Biomedical subjects

J A Kanaley

Publications and source records attributed to J A Kanaley.

At least 19 recordsLinked to original sources

PubMed2006

Oral arginine attenuates the growth hormone response to resistance exercise.

This study investigated the combined effect of resistance exercise and arginine ingestion on spontaneous growth hormone (GH) release. Eight healthy male subjects were studied randomly on four separate occasions [placebo, arginine (Arg), placebo + exercise (Ex), arginine + exercise (Arg+Ex)]. Subjects had blood sampled every 10 min for 3.5 h. After baseline sampling (30 min), subjects ingested a 7-g dose of arginine or placebo (blinded, randomly assigned). On the exercise days, the subject performed 3 sets of 9 exercises, 10 repetitions at 80% one repetition maximum. Resting GH concentrations were similar on each study day. Integrated GH area under the curve was significantly higher on the Ex day (508.7 +/- 169.6 min.ng/ml; P < 0.05) than on any of the other study days. Arg+Ex (260.5 +/- 76.8 min.ng/ml) resulted in a greater response than the placebo day but not significantly greater than the Arg day. The GH half-life and half duration were not influenced by the stimulus administered. The GH secretory burst mass was larger, but not significantly, on the Arg, Ex, and Arg+Ex day than the placebo day. Endogenous GH production rate (Ex > Arg+Ex > Arg > placebo) was greater on the Ex and Arg+Ex day than on the placebo day (P < 0.05) but there were no differences between the Ex and Arg+Ex day. Oral arginine alone (7 g) stimulated GH release, but a greater GH response was seen with exercise alone. The combined effect of arginine before exercise attenuates the GH response. Autonegative feedback possibly causes a refractory period such that when the two stimuli are presented there will be suppression of the somatotrope.

Administration, Oral↗

PubMed2006

Regional differences in abdominal fat loss.

OBJECTIVE: This study determined if the magnetic resonance imaging (MRI) protocol used alters the estimation of change in abdominal fat with weight loss in obese type 2 diabetic women. This study also examined if there is a uniform fat loss across the abdomen. METHODS AND PROCEDURES: Thirty-three obese postmenopausal women with type 2 diabetes (age 50-70 years, body mass index>30 kg/m(2)) had a total abdominal MRI scan pre- and post weight loss intervention. Three different MRI analysis protocols were used and compared: a single slice at L(2)-L(3) vs five slices (centered at L(4)-L(5)) vs all abdominal slices. In addition, the total abdominal scan was divided into four regions (four slices each) with region 3 (critical region) including the traditionally studied L(2)-L(3), and regions 1 and 2 superior and region 4 inferior to critical region 3. Analysis of variance (ANOVA) with repeated measures was used to compare the influence of weight loss on abdominal fat measured both regionally and using the varying number of MR slices. RESULTS: At baseline, the ratio of visceral adipose tissue:subcutaneous adipose tissue (VAT:SAT) was significantly lower using the single-slice method compared to five slices and the total abdomen (P<0.01). Using the single-slice method, a lower %VAT was found than with the other methods (P<0.01). In regions 1, 2, 3, and 4, the absolute change in total fat was 122+/-50, 182+/-48, 182+/-55, and 155+/-40 cm(3), respectively. The regional difference in abdominal fat patterning revealed that the critical region (region 3) had a smaller VAT:SAT ratio than regions 1 and 2 (P<0.05), and the ratio at region 4 was smaller than region 3 (P<0.05). Weight loss resulted in a decrease in the VAT:SAT ratio (P<0.05) for regions 3 and 4 but not for regions 1 and 2. CONCLUSIONS: The number of MR slices analyzed yields differential result in relative VAT distribution. Regional differences in abdominal fat loss occur with a greater relative VAT loss in the critical region, thus if only the critical region is analyzed the overall VAT loss induced by weight loss intervention may be overestimated.

Abdominal Fat↗

PubMed2005

The effect of submaximal exercise on immuno- and bioassayable IGF-I activity in patients with GH-deficiency and healthy subjects.

