bluuebunny/crossref_metadata_2025 huggingface dataset:
The Acute Effects of Dairy Calcium Intake on Fat Metabolism during Exercise and Endurance Exercise Performance
Authors: White Kimberly M. , Lyle Roseann M. , Flynn Michael G. , Teegarden Dorothy , Donkin Shawn S.
Published: August 2016

The purpose of this study was to test the effect of acute dairy calcium intake on exercise energy metabolism and endurance performance. Trained female runners completed two trials. Each trial consisted of a 90-min glycogen depletion run followed by a self-paced 10K time trial, conducted one hour after consumption of a high dairy (500 mg Ca+2) or low dairy (80 mg Ca+2) meal. During the 90-min run, blood samples and respiratory gases were collected. No treatment main effects of acute dairy intake were found for respiratory exchange ratio (RER), calculated fat oxidation, lactate, glycerol, or 10K time. Following this protocol, acute dairy calcium intake did not alter fat utilization or endurance performance in trained female runners.
Effects of an Exercise Program and a Calcium Supplementation on Bone in Children: A Randomized Control Trial
Authors: Ianc Dorina , Serbescu Carmen , Bembea Marius , Benhamou Laurent , Lespessailles Eric , Courteix Daniel
Published: August 2016

We investigated the effects of calcium supplementation and physical practice on the bone ultrasound properties and trabecular microarchitecture in children. 160 children aged 8−11 were randomly allocated to active or nonactive groups and to receive either a calcium-phosphate or a placebo powder for 6 months. Skeletal status was assessed using an ultrasound technique, which measures the speed of sound (Ad-SoS, m/s) at the phalanx. Bone microarchitecture was characterized by fractal analysis measured on calcaneus radiographs and the result expressed as the Hmean parameter, that has been shown to a good reliability of the bone texture quality. After 6 months, the calcium group had significantly gained Ad-SoS compared to the placebo group (P = 0.01) and Hmean increase was greater in the active than the nonactive group (P < 0.05). Exercise and calcium supplementation had a differential effect on the bone tissue, calcium being rather linked to a systemic effect whereas exercise has acted better onto the skeletal stressed site.
Effects of a Fixed Dietary Intake on Changes in Red Blood Cell Delta-Aminolevulinate Dehydratase Activity and Hemolysis in Female Rhythmic Gymnasts: A Two-Year Follow-Up Study ▀
Authors: Ishizaki Sakuko , Koshimizu Takako , Yanagisawa Kae , Akiyama Yoshiko , Mekada Yuko , Shiozawa Nobuhiro , Takahaski Noriko , Yamakawa Jun , Kawano Yukari
Published: August 2016

This study was to assess the effect of a fixed dietary intake on biomarkers of red blood cell (RBC) biosynthesis and degradation. Over a two-year period, eight collegiate rhythmic gymnasts participated in this study. During the first year, they ate self-selected diets. During the second year, a fixed dietary intake involving consumption of common Japanese foods containing 15 mg iron and 1500 kcal energy was maintained for 4 wk at the beginning of the program. Fixed dietary intakes resulted in significantly increased intakes of protein, minerals and vitamins, and significantly decreased fat intake, but total energy and carbohydrate intakes were unchanged. Mean values of RBC, Hb, Ht, or TIBC were not affected by the intervention. A fixed dietary intervention appeared to enhance RBC turnover by increasing the capacity for erythrocyte biosynthesis and degradation, although the prevalence of iron-deficiency anemia remained unchanged.
The Effects of Caffeine in Women during Aerobic-Dance Bench Stepping
Authors: Ahrens Jennifer N. , Lloyd Lisa K. , Crixell Sylvia H. , Walker John L.
Published: August 2016

