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Biomedical subjects

Christopher J Gore

Publications and source records attributed to Christopher J Gore.

11 recordsLinked to original sources
PubMed2003

Measurement and prediction of energy expenditure in males during household and garden tasks.

Participation in at least 30 min of moderate intensity activity on most days is assumed to confer health benefits. This study accordingly determined whether the more vigorous household and garden tasks (sweeping, window cleaning, vacuuming and lawn mowing) are performed by middle-aged men at a moderate intensity of 3-6 metabolic equivalents (METs) in the laboratory and at home. Measured energy expenditure during self-perceived moderate-paced walking was used as a marker of exercise intensity. Energy expenditure was also predicted via indirect methods. Thirty-six males [ X (SD): 40.0 (3.3) years; 179.5 (6.9) cm; 83.4 (14.0) kg] were measured for resting metabolic rate (RMR) and oxygen consumption ( VO(2)) during the five activities using the Douglas bag method. Heart rate, respiratory frequency, CSA (Computer Science Applications) movement counts, Borg scale ratings of perceived exertion and Quetelet's index were also recorded as potential predictors of exercise intensity. Except for vacuuming in the laboratory, which was not significantly different from 3.0 METs ( P=0.98), the MET means in the laboratory and home were all significantly greater than 3.0 ( P</=0.006). The sweeping and vacuuming MET means were significantly higher ( P<0.001) at home than in the laboratory, whereas the converse applied for window cleaning and lawn mowing. Measured RMR was significantly lower ( P<0.001) than the 1-MET constant. Estimating METs by fitting random intercept regression models to the data resulted in standard deviations for the "leave-one-out" prediction errors (predicted-measured) of 0.4 and 0.5 METs for the laboratory and home equations, respectively. While the means indicate that all the activities were performed at a moderate intensity, there was great inter-individual variability in energy expenditure. The laboratory and home-based equations predicted with correct classification rates of 89% and 88%, respectively, whether energy expenditure was <3.0 or >/=3.0 METs.

Activities of Daily Living↗
PubMed2003

CPX/D underestimates VO(2) in athletes compared with an automated Douglas bag system.

PURPOSE: Based on persistent reports of low oxygen consumption VO(2) from Medical Graphics CPX/D metabolic carts, we compared the CPX/D against an automated Douglas bag system. METHODS: Twelve male athletes completed three, randomized 25-min bouts (5 min at 100, 150, 200, 250, and 300 W) on a cycle ergometer with intervening 30-min rests. One bout was measured on each of the CPX/D, the CPX/D with altered software (CPX/DDelta), and an automated Douglas bag system at Flinders University (FU). The CPX/DDelta software alteration was an apparent lag time correction factor of 60 ms. RESULTS: For the CPX/D, both VO(2) and VCO(2) were significantly lower than the FU system at 100-300 W, and the relative differences ranged -10.7 to -12.0% and -7.7 to -8.2%, respectively. Altering the software approximately halved the VO(2) discrepancy between the CPX/DDelta and FU systems. When data from all five workloads were pooled, V(E) of the CPX/D (67.2 +/- 26.4 L x min-1) and CPX/DDelta (67.5 +/- 26.9 L x min-1) were significantly lower than for the FU system (70.5 +/- 27.1 L x min-1); and at 300 W, the relative differences were -4.0% and -3.4% for the CPX/D and CPX/DDelta, respectively. Altering the software changed the pooled %O(2) from 16.24 +/- 0.40% for the CPX/D to 16.04 +/- 0.39% for the CPX/DDelta, and these were significantly different than pooled data for the FU system (16.15 +/- 0.39%). CONCLUSIONS: During submaximal exercise, the CPX/D yields VO(2) values that are approximately 11% lower than the criterion system, and the source of the discrepancy does not appear to be primarily related to volume measurement. A disturbing observation is that factory defaults for the lag time use different correction factors, which vary by 60 ms and this significantly alters VO(2) and VCO(2).

Adolescent↗
PubMed2003

Second-generation blood tests to detect erythropoietin abuse by athletes.

