Validity of BMI-based Equations for Estimating Body Fat Percentage in Collegiate Male Soccer Players: A Three-Compartment Model Comparison

The ease of calculating body mass index (BMI)-based body fat percentage (BF%) is appealing in collegiate male soccer player who have limited time availability and strict training regimens. However, research has yet to evaluate whether BMI-based BF% equations are valid when compared to a criterion multi-compartment model. PURPOSE: The purpose of this study was to compare BMI-based BF% equations with a three-compartment (3C) model in collegiate male soccer players. METHODS: Sixteen NCAA Division II male soccer players (age = 21 ± 2 years; ht = 179.0 ± 8.2 cm; wt = 78.0 ± 8.5 kg) participated in this study. BMI was calculated as weight (kg) divided by height squared (m2). BF% was predicted with the BMI-based equations of Jackson et al. (BMIJA), Deurenberg et al. (BMIDE) Gallagher et al. (BMIGA), and Womersley and Durnin (BMIWO). The criterion 3C model BF% was determined using air displacement plethysmography (BOD POD®) for body volume and bioimpedance spectroscopy for total body water. RESULTS: The BMI-based BF% equations significantly overestimated mean group BF% for all equations when compared to the 3C model (2.78 to 5.18%; all p \u3c 0.05). The standard error of estimate ranged from 4.18 (BMIDE) to 4.29% (BMIWO). Furthermore, the 95% limits of agreement were similar for all comparisons and ranged from ±7.96 (BMIGA) to 8.18% (BMIJA). CONCLUSIONS: The results of this study demonstrate that the selected BMI-based BF% equations produce fairly small SEEs and 95% limits of agreement. However, the equations also revealed systematic error and a tendency to overestimate mean group BF% when compared to the 3C model. BMI-based equations can be used as an alternative for the individual estimation of BF% in collegiate male soccer players when a more advanced 3C model is not available, but practitioners should consider adjusting for the systematic error (e.g., decrease BMIDE by 2.78%)

Evaluation of Repetitions-to-Failure Equations in the Presence of Male and Female Spotters

One-repetition maximum (1RM) is commonly evaluated in strength and conditioning programs in order to monitor the progress of exercise prescriptions. Although the benefits of muscular strength are well-known, conducting 1RM protocols can be time consuming and is not recommended for certain populations. Alternatively, the estimation of 1RM can be completed by utilizing a repetitions-to-failure (RTF) approach. However, one area that has yet to be systematically evaluated is whether the accuracy of RTF prediction equations is influenced by the sex of a spotter during a 1RM testing protocol. Purpose: The purpose of this study was two-fold: 1) to determine whether differences in RTF, measured 1RM, and 1RM prediction methods vary between lifter and spotter sex; and 2) determine the validity of the 1RM prediction methods in the presence of either a male or female spotter. Methods: 20 resistance-trained individuals (50% males) participated in this study. The first two visits determined 1RM (kg) bench press scores in the presence of a male or female spotter. Subjects bench-pressed loads at 30 (5-repetitions), 50 (5-repetitions) and 70% 1RM (RTF) in the presence of a male or female spotter for visits 3 and 4. Estimated 1RM was determined via the RTF at 70% 1RM using Wathan (Wathan1RM), Mayhew (Mayhew1RM), and Epley (Epley1RM) equations. Results: There were significant interactions when assessing Wathan1RM and Mayhew1RM (pPost hoc analysis revealed Wathan1RM and Mayhew1RM were significantly higher during the male spotter condition (58.13±11.05 and 54.07±10.32kg, respectively) than female spotter condition (54.30±10.61 and 50.53±9.91kg) when evaluated in female weight lifters (p=0.032 and 0.033, respectively). Evaluation of mean differences revealed that the constant error (CE) for male and female spotter conditions was lower for Epley1RM (CE = 4.98 and 4.75kg, respectively)than Wathan1RM (CE = 16.19 and 16.06kg, respectively)and Mayhew1RM (CE = 8.79 and 8.65kg, respectively). Moreover the 95% limits of agreement for male and female spotter conditions were smaller for Epley1RM (±13.79 and 13.62kg, respectively) than Wathan1RM (±26.49 and 22.95kg, respectively)and Mayhew1RM (±19.82 and 17.13kg, respectively). Conclusions: Epley1RM should be used over Wathan1RM and Mayhew1RM when loads up to 70% 1RM are implemented. Also, spotter sex only appears to impact female lifters when employing the prediction equations of Wathan1RM and Mayhew1RM