People of all ages and fitness levels participate regularly in aerobic-dance bench stepping (ADBS) to increase fitness and control body weight. Any reasonable method for enhancing the experience or effectiveness of ADBS would be beneficial. This study examined the acute effects of a single dose of caffeine on physiological responses during ADBS in women. When compared with a placebo, neither a 3- nor a 6-mg/kg dose of caffeine altered physiological responses or rating of perceived exertion (RPE) in 20 women (age 19–28 y) of average fitness level, not habituated to caffeine, while they performed an ADBS routine. Since neither dose of caffeine had any effect on VO2, Vco2, minute ventilation, respiratory-exchange ratio, rate of energy expenditure, heart rate, or RPE during ADBS exercise, it would not be prudent for a group exercise leader to recommend caffeine to increase energy cost or decrease perception of effort in an ADBS session. Furthermore, caffeine ingestion should not interfere with monitoring intensity using heart rate or RPE during ADBS.
Effects of β-Hydroxy-β-Methylbutyrate on Aerobic-Performance Components and Body Composition in College Students
Authors: Lamboley Cédric R.H. , Royer Donald , Dionne Isabelle J.
Published: August 2016

The aim of this study was to determine the effects of oral β-hydroxy-β-methylbutyrate (HMB) supplementation (3 g/d) on selected components of aerobic performance and body composition of active college students. Subjects were randomly assigned to either an HMB (n = 8) or a placebo (PLA) group (n = 8) for a 5-wk supplementation period during which they underwent interval training 3 times a week on a treadmill. Aerobic-performance components were measured using a respiratory-gas analyzer. Body composition was determined using dual-energy X-ray absorptiometry. After the intervention, there were significant differences (P < 0.05) between the 2 groups in gains in maximal oxygen consumption (+8.4% for PLA and +15.5% for HMB) and in respiratory-compensation point (+8.6% for PLA and +13.4% for HMB). Regarding body composition, there were no significant differences. The authors concluded that HMB supplementation positively affects selected components of aerobic performance in active college students.
Creatine and Glycerol Hyperhydration in Trained Subjects before Exercise in the Heat
Authors: Easton Chris , Turner Stephen , Pitsiladis Yannis P.
Published: August 2016

The authors examined the effects of combined creatine (Cr) and glycerol (Gly) supplementation on responses to exercise in the heat. Subjects (N = 24) were matched for body mass and assigned to either a Cr or placebo (Pl) group. Twice daily during two 7-d supplementation regimens, the Cr group received 11.4 g of Cr·H2O and the Pl group received 11.4 g of glucose. Subjects in both groups also ingested 1 g of Gly/kg body mass (twice daily) in either the first or the second supplementation regimen. This design allowed 4 possible combinations of supplements to be examined (Pl/Pl, Pl/Gly, Cr/Pl, and Cr/Gly). Exercise trials were conducted pre- and post supplementation at 30 °C and 70% relative humidity. In the Pl group, total body water (TBW) increased by 0.50 ± 0.28 L after Gly and in the Cr group by 0.63 ± 0.33 L after Pl and by 0.87 ± 0.21 L after Gly. Both Cr/Pl and Cr/Gly resulted in significantly attenuated heart rate, rectal temperature, and perceived effort during exercise, although no regimen had any effect on performance. The addition of Gly to Cr significantly increased TBW more than Cr alone (P = 0.02) but did not further enhance the attenuation in HR, Tre, and RPE during exercise. These data suggest that combined Cr and Gly is an effective method of hyper hydration capable of reducing thermal and cardiovascular responses.
Eight Weeks of Aromatase Inhibition Using the Nutritional Supplement Novedex XT: Effects in Young, Eugonadal Men
Authors: Willoughby Darryn S. , Wilborn Colin , Taylor Lemuel , Campbell William
Published: August 2016

