Intensity of acute exercise does not affect serum leptin concentrations in young men

PURPOSE

We examined the effects of exercise intensity on serum leptin levels.

METHODS

Seven men (age = 27.0 yr; height = 178.3 cm; weight = 82.2 kg) were tested on a control (C) day and on 5 exercise days (EX). Subjects exercised (30 min) at the following intensities: 25% and 75% of the difference between the lactate threshold (LT) and rest (0.25 LT, 0.75 LT), at LT, and at 25% and 75% of the difference between LT and VO2peak (1.25 LT, 1.75 LT).

RESULTS

Kcal expended during the exercise bouts ranged from 150 +/- 11 kcal (0.25 LT) to 529 +/- 45 kcal (1.75 LT), whereas exercise + 3.5 h recovery kcal ranged from 310 +/- 14 kcal (0.25 LT) to 722 +/- 51 kcal (1.75 LT). Leptin area under the curve (AUC) (Q 10-min samples) for all six conditions (C + 5 Ex) was calculated for baseline (0700-0900 h) and for exercise + recovery (0900-1300 h). Leptin AUC for baseline ranged from 243 +/- 33 to 291 +/- 56 ng x mL(-1) x min; for exercise + recovery results ranged from 424 +/- 56 to 542 +/- 99 ng x mL(-1) x min. No differences were observed among conditions within either the baseline or exercise + recovery time frames. Regression analysis confirmed positive relationships between serum leptin concentrations and percentage body fat (r = 0.94) and fat mass (r = 0.93, P < 0.01).

CONCLUSION

We conclude that 30 min of acute exercise, at varying intensity of exercise and caloric expenditure, does not affect serum leptin concentrations during exercise or for the first 3.5 hours of recovery in healthy young men.

Impact of acute exercise intensity on pulsatile growth hormone release in men

To investigate the effects of exercise intensity on growth hormone (GH) release, 10 male subjects were tested on 6 randomly ordered occasions [1 control condition (C), 5 exercise conditions (Ex)]. Serum GH concentrations were measured in samples obtained at 10-min intervals between 0700 and 0900 (baseline) and 0900 and 1300 (exercise+ recovery). Integrated GH concentrations (IGHC) were calculated by trapezoidal reconstruction. During Ex subjects exercised for 30 min (0900-0930) at one of the following intensities [normalized to the lactate threshold (LT)]: 25 and 75% of the difference between LT and rest (0.25LT and 0.75LT, respectively), at LT, and at 25 and 75% of the difference between LT and peak (1.25LT and 1.75LT, respectively). No differences were observed among conditions for baseline IGHC. Exercise+recovery IGHC (mean +/- SE: C = 250 +/- 60; 0.25LT = 203 +/- 69; 0.75LT = 448 +/- 125; LT = 452 +/- 119; 1.25LT = 512 +/- 121; 1.75LT = 713 +/- 115 microg x l(-1) x min(-1)) increased linearly with increasing exercise intensity (P < 0.05). Deconvolution analysis revealed that increasing exercise intensity resulted in a linear increase in the mass of GH secreted per pulse and GH production rate [production rate increased from 16. 5 +/- 4.5 (C) to 32.1 +/- 5.2 microg x distribution volume(-1) x min(-1) (1.75LT), P < 0.05], with no changes in GH pulse frequency or half-life of elimination. We conclude that the GH secretory response to exercise is related to exercise intensity in a linear dose-response pattern in young men.

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.

Alcohol use and behaviors in women long-distance race participants reporting a history of bulimia and/or anorexia nervosa

OBJECTIVE

To describe the relationship between a reported a history of an eating disorder, a history of problem alcohol behavior and current alcohol consumption in women long-distance runners.

DESIGN

Survey.

SETTING

General community.

PARTICIPANTS

Women participating in a 20-mile road race (n = 398) and age-matched non-exercising women enrolled in a family practice health maintenance organization (n = 121) (mean age, 37.1 +/- 9.4 years).

INTERVENTION

Not applicable.

MEASURES

Responses to questions relating to 1) a past history of an eating disorder; 2) weight; 3) running and exercise habits; 4) drinking behaviors using alcoholism screening tests; 5) quantity-frequency data of the previous two week alcohol consumption.

RESULTS

Ten percent of racers and 4.1% of controls reported a history of an eating disorder. Those racers reporting a history of bulimia nervosa without anorexia were more likely to report feeling guilty about their drinking, drunk-driving arrests, an elevated score on an alcoholism screening test (suggestive of problem drinking), alcoholism, and seeking help for problem drinking than other racers or the control population without a history of an eating disorder. However, bulimic racers did not report either increased current alcohol consumption or occasions of drinking, including binge drinking (five or more drinks in one episode).

CONCLUSIONS

Women racers reporting a history of bulimia nervosa are more likely to report a history of problem behaviors with alcohol but not differences in current alcohol consumptions from that reported by other women racers or women without a history of an eating disorder from the control population.

