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Biomedical subjects

T R Thomas

Publications and source records attributed to T R Thomas.

At least 37 records · Page 2Linked to original sources
PubMed1989

Fat energy use and plasma lipid changes associated with exercise intensity and temperature.

The effect of 60 min of exercise at two intensities (50 and 60% VO2max) and temperatures (0 and 22 degrees C) on changes (delta) in plasma lipids [triglycerides (TG), glycerol (GLY), total cholesterol (TC), and HDL-cholesterol (HDL-C)] was examined. Subjects were 10 men aged 27 +/- 7 years (VO2max = 3.81 +/- 0.45 1 min, % fat = 12.2% +/- 7.1%). VO2 and respiratory exchange ratio results indicated that total energy and fat energy use were similar at the two temperatures. Changes in plasma volume (%delta PV) were different (P less than 0.05) at the two temperatures (22 degrees C: -2.3% vs 0 degrees C: 1.1%). Combining the data at each temperature revealed that the increases in concentrations were greater (P less than 0.05) at 22 degrees C (delta TG = 0.22, delta GLY = 0.20, delta TC = 0.14, delta HDL-C = 0.05 mmol l-1) vs 0 degrees C (delta TG = 0.10, delta GLY = 0.12, delta TC = 0.05, delta HDL-C = 0.02 mmol l-1). Combining the data for each intensity revealed that the increases in concentration were greater (P less than 0.05) at 60% VO2max for delta TG and delta HDL-C. The 60% VO2max/22 degrees C bout produced greater changes (P less than 0.05) than all other bouts for delta TC and delta HDL-C (0.21 and 0.08 mmol l-1, respectively). Only delta TG and delta GLY were greater at 22 degrees C when adjusted for %delta PV. These metabolic and plasma lipid results indicate that cold exposure does not act synergistically with exercise to further stimulate fat metabolism.

Adult↗
PubMed1989

Resistance exercise program effects on abdominal function and physique.

The purpose of this study was to compare the effects of different abdominal exercise programs on abdominal muscular function and physique. Forty-five men and women (aged 18-26 yr) were randomly assigned to training using: (1) abdominal crunch (AC) weight machine; (2) steated incline (SI) weight machine; or (3) incline sit-up (ISU) exercise. Strength training occurred three times per week for 10 weeks. All groups improved in abdominal muscular strength and endurance. The ISU and AC group improved in muscular power (timed sit-up), while flexibility was maintained or increased in all groups. Abdominal skinfolds tended to increase and girths generally were unaltered by the abdominal exercise programs. These results suggest that abdominal weight machines or traditional incline sit-ups are effective in altering abdominal muscular function, but local abdominal exercise alone is unsatisfactory for reducing stomach skinfolds or girths.

Abdominal Muscles↗
PubMed1989

Metabolic responses associated with four modes of prolonged exercise.

The purpose of this study was to compare energy expenditure and substrate utilization during 60 min of steady state-exercise at similar heart rates (HR) using four exercise modes: stationary cycle (C), rower (R), ski simulator (S), and treadmill (walking) (T). Five subjects (means age = 23 +/- 4 yr) performed 60 min of continuous exercise at 65% HR max on each of the four modes in random order. Total energy (TE) and fat energy (FE) expenditure were determined from VO2 and respiratory exchange ratio (RER). VO2 during exercise averaged 2.427 for C, 2.167 for R, 2.242 for S, and 2.420 l min-1 for T and were not significantly different by repeated measures ANOVO (p greater than 0.05). RER, TE, and FE also were not statistically different among exercise modes. However, walking and skiing tended to use more fat; the average 60 min cumulative exercise values were 960 for C, 871 for R, 1088 for S, and 1188 kJ for T. The rate of fat expenditure generally increased after 20 min on all modes. These results indicate that the energy expended at comparable relative HR's is similar for four aerobic exercise modes.

Adult↗
PubMed1988

Dietary preparation and per cent fat measurement by hydrostatic weighing.