This study examined the effects of an aromatase-inhibiting nutritional supplement on serum steroid hormones, body composition, and clinical safety markers. Sixteen eugonadal young men ingested either Novedex XT™ or a placebo daily for 8 wk, followed by a 3-wk washout period. Body composition was assessed and blood and urine samples obtained at weeks 0, 4, 8, and 11. Data were analyzed by 2-way repeated-measures ANOVA. Novedex XT resulted in average increases of 283%, 625%, 566%, and 438% for total testosterone (P = 0.001), free testosterone (P = 0.001), dihydrotestosterone (P = 0.001), and the testosterone:estrogen ratio (P = 0.001), respectively, whereas fat mass decreased 3.5% (P = 0.026) during supplementation. No significant differences were observed in blood and urinary clinical safety markers or for any of the other serum hormones (P > 0.05). This study indicates that Novedex XT significantly increases serum androgen levels and decreases fat mass.
The Impact of Varying Dietary Protein on Serum IGF-I, IGFBP-1, and IGFBP-3 during 6 Days of Physical Activity
Authors: Ormsbee Michael J. , Clapper Jeffrey A. , Clapper Joan L. , Vukovich Matthew D.
Published: August 2016

This study was designed to investigate the impact of dietary protein intake on serum concentrations of IGF-I and IGFBP-1 and relative amounts of serum IGFBP-3 during 6 d of physical activity. Ten men (23.8 ± 2.0 y of age) were assigned to 1 of 3 trials in a random crossover design. Each trial was isocaloric but with varying amounts of dietary protein: 50 g, 100 g, or 200 g. Subjects expended 500 kcal through treadmill running or weightlifting on alternate days for 6 d. Fasting blood samples were obtained for measurement of IGF-I, IGFBP-1, and IGFBP-3. Pre–post 24-h urine was measured for urea nitrogen. 50 g/d of protein resulted in a negative nitrogen balance, whereas 100 g/d and 200 g/d resulted in a positive nitrogen balance—200 g greater (P < 0.05) than 50 g and 100 g. Baseline IGF-I, BP-1, and BP-3 were not different among treatments. IGF-I decreased (P = 0.002) during the 6 d. Post intervention IGFBP-I was greater (P = 0.03) than at baseline. Post intervention IGFBP-3 values were not different from baseline or between trials. A 6-d modification of protein intake, while in energy balance, during a strength and conditioning program does not appear to modify serum concentrations of IGF-I or IGFBP-1 or relative amounts of IGFBP-3.
Carbohydrate Loading and Female Endurance Athletes: Effect of Menstrual-Cycle Phase
Authors: McLay Rebecca T. , Thomson Christine D. , Williams Sheila M. , Rehrer Nancy J.
Published: August 2016

This study compared 3 d of carbohydrate loading (CHOL; 8.4 g·kg−1·d−1 carbohydrate) in female eumenorrheic athletes with 3 d of an isoenergetic normal diet (NORM; 5.2 g·kg−1·d−1 carbohydrate) and examined the effect of menstrual-cycle phase on performance, muscle-glycogen concentration [glyc], and substrate utilization. Nine moderately trained eumenorrheic women cycled in an intermittent protocol varying in intensity from 45% to 75% VO2max for 75 min, followed by a 16-km time trial at the midfollicular (MF) and midluteal (ML) phases of the menstrual cycle on NORM and CHOL. Time-trial performance was not affected by diet (CHOL 26.10 ± 1.04 min, NORM 26.16 ± 1.35 min; P = 0.494) or menstrual-cycle phase (MF 26.05 ± 1.10 min, ML 26.23 ± 1.33 min; P = 0.370). Resting [glyc] was lowest in the MF phase after NORM (575 ± 145 mmol·kg−1·dw−1), compared with the MF phase after CHOL (728 mmol·kg−1·dw−1) and the ML phase after CHOL and NORM (756 and 771 mmol·kg−1·dw−1, respectively). No effect of phase on substrate utilization during exercise was observed. These data support previous observations of greater resting [glyc] in the ML than the MF phase of the menstrual cycle and suggest that lower glycogen storage in the MF phase can be overcome by carbohydrate loading.
Endurance Training on Low-Carbohydrate and Grain-Based Diets: A Case Study
Authors: Rosenkranz Richard R. , Cook Chad M. , Haub Mark D.
Published: August 2016

Purpose:

To illustrate the effects of low-carbohydrate (LC) and grain-based (GB) diets on body composition, biomarkers, athletic training, and performance in an elite triathlete.

