Effect of race and resistance training status on the density of fat-free mass and percent fat estimates.

The impact of race and resistance training status on the assumed density of the fat-free mass (D(FFM)) and estimates of body fatness via hydrodensitometry (%Fat(D)) vs. a four-component model (density, water, mineral; %Fat(D,W,M)) were determined in 45 men: white controls (W; n = 15), black controls (B; n = 15), and resistance-trained blacks (B-RT; n = 15). Body density by hydrostatic weighing, body water by deuterium dilution, and bone mineral by dual-energy X-ray absorptiometry were used to estimate %Fat(D,W,M). D(FFM) was not different between B and W (or 1.1 g/ml); however, D(FFM) in B-RT was significantly lower (1.091 +/- 0.012 g/ml; P < 0.05). Therefore, %Fat(D) using the Siri equation was not different from %Fat(D,W,M) in W (17.5 +/- 5.0 vs. 18.3 +/- 5.4%) or B (14.9 +/- 5.6 vs. 15.7 +/- 5.7%) but significantly overestimated %Fat(D,W,M) in B-RT (14.0 +/- 5.9 vs. 10.4 +/- 6.0%; P < 0.05). The use of a race-specific equation (assuming D(FFM) = 1.113 g/ml) did not improve the agreement between %Fat(D) and %Fat(D,W,M), resulting in a significantly greater mean (+/-SD) discrepancy for B (1.7 +/- 1.8% fat) and B-RT (6.2 +/- 4.3% fat). Thus race per se does not affect D(FFM) or estimates of %Fat(D); however, B-RT have a D(FFM) lower than 1.1 g/ml, leading to an overestimation of %Fat(D).

Use of air displacement plethysmography for estimating body fat in a four-component model.

PURPOSE: To compare measurements of body density (D(b)) obtained from air displacement plethysmography (AP) and hydrostatic weighing (HW) and to determine the accuracy of substituting D(b) via AP (D(b)-AP) for D(b) via HW (D(b)-HW) in estimating body fatness (%Fat(4C)) and the composition and density of the fat-free mass (Dffm) from a four-component model (fat, mineral, water, and protein). METHODS: D(b) was measured in 50 young adults using AP and HW. Total body water via deuterium dilution, bone mineral content via dual-energy x-ray absorptiometry, and D(b) were used to estimate %Fat(4C). RESULTS: D(b)-AP and D(b)-HW were highly correlated (r = 0.89, SEE = 0.008 g x mL(-1)), but D(b)-AP (1.065 +/- 0.003 g x mL(-1)) was significantly higher (P < 0.05) than D(b)-HW (1.058 +/- 0.003 g x mL(-1)), resulting in a mean difference of 2.8%fat. Differences between %Fat(4C-AP) (17.8 +/- 1.2%) and %Fat(4C-HW) (19.3 +/- 1.2%) were significant (P < 0.05), but the SD of the differences (2.3%) was low. When D(b)-AP was used in a four-component model in place of D(b)-HW, the calculated Dffm was significantly higher (1.109 +/- 0.002 vs 1.105 +/- 0.002 g x mL(-1)) based on a higher (P < 0.05) protein fraction (22.0 +/- 0.4% vs 20.6 +/- 0.4%) and lower (P < 0.05) water (71.1 +/- 0.4% vs 72.4 +/- 0.4%) and mineral fractions (7.0 +/- 0.1% vs 7.1 +/- 0.1%). CONCLUSIONS: AP yields a higher D(b) than HW and may not be a valid method for measuring D(b) or estimating %fat using densitometry. However, due to relatively small bias and low individual error, D(b)-AP is an acceptable substitute for D(b)-HW when estimating %fat with a four-component model in young adults.

Serum cholesterol levels in college students: opportunities for education and intervention.

Elevated serum cholesterol levels have been shown to be associated with premature atherosclerosis in adolescents and young adults. The National Cholesterol Education Program recommends cholesterol screening for all adults aged 20 years or older, but normative data on the college-age population are limited. At a university where lipid profiles are made available to students in selected health/wellness courses, the authors analyzed and summarized lipid profiles on 1,088 undergraduates. Mean total cholesterol levels were similar for men (165 +/- 33 mg/dL) and women (168 +/- 27 mg/dL). The men, however, had significantly lower high-density lipoprotein (HDL) cholesterol and higher low-density lipoprotein (LDL) cholesterol than the women. One hundred twenty-one students (11.1% of the sample) had elevated serum cholesterol levels (LDL-C > or = 130 mg/dL). Cholesterol screening can be used as an educational tool for college students to reinforce the link between lipid levels and health habits.

Evaluation of the BOD POD for assessing body fat in collegiate football players.

