Effects of a lifestyle intervention on markers of cardiometabolic risk and oxidized lipoproteins among obese adolescents with prediabetes.

OBJECTIVE: Obesity and hyperglycaemia contribute to the atherosclerotic process in part through oxidative modifications to lipoprotein particles. The present study aimed to evaluate the effects of a lifestyle intervention on markers of oxidized lipoproteins in obese Latino adolescents with prediabetes. DESIGN: Pre-post design. SETTING: Participants were enrolled into a 12-week lifestyle intervention. Measurements pre- and post-intervention included anthropometrics and body composition, lipid panel, oxidized LDL (oxLDL), oxidized HDL (oxHDL), intake of fresh fruits and vegetables, and cardiorespiratory fitness. PARTICIPANTS: Thirty-five obese Latino adolescents (seventeen females, eighteen males; mean age 15·5 (sd 1·0) years; mean BMI percentile 98·5 (sd 1·2)) with prediabetes. RESULTS: Intervention participation resulted in significant reductions in weight (-1·2 %, P = 0·042), BMI and BMI percentile (-2·0 and -0·4 %, respectively, P < 0·001), body fat (-7·0 %, P = 0·025), TAG (-11·8 %, P = 0·032), total cholesterol (-5·0 %, P = 0·002), VLDL-cholesterol (-12·5 %, P = 0·029), and non-HDL-cholesterol (-6·7 %, P = 0·007). Additionally, fitness (6·4 %, P < 0·001) and intake of fruits and vegetables (42·4 %, P = 0·025) increased significantly. OxLDL decreased significantly after the intervention (51·0 (sd 14·0) v. 48·7 (sd 12·8) U/l, P = 0·022), while oxHDL trended towards a significant increase (395·2 (sd 94·6) v. 416·1 (sd 98·4) ng/ml, P = 0·056). CONCLUSIONS: These data support the utility of lifestyle intervention to improve the atherogenic phenotype of Latino adolescents who are at high risk for developing premature CVD and type 2 diabetes.

Effect of Training Status on Oxygen Consumption in Women After Resistance Exercise.

This study compared acute postexercise oxygen consumption in 11 trained women (age, 46.5 ± 1.6 years; body mass index [BMI], 28.4 ± 1.7 kg·m(-2) and 11 untrained women (age, 46.5 ± 1.5 years; BMI, 27.5 ± 1.5 kg·m(-2)) after resistance exercise (RE). Resistance exercise consisted of 3 sets of 8 exercises (8-12 repetitions at 50-80% 1 repetition maximum). Oxygen consumption (VO2 ml·min(-1)) was measured before and after (0, 20, 40, 60, 90, and 120 minutes) RE. Immediately after cessation of RE (time 0), oxygen consumption increased in both trained and untrained women and remained significantly above baseline through 60 minutes after exercise (p < 0.01). Total oxygen consumption during recovery was 31.3 L in trained women and 27.4 L in untrained women (p = 0.07). In trained women, total oxygen consumption was strongly related to absolute (kg) lean mass (r = 0.88; p < 0.001), relative (kilogram per square meter) lean mass (r = 0.91; p < 0.001), and duration of exercise (r = 0.68; p ≤ 0.05), but in untrained women, only training volume-load was related to total oxygen consumption (r = 0.67; p ≤ 0.05). In trained women, 86% of the variance in oxygen consumption was explained by lean mass and exercise duration, whereas volume-load explained 45% in untrained women. Our findings suggest that, in women, resistance training increases metabolic activity of lean tissue. Postexercise energy costs of RE are determined by the duration of stimulation provided by RE rather than absolute work (volume-load) performed. This phenomenon may be related to type II muscle fibers and increased protein synthesis.

Comparison of concentric and eccentric bench press repetitions to failure.

