In sport science and physiology, exercise performance tests are frequently used to examine the in... more In sport science and physiology, exercise performance tests are frequently used to examine the influence of experimental interventions on endurance performance. The reliability (or reproducibility) of performance of a test refers to the consistency or reproducibility of performance when someone performs the test repeatedly. The reliability of time-to-exhaustion and time-trial performance test protocols has not been studied extensively. To date, the studies of Jeukendrup et al (cyling) and Laursen et al. (running) are the only studies that directly compared the reliability of TTE versus TT exercise tests. The reliability of TTE versus TT in healthy untrained subjects needs to be studied since athletic status, exercise intensity and duration are factors that affect the reliability of performance tests. Therefore, the purpose of this study was 1) to evaluate the reproducibility of comparable TT and TTE tests in healthy untrained male subjects; and 2) to evaluate the performance (time t...
Introduction: In cardiopulmonary rehabilitation programs (CPR), constant-load cycle endurance tes... more Introduction: In cardiopulmonary rehabilitation programs (CPR), constant-load cycle endurance tests (CLET) protocols are used to evaluate the response to specific interventions. In healthy subjects CLET protocols show a much lower reproducibility than time trial test (TTT) protocols. The purpose of this study was to evaluate the reproducibility of the CLET protocol and TTT protocol on a cycle ergometer in patients with COPD. Methods: In 20 patients with COPD (GOLD II-IV, FEV1 of 56±15%) exercise performance was measured. Patients were randomly allocated to a CLET protocol or TTT protocol. Patients performed the test protocol to which they were assigned, five times. Patients in the CLET group exercised to exhaustion at 120% of the actual individual training workload attained in the during CPR training sessions. Patients in the TTT group were asked to perform a certain amount of work (120% * Wtraining * 420) as fast as possible. Results: TTT protocol showed a significantly lower coeff...
Dit overzichtsartikel beschrijft de huidige stand van zaken in de wetenschap omtrent de verklarin... more Dit overzichtsartikel beschrijft de huidige stand van zaken in de wetenschap omtrent de verklaring voor het optreden van het verschijnsel Spierkramp. Nieuwe inzichten gecombineerd met bestaande ervaringen geven aan dat met name spiervermoeidheid een belangrijke factor is in het optreden van spierkramp. Aansturing vanuit het zenuwstelsel kan hiermee verstoord zijn en leiden tot ongecontroleerde samentrekking.
Journal of cardiopulmonary rehabilitation and prevention, 2017
The primary aims of this study were (1) to evaluate whole-body mechanical efficiency (ME) in a la... more The primary aims of this study were (1) to evaluate whole-body mechanical efficiency (ME) in a large group of chronic obstructive pulmonary disease (COPD) patients with a wide range of degrees of illness and (2) to examine how ME in COPD is related to absolute work rate and indices of disease severity during exercise testing. A total of 569 patients (301 male patients; GOLD stage I: 28, GOLD stage II: 166, GOLD stage III: 265, and GOLD stage IV: 110) with chronic obstructive pulmonary disease (COPD) were included in the data analysis. Individual maximal workload (watt), peak minute ventilation ((Equation is included in full-text article.)E, L/min body temperature and pressure, saturated), and peak oxygen uptake ((Equation is included in full-text article.)O2, mL/min standard temperature and pressure, dry) were determined from a maximal incremental cycle ergometer test. Ventilatory and metabolic response parameters were collected during a constant work rate test at 75% of the individ...
Voor veel mensen is afvallen een belangrijke reden om zich lichamelijk in te spannen. Ook op sc... more Voor veel mensen is afvallen een belangrijke reden om zich lichamelijk in te spannen. Ook op scholen wordt er soms aandacht besteed aan de relatie tussen (over)gewicht en inspanning. Maar hoeveel energie verbruik je nu eigenlijk tijdens inspanning? En hoeveel vet verbrand je daarmee?
The sympathetic nervous system is involved in the control of energy metabolism and expenditure. D... more The sympathetic nervous system is involved in the control of energy metabolism and expenditure. Diet-induced thermogenesis is mediated partly by the ß-adrenergic component of this system. The aim of the present study was to investigate the role of genetic variation in the ß2-adrenoceptor in diet-induced thermogenesis. Data from twenty-four subjects (fourteen men and ten women; BMI 26·7(sem 0·8) kg/m2; age 45·2(sem1·4) years) with different polymorphisms of the ß2-adrenoceptor at codon 16 (Gly16Gly, Gly16Arg or Arg16Arg) were recruited for this study. Subjects were given a high-carbohydrate liquid meal, and the energy expenditure, respiratory exchange ratio, and plasma concentrations of NEFA, glycerol, glucose, insulin and catecholamines were measured before and over 4 h after the meal. The AUC of energy expenditure (diet-induced thermogenesis) was not significantly different between polymorphism groups, nor was the response of any of the other measured variables to the meal. In a mu...