Development of a DXA-derived Body Volume Equation in Hispanic Adults for Administering in a 4-compartment Model

The necessity of using underwater weighing (UWW) or air displacement plethysmography (ADP) for body volume (BV) restricts the use of a four-compartment (4C) model to research settings. As a result, dual energy X-ray absorptiometry (DXA) has been proposed as an alternative, which would be useful for clinical settings. Nonetheless, it is unknown whether DXA-derived BV is valid in a 4C model for Hispanics. PURPOSE: The purpose of the current study was two-fold: 1) to develop a new DXA-derived BV equation with the GE-Lunar Prodigy while utilizing UWW as a criterion and 2) cross-validate 4C models when utilizing the new DXA-derived BV equation (4C-DXANICKERSON), Wilson DXA-derived BV equation (4C-DXAWILSON), and air displacement plethysmography (ADP)-derived BV (4C-ADP) in Hispanic adults. METHODS: 191 Hispanic adults (18-45yrs) participated in the current study. The development sample consisted of 60 females and 60 males whereas the cross-validation sample comprised of 41 females and 30 males. Criterion body fat percentage (BF%) and fat-free mass (FFM) were determined using a 4C model with UWW as a criterion for BV (4C-UWW). The new DXA-derived BV equation (Nickerson) was developed by linearly regressing UWW-derived BV with DXA fat mass (FM), lean mass (LM), and bone mineral content (BMC). 4C-DXANICKERSON, 4C-DXAWILSON, and 4C-ADP were compared against 4C-UWW in the cross-validation sample. RESULTS: The new DXA-derived BV equation (L) was generated in the development sample as follows: (FM/0.91) + (LM/1.06) + (BMC/16.95) + 0.268. 4C-DXANICKERSON, 4C-DXAWILSON, and 4C-ADP all produced similar mean values (BF%=21.04±5.99, 22.23±6.93, and 20.62±6.26%, respectively) when compared to 4C-UWW (21.29±6.14%) in Hispanic males (all p\u3e0.05). 4C-DXANICKERSON also yielded similar BF% and FFM values as 4C-UWW when evaluating the constant error (CE) in Hispanic females (CE=-0.79% and 0.38kg; p=0.060 and 0.174, respectively). However, 4C-DXAWILSON produced significantly different BF% and FFM values (CE=3.22% and -2.20kg, respectively; both pWILSON yielded significant proportional bias when estimating BF% (coefficient=0.226; pCONCLUSION: Current study findings demonstrate that 4C-DXANICKERSON is a valid measure of BV in Hispanics and is recommended for use in clinics where DXA is the main body composition assessment technique

Validation of Various Load-velocity Relationships for Estimation of Bench Press 1-repetition Maximum

