Female Distance Runners Training In Southeastern United States Have Adequate Vitamin D Status.

BACKGROUND: High rates of vitamin D deficiency have been reported in athletes. The purpose of this study was to evaluate the associations between vitamin D with bone health and parathyroid hormone (PTH) concentrations in female runners who trained at 30.4° degrees north. METHODS: Serum 25-hydroxyvitamin D (25(OH) D), PTH, body composition, and bone mineral density (BMD) were measured in 59 female runners, aged 18-40 years. Stress fracture history, training duration and frequency were evaluated by questionnaire. As per National Endocrine Society cut-offs, serum vitamin D ranges were: 25(OH)D < 50 nmol/L for deficient; 50-75 nmol/L for insufficient; and ≥ 75 nmol/L for sufficient status. RESULTS: Mean serum 25(OH)D concentrations were 122.6 ± 63.9 nmol/L, with 18.6% of subjects in the deficient (5.1%) or insufficient (13.5%) range. No significant differences were observed between sufficient and deficient/insufficient subjects for BMD, PTH, history of stress fractures, or demographic data. CONCLUSIONS: The majority of distance runners maintained sufficient vitamin D status, suggesting that training outdoors in latitude where vitamin D synthesis occurs year-round reduces the risk for vitamin D deficiency. Data do not support the indiscriminate supplementation of outdoor athletes in southern latitudes without prior screening.

Dietary and training predictors of stress fractures in female runners.

PURPOSE: To compare female runners with and without a history of stress fractures to determine possible predictors of such fractures. METHODS: 27 female runners (age 18-40 yr) who had had at least 1 stress fracture were matched to a control sample of 32 female runners without a history of stress fractures. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (iDXA). Subjects answered questionnaires on stress-fracture history, training, menstrual status, and diet. RESULTS: No significant differences were found in menstrual characteristics, diet and dairy intake, or bone measurements. Weekly servings of milk during middle school significantly predicted BMD at the femur (p = .010), femoral neck (p = .002), Ward's triangle (p = .014), and femoral shaft (p = .005). Number of menstrual cycles in the previous year predicted femoral-neck BMD (p = .004). Caffeine intake was negatively associated with BMD of the femur (p = .010), femoral neck (p = .003), trochanter (p = .038), and femoral shaft (p = .035). Weekly hours of training were negatively associated with total-body BMD (p = .021), total-body bone mineral content (p = .028), and lumbar-spine BMD (p = .011). Predictors for stress fractures included the number of years running, predominantly running on hard ground, irregular menstrual history, low total-body BMD, and low current dietary calcium intake when controlling for body-mass index (Nagelkerke R2 = .364). CONCLUSIONS: Servings of milk during middle-school years were positively correlated with hip BMD, although current calcium intake, low BMD, irregular menstrual history, hard training surface, and long history of training duration were the most important predictors of stress fractures.

The effects of acute exercise bouts on hepcidin in women.

PURPOSE: To investigate the effects of acute exercise on serum hepcidin and iron (sFe) in active women. Changes in interleukin-6 (IL-6), hepcidin, ferritin, and sFe in response to 2 different exercise durations were compared. METHODS: Twelve women age 19-32 yr performed 2 treadmill runs (60 and 120 min) at 65% of VO2max. Blood samples were obtained before, immediately after, and 3, 6, 9, and 24 hr after exercise. Two-way repeated-measures ANOVA was conducted to examine changes in measured variables. Significance was accepted at p < .05. RESULTS: Significant effects for trial were observed for hepcidin (60 min: 1.15 ± 0.48 nmol/L; 120 min: 2.28 ± 1.44 nmol/L) and for time, with hepcidin significantly increased 3 hr postexercise in both trials (60 min: 3 hr - 1.99 ± 2.00 nmol/L; 120 min: 3 hr - 4.60 ± 4.61 nmol/L). Significant main effects for time occurred for sFe, ferritin, and IL-6. sFe was significantly decreased 9 hr postexercise compared with 3 and 24 hr postexercise. IL-6 was significantly increased immediately postexercise. CONCLUSIONS: Both runs resulted in significant increases in hepcidin 3 hr after exercise. Increases in hepcidin were preceded by significant increases in IL-6 immediately postexercise and followed by significant decreases in sFe 9 hr postexercise. It was concluded that endurance exercise increases the production of hepcidin, which affects sFe. The 2-hr exercise bout stimulated greater changes in serum hepcidin than the 1-hr bout.

Branched-chain amino acid supplementation lowers perceived exertion but does not affect performance in untrained males.

