Ann L. Gibson

Validation of air displacement plethysmography for assessing body composition

PURPOSE The purpose of this study was to verify the validity of an air displacement plethysmography device (Bod Pod) for estimating body density (Db). METHODS The Db from the Bod Pod (DbBP) was compared with the Db from hydrostatic weighing (DbHW) at residual lung volume in a heterogeneous sample of 30 black men who varied in age (32.0 +/- 7.7 yr), height (180.3 +/- 7.5 cm), body mass (84.2 +/- 15.0 kg), body fatness (16.1 +/- 7.5%), and self-reported physical activity level and socioeconomic status. The Db for each method was converted to relative body fat (%BF) using race-specific conversion formulas and subsequently compared with %BF obtained from dual-energy x-ray absorptiometry (%BFDXA). RESULTS Linear regression, using DbHW as the dependent variable and DbBP as the predictor, produced an R2 = 0.84 and SEE = 0.00721 g x cc(-1). However, the mean difference between the two methods (0.00450 +/- 0.00718 g x cc(-1) was significant (P < 0.01). The Bod Pod underestimated the Db of 73% of the sample. The %BF estimates from the Bod Pod, HW, and DXA differed significantly (P < 0.01). The average %BFBP (17.7 +/- 7.4%) was significantly greater than %BFHW (15.8 +/- 7.5%) and %BFDXA (16.1 +/- 7.5%); however, there was no significant difference between %BFHW and %BFDXA. CONCLUSION The Bod Pod significantly and systematically underestimated Db, resulting in an overestimation of %BF. More cross-validation research is needed before recommending the Bod Pod as a reference method.

Eight-Week Traditional Mat Pilates Training-Program Effects on Adult Fitness Characteristics

We investigated responses of adult, novice practitioners (n = 9) to an 8-week traditional mat Pilates program (P) that met 1 hr/day three times/week. Classes consisted primarily of beginner and intermediate level exercises. Compared to an active control group (C; n = 13) that showed no improvements, those in P significantly (p < .05) improved relative body fat (-1.2%BF), sit-and-reach (+7.5 cm), shoulder reach (+6.9 cm), curl-up (+14 reps), and low back extension (+7 reps) scores, as well as circumferences at the waist (-2.7 cm), chest (-1.7 cm), and arm (-0.5 cm). Baseline differences were noted only for curl-ups and low back extensions, with P being lower than C. Body composition, muscular endurance, and flexibility significantly improved after 8 weeks of traditional mat Pilates.

Potential role of meal frequency as a strategy for weight loss and health in overweight or obese adults.

Improved dietary strategies for weight loss are necessary to decrease metabolic disease risk in overweight or obese adults. Varying meal frequency (MF; i.e., increasing or decreasing eating occasions beyond the traditional pattern of three meals daily) has been thought to have an influence on body weight regulation, hunger control, and blood markers of health. It is common practice for weight management clinicians to recommend increasing MF as a strategy for weight management and to improve metabolic parameters. However, limited research exists investigating the effect of MF during controlled hypocaloric dietary interventions. Furthermore, MF literature often speculates with regard to efficacy of MF treatments based on research using normal weight, overweight/obese, or some combination, where much diversity exists within these various populations. In this review, we suggest that normal-weight and overweight/obese populations, as well as free-living versus investigator-controlled research trials, should be studied independently. Therefore, the objective of the present review is to survey the literature to assess whether the alteration of MF influences body weight regulation, hunger control, and/or blood markers of health in overweight/obese participants undergoing a controlled hypocaloric diet to induce weight loss. Findings of this review indicate that there is uncertainty in the literature when interpreting the optimal MF for obesity treatment, where reduced MF may even show more favorable lipid profiles in obese individuals compared with increased MF. Furthermore, the simple relationship of comparing MF with body fatness or body mass index should also consider whether eating frequency is associated with other healthy factors (e.g., increased physical activity).

