Curt B. Dixon

Concurrent validation of the OMNI perceived exertion scale for resistance exercise.

UNLABELLED The criterion variables were total weight lifted (Wttot ) determined separately for women and men during BC and KE, and blood lactic acid concentration ([Hla]) determined for a combined female ( N = 10) and male ( N = 10) subset during BC. Subjects performed three separate sets of 4, 8, and 12 repetitions for BC and KE at 65% one-repetition maximum. Rating of perceived exertion for the active muscles (RPE-AM) was measured during the mid and final repetition and RPE for the overall body (RPE-O) during the final repetition. : For both female and male groups across the three sets: (a) RPE-AM ranged from 3.6 to 8.2 for BC and 5.1 to 9.6 for KE and (b) RPE-O ranged from 2.4 to 6.7 for BC and 4.2 to 7.6 for KE. Positive linear regressions ranged from r = 0.79 to 0.91 ( P < 0.01) between Wttot and RPE-AM (mid), RPE-AM (final), and RPE-O for both BC and KE in both sex groupings. A positive ( P < 0.01) linear regression was found between [Hla] and RPE-AM (final) (r = 0.87) during BC. RPE did not differ between women and men at any measurement point within each set for BC and KE. RPE-AM (final) was greater ( P < 0.01) than RPE-O in the three sets of BC and KE. CONCLUSION Findings provided concurrent validation of the OMNI-RES to measure RPE for the active muscle and overall body in young recreationally trained female and male weight lifters performing upper- and lower-body resistance exercise.

Self-regulated cycling using the children's OMNI Scale of Perceived Exertion

PURPOSE An estimation and production paradigm was used to determine whether clinically normal 8- to 12-yr-old female (N = 18) and male (N = 18) children could (a) self-regulate intermittent cycle ergometer exercise using a prescribed target rating of perceived exertion (RPE), (b) discriminate between target RPEs, and (c) produce intermittent target RPEs in both an ascending and descending sequence. METHODS Overall body RPE was assessed with the Childrens OMNI Scale (0-10). Subjects underwent (a) one orientation trial, (b) one estimation (E) trial, and (c) two production (P) trials. During E, RPE was estimated each minute of a progressive cycle ergometer test. During the 3-min intermittent P trials, subjects titrated cycle brake force to produce either an RPE sequence of 2 and 6 (ascending) or 6 and 2 (descending). The P trials simulated short, intermittent exercise typical of childrens play. RESULTS Oxygen uptake (VO2) did not differ between E and P at a target RPE of 2 (0.63 versus 0.66 L x min(-1)) and 6 (1.27 vs 1.21 L x min(-1)). Heart rate (HR) did not differ between E and P at a target RPE of 2 (104.1 vs 102.6 beats.min-1) and 6 (153.7 vs 154.5 beats x min(-1)). Both VO2 and HR were higher (P < 0.01) at a target RPE-6 than -2. Responses were not affected by gender or production sequence. CONCLUSION Young female and male children were able to use the OMNI Scale to self-regulate short-duration intermittent cycle exercise intensity.

Evaluation of the BOD POD and Leg-to-Leg Bioelectrical Impedance Analysis for Estimating Percent Body Fat in National Collegiate Athletic Association Division III Collegiate Wrestlers