OBJECTIVE: Growth hormone (GH) increases during exercise, but the response of the insulin-like growth factor (IGF) system has not been as definitive. Therefore, we investigated the effect of the exercise-induced GH response on the circulating IGF-system in GH-deficient (GHD) and intact adults. DESIGN: Eight GHD adults were studied on 2 occasions, with (+GH) and without (-GH) GH administered (0.4 IU) during exercise (45 min of cycle ergometer exercise at the lactate threshold). Eight age-matched controls were only studied on one occasion. Blood samples were drawn at baseline, during and post-exercise. IGFBP-3 proteolysis was measured by an in vitro proteolytic activity assay, IGF-I bioactivity by novel IGF-I kinase receptor activation assay (KIRA) and other hormones by immunoassay. RESULTS: GH administration to GHD adults resulted in a serum GH peak similar to the exercise-stimulated GH response in GH intact controls, but exercise had only a small impact on the IGF system. IGF-I concentration was lower in controls but was only significantly lower than the +GH day. Neither IGF-I nor -II levels changed over time. IGFBP-1 demonstrated a time effect (P<0.01) in all groups, and a time x group interaction (P<0.01) with a rise at 75 min post-exercise, which was greater in the GHD subjects than controls. IGFBP-2 and -3 increased significantly (P<0.01) over time in the GHD subjects, but not in the controls. No change in IGFBP-3 proteolysis or IGF-I bioactivity was found during exercise or recovery in either group. CONCLUSION: Submaximal exercise induced minor changes in IGFBP-1, -2 and -3, without affecting IGFBP-3 proteolysis and IGF-I bioavailability. Thus the metabolic status during submaximal exercise does not require a change in plasma IGF-I bioavailability. Administration of GH to GHD adults does not result in changes in proteolysis or bioavailability.

Adult↗

PubMed2005

Hormone-replacement therapy use, but not race, impacts the resting and exercise-induced GH response in postmenopausal women.

OBJECTIVE: This study examined the effect of hormone-replacement therapy (HRT) use on the incremental GH response to aerobic exercise in postmenopausal women and established whether racial differences in the GH response were seen at rest and in response to exercise. METHODS: 13 white (n = 6, HRT; n = 7, no HRT) and seven black women (no HRT) were studied on two occasions, a control day and an exercise day (30 min at 70% VO(2)max on a cycle ergometer). Blood was sampled every 10 min for a 4-h period and analyzed for GH using an ultrasensitive chemiluminescent assay. RESULTS: The mean 4-h GH concentration was higher on both study days in the HRT women than the non-HRT users. The integrated GH concentrations were greater in the HRT women both at rest and in response to exercise (rest, 352 +/- 53 min microg l(-1); exercise, 711 +/- 57 min microg l(-1); P < 0.01) than in the non-HRT women (rest, 157 +/- 87 min microg l(-1); exercise, 248 +/- 94 min microg l(-1)). The incremental GH response was greater in the HRT users than in the non-HRT women (358 +/- 130 versus 90.8 +/- 94 min microg l(-1), respectively; P < 0.05). GH-production rate during the 4-h period was greater in the HRT women than in the non-HRT women (P < 0.01), due to an increase in the GH mass secreted/pulse (P < 0.05), with no change in GH pulse number or GH half-life. No racial differences in the mean 4-h GH concentrations or integrated GH concentrations were found at rest or in response to exercise. CONCLUSION: HRT use resulted in a greater incremental exercise response compared with non-HRT users, due to changes in the secretory pulse characteristics in the HRT users. This study also demonstrated that no racial differences exist at rest and in response to exercise in the morning hours.

Bicycling↗

PubMed2004

Exercise is required for visceral fat loss in postmenopausal women with type 2 diabetes.

This study examined the effects of aerobic exercise without weight loss, a hypocaloric high monounsaturated fat diet, and diet plus exercise (D+E) on total abdominal and visceral fat loss in obese postmenopausal women with type 2 diabetes. Thirty-three postmenopausal women (body mass index, 34.6 +/- 1.9 kg/m(2)) were assigned to one of three interventions: a hypocaloric high monounsaturated fat diet alone, exercise alone (EX), and D+E for 14 wk. Aerobic capacity, body composition, abdominal fat distribution (magnetic resonance imaging), glucose tolerance, and insulin sensitivity were measured pre- and postintervention. Body weight ( approximately 4.5 kg) and percent body fat ( approximately 5%) were decreased (P < 0.05) with the D and D+E intervention, whereas only percent body fat ( approximately 2.3%) decreased with EX. Total abdominal fat and sc adipose tissue (SAT) were reduced with the D and D+E interventions (P < 0.05), whereas visceral adipose tissue (VAT) decreased with the D+E and EX intervention, but not with the D intervention. EX resulted in a reduction in total abdominal fat, VAT, and SAT (P < 0.05) despite the lack of weight loss. The reductions in total abdominal fat and SAT explained 32.7% and 9.7%, respectively, of the variability in the changes in fasting glucose levels, whereas the reductions in VAT explained 15.9% of the changes in fasting insulin levels (P < 0.05). In conclusion, modest weight loss, through either D or D+E, resulted in similar improvements in total abdominal fat, SAT, and glycemic status in postmenopausal women with type 2 diabetes; however, the addition of exercise to diet is necessary for VAT loss. These data demonstrate the importance of exercise in the treatment of women with type 2 diabetes.