PURPOSE: The purpose of this investigation was to evaluate the accuracy of a new air displacement plethysmograph, BOD POD Body Composition System, for determining %fat in collegiate football players. METHODS: Body fatness was estimated from body density (Db), which was measured on the same day using the BOD POD and hydrostatic weighing (HW) in 69 Division IA football players. In addition, 20 subjects were whole body scanned using dual-energy x-ray absorptiometry, DXA (Lunar DPX-L) to assess total body mineral content and %fat. Mineral content and HW determined Db were used to compute %fat from a three-component model (3C; fat, mineral, and residual). RESULTS: Test-retest reliability for assessing %fat using the BOD POD (N = 15) was 0.994 with a technical error of measurement of 0.448%. Mean (+/- SEM) Db measured with the BOD POD (1.064 +/- 0.002 g x cc(-1) was significantly greater (P < 0.05) than HW (1.060 +/- 0.002 g x cc(-1)), thus resulting in a lower %fat for the BOD POD (15.1 +/- 0.8%) compared with HW (17.0 +/- 0.8%). Similar results (N = 20) were found for DXA (12.9 +/- 1.2%) and the 3C (12.7 +/- 0.8%) where %fat scores were significantly higher (P < 0.05) than scores determined using the BOD POD (10.9 +/- 1.0%). CONCLUSIONS: Db measured with the BOD POD was higher than the criterion HW, thus yielding lower %fat scores for the BOD POD. In addition, BOD POD determined %fat was lower than DXA and 3C determined values in a subgroup of subjects. Assessment of %fat using the BOD POD is reliable and requires minimal technical expertise; however, in this study of collegiate football players, %fat values were underpredicted when compared to HW, DXA, and the 3C model.

The gender difference in distance running performance has plateaued: an analysis of world rankings from 1980 to 1996.

PURPOSE: Annual world rankings from 1980-1996 were used i) to determine if the gender difference in distance running events has stabilized, and ii) to examine whether the relative decline in pace as race distance increases is different between men and women. World best (WB) and 100th best times in the 1500 m and the marathon (42 km) for each of the 17 years were the indices used to represent overall trends in men's vis-à-vis women's distance running. METHODS: These data were analyzed using regression analyses to develop and compare gender-specific equations. In the 1500 m, the gender difference in WB times (11.1 +/- 1.1%) was consistent from 1980 to 1996, and the slight rate of improvement in event depth (i.e., 100th rankings) was similar for men and women. RESULTS: In the marathon, the gender difference in WB times (11.2 +/- 0.9%) was essentially the same as for the 1500 m. In 1980, the marathon was a fairly new event for the women, having only just been sanctioned by the International Amateur Athletics Federation (IAAF). As a consequence, the depth of the field increased quickly from 1980 to 1984. Since the mid-1980s, the rate of improvement for women in 100th-ranked times has leveled off to equal that of men. The average declines in relative pace for men and women from the 1500 m to the 10 km to the marathon were found to be remarkably similar with no diminishing of the gender difference as race distance increased. CONCLUSIONS: Based on worldwide indices of competitive distance running, the gender difference in distance running performance has plateaued in recent years. Concomitantly, over the past decade, opportunities for women to train and compete have approached parity with those of men. It is likely that the current gender difference in performance will remain fairly constant because of biological differences between men and women that give men an advantage in distance running.

Bone mineral density and body composition of the United States Olympic women's field hockey team.

OBJECTIVE: To evaluate total bone mineral density (BMD) and body composition (% fat) in world class women field hockey players, members of the 1996 United States Olympic team. METHODS: Whole body BMD (g/cm2) and relative body fatness (% fat) were assessed by dual energy x ray absorptiometry using a Lunar DPX-L unit with software version 1.3z. Body composition was also estimated by hydrostatic weighing and the sum of seven skinfolds. RESULTS: Mean (SD) BMD was 1.253 (0.048) g/cm2 which is 113.2 (4.0)% of age and weight adjusted norms. Estimates of body composition from the three methods were similar (statistically non-significant): 16.1 (4.4)% fat from dual energy x ray absorptiometry, 17.6 (3.2)% from hydrostatic weighing, and 16.9 (2.6)% from the sum of seven skinfolds. Mean fat free mass was approximately 50 kg. CONCLUSIONS: The mean whole body BMD value for members of the 1996 United States Olympic women's field hockey team is one of the highest reported for any women's sports team. Moreover, the mean fat free mass per unit height was quite high and % fat was low. In this group of world class sportswomen, low % fat was not associated with low BMD.

Water versus carbohydrate-electrolyte ingestion before and during a 15-km run in the heat.