Estimating 1-repetition maximum (1RM) by measuring mean concentric velocity (MCV)is an indirect method that has gained popularity in the field of strength and conditioning. It has previously been recommended that 4 – 6 loads ranging from 30 – 85% 1RM be used when estimating 1RM via MCV. Nonetheless, the validity of fewer loads at varying intensities is an area in need of further investigating. Purpose: The purpose of this study was to validate various load-velocity relationships to predict bench press 1RM values. Methods: 20 resistance-trained individuals (50% males) participated in this study. Warm-up sets consisted of subjects bench pressing loads at 50 (5-repetitions), 70 (3-repetitions) and 90% (1-repetition) of estimated 1RM. Following the warm-up loads, a maximal of 4 attempts were performed in order to determine measured 1RM. The MCV (m∙s-1)was recorded using a linear position transducer during the warm-up and 1RM trials in order to develop load-velocity profiles. Specifically, four different velocity-based 1RM equations (EQ) were determined using the warm-up loads of 50, 70, and 90% (MCV-EQ1), 50 and 90% (MCV-EQ2), 70 and 90% (MCV-EQ3), and 50 and 70% (MCV-EQ4). Results: Evaluation of mean differences revealed the constant error (CE) for the MCV prediction equations were not statistically significant for any comparisons (CEs = 0.80 to 2.96 kg; all p \u3e 0.05). In addition, the correlation coefficients between the MCV prediction methods and measured 1RM were near perfect for all comparisons (r ³ 0.98; all p \u3c 0.001). The validity statistics indicated the standard error of estimate (SEE) and 95% limits of agreement (LOAs) was lowest for MCV-EQ1 (7.86 kg and ±15.00 kg, respectively) and highest for MCV-EQ3 (9.24 kg and 17.74 kg, respectively). Nonetheless, the SEEs and 95% LOAs for MCV-EQ2 (8.10 kg and ±15.55 kg, respectively) and MCV-EQ4 (8.38 kg and ±16.08 kg, respectively) were similar as MCV-EQ1. Conclusions: The current study findings revealed that MCV-EQ3 produced the largest individual error (SEE and 95% LOAs). Therefore, practitioners may consider employing the load-velocity relationships of MCV-EQ1, MCV-EQ2, or MCV-EQ4. Collectively, the current study findings reveal that 2 (MCV-EQ2 and MCV-EQ4) or 3 (MCV-EQ1) warm-up loads can easily be employed to estimate velocity-based 1RM on the bench press

Bias Varies for Bioimpedance Analysis and Skinfold Technique when Stratifying Collegiate Male Athletes Fat-free Mass Hydration Levels

Bioelectrical impedance analysis (BIA) and skinfold (SF) techniques are commonly used to estimate body composition in athletic settings. Both methods are based upon a 2-compartment (2C) model approach, which assumes the hydration of fat-free mass (FFM) is constant (73.80%). Deviations from assumed constants such as FFM hydration have previously been observed in athletes. However, the magnitude of error associated with deviations in FFM hydration are scarce. PURPOSE: The purpose of this study was to evaluate the accuracy of BIA- and SF-based body fat percentage (BF%) estimates in collegiate athletes when stratifying FFM hydration levels. METHODS: FFM hydration levels for the entire sample ranged from 64.55–73.84%. Therefore, athletes were analyzed as a whole (FFM-HydrationALL: n=63) and at the FFM hydration levels of 64.00-68.99% (FFM-HydrationL1: n=37) and 69.00-74.00% (FFM-HydrationL2: n=26). A 3-compartment model utilizing air displacement plethysmography for body volume and bioimpedance spectroscopy for total body water was employed in order to determine the accuracy of BIA and SF for the 3 separate groups. RESULTS: The results of this study demonstrated that BIA had significant constant error (CE) when analyzed in FFM-HydrationALL, FFM-HydrationL1, and FFM-HydrationL2 (all p \u3c 0.001; CE = 5.64, 6.27, and 4.73%, respectively). However, the CE was not statistically significant for SF when evaluating FFM-HydrationALL, FFM-HydrationL1, and FFM-HydrationL2 (all p \u3e 0.05; CE = -0.04, -1.36, and 1.83%, respectively). The BIA device revealed proportional bias for FFM-HydrationALL and FFM-HyrdrationL1 (coefficients = -0.19 and -0.21; both p \u3c 0.05). However, the proportional bias was not present for BIA when analyzed in FFM-HydrationL2 (coefficient = -0.16; p = 0.06). Lastly, the SF method only had significant proportional bias when examined in FFM-HydrationALL (coefficient = 0.17; p = 0.02).CONCLUSIONS: The current study results revealed that proportional bias for BIA is removed when FFM hydration levels approach the assumed 73.80% commonly employed in 2C models. In contrast, the large variance in FFM hydration levels did not impact the SF technique. Therefore, practitioners are encouraged to utilize the SF technique over BIA when assessing BF% in collegiate male athletes

Evaluation of Fat-free Mass Characteristics at Different Adiposity Levels: Impact of Weight Status Stratification Method