The purpose of this study was to compare percent body fat (%BF) estimated by air displacement plethysmography (ADP) and legto-leg bioelectrical impedance analysis (LBIA) with hydrostatic weighing (HW) in a group (n 5 25) of NCAA Division III collegiate wrestlers. Body composition was assessed during the pre-season wrestling weight certification program (WCP) using the NCAA approved methods (HW, 3-site skinfold [SF], and ADP) and LBIA, which is currently an unaccepted method of assessment. A urine specific gravity less than 1.020, measured by refractometry, was required before all testing. Each subject had all of the assessments performed on the same day. LBIA measurements (Athletic mode) were determined using a Tanita body fat analyzer (model TBF-300A). Hydrostatic weighing, corrected for residual lung volume, was used as the criterion measurement. The %BF data (mean ± SD) were LBIA (12.3 ± 4.6), ADP (13.8 ± 6.3), SF (14.2 ± 5.3), and HW (14.5 ± 6.0). %BF estimated by LBIA was significantly (p < 0.01) smaller than HW and SF. There were no significant differences in body density or %BF estimated by ADP, SF, and HW. All methods showed significant correlations (r = 0.80–0.96; p < 0.01) with HW. The standard errors of estimate (SEE) for %BF were 1.68, 1.87, and 3.60%; pure errors (PE) were 1.88, 1.94, and 4.16% (ADP, SF, and LBIA, respectively). Bland-Atman plots for %BF demonstrated no systematic bias for ADP, SF, and LBIA when compared with HW. These preliminary findings support the use of ADP and SF for estimating %BF during the NCAA WCP in Division III wrestlers. LBIA, which consistently underestimated %BF, is not supported by these data as a valid assessment method for this athletic group.

The Effect of Acute Resistance Exercise on Serum Malondialdehyde in Resistance-Trained and Untrained Collegiate Men

The purposes of this study were to determine whether acute resistance exercise increases serum malondialdehyde (MDA) levels postexercise, and if so, whether resistance exercise training status influences the magnitude of the exercise-induced lipid peroxidation response. Twelve recreationally resistancetrained (RT) and 12 untrained (UT) men who did not have resistance exercise experience in the past year participated in this study. All subjects completed an 8-exercise circuit resistance exercise protocol consisting of 3 sets of 10 repetitions at 10 repetitions maximum for each exercise. Blood samples were obtained pre-exercise, at 5 minutes postexercise, and at 6, 24, and 48 hours postexercise. At pre-exercise, MDA (nmol·ml−1) averaged 3.41 ± 0.25 (RT) and 3.20 ± 0.25 (UT) and did not differ (p > 0.05) either between groups or over time. Creatine kinase (IU·L−1) was significantly (p < 0.05) elevated 5 minutes post-exercise (170.6 ± 25.8), 6 hours postexercise (290.3 ± 34.4), 24 hours postexercise (365.5 ± 49.9), and 48 hours postexercise (247.5 ± 38.5) as compared with pre-exercise (126.4 ± 20.2) for both groups. There was no difference (p < 0.05) in CK activity between groups. This study indicated that moderate-intensity whole-body resistance exercise had no effect on serum MDA concentration in RT and UT subjects.

The effect of acute fluid consumption on measures of impedance and percent body fat using leg-to-leg bioelectrical impedance analysis

Objective:To examine the effect of acute fluid consumption on measures of impedance and percent body fat (%BF) using a common leg-to-leg bioelectrical impedance analyzer system.Design:Cross-sectional design with treatment order determined using a counterbalanced assignment.Setting:University laboratory.Subjects:In total, 21 recreationally active men (mean age 19.7±1.0 years; body mass index 24.2±2.3 kg/m2) volunteered to participate in this study.Intervention:Subjects had their body composition assessed on three separate occasions. After an initial baseline body composition measurement, subjects consumed 591 ml of water (H2O), a carbohydrate/electrolyte drink (CHOE), or received nothing, used as the control (CON). Subjects were reassessed 20, 40, and 60 min after baseline (POST). Urine specific gravity (USG) was recorded at baseline and 60 min POST to assess hydration state.Results:There were no significant changes in impedance or total body water (TBW) for any of the measurement time periods after drinking H2O or a CHOE beverage. Body weight (BW) (P<0.0001) and %BF (P<0.02) increased significantly 20 min POST and remained elevated at the 40 and 60 min POST time periods. After drinking, USG significantly decreased (P<0.0001) 60 min POST from baseline. For the CON trial, there were no significant changes in BW, %BF, TBW, or USG over time.Conclusions:Fluid consumption had no effect on lower-body impedance despite causing significant changes in hydration state. A slight overestimation in %BF (∼0.5%) was observed due to increased BW in the H2O and CHOE trials. This finding may have little practical significance when assessing body composition by LBIA.