Eccentric muscle actions (ECC) are characterized by muscle lengthening, despite actin-myosin crossbridge formation. Muscles acting eccentrically are capable of producing higher levels of force compared with muscles acting concentrically. The purpose of this study was to determine whether ECC bench press yields greater strength than concentric (CON) as determined by 1 repetition maximum (1RM). Additionally, a comparison was made examining differences in the number of repetitions to failure at different relative intensities of 1RM. Thirty healthy men (age = 24.63 ± 5.6 years) were tested for 1RM in CON and ECC bench press and the number of repetitions completed at 60, 70, 80, and 90% 1RM. For CON repetitions, the weight was mechanically lowered to the chest, and the participant pressed it up until the elbows were fully extended. The ECC bench press consisted of lowering a barbell from a fully extended elbow position to the chest in a continuous controlled manner for 3 seconds as determined by electronic metronome. Paired t-tests showed that ECC 1RM (115.99 ± 31.08 kg) was significantly (p ≤ 0.05) greater than CON 1RM (93.56 ± 26.56 kg), and the number of repetitions completed at 90% 1RM was significantly (p ≤ 0.05) greater in ECC (7.67 ± 3.24) as compared with CON (4.57 ± 2.21). There were no significant differences in number of completed repetitions during CON and ECC bench press at 60, 70, and 80% 1RM. These data indicate that ECC actions yield increased force capabilities (∼120%) as compared with CON in the bench press and may be less prone to fatigue, especially at higher intensities. These differences suggest a need to develop unique strategies for training eccentrically.

Injuries, changes in fitness, and medical demands in deployed National Guard soldiers.

PURPOSE: To characterize noncombat injury/illness, determine changes in physical fitness, and evaluate the influence of these changes on medical resource utilization by National Guard (NG) Soldiers. METHODS: Fifty-four Soldiers from the Arizona NG completed pre- and postdeployment fitness testing. Additionally, individual deployment medical records were inventoried. RESULTS: The majority of noncombat-related medical visits (41%) were musculoskeletal in nature, followed by miscellaneous (33%) and respiratory (13%). Soldiers experienced significant decreases in percent fat mass (-11.1%, p < 0.001) and VO2 peak (-10.8%, p < 0.001). There were significant increases in push-ups (16.4%, p < 0.001), sit-ups (11.0%, p = 0.001), bench-press (10.2%, p < 0.001), and back squat (14.2%, p < 0.001) measures. VO2 peak was inversely correlated to medical resource utilization (r = -0.45 to -0.28, p < or = 0.05). The tertile of Soldiers experiencing the sharpest declines in VO2 peak had significantly more medical visits over the course of the deployment than the other two tertiles (8.0 vs. 2.6 vs. 3.1 medical visits/Soldier, p < or = 0.05). CONCLUSION: The predominate noncombat medical issue was musculoskeletal injury. NG Soldiers improved their body composition, strength, and endurance but experienced significant declines in aerobic fitness while deployed. These data document the association between declining aerobic fitness and increased utilization of medical resources.

Short-term effects of resistance training frequency on body composition and strength in middle-aged women.

Although a dose-response relationship between resistance training frequency and strength has been identified, there is limited research regarding the association between frequency and body composition. This study evaluated the effects of 3 vs. 4 d·wk(-1) of resistance training on body composition and strength in middle-aged women. Twenty-one untrained women (age 47.6 ± 1.2 years) completed 8 weeks of resistance training either 3 nonconsecutive days of the week using a traditional total-body protocol (RT3) or 4 consecutive days of the week using an alternating split-training protocol (RT4). The RT3 completed 3 sets of 8 exercises, whereas RT4 completed 3 sets of 6 upper body exercises or 6 sets of 3 lower body exercises. Both groups completed 72 sets per week of 8-12 repetitions at 50-80% 1 repetition maximum. Weekly training volume load was calculated as the total number of repetitions × load (kg) completed per week. Body composition was measured using air displacement plethysmography. At baseline and after 8 weeks of resistance training, there were no significant between-group differences. Both protocols resulted in significant increases in absolute lean mass (1.1 ± 0.3 kg; p = 0.001), body weight (1.02 ± 0.3 kg; p = 0.005), body mass index (0.3 ± 0.1 kg·m(-2); p = 0.006), strength (p < 0.001), and weekly training volume load (p < 0.001). Correlation analysis revealed that weekly training volume load was strongly and positively related to gains in lean mass (r = 0.56, p = 0.05) and strength (r = 0.60, p = 0.006). In these untrained, middle-aged women, initial short-term gains in lean mass and strength were not influenced by training frequency when the number of training sets per week was equated.