The purpose of this study was to determine whether branched-chain amino acid (BCAA) supplementation affects aerobic performance, ratings of perceived exertion (RPE), or substrate utilization as compared with an isocaloric, carbohydrate (CHO) beverage or a noncaloric placebo (PLAC) beverage. Nine untrained males performed three 90-minute cycling bouts at 55% VO2 peak followed by 15-minute time trials. Subjects, who were blinded to beverage selection, ingested a total of 200 kcal via the CHO or BCAA beverage before and at 60 minutes of exercise or the PLAC beverage on the same time course. RPE and metabolic measurements were taken every 15 minutes during steady-state exercise, and each of the trials was separated by 8 weeks. Plasma glucose and BCAA concentrations were measured pre- and post-exercise. A greater distance (4.6 ± 0.6 km) was traveled in the time-trial during the CHO trial than the PLAC trial (3.9 ± 0.4 km) (p < 0.05). There was no difference between the BCAA (4.4 ± 0.5 km) and PLAC trials. RPE was reduced at the 75-minute and 90-minute mark during the BCAA trial as compared with the PLAC trial. There were no significant differences found for the trial vs. time interaction in regard to respiratory exchange ratio. Thus, CHO supplementation improves performance in a loaded time-trial as compared with a PLAC beverage. BCAA supplementation, although effective at increasing blood concentrations of BCAA, did not influence aerobic performance but did attenuate RPE as compared with a PLAC beverage.

Residential context, walking and obesity: two African-American neighborhoods compared.

We compare walking and obesity rates in two African-American neighborhoods that are similar in urban form but different in level of neighborhood disadvantage. We find higher rates of utilitarian walking in the neighborhood with higher density and disadvantage and more destinations within walking distance. However levels of leisure walking and physical activity were not higher, and rates of obesity were not lower in the non-poor neighborhood with better maintenance, more sidewalks and recreational facilities. Different types of barriers to physical activity reported in the two neighborhoods and the high rates of overweight and obesity in both may explain the findings.

Effects of a 12-month pedometer walking program on gait, body mass index, and lower extremity function in obese women.

This study evaluated the effects of a self-reported pedometer-walking program on gait, lower extremity function, and Body Mass Index for 33 obese women, ages 31-65 years (M = 48.0, SD = 8.0) and whose initial average Body Mass Index was 40.30 +/- 9.60 kg/m2. During the 12-mo. intervention participants wore pedometers and reported the number of daily steps walked. Body Mass Index, three gait parameters, steps/day, and lower extremity function were taken over 3-mo. intervals. All participants increased in gait velocity, % single-leg support, and lower extremity function, and decreased in Body Mass Index over time. Those whose steps/day increased by 2000 over 6 mo. had significantly faster velocities and longer step lengths than those whose steps/day did not increase. The 1-yr. walking program stimulated changes in gait, Body Mass Index, and lower extremity function for these obese women. Ultimately, these changes may reduce the risk of falls for this group of women.

No effect of moderate hypohydration or hyperthermia on anaerobic exercise performance.

PURPOSE: This study examined the effects of hypohydration and moderate hyperthermia (core temperature elevation) on anaerobic exercise performance in a temperate environment. METHODS: Eight active males completed two passive heat exposure trials (180 min, 45 degrees C, 50% rh) with (EUH) and without (HYP) fluid replacement. A single 15-s Wingate anaerobic test (WAnT) was used to assess anaerobic performance (peak power, mean power, and fatigue index) before (-180 min) and again at three time points after passive heat exposure to include immediately (0 min), 30 min, and 60 min after in a temperate environment (22 degrees C). Rectal temperature (Tc) was measured throughout the experiment. RESULTS: HYP reduced body mass (2.7+/-0.7%) (P<0.05) but had no effect on any WAnT performance measure. Passive heat exposure elicited moderate hyperthermia in both trials (EUH: 0.6 degrees C; HYP: 1.0 degrees C) and returned to baseline within 30-60 min following similar decay curves. HYP Tc remained higher (0.4 degrees C) than EUH throughout testing (P<0.05), but moderate hyperthermia itself produced no independent effect on anaerobic exercise performance in either trial. CONCLUSIONS: This study demonstrates that neither moderate HYP nor the moderate hyperthermia accompanying HYP by passive heat exposure affect anaerobic exercise performance in a temperate environment.

Effects of a 12-Month Pedometer-Based Walking Intervention in Women of Low Socioeconomic Status.