Adipose Tissue↗

PubMed2004

Influence of resistance exercise training on glucose control in women with type 2 diabetes.

The objective of the study was to evaluate the effects of acute and chronic resistance training on glucose and insulin responses to a glucose load in women with type 2 diabetes. Subjects consisted of type 2 diabetic women (n = 7) and age-matched controls (n = 8) with normal glucose tolerance. All subjects participated in 3 oral glucose tolerance tests: pretraining, 12 to 24 hours after the first exercise session (acute) and 60 to 72 hours after the final training session (chronic). Exercise training consisted of a whole body resistance exercise program using weight-lifting machines 3 days per week for 6 weeks. Resistance training was effective in increasing strength of all muscle groups in all subjects. Integrated glucose concentration expressed as area under the curve (AUC) was 3,355.0 +/- 324.6 mmol/L. min pretraining, improved significantly (P <.01) after the acute bout of exercise (2,868 +/- 324.0 mmol/L. min), but was not improved with chronic training (3,206.0 +/- 337.0 mmol/L. min) in diabetic subjects. A similar pattern of significance was observed with peak glucose concentration (pre: 20.2 +/-1.4 mmol/L; acute: 17.2 +/- 1.7 mmol/L; chronic: 19.9 +/- 1.7 mmol/L). There were no significant changes in insulin concentrations after any exercise bout in the diabetic subjects. There were no changes in glucose or insulin levels in control subjects. An acute bout of resistance exercise was effective in improving integrated glucose concentration, including reducing peak glucose concentrations in women with type 2 diabetes, but not age-matched controls. There were no significant changes in insulin concentrations for either group. Resistance exercise offers an alternative to aerobic exercise for improving glucose control in diabetic patients. To realize optimal glucose control benefits, individuals must follow a regular schedule that includes daily exercise.

Adult↗

PubMed2003

Adrenocortical responses to submaximal exercise in postmenopausal black and white women.

The purpose of this study was to determine whether racial differences exist in the dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEAS), and cortisol concentrations of black and white postmenopausal women at rest and in response to submaximal exercise. Twenty-three postmenopausal women (13 white and 10 black) were studied on 2 occasions. On one occasion subjects rested quietly for 4 hours (control day), whereas on the other occasion after 50 minutes of rest, subjects exercised at 70% of Vo(2) peak for 30 minutes on a cycle ergometer (exercise day). Blood was sampled at rest, during exercise, and during recovery and assayed for DHEA, DHEAS, and cortisol concentrations. Resting DHEA and cortisol concentrations and integrated area under the curve (AUC) were similar between the black and white women; however, the black women had lower resting DHEAS concentrations compared with the white women (DHEAS, black: 1.32 +/- 0.29 v white: 2.18 +/- 0.25 micromol. L(-1), P <.05). Regardless of race, DHEA and cortisol AUC increased significantly above resting values (P <.01), but the exercise AUC for DHEA and cortisol were not different between the black and white women (DHEA: 607 +/- 133 and 824 +/- 108 min x nmol. L(-1); cortisol: 9,604 +/- 1,247 and 8,076 +/- 1,093 min x nmol. L(-1), respectively). No exercise-induced change in integrated DHEAS AUC was found in either group. In conclusion, racial differences exist in the resting DHEAS levels of postmenopausal women, but with no racial differences in resting DHEA and cortisol concentrations. Race had no impact on these adrenal hormone responses to submaximal exercise.

Adipose Tissue↗

PubMed2003

Racial differences in subcutaneous and visceral fat distribution in postmenopausal black and white women.

