Kelly E. Johnson

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.

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.

Effect of Branched-Chain Amino Acid Supplementation on Recovery Following Acute Eccentric Exercise

This study investigated the effect of branched-chain amino acid (BCAA) supplementation on recovery from eccentric exercise. Twenty males ingested either a BCAA supplement or placebo (PLCB) prior to and following eccentric exercise. Creatine kinase (CK), vertical jump (VJ), maximal voluntary isometric contraction (MVIC), jump squat (JS) and perceived soreness were assessed. No significant (p > 0.05) group by time interaction effects were observed for CK, soreness, MVIC, VJ, or JS. CK concentrations were elevated above baseline (p < 0.001) in both groups at 4, 24, 48 and 72 hr, while CK was lower (p = 0.02) in the BCAA group at 48 hr compared to PLCB. Soreness increased significantly from baseline (p < 0.01) in both groups at all time-points; however, BCAA supplemented individuals reported less soreness (p < 0.01) at the 48 and 72 hr time-points. MVIC force output returned to baseline levels (p > 0.05) at 24, 48 and 72 hr for BCAA individuals. No significant difference between groups (p > 0.05) was detected for VJ or JS. BCAA supplementation may mitigate muscle soreness following muscle-damaging exercise. However, when consumed with a diet consisting of ~1.2 g/kg/day protein, the attenuation of muscular performance decrements or corresponding plasma CK levels are likely negligible.

The efficacy of a telemedicine-based weight loss program with video conference health coaching support:

Introduction Clinically significant weight loss is defined as a ≥5% of initial body weight loss within a 6-month period. The purpose of this study was to assess body weight change from a 12-week telehealth-based weight loss program that integrated health coaching via video conferencing. Methods A total of 25 obese participants (12 males, 13 females) were recruited for this fully online 12-week weight loss program. Participants were randomly assigned to either an intervention group or control group (n = 13 intervention, body mass index (BMI) = 34.7 ± 4.5 kg/m2; n = 12 control, BMI = 34.4 ± 4.43 kg/m2). All participants were given access to a secure platform for data tracking and video conferencing with the research team. The intervention group met with the medical doctor once per month and with a registered dietitian, weekly. Control participants met with the research team at baseline and at 12 weeks. Independent samples t-tests and Chi-square tests were used via SPSS version 24 with significance set to p < 0.05. Results There was a significant difference between the intervention and control groups for body weight loss (7.3 ± 5.2 versus 1.2 ± 3.9 kg, respectively, p < 0.05) as well as for percent body weight loss (7.16 ± 4.4 versus 1.5 ± 4.1%, respectively, p < 0.05). Clinically significant weight loss was achieved in 9 out of 13 (69.2%) in the intervention group versus 1 out of 12 (8%) in the control group. Discussion Mobile phone-based health coaching may promote weight loss. Weekly video conferencing with education may be an applicable tool for inducing significant body weight loss in obese individuals.

Comparison of BMI and Body Composition in College Football Players: 3589 Board #28 June 4, 8: 00 AM - 9: 30 AM.

Competitive runners aim to maximize performance by optimizing movement efficiency at a high level of physical exertion. Thus, there is a need to identify modifiable factors which influence running economy (RE). PURPOSE: To evaluate the relationship between body composition and mass distribution parameters of the legs to RE in competitive male distance runners. METHODS: Eighteen elite male runners (age 18-29) participated in this study. Whole body dual energy x-ray absorptiometry (DXA) was performed on each subject to obtain body composition measurements. The right and left thigh and shank regions were manually selected in DXA analysis software to measure lean mass, fat mass, bone mineral content, and bone mineral density. The mean data from both legs were used for all analyses. For each tissue type, the ratio of thigh to shank mass was computed to quantify relative mass distribution. Additionally, the masses of each tissue type of the thigh, shank, and whole leg were normalized to total body mass.Each runner performed an incremental treadmill running protocol, where they ran at progressively faster submaximal speeds for four minute intervals, followed by four minutes of recovery, before completing a VO2max test. Breath-by-breath VO2 and VCO2 were measured with a metabolic cart. RE was computed for the greatest running speed at which respiratory exchange ratio (RER) remained below 1.0. A stepwise linear regression was performed to determine if any absolute or normalized regional body composition or mass distribution variables were associated with RE. RESULTS: Mean ± SD metabolic data for the speeds analyzed were: VO2: 61.9 ± 6.7 mL O2/kg/min, RER: 0.98 ± 0.02, RE: 201.4 ± 10.7 ml O2/kg/km. Mass of the whole leg normalized to total body mass was the first variable selected into the stepwise model (adjusted r2=0.294, p=0.012), and bone mass of the shank normalized to total body mass was the second variable entered into the model (total adjusted r2=0.460, p=0.028). CONCLUSIONS: In this homogenous group, minimal inter-individual variation in body fat would be expected. Thus, relatively more mass distributed in the legs implies less mass in the remainder of the body to move through space. Bone mass in the shank may be related to shank length, which could influence biomechanical factors associated with efficiency.