Twelve highly trained male runners ran 15 km at self-selected pace on a treadmill in warm conditions to demonstrate differences in physiological responses, fluid preferences, and performance when ingesting sports drinks or plain water before and during exercise. One hour prior to the start of running, an equal volume (1,000 ml) of either water or a 6% or an 8% carbohydrate-electrolyte (CE) drink was ingested. Blood glucose was significantly higher 30 min following ingestion of 6% and 8% CE compared to water, significantly lower at 60 min postingestion with both sports drinks than with water, but similar after 7.5 km of the run for all beverages. During the first 13.4 km, oxygen uptake and run times were not different between trials; however, the final 1.6-km performance run was faster with both CE drinks compared to water. Despite a lower preexercise blood glucose, CE consumption prior to and during exercise significantly improved performance in last 1.6 km of a 15-km run compared to water.

Development of a cadence curl-up test for college students.

The purpose of this study was to evaluate a cadence curl-up test in a college population as compared to the American Alliance for Health, Physical Education, Recreation and Dance (AAHPERD) 1-min sit-up test (Association for Research and Professional Councils and Societies, 1985) and the Robertson 1-min curl-up test (Robertson & Magnusdottir, 1987). A cadence curl-up test, referred to as the GT curl-up test, was set at 25 repetitions per minute. A total of 205 college students completed three trials consisting of one AAHPERD sit-up trial and two GT curl-up trials. A subsample (n = 85) completed the Robertson curl-up test as a fourth trial. Trials were counterbalanced with 7 days rest between each test. To evaluate content validity, electromyography signals from selected muscle sites were measured on 6 participants for each of the three tests. Mean scores and standard deviations for the GT curl-up test, AAHPERD sit-up test, and Robertson curl-up test were M = 46.2, SD = 17.8; M = 46.4, SD = 10.2; and M = 69.7, SD = 14.1), respectively. Pearson product moment correlations among the three tests were low to moderate (r < or = .50). The intraclass correlation reliability estimate for the GT curl-up test was 0.92. In 1-min speed tests, repeated rapid trunk flexion can adversely affect technique and has raised safety concerns (Jette, Sidney & Cicutti, 1984; Faulkner, Sprigings, McQuarrie, & Bell, 1989; Cooper Institute for Aerobics Research, 1994). The Robertson test also requires the use of a curl-up frame. In the GT cadence test these drawbacks are minimized due to a slower, more controlled movement with an objective endpoint that is not dependent on special equipment. Moreover, our EMG findings supported previous reports that curl-up exercise with feet unanchored minimizes rectus femoris involvement. Based on the results of this study, the CT curl-up test was found to be a reliable field test with logical validity supporting its relevance as an index of abdominal muscular endurance among college students.

Comparison of body composition and bone mineral measurements from two DXA instruments in young men.

The purpose of this study was to compare body-composition and whole-body, lumbar spine (LS), femoral neck (FN), trochanter, and Ward's triangle (WT) bone mineral measurements by using the Hologic QDR 1000W (DXAH) and the Lunar DPX-L (DXAL) dual-energy X-ray absorptiometry instruments. In addition, the ability of conversion equations to predict DXAH data from DXAL data were tested. Thirteen healthy young adult males (aged 22.2 +/- 3.6 y, 177.4 +/- 5.3 cm in height, and 72.7 +/- 9.6 kg in weight) were scanned on the same day by using DXAH and DXAL. Whereas measured body mass was not different (P > 0.05) between machines, whole-body fat mass [DXAH-DXAL (DXAdiff) = 1152 +/- 1395 g], percentage fat (DXAdiff = 1.5 +/- 1.7% of body mass), bone mineral density (BMD; DXAdiff = 0.016 +/- 0.023 g/cm2), and bone mineral content (BMC; DXAdiff = 316 +/- 50 g) were lower and whole-body fat-free soft tissue (FFST; DXAdiff = 1781 +/- 1859 g) was higher with DXAH than with DXAL. Lower fat mass (DXAdiff = 2145 +/- 855 g) and BMC (DXAdiff = 216 +/- 36 g) and higher FFST (DXAdiff = 1966 +/- 943 g) in the trunk were primarily responsible for the whole-body differences. Lower BMD and BMC values were found for LS (DXAdiff = 0.145 +/- 0.038 g/cm2 and 3 +/- 2 g, respectively), trochanter (DXAdiff = 0.100 +/- 0.044 g/cm2 and 1.7 +/- 1.0 g), and WT (DXAdiff = 0.195 +/- 0.061 g/cm2 and 1.93 +/- 0.51 g) with DXAH compared with DXAL. DXAH BMD of FN was also lower (DXAdiff = 0.141 +/- 0.032 g/cm2) than with DXAL. Only DXAH whole-body BMC and LS BMD were accurately predicted from DXAL with conversion equations. Predicted DXAH FN BMD was significantly lower than the actual DXAH value (P < or = 0.05), whereas the discrepancy between DXAH and DXAL actually increased for whole-body percentage fat and BMD (DXAdiff = 6.6 +/- 1.3% body mass and 0.020 +/- 0.025 g/cm2). In conclusion, lower whole-body fat mass, percentage fat, and BMC, and higher whole-body FFST with DXAH were due primarily to measurement differences in the trunk. Whereas conversion equations accurately predicted DXAH whole-body BMC and LS BMD from DXAL measurements in young adult males, they did not accurately predict DXAH, percentage fat, and BMD of the whole body and FN BMD.