Most studies examining racial disparities in abdominal fat distribution have focused on premenopausal women. The purpose of this report was to determine if racial differences exist in the abdominal fat distribution in postmenopausal white and black women. Fifty-four women (33 white and 21 black) were scanned by magnetic resonance imaging (MRI) to determine abdominal fat distribution, were measured by hydrostatic weighing for percent body fat, and had their fasting blood lipids, glucose, and insulin levels measured. These women were matched for age (mean age, 53.5 +/- 0.9 years) and percent body fat (black: 39.6% +/- 2.3%, white: 37.3% +/- 1.2%). When adjusted for total body fat mass and hormone replacement therapy (HRT), total abdominal fat (white: 10,352.1 +/- 535.2, black: 11,220.4 +/- 670.1 cm(3)) was not statistically different between groups, but the visceral fat content was significantly higher in the white women (white: 2,943.5 +/- 220.4, black: 2,332.6 +/- 176.1 cm(3)). The percent visceral fat was also higher in these women (white: 30.5% +/- 1.3%, black: 22.1% +/- 1.6%, P <.01). Subcutaneous adipose tissue (SAT) was significantly higher in the black women (white: 7,408.6 +/- 450.2, black: 8,887 +/- 563.1 cm(3), P <.05). No significant differences were found in the insulin concentrations or the blood lipid profile of these women. Regardless of race, visceral fat was a significant predictor of log triglyceride, low-density lipoprotein-cholesterol (LDL-C), cholesterol/LDL-C, insulin levels, and insulin resistance. Race was only found to contribute to 8% of the variability of LDL-C. HRT use had no effect on abdominal fat distribution or the blood lipid profile in this cohort of women. In conclusion, disparities in abdominal fat distribution between black and white women continue to exist in the early postmenopausal years, and the regression results indicate that the absolute amount of visceral fat, and not the relative amounts of visceral fat, is the best predictor of the blood lipid profile and insulin sensitivity. HRT use did not result in differences in abdominal fat distribution in these women. Factors, such as genetics and lifestyle, must play a larger role in explaining the increased health risk in black women.

Abdomen↗

PubMed2002

Dose related association of impact activity and bone mineral density in pre-pubertal girls.

Impact activity is an important contributor to bone accrual. Children engaging in such activity have been shown to have greater bone mineral density (BMD) than their peers. This cross-sectional study was designed to quantify the association between BMD and impact activity in pre-pubescent girls, specifically examining for a dose-dependent relationship. Fifty 7-11-year-old Caucasian female gymnasts were grouped by hours of gymnastics participation during a 6-month period: LOW, 1-8 hours/week (hrs/wk); HIGH, >8 hrs/wk. They were compared with 20 controls, with height, weight, age, and Tanner stage averages matched to the gymnasts. Total body, forearm, hip, lumbar spine BMD, and body composition were measured by dual energy X-ray absorptiometry (DXA). Strength was measured by one repetition maximum testing, calcium intake was quantified by questionnaire, and physical activity was measured by questionnaire and activity monitors. Total and regional BMD were greater in the HIGH group than the controls (P<0.05). Furthermore, both total and forearm BMD were greater in the HIGH group than in the LOW group, and greater in the LOW group than in the controls (P<0.05). Simple regression analysis between hrs/wk of gymnastics activity versus total and regional BMD (using maturation-adjusted Z scores) yielded a positive slope for each site. R2 was greatest for hip BMD (R2 = 0.25), and least for lumbar spine (R2 = 0.10) (P<0.0001). In conclusion, in this group of pre-pubescent girls, we observed a dose-dependent relationship between BMD and hrs/wk of impact activity; even moderate doses of impact activity were associated with increased BMD.

Bone Density↗

PubMed2001

Substrate oxidation during acute exercise and with exercise training in lean and obese women.

The purpose of this study was to examine the rates of substrate oxidation in lean and obese women during short-duration, high-intensity exercise and to examine the effects of a 16-week exercise training program on substrate oxidation during 30 min of exercise in lean and obese individuals. Fat and carbohydrate oxidation were measured in 8 non-obese (Non-Ob), 11 lower-body obese (LBO) and 12 upper-body obese (UBO) women at rest and during 30 min of treadmill exercise at 70% of peak oxygen uptake. The obese women participated in 16 weeks of aerobic training (3 times per week at 70% of maximum oxygen uptake). Total fat and carbohydrate oxidation were measured using indirect calorimetry. The respiratory exchange ratio (R) was similar between groups at rest and was found to decrease throughout the exercise session (P< 0.01). Fat oxidation was greater at 15 min of exercise than at rest (P<0.01) but did not increase significantly more at 30 min of exercise. Obese women had significantly greater fat oxidation (both absolute concentrations and when expressed per kg of fat free mass, FFM) at 30 min of exercise than the Non-Ob women [Non-Ob 23.5 (3.7) micromol.kg FFM(-1).min(-1), LBO 35.2 (3.1) micromol.kg FFM(-1).min(-1), UBO 33.2 (2.6) micromol.kg FFM(-1).min(-1); P<0.01]. Carbohydrate oxidation also increased (P < 0.01) in response to exercise, but no group differences were found. The pattern of fat distribution (LBO vs UBO) did not affect the resting or exercise fat oxidation (P=NS). Sixteen weeks of aerobic exercise did not result in significant changes in resting or exercise fat oxidation in the obese women (n = 10; P=NS), but did significantly increase carbohydrate oxidation [pretraining 8.6 (1.4) micromol.kg FFM(-1), post-training 13.6 (2.1) micromol.kg FFM(-1).min(-1); P<0.01]. Unlike earlier studies, this shorter-duration, higher-intensity exercise resulted in a greater whole-body fat oxidation in the obese women than in the Non-Ob women, and exercise training did not result in any changes in fat oxidation, but did increase exercise carbohydrate oxidation.

Abdomen↗

PubMed2001

Resting leptin responses to acute and chronic resistance training in type 2 diabetic men and women.

PURPOSE: To evaluate the plasma leptin levels approximately 24 h post-exercise in control and type 2 diabetic subjects and to establish if observed changes in leptin concentrations were acute or chronic effects of a resistance training program. METHODS: Thirty men and women (17 controls and 13 type 2, obese diabetics, age 40-55 y) had resting blood samples drawn at 08:00 h (12 h postprandial) at the beginning of the study (pre-training), 24 h after a three repetition maximal weight lifting bout (acute) and 72 h after their last training bout of 6 weeks of resistance training (chronic). The two groups were not matched with respect to body mass index and the control subjects were not normal weight. Subjects weight-trained three times a week, for 6 weeks, for 1 h, training both the upper and lower body. RESULTS: Serum leptin concentrations were significantly higher in the type 2 diabetics than in the control group at pre-training (41.4+/-8.9 vs 11.4+/-3.0 ng/ml, P<0.05, respectively). Compared to pre-training, the leptin levels decreased significantly (P<0.01) after acute exercise in the diabetics but not in the control subjects (diabetics 30.9+/-7.1 vs controls 10.6+/-2.6 ng/ml). Approximately 72 h after 6 weeks of exercise training, the leptin concentrations were no longer lower than the pre-training values in either group (36.9+/-8.8 vs 11.9+/-8.8 ng/ml, respectively, P=NS). When leptin concentrations were log transformed and adjusted for fat mass there were still significant changes in leptin levels over time and between the control and diabetic group (P<0.05). CONCLUSIONS: The type 2 diabetics showed a significant 30% reduction in resting leptin levels 24 h after a single bout of resistance exercise. This was an acute response to resistance exercise and not a chronic training effect (no difference between pre-training and chronic). The decreased resting leptin concentrations approximately 24 h post-acute exercise may be due to reduced glucose availability to the adipose tissue, particularly in the diabetic subjects. There is no chronic effect of resistance exercise on leptin concentrations.

Adipose Tissue↗

PubMed2001

Abdominal fat distribution in pre- and postmenopausal women: The impact of physical activity, age, and menopausal status.

Age-related increases in total body fat have been reported, but the impact of menopause on abdominal fat distribution is still unclear. The purpose of this study was to determine the impact of menopausal status on abdominal fat distribution using magnetic resonance imaging (MRI). In addition, we investigated the influence of abdominal fat distribution on blood lipid profiles and leptin concentrations. Twenty-three premenopausal (PRE), 27 postmenopausal (POST), and 28 postmenopausal women on estrogen replacement therapy (ERT) had measurements of regional abdominal fat, blood lipids, and serum leptin concentrations. The women were matched for body mass index (BMI) and total body fat mass. Age and menopausal status were not found to be significant predictors of total abdominal fat, visceral fat, or subcutaneous fat, while physical activity was a significant predictor (P <.01) for total abdominal fat (R(2) =.16), visceral fat (R(2) =.32) and percent visceral fat (R(2) =.25). There was a trend for a greater visceral fat content in the POST women compared with the PRE women (2,495.0 +/- 228.4 v 1,770.4 +/- 240.8 cm(2), respectively, P =.06). The percent visceral abdominal fat was significantly lower (P <.05) in the premenopausal women than in either postmenopausal group (PRE, 23.2% +/- 1.7%; POST, 28.9% +/- 1.8%; ERT, 28.9% +/- 1.6%). Menopausal status and age did not influence any of the blood lipid values. Abdominal fat distribution was a significant predictor of cholesterol concentrations and the cholesterol/high-density lipoprotein-cholesterol (HDL-C) ratio, but only accounted for approximately 15% of the variability in these levels. Total body fat and physical activity accounted for 47% of the variability in leptin concentrations, while abdominal fat distribution, age, and menopausal status were not significant predictors. In conclusion, in early postmenopausal women, the level of physical activity accounts for the variability in abdominal fat distribution observed, while menopausal status and age do not play a significant role. ERT was not associated with additional benefits in abdominal fat distribution compared with postmenopausal women not on ERT or in the blood lipid profile in these women.