How do they compare?: an assessment of predeployment fitness in the Arizona National Guard.

Currently, there is a paucity of literature that describes physical fitness levels in deploying service members. There has been no data collected that evaluate the Army National Guard or Reserves. This descriptive study will provide physical fitness data for soldiers in the Arizona National Guard (AZNG), allowing for a comparison between the active and reserve components. Sixty soldiers from the AZNG were tested before deployment. Body composition was measured by using air displacement plethysmography. Flexibility testing included the sit and reach (SNR), trunk extension (TE), and shoulder elevation (SE) assessments. Muscular strength was determined by the completion of 1 repetition maximum (1RM) bench press and back squat. Muscular endurance was determined by the completion of the Army push-up (P/U) and sit-up (S/U) test. Muscular power was assessed by the completion of the Wingate cycle test and the standing broad jump (SBJ). Cardiorespiratory fitness was determined by the completion of a VO2peak test. The AZNG soldiers demonstrated a fat mass of 22.7 ± 8.9%, SNR, TE, and SE of 30.0 ± 8.9, 117.1 ± 25.2, and 145.5 ± 50.3 cm, 1RM bench press and back squat of 82.2 ± 29.9 and 104.6 ± 29.0 kg, P/U and S/U of 50 ± 18 and 53 ± 14 reps, peak power of 660.9 ± 177.8 W, SBJ of 191.8 ± 28.4 cm, and VO2peak of 48.9 ± 8.8 ml·kg(-1)·min(-1). This is the first study that provides descriptive data for physical fitness in a reserve component. The data demonstrate that these AZNG soldiers are relatively fit and have comparable results to their active duty counterparts. This descriptive data will provide military leadership a better understanding of the condition of soldiers before deployment and will assist them in better preparing soldiers for future conflicts.

Comparison of body composition measurement with whole body multifrequency bioelectrical impedance and air displacement plethysmography in healthy middle-aged women.

Our purpose was to evaluate accuracy of multifrequency bioelectrical impedance analysis (MFBIA) using air displacement plethysmography (ADP) as the criterion measure. Body composition of 27 women was assessed by ADP followed immediately by MFBIA. There was a strong relationship (p = .01) between ADP and MFBIA in absolute lean mass (r = 0.80), absolute fat mass (r = 0.99), percent lean mass (r = 0.91), and percent fat mass (r = 0.91). Although MFBIA consistently overestimated lean mass and underestimated fat mass compared with ADP, agreement between measurements was within 2%-3% body fat. An accurate assessment tool, MFBIA can be useful in clinical settings.

Effects of intensity and volume on insulin sensitivity during acute bouts of resistance training.