To examine if the dietary preparation for hydrostatic weighing (HW) alters the % fat measurement, seven men and three women (age 29 +/- 6, Males 11.7 +/- 7.3% fat and Females 24.1 +/- 5.4% fat, mean +/- SD) were assessed before and after three meals. On separate days and in random order, each subject (1) ate a salad with toppings (600 g) with small beverage, (2) ate two bean burritos and one bean tostada (900 g) with small beverage, and (3) drank 800 ml of carbonated beverage. The subject was reweighted 45 min after the meals and immediately after the beverage ingestion. Functional residual capacity was assessed simultaneously with underwater weight. Dependent t-tests indicated that body weight in air increased after each of the three means (Bean 0.78, Salad 0.92, Beverage 0.90 kg, all p less than 0.05), but underwater weights were unchanged. Following the salad, body density (1064.6 vs 1061.8 kg.m-3) and % fat (15.0 vs 16.3%, p less than 0.05) were significantly different pre-meal vs post-meal. Likewise, beverage ingestion resulted in decreased body density (1064.7 vs 1061.2 kg.m-3) and increased % fat (15.0 vs 16.5%, p less than 0.05). The bean meal did not cause a change in measured body density (1062.8 vs 1062.8 kg.m-3) or % fat (15.8 vs 15.8%). These results indicate that for the most accurate analysis, preliminary dietary preparation for HW should include food and beverage restriction.

Adipose Tissue↗
PubMed1985

Response of HDL cholesterol, apoprotein A-I, and LCAT to exercise withdrawal.

The effect of short-term exercise withdrawal on plasma lipoproteins, apoprotein A-I (Apo A-I), and lecithin:cholesterol acyltransferase (LCAT) was studied in moderately trained lifestyle exercisers. Eight endurance-trained men, age 18-45 years (means = 29 years), withdrew from aerobic activity for 6 weeks, while an age and fitness-matched control group (n = 9) maintained normal exercise habits. A baseline period that included two blood samplings preceded the detraining intervention. Plasma total cholesterol (TCHOL), HDL cholesterol (HDL-C) and triglyceride (TG) levels were determined weekly. Other blood variables (HDL2-C, HDL3-C, Apo A-I, and LCAT), % fat, and aerobic capacity (VO2max) were measured pre-, mid-, and post-experiment. A two-way repeated measures analysis of variance (ANOVA) indicated that the 6-week exercise withdrawal period failed to elicit significant mean changes in any blood variable, % fat, or VO2max. Therefore, a short-term layoff from aerobic activity by moderately trained, chronic exercisers generally does not adversely affect the blood lipoprotein profile or aerobic capacity.

Adolescent↗
PubMed1985

Fat utilization enhanced by exercise in a cold environment.

To study substrate utilization during cold temperature exercise, seven men dressed in shorts, T-shirts, and light gloves performed 60 min of continuous cycle ergometer exercise at -10 degrees C and 22 degrees C. The workload at both temperatures represented 66% of the cycle-measured maximal heart rate. Oxygen consumption and respiratory exchange ratio (RER) were measured at rest and during 60 min of exercise. Rates of total and fat energy utilization (kJ X min-1) during exercise were calculated from VO2 and RER. A two-factor repeated measures analysis of variance indicated that at rest oxygen consumption averaged 56% higher and RER 5% lower at -10 degrees C. During exercise, oxygen consumption averaged 10% higher (P less than 0.05), and RER averaged 2% lower (P less than 0.05) at -10 degrees C. The rates of total energy use (mean +/- SD = 39.3 +/- 1.2 vs 35.7 +/- 1.3 kJ X min-1; P less than 0.05) were significantly higher at -10 degrees C than at 22 degrees C. In addition, the rate of fat use increased significantly in both groups after 30 min of exercise. The cumulative total energy expenditure for 60 min of exercise was 13% higher (2379 +/- 308 vs 2110 +/- 415 kJ; P less than 0.05 and the cumulative fat expenditure was 35% higher (979 +/- 209 vs 724 +/- 184 kJ: P less than 0.05) in the cold environment. These results indicate that a cold environment can significantly enhance fat utilization during endurance exercise.

Adipose Tissue↗
PubMed1985

Effects of interval and continuous running on HDL-cholesterol, apoproteins A-1 and B, and LCAT.

The purpose of this study was to examine the effect of interval and continuous exercise programs on plasma lipoproteins, apoproteins, and lecithin: cholesterol acyltransferase (LCAT). Thirty-six college male students (age 18-25 yrs.) were randomly assigned to a 5 mile continuous exercise group, 4 minute interval (1:1, work:rest), 2 minute interval (1:1-1/2, work:rest), or control. Workloads were equated by kcal expenditure/workout. The training groups exercised for one hour three times a week for 11 weeks. Neither interval or continuous exercise programs significantly altered plasma total cholesterol, high density lipoprotein cholesterol (HDL-C), apoprotein A-1 (Apo A-1), apoprotein B (Apo B), or LCAT. Posttest maximal oxygen consumption was significantly higher than pretest for the 4 minute interval and 5 mile continuous groups. Thus continuous exercise and long interval programs resulted in gains in aerobic capacity, but none of the training programs were effective in altering the plasma lipoproteins or apoproteins investigated.

Adolescent↗
PubMed1984

Effects of different running programs on VO2 max, percent fat, and plasma lipids.

This study attempted to determine the effects of interval and continuous running on factors associated with cardiovascular health. Fifty-nine untrained men and women, ages 18-32 years, were randomly assigned to one of four groups: (1) 4 mile: running continuously at 75% of maximal heart rate (approximately 500 Cal/session) (2) 2 mile: running continuously at 75% of maximal heart rate (approximately 250 Cal/session) (3) interval: running one min at 90% maximal heart rate followed by three min of walking for eight sets (approximately 500 Cal/session) (4) control: no exercise program. The training was performed three times per week for 12 weeks. Treadmill VO2 max and percent body fat by hydrostatic weighing were assessed pre- and post training. Pre and post analyses were performed on plasma for triglycerides (TG), cholesterol (Chol), and high density lipoprotein cholesterol (HDL-C). Analysis of covariance indicated that only the interval group improved more than the control in VO2 max. Percent fat decreased in all exercise groups, but no program was superior. Changes in TG, Chol, or HDL-C were not different among groups. Although men and women differed on the pretests in VO2 max, percent fat, and HDL-C, their response to the training was similar. These results indicate that interval training may benefit aerobic capacity more than continuous running in young adults who have moderately high initial fitness levels. The data also indicate that cardiovascular fitness parameters are not easily altered by short term exercise in young active men and women.

Adipose Tissue↗
PubMed1983

Physiological and psychological correlates of success in track and field athletes.

Twenty-four collegiate distance runners and 20 power athletes (sprinters and jumpers) of various success levels were tested on a number of physiological and psychological parameters. Multiple regression analysis indicated that physiological factors could explain over 81% of the variance related to successful distance running while physiological and psychological factors could explain over 80% of the of the variance related to successful sprinting and jumping. Body weight, fibre type, low density lipoprotein-cholesterol, and hamstring strength were significant singular correlates to successful distance running. Year in school, percent body fat, quadriceps strength, and leg muscle balance were significant single correlates to successful sprinting and jumping performance.

Adolescent↗
PubMed1982

The effect of acute exercise on body density, body volume, and plasma volume.

In order to determine the relationship between reductions in body weight, body volume, and plasma volume, 22 track runners underwent exercises of various intensities and durations. The average mileage performed in the distance runs was 8.4 miles. The average caloric cost was 822 and 288 Cal for the distance and sprint activities, respectively. The overall range of energy expenditure was 100 to 1000 Cal. Before and after the workbout, body volume and density were determined by hydrostatic weighing on each subject. In addition, venous blood samples were analyzed for hematocrit (Hct) and hemoglobin (Hb), and the percent change in plasma volume (% delta PV) was calculated. Body weight and body volume decreases occurred in all subjects. Body density, percent body fat, and plasma volume were significantly altered only in the group of athletes undergoing distance runs. Body weight loss ranged from 0.3 kg to 2.0 kg and was correlated with body volume decreases (r = 0.91) and energy expended (r = 0.73). Body volume changes were related to the extent of density increases (r = 0.58), changes in plasma volume (r = 0.53), and energy enpended (r = 0.75). The % delta PV was significantly related only to changes in body volume. The results of this study indicate that acute exercise does affect body volume and thus the density and % fat determinations. These changes do not parallel closely the changes in plasma volume. The data suggest that for absolute accuracy, the state of hydration of the subject should be controlled prior to hydrostatic weighing. However, even in dehydration caused by prolonged distance running, the density measurement error is small and nearly within the methodological error of the hydrostatic weighing technique.

Body Composition↗
PubMed1981

Validity of the Astrand-Ryhming nomogram for predicting maximal oxygen intake.

The purpose of this study was to evaluate the validity of the predicted VO2 max from the Astrand-Ryhming nomogram, using the cycle ergometer as the sole exercise mode and following the recommended submaximal test protocol. In addition, two sets of age correction factors were compared for accuracy. Using the Astrand age correction factors, the SEE of the predicted VO2 max for the 40 male subjects was .42 L.min-1 or 5.7 ml.kg-1.min-1, (r = .76 and .83, respectively); there was no significant difference between the measured and the predicted means. Although virtually identical SEE and r were found when applying the von Dobeln age correction factors, a significantly lower predicted mean was found (p less than .05), which indicated a consistent tendency to underestimate the actual VO2 max. These results suggest that the Astrand age correction factors should be used in conjunction with the Astrand-Ryhming nomogram, especially when classifying subjects into various fitness classifications.

Adolescent↗
PubMed1981

Isolation of mycobacteria inducing cross-reactions in the complement fixation test for Johne's disease.

Eight bulls which gave positive reactions in the complement fixation test for Johne's disease were identified in a group of 29 bulls which had previously given only negative reactions at repeated annual tests. One reacting bull was confirmed to be infected with Mycobacterium paratuberculosis at autopsy, but another reactor which was slaughtered had no visible lesions and mycobacteria were not recovered in culture. Faecal samples from seven further bulls (six reactors and one non-reactor) yielded mycobacteria which were not dependent on mycobactin for growth. When one of these strains was injected into two calves they developed positive reactions in the complement fixation test for Johne's disease and to intradermal skin testing with purified protein derivatives of M avium, M paratuberculosis and M bovis. The strains did not satisfy the exact requirements for classification into any recognised mycobacterial species.

Animals↗
PubMed1980

Human joint performance and the roughness of articular cartilage.

It is known that the surface of articular cartilage is rough and it has been suggested that this is likely to affect the lubrication of human joints. This paper describes the direct measurement of a cartilage surface with a stylus instrument. It is found that the height distribution is Gaussian with an inverse-square power spectrum. It is thus possible to calculate the elastic deflection of the surface under normal walking loads and it is shown that the mean separation of the cartilage surfaces in a human joint varies rather slowly with load. In one particular hip joint at heel strike the real area of contact was calculated to be about 1.3 cm2, the mean gap to be about 60 micrometers and the trapped volume to be about 80 percent of that when standing.

Adult↗
PubMed1980

Hydrostatic weighing at residual volume and functional residual capacity.

Hydrostatic weighing (HW) was performed at both residual volume (RV) and functional residual capacity (FRC) to determine if underwater weighing at different lung volumes affected the measurement of body density. Subjects were 43 males, 18-25 yr. Subjects were submerged in the prone position, and the lung volume was measured by helium dilution at the time of the underwater weighing. Underwater weight was first assessed at FRC followed by assessment at RV. Changes in lung volume were accurately reflected in the underwater weight. Body density (D) was not different with the use of the FRC (mean D = 1.0778) or RV (mean D = 1.0781) data. Percent fat values for the FRC and RV data were 9.3 +/- 5.4 and 9.2 +/- 5.1%, respectively, and were not statistically different. The results indicate that the difference between percent fat determinations by HW in the prone position at FRC and RV is negligible. Because measurement of underwater weight at FRC is more comfortable for the subject, this may be the method of choice when the lung volume can be measured during the underwater weighing.

Adolescent↗
PubMed1978

Fatty acid pattern and cholesterol in skeletal muscle of men aged 22 to 73.

In order to examine the relationship between fatty acid distribution of skeletal muscle membranes and age, a needle biopsy was performed on the vastus lateralis muscle of 20 healthy, non-obese males, ranging in age from 22 to 73 years. The muscle sample was homogenized, centrifuged at 100,000 x g, and the resulting pellet was saponified and acidified. The fatty acids and cholesterol were removed by a single hexane extraction and analyzed by gas--liquid chromatography with flame ionization detection. All subjects regardless of age had no consistent differences in the fatty acid profiles and cholesterol composition in the tissue. Correlation coefficients indicated no significant relationship between the age of the individual and any of the analyzed lipids. The results of this study indicated that aging may not be reflected by gross changes in the composition of structural lipids in the cell.

Adult↗
PubMed1978

A simple inexpensive method for estimating underwater weight.

A description is given of a simple, inexpensive and versatile method for estimating underwater weight. The use of a portable stock tank allows the determination of % Fat by underwater weighing without requiring a swimming pool, built-in tank, or special facility. Twenty-eight college students were weighed on two separate testing sessions 24-48 hours apart. Ten trials were performed at each session. The mean of the last five trials was used in determining underwater weight. The test-retest reliability coefficient was high, r = 0.98, and most of the successive trial correlations were above 0.99. The mean % Fat for the women (N = 9) was 22.2 +/- 5.9 and for the men (N = 19) was 13.7 +/- 5.1.

Adipose Tissue↗