Malia N.M. Blue

Effects of high-intensity interval training on cardiometabolic risk factors in overweight/obese women

ABSTRACT The purpose of this study was to evaluate two practical interval training protocols on cardiorespiratory fitness, lipids and body composition in overweight/obese women. Thirty women (mean ± SD; weight: 88.1 ± 15.9 kg; BMI: 32.0 ± 6.0 kg · m2) were randomly assigned to ten 1-min high-intensity intervals (90%VO2 peak, 1 min recovery) or five 2-min high-intensity intervals (80–100% VO2 peak, 1 min recovery) or control. Peak oxygen uptake (VO2 peak), peak power output (PPO), body composition and fasting blood lipids were evaluated before and after 3 weeks of training, completed 3 days per week. Results from ANCOVA analyses demonstrated no significant training group differences for any primary variables (P > 0.05). When training groups were collapsed, 1MIN and 2MIN resulted in a significant increase in PPO (∆18.9 ± 8.5 watts; P = 0.014) and time to exhaustion (∆55.1 ± 16.4 s; P = 0.001); non-significant increase in VO2 peak (∆2.36 ± 1.34 ml · kg−1 · min−1; P = 0.185); and a significant decrease in fat mass (FM) (−∆1.96 ± 0.99 kg; P = 0.011). Short-term interval exercise training may be effective for decreasing FM and improving exercise tolerance in overweight and obese women.

Utility of ultrasound for body fat assessment: validity and reliability compared to a multicompartment criterion

Measurement of body composition to assess health risk and prevention is expanding. Accurate portable techniques are needed to facilitate use in clinical settings. This study evaluated the accuracy and repeatability of a portable ultrasound (US) in comparison with a four‐compartment criterion for per cent body fat (%Fat) in overweight/obese adults. Fifty‐one participants (mean ± SD; age: 37·2 ± 11·3 years; BMI: 31·6 ± 5·2 kg m−2) were measured for %Fat using US (GE Logiq‐e) and skinfolds. A subset of 36 participants completed a second day of the same measurements, to determine reliability. US and skinfold %Fat were calculated using the seven‐site Jackson–Pollock equation. The Wang 4C model was used as the criterion method for %Fat. Compared to a gold standard criterion, US %Fat (36·4 ± 11·8%; P = 0·001; standard error of estimate [SEE] = 3·5%) was significantly higher than the criterion (33·0 ± 8·0%), but not different than skinfolds (35·3 ± 5·9%; P = 0·836; SEE = 4·5%). US resulted in good reliability, with no significant differences from Day 1 (39·95 ± 15·37%) to Day 2 (40·01 ± 15·42%). Relative consistency was 0·96, and standard error of measure was 0·94%. Although US overpredicted %Fat compared to the criterion, a moderate SEE for US is suggestive of a practical assessment tool in overweight individuals. %Fat differences reported from these field‐based techniques are less than reported by other single‐measurement laboratory methods and therefore may have utility in a clinical setting. This technique may also accurately track changes.

Metabolic characterization of overweight and obese adults

ABSTRACT Objectives: Traditional evaluations of metabolic health may overlook underlying dysfunction in individuals who show no signs of insulin resistance or dyslipidemia. The purpose of this study was to characterize metabolic health in overweight and obese adults using traditional and non-traditional cardiometabolic variables. A secondary purpose was to evaluate differences between overweight/obese and male/female cohorts, respectively. Methods: Forty-nine overweight and obese adults (Mean ± SD; Age = 35.0 ± 8.9 yrs; Body mass index = 33.6 ± 5.2 kg·m−2; Percent body fat [%fat] = 36.7 ± 7.9%) were characterized. Body composition (fat mass [FM], lean mass [LM], %fat) was calculated using a 4-compartment model; visceral adipose tissue (VAT) was quantified using B-mode ultrasound. Resting metabolic rate (RMR) and respiratory exchange ratio (RER) were evaluated using indirect calorimetry. Fasted blood and saliva samples were analyzed for total cholesterol (TC), high-density lipoproteins (HDL), low-density lipoproteins (LDL), triglycerides (TRG), glucose (GLUC), insulin, leptin, estradiol, and cortisol. Results: The prevalence of individuals with two or more cardiometabolic risk factors increased from 13%, using traditional risk factors (GLUC, TRG, HDL), to 80% when non-traditional metabolic factors (VAT, LM, RMR, RER, TC, LDL, HOMA-IR) were considered. Between overweight/obese, there were no significant differences in %fat (p = 0.152), VAT (p = 0.959), RER (p = 0.493), lipids/GLUC (p > 0.05), insulin (p = 0.143), leptin (p = 0.053), or cortisol (p = 0.063); obese had higher FM, LM, RMR, and estradiol (p < 0.01). Males had greater LM, RMR, and TRG (p < 0.01); females had greater %fat, and leptin (p < 0.001). There were no significant sex differences in RER, estradiol, insulin, or cortisol (p > 0.05). Conclusions: Evaluating metabolic health beyond BMI and traditional cardiometabolic risk factors can give significant insights into metabolic status. Due to high variability in metabolic health in overweight and obese adults and inherent sex differences, implementation of body composition and visceral fat measures in the clinical setting can improve early identification and approaches to disease prevention.