Abdomen↗

PubMed2001

Cortisol and growth hormone responses to exercise at different times of day.

Exercise of appropriate intensity is a potent stimulus for GH and cortisol secretion. Circadian and diurnal rhythms may modulate the GH and cortisol responses to exercise, but nutrition, sleep, prior exercise patterns, and body composition are potentially confounding factors. To determine the influence of the time of day on the GH and cortisol response to acute exercise, we studied 10 moderately trained young men (24.1 +/- 1.1 yr old; maximal oxygen consumption, 47.9 +/- 1.4 mL/kg.min; percent body fat, 13.2 +/- 0.6%). After a supervised night of sleep and a standard meal 12 h before exercise, subjects exercised at a constant velocity (to elicit an initial blood lactate concentration of approximately 2.5 mmol/L) on a treadmill for 30 min on 3 separate occasions, starting at 0700, 1900, and 2400 h. Blood samples were obtained at 5-min intervals for 1 h before and 5 h after the start of exercise; subjects were not allowed to sleep during this period. Subjects were also studied on 3 control days under identical conditions without exercise. There were no significant differences with time of day in the mean blood lactate and submaximal oxygen consumption values during exercise. The differences over time in serum GH and cortisol concentrations between the exercise day and the control day were determined with 95% confidence limits for each time of day. Exercise stimulated a significant increase in serum GH concentrations over control day values for approximately 105--145 min (P < 0.05) with no significant difference in the magnitude of this response by time of day. The increase in serum GH concentrations with exercise was followed by a transient suppression of GH release (for approximately 55--90 min; P < 0.05) after exercise at 0700 and 1900 h, but not at 2400 h. Although the duration of the increase in serum cortisol concentrations after exercise was similar (approximately 150--155 min; P < 0.05) at 0700, 1900, and 2400 h, the magnitude of this increase over control day levels was greatest at 2400 h. This difference was significant for approximately 130 min and approximately 40 min compared to exercise at 1900 and 0700 h, respectively (P < 0.05). The cortisol response to exercise at 0700 h was significantly greater than that at 1900 h for about 55 min (P < 0.05). A rebound suppression of cortisol release for about 50 min (P < 0.05) was observed after exercise at 2400 h, but not 0700 or 1900 h. Both baseline (before exercise) and peak cortisol concentrations were significantly higher at 0700 h than at 1900 or 2400 h (P < 0.01). We conclude that time of day does not alter the GH response to exercise; however, the exercise-induced cortisol response is modulated by time of day.

Adult↗

PubMed1999

Validity of methods of body composition assessment in young and older men and women.

We examined the validity of percent body fat (%Fat) estimation by two-compartment (2-Comp) hydrostatic weighing (Siri 2-Comp), 3-Comp dual-energy X-ray absorptiometry (DEXA 3-Comp), 3-Comp hydrostatic weighing corrected for the total body water (Siri 3-Comp), and anthropometric methods in young and older individuals (n = 78). A 4-Comp model of body composition served as the criterion measure of %Fat (Heymsfield 4-Comp; S. B. Heymsfield, S. Lichtman, R. N. Baumgartner, J. Wang, Y. Kamen, A. Aliprantis, and R. N. Pierson Jr., Am. J. Clin. Nutr. 52: 52-58, 1990.). Comparison of the Siri 3-Comp with the Heymsfield 4-Comp model revealed mean differences of </=0.4 %Fat, r values >/= r = 0.997, total error values </= 0.85 %Fat, and 95% confidence intervals (Bland-Altman analysis) of </=1.7 %Fat. Comparison of Siri 2-Comp, DEXA, and anthropometric models with the Heymsfield 4-Comp revealed that total error scores ranged from +/-4. 0 to +/-10.7 %Fat, and 95% confidence intervals associated with the Bland-Altman analysis ranged from +/-5.1 to +/-15.0 %Fat. We conclude that the Siri 3-Comp model provides valid and accurate body composition data when compared with a 4-Comp criterion model. However, the individual variability associated with the Siri 2-Comp, DEXA 3-Comp, and anthropometric models may limit their use in research settings. The use of anthropometric estimation methods resulted in large mean differences and a considerable amount of interindividual variability. These data suggest that the use of these techniques should be viewed with caution.