Graded Exercise Testing Protocols for the Determination of VO2max: Historical Perspectives, Progress, and Future Considerations

Graded exercise testing (GXT) is the most widely used assessment to examine the dynamic relationship between exercise and integrated physiological systems. The information from GXT can be applied across the spectrum of sport performance, occupational safety screening, research, and clinical diagnostics. The suitability of GXT to determine a valid maximal oxygen consumption (VO2max) has been under investigation for decades. Although a set of recommended criteria exists to verify attainment of VO2max, the methods that originally established these criteria have been scrutinized. Many studies do not apply identical criteria or fail to consider individual variability in physiological responses. As an alternative to using traditional criteria, recent research efforts have been directed toward using a supramaximal verification protocol performed after a GXT to confirm attainment of VO2max. Furthermore, the emergence of self-paced protocols has provided a simple, yet reliable approach to designing and administering GXT. In order to develop a standardized GXT protocol, additional research should further examine the utility of self-paced protocols used in conjunction with verification protocols to elicit and confirm attainment of VO2max.

Time course of supine and standing shifts in total body, intracellular and extracellular water for a sample of healthy adults

Background/objectives:Traditional tetrapolar bioimpedance spectroscopy (BIS) is performed with the participant supine for 10 min. New vertical analyzers are penetrating clinical, home and fitness markets, but have body water values that differ from supine reference measures. The minimum time standing prior to assessment does not appear in the literature. We investigated the time course of body water shifts in healthy adults undergoing 30-min assessments in supine and vertical positions.Subjects/methods:While seated, participants were prepped for standard tetrapolar electrode placement. Starting position was counterbalanced and body water measurements were taken every 5 min for 30 min in both positions. Participants sat for 2 min prior to switching positions. Of the 64 participants, three were unable to stand for 30 min; their data were excluded. Body size differences were minimized via computation of relative (%) change between time intervals for total body water (TBW), extracellular water (ECW) and intracellular water (ICW).Results:ECW and ICW shifted in opposite directions while participants were supine; as ECW decreased at each time point, ICW increased (P<0.0125). Likewise, when participants stood, ECW increased incrementally (P<0.0125), but the decreases in ICW were not significant. At each time interval, the changes in supine ECW and ICW differed from the standing values (P<0.05). No postural or time differences were found for %change TBW.Conclusions:For TBW, 5 min appears sufficient for fluid stabilization in either position. Supine ECW and ICW stabilization require more than 30 min as does standing ECW.

Increased meal frequency attenuates fat-free mass losses and some markers of health status with a portion-controlled weight loss diet

Increased meal frequency (MF) may be associated with improvements in blood markers of health and body composition during weight loss; however, this claim has not been validated. The purpose of the study was to determine if either a 2-meal (2 MF) or 6-meal frequency (6 MF) regimen can improve body composition and blood-based markers of health while consuming a portion-controlled equihypocaloric diet. Eleven (N=11) obese women (52 ± 7 years, 101.7 ± 22.6 kg, 39.1 ± 7.6 kg/m(2)) were randomized into treatment condition (2 MF or 6 MF) for 2 weeks, completed a 2-week washout, and alternated treatment conditions. In pre/post fashion, changes in body composition, glucose, insulin, and lipid components were measured in response to a test meal. Body mass was successfully lost (P ≤ .05) under both feeding regimens (2 MF: -2.8 ± 1.5 vs 6 MF: -1.9 ± 1.5 kg). Altering MF did not impact glucose, insulin, total cholesterol, or low-density lipoprotein cholesterol (P>.05). On average, fat-free mass (FFM) decreased by -3.3% ± 2.6% following the 2 MF condition and, on average, increased by 1.2% ± 1.7% following the 6 MF condition (P ≤ .05). Fasting high-density lipoprotein cholesterol (HDL-C) percentage increased during the 2 MF condition; this was significantly greater than that in the 6 MF condition (1.3% ± 12.2% vs 0.12% ± 10.3%) (P ≤ .05). Overall, reductions in MF (2 MF) were associated with improved HDL-C levels; but the clinical significance is not clear. Alternatively, increased MF (6 MF) did appear to favorably preserve FFM during weight loss. In conclusion, caloric restriction was effective in reducing body mass and attenuating FFM changes in body composition; however, glucose, insulin, and lipid metabolism had no significant differences between MF.