Reported alcohol use and behavior in long-distance runners

Because alcohol may impair sports performance, we hypothesized there would be less drinking in serious recreational runners. We used mailed questionnaires to examine drinking patterns (2-wk quantity/frequency), scores on modified versions of the Michigan Alcoholism Screening Test (brief MAST [BMAST], short MAST [SMAST]), and parental history of problem drinking in 397 men and 144 women runners participating in a 20-mile race, compared with a nonexercising control population of 138 men and 119 women. A subset of 188 pairs (104 men, 84 women) were matched for gender, age, educational level, and marital status. We used chi-square analysis, paired t-test, and ANOVA. Male gender, running, and a family history for problem drinking predicted increased total alcohol consumption. We found that male runners (vs male controls) drank more 14.2 +/- 19.6 vs 5.4 +/- 7.6 drinks.wk-2, P = 0.004) and felt guilty about their drinking (26.6% vs 13.8%, P < 0.01). Men and women runners reported more occasions of drinking than matched controls (2.8 +/- 2.7 vs 2.0 +/- 2.3.wk-2, P = 0.004). Runners with scores on the BMAST (> or = 6) or SMAST (> or = 3) suggestive of a history of problem drinking drank less than controls with a similar score. Contrary to our hypothesis, running is associated with increased alcohol consumption, except in those who report a history of problem alcohol behavior.

Safety of a preadolescent basketball program

A preadolescent youth basketball program was prospectively studied to determine injury rates and the kinds of injuries sustained. The overall injury rate was 7.6% (39 injuries among the 510 children aged 5 to 12 years). Girls had a higher injury rate than boys (P less than .02). Only 12 children (2.4%) suffered significant injuries as defined by the inability to play for at least one session. Most injuries were contusions (35.9%), followed by strains or sprains (28.2%), epistaxis (12.8%), lacerations (5.1%), and one finger fracture (2.6%), the most significant injury. Games were more likely to produce injuries than practice sessions; most injuries occurred in the second half of game play. This study documents a low injury rate in an organized preadolescent basketball program.

Federal guidelines for marijuana screening should have lower cutoff levels. A comparison of results from immunoassays and gas chromatography-mass spectrometry

Federal guidelines for urine marijuana testing use a screening cutoff of 100 ng/mL and a confirming cutoff of 15 ng/mL. We tested 75 urine samples with two different immunoassays with cutoff points of 100 and 20 ng/mL. The same samples were also analyzed with gas chromatography-mass spectrometry. At the government recommended cutoff levels for screening and confirming, test sensitivity was 47% and specificity was 91%. With a screening cutoff of 20 ng/mL confirmed at 5 ng/mL, test sensitivity was 88% and specificity was 94%. We suggest adoption of these lower cutoff levels.

Early detection of bacteremia in an outpatient clinic

A total of 570 patients, aged less than 24 months, who were seen in the emergency room at Texas Children's Hospital for evaluation of acute febrile illness had a WBC count, differential count, and a blood culture obtained. Bacteremia occurred in 7.7% (n = 44) (22 Haemophilus influenzae; 17 Streptococcus pneumoniae; three Escherichia coli; one group B Streptococcus; one Staphylococcus aureus). The sensitivity, specificity, and positive predictive value of morphologic changes (vacuolization and toxic granulation) of polymorphonuclear neutrophils (segmented neutrophils plus band cells), WBC count greater than or equal to 15,000/microL and band cells greater than or equal to 500/microL were examined. Additionally, abnormalities in three of four tests (WBC count greater than or equal to 15,000/microL, band cells greater than or equal to 500/microL, segmented neutrophils greater than or equal to 10,000/microL, and/or total polymorphonuclear neutrophils greater than or equal to 10,500/microL) were evaluated. Morphologic changes of polymorphonuclear neutrophils were noted frequently in patients with culture-proven bacteremia (63% and 51% positive predictive value for vacuolization and toxic granulation, respectively) and were more predictive of bacterial infection than traditional tests. If both vacuolization and toxic granulation were present, the positive predictive value increased to 76%. Examination of the peripheral blood smear may provide important adjunctive information for the presence of bacteremia prior to bacteriologic confirmation.

Fluoride supplementation in Harris County, Texas

We sent questionnaires to 421 physicians in Harris County, Texas, to determine the use of oral fluoride supplementation. The response rate was 56%. Although 95% of the physicians practice in fluoride-deficient areas (less than 0.7 ppm), 36% of those responding stated that the fluoride content of the water was adequate; 25% were unsure. Of those who thought that the fluoride content was adequate, 79% stated that the actual fluoride content was less than 0.7 ppm or were unsure. Only 35% of the responding physicians prescribed fluoride, only 45% knew the correct dose. Only 50% of the responders made routine dental referrals in the 3- and 4-year age group. More physician education is needed to ensure oral fluoride supplementation in communities with inadequately fluoridated water supplies.