scholarly journals Variations in exercise ventilation in hypoxia will affect oxygen uptake

2020 ◽  
Vol 107 (3) ◽  
pp. 431-443
Author(s):  
J.A. Loeppky ◽  
R.M. Salgado ◽  
A.C. Sheard ◽  
D.O. Kuethe ◽  
C.M. Mermier
Keyword(s):  
Individual Variation ◽  
Ambient Pressure ◽  
Work Of Breathing ◽  
Linear Equations ◽  
Mechanical Efficiency ◽  
Individual Response ◽  
Hypoxic Ventilatory Response ◽  
Gross Efficiency ◽  
Exercise Ventilation ◽  
Progressive Exercise

AbstractReports of VO2 response differences between normoxia and hypoxia during incremental exercise do not agree. In this study VO2 and VE were obtained from 15-s averages at identical work rates during continuous incremental cycle exercise in 8 subjects under ambient pressure (633 mmHg ≈1,600 m) and during duplicate tests in acute hypobaric hypoxia (455 mmHg ≈4,350 m), ranging from 49 to 100% of VO2 peak in hypoxia and 42–87% of VO2 peak in normoxia. The average VO2 was 96 mL/min (619 mL) lower at 455 mmHg (n.s. P = 0.15) during ramp exercises. Individual response points were better described by polynomial than linear equations (mL/min/W). The VE was greater in hypoxia, with marked individual variation in the differences which correlated significantly and directly with the VO2 difference between 455 mmHg and 633 mmHg (P = 0.002), likely related to work of breathing (Wb). The greater VE at 455 mmHg resulted from a greater breathing frequency. When a subject's hypoxic ventilatory response is high, the extra work of breathing reduces mechanical efficiency (E). Mean ∆E calculated from individual linear slopes was 27.7 and 30.3% at 633 and 455 mmHg, respectively (n.s.). Gross efficiency (GE) calculated from mean VO2 and work rate and correcting for Wb from a VE–VO2 relationship reported previously, gave corresponding values of 20.6 and 21.8 (P = 0.05). Individual variation in VE among individuals overshadows average trends, as also apparent from other reports comparing hypoxia and normoxia during progressive exercise and must be considered in such studies.

scholarly journals Respiratory energetics during exercise at high altitude

1999 ◽  
Vol 86 (6) ◽  
pp. 1785-1792 ◽  
Author(s):  
Fabio Cibella ◽  
Giuseppina Cuttitta ◽  
Salvatore Romano ◽  
Bruno Grassi ◽  
Giovanni Bonsignore ◽  
...  
Keyword(s):  
High Altitude ◽  
Minute Ventilation ◽  
Work Of Breathing ◽  
Normal Subjects ◽  
Mechanical Efficiency ◽  
Esophageal Pressure ◽  
Work Capacity ◽  
External Work ◽  
Exercise Ventilation ◽  
The Relationship

The purpose of this study was to assess the effect of high altitude (HA) on work of breathing and external work capacity. On the basis of simultaneous records of esophageal pressure and lung volume, the mechanical power of breathing (W˙rs) was measured in four normal subjects during exercise at sea level (SL) and after a 1-mo sojourn at 5,050 m. Maximal exercise ventilation (V˙e max) and maximal W˙rs were higher at HA than at SL (mean 185 vs. 101 l/min and 129 vs. 40 cal/min, respectively), whereas maximal O2 uptake averaged 2.07 and 3.03 l/min, respectively. In three subjects, the relationship ofW˙rs to minute ventilation (V˙e) was the same at SL and HA, whereas, in one individual, W˙rs for any givenV˙e was consistently lower at HA. Assuming a mechanical efficiency (E) of 5%, the O2 cost of breathing at HA and SL should amount to 26 and 5.5% of maximal O2 uptake, whereas for E of 20% the corresponding values were 6.5 and 1.4%, respectively. Thus, at HA, W˙rs may substantially limit external work unless E is high. Although at SLV˙e max did not exceed the critical V˙e, at which any increase inV˙e is not useful in terms of body energetics even for E of 5%, at HAV˙e maxexceeded critical V˙e even for E of 20%.

