John C. Young

The Effects of Adding Leucine to Pre and Postexercise Carbohydrate Beverages on Acute Muscle Recovery From Resistance Training

Stock, MS, Young, JC, Golding, LA, Kruskall, LJ, Tandy, RD, Conway-Klaassen, JM, and Beck, TW. The effects of adding leucine to pre and postexercise carbohydrate beverages on acute muscle recovery from resistance training. J Strength Cond Res 24(8): 2211-2219, 2010-The present study examined the effects of adding leucine to pre and postexercise carbohydrate beverages on selected markers of muscle damage, delayed-onset muscle soreness (DOMS), and squat performance for up to 72 hours after lower-body resistance training. Seventeen resistance trained men (mean ± SD age 22.9 ± 2.9 years) and 3 resistance trained women (mean ± SD age 21.6 ± 2.6 years) performed 6 sets of squats to fatigue using 75% of the 1 repetition maximum. Each subject consumed a carbohydrate beverage 30 minutes before and immediately after exercise with or without the addition of 22.5 mg·kg−1 (45 mg·kg−1 total) of leucine in a randomized, double-blind fashion. Serum creatine kinase (CK), lactate dehydrogenase (LDH), and DOMS were analyzed immediately before (TIME1), 24 (TIME2), 48 (TIME3), and 72 (TIME4) hours after exercise. The subjects repeated the squat protocol at TIME4 to test recovery. No differences were observed between groups for squat performance, defined as the total number of repetitions performed during 6 sets of squats, for both TIME1 and TIME4. The addition of leucine did not significantly decrease CK and LDH activity or DOMS. These results suggested that adding leucine to carbohydrate beverages did not affect acute muscle recovery and squat performance during both initial testing and during a subsequent exercise bout 72 hours later in resistance trained subjects.

The effect of creatine supplementation on glucose uptake in rat skeletal muscle.

Glucose transport in muscle is a function of the muscle metabolic state, as evidenced by the increase in glucose transport which occurs with conditions of altered aerobic metabolism such as hypoxia or contractile activity. The energy state of the muscle can be determined by the muscle phosphocreatine concentration. Dietary supplementation of creatine has been shown to increase both phosphocreatine (PCr) and creatine (TCr) levels in muscle, although not in the same proportion, so that the PCr/TCr ratio falls suggesting an altered energy state in the cell. The purpose of this study was to determine the effect of increased creatine content on glucose uptake in muscle. PCr and TCr were determined in plantaris muscles from rats following five weeks of dietary supplementation of creatine monohydrate (300 mg/kg/day). (3)H-2-deoxyglucose uptake was measured in epitrochlearis muscles incubated in the presence or absence of a maximally stimulating dose of insulin. Despite a significant increase in creatine content in muscle, neither basal nor insulin-stimulated glucose uptake was altered in creatine supplemented rats. Since PCr levels were not increased with creatine supplementation, these results suggest that the actual concentration of PCr is a more important determinant of glucose uptake than the PCr/TCr ratio.

Role of dihydropyridine sensitive calcium channels in glucose transport in skeletal muscle.

Glucose transport in skeletal muscle is a carrier-mediated process activated by insulin and by contractile activity. Since previous evidence suggests a role for calcium influx in the activation of this process, the purpose of this study was to determine if glucose transport is mediated by muscles voltage dependent (dihydropyridine sensitive) calcium channels. Soleus and extensor digitorum longus (EDL) muscles, isolated from rats, were incubated with the calcium channel blocker nifedipine. Basal glucose transport was decreased in both soleus and EDL by nifedipine. Treatment with nifedipine effectively blocked both insulin and contraction stimulated glucose transport in soleus. Conversely, glucose transport in EDL, although reduced, was still significantly increased over basal by both insulin and contraction, due, perhaps, to a relatively greater number of dihydropyridine receptors in EDL. These results provide evidence that contraction stimulated, as well as insulin stimulated, glucose transport is mediated in-part by dihydropyridine receptors in skeletal muscle.

THE EFFECT OF MODERATE CONSUMPTION OF NON-NUTRITIVE SWEETENERS ON GLUCOSE TOLERANCE AND BODY COMPOSITION IN RATS

Glucose tolerance and body composition were determined in male rats given non-nutritive sweeteners (NNS) (aspartame or sucralose) in drinking water. Areas under the curve for glucose and insulin with NNS did not differ from control. NNS treatment had no effect on weight gain or percent body fat. Epididymal fat pad mass was higher with aspartame and the ratio of trunk to total fat was less with sucralose versus control, suggesting that NNS consumption altered body fat distribution.

Vitamin D Status and Bone Mineral Density in Female Collegiate Dancers and Cheerleaders

Bone mineral density reflects an athlete’s cumulative history of energy availability, physical activity, and menstrual status, as well as nutritional and environmental factors. Although sports with high-impact loading are associated with higher bone mineral density than low-impact or non-impact sports, confounding variables are differences in the athletes’ body size and sport-specific training. The purpose of this study was to determine if bone mineral density (BMD) and vitamin D status are different between two groups of female collegiate athletes who have comparable body size/weight requirements, but who engage in qualitatively different training regimens. Full body, spine and dual femur BMD was assessed by dual energy X-ray absorptiometry (DXA) in members of a university pep-dance team (n = 10) or cheer team (n = 9), ages 18-22. Plasma vitamin D status was assessed by ELIZA. There was no significant difference between the groups for total body BMD (1.23 g/cm dance vs 1.22 g/cm cheer, P = 0.70), spine BMD (1.39 g/cm dance vs 1.36 g/cm cheer, P = 0.72) or dual femur BMD (1.20 g/cm dance vs 1.11 g/cm, P = 0.23). Insufficient serum vitamin D status (20-32 ng/mL) was found in 74% of the athletes (27 ± 4 ng/mL, dance and 25 ± 8 ng/mL, cheer). In addition, estimated daily vitamin D and calcium intakes were less than the RDA for both dancers and cheerleaders. Despite nutritional insufficiencies, BMD was not significantly different between the low-impact activity pep dance team and high-impact activity cheer team, suggesting that the type of physical activity was not as important for BMD in these athletes as participating in 20+ hours a week of physical activity, which could have counteracted the negative effects of the nutrient insufficiencies on their bone health.

An Evaluation of Select Physical Activity Exercise Classes (PEX) on Bone Mineral Density: 697 Board #13 June 1, 3: 30 PM - 5: 00 PM.

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Validation of Hexoskin biometric shirt to COSMED K4 b2 metabolic unit in adults during trail running

Abstract Wearable biometric technology use has increased in recent years. The Hexoskin biometric shirt is a wearable technology that monitors heart rate (HR), ventilatory rate (VR), minute ventilation (VE), step count, and energy expenditure (EE). It is unknown whether the Hexoskin biometric shirt produces valid results in the field. Participants (N = 26) completed a self-paced 1.6 km trail run wearing the Hexoskin biometric shirt and the COSMED K4 b2 portable metabolic system. Data for HR, VR, and VE were analyzed in six one-minute increments occurring the first three minutes and the last three minutes of the run. Data for step count and energy expenditure were analyzed for the entire trail run. HR, VR, VE, step count, and EE data were analyzed using Pearson product-moment correlation with significance at p < .05. HR, VE, step count, and EE measures at all time points were not significantly correlated. VR measures at all time points were significantly correlated (p < .001). Our results indicate the Hexoskin biometric shirt provides valid measures of VR. For all other measures, the Hexoskin does not provide valid real time results.