Effect of Acute Dietary Nitrate Consumption on Oxygen Consumption During Submaximal Exercise in Hypobaric Hypoxia

Reduced partial pressure of oxygen impairs exercise performance at altitude. Acute nitrate supplementation, at sea level, may reduce oxygen cost during submaximal exercise in hypobaric hypoxia. Therefore, we investigated the metabolic response during exercise at altitude following acute nitrate consumption. Ten well-trained (61.0 ± 7.4 ml/kg/min) males (age 28 ± 7 yr) completed 3 experimental trials (T1, T2, T3). T1 included baseline demographics, a maximal aerobic capacity test (VO2max) and five submaximal intensity cycling determination bouts at an elevation of 1600 m. A 4-day dietary washout, minimizing consumption of nitrate-rich foods, preceded T2 and T3. In a randomized, double-blind, placebo-controlled, crossover fashion, subjects consumed either a nitrate-depleted beetroot juice (PL) or ~12.8 mmol nitrate rich (NR) beverage 2.5 hr before T2 and T3. Exercise at 3500 m (T2 and T3) via hypobaric hypoxia consisted of a 5-min warm-up (25% of normobaric VO2max) and four 5-min cycling bouts (40, 50, 60, 70% of normobaric VO2max) each separated by a 4-min rest period. Cycling RPM and watts for each submaximal bout during T2 and T3 were determined during T1. Preexercise plasma nitrite was elevated following NR consumption compared with PL (1.4 ± 1.2 and 0.7 ± 0.3 uM respectively; p < .05). There was no difference in oxygen consumption (-0.5 ± 1.8, 0.1 ± 1.7, 0.7 ± 2.1, and 1.0 ± 3.0 ml/kg/min) at any intensity (40, 50, 60, 70% of VO2max, respectively) between NR and PL. Further, respiratory exchange ratio, oxygen saturation, heart rate and rating of perceived exertion were not different at any submaximal intensity between NR and PL either. Blood lactate, however, was reduced following NR consumption compared with PL at 40 and 60% of VO2max (p < .0.05). Our findings suggest that acute nitrate supplementation before exercise at 3500 m does not reduce oxygen cost but may reduce blood lactate accumulation at lower intensity workloads.

Effect of post-exercise caffeine and green coffee bean extract consumption on blood glucose and insulin concentrations.

OBJECTIVE The aim of this study was to investigate the effects of ingesting caffeine and green coffee bean extract on blood glucose and insulin concentrations during a post-exercise oral glucose tolerance test. METHODS Ten male cyclists (age: 26 ± 5 y; height: 179.9 ± 5.4 cm; weight: 77.6 ± 13.3 kg; body mass index: 24 ± 4.3 kg/m(2); VO2 peak: 55.9 ± 8.4 mL·kg·min(-1)) participated in this study. In a randomized order, each participant completed three 30-min bouts of cycling at 60% of peak power output. Immediately after exercise, each participant consumed 75 g of dextrose with either 5 mg/kg body weight of caffeine, 10 mg/kg of green coffee bean extract (5 mg/kg chlorogenic acid), or placebo. Venous blood samples were collected immediately before and after exercise during completion of the oral glucose tolerance test. RESULTS No significant time × treatment effects for blood glucose and insulin were found. Two-h glucose and insulin area under the curve values, respectively, for the caffeine (658 ± 74 mmol/L and 30,005 ± 13,304 pmol/L), green coffee bean extract (637 ± 100 mmol/L and 31,965 ± 23,586 pmol/L), and placebo (661 ± 77 mmol/L and 27,020 ± 12,339 pmol/L) trials were not significantly different (P > 0.05). CONCLUSION Caffeine and green coffee bean extract did not significantly alter postexercise blood glucose and insulin concentrations when compared with a placebo. More human research is needed to determine the impact of these combined nutritional treatments and exercise on changes in blood glucose and insulin.