This study evaluated the effects of various resistance exercise protocols on 24-hour postexercise insulin sensitivity. Seventeen participants with impaired fasting glucose (100-125 mg/dL) completed 4 separate bouts of resistance exercise under moderate intensity (65% 1 repetition maximum [1RM]) or high intensity (85% 1RM) conditions within the confines of single set and multiple set protocols. Intravenous fasting blood was taken at baseline and 24 hours postexercise for each exercise condition to measure fasting plasma glucose (G0) and fasting serum insulin (I0) to calculate insulin sensitivity (homeostasis model assessment-insulin resistance = (G0*I0)/405). A minimum of 3 days washout was given between each exercise protocol. A 4 x 2 factorial analysis of variance was performed to compare insulin sensitivity and fasting glucose within subjects and between treatments. All of the exercise protocols improved subsequent insulin sensitivity (p = 0.002) and G0 (p = 0.001). In comparison with single set, there was a significantly greater decrease in G0 (p = 0.021) 24 hours after multiple set bouts. High intensity showed significant decreases in insulin sensitivity as compared with moderate intensity protocols (p = 0.046). Effect size data suggest a dose response relationship between program variables of volume and intensity and 24-hour postexercise insulin sensitivity. High-intensity protocols resulted in greater effect sizes for insulin sensitivity (0.83 multiple set; 0.53 single set) as compared with moderate-intensity protocols. The high-intensity, multiple set bout yielded the greatest treatment effect in both fasting glucose (0.61) and insulin sensitivity (0.83). Overall, single set protocols were less effective than multiple set protocols in lowering fasting blood glucose. Findings suggest a dose-response relationship between volume and intensity on insulin sensitivity and fasting blood glucose. Results indicate that resistance exercise is an effective treatment for acutely enhancing insulin sensitivity and regulating blood glucose in individuals with impaired fasting glucose.

Evaluation of multiple one repetition maximum strength trials in untrained women.

Resistance training for health is increasingly popular, yet limited research exists regarding the most appropriate and reliable methods to evaluate outcomes among nonathletic populations. The purpose of this study was to evaluate differences between multiple trials of 1 repetition maximum (1RM) strength in healthy previously untrained women (35.5 +/- 2.1 years). Nineteen participants completed 3 trials of 1RM chest and leg press with at least 24 hours rest between trials. Familiarization was incorporated into trial 1 for both tests. All trials were highly reliable (intraclass correlation = 0.95). For 1RM chest press, nonsignificant strength changes between trials 1-2 and 2-3 were 1.2 +/- 0.3 kg (p = 0.13) and 1.3 +/- 0.4 kg (p = 0.18), respectively, while the overall increase between trials 1-3 was 2.5 +/- 0.7 kg (p = 0.06). For 1RM leg press, strength changes between trials 1-2 and 2-3 were 6.9 +/- 0.6 kg (p = 0.05) and 7.3 +/- 0.4 kg (p = 0.01), respectively, while the overall difference between trials 1-3 was 14.2 +/- 1.0 kg (p < 0.01). In this study of untrained women, evaluation of maximal strength was significantly different between multiple repeated trials of lower-body strength but not upper-body strength. Thus, it was determined that a series of 3 1RM tests was sufficient to obtain a consistent measurement of maximal upper-body strength (chest press) but not lower-body strength (leg press). These findings may be of assistance for efficient reliable field testing of untrained women.

Feasibility of a Home-Based Balance Intervention in Middle-Aged Women Using Wii Fit Plus®.

BACKGROUND: This study evaluated the feasibility and effectiveness of a home-based exercise intervention using the Wii Fit Plus®. METHODS: A randomized, controlled trial of 24 women (age 53.6 [5.4] y) was used to assess compliance and changes in balance over 12 weeks. Balance was measured via the Berg Balance Scale and Frailty and Injuries: Cooperative Studies of Intervention Techniques-4 Scale at baseline and week 6 and week 12. Participant compliance to the intervention was captured via paper logs and the electronic record collected by the Wii Fit Plus®. RESULTS: Participants in the intervention group were 95% compliant based on electronic records. There were no significant differences between groups for total score on either balance scale. There was a significant group × time interaction in favor of the intervention for maximum velocity y (P < .05), average velocity (P < .05), and was trending for maximum velocity x (P = .05) in the tandem step, eyes closed position. CONCLUSIONS: The results suggest that the Wii Fit Plus® is appropriate for home-based interventions in middle-aged women. Modest improvements in balance indicate that this may be an effective means to improve or maintain balance in older women. More research is needed to determine compliance and benefits to reducing fall risk in durations exceeding 12 weeks.

Postexercise Hemodynamic Responses in Lean and Obese Men.