This study examined the effects of a 12-month walking intervention in overweight/obese, low socioeconomic women. Forty-six women (48.2 ± 8.0 years) entered the study. Outcomes included weight, waist and hip circumferences, body mass index (BMI), blood pressure, glycosylated hemoglobin, blood lipids, fibrinogen, and high-sensitivity C-reactive protein (hsCRP). Both intention-to-treat analyses in all participants and group analyses in study completers only (3K group = increased steps/day by ≥3,000; No Δ group = did not increase steps/day by ≥3,000) were conducted. Group × time ANOVA was used. In study completers, 3K significantly increased steps/day (6,903 ± 3,328 to 12,323 ± 5,736) compared to No Δ (4,926 ± 3,374 to 5,174 ± 3,095) from baseline to 12 months. There was a significant time effect for weight (P = 0.030), BMI (P = 0.029), and hsCRP (P = 0.044). Low socioeconomic women who adhere to a long-term, pedometer-based walking intervention significantly increased steps/day and may improve body weight, BMI, and hsCRP. This could help reduce health disparities in this population over time.

Comparison of sweat loss estimates for women during prolonged high-intensity running.

PURPOSE: This study evaluated the error produced by four commonly used field estimates and two prediction equations of total body sweat loss. METHODS: Eight women distance runners were studied during a 30-km treadmill run (approximately 70% .VO(2max)) in a warm (30 degrees C T(db)) and a cool (14 degrees C T(db)) environment. Total sweat loss (TSL) was determined from changes in body mass corrected for fluid intake (FI), urine losses (UL), clothing (trapped sweat, TS), CO(2)-O(2) exchange (metabolic mass loss, MML), and respiratory water loss (RWL). TSL was compared with four estimates of sweat losses (often employed in the field) from body mass changes corrected for: a) FI only (F-1); b) FI and TS (F-2); c) FI and UL (F-3); or d) FI, TS, and UL (F-4). Two prediction equations were used also for comparison to TSL values. RESULTS: In the warm environment, F-1, F-3, and F-4 accurately estimated (0.2-6.9%; P > 0.05) TSL, whereas F-2 produced a large error (15.3%; P < 0.05). In the cool environment, all four estimates produced large errors (14-41%; P < 0.05). Both prediction equations markedly underestimated (20-22%) TSL in the warm environment and underestimated (41%) or overestimated (20%) TSL in the cool environment. CONCLUSION: TSL can be accurately estimated from changes in body mass using F-1, F-3, or F-4 methods in hot environments; however, none of the methods accurately estimated actual TSL values in a cool environment. Neither prediction equation provided accurate estimates of TSL in warm or cool conditions for women runners. These results illustrate the difficulty of accurately estimating and predicting sweat losses in the field.

Iron status of young males and females performing weight-training exercise.

PURPOSE: To determine the effect of weight training on measures of iron status in young males and females. METHODS: Forty (27 female, 13 male) non-weight-trained college age subjects participated in a 12-wk weight-training program conducted 3 d.wk-1. Blood samples and food diaries were obtained pretraining and at 4-wk intervals. Blood was analyzed for hemoglobin, hematocrit, serum iron (SI), total iron binding capacity (TIBC), transferrin saturation (TS), serum ferritin (SF), soluble transferrin receptor (sTfR), and creatine kinase (CK). Subjects were grouped by SF level (FL, females < or = 20 microg.L-1; FN, females > 20 microg.L-1; ML, males < or = 45 microg.L-1; MN, males > or = 50 microg.L-1) to determine the impact of initial iron status on measured responses. RESULTS: Weight training increased strength and fat-free mass and decreased levels of percent body fat. Hemoglobin concentration declined after 12 wk of training (13.7 +/- 1.6 vs 13.2 +/- 1.7 g.dL-1), independent of gender or initial iron status. Only the MN group experienced a decline in SF level after 8 wk of training (129.7 +/- 77.9 vs 102.0 +/- 57.8 microg.L-1). No significant changes were observed for hematocrit, SI, TIBC, TS, sTfR, or CK measures. Total iron intake, but not heme or bioavailable iron intakes, declined at the 12th week of training compared with baseline (13.4 +/- 6.5 vs 10.7 +/- 4.8 mg.d-1) and was not significantly correlated with hematological or iron status measures. CONCLUSIONS: Hemoglobin concentration declines without alterations in SI, TIBC, TS, or sTfR after 12 wk of weight training. The SF level of males with adequate iron status is lowered with weight training but not among females or males with low iron status.

Branched-chain amino acid supplementation and indicators of muscle damage after endurance exercise.