Methods:

The athlete followed 2 dietary interventions for 14 d while maintaining a prescheduled training program. Pre- and post intervention measurements for each diet included plasma and serum samples, resting energy expenditure, body composition, and a performance bike ride.

Results:

Compared with the GB diet, the LC diet elicited more disruptions to training and unfavorable subjective experiences. Total cholesterol, HDL cholesterol, LDL cholesterol, ratings of perceived exertion, and heart rate were elevated on the LC diet. Blood insulin, resting lactate, post exercise lactate, and C-reactive protein were lowest on the LC diet.

Conclusion:

The LC diet resulted in both favorable and unfavorable outcomes. The primary observation was a disruption to scheduled training on the LC diet. Researchers should consider how the potential mediating effect of disruptions to training could influence pretest–posttest designs.
Drink-Flavor Change’s Lack of Effect on Endurance Cycling Performance in Trained Athletes
Authors: Desbrow Ben , Minahan Clare , Leveritt Michael
Published: August 2016

This study investigated whether a change in beverage favor during endurance cycling improves subsequent performance. Eight trained male athletes (age 24.3 ± 3.9 y, weight 74.7 ± 6.0 kg, peak O2 uptake [VO2peak] 65.4 ± 5.4 mL·kg−1·min−1; mean ± SD) undertook 3 trials, with training and diet being controlled. Trials consisted of 120 min of steady-state (SS) cycling at ~70% VO2peak, immediately followed by a 7-kJ/kg time trial (TT). During exercise subjects were provided with fluids every 20 min. After 80 min of SS cycling subjects either continued drinking the same-favor sports drink or changed to an alternate favor—either an alternate-favor sports drink (AFSD) or cola. All beverages were carbohydrate and volume matched. Changing drink favor caused no significant change in TT time (sports drink 27:16 ± 03:12, AFSD 27:06 ± 03:16, cola 27:03 ± 02:42; min: s). The various favors produced no treatment effects on heart rate, blood glucose, or rating of perceived exertion throughout the SS exercise protocol. The influence of other taste variables such as palatability, bitterness, or timing of favor change on endurance-exercise performance requires more rigorous investigation.
The Effect of Probiotics on Respiratory Infections and Gastrointestinal Symptoms during Training in Marathon Runners
Authors: Kekkonen Riina A. , Vasankari Tommi J. , Vuorimaa Timo , Haahtela Tari , Julkunen Ilkka , Korpela Riitta
Published: August 2016

Heavy exercise is associated with an increased risk of upper respiratory tract infections. Strenuous exercise also causes gastrointestinal (GI) symptoms. In previous studies probiotics have reduced respiratory tract infections and GI symptoms in general populations including children, adults, and the elderly. These questions have not been studied in athletes before. The purpose of this study was to investigate the effect of probiotics on the number of healthy days, respiratory infections, and GI-symptom episodes in marathon runners in the summer. Marathon runners (N = 141) were recruited for a randomized, double-blind intervention study during which they received Lactobacillus rhamnosus GG (LGG) or placebo for a 3-mo training period. At the end of the training period the subjects took part in a marathon race, after which they were followed up for 2 wk. The mean number of healthy days was 79.0 in the LGG group and 73.4 in the placebo group (P = 0.82). There were no differences in the number of respiratory infections or GI-symptom episodes. The duration of GI-symptom episodes in the LGG group was 2.9 vs. 4.3 d in the placebo group during the training period (P = 0.35) and 1.0 vs. 2.3 d, respectively, during the 2 wk after the marathon (P = 0.046). LGG had no effect on the incidence of respiratory infections or GI-symptom episodes in marathon runners, but it seemed to shorten the duration of GI-symptom episodes.
The Effect of 4 Wk of Oral Echinacea Supplementation on Serum Erythropoietin and Indices of Erythropoietic Status
Authors: Whitehead Malcolm T. , Martin Tyler D. , Scheett Timothy P. , Webster Michael J.
Published: August 2016