The effects of high intensity interval training on muscle size and quality in overweight and obese adults

OBJECTIVES Despite growing popularity of high intensity interval training (HIIT) for improving health and fitness, limited data exist identifying the effects of HIIT on muscle characteristics. The purpose of the current study was to investigate the effects of a 3-week HIIT intervention on muscle size and quality in overweight and obese men and women. DESIGN Randomized controlled trial. METHODS Forty-four overweight and obese men and women (mean±SD; age: 35.4±12.3years; height: 174.9±9.7cm; weight: 94.6±17.0kg; %fat: 32.7±6.5%) completed the current study. During baseline and post testing, muscle cross sectional area (mCSA) and echo intensity (EI) were determined from a panoramic scan of the vastus lateralis obtained by B-mode ultrasonography. Body composition variables were measured using dual energy X-ray absorptiometry. Participants were randomized into either a 1:1 work-to-rest ratio HIIT group (SIT; n=16), a 2:1 work-to-rest ratio HIIT group (LIT; n=19), or control (CON; n=9). HIIT participants performed five, 2-min bouts (LIT) or 10, 1-min bouts (SIT) at 85-100% VO2peak for 9 sessions over three weeks. RESULTS Analysis of covariance demonstrated a significant increase in mCSA for SIT (p=0.038; change (Δ)=3.17±3.36cm2) compared to CON (Δ=-0.34±2.36cm2). There was no significant difference in EI across groups (p=0.672). CONCLUSIONS HIIT may be an effective exercise modality to influence muscle size in overweight and obese individuals. Future studies should investigate muscle characteristics and remodeling in an overweight population following interventions of longer duration and varying work-to-rest protocols.

Validity of the 4-compartment model using dual energy X-ray absorptiometry-derived body volume in overweight individuals

The purpose of the present study was to assess the validity of dual-energy X-ray absorptiometry (DXA) to estimate body volume (BV) for use in a 4-compartment (4C) body composition model in an overweight/obese population. Body composition of 61 overweight/obese adults (age: 37.3 ± 10.0 years; height: 170.2 ± 9.5 cm; body mass: 97.1 ± 17.4 kg) was measured by 2 methods: a criterion 4C model and a DXA-derived BV 4C model. For both models, bioelectrical impedance spectroscopy was used to estimate total body water; total body bone mineral content was measured by a full-body DXA scan. For the criterion 4C model, BV was derived from air displacement plethysmography; for the DXA-4C model, BV was derived from previously published coefficients. Total error (TE) and standard error of the estimate (SEE) values for BV (TE = 1.11 L; SEE = 0.01 L) and body fat percentage (%fat) (TE = 2.92%; SEE = 0.32%) represented good to very good agreement between models. The DXA-derived measures of body composition (BV: 96.6 ± 18.1 L; %fat: 39.5% ± 8.1%; fat mass: 38.5 ± 11.9 kg), were significantly greater (p < 0.001) than 4C criterion measures (BV: 95.7 ± 17.6 L; %fat: 37.0% ± 7.6%; FM: 36.0 ± 10.8 kg) with the exception of lean mass, which was significantly lower (p < 0.001; DXA-4C: 58.2 ± 11.2 kg; criterion 4C: 60.7 ± 12.0 kg). Although small statistically significant mean differences were observed, TE and SEE results support the use of the DXA-4C method, which requires less time and equipment, for valid estimates of body composition in overweight/obese individuals.

The effects of nutrient timing on training adaptations in resistance-trained females