The method used to stratify weight status when evaluating fat-free mass (FFM) characteristics has primarily been based upon body mass index (BMI) and not body fat percent (BF%). As a result, it is unknown whether deviations in FFM characteristics are similar when stratifying weight status based upon BMI or BF%. Purpose: The purpose of this study was to evaluate FFM characteristics at different adiposity levels when stratifying weight status via BMI and BF%. Methods: 150 adults (50% males) participated in this study. 3-compartment (3C) model body composition was based upon body density (Db) via air displacement plethysmography (ADP) and total body water via bioimpedance analysis. FFM density (DFFM), residual (RFFM), and hydration (HFFM)were evaluated in all subjects. The Db obtained from a stand-alone assessment of ADP (2C-Db) and 3C model (3C-Db)were also compared between groups. Subjects were stratified based upon weight status (BMI and BF%). First, subjects were divided into a normal weight (NW-BMI), overweight (OW-BMI) or obese (OB-BMI) group, which were based upon BMI values of 18.5-24.99 kg/m2 (n=50), 25.0-29.99 kg/m2 (n=50), and ³ 30.0 kg/m2 (n=50), respectively. Next, subjects were divided into groups based upon BF% where normal weight BF% values (NW-BF%) for males and females were \u3c 25 and 35% (n=81), respectively, and obese BF% values (OB-BF%) were ³25 and 35% (n=69), respectively. Results: The DFFM ranged from 1.096 – 1.097 g/cm3 for all groups in both weight status stratification methods (all p \u3e 0.05). HFFM and RFFM were similar for all comparisons and ranged from 73.99 – 74.33% and 25.67 – 26.01%, respectively, for BMI groups and 74.02 – 74.26% and 25.74 – 25.98%, respectively, for BF% groups (all p \u3e 0.05). In contrast, the 3C-Db (1.050, 1.036, and 1.013 g/cm3) and 2C-Db (1.051, 1.036, and 1.014 g/cm3) were statistically significant for all comparisons between NW-BMI, OW-BMI, and OB-BMI respectively (all p \u3c 0.05). Furthermore, 3C-Db (1.051 and 1.011 g/cm3) and 2C-Db (1.052 and 1.012 g/cm3) were significantly different when comparing NW-BF% and OB-BF% (both p \u3c 0.05). CONCLUSIONS: Previous research has reported the FFM characteristics when stratifying weight status via BMI classification. As a result, it was unknown whether deviations in FFM characteristics existed when stratifying by BF%. Uniquely, the current study findings revealed that FFM characteristics are similar between groups regardless of the weight status stratification method (BMI or BF%)

Evaluation of Load Velocity Profiles with Varying Warm-up Sets and Relative Intensities

International Journal of Exercise Science 14(4): 971-979, 2021. The purpose of this study was to determine whether the number of warm-up sets and relative intensity impacts the prediction of velocity-based one-repetition maximum (1RM) values. Twenty resistance-trained individuals (males: n = 10, females: n = 10) participated in this study. Warm-up sets consisted of subject’s bench-pressing loads at 50 (five-repetitions), 70 (three-repetitions), and 90% (one-repetition) of estimated 1RM. A maximum of four attempts were performed to determine 1RM, while recording mean concentric velocity (MCV)using a linear position transducer during warm-up and 1RM trials in order to develop load-velocity profiles. Specifically, four different velocity-based 1RM equations (EQ) were developed from the warm-up sets of 50, 70, and 90% (MCV-EQ1), 50 and 90% (MCV-EQ2), 70 and 90% (MCV-EQ3), and 50 and 70% (MCV-EQ4). Constant error (CE) for the MCV prediction equations were not statistically significant for any comparisons (CEs = 0.80 to 2.96kg, all p \u3e 0.05). Correlation coefficients between the MCV prediction methods and measured 1RM were near perfect for all comparisons (r ≥ 0.98, all p \u3c 0.001). The standard error of estimate (SEE) and 95% limits of agreement (LOAs) were lowest for MCV-EQ1 (7.86 kg and ± 15.00 kg, respectively) and slightly higher for MCV-EQ3 (9.24 kg and 17.74 kg, respectively). Nonetheless, SEEs and 95% LOAs for MCV-EQ2 (8.10 kg and ± 15.55kg, respectively) and MCV-EQ4 (8.38 kg and ± 16.08 kg, respectively) were similar as MCV-EQ1. Current study results indicated that an additional warm-up set only slightly increases the accuracy of velocity-based 1RM estimations. Furthermore, larger differences in relative intensity will help produce slightly more accurate 1RM values