Fluid intake in male and female runners during a 40-km field run in the heat.

To compare physiological responses, hydration status and exercise performance in similarly trained men and women in a hot, humid environment, 12 highly trained runners were studied during a simulated 40-km race. A 7% carbohydrate-electrolyte (CE) beverage was consumed prior to exercise (400 ml) and every 5 km (approximately 250 ml) during the run. The run times of the males and females did not differ significantly (173.5 +/- 8.5 and 183.8 +/- 4.2 min, respectively); nor did the rate of fluid intake relative to body mass (10.3 +/- 0.7 and 10.7 +/- 0.8 ml kg-1 h-1, respectively) or percent body mass loss (4.0 +/- 0.1% and 3.9 +/- 0.1%, respectively). During the run, %VO2 max, heart rate, concentrations of blood lactate, serum total protein and plasma osmolality were also similar for both groups. However, some significant sex differences (P < 0.05) were observed: the females had lower plasma volume losses and higher serum potassium and sodium concentrations than the males during the run. Rectal temperatures were lower in the female runners compared with the males during the last 10 km of the run (0.7 degrees C) and recovery (1.1 degrees C). Findings from this 40-km field run in hot, humid conditions suggest that CE fluid replacement at a relatively similar dosage (approximately 10 ml kg-1 h-1) may have sex-specific physiological effects. These observations warrant further investigation to assess the need for sex-specific fluid replacement guidelines.

Are adaptations to combined endurance and strength training affected by the sequence of training?

The purpose of this study was to determine whether the sequence of strength training before endurance training (ST/ET) is more or less effective than endurance training followed by strength training (ET/ST). Twenty-three females and 11 males were assigned to one of three groups: ST/ET (n = 15), ET/ST (n = 15) or control (n = 4). The 7-week training programme consisted of strength training using 10 exercises for two sets of 3-12 repetitions and running for 20-25 min at 60-90% of heart rate reserve. Maximal oxygen uptake (VO2 max) was measured during a graded treadmill test, and muscular strength was assessed using one-repetition maximum tests for the bench press (BP), shoulder press (SP), arm curl (AC) and leg press (LP). The VO2 max significantly (P < 0.05) increased 6.7 and 6.2% for the ST/ET and ET/ST groups, respectively. There was no significant (P > 0.05) difference between the two experimental groups. Muscular strength significantly (P < 0.05) improved by 15.2% (BP), 16.6% (SP), 17.2% (AC) and 11.9% (LP) for the ST/ET group and 19.9% (BP), 24.1% (SP), 20.9% (AC) and 14.0% (LP) for the ET/ST group. There were no significant (P > 0.05) differences between the two experimental groups for the BP, AC and LP; however, the ET/ST group increased (P < 0.05) SP strength more than the ST/ET group. In conclusion, adaptations to a combination of short-term endurance and strength training as assessed by VO2 max and BP, AC and LP strength appear to be independent of whether endurance training occurs prior to or following strength training.

Monitoring core temperature during exercise: ingestible sensor vs. rectal thermistor.

A telemetry monitoring system using an ingestible temperature sensor has recently become available commercially, but to our knowledge no published data on exercise applications have been reported. Consequently, core temperature was measured by both ingestible capsule sensors and standard rectal thermistors in six trained subjects (three cyclists, three runners) during 30 to 90 min of progressive cycling or treadmill exercise. Testing was conducted 3-9 h after ingestion of the capsule. The telemetered temperature was lower than the rectal temperature both at rest and during exercise in every subject, with resulting significant (p < 0.005) mean differences (+/- S.D.) of 36.91 (+/- 0.41) vs. 37.50 (+/- 0.21) and 38.01 (+/- 0.33) vs. 38.94 degrees C (+/- 0.24), respectively. The mean temperature difference increased by 58% from rest (0.59 degrees C) to peak exercise (0.93 degrees C). These preliminary findings demonstrate a consistently lower temperature from the capsule sensor located within the GI tract compared to rectal thermistors. Replication of these results and investigation into this disparity are necessary before these ingestible capsules should be used for routine monitoring of core temperature.