OBJECTIVES The purpose of this study was to determine the effects of pre- vs. post-workout nutrition on strength, body composition, and metabolism in trained females over 6 weeks of high intensity resistance training (HIRT). DESIGN Forty-three trained females (mean±SD; age: 20.5±2.2 yrs; height: 165.2±5.7cm; body mass: 66.5±11.4kg) were measured for strength, body composition, and metabolic variables before and after a HIRT intervention. Participants were randomized using a 2:2:1 matched block randomization scheme by baseline leg press strength into a group that consumed a 1:1.5 carbohydrate-protein supplement (16g CHO/25g PRO) pre-training (PRE), post-training (POST), or no supplement (CON). METHODS Dual-energy X-ray absorptiometry was used to evaluate fat mass (FM), lean mass (LM), and percent fat (%fat). Strength was analyzed using a one repetition max on the leg and bench press (LP1RM and BP1RM, respectively). Participants completed HIRT twice per week for 6 weeks. At the first and last trainings, metabolic variables [resting energy expenditure (REE) and respiratory exchange ratio, RER] were measured. RESULTS There were no significant differences between groups for any changes in body composition variables or LP1RM (p=0.170-0.959). There were significant differences for BP1RM (p=0.007), with PRE and POST experiencing greater increases than CON (p=0.010 and 0.015, respectively). REE changes were not significant between groups (p=0.058-0.643). PRE demonstrated greater fat oxidation (RER) at 30min post-exercise (p=0.008-0.035). CONCLUSION Peri-workout nutrition is potentially important for upper body strength and metabolism. PRE may be more effective for promoting fat utilization immediately post-workout.

Fat-Free Mass Index in NCAA Division I and II Collegiate American Football Players

Abstract Trexler, ET, Smith-Ryan, AE, Blue, MNM, Schumacher, RM, Mayhew, JL, Mann, JB, Ivey, PA, Hirsch, KR, and Mock, MG. Fat-free mass index in NCAA Division I and II collegiate American football players. J Strength Cond Res 31(10): 2719–2727, 2017—Fat-free mass index (FFMI) is a height-adjusted assessment of fat-free mass (FFM), with previous research suggesting a natural upper limit of 25 kg·m−2 in resistance trained male athletes. The current study evaluated upper limits for FFMI in collegiate American football players (n = 235) and evaluated differences between positions, divisions, and age groups. The sample consisted of 2 National Collegiate Athletic Association Division I teams (n = 78, n = 69) and 1 Division II team (n = 88). Body composition was assessed via dual-energy x-ray absorptiometry and used to calculate FFMI; linear regression was used to normalize values to a height of 180 cm. Sixty-two participants (26.4%) had height-adjusted FFMI values above 25 kg·m−2 (mean = 23.7 ± 2.1 kg·m−2; 97.5th percentile = 28.1 kg·m−2). Differences were observed among position groups (p < 0.001; &eegr;2 = 0.25), with highest values observed in offensive linemen (OL) and defensive linemen (DL) and lowest values observed in offensive and defensive backs. Fat-free mass index was higher in Division I teams than Division II team (24.3 ± 1.8 kg·m−2 vs. 23.4 ± 1.8 kg·m−2; p < 0.001; d = 0.49). Fat-free mass index did not differ between age groups. Upper limit estimations for FFMI seem to vary by position; although the 97.5th percentile (28.1 kg·m−2) may represent a more suitable upper limit for the college football population as a whole, this value was exceeded by 6 linemen (3 OL and 3 DL), with a maximal observed value of 31.7 kg·m−2. Football practitioners may use FFMI to evaluate an individuals capacity for additional FFM accretion, suitability for a specific position, potential for switching positions, and overall recruiting assessment.

Dietary macronutrient distribution influences post-exercise substrate utilization in women: a cross-sectional evaluation of metabolic flexibility.

BACKGROUND Metabolic flexibility is the ability to alter substrate utilization in response to substrate availability, which may influence health and performance. The current study evaluated the effects of habitual macronutrient distribution on energy expenditure (EE) and metabolic flexibility in physically active women. METHODS Participants (N.=20) completed a 3-day food log and a standardized bout of high-intensity interval training to determine EE and respiratory exchange ratio (RER). EE and RER were measured via indirect calorimetry at rest (PRE) and immediately (IP), 30 minutes (30 min), and 60 minutes postexercise (60 min). To evaluate metabolic flexibility, RER changes were calculated from PRE to IP, IP to 30 min, and IP to 60 min. For each macronutrient, participants were categorized into high- and low-intake groups using a median split. RESULTS No significant correlations were observed between macronutrient distribution and EE when covaried for lean mass (all P≥0.232), and ANCOVAs revealed no significant group × time interactions (all P≥0.241). Fat intake was not associated with ∆RER (all P≥0.477). Correlations between PRO intake and ∆RER approached significance (r=0.373-0.411; P=0.079-0.115), as did inverse associations between CHO and ∆RER (r=-0.404 - -0.409; P=0.084-0.087). Lower RER values were observed in the low-CHO group at 30 min and 60 min (P=0.030) compared to high-CHO. Higher RER values were observed in the high-PRO group at IP (P=0.042) compared to low-PRO. Estradiol was not correlated with RER at any time point, or different between diet groups (all P≥0.401). CONCLUSIONS Results suggest that high PRO and low CHO intakes are associated with greater metabolic flexibility in women.