Biomedical subjects

P F Schoffelen

Publications and source records attributed to P F Schoffelen.

6 recordsLinked to original sources

PubMed1997

A dual-respiration chamber system with automated calibration.

This study characterizes respiration chambers with fully automated calibration. The system consists of two 14-m3 pull-type chambers. Care was taken to provide a friendly environment for the subjects, with the possibility of social contact during the experiment. Gas analysis was automated to correct for analyzer drift and barometric pressure variations and to provide ease of use. Methods used for checking the system's performance are described. The gas-analysis repeatability was within 0.002%. Results of alcohol combustion (50-350 ml/min CO2) show an accuracy of 0.5 +/- 2.0 (SD) % for O2 consumption and -0.3 +/- 1.6% for CO2 production for 2- to 24-h experiments. It is concluded that response time is not the main factor with respect to the smallest practical measurement interval (duration); volume, mixing, gas-analysis accuracy, and levels of O2 consumption and CO2 production are at least equally important. The smallest practical interval was 15-25 min, as also found with most chamber systems described in the literature. We chose to standardize 0.5 h as the minimum measurement interval.

Atmosphere Exposure Chambers↗

PubMed1990

The shape of the cumulative food intake curve in humans, during basic and manipulated meals.

The shape of the cumulative food intake curve of normal weight and obese women was studied during solid food lunches, artificially prolonged meals, and energetically enriched meals eaten in a laboratory setting. Subjects (86 normal weight, 50 obese) displayed consistent eating behaviour over 3-6 repeated meals, with marked differences between individuals. Aspects of eating behaviour were reflected in decelerated and nondecelerated (or linear) cumulative intake curves depending on changes or no changes in eating rate during the course of a meal, respectively. A change in eating rate was generally related to decrease in bite size, with bite rate remaining constant, from the third temporal quarter of the meal onwards, resulting in a decelerated cumulative intake curve. The nondecelerated (linear) cumulative intake curve does not show this change in eating rate: in the first three temporal quarters bite size and bite rate were constant, whereas in the fourth temporal quarter bite size decreased slightly, compensated by a small increase in bite rate. Intraindividual ranges for meal parameters such as chewing time per bite, bite interval and initial eating rate indicated consistency of individual eating behaviour. In manipulation experiments with a subset of 21 subjects in which meals were artificially prolonged by an interval of 8 min, the cumulative intake curves did not differ significantly from the original cumulative intake curves in 10 nondecelerated (linear) eaters, but showed a change towards nondecelerated curves in 8 out of 11 decelerated eaters.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

Effects of addition of exercise to energy restriction on 24-hour energy expenditure, sleeping metabolic rate and daily physical activity.

Body composition, sleeping metabolic rate (SMR), 24-h energy expenditure (24-EE) and daily physical activity were determined in 12 obese women during and after 12 weeks of exercise (4 h per week on 55 per cent of VO2 max) and/or energy restriction (2.9-3.5 MJ/d). Diet(D) and diet-exercise (DE) groups were formed by matching the subjects on their body mass index (BMI, kg/m2; mean 30.3). After 12 weeks no significant differences were shown in loss of weight (D 12.2 and DE 13.2 kg) and loss of fat mass (D 9.4 and DE 10.9 kg). Both groups reduced their SMR (D 29.9 per cent and DE 21.7 per cent) and their metabolic rate during the entire night measured by indirect calorimetry (12-EE) (D 36.4 per cent and DE 28.6 per cent; P less than 0.05). Energy expenditure over 24 h, estimated by means of heart-rate monitoring, was reduced by 22.1 per cent for D and by 19.6 per cent for DE (n.s.). Daily physical activity, which was determined during 5 d using an actometer, was increased after 12 weeks for DE (27 per cent; P less than 0.05) and D (10 per cent; n.s.). The suggestion that a reduction in normal activities of daily life in a diet-exercise group is the explanation for the absence of significant differences in weight and fat loss between a diet-exercise and a diet group is not confirmed in this study. Daily physical activity showed a significantly higher increase for the diet-exercise group than for the diet group, while the decline of SMR and 24-EE tended to be smaller.

