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.

Peripheral chemoreceptor function after carbonic anhydrase inhibition during moderate-intensity exercise

1999 ◽  
Vol 86 (5) ◽  
pp. 1544-1551 ◽  
Author(s):  
Barry W. Scheuermann ◽  
John M. Kowalchuk ◽  
Donald H. Paterson ◽  
David A. Cunningham
Keyword(s):  
Steady State ◽  
Carbonic Anhydrase ◽  
Ventilatory Threshold ◽  
Ventilatory Response ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Peripheral Chemoreceptor ◽  
Ventilatory Drive ◽  
Carbonic Anhydrase Inhibition ◽  
End Tidal

The effect of carbonic anhydrase inhibition with acetazolamide (Acz, 10 mg/kg) on the ventilatory response to an abrupt switch into hyperoxia (end-tidal [Formula: see text]= 450 Torr) and hypoxia (end-tidal[Formula: see text] = 50 Torr) was examined in five male subjects [30 ± 3 (SE) yr]. Subjects exercised at a work rate chosen to elicit an O2 uptake equivalent to 80% of the ventilatory threshold. Ventilation (V˙e) was measured breath by breath. Arterial oxyhemoglobin saturation (%[Formula: see text]) was determined by ear oximetry. After the switch into hyperoxia, V˙eremained unchanged from the steady-state exercise prehyperoxic value (60.6 ± 6.5 l/min) during Acz. During control studies (Con),V˙e decreased from the prehyperoxic value (52.4 ± 5.5 l/min) by ∼20% (V˙enadir = 42.4 ± 6.3 l/min) within 20 s after the switch into hyperoxia. V˙e increased during Acz and Con after the switch into hypoxia; the hypoxic ventilatory response was significantly lower after Acz compared with Con [Acz, change (Δ) inV˙e/[Formula: see text]= 1.54 ± 0.10 l ⋅ min−1 ⋅ [Formula: see text] −1; Con, ΔV˙e/[Formula: see text]= 2.22 ± 0.28 l ⋅ min−1 ⋅ [Formula: see text] −1]. The peripheral chemoreceptor contribution to the ventilatory drive after acute Acz-induced carbonic anhydrase inhibition is not apparent in the steady state of moderate-intensity exercise. However, Acz administration did not completely attenuate the peripheral chemoreceptor response to hypoxia.

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.

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.

scholarly journals Cardiac output during exercise by the open circuit acetylene washin method: comparison with direct Fick

2000 ◽  
Vol 88 (5) ◽  
pp. 1650-1658 ◽  
Author(s):  
B. D. Johnson ◽  
K. C. Beck ◽  
D. N. Proctor ◽  
J. Miller ◽  
N. M. Dietz ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Method Comparison ◽  
Arterial Oxygen Tension ◽  
Open Circuit ◽  
Peak Oxygen Consumption ◽  
Moderate Intensity ◽  
Arterial Oxygen ◽  
Computational Techniques ◽  
Moderate Intensity Exercise ◽  
End Tidal

An open-circuit (OpCirc) acetylene uptake cardiac output (Q˙t) method was modified for use during exercise. Two computational techniques were used. OpCirc1 was based on the integrated uptake vs. end-tidal change in acetylene, and OpCirc2 was based on an iterative finite difference modeling method. Six subjects [28–44 yr, peak oxygen consumption (V˙o 2) = 120% predicted] performed cycle ergometry exercise to compareQ˙t using OpCirc and direct Fick methods. An incremental protocol was repeated twice, separated by a 10-min rest, and subsequently subjects exercised at 85–90% of their peak work rate. Coefficient of variation of the OpCirc methods and Fick were highest at rest (OpCirc1, 7%, OpCirc2, 12%, Fick, 10%) but were lower at moderate to high exercise intensities (OpCirc1, 3%, OpCirc2, 3%, Fick, 5%). OpCirc1 and OpCirc2 Q˙t correlated highly with Fick Q˙t( R 2 = 0.90 and 0.89, respectively). There were minimal differences between OpCirc1 and OpCirc2 compared with Fick up to moderate-intensity exercise (<70% peakV˙o 2); however, both techniques tended to underestimate Fick at >70% peakV˙o 2. These differences became significant for OpCirc1 only. Part of the differences between Fick and OpCirc methods at the higher exercise intensities are likely related to inhomogeneities in ventilation and perfusion matching ( R 2 = 0.36 for Fick − OpCirc1 vs. alveolar-to-arterial oxygen tension difference). In conclusion, both OpCirc methods provided reproducible, reliable measurements ofQ˙t during mild to moderate exercise. However, only OpCirc2 appeared to approximate FickQ˙t at the higher work intensities.

scholarly journals The Effects of Transdermal Nicotine Patches on the Cardiorespiratory and Lactate Responses During Exercise from Light to Moderate Intensity: Implications for Exercise Prescription during Smoking Cessation

