Exercise Protocol ◽  
Exercise Tests ◽  
Cycle Ergometer Exercise ◽  
Ergometer Exercise ◽  
Total Body

Background Assessment of peak oxygen consumption (V̇o2peak) using traditional modes of testing such as treadmill or cycle ergometer can be difficult in individuals with stroke due to balance deficits, gait impairments, or decreased coordination. Objective The purpose of this study was to quantitatively assess the validity and feasibility of a modified exercise test using a total-body recumbent stepper (mTBRS-XT) in individuals after stroke. Design A within-subject design, with a sample of convenience, was used. Participants Eleven participants (7 male, 4 female) with a mean of 40.1 months (SD=32.7) after stroke, a mean age of 60.9 years (SD=12.0), and mild to severe lower-extremity Fugl-Myer test scores (range=13–34) completed the study. Methods Participants performed 2 maximal-effort graded exercise tests on separate days using the mTBRS-XT and a cycle ergometer exercise protocol to assess cardiorespiratory fitness. Measurements of V̇o2peak and peak heart rate (peak HR) were obtained during both tests. Results A strong relationship existed between the mTBRS-XT and the cycle ergometer exercise test for V̇o2peak and peak HR (r=.91 and .89, respectively). Mean V̇o2peak was significantly higher for the mTBRS-XT (16.6 mL×kg−1×min−1[SD=4.5]) compared with the cycle ergometer exercise protocol (15.4 mL×kg−1×min−1 [SD=4.5]). All participants performed the mTBRS-XT. One individual with severe stroke was unable to pedal the cycle ergometer. No significant adverse events occurred. Conclusion The mTBRS-XT may be a safe, feasible, and valid exercise test to obtain measurements of V̇o2peak in people with stroke. Health care professionals may use the mTBRS-XT to prescribe aerobic exercise based on V̇o2peak values for individuals with mild to severe deficits after stroke.

Cardiovascular responses to treadmill and cycle ergometer exercise in children and adults

1997 ◽  
Vol 83 (3) ◽  
pp. 948-957 ◽  
Author(s):  
Kenneth R. Turley ◽  
Jack H. Wilmore
Keyword(s):  
Stroke Volume ◽  
Peripheral Resistance ◽  
Cardiovascular Responses ◽  
Cycle Ergometer ◽  
Left Ventricular ◽  
Absolute Amount ◽  
Exercise Tests ◽  
Exercise Modality ◽  
Cycle Ergometer Exercise ◽  
Ergometer Exercise

Turley, Kenneth R., and Jack H. Wilmore. Cardiovascular responses to treadmill and cycle ergometer exercise in children and adults. J. Appl. Physiol. 83(3): 948–957, 1997.—This study was conducted to determine whether submaximal cardiovascular responses at a given rate of work are different in children and adults, and, if different, what mechanisms are involved and whether the differences are exercise-modality dependent. A total of 24 children, 7 to 9 yr old, and 24 adults, 18 to 26 yr old (12 males and 12 females in each group), participated in both submaximal and maximal exercise tests on both the treadmill and cycle ergometer. With the use of regression analysis, it was determined that cardiac output (Q˙) was significantly lower ( P ≤ 0.05) at a given O2 consumption level (V˙o 2, l/min) in boys vs. men and in girls vs. women on both the treadmill and cycle ergometer. The lower Q˙ in the children was compensated for by a significantly higher ( P ≤ 0.05) arterial-mixed venous O2difference to achieve the same or similarV˙o 2. Furthermore, heart rate and total peripheral resistance were higher and stroke volume was lower in the children vs. in the adult groups on both exercise modalities. Stroke volume at a given rate of work was closely related to left ventricular mass, with correlation coefficients ranging from r = 0.89–0.92 and r = 0.88–0.93 in the males and females, respectively. It was concluded that submaximal cardiovascular responses are different in children and adults and that these differences are related to smaller hearts and a smaller absolute amount of muscle doing a given rate of work in the children. The differences were not exercise-modality dependent.