The purpose of this study was to determine whether branched-chain amino acid (BCAA) supplementation attenuates indirect indicators of muscle damage during endurance exercise as compared with an isocaloric, carbohydrate (CHO) beverage or a noncaloric placebo (PLAC) beverage. Nine untrained men performed three 90 min cycling bouts at 55% VO 2peak. Subjects, blinded to beverage selection, ingested a total of 200 kcal of energy via the CHO or BCAA beverage before and at 60 min of exercise, or they drank the PLAC beverage. Creatine kinase (CK), lactate dehydrogenase (LDH), isokinetic leg-extension and -flexion torque, and muscle soreness were assessed before and immediately, 4 h, 24 h, and 48 h postexercise. The trials were separated by 8 wk. CK activities were significantly lower after the BCAA trial than in the PLAC trial at 4, 24, and 48 h postexercise, as well as lower than the CHO beverage at 24 h postexercise. CK was lower in the CHO trial at the 24- and 48-h time points than in the PLAC trial. LDH activities were lower in the BCAA trial at 4 h than in the PLAC trial. As compared with the CHO and PLAC trials, ratings of perceived soreness were lower at 24 h postexercise, and leg-flexion torque was higher at the 48-h time point after the BCAA trial. The present data suggest that BCAA supplementation attenuates muscle damage during prolonged endurance exercise in untrained college-age men. CHO ingestion attenuates CK activities at 24 and 48 h postexercise as compared with a placebo beverage.

Pedometer measurement of physical activity and chronic disease risk factors of obese lower socioeconomic status African American women.

BACKGROUND: To evaluate physical activity with pedometers and health markers of chronic disease in obese, lower socioeconomic African American women. METHODS: Thirty-five women (48 +/- 8 years) wore pedometers for 2 weeks. One-way analyses of variances were used to compare age, weight, body mass indices (BMI), and health markers of chronic disease (including blood pressure, cholesterol, triglycerides, glycosylated hemoglobin, fibrinogen, C-reactive protein) between women who were classified by steps per day as sedentary (SED < 5000; 2941 +/- 1161 steps/d) or active (ACT > or = 5000; 7181 +/- 2398 steps/d). RESULTS: ACT had significantly lower BMI (ACT: 37.2 +/- 5.6; SED: 44.4 +/- 7.2 kg/m2) and hip circumferences (ACT: 37.2 +/- 5.6; SED: 44.4 +/- 37.2 cm) and higher total cholesterol (ACT: 230 +/- 53; SED: 191 +/- 32 mg/dL) than SED. There were no differences in health markers of chronic disease between SED and ACT. Pearson product moment correlations showed significant negative correlations between steps/d and weight (r = -.42), BMI (r = -.46), and hip circumference (r = -.47). CONCLUSIONS: Increased levels of physical activity were associated with reduced BMI and hip circumferences but were not associated with lower health markers for chronic disease in obese, lower socioeconomic African American women.

Biomechanics, exercise physiology, and the 75th anniversary of RQES.

The purpose of this paper is to review the biomechanics and exercise physiology studies published in the Research Quarterly for Exercise and Sport (RQES) over the past 75 years. Studies in biomechanics, a relatively new subdiscipline that evolved from kinesiology, first appeared in the journal about 40 years ago. Exercise physiology studies have been published in RQES throughout its history. Studies in both subdisciplines reflect areas of research that were of great interest at the time of their publication. Many of the leading scholars, past and present, in both biomechanics and exercise physiology were authors of papers in RQES.

Reliability of near-infrared spectroscopy for determining muscle oxygen saturation during exercise.

Near-infrared spectroscopy is currently used to assess changes in the oxygen saturation of the muscle during exercise. The primary purpose of this study was to assess the reliability of near-infrared spectroscopy in determining muscle oxygen saturation (StO2) in the vastus lateralis during cycling and the gastrocnemius during running for exercise intensities at lactate threshold and maximal effort. Test-retest reliability was determined from an intraclass correlation coefficient obtained from a one-way analysis of variance. Reliability of muscle StO2 for the gastrocnemius at lactate threshold was R = .87, and R = .88 at maximal effort. Reliability of muscle StO2 for the vastus lateralis at lactate threshold was R = .94 and R = .99 at maximal effort.

Sweat iron and zinc losses during prolonged exercise.

The purpose of this study was to examine the effects of a 2-hour exercise bout on sweat iron and zinc concentrations and losses in males and females. Nine male and 9 female recreational cyclists exercised at approximately 50% VO(2peak) in a temperate environment (Ta = 23 degrees C, RH = 51%). Sweat samples were collected for 15 min during each of four 30-min exercise bouts. No significant differences were observed between males' and females' sweat iron or zinc concentrations or losses. Sweat iron concentrations decreased significantly between 60 and 90 min of exercise. Sweating rates increased significantly from 30 to 60 min and remained constant during the second hour. Sweat iron losses were significantly lower during the second hour (0.042 mg/m2/h) than the first hour of exercise (0.060 mg/m2/h). Sweat zinc concentrations also decreased significantly over the 2-hour exercise bout. Dietary intakes of iron and zinc were not significantly correlated to sweat iron and zinc concentrations. Sweat iron and zinc losses during 2 hours of exercise represented 3% and 1% of the RDA for iron and 9% and 8% of the RDA for zinc for men and women, respectively. These results suggest a possible iron conservation that prevents excessive iron loss during prolonged exercise.