The purpose of this investigation was to determine whether echinacea supplementation results in alterations of erythroid growth factors and erythropoietic status. Twenty-four men age 24.9 ± 4.2 y, height 1.7 ± 0.8 m, weight 87.9 ± 14.6 kg, and 19.3% ± 6.5% body fat were grouped using a double-blind design and self-administered an 8000-mg/d dose of either echinacea (ECH) or placebo (PLA) in 5 × 400 mg × 4 times/d for 28 d. Blood samples were collected and analyzed for red blood cells (RBCs), hematocrit (Hct), hemoglobin (Hb), mean corpuscular volume, mean corpuscular hemoglobin content, prostaglandin E2, ferritin, erythropoietin (EPO), interleukin 3 (IL-3), and granulocyte-macrophage-colony-stimulating factor using automated flow cytometry and ELISA. ANOVA was used to determine significant differences (P ≤ 0.05). EPO was greater (P < 0.001) in ECH at Days 7, 14, and 21 and refected a 44%, 63%, and 36% increase, respectively. IL-3 was greater (P = 0.011) in ECH at Days 14 and 21, which indicated a 65% and 73% increase, respectively. These data indicate that ECH supplementation resulted in an increase in EPO and IL-3 but did not significantly alter RBCs, Hb, or Hct.
A Meta-Analysis of the Effects of Glycerol-Induced Hyperhydration on Fluid Retention and Endurance Performance
Authors: Goulet Eric D.B. , Aubertin-Leheudre Mylène , Plante Gérard E. , Dionne Isabelle J.
Published: August 2016

The authors determined, through a meta-analytic approach, whether glycerol-induced hyperhydration (GIH) enhances fluid retention and increases endurance performance (EP) significantly more than water-induced hyperhydration (WIH). Collectively, studies administered 23.9 ± 2.7 mL of fuid/kg body weight (BW) with 1.1 ± 0.2 g glycerol/kg BW, and hyperhydration was measured 136 ± 15 min after its onset. Compared with WIH, GIH increased fluid retention by 7.7 ± 2.8 mL/kg BW (P < 0.01; pooled effect size [PES]: 1.64 ± 0.80, P < 0.01, N = 14). The use of GIH was associated with an improvement in EP of 2.62% ± 1.60% (P = 0.047; PES: 0.35 ± 0.13, P = 0.014, N = 4). Unarguably, GIH significantly enhances fluid retention better than WIH. Because of the dearth of data, the effect of GIH on EP must be further investigated before more definitive conclusions can be drawn as to its ergogenic property.
Effect of Protein Ingestion on Energy Expenditure and Substrate Utilization after Exercise in Middle-Aged Women
Authors: Benton Melissa J. , Swan Pamela D.
Published: August 2016

Research suggests that ingesting protein after resistance exercise (RE) increases muscle protein synthesis and results in greater muscle gains. The effect on energy expenditure and substrate utilization, however, is unclear. This study evaluated the effect of RE and post exercise protein on recovery energy expenditure and substrate utilization in 17 women (age 46.5 ± 1.2 y). A whey-protein supplement (120 kcal, 30 g protein) was ingested immediately after 1 bout of RE (PRO) and a non caloric placebo after another (PLA). VO2 and respiratory-exchange ratio (RER) were measured before and for 120 min after each exercise session. RE resulted in a significant increase in VO2 that persisted through 90 min of recovery (P < 0.01) and was not affected by protein supplementation. RE significantly lowered RER, resulting in an increase in fat oxidation for both PLA and PRO (P < 0.01). For PRO, however, RER returned to baseline values earlier than for PLA, resulting in a reduced fat-oxidation response (P = 0.02) and earlier return to pre exercise baseline values than for PLA. Substrate utilization was significantly different between conditions (P = 0.02), with fat contributing 77.76% ± 2.19% for PLA and 72.12% ± 2.17% for PRO, while protein oxidation increased from 17.18% ± 1.33% for PLA to 20.82% ± 1.47% for PRO. Post exercise protein did not affect energy expenditure, but when protein was available as an alternate fuel fat oxidation was diminished. Based on these findings it might be beneficial for middle-aged women to delay protein intake after RE to maximize fat utilization.
Parallel Increases in Phosphocreatine and Total Creatine in Human Vastus Lateralis Muscle during Creatine Supplementation
Authors: Brault Jeffrey J. , Towse Theodore F. , Slade Jill M. , Meyer Ronald A.
Published: August 2016