PURPOSE: We assessed resting central/peripheral blood pressure (BP), postexercise BP, and hemodynamic responses (stroke volume, cardiac output, and systemic vascular resistance) after acute exercise and 2 wk of aerobic training in lean and centrally obese men matched for BP. METHODS: Eight lean (body mass index < 25 kg·m, visceral fat = 279 ± 224 cm) and eight centrally obese (body mass index > 30 kg·m, visceral fat = 1471 ± 374 cm) men performed six training sessions (3 d·wk for 40 min at 65%-70% HRmax). Resting BP and hemodynamic measurements were obtained at baseline, after exercise for 60 min, and at 24 h and 48 h after the last training session. RESULTS: Postexercise brachial and central systolic BP (SBP) and mean arterial BP decreased 3-4 mm Hg below resting in lean (P < 0.001) and increased by 3 mm Hg in obese (P < 0.02). Posttraining resting brachial/central SBP were reduced by 3-4 mm Hg only in lean men (P < 0.05). Pretraining postexercise hypotension was significantly correlated with the training-induced change in resting brachial SBP at 48 h (r = 0.58, P = 0.02), but not at 24 h (r = 0.38, P = 0.15). Similar correlations were observed between acute reductions in central SBP and central SBP at 24 h (r = 0.43, P = 0.09) and 48 h (r = 0.54, P = 0.03) posttraining. CONCLUSIONS: In contrast to the consistent results for lean men, postexercise hypotension was not observed in centrally obese men, and resting SBP was not reduced after a short aerobic training program. Considerable individual variation in postexercise BP response among obese men may have implications for design of exercise interventions to lower BP in these individuals.

Blood ketones are directly related to fatigue and perceived effort during exercise in overweight adults adhering to low-carbohydrate diets for weight loss: a pilot study.

Ketogenic diets have been associated with reductions in free-living physical activity, a response that can be counterproductive in individuals trying to lose weight. To explore whether popular low-carbohydrate diets might impact the desire to exercise by raising blood ketone concentrations, fatigue and perceived effort during exercise were compared in untrained, overweight adults adhering to a ketogenic low-carbohydrate diet or to a control diet low in carbohydrate, but not ketogenic (5%, 65%, and 30% or 40%, 30%, and 30% of energy from carbohydrate, fat, and protein, respectively). In this prospective, randomized, 2-week pilot study, all meals and snacks were provided to subjects, and energy intake was strictly controlled to provide approximately 70% of that needed for weight maintenance. At baseline and at the end of week 2, exercise testing was conducted in fasting participants. Weight loss and the reductions in fat mass did not differ by group during the trial. At week 2, blood beta-hydroxybutyrate concentrations were 3.6-fold greater for the ketogenic vs nonketogenic group (P=0.018) and correlated significantly with perceived exercise effort (r2=0.22, P=0.049). Blood beta-hydroxybutyrate was also significantly correlated to feelings of "fatigue" (r=0.458, P=0.049) and to "total mood disturbance" (r=0.551, P=0.015) while exercising. These pilot data indicate that ketogenic, low-carbohydrate diets enhance fatigability and can reduce the desire to exercise in free-living individuals.

Ketogenic low-carbohydrate diets have no metabolic advantage over nonketogenic low-carbohydrate diets.

BACKGROUND: Low-carbohydrate diets may promote greater weight loss than does the conventional low-fat, high-carbohydrate diet. OBJECTIVE: We compared weight loss and biomarker change in adults adhering to a ketogenic low-carbohydrate (KLC) diet or a nonketogenic low-carbohydrate (NLC) diet. DESIGN: Twenty adults [body mass index (in kg/m(2)): 34.4 +/- 1.0] were randomly assigned to the KLC (60% of energy as fat, beginning with approximately 5% of energy as carbohydrate) or NLC (30% of energy as fat; approximately 40% of energy as carbohydrate) diet. During the 6-wk trial, participants were sedentary, and 24-h intakes were strictly controlled. RESULTS: Mean (+/-SE) weight losses (6.3 +/- 0.6 and 7.2 +/- 0.8 kg in KLC and NLC dieters, respectively; P = 0.324) and fat losses (3.4 and 5.5 kg in KLC and NLC dieters, respectively; P = 0.111) did not differ significantly by group after 6 wk. Blood beta-hydroxybutyrate in the KLC dieters was 3.6 times that in the NLC dieters at week 2 (P = 0.018), and LDL cholesterol was directly correlated with blood beta-hydroxybutyrate (r = 0.297, P = 0.025). Overall, insulin sensitivity and resting energy expenditure increased and serum gamma-glutamyltransferase concentrations decreased in both diet groups during the 6-wk trial (P < 0.05). However, inflammatory risk (arachidonic acid:eicosapentaenoic acid ratios in plasma phospholipids) and perceptions of vigor were more adversely affected by the KLC than by the NLC diet. CONCLUSIONS: KLC and NLC diets were equally effective in reducing body weight and insulin resistance, but the KLC diet was associated with several adverse metabolic and emotional effects. The use of ketogenic diets for weight loss is not warranted.

Effects of an 8-week high-protein or high-carbohydrate diet in adults with hyperinsulinemia.

CONTEXT: Incidence of insulin resistance (IR) in Americans is steadily rising. IR may be ameliorated with < or = 5% loss in body weight. OBJECTIVE: To examine effects of 2 weight-loss diets on body weight and composition in overweight adults with IR. DESIGN: Participants randomly assigned to a high-protein, low-fat (HPLF) or a high-carbohydrate, low-fat (HCLF) diet for 8 weeks. SETTING: All meals prepared and weighed in the metabolic kitchen at Arizona State University. Lunch consumed on-site; all other meals packaged for home consumption. PATIENTS: Twenty overweight, healthy participants with elevated fasting serum insulin (> or = 15 microU/L) were recruited. INTERVENTIONS: Both diets were low-fat (27% kcal from fat; < 7% saturated, < or = 10% monounsaturated, and < or = 10% polyunsaturated) and energy-restricted (energy levels were 1200, 1500, 1700 or 2000 kcal); HPLF: 32% protein, 41% carbohydrate; HCLF: 59% carbohydrate, 14% protein. Energy levels were assigned on the basis of participant's resting metabolic rate. MAIN OUTCOME MEASURES: Body composition, etabolic indices, fasting plasma glucose, and insulin. RESULTS: No significant differences were found in the main outcome measures between the diets. Body weight (HPLF: -4.9 kg; HCLF: -4.0 kg) and total percent body fat (HPLF: -1.5%; HCLF: -0.4%) significantly reduced from baseline to week 8 (P = .005 and P = .035, respectively). CONCLUSION: Both diets promoted > or = 5% loss in body weight and significantly reduced percent body fat.

Energy expenditure and cardiovascular responses to Tai Chi Easy.

OBJECTIVES: The purpose of this study was to evaluate the cardiorespiratory response and energy expenditure during the practice of Tai Chi Easy (TCE). TCE has been proposed as a low-intensity alternative to traditional physical activity. DESIGN: Oxygen cost data were collected from 10 healthy adult women (mean age of 47.9 ± 12.8 years) at rest and during a 30-min session of TCE using an automated metabolic cart and heart rate (HR) telemetry. The Borg rating of perceived exertion (RPE) scale was utilized to measure subjective intensity of the TCE movements. RESULTS: The mean oxygen consumption (VO(2)) for the movements ranged from 4.3 ml kg(-1)min(-1) to 5.5 ml kg(-1)min(-1) with an overall mean of 5.0 ml kg(-1)min(-1). The mean HR for all activity was 67.0 beats per minute and the mean energy expenditure (EE) was 1.6 Kcal min(-1). CONCLUSIONS: Cardiorespiratory and EE responses to TCE indicate that this a low intensity exercise appropriate for individuals requiring activity prescriptions of approximately 2 metabolic equivalents (METs).

Walking Workstation Use Reduces Ambulatory Blood Pressure in Adults With Prehypertension.

BACKGROUND: The acute effect of low-intensity walking on blood pressure (BP) is unclear. PURPOSE: To determine if the acute use of a walking workstation reduces ambulatory blood pressure (ABP) in prehypertensive men and women. METHODS: Ten prehypertensive adults participated in a randomized, cross-over study that included a control workday and a walking workstation workday. ABP was measured for 7 hour during the workday and for 6 hour after work. RESULTS: Both systolic BP (SBP) (134 ± 14 vs. 137 ± 16 mmHg; P = .027) and diastolic BP (DBP) (79 ± 10 vs. 82 ± 12 mmHg; P = .001) were lower on the walking workstation day. Postwork hours (4:00 PM-10:00 PM), SBP (129 ± 13 vs. 133 ± 14 mmHg; P = .008), and DBP (74 ± 11 vs. 78 ± 13 mmHg; P = .001) were also lower on the walking workstation day. DBP load was significantly lower during the walking workstation day, with only 14% of the readings above 90 mmHg compared with 22% of the control day readings (P = .037). CONCLUSION: Accumulation of very-light-intensity physical activity (~2 METs) over the course of a single work day using a walking workstation may reduce BP burden in prehypertensive individuals.

Creatine supplementation influences substrate utilization at rest.

The influence of creatine supplementation on substrate utilization during rest was investigated using a double-blind crossover design. Ten active men participated in 12 wk of weight training and were given creatine and placebo (20 g/day for 4 days, then 2 g/day for 17 days) in two trials separated by a 4-wk washout. Body composition, substrate utilization, and strength were assessed after weeks 2, 5, 9, and 12. Maximal isometric contraction [1 repetition maximum (RM)] leg press increased significantly (P < 0.05) after both treatments, but 1-RM bench press was increased (33 +/- 8 kg, P < 0.05) only after creatine. Total body mass increased (1.6 +/- 0.5 kg, P < 0.05) after creatine but not after placebo. Significant (P < 0.05) increases in fat-free mass were found after creatine and placebo supplementation (1.9 +/- 0.8 and 2.2 +/- 0.7 kg, respectively). Fat mass did not change significantly with creatine but decreased after the placebo trial (-2.4 +/- 0.8 kg, P < 0.05). Carbohydrate oxidation was increased by creatine (8.9 +/- 4.0%, P < 0.05), whereas there was a trend for increased respiratory exchange ratio after creatine supplementation (0.03 +/- 0.01, P = 0.07). Changes in substrate oxidation may influence the inhibition of fat mass loss associated with creatine after weight training.

Evaluation of air displacement for assessing body composition of collegiate wrestlers.

PURPOSE: To evaluate the accuracy of air displacement plethysmography (ADP) by using the BOD POD in comparison with hydrostatic weighing (HW) in a collegiate wrestling population in hydrated and acutely dehydrated states. METHODS: Body composition was determined by ADP, HW, and three-site skinfolds (SK) in 66 NCAA Division I collegiate wrestlers before and after acute dehydration (2.6% reduction in body mass). For all methods, body density (D(b)) was converted to percent body fat (%BF) by using the Brozek equation for Euro-Americans and the Schutte equation for African-Americans. RESULTS: There were no significant differences between ADP and HW for D(b), %BF, and fat-free mass (FFM) in either the hydrated or dehydrated states. The standard errors of the estimate for %BF estimated from ADP with HW as the reference method were 2.12% (hydrated) and 2.16% (dehydrated); prediction errors were 2.35% (hydrated) and 2.49% (dehydrated). Bland-Altman plots of D(b) and %BF showed no systematic bias, and 64 out 66 subjects fell within the 95% limits of agreement (mean difference +/- 2 SD) for both variables. For SK, %BF was significantly higher than HW in both the hydrated and dehydrated state. All methods (ADP, HW, and SK) showed a significant decrease in FFM from the hydrated to the dehydrated state. CONCLUSIONS: This study demonstrates that the BOD POD air displacement method provides similar estimates of D (b), %BF, and FFM when compared with HW in a heterogeneous collegiate wrestling population during hydrated and acutely dehydrated states. Pretest guidelines to ensure normal hydration status before body composition assessment using any method must be followed to minimize measurement error in %BF.