Adult↗

PubMed1988

The work of walking: a calorimetric study.

Experiments were designed to test the traditional assumption that during level walking all of the energy from oxidation of fuel appears as heat and no work is done. Work is force expressed through distance, or energy transferred from a man to the environment, but not as heat. While wearing a suit calorimeter in a respiration chamber, five women and five men walked for 70 to 90 min on a level treadmill at 2.5, 4.6, and 6.7 km.h-1 and pedalled a cycle ergometer for 70 to 90 min against 53 and 92 W loads. They also walked with a weighted backpack and against a horizontal load. During cycling, energy from fuel matched heat loss plus the power measured by the ergometer. During walking, however, energy from fuel exceeded that which appeared as heat, meaning that work was done. The power increased with walking speed; values were 14, 29, and 63 W, which represented 11, 12, and 13% of the incremental cost of fuel above the resting level. Vertical and horizontal loads increased the fuel cost and heat loss of walking but did not alter the power output. This work energy did not re-appear as thermal energy during 18 h of recovery. The most likely explanation of the work done is in the inter-action between the foot and the ground, such as compressing the heel of the shoe and bending the sole. We conclude that work is done in level walking.

Adult↗

PubMed1987

Does exercise give an additional effect in weight reduction regimens?

The effects of dieting and exercise on RMR, body composition and maximal aerobic power were studied in 12 obese women. The subjects were paired on the basis of their body mass index and divided into a diet (D) and a diet + exercise group (DE). The treatment consisted of a 5-week period with a low-energy formula diet of 2.9 MJ and an 8-week period with a mixed diet of 1.7 MJ supplemented with 1.8 MJ normal foodstuffs. DE trained 4 h per week at 50-60 per cent of their maximal aerobic power with aerobics and fitness exercises. Body composition was determined by hydrostatic weighing and RMR was measured from 03.00 to 06.00 hours in a respiration chamber. Maximal aerobic power was measured on a continuously braked ergometer. The measurements were done at week 0, after 4 weeks (week 5), and after 12 weeks (week 13). Weight loss after 4 weeks was 8.2 kg (DE) and 7.9 kg (D) and after 12 weeks 13.2 kg (DE) and 12.2 kg (D). There were no significant differences between the groups. Fat loss was also not statistically different between DE (6.7 and 10.9 kg) and D (6.0 and 9.4 kg). Both groups showed a significant decrease in RMR per kilogram FFM after 12 weeks (DE: 18.2 per cent and D: 26.5 per cent). There was also a significant decrease in RMR for D (19.9 per cent) after 4 weeks but not for DE (12.2 per cent).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

Measurement of resting energy expenditure in patients with chronic obstructive pulmonary disease in a clinical setting.

There is a growing tendency to estimate energy requirements by means of the assessment of resting energy expenditure (REE) by indirect calorimetry. In this study a computerized open-circuit ventilated hood system is described that was constructed for assessing REE in a clinical setting. Measurement error of the device, tested by ethanol combustion was +2% for VO2 and VCO2 and less than 1% for respiratory quotient. To assess the within-patient variability of REE measurements performed in a daily clinical routine, we studied the following aspects of the measurements in several groups of patients with chronic obstructive pulmonary disease: (1) reproducibility, (2) the influence of routine physical activities before the measurement, (3) measurement duration, and (4) difference between measurements using a ventilated hood or a mouthpiece. Reproducibility of measurements with a 2-month interval in 12 weight-stable patients was good (1415 +/- 128 and 1398 +/- 138 kcal/day). Variations due to limited activities and different measurement durations (between 10 and 30 minutes) were not significant. Variations between measurements with a mouthpiece and ventilated hood were larger in patients than in healthy control subjects, but for both groups no systematic difference was established. REE can be assessed reliably by short-term measurements with a ventilated hood in stable chronic obstructive pulmonary disease patients on an outpatient basis, provided a short rest is taken before the measurement.

Aged↗