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Oxygen Cost (oxygen + cost)

Distribution by Scientific Domains

Medical Sciences	57%
Life Sciences	42%

Selected Abstracts

Oxygen cost of ventilation during incremental exercise to VO2 max

RESPIROLOGY, Issue 2 2006
Chantal A. VELLA
Objective: Evidence of significant oxygen requirements for ventilation during exercise (exercise hyperpnoea) prompted the investigation into whether the oxygen cost of ventilation affects the presence of a whole-body VO2 plateau at maximal exercise. The purposes of this study were to: (i) use isocapnic hyperpnoea trials to determine the oxygen cost of ventilation (VO2VENT) across a range of ventilation (VE); (ii) determine the mean VO2VENT at maximal exercise expressed as a percentage of whole-body VO2 max; and (iii) determine if a plateau in VO2 is more evident when the VO2VENT is subtracted from whole-body VO2 at maximal exercise. Methods: A total of 21 subjects performed a VO2 max test on the cycle ergometer to determine the range of VE for each subject. From the initial VO2 max test, nine VE values across the range of VE were selected for each subject and the oxygen cost of each was measured. Results: The mean maximal VO2VENT equalled 8.8 ± 3.3% of VO2 max and ranged from 5.0% to 17.6%. VO2VENT increased exponentially with increasing VE, but there was considerable subject variability in the oxygen cost per litre of VE as VE increased. Subtracting the VO2VENT from whole-body VO2 at maximal exercise increased the detection of a plateau in VO2 at VO2 max. Conclusions: The data of the present study indicate that the VO2VENT is a significant portion of VO2 max and may be a limiting factor of maximal exercise performance in some subjects. [source]

Impaired oxygen kinetics in beta-thalassaemia major patients

ACTA PHYSIOLOGICA, Issue 3 2009
I. Vasileiadis
Abstract Aim:, Beta-thalassaemia major (TM) affects oxygen flow and utilization and reduces patients' exercise capacity. The aim of this study was to assess phase I and phase II oxygen kinetics during submaximal exercise test in thalassaemics and make possible considerations about the pathophysiology of the energy-producing mechanisms and their expected exercise limitation. Methods:, Twelve TM patients with no clinical evidence of cardiac or respiratory disease and 10 healthy subjects performed incremental, symptom-limited cardiopulmonary exercise testing (CPET) and submaximal, constant workload CPET. Oxygen uptake (Vo2), carbon dioxide output and ventilation were measured breath-by-breath. Results:, Peak Vo2 was reduced in TM patients (22.3 ± 7.4 vs. 28.8 ± 4.8 mL kg,1 min,1, P < 0.05) as was anaerobic threshold (13.1 ± 2.7 vs. 17.4 ± 2.6 mL kg,1 min,1, P = 0.002). There was no difference in oxygen cost of work at peak exercise (11.7 ± 1.9 vs. 12.6 ± 1.9 mL min,1 W,1 for patients and controls respectively, P = ns). Phase I duration was similar in TM patients and controls (24.6 ± 7.3 vs. 23.3 ± 6.6 s respectively, P = ns) whereas phase II time constant in patients was significantly prolonged (42.8 ± 12.0 vs. 32.0 ± 9.8 s, P < 0.05). Conclusion:, TM patients present prolonged phase II on-transient oxygen kinetics during submaximal, constant workload exercise, compared with healthy controls, possibly suggesting a slower rate of high energy phosphate production and utilization and reduced oxidative capacity of myocytes; the latter could also account for their significantly limited exercise tolerance. [source]

Dietary nitrate lowers oxygen cost during exercise

ACTA PHYSIOLOGICA, Issue 1 2007
Jan Henriksson
No abstract is available for this article. [source]

Energy efficiency in gait, activity, participation, and health status in children with cerebral palsy

DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 3 2008
Claire Kerr BSc (Hons) Physio PhD
The aim of the study was to establish if a relationship exists between the energy efficiency of gait, and measures of activity limitation, participation restriction, and health status in a representative sample of children with cerebral palsy (CP). Secondary aims were to investigate potential differences between clinical subtypes and gross motor classification, and to explore other relationships between the measures under investigation. A longitudinal study of a representative sample of 184 children with ambulant CP was conducted (112 males, 72 females; 94 had unilateral spastic C P, 84 had bilateral spastic C P, and six had non-spastic forms; age range 4-17y; Gross Motor Function Classification System Level I, n=57; Level II, n=91; Level III, n=22; and Level IV, n=14); energy efficiency (oxygen cost) during gait, activity limitation, participation restriction, and health status were recorded. Energy efficiency during gait was shown to correlate significantly with activity limitations; no relationship between energy efficiency during gait was found with either participation restriction or health status. With the exception of psychosocial health, all other measures showed significant differences by clinical subtype and gross motor classification. The energy efficiency of walking is not reflective of participation restriction or health status. Thus, therapies leading to improved energy efficiency may not necessarily lead to improved participation or general health. [source]