U.S. Cohort Differences in Body Composition Outcomes of a 6-Month Pedometer-Based Physical Activity Intervention: The ASUKI Step Study.

BACKGROUND: Regular physical activity (PA) enhances health and is an important factor in disease prevention and longevity. The 2008 U.S. Physical Activity Guidelines recommends that all healthy adults attain at least 150 minutes per week of moderate intensity aerobic PA (e.g., brisk walking) to maintain and promote PA. OBJECTIVES: This study determined the effects of a 6-month pedometer-based worksite walking intervention with participants focusing on a goal of achieving 10,000 steps per day, on body composition in adults with a wide range of body mass index (BMI) values and compares the changes with outcomes of similar studies. MATERIALS AND METHODS: The design was a single group, quasi-experimental study. All participants received a pedometer and were asked to register the daily number of steps. Men and women (n = 142; age = 41 ± 11.5 years; BMI = 27.2 ± 7.25 kg.m(-2)) received body composition measures at 1, 3, and 6 months. A multilevel growth modeling approach was used to explore change over time and to predict change by steps, age, gender, and fat category categorized as normal and overweight/obese. RESULTS: Significant individual differences in linear slopes and change over time were observed for waist circumference (WC) (-3.0 cm) only in unconditional model (t = -0.67, P = 0.02). CONCLUSIONS: A 3.0 cm loss in WC shows that a 10,000 step per day walking program has the potential to influence changes in body composition measures that are correlated with adverse health outcomes. While significant changes did occur there are some limitations. The analysis did not consider the data regarding completing of 10,000 steps per day and other potential factors that could influence the results. Compliance to the walking dose and initial physical activity and body composition levels are important to consider when studying body composition changes in such programs.

Vitamin C status and perception of effort during exercise in obese adults adhering to a calorie-reduced diet.

OBJECTIVE: Moderate energy restriction and exercise are recommended for effective weight loss. Obese individuals oxidize less fat and report a higher perceived exertion during exercise, characteristics that may negatively influence exercise behavior. Because vitamin C status has been linked to fatigability, we compared the effects of vitamin C supplementation on self-reported fatigue and on the respiratory exchange ratio and the Ratings of Perceived Exertion scale during moderate exercise in healthy obese adults adhering to a hypocaloric diet. METHODS: Twenty adults (4 men and 16 women) were stratified and randomly assigned to receive 500 mg of vitamin C (VC) or placebo (CON) daily for 4 wk while adhering to a vitamin C-controlled, calorie-restricted diet. Feelings of general fatigue as assessed by the Profile of Mood States questionnaire were recorded on a separate day from the exercise session at weeks 0 and 4. Participants walked on a treadmill at an intensity of 50% predicted maximal oxygen consumption for 60 min at weeks 0 and 4, and heart rate, respiratory exchange ratio, and Ratings of Perceived Exertion were recorded. RESULTS: After 4 wk, the two groups lost similar amounts of weight (≈ 4 kg), and the respiratory exchange ratio was not altered by group. Heart rate and the Ratings of Perceived Exertion during exercise were significantly decreased in the VC versus the CON group (-11 versus -3 beats/min, P = 0.022, and -1.3 versus +0.1 U, P = 0.001, respectively), and the general fatigue score was decreased 5.9 U for the VC group versus a 1.9 U increase for the CON group (P = 0.001). CONCLUSION: These data provide preliminary evidence that vitamin C status may influence fatigue, heart rate, and perceptions of exertion during moderate exercise in obese individuals.