A comparison of skinfolds and leg-to-leg bioelectrical impedance for the assessment of body composition in children

BackgroundThis field-based investigation examined the congruence between skinfolds and bioelectrical impedance in assessing body composition in children.MethodsSubjects were 162 female and 160 male children 10–15 years of age. Skinfold measures obtained at the triceps and medial calf and a leg-to-leg bioelectrical impedance system were used to determine percent fat using child-specific equations. Pearson product moment correlations were performed on the percent fat values obtained using skinfolds and bioelectric impedance for the entire data set. Separate correlations were also conducted on gender and age/gender subsets. Dependent t tests were used to compare the two techniques.ResultsPercent fat did not differ between skinfolds and bioelectrical impedance for the total subject pool. Bioelectrical impedance overestimated percent fat in girls by 2.6% and underestimated percent fat in boys by 1.7% (p < 0.01). Correlations between skinfolds and bioelectrical impedance ranged from r = 0.51 to r = 0.90.ConclusionsLeg-to-leg bioelectrical impedance may be a viable alternative field assessment technique that is comparable to skinfolds. The small differences in percent fat between the two techniques may have limited practical significance in school-based health-fitness settings.

The effect of acute fluid consumption on measures of impedance and percent body fat estimated using segmental bioelectrical impedance analysis.

Background/Objectives:To determine the effect of acute fluid consumption on measures of impedance and percent body fat (%BF) estimated using segmental bioelectrical impedance analysis (SBIA).Subjects/Methods:Seventy-six healthy, recreationally active adults (41 women; 35 men) volunteered to participate in this study (mean±s.d.; age, 21.0±1.6 years; body mass index, 25.0±3.2 kg/m2). Subjects had their body composition assessed on three separate occasions. After a baseline measurement, subjects consumed 591 ml of water (H2O), a carbohydrate/electrolyte drink (CHOE) or received nothing (CON). Subjects were reassessed 20, 40 and 60 min following (POST) the baseline measure in each fluid condition.Results:Twenty minutes after drinking a H2O or CHOE beverage, %BF (1.1 and 1.2%), impedance (12 and 14 Ω) and body mass increased significantly (P<0.001). During the CON trial, %BF (0.3 and 0.5%) and impedance (7 and 11 Ω) also increased significantly above baseline values at 40 and 60 min POST. However, the normal hourly variability was significantly (P<0.009) less than the observed fluid-induced %BF alterations. The greatest %BF increases were observed in the lightest subjects, who were women. Fluid type had no effect on the magnitude of change POST.Conclusions:Twenty minutes after drinking, %BF estimates increased approximately 1.0% due to elevations in impedance and body mass. As such, we recommend adhering to the pretest fluid restriction guideline to avoid fluid-induced alterations in SBIA body composition measures. In addition, use of a consistent testing schedule may minimize normal %BF variation over time.

Comparison of Maximal Oxygen Consumption between Obese Black and White Adolescents

Abstract The purpose of this investigation was to determine whether maximal oxygen consumption (VO2max) differed between clinically obese black and white children and if a difference existed to determine whether it was related to hematological profiles and/or physical activity/inactivity levels. Twenty-three black and 21 white adolescents were matched for age, BMI, and Tanner stage (II-V). Body composition was determined by DEXA and CT scan. Daily physical activity/inactivity was assessed by questionnaire. VO2max was assessed using the Bruce treadmill protocol. Black participants had significantly lower VO2max and VO2maxFFM values when compared with white adolescents (26.1 ± 4.2 versus 29.9 ± 3.1 mL · kg−1 · min−1; 48.3 ± 8.8 versus 55.6 ± 5.2 mL · kgFFM−1 · min−1, respectively). Black adolescents also had significantly lower Hb concentrations ([Hb]) than white children (12.7 ± 1.3 versus 13.4 ± 0.7 g/dL). Black adolescents were more physically inactive than their white peers. VO2max correlated with [Hb] for the combined groups. Obese black adolescents had lower VO2max compared with white children and this difference was explained, in part, by the lower [Hb] observed in the black participants. Further investigations should study Hb flow rate (a function of [Hb] · maximal cardiac output) and physical activity/inactivity patterns in obese black and white children as it relates to VO2max.

Effect of resistance exercise on percent body fat using leg-to-leg and segmental bioelectrical impedance analysis in adults.

Dixon, CB and Andreacci, JL. Effect of resistance exercise on percent body fat using leg-to-leg and segmental bioelectrical impedance analysis in adults. J Strength Cond Res 23(7): 2025-2032, 2009-The purpose of this study was to examine the effect of a resistance exercise bout on percent body fat (%BF) measured by leg-to-leg and segmental bioelectrical impedance analysis (LBIA; SBIA) in adults. Eighty-six volunteers (45 women; 41 men) reported to the weight training facility on 2 separate occasions. After an initial LBIA and SBIA assessment, subjects performed 60 minutes of continuous resistance exercise, or did nothing, which served as the control. During the resistance exercise trial, subjects completed an 8-exercise circuit protocol consisting of 3 sets of 10 to 12 repetitions at 65-75% of 1 repetition maximum for each exercise. Subjects were provided with a bottle of water for consumption during both trials. Body composition was reassessed 60 minutes after baseline for comparison. For the resistance exercise trial, significant reductions (p < 0.05) in SBIA-measured %BF (women = 0.9 ± 1.0%; men = 1.4 ± 0.8%) and impedance (women = 22.2 ± 17.0 Ω; men = 22.3 ± 10.0 Ω) were observed, whereas LBIA body composition measurements remained unchanged. After the control trial, significant increases (p < 0.05) in SBIA-measured %BF (women = 0.6 ± 0.8%; men = 0.5 ± 0.7%) and impedance (women = 7.8 ± 12.6 Ω; men = 4.7 ± 8.3 Ω) and LBIA-measured %BF (women = 0.4 ± 0.7%; men = 0.4 ± 0.5%) were observed because of the body mass gain (approximately 300-400 g) after drinking. When using SBIA, assessments should be performed before resistance exercise to eliminate exercise-induced alterations in %BF. Conversely, resistance exercise had no effect on the LBIA measurements, and, therefore, following pretest exercise guidelines may not be necessary when this technology is used for the body composition assessment.

Effect of Exercise Intensity on Percent Body Fat Determined by Leg-to-Leg and Segmental Bioelectrical Impedance Analyses in Adults.

Purpose: We examined the impact that cycle ergometry exercise had on percent body fat (%BF) estimates when assessed using either leg-to-leg or segmental bioelectrical impedance analysis (LBIA; SBIA) and whether the intensity of the exercise bout impacts the %BF magnitude of change. Method: Seventy-four college-aged adults participated in this study. Participants visited the laboratory on three separate occasions. Testing included two 30-min exercise sessions (70% HRmax and 85% HRmax) and a 30-min no-exercise session, which served as the control. Results: Following exercise, significant (p < .05) reductions in mean %BF were observed when using LBIA (70% HRmax = 0.3%; 85% HRmax = 0.5%) and SBIA (70% HRmax = 0.8%; 85% HRmax = 1.4%). The mean %BF reductions were significantly (p < .04) greater following exercise at the higher intensity for both analyzers. Conclusions: Our findings indicate that cycle exercise performed before LBIA and SBIA body composition assessment reduces mean %BF estimates. In addition, the %BF reductions were found to be larger at the higher end of the American College of Sports Medicine/American Heart Association recommended intensity range (85% HRmax) and when the SBIA analyzer was used to conduct the assessment.