Educators in the Time of COVID: Metamorphosis of a Profession and of a People

The following is a collection of reflections written by six educators ranging from K–Higher Education. In this feature, these educators share their experiences of living and educating during the 2020–2021 COVID-19 pandemic. Once compartmentalized and only used when needed, their separate roles and identities had to merge to meet educator, spousal, and parental demands. The first text by Brett Nickerson shows how his life as husband and father collided with his profession as an assistant professor at a university when his wife, a dedicated nurse, was called to help others in need. The second testimonial is by Mayra Garcia, a wife, parent of two, and social studies teacher at a high school. The third piece is by Claire Murillo, an educator and a mother, who experienced caring for a newborn during a hectic year of changes. Regina J. Bustillos, a wife, mother of four, and an educator in a border town in West Texas, contributes the fourth reflection. In the fifth reflection, Qiana O’Leary shares her narrative about finding who she is as an educator in this unprecedented crisis. Finally, the sixth reflection by Sara Abi Villanueva—a wife, mother of two, at the time, a graduate student, and an English, language arts, and reading teacher at the secondary level—is a life-in-the-day reflection schedule

Carbohydrate Rinse Fails to Enhance Cycling Performance or Alter Metabolic and Autonomic Recovery in Recreational Cyclists

The purpose of the study was to examine the effects of carbohydrate (CHO) mouth rinsing on autonomic and metabolic recovery as well as cycling performance. Ten male recreational cyclists (age = 30 ± 6 years, VO2peak = 54.5 ± 8.1 mL·kg-1·min-1) completed a randomized, double-blind, placebo-controlled, crossover designed study. A CHO or a placebo (PLA) rinse was administered every 12.5% of a work to completion trial (75%Wmax). Heart rate variability (lnRMSSD), the respiratory exchange ratio, and plasma epinephrine, norepinephrine, insulin, glucose, free fatty acids (FFA), and lactate were measured pre- and post-exercise. The CHO rinse did not improve time to completion of the test trial (CHO: 4108 ± 307 s, PLA: 4176 ± 374 s, p = 0.545). Further, the CHO rinse did not impact autonomic recovery, as measured by lnRMSSD (p = 0.787) and epinephrine (p = 0.132). Metabolic biomarkers were also unaffected by the CHO rinse, with no differences observed in responses of FFA (p = 0.064), lactate (p = 0.302), glucose (p = 0.113) or insulin (p = 0.408). Therefore, the CHO mouth rinse does not reduce the acute sympathetic response following strenuous exercise and does not result in improvements in cycling time to completion

Effects of Heat Exposure on Body Water Assessed using Single-Frequency Bioelectrical Impedance Analysis and Bioimpedance Spectroscopy

International Journal of Exercise Science 10(7): 1085-1093, 2017. The purpose of this study was to determine if heat exposure alters the measures of total body water (TBW), extracellular water (ECW), and intracellular water (ICW) in both single-frequency bioelectrical impedance analysis (BIA) and bioimpedance spectroscopy (BIS). Additionally, we sought to determine if any differences exist between the BIA and BIS techniques before and after brief exposure to heat. Body water was evaluated for twenty men (age=24±4 years) in a thermoneutral environment (22°C) before (PRE) and immediately after (POST) 15 min of passive heating (35°C) in an environmental chamber. The mean difference and 95% limits of agreement at PRE demonstrated that BIS yielded significantly higher body water values than BIA (all p0.05; 0.2±1.5kg). Additionally, the ES of the mean differences at POST were trivial to small and the r-values were high (r≥0.96). When analyzing the changes in body water before and after heat exposure, POST values for BIS were significantly higher than PRE (all