Background: The aim of the present study was to establish whether polymorphisms, especially those... more Background: The aim of the present study was to establish whether polymorphisms, especially those within the promoter region, of the β 2-adrenoceptor gene (ADRB2) influence β 2-adrenoceptor expression in human lung. Methods: The density of β-adrenoceptors in human lung tissue (n=88) was determined by saturation binding using the radioligand, iodinated cyanopindolol. Discrimination of β 1-and β 2-adrenoceptors was determined using the highly selective β 1-adrenoceptor antagonist, CGP20712A. Genotype was determined at 5 positions of ADRB2 previously reported as polymorphic. Potential influences of single nucleotide polymorphisms (SNPs) within the promoter region (-367,-47) and coding block (46, 79, 491) of ADRB2 on β 2-adrenoceptor expression were investigated. Results: The density of β 2-adrenoceptors was variable among the 88 lung preparations studied ranging from 17 to 177 fmol/mg protein (mean±S.E.M., 72±4 fmol/mg protein). There was no influence of genotype on β 2-adrenoceptor expression for any of the polymorphisms studied except at position 491. The polymorphism at position 491C>T, leading to a change from thr to ile at amino acid 164, is uncommon. Preparations genotyped as heterozygous (126±15 fmol/mg protein; n=5) expressed significantly (P = 0.0005) higher levels of β 2-adrenoceptor than those that were homozygous (69±4 fmol/mg protein; n=83).
The Journal of Clinical Endocrinology & Metabolism, 2005
The -adrenergic system is involved in the control of energy metabolism and expenditure. The  2-... more The -adrenergic system is involved in the control of energy metabolism and expenditure. The  2-adrenergic receptor ( 2-AR) gene shows polymorphisms that have been associated with obesity in several studies. In vitro and in vivo studies suggest differences in  2-AR-mediated function between these polymorphisms. The aim of this study was to investigate the influence of genetic variation in codon 16 of the  2-AR gene on energy metabolism in humans. Thirty-four subjects were recruited [Gly16Gly (n ؍ 13), Gly16Arg (n ؍ 16), or Arg16Arg (n ؍ 5)]. The  2-AR was stimulated with two doses of salbutamol (50 and 100 ng/kg fat-free mass per minute) after blockade of the  1-adrenergic receptors with atenolol. Energy expenditure and plasma substrate and hormone concentrations were measured. The increase in energy expenditure (⌬EE) was significantly different among groups in which the Arg16Arg group showed the lowest increase (P < 0.05 vs. Gly carriers). In a multiple regression model, variations in the increase in nonesterified fatty acid concentration during salbutamol infusion (partial r ؍ 0.51) and the polymorphism contributed significantly to the variation in ⌬EE. Thirty-five percent of the variation in ⌬EE was explained by these two factors. We conclude that subjects with the Arg16Arg polymorphism of the  2-AR gene have a reduced thermogenic response to  2-adrenergic stimulation. Although this relatively small study needs confirmation, the findings support a role for this polymorphism in the development and maintenance of overweight and obesity.
Objective: Physical education (PE) has been attributed an important role in providing young peopl... more Objective: Physical education (PE) has been attributed an important role in providing young people with physical activity. If sufficiently active, PE lessons could contribute to physical activity levels in youth. Therefore, the purpose of this study was to determine the overall intensity of Dutch primary and secondary school physical education (PE) lessons and the influence of various lesson characteristics on these intensity levels. Methods: Between September 2008 and June 2009 heart rates were measured using the Polar Team System in a nationally distributed sample of 913 students in 40 schools in the Netherlands. Results: Overall percentages lesson time in moderate-to-vigorous physical activity (MVPA) were 46.7% and 40.1% during primary school and secondary school PE respectively. Results indicated a sharp decline in girls' PE intensity levels at the beginning of secondary school. Furthermore, secondary school boys were more active than girls. The high prevalence of teamgames in the Dutch PE curricula might prevent secondary school girls from attaining similar physical activity levels during PE.