Absorptiometry, Photon↗

PubMed1999

Obesity attenuates the growth hormone response to exercise.

Resting serum GH concentrations are decreased in obesity. In nonobese (NonOb) individuals, acute exercise of sufficient intensity increases GH levels; however, conflicting data exist concerning the GH response to exercise in obese individuals. To examine the exercise-induced GH response in obese individuals, we studied 8 NonOb, 11 lower body obese (LBO), and 12 upper body obese (UBO) women before, during, and after 30 min (0800-0830 h) of treadmill exercise at 70% oxygen consumption peak. Blood samples were taken every 5 min (0700-1300 h) and were analyzed for GH concentrations with a sensitive (0.002 microg/L) chemiluminescence assay. The impact of 16 weeks of aerobic exercise training on the GH response to exercise was also examined in the obese women. In response to exercise, the 6-h integrated GH concentration was significantly greater (P < 0.05) in the NonOb women (1006 +/- 220 min/microg x L) than in either of the obese groups (LBO, 435 +/- 136; UBO, 189 +/- 26 min/microg x L). No differences were found between the LBO and UBO women. The increased integrated GH concentrations could be accounted for by a greater 6-h GH production rate [micrograms per L distribution volume (Lv)] in the NonOb women than in either of the obese groups (NonOb, 45.6 +/- 12.3; LBO, 16.9 +/- 1.2; UBO, 8.7 +/- 0.64 microg/Lv; P < 0.05). This increase was attributed to a greater mass of GH secreted per pulse in the NonOb women (NonOb, 10.8 +/- 2.5; LBO, 4.9 +/- 0.8; UBO, 4.0 +/- 0.5 microg/Lv; P < 0.05, NonOb vs. both obese groups). After 16 weeks of aerobic training, maximal oxygen consumption increased from 44.7 +/- 2.2 to 48.5 +/- 1.9 mL/kg fat-free mass x min; P < 0.05), but no significant change in body composition occurred in the 10 obese women who completed the training. No change was observed in the GH response to exercise after training (n = 10; pre, 379 +/- 144; post, 350 +/- 55 min/microg x L). In conclusion, the GH response to exercise was attenuated in the obese women compared to NonOb women. Short term aerobic training improved fitness, but did not increase the GH response to exercise.

Body Composition↗

PubMed1998

Repeated bouts of exercise alter the blood lactate-RPE relation.

PURPOSE: To examine the effects of repeated bouts of exercise on the blood lactate [HLa]-ratings of perceived exertion (RPE) relation. METHODS: Six moderately trained males were studied on two occasions: a sequential exercise bouts day (SEB: 1000 h, 1130 h, and 1300 h) and a delayed exercise bouts day (DEB: 1000 h, 1400 h, and 1800 h). Each of the three exercise bouts within a given condition were 30 min in duration at the power output (PO) associated with 70% of VO2peak on a cycle ergometer. A standardized meal was provided at 0600 h. VO2, PO, HR, and RER were recorded every min during exercise and blood [HLa] and RPE were measured every 5 min during exercise. RESULTS: A 2 x 3 analysis of variance with repeated measures revealed that blood [HLa] decreased significantly with each repeated exercise bout (X +/- SEM: bout 1: SEB = 3.5 (0.3), DEB = 3.8 (0.4); bout 2: SEB = 2.6 (0.3), DEB = 2.8 (0.3); bout 3: SEB = 2.0 (0.2), DEB = 2.1 (0.4); mM). No differences were observed in the blood [HLa] response to repeated bouts of exercise between SEB and DEB. RPE-peripheral (legs, RPE-L) was higher during bout 3 compared with bout 1 (P <0.05) (bout 1: SEB = 11.8 (0.8), DEB = 12.3 (0.2); bout 2: SEB = 12.3 (0.5), DEB = 13.3 (0.4); bout 3: SEB = 13.5 (0.8), DEB = 14.0 (0.7); RPE-central (chest and breathing, RPE-C) was not affected by repeated bouts of exercise, whereas RPE-Overall (RPE-O) was higher during bout 3 compared with bouts 1 and 2 (P < 0.05) (bout 1: SEB = 12.5 (0.2), DEB = 12.3 (0.4); bout 2: SEB = 12.8 (0.4), DEB = 12.7 (0.4); bout 3: SEB = 13.7 (0.7), DEB = 13.2 (0.3)). No interaction for RPE x condition was observed. HR increased with repeated bouts of exercise with HR during exercise bout 3 being higher than HR during exercise bout 1 (164 vs. 156 bpm, P < 0.05). There was also a strong trend for HR during exercise bout 3 to be higher than HR during exercise bout 2 (P < 0.06). A trend for a reduction in VO2 with repeated exercise was observed (P < 0.07), with the reduction apparently related to the SEB condition (P < 0.12 for VO2 x condition). PO and kcal.min-1 were not affected by repeated bouts of exercise. RER decreased significantly with each repeated bout of exercise (from RER = 0.96 to RER = 0.89, P < 0.05) with no difference observed between SEB and DEB. CONCLUSIONS: We conclude that the blood [HLa]-RPE relation is altered by repeated bouts of exercise and that this alteration does not appear to be affected by recovery time between exercise bouts (up to 3.5 h of recovery). These data suggest that, after the first exercise bout, RPE should not be used to produce a specific blood [HLa] on subsequent exercise bouts.