Endurance training decreases plasma glucose turnover and oxidation during moderate-intensity exercise in men

1990 ◽  
Vol 68 (3) ◽  
pp. 990-996 ◽  
Author(s):  
A. R. Coggan ◽  
W. M. Kohrt ◽  
R. J. Spina ◽  
D. M. Bier ◽  
J. O. Holloszy
Keyword(s):  
Endurance Training ◽  
Plasma Glucose ◽  
Cycle Ergometer ◽  
Fat Free Mass ◽  
Strenuous Exercise ◽  
Moderate Intensity ◽  
Glucose Turnover ◽  
Moderate Intensity Exercise ◽  
Ergometer Exercise ◽  
Before And After

To assess the effects of endurance training on plasma glucose kinetics during moderate-intensity exercise in men, seven men were studied before and after 12 wk of strenuous exercise training (3 days/wk running, 3 days/wk cycling). After priming of the glucose and bicarbonate pools, [U-13C] glucose was infused continuously during 2 h of cycle ergometer exercise at 60% of pretraining peak O2 uptake (VO2) to determine glucose turnover and oxidation. Training increased cycle ergometer peak VO2 by 23% and decreased the respiratory exchange ratio during the final 30 min of exercise from 0.89 +/- 0.01 to 0.85 +/- 0.01 (SE) (P less than 0.001). Plasma glucose turnover during exercise decreased from 44.6 +/- 3.5 mumol.kg fat-free mass (FFM)-1.min-1 before training to 31.5 +/- 4.3 after training (P less than 0.001), whereas plasma glucose clearance (i.e., rate of disappearance/plasma glucose concentration) fell from 9.5 +/- 0.6 to 6.4 +/- 0.8 ml.kg FFM-1.min-1 (P less than 0.001). Oxidation of plasma-derived glucose, which accounted for approximately 90% of plasma glucose disappearance in both the untrained and trained states, decreased from 41.1 +/- 3.4 mumol.kg FFM-1.min-1 before training to 27.7 +/- 4.8 after training (P less than 0.001). This decrease could account for roughly one-half of the total reduction in the amount of carbohydrate utilized during the final 30 min of exercise in the trained compared with the untrained state.

Ten days of exercise training reduces glucose production and utilization during moderate-intensity exercise

1994 ◽  
Vol 266 (1) ◽  
pp. E136-E143 ◽  
Author(s):  
L. A. Mendenhall ◽  
S. C. Swanson ◽  
D. L. Habash ◽  
A. R. Coggan
Keyword(s):  
Endurance Training ◽  
Time Course ◽  
Plasma Concentrations ◽  
Glucose Production ◽  
Peak Oxygen Uptake ◽  
Cycle Ergometer ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Ergometer Exercise ◽  
Exercise Induced

We have previously shown that 12 wk of endurance training reduces the rate of glucose appearance (Ra) during submaximal exercise (Coggan, A. R., W. M. Kohrt, R. J. Spina, D. M. Bier, and J. O. Holloszy. J. Appl. Physiol. 68: 990-996, 1990). The purpose of the present study was to examine the time course of and relationship between training-induced alterations in glucose kinetics and endocrine responses during prolonged exercise. Accordingly, seven men were studied during 2 h of cycle ergometer exercise at approximately 60% of pretraining peak oxygen uptake on three occasions: before, after 10 days, and after 12 wk of endurance training. Ra was determined using a primed, continuous infusion of [6,6-2H]glucose. Ten days of training reduced mean Ra during exercise from 36.9 +/- 3.3 (SE) to 28.5 +/- 3.4 mumol.min-1.kg-1 (P < 0.001). Exercise-induced changes in insulin, C-peptide, glucagon, norepinephrine, and epinephrine were also significantly blunted. After 12 wk of training, Ra during exercise was further reduced to 21.5 +/- 3.1 mumol.min-1.kg-1 (P < 0.001 vs. 10 days), but hormone concentrations were not significantly different from 10-day values. The lower glucose Ra during exercise after short-term (10 days) training is accompanied by, and may be due to, altered plasma concentrations of the major glucoregulatory hormones. However, other adaptations must be responsible for the further reduction in Ra with more prolonged training.

Breath-to-breath monitoring of inspiratory occlusion pressures in humans

1981 ◽  
Vol 51 (2) ◽  
pp. 520-523 ◽  
Author(s):  
S. A. Ward ◽  
K. A. Agleh ◽  
C. S. Poon
Keyword(s):  
Steady State ◽  
Cycle Ergometer ◽  
Moderate Intensity ◽  
Occlusion Pressure ◽  
Low Resistance ◽  
Airway Occlusion ◽  
Cycle Ergometer Exercise ◽  
Occlusion Device ◽  
Ergometer Exercise ◽  
Breath Monitoring

A pneumatically drive occlusion device has been designed to implement brief (ca. 130 ms) inspiratory airway occlusion and to monitor the associated inspiratory occlusion pressure (P100) on a breath-to-breath basis in humans. The device, which has a low resistance when patent, provides no discernible modulation of ventilation during steady and nonsteady states of moderate intensity cycle-ergometer exercise. With this technique, it is possible to undertake investigations of dynamic as well as steady-state P100 responses to stimuli such as extensive, inhaled CO2, and hypoxia.

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