BACKGROUND AND OBJECTIVES: We previously developed blood tests that were introduced at the Sydney 2000 Olympic Games to identify athletes injecting recombinant human erythropoietin (rHuEPO). The aim of this study was to re-analyse our existing database to develop models with heightened sensitivity, using wherever possible blood parameters measurable with appropriate standards of analytical performance. DESIGN AND METHODS: The principal database for this study was derived from a double-blind trial in which 57 recreational athletes were administered either rHuEPO or placebo. Standard discriminant analysis was used to derive two ON models (ON-hes and ON-he) and two OFF models (OFF-hr and OFF-hre) sensitive to accelerated and decelerated erythropoiesis respectively, utilising concentrations of hemoglobin (h), erythropoietin (e) and serum transferrin receptor (s), as well as percent reticulocytes (r). The ability of our models to detect rHuEPO administration was assessed by comparing model scores of subjects in the administration trial with the model scores of 1152 elite athletes from 12 countries. RESULTS: The ability of the new models to detect rHuEPO administration was generally higher than that of our previous models, particularly during phases when low doses of rHuEPO were used, and after injections had ceased. INTERPRETATION AND CONCLUSIONS. The increased stability of the new blood parameters facilitates transport of samples to central laboratories, and the heightened sensitivity of the new models makes them better than existing models for federations wishing to screen samples for urine testing and to identify and target suspect athletes for out-of-competition testing. However procedures should be incorporated that respect an elevated model score caused by genetic, health or environmental circumstances.

Doping in Sports↗
PubMed2003

The effect of common hematologic abnormalities on the ability of blood models to detect erythropoietin abuse by athletes.

BACKGROUND AND OBJECTIVES: Algorithms that combine scores from multiple blood parameters are demonstrably effective in highlighting recombinant human erythropoietin (rHuEPO) administration, and have been used to deter rHuEPO use by athletes. These models are sensitive to atypical levels of blood parameters encountered during altered states of red cell production. Because hematologic abnormalities can also result in unusual blood profiles, the aim of this study was to document the incidence and magnitude of such abnormalities in an elite athlete population. DESIGN AND METHODS: We screened blood samples obtained from 413 female and 739 male elite athletes from 12 countries for known hematologic abnormalities, and compared the algorithm scores for these athletes with those of their healthy counterparts. We also established the magnitude of blood parameters required for model scores to exceed cut-offs associated with rHuEPO use. RESULTS: We found that 0.7% of male and 2.4% of female athletes were iron deficient either with our without anemia. An additional 1.4% of males and 1.0% of females had hemoglobinopathies. On average these athletes' model scores were at or below the score of their healthy counterparts. The greatest influence on our models was hemoglobin concentration. Values of other parameters must exceed normal ranges by a substantial margin in order for model scores to approach levels associated with rHuEPO use. INTERPRETATION AND CONCLUSIONS: The hematologic disorders we encountered in elite athletes were not associated with model scores that exceeded the nominal cut-offs that we have previously recommended to delineate rHuEPO use. We did not find any abnormalities among elite endurance athletes that were associated with high model scores.

Adolescent↗
PubMed2003

Effect of altitude on second-generation blood tests to detect erythropoietin abuse by athletes.

BACKGROUND AND OBJECTIVES: ON- and OFF-model scores derived from blood parameters sensitive to erythropoiesis have been shown to be a useful tool to identify athletes who are currently injecting erythropoietin to enhance performance or those who have recently stopped doing so. We investigated changes in blood parameters and model scores during and after exposure to terrestrial and simulated altitudes. DESIGN AND METHODS: We retrospectively evaluated changes in hematologic data collected from 19 elite cyclists who lived and trained 2690 m above sea level for 26-31 days, from six elite Kenyan runners who lived 2100 m above sea level but descended to compete at sea level competitions, and from 39 well-trained subjects who resided at sea level but slept at a simulated altitude of 2650-3000 m for 20-23 days of either consecutive or intermittent nightly exposure. RESULTS: Upon ascent to a terrestrial altitude, ON- and OFF-model scores increased immediately, mainly because of an increase in hemoglobin concentration. Scores had not returned fully to baseline three weeks after return to sea level, because of the persistence of the raised hemoglobin concentration for the ON and OFF scores and a fall in reticulocyte percentage for OFF scores. Effects were smaller or negligible for simulated altitude. For Kenyan runners, ON- and OFF-model scores decreased within seven days of descent to sea level. INTERPRETATION AND CONCLUSIONS: Our results reinforce the notion that caution should be exercised when interpreting blood results from athletes who have recently been exposed to either terrestrial or simulated altitude, and appropriate allowance should be made for the effect of altitude on blood model scores.

Acclimatization↗
PubMed2002

Effects of prolonged low doses of recombinant human erythropoietin during submaximal and maximal exercise.