Adult↗

PubMed1997

Human growth hormone response to repeated bouts of aerobic exercise.

We examined whether repeated bouts of exercise could override growth hormone (GH) auto-negative feedback. Seven moderately trained men were studied on three occasions: a control day (C), a sequential exercise day (SEB; at 1000, 1130, and 1300), and a delayed exercise day (DEB; at 1000, 1400, and 1800). The duration of each exercise bout was 30 min at 70% maximal O2 consumption (VO2max) on a cycle ergometer. Standard meals were provided at 0600 and 2200. GH was measured every 5-10 min for 24 h (0800-0800). Daytime (0800-2200) integrated GH concentrations were approximately 150-160% greater during SEB and DEB than during C: 1,282 +/- 345, 3,192 +/- 669, and 3,389 +/- 991 min.microgram.l-1 for C, SEB, and DEB, respectively [SEB > C (P < 0.06), DEB > C (P < 0.03)]. There were no differences in GH release during sleep (2300-0700). Deconvolution analysis revealed that the increase in 14-h integrated GH concentration on DEB was accounted for by an increase in the mass of GH secreted per pulse (per liter of distribution volume, lv): 7.0 +/- 2.9 and 15.9 +/- 2.6 micrograms/lv for C and DEB, respectively (P < 0.01). Comparison of 1.5-h integrated GH concentrations on the SEB and DEB days (30 min exercise + 60 min recovery) revealed that, with each subsequent exercise bout, GH release apparently increased progressively, with a slightly greater increase on the DEB day [SEB vs. DEB: 497 +/- 162 vs. 407 +/- 166 (bout 1), 566 +/- 152 vs. 854 +/- 184 (bout 2), and 633 +/- 149 vs. 1,030 +/- 352 min.microgram.l-1 (bout 3), P < 0.05]. We conclude that the GH response to acute aerobic exercise is augmented with repeated bouts of exercise.

Adult↗

PubMed1995

Measurement of abdominal and visceral fat with computed tomography and dual-energy x-ray absorptiometry.

These studies were undertaken to compare dual-energy x-ray absorptiometry (DXA) and computed tomography (CT) measurements of abdominal fat and to determine whether anthropometry could be combined with DXA to predict intraabdominal (visceral) fat mass in humans. Twenty-one volunteers underwent abdominal CT scans, DXA, and anthropometry. DXA- and CT-measured total abdominal fat were similar (8448 +/- 5005 and 8066 +/- 5354 mL, respectively; NS) and were highly correlated (r = 0.985, P < 0.001). The combination of anthropometry and DXA was a suboptimal predictor of CT-measured intraabdominal fat (r = 0.61, P < 0.05); however, the combination of a single CT slice (to assess the ratio of intraabdominal to total abdominal adipose tissue) and DXA-measured abdominal fat was an excellent predictor of CT-measured intraabdominal fat (r = 0.98, P < 0.001). We conclude that a single-slice CT scan (or other imaging technique) with or without DXA is required for accurate predictions of intraabdominal fat.

Absorptiometry, Photon↗