In sport science and physiology, exercise performance tests are frequently used to examine the in... more In sport science and physiology, exercise performance tests are frequently used to examine the influence of experimental interventions on endurance performance. The reliability (or reproducibility) of performance of a test refers to the consistency or reproducibility of performance when someone performs the test repeatedly. The reliability of time-to-exhaustion and time-trial performance test protocols has not been studied extensively. To date, the studies of Jeukendrup et al (cyling) and Laursen et al. (running) are the only studies that directly compared the reliability of TTE versus TT exercise tests. The reliability of TTE versus TT in healthy untrained subjects needs to be studied since athletic status, exercise intensity and duration are factors that affect the reliability of performance tests. Therefore, the purpose of this study was 1) to evaluate the reproducibility of comparable TT and TTE tests in healthy untrained male subjects; and 2) to evaluate the performance (time t...
Introduction: In cardiopulmonary rehabilitation programs (CPR), constant-load cycle endurance tes... more Introduction: In cardiopulmonary rehabilitation programs (CPR), constant-load cycle endurance tests (CLET) protocols are used to evaluate the response to specific interventions. In healthy subjects CLET protocols show a much lower reproducibility than time trial test (TTT) protocols. The purpose of this study was to evaluate the reproducibility of the CLET protocol and TTT protocol on a cycle ergometer in patients with COPD. Methods: In 20 patients with COPD (GOLD II-IV, FEV1 of 56±15%) exercise performance was measured. Patients were randomly allocated to a CLET protocol or TTT protocol. Patients performed the test protocol to which they were assigned, five times. Patients in the CLET group exercised to exhaustion at 120% of the actual individual training workload attained in the during CPR training sessions. Patients in the TTT group were asked to perform a certain amount of work (120% * Wtraining * 420) as fast as possible. Results: TTT protocol showed a significantly lower coeff...
Dit overzichtsartikel beschrijft de huidige stand van zaken in de wetenschap omtrent de verklarin... more Dit overzichtsartikel beschrijft de huidige stand van zaken in de wetenschap omtrent de verklaring voor het optreden van het verschijnsel Spierkramp. Nieuwe inzichten gecombineerd met bestaande ervaringen geven aan dat met name spiervermoeidheid een belangrijke factor is in het optreden van spierkramp. Aansturing vanuit het zenuwstelsel kan hiermee verstoord zijn en leiden tot ongecontroleerde samentrekking.
Journal of cardiopulmonary rehabilitation and prevention, 2017
The primary aims of this study were (1) to evaluate whole-body mechanical efficiency (ME) in a la... more The primary aims of this study were (1) to evaluate whole-body mechanical efficiency (ME) in a large group of chronic obstructive pulmonary disease (COPD) patients with a wide range of degrees of illness and (2) to examine how ME in COPD is related to absolute work rate and indices of disease severity during exercise testing. A total of 569 patients (301 male patients; GOLD stage I: 28, GOLD stage II: 166, GOLD stage III: 265, and GOLD stage IV: 110) with chronic obstructive pulmonary disease (COPD) were included in the data analysis. Individual maximal workload (watt), peak minute ventilation ((Equation is included in full-text article.)E, L/min body temperature and pressure, saturated), and peak oxygen uptake ((Equation is included in full-text article.)O2, mL/min standard temperature and pressure, dry) were determined from a maximal incremental cycle ergometer test. Ventilatory and metabolic response parameters were collected during a constant work rate test at 75% of the individ...
Voor veel mensen is afvallen een belangrijke reden om zich lichamelijk in te spannen. Ook op sc... more Voor veel mensen is afvallen een belangrijke reden om zich lichamelijk in te spannen. Ook op scholen wordt er soms aandacht besteed aan de relatie tussen (over)gewicht en inspanning. Maar hoeveel energie verbruik je nu eigenlijk tijdens inspanning? En hoeveel vet verbrand je daarmee?
The sympathetic nervous system is involved in the control of energy metabolism and expenditure. D... more The sympathetic nervous system is involved in the control of energy metabolism and expenditure. Diet-induced thermogenesis is mediated partly by the ß-adrenergic component of this system. The aim of the present study was to investigate the role of genetic variation in the ß2-adrenoceptor in diet-induced thermogenesis. Data from twenty-four subjects (fourteen men and ten women; BMI 26·7(sem 0·8) kg/m2; age 45·2(sem1·4) years) with different polymorphisms of the ß2-adrenoceptor at codon 16 (Gly16Gly, Gly16Arg or Arg16Arg) were recruited for this study. Subjects were given a high-carbohydrate liquid meal, and the energy expenditure, respiratory exchange ratio, and plasma concentrations of NEFA, glycerol, glucose, insulin and catecholamines were measured before and over 4 h after the meal. The AUC of energy expenditure (diet-induced thermogenesis) was not significantly different between polymorphism groups, nor was the response of any of the other measured variables to the meal. In a mu...
Background: The aim of the present study was to establish whether polymorphisms, especially those... more Background: The aim of the present study was to establish whether polymorphisms, especially those within the promoter region, of the β 2-adrenoceptor gene (ADRB2) influence β 2-adrenoceptor expression in human lung. Methods: The density of β-adrenoceptors in human lung tissue (n=88) was determined by saturation binding using the radioligand, iodinated cyanopindolol. Discrimination of β 1-and β 2-adrenoceptors was determined using the highly selective β 1-adrenoceptor antagonist, CGP20712A. Genotype was determined at 5 positions of ADRB2 previously reported as polymorphic. Potential influences of single nucleotide polymorphisms (SNPs) within the promoter region (-367,-47) and coding block (46, 79, 491) of ADRB2 on β 2-adrenoceptor expression were investigated. Results: The density of β 2-adrenoceptors was variable among the 88 lung preparations studied ranging from 17 to 177 fmol/mg protein (mean±S.E.M., 72±4 fmol/mg protein). There was no influence of genotype on β 2-adrenoceptor expression for any of the polymorphisms studied except at position 491. The polymorphism at position 491C>T, leading to a change from thr to ile at amino acid 164, is uncommon. Preparations genotyped as heterozygous (126±15 fmol/mg protein; n=5) expressed significantly (P = 0.0005) higher levels of β 2-adrenoceptor than those that were homozygous (69±4 fmol/mg protein; n=83).
The Journal of Clinical Endocrinology & Metabolism, 2005
The -adrenergic system is involved in the control of energy metabolism and expenditure. The  2-... more The -adrenergic system is involved in the control of energy metabolism and expenditure. The  2-adrenergic receptor ( 2-AR) gene shows polymorphisms that have been associated with obesity in several studies. In vitro and in vivo studies suggest differences in  2-AR-mediated function between these polymorphisms. The aim of this study was to investigate the influence of genetic variation in codon 16 of the  2-AR gene on energy metabolism in humans. Thirty-four subjects were recruited [Gly16Gly (n ؍ 13), Gly16Arg (n ؍ 16), or Arg16Arg (n ؍ 5)]. The  2-AR was stimulated with two doses of salbutamol (50 and 100 ng/kg fat-free mass per minute) after blockade of the  1-adrenergic receptors with atenolol. Energy expenditure and plasma substrate and hormone concentrations were measured. The increase in energy expenditure (⌬EE) was significantly different among groups in which the Arg16Arg group showed the lowest increase (P < 0.05 vs. Gly carriers). In a multiple regression model, variations in the increase in nonesterified fatty acid concentration during salbutamol infusion (partial r ؍ 0.51) and the polymorphism contributed significantly to the variation in ⌬EE. Thirty-five percent of the variation in ⌬EE was explained by these two factors. We conclude that subjects with the Arg16Arg polymorphism of the  2-AR gene have a reduced thermogenic response to  2-adrenergic stimulation. Although this relatively small study needs confirmation, the findings support a role for this polymorphism in the development and maintenance of overweight and obesity.
Objective: Physical education (PE) has been attributed an important role in providing young peopl... more Objective: Physical education (PE) has been attributed an important role in providing young people with physical activity. If sufficiently active, PE lessons could contribute to physical activity levels in youth. Therefore, the purpose of this study was to determine the overall intensity of Dutch primary and secondary school physical education (PE) lessons and the influence of various lesson characteristics on these intensity levels. Methods: Between September 2008 and June 2009 heart rates were measured using the Polar Team System in a nationally distributed sample of 913 students in 40 schools in the Netherlands. Results: Overall percentages lesson time in moderate-to-vigorous physical activity (MVPA) were 46.7% and 40.1% during primary school and secondary school PE respectively. Results indicated a sharp decline in girls' PE intensity levels at the beginning of secondary school. Furthermore, secondary school boys were more active than girls. The high prevalence of teamgames in the Dutch PE curricula might prevent secondary school girls from attaining similar physical activity levels during PE.
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