The aim of this study was to characterise the effect of prolonged low doses of recombinant erythropoietin (r-HuEPO) on the responses to submaximal and maximal exercise. Volunteer recreational athletes ( n=21) were divided into three groups: r-HuEPO+intravenous iron (EPO+IV, n=7), r-HuEPO+oral iron (EPO+OR, n=9) and placebo ( n=5). During the 12 week study, r-HuEPO or saline injections were given three times a week for the first 8 weeks and for the final 4 weeks the subjects were monitored but no injections were administered. The r-HuEPO doses were 50 IU x kg(-1) body mass for 3 weeks and 20 IU x kg(-1) body mass for the next 5 weeks. An exercise test comprising three submaximal intensities and then increments to elicit maximal aerobic power (VO2max ) was conducted during weeks 0, 4, 8 and 12. During week 0, the mean intensity of the submaximal stages was 60%, 72% and 81%. Blood taken at rest was analysed twice a week for haematocrit (Hct). The relative increases in at weeks 4, 8 and 12 were 7.7%, 9.7% and 4.5%, respectively, for the EPO+IV group; 6.0%, 4.7% and 3.1% for the EPO+OR group; and -0.5%, -0.1% and -1.0% for the placebo group, where the improvements at week 12 for the EPO+IV and EPO+OR groups remained significantly above week 0 values. The Hct was significantly elevated by 0.06 and 0.07 units at week 3 in the EPO+IV and EPO+OR groups, respectively, and was stable during the 5 weeks of low-dose r-HuEPO. After 8 weeks of r-HuEPO use, plasma lactate concentration tended to be lower at exercise intensities ranging from 60% to 100%. This study confirmed the ability of low doses of r-HuEPO to maintain Hct and at elevated levels.

Administration, Oral↗
PubMed2002

Determining energy expenditure during some household and garden tasks.

PURPOSE: This study: a) calculated the reproducibility (intraclass correlation coefficient, ICC) and precision (technical error of measurement, TEM) for VO2 during moderate paced walking, self-paced sweeping, window cleaning, vacuuming and lawn mowing; b) determined which of the five activities rated >or= 3.0 when exercise intensity was calculated in METs (1 MET or metabolic equivalent = VO2 of 3.5 mL.kg-1.min-1) and multiples of the measured resting metabolic rate (RMR); and c) expanded the limited database on energy expenditure during household and garden activities. METHODS: Twelve men and 12 women (mean +/- SD: 39.3 +/- 3.4 yr; 171.6 +/- 9.6 cm; 81.0 +/- 15.5 kg) were measured for RMR and VO2 during the five activities on two separate days via indirect calorimetry by using the Douglas bag method. RESULTS: The interday ICCs and TEMs for the five activities ranged from 0.81 to 0.97 and from 2.1 to 7.0%, respectively. The means were significantly (P < 0.001) above 3.0 for moderate paced walking (range = 3.3-8.7), sweeping (2.9-6.7), window cleaning (3.0-6.0), vacuuming (2.6-4.4), and lawn mowing (4.9-7.5) when VO2 was divided by measured RMR, but one and five subjects scored below 3.0 for sweeping and vacuuming, respectively. Division of exercise VO2 by the convention of 3.5 mL O2.kg-1.min-1 significantly decreased (P < 0.001) each mean, and lawn mowing (5.0 METs) was the only activity where all subjects scored above 3.0 METs (P < 0.001; 3.8-6.4); nevertheless, the means for walking (3.7 METs), sweeping (3.2 METs), and window cleaning (3.6 METs) were also in the moderate intensity category of 3-6 METs. CONCLUSIONS: These data: a) emphasize that the VO2 during self-paced moderate intensity walking and self-paced household and garden activities can be measured with reproducibility and precision, b) demonstrate that expressing energy expenditure in conventional METs yields lower values than when it is presented as a multiple of measured RMR, c) suggest that all activities except vacuuming are performed at moderate intensity when energy expenditure is expressed in conventional METs, and d) highlight the biological variability in energy expenditure when different people perform the same task.

Activities of Daily Living↗
PubMed2002

Living high-training low increases hypoxic ventilatory response of well-trained endurance athletes.

This study determined whether "living high-training low" (LHTL)-simulated altitude exposure increased the hypoxic ventilatory response (HVR) in well-trained endurance athletes. Thirty-three cyclists/triathletes were divided into three groups: 20 consecutive nights of hypoxic exposure (LHTLc, n = 12), 20 nights of intermittent hypoxic exposure (four 5-night blocks of hypoxia, each interspersed with 2 nights of normoxia, LHTLi, n = 10), or control (Con, n = 11). LHTLc and LHTLi slept 8-10 h/day overnight in normobaric hypoxia (approximately 2,650 m); Con slept under ambient conditions (600 m). Resting, isocapnic HVR (DeltaVE/DeltaSp(O(2)), where VE is minute ventilation and Sp(O(2)) is blood O(2) saturation) was measured in normoxia before hypoxia (Pre), after 1, 3, 10, and 15 nights of exposure (N1, N3, N10, and N15, respectively), and 2 nights after the exposure night 20 (Post). Before each HVR test, end-tidal PCO(2) (PET(CO(2))) and VE were measured during room air breathing at rest. HVR (l. min(-1). %(-1)) was higher (P < 0.05) in LHTLc than in Con at N1 (0.56 +/- 0.32 vs. 0.28 +/- 0.16), N3 (0.69 +/- 0.30 vs. 0.36 +/- 0.24), N10 (0.79 +/- 0.36 vs. 0.34 +/- 0.14), N15 (1.00 +/- 0.38 vs. 0.36 +/- 0.23), and Post (0.79 +/- 0.37 vs. 0.36 +/- 0.26). HVR at N15 was higher (P < 0.05) in LHTLi (0.67 +/- 0.33) than in Con and in LHTLc than in LHTLi. PET(CO(2)) was depressed in LHTLc and LHTLi compared with Con at all points after hypoxia (P < 0.05). No significant differences were observed for VE at any point. We conclude that LHTL increases HVR in endurance athletes in a time-dependent manner and decreases PET(CO(2)) in normoxia, without change in VE. Thus endurance athletes sleeping in mild hypoxia may experience changes to the respiratory control system.

Acclimatization↗
PubMed2002

Respiratory events and periodic breathing in cyclists sleeping at 2,650-m simulated altitude.

We examined the initial effect of sleeping at a simulated moderate altitude of 2,650 m on the frequency of apneas and hypopneas, as well as on the heart rate and blood oxygen saturation from pulse oximetry (SpO2) during rapid eye movement (REM) and non-rapid eye movement (NREM) sleep of 17 trained cyclists. Pulse oximetry revealed that sleeping at simulated altitude significantly increased heart rate (3 +/- 1 beats/min; means +/- SE) and decreased SpO2 (-6 +/- 1%) compared with baseline data collected near sea level. In response to simulated altitude, 15 of the 17 subjects increased the combined frequency of apneas plus hypopneas from baseline levels. On exposure to simulated altitude, the increase in apnea was significant from baseline for both sleep states (2.0 +/- 1.3 events/h for REM, 9.9 +/- 6.2 events/h for NREM), but the difference between the two states was not significantly different. Hypopnea frequency was significantly elevated from baseline to simulated altitude exposure in both sleep states, and under hypoxic conditions it was greater in REM than in NREM sleep (7.9 +/- 1.8 vs. 4.2 +/- 1.3 events/h, respectively). Periodic breathing episodes during sleep were identified in four subjects, making this the first study to show periodic breathing in healthy adults at a level of hypoxia equivalent to 2,650-m altitude. These results indicate that simulated moderate hypoxia of a level typically chosen by coaches and elite athletes for simulated altitude programs can cause substantial respiratory events during sleep.

Adult↗
PubMed2002

Development of reference ranges in elite athletes for markers of altered erythropoiesis.

BACKGROUND AND OBJECTIVES: Our previous research developed two statistical models that are useful indicators of current (ON-model) or recently discontinued (OFF-model) recombinant human erythropoietin (rHuEPO) use by athletes. The component variables of the ON-model are hematocrit (Hct), reticulocyte hematocrit (RetHct), serum erythropoietin (EPO), percent macrocytes (%Macro), and soluble transferrin receptor (sTfr), whilst the OFF-model uses only the first three variables. Genetics and training modalities of elite athletes may conceivably produce unusual values for blood parameters related to erythropoiesis. The aims of this study were to develop reference ranges in elite athletes for key hematologic parameters as well as ON- and OFF-models scores, and to evaluate the effect of ethnicity, gender, residence at moderate altitude (approximately 2000 m) and within-individual variation on the variables and model scores. DESIGN AND METHODS: Over a period of three weeks, 413 female and 739 male elite athletes from 12 countries visited laboratories to provide three blood samples for analysis of blood parameters sensitive to erythropoiesis. For each parameter and for the ON- and OFF-model scores, we used mixed modeling to establish the range within which we could be 95% certain that the value for a randomly chosen athlete would fall, taking into account various random effects (variation within and between subjects and laboratories) and fixed effects (means for different levels of ethnicity, age, sport, altitude of residency). We performed similar analyses for changes in the ON- and OFF-model scores between the three visits. RESULTS: Most fixed effects were accompanied by clear-cut, small to moderate differences in several parameters. However, residency at moderate altitude was accompanied by a much higher hematocrit than residency nearer sea level, with the mean (and 95% confidence limits) for the difference being 2.3 (0.9 to 3.7) and 1.8 (0.1 to 3.5) units for males and females, respectively. Males at altitude also demonstrated a moderately higher ON-model score. Otherwise the influence of these effects was small for ON-, OFF- and changes in model scores. INTERPRETATION AND CONCLUSIONS: Assessment of an athlete's blood parameters and ON- and OFF-model scores may need adjustment for training modalities and other characteristics of the subject. Changes in model scores (together with monitoring of urine samples for the presence of rHuEPO) provide a promising approach to detection of rHuEPO abuse, because they are less sensitive to subject characteristics and less variable than raw model scores.

Adolescent↗