Hemodynamic and metabolic responses to self-paced and ramp-graded exercise testing protocols

Recent examinations have shown lower maximal oxygen consumption during traditional ramp (RAMP) compared with self-paced (SPV) graded exercise testing (GXT) attributed to differences in cardiac output. The current study examined the differences in hemodynamic and metabolic responses between RAMP and SPV during treadmill exercise. Sixteen recreationally trained men (aged23.7 ± 3.0 years) completed 2 separate treadmill GXT protocols. SPV consisted of five 2-min stages (10 min total) of increasing speed clamped by the Borg RPE6-20 scale. RAMP increased speed by 0.16 km/h every 15 s until volitional exhaustion. All testing was performed at 3% incline. Oxygen consumption was measured via indirect calorimetry; hemodynamic function was measured via thoracic impedance and blood lactate (BLa-) was measured via portable lactate analyzer. Differences between SPV and RAMP protocols were analyzed as group means by using paired-samples t tests (R Core Team 2017). Maximal values for SPV and RAMP were similar (p > 0.05) for oxygen uptake (47.1 ± 3.4 vs. 47.4 ± 3.4 mL·kg-1·min-1), heart rate (198 ± 5 vs. 200 ± 6 beats·min-1), ventilation (158.8 ± 20.7 vs. 159.3 ± 19.0 L·min-1), cardiac output (26.9 ± 5.5 vs. 27.9 ± 4.2 L·min-1), stroke volume (SV) (145.9 ± 29.2 vs. 149.8 ± 25.3 mL·beat-1), arteriovenous oxygen difference (18.5 ± 3.1 vs. 19.7 ± 3.1 mL·dL-1), ventilatory threshold (VT) (78.2 ± 7.2 vs. 79.0% ± 7.6%), and peak BLa- (11.7 ± 2.3 vs. 11.5 ± 2.4 mmol·L-1), respectively. In conclusion, SPV elicits similar maximal hemodynamic responses in comparison to RAMP; however, SV kinetics exhibited unique characteristics based on protocol. These results support SPV as a feasible GXT protocol to identify useful fitness parameters (maximal oxygen uptake, oxygen uptake kinetics, and VT).

Nitrate-Containing Beetroot Juice Reduces Oxygen Consumption During Submaximal Exercise in Low but Not High Aerobically Fit Male Runners

[Purpose] To examine the effect of a 4-day NO3- loading protocol on the submaximal oxygen cost of both low fit and high fit participants at five different exercise intensities. [Methods] Eleven (6 high fit, VO2max 60.1 ± 4.6ml/kg/min; 5 low fit, VO2max 42.4 ± 3.2ml/ kg/min) participants were initially assigned to a placebo (PL; negligible NO3-) or inorganic nitrate-rich (NR; 6.2 mmol nitrate/day) group using a double-blind, placebo-controlled, crossover design. Participants completed three trials (T1, T2 and T3). T1 included a maximal aerobic capacity (VO2max) treadmill test. A 6-day washout, minimizing nitrate consumption, preceded T2. Each of the four days prior to T2 and T3, participants consumed either PL or NR with the final dose 2.5 hours prior to exercise. A 14-day washout followed T2. T2 and T3 consisted of 5-minute submaximal treadmill bouts (45, 60, 70, 80 and 85% VO2max) determined during T1. [Results] Low fit nitrate-supplemented participants consumed less oxygen (p<0.05) at lower workloads (45% and 60% VO2max) compared to placebo trials; changes were not observed in high fit participants. The two lowest intensity workloads of 45 and 60% VO2max revealed the greatest correlation (r=0.54, p=0.09 and r=0.79, p<0.05; respectively) between VO2max and change in oxygen consumption. No differences were found between conditions for heart rate, respiratory exchange ratio or rating of perceived exertion for either fitness group. [Conclusion] Nitrate consumption promotes reduced oxygen consumption at lower exercise intensities in low fit, but not high fit males. Lesser fit individuals may receive greater benefit than higher fit participants exercising at intensities <60% VO2max.