Diaphragmatic work of breathing in premature human infants

1987 ◽  
Vol 62 (4) ◽  
pp. 1410-1415 ◽  
Author(s):  
B. G. Guslits ◽  
S. E. Gaston ◽  
M. H. Bryan ◽  
S. J. England ◽  
A. C. Bryan
Keyword(s):  
Lung Disease ◽  
Preterm Infants ◽  
Work Of Breathing ◽  
Mechanical Efficiency ◽  
Strongly Correlated ◽  
Intercostal Muscle ◽  
Human Infants ◽  
Transdiaphragmatic Pressure ◽  
Rib Cage ◽  
Inspiratory Work

Present methods of assessing the work of breathing in human infants do not account for the added load when intercostal muscle activity is lost and rib cage distortion occurs. We have developed a technique for assessing diaphragmatic work in this circumstance utilizing measurements of transdiaphragmatic pressure and abdominal volume displacement. Eleven preterm infants without evidence of lung disease were studied. During periods of minimal rib cage distortion, inspiratory diaphragmatic work averaged 5.9 g X cm X ml-1, increasing to an average of 12.4 g X cm X ml-1 with periods of paradoxical rib cage motion (P less than 0.01). Inspiratory work was strongly correlated with the electrical activity of the diaphragm as measured from its moving time average (P less than 0.05). Assuming a mechanical efficiency of 4% in these infants, the caloric cost of diaphragmatic work may reach 10% of their basal metabolic rate in periods with rib cage distortion. When lung disease is superimposed, the increased metabolic demands of the diaphragm may predispose preterm infants to fatigue and may contribute to a failure to grow.

Cycling Efficiency and Performance Following Short-Term Training Using Uncoupled Cranks

2009 ◽  
Vol 4 (1) ◽  
pp. 18-28 ◽  
Author(s):  
Andrew D. Williams ◽  
Isaac Selva Raj ◽  
Kristie L. Stucas ◽  
James W. Fell ◽  
Diana Dickenson ◽  
...  
Keyword(s):  
Lactate Threshold ◽  
Performance Enhancement ◽  
Average Power ◽  
Time Trial ◽  
Mechanical Efficiency ◽  
Cycling Performance ◽  
Peak Power Output ◽  
Gross Efficiency ◽  
And Performance ◽  
Study Participants

Objectives:Uncoupled cycling cranks are designed to remove the ability of one leg to assist the other during the cycling action. It has been suggested that training with this type of crank can increase mechanical efficiency. However, whether these improvements can confer performance enhancement in already well-trained cyclists has not been reported.Method:Fourteen well-trained cyclists (13 males, 1 female; 32.4 ± 8.8 y; 74.5 ± 10.3 kg; Vo2max 60.6 ± 5.5 mL·kg−1·min−1; mean ± SD) participated in this study. Participants were randomized to training on a stationary bicycle using either an uncoupled (n = 7) or traditional crank (n = 7) system. Training involved 1-h sessions, 3 days per week for 6 weeks, and at a heart rate equivalent to 70% of peak power output (PPO) substituted into the training schedule in place of other training. Vo2max, lactate threshold, gross efficiency, and cycling performance were measured before and following the training intervention. Pre- and post testing was conducted using traditional cranks.Results:No differences were observed between the groups for changes in Vo2max, lactate threshold, gross efficiency, or average power maintained during a 30-minute time trial.Conclusion:Our results indicate that 6 weeks (18 sessions) of training using an uncoupled crank system does not result in changes in any physiological or performance measures in well-trained cyclists.

Economic potential of individual variation in milk yield response to concentrate intake of dairy cows

2010 ◽  
Vol 148 (3) ◽  
pp. 263-276 ◽  
Author(s):  
G. ANDRÉ ◽  
P. B. M. BERENTSEN ◽  
G. VAN DUINKERKEN ◽  
B. ENGEL ◽  
A. G. J. M. OUDE LANSINK
Keyword(s):  
Observational Study ◽  
Milk Yield ◽  
Individual Variation ◽  
Study Data ◽  
Yield Response ◽  
Individual Response ◽  
Early Lactation ◽  
The Individual ◽  
Daily Milk Yield ◽  
Daily Milk

SUMMARYThe objectives of the current study were to quantify the individual variation in daily milk yield response to concentrate intake during early lactation and to assess the economic prospects of exploiting the individual variation in milk yield response to concentrate intake. In an observational study, data from 299 cows on four farms in the first 3 weeks of the lactation were collected. Individual response in daily milk yield to concentrate intake was analysed by a random coefficient model. Marked variation in individual milk yield response to concentrate intake was found on all four farms. An economic simulation was carried out, based on the estimated parameter values in the observational study. Individual optimization of concentrate supply is compared with conventional strategies for concentrate supply based on averaged population response parameters. Applying individual economic optimal settings for concentrate supply during early lactation, potential economic gain ranges from €0·20 to €2·03/cow/day.

THE OXYGEN COST OF BREATHING IN THE PREMATURE INFANT

PEDIATRICS ◽  
1966 ◽  
Vol 37 (6) ◽  
pp. 954-959
Author(s):  
Donald W. Thibeault ◽  
Bella Clutario ◽  
Peter A. M. Auld
Keyword(s):  
Premature Infant ◽  
Premature Infants ◽  
Work Of Breathing ◽  
Mechanical Efficiency ◽  
Oxygen Cost ◽  
Sources Of Error ◽  
Quantitative Results ◽  
The Absolute ◽  
Normal Adults

Work of breathing, oxygen cost of breathing, and calculated mechanical efficiency were studied in normal prematures using the plethysmograph method. The results indicate that the oxygen cost of breathing in these subjects averaged 0.9 ml per 500 ml ventilated. Calculated mechanical efficiency averaged 4.1%. These results were compared with those reported for normal adults, and premature infants were shown to have a higher oxygen cost of breathing and a lower mechanical efficiency. The sources of error of the method are discussed and emphasis is given to the fact that the absolute quantitative results may not be exact.

Mechanical work of breathing during muscular exercise

1960 ◽  
Vol 15 (3) ◽  
pp. 354-358 ◽  
Author(s):  
R. Margaria ◽  
G. Milic-Emili ◽  
J. M. Petit ◽  
G. Cavagna
Keyword(s):  
Energy Cost ◽  
Work Of Breathing ◽  
Pulmonary Ventilation ◽  
Respiratory Muscles ◽  
Mechanical Efficiency ◽  
Mechanical Work ◽  
Muscular Exercise ◽  
Additional Energy ◽  
External Work ◽  
Small Magnitude

The mechanical work of breathing was measured during muscular exercise on three normal subjects from simultaneous records of intra-esophageal pressure and tidal volume. At the maximal values of ventilation attained during exercise, the mechanical work of breathing amounts to about 100–120 cal/min. The maximum pulmonary ventilation useful for external work is attained when the energy cost of breathing due to any additional unit of air ventilated (dWre/dV) equals the additional energy provided by the same change in ventilation (dWtot/ dV), i.e. when dWre/dV = dWtot/dV. The maximal values of ventilation obtained experimentally during muscular exercise are in good agreement with that assumption, if the mechanical efficiency of the respiratory muscles is taken as 0.25. This implies that the mechanical efficiency of the respiratory muscles is the same as that of the muscles involved in performing useful external work. The work of breathing is of relatively small magnitude: during exercise the work of a breathing cycle amounts, at maximum, to 8% of the maximum potential work of breathing, calculated from the pressure-volume diagram of the respiratory apparatus, and the energy cost of respiration represents no more than 3% of the total energy consumed by the subject. Submitted on May 21, 1959

Breathing pattern during maximal exercise and during submaximal exercise with hypercapnia

1987 ◽  
Vol 63 (1) ◽  
pp. 238-244 ◽  
Author(s):  
C. G. Gallagher ◽  
E. Brown ◽  
M. Younes
Keyword(s):  
Tidal Volume ◽  
Respiratory System ◽  
Breathing Pattern ◽  
Maximal Exercise ◽  
Submaximal Exercise ◽  
Incremental Exercise ◽  
Exercise Ventilation ◽  
Significant Difference ◽  
Progressive Exercise ◽  
Very High

During progressive exercise ventilation (VI) initially increases through increases in both tidal volume (VT) and respiratory frequency (f) but at high levels of exercise further increases in VI are almost completely due to increases in f and a VT plateau is seen. We wished to determine whether the presence of the VT plateau is due to a tachypneic influence related to very high levels of exercise or whether it represents a stereotypic response of the respiratory system at high levels of VI. We therefore compared breathing pattern in six subjects during maximal incremental exercise (ME) with that in the same subjects when similar levels of VI were obtained by a combination of submaximal exercise and hypercapnia (E/CO2). A VT plateau was seen in all ME and E/CO2 tests. There was no significant difference in the level of the VT plateau between the ME (2.93 +/- 0.17 liters) and E/CO2 (2.97 +/- 0.12 liters) tests. We conclude that the presence and level of the VT plateau during ME is not due to a tachypneic stimulus related to very high levels of exercise but is a function of the level of VI.

scholarly journals Plasma Melatonin and Progesterone Profiles of Suffolk and Romney Marsh Ewes Implanted with Melatonin during Anoestrus Season at Lower Latitudes in Southern Hemisphere

2018 ◽  
Vol 44 (1) ◽  
pp. 8
Author(s):  
Aya Sasa ◽  
Paula Almeida Rodrigues ◽  
Keico Okino Nonaka ◽  
Julio César de Carvalho Balieiro ◽  
Lia Alencar Coelho
Keyword(s):  
Individual Variation ◽  
Southeastern Brazil ◽  
Individual Response ◽  
Light Phase ◽  
Melatonin Treatment ◽  
Plasma Progesterone ◽  
Blood Samples ◽  
Mean Values ◽  
Positive Effects ◽  
Plasma Melatonin

Background: The subcutaneous implants of melatonin are stimulatory and mimic the positive effects of short photoperiod on reproduction in small ruminants. This study investigated the daily plasma melatonin profiles in ewes treated with melatonin implants and kept under natural photoperiod in Southeastern Brazil. The plasma progesterone concentrations were also investigated before and after melatonin implantation.Materials, Methods & Results: Romney Marsh (n = 11) and Suffolk (n = 10) ewes, which had been isolated from rams for at least 2 months prior to the beginning of the trial, were randomly allocated in two groups based on melatonin implant treatment (with or without melatonin implant). For plasma melatonin concentration, 43 days after melatonin implantation and 3 days before the ram introduction blood samples were collected every 2 hours during 24 hours. For plasma progesterone concentrations, blood samples were collected every once to twice a week for 2 different periods: prior to melatonin implantation and 46 days after the melatonin implantation and at the same day of the introduction of rams. The hormonal concentrations were determined by the radioimmunoassay method (RIA). The data were analyzed according to MIXED procedure (SAS) as repeated measurements for random animal effects. The effect of melatonin treatment on plasma melatonin 24-h period varied according to the breed. At the dark-phase, there were no plasma melatonin differences (P > 0.05) between implanted and no-implanted (228.02 ± 58.39 vs. 169.59 ± 48.39) Romney Marsh ewes whereas for Suffolk ewes the plasma melatonin levels were higher in implanted (305.61 ± 68.39 pg/mL) than no-implanted (151.26 ± 38.35 pg/mL) ones. At the light-phase, melatonin treatment effects could be evidenced and these differences (P < 0.01) consisted of higher melatonin values for implanted ewes and basal values for no-implanted ones in both breed groups. Before the melatonin implantation, the plasma progesterone levels were ˂ 1 ng/mL for Romney Marsh (0.41 ± 0.02 ng/mL) and Suffolk (0.47 ± 0.02 ng/mL) ewes. During the ram introduction period, no melatonin treatment effect was observed on plasma progesterone concentrations in both breed groups, but 2 days after ram introduction the plasma progesterone concentrations increased the mean values > than 1 ng/mL in implanted and no-implanted Suffolk ewes. In implanted Romney Marsh ewes the elevation of progesterone mean values was weak whereas in no-implanted Romney Marsh ewes the progesterone levels were maintained ˂ 1 ng/mL during all the blood sample collection times.Discussion: The melatonin treatment also produced a similar model of daily melatonin levels as reported previously by others, which is characterized by high plasma melatonin concentrations during the light phase of the day. The effect of melatonin implants on plasma melatonin profiles interacted with breed confirming an individual response to melatonin implantation which is proportional to genetic individual variation pattern of melatonin secretion. Before the melatonin implantation all Romney Marsh and Suffolk ewes were judged to be in non-ovulatory period (anoestrus) with plasma progesterone mean values lower than 1 ng/mL. The melatonin treatment helped to induce the ovulatory activity in most of the ewes that were in anestrous at the time of melatonin implantation and the efficacy of this treatment depends on the individual variation in ovulatory response to ram introduction. In Southeastern Brazil., melatonin implant altered the daily plasma melatonin profiles of Suffolk and Romney Marsh ewes by increasing the melatonin levels during the light-phase of the day. Melatonin implant also induced an ovulatory response in Suffolk and Romney Marsh after the introduction of the rams. For no-implanted Suffolk ewes, the male effect is sufficient to provoke an ovulatory response.

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