Medicina ◽  
2019 ◽  
Vol 55 (7) ◽  
pp. 348
Author(s):  
Takashi Nakagata ◽  
Kosuke Fukao ◽  
Hiroyuki Kobayashi ◽  
Shizuo Katamoto ◽  
Hisashi Naito
Keyword(s):  
Perceived Exertion ◽  
Peak Level ◽  
Random Order ◽  
Cycle Ergometer ◽  
Moderate Intensity ◽  
Nicotine Concentration ◽  
Nicotine Patches ◽  
Transdermal Nicotine ◽  
Study Results ◽  
Young Smokers

Background and objectives: Exercise can help ease withdrawal symptoms of smokers. However, there is little information about the physiological responses, such as cardiorespiratory and lactate (La) responses, during exercise from light to moderate intensity combined with transdermal nicotine patches (TNPs) in smokers. This study aimed to investigate the effect of TNPs on the cardiorespiratory and La responses during exercise at light to moderate intensity. Materials and Methods: Fourteen young men (8 non-smokers, 6 current smokers) aged 20 to 26 years participated in this study. They performed an incremental graded submaximal exercise test using an electromagnetic cycle ergometer set from 30 to 210 W with (TNP condition) or without a TNP (control condition) in a random order. The TNP was applied to the left arm 8–10 h prior to starting the exercise to achieve the peak level of blood nicotine concentration. Heart rate (HR), rate of perceived exertion (RPE), oxygen consumption (VO2), ventilation (VE), and blood La at rest and during exercise were measured and analyzed. Results: The HR at rest was significantly higher in the TNP condition than in the control condition (TNP; 74.7 ± 13.8 bpm, control; 65.3 ± 10.8 bpm, p < 0.001). There was no interaction (condition × exercise intensity) between any of the variables, and VO2, VE, RPE, and La during exercise were not significantly different between the conditions. However, HR during exercise was 6.7 bpm higher on average in the TNP condition. Conclusions: The HR during exercise was greater at light to moderate intensity with a TNP. Our study results will guide clinicians or health professionals when prescribing exercise programs combined with TNPs for healthy young smokers.

scholarly journals Moderate intensity exercise in hypoxia increases IGF-1 bioavailability and serum irisin in individuals with type 1 diabetes

2020 ◽  
Vol 11 ◽  
pp. 204201882092532 ◽  
Author(s):  
Aleksandra Żebrowska ◽  
Marcin Sikora ◽  
Anna Konarska ◽  
Anna Zwierzchowska ◽  
Tomasz Kamiński ◽  
...  
Keyword(s):  
Type 1 Diabetes ◽  
Serum Levels ◽  
Cycle Ergometer ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Physiological Variables ◽  
Hypoxic Conditions ◽  
Study Results ◽  
Glycaemia Control

Aim: This study aimed to determine the effect of moderate intensity continuous exercise (Ex) and hypoxia (Hyp) on serum brain-derived neurotrophic factor (BDNF), insulin-like growth factor-1 (IGF-1) and its binding protein-3 (IGFBP-3), irisin and cytokines levels in patients with type 1 diabetes (T1D). Methods: A total of 14 individuals with T1D (age: 28.7 ± 7.3 years) and 14 healthy adults (age: 27.1 ± 3.9 years) performed 40-min continuous Ex at moderate intensity (50% lactate threshold) on a cycle ergometer in normoxia (Nor) and Hyp (FiO2 = 15.1%) Biochemical factors, glucose concentrations and physiological variables were measured at rest, immediately and up to 24 h after both Ex protocols. Results: Patients with T1D had significantly lower pre-Ex serum concentrations of BDNF ( p < 0.05, p < 0.01), and total IGF-1 ( p < 0.001, p < 0.05) and significantly higher irisin levels ( p < 0.05, p < 0.01) in Nor and Hyp, compared with healthy subjects. Ex significantly increased in T1D group serum BDNF (in Nor only p < 0.05) and total IGF-1 levels in Nor and Hyp ( p < 0.001 and p < 0.01, respectively). Immediately after Ex in Hyp, freeIGF-1 ( p < 0.05) and irisin levels ( p < 0.001) were significantly higher compared with the levels induced by Ex alone. Free IGF-1 and irisin serum levels remained elevated in 24 h post-Ex in Hyp. In T1D, significant blood glucose (BG) decrease was observed immediately after Ex in Hyp ( p < 0.001) and in 24 h recovery ( p < 0.001) compared with pre-Ex level. Conclusion: The study results suggest that moderate intensity continuous Ex has beneficial effect on BDNF and IGF-1 levels. Ex in hypoxic conditions may be more effective in increasing availability of IGF-1. The alterations in the post-Ex irisin levels and IGF-1 system may be contributing to more effective glycaemia control in patients with T1D.

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