Oxygen cost of ventilation during incremental exercise to VO2 max

Physical training and testing in patients with chronic obstructive pulmonary disease

THE CLINICAL RESPIRATORY JOURNAL, Issue 1 2007
Ragnheiður Harpa Arnardóttir
Abstract Introduction:, The effects of different training modes need to be investigated further in patients with chronic obstructive pulmonary disease (COPD). Both advanced laboratory tests and field tests are used in patients with COPD to evaluate effects of interventions such as pulmonary rehabilitation. Aims:, The overall aims of the studies were to investigate the effects of different training modalities on exercise capacity and on health-related quality of life (HRQoL) in patients with moderate or severe COPD and, further, to explore two of the physical field tests used in pulmonary rehabilitation, the 12-min walk test and the incremental shuttle walking test (ISWT). Materials and Methods:, Patients with moderate or severe COPD were included. In study I (n = 57), the 12-min walk test was performed three times within 1 week. Exercise-induced hypoxemia (EIH) was assessed by pulse oximeter and was defined as SpO2 < 90%. In study II (n = 93), performance on ISWT was compared to performance on two different cycle tests. In study III (n = 42), the effects of two different combination training programmes were compared when training twice a week for 8 weeks. One programme was mainly based on endurance training (group A), and the other was based on resistance training and on callisthenics (group B). In study IV (n = 60), endurance training with interval resistance was compared to endurance training with continuous resistance. Results:, In study I, the 12-min walking distance (12MWD) did not increase on retesting in patients with EIH, but increased significantly on retesting in the non-EIH patients. In study II, the ISWT was as good a predictor of peak exercise capacity (W peak) as peak oxygen uptake (VO2 peak) was. In study III, W peak and 12MWD increased in group A but not in group B. HRQoL, anxiety and depression were unchanged in both groups. Ratings of perceived exertion at rest were significantly lower in group A than in group B after training and during 12 months of follow-up. Twelve months post training, 12MWD was back to baseline in group A, but was significantly shorter than at baseline in group B. Patients with moderate and severe COPD responded to training in the same way. In study IV, both interval and continuous endurance training increased W peak, VO2 peak, peak exhaled carbon dioxide (VCO2 peak) and 12MWD. Likewise, HRQoL, dyspnoea during activities of daily life, anxiety and depression improved similarly in both groups. At a fixed, sub-maximal workload (isotime), the interval training reduced oxygen cost and ventilatory demand significantly more than the continuous training did. Conclusions:, EIH affects the retest effects on 12MWD. W peak can be predicted from an ISWT similarly well as from VO2 peak. A short training programme can improve W peak and 12MWD when based mainly on endurance training. Both patients with moderate and severe COPD respond to training in the same way. A short endurance training intervention can possibly delay decline in 12MWD for 1 year. Both interval and continuous endurance training improves physical performance and HRQoL. Interval training lowers the energy cost of sub-maximal work more than continuous training does. [source]

Endurance exercise performance: the physiology of champions

THE JOURNAL OF PHYSIOLOGY, Issue 1 2008
Michael J. Joyner
Efforts to understand human physiology through the study of champion athletes and record performances have been ongoing for about a century. For endurance sports three main factors , maximal oxygen consumption , the so-called ,lactate threshold' and efficiency (i.e. the oxygen cost to generate a give running speed or cycling power output) , appear to play key roles in endurance performance. and lactate threshold interact to determine the ,performance , which is the oxygen consumption that can be sustained for a given period of time. Efficiency interacts with the performance to establish the speed or power that can be generated at this oxygen consumption. This review focuses on what is currently known about how these factors interact, their utility as predictors of elite performance, and areas where there is relatively less information to guide current thinking. In this context, definitive ideas about the physiological determinants of running and cycling efficiency is relatively lacking in comparison with and the lactate threshold, and there is surprisingly limited and clear information about the genetic factors that might pre-dispose for elite performance. It should also be cautioned that complex motivational and sociological factors also play important roles in who does or does not become a champion and these factors go far beyond simple physiological explanations. Therefore, the performance of elite athletes is likely to defy the types of easy explanations sought by scientific reductionism and remain an important puzzle for those interested in physiological integration well into the future. [source]