Short-term creatine supplementation is reported to result in a decreased ratio of phosphocreatine (PCr) to total creatine (TCr) in human skeletal muscle at rest. Assuming equilibrium of the creatine kinase reaction, this decrease in PCr:TCr implies increased cytoplasmic ADP and decreased Gibbs free energy of ATP hydrolysis in muscle, which seems contrary to the reported ergogenic benefits of creatine supplementation. This study measured changes in PCr and TCr in vastus lateralis muscle of adult men (N = 6, 21–35 y old) during and 1 day after 5 d of creatine monohydrate supplementation (0.43 g·kg body weight−1·d−1) using noninvasive 31P and 1H magnetic-resonance spectroscopy (MRS). Plasma and red-blood-cell creatine increased by 10-fold and 2-fold, respectively, by the third day of supplementation. MRS-measured skeletal muscle PCr and TCr increased linearly and in parallel throughout the 5 d, and there was no significant difference in the percentage increase in muscle PCr (11.7% ± 2.3% after 5 d) vs. TCr (14.9% ± 4.1%) at any time point. The results indicate that creatine supplementation does not alter the PCr:TCr ratio, and hence the cytoplasmic Gibbs free energy of ATP hydrolysis, in human skeletal muscle at rest.
Amino Acids and the Brain: Do They Play a Role in “Central Fatigue”?
Authors: Meeusen Romain , Watson Phil
Published: August 2016

It is clear that the cause of fatigue is complex, infuenced by both events occurring in the periphery and the central nervous system (CNS). It has been suggested that exercise-induced changes in serotonin (5-HT), dopamine (DA), and noradrenaline (NA) concentrations contribute to the onset of fatigue during prolonged exercise. Serotonin has been linked to fatigue because of its documented role in sleep, feelings of lethargy and drowsiness, and loss of motivation, whereas increased DA and NA neurotransmission favors feelings of motivation, arousal, and reward. 5-HT has been shown to increase during acute exercise in running rats and to remain high at the point of fatigue. DA release is also elevated during exercise but appears to fall at exhaustion, a response that may be important in the fatigue process. The rates of 5-HT and DA/NA synthesis largely depend on the peripheral availability of the amino acids tryptophan (TRP) and tyrosine (TYR), with increased brain delivery increasing serotonergic and DA/NA activity, respectively. TRP, TYR, and the branched-chained amino acids (BCAAs) use the same transporter to pass through the blood-brain barrier, meaning that the plasma concentration ratio of these amino acids is thought to be a very important marker of neurotransmitter synthesis. Pharmacological manipulation of these neurotransmitter systems has provided support for an important role of the CNS in the development of fatigue. Work conducted over the last 20 y has focused on the possibility that manipulation of neurotransmitter precursors may delay the onset of fatigue. Although there is evidence that BCAA (to limit 5-HT synthesis) and TYR (to elevate brain DA/NA) ingestion can influence perceived exertion and some measures of mental performance, the results of several apparently well-controlled laboratory studies have yet to demonstrate a clear positive effect on exercise capacity or performance. There is good evidence that brain neurotransmitters can play a role in the development of fatigue during prolonged exercise, but nutritional manipulation of these systems through the provision of amino acids has proven largely unsuccessful.
Role of Amino Acids and Peptides in the Molecular Signaling in Skeletal Muscle after Resistance Exercise
Authors: Koopman René
Published: August 2016

Resistance exercise can effectively result in an increase in muscle mass, or hypertrophy, which generally becomes apparent after several weeks of training. Muscle hypertrophy requires muscle protein synthesis to exceed protein breakdown during an extended time period. It has been firmly established that the interaction between exercise and nutrition (i.e., protein intake) is necessary to attain net protein accretion in skeletal muscle. The stimulation of protein synthesis is caused in part by stimulation of mRNA translation initiation. There is relatively little information on the response of intracellular signaling controlling mRNA translation to exercise and nutrition, especially in humans, but the available data in humans seem to suggest that a single bout of resistance exercise does not substantially enhance PI-3 kinase/mTOR signaling during the first 2 h after exercise. Moreover, it is demonstrated that the ingestion of protein or amino acids after exercise is crucial to further stimulate molecular signaling that controls translation initiation. The aim of this review is to provide an overview of the intracellular signaling related to translational control and to provide a summary of the current knowledge about the response of the signaling pathways controlling the anabolic response to exercise and nutrient intake in vivo in humans.
Food-Derived Bioactive Peptides Influence Gut Function
Authors: Moughan Paul J. , Fuller Malcolm F. , Han Kyoung-Sik , Kies Arie K. , Miner-Williams Warren
Published: August 2016

Bioactive peptides either present in foods or released from food proteins during digestion have a wide range of physiological effects, including on gut function. Many of the bioactive peptides characterized to date that influence gut motility, secretion, and absorption are opioid agonists or antagonists. The authors review a body of experimental evidence that demonstrates an effect of peptides from food proteins on endogenous (nondietary) protein flow at the terminal ileum of simple-stomached mammals, including adult humans. At least some dietary peptides (1000-5000 Da) significantly enhance the loss of protein from the small intestine, causing an increased amount of protein to enter the colon. Food-derived peptides appear to either stimulate protein secretion into the gut lumen or inhibit amino acid reabsorption or influence both processes simultaneously. The effect of dietary peptides on small-intestine secretory-protein dynamics is discussed in the context of the major components of gut endogenous protein, sloughed cells, enzymatic secretions, mucin, and bacterial protein.
Role of Protein and Hydrolysates before Exercise
Authors: Tipton Kevin D.
Published: August 2016

Adaptations to exercise training are determined by the response of metabolic and molecular mechanisms that determine changes in proteins. The type, intensity, and duration of exercise, as well as nutrition, determine these responses. The importance of protein, in the form of intact proteins, hydrolysates, or free amino acids, for exercise adaptations is widely recognized. Exercise along with protein intake results in accumulation of proteins that influence training adaptations. The total amount of protein necessary to optimize adaptations is less important than the type of protein, timing of protein intake, and the other nutrients ingested concurrently with the protein. Acute metabolic studies offer an important tool to study the responses of protein balance to various exercise and nutritional interventions. Recent studies suggest that ingestion of free amino acids plus carbohydrates before exercise results in a superior anabolic response to exercise than if ingested after exercise. However, the difference between pre- and post exercise ingestion of intact proteins is not apparent. Thus, the anabolic response to exercise plus protein ingestion seems to be determined by the interaction of timing of nutrient intake in relation to exercise and the nutrients ingested. More research is necessary to delineate the optimal combination of nutrients and timing for various types of training adaptations. Protein and amino acid intake have long been deemed important for athletes and exercising individuals. Olympic athletes, from the legendary Milo to many in the 1936 Berlin games, reportedly consumed large amounts of protein. Modern athletes may consume slightly less than these historical figures, yet protein is deemed extremely important by most. Protein is important as a source of amino acids for recovery from exercise and repair of damaged tissues, as well as for adaptations to exercise training, such as muscle hypertrophy and mitochondrial biogenesis.
Carbohydrate-Protein Drinks Do Not Enhance Recovery from Exercise-Induced Muscle Injury
Authors: Green Michael S. , Corona Benjamin T. , Doyle J. Andrew , Ingalls Christopher P.
Published: August 2016

This study examined the effects of carbohydrate (CHO), carbohydrate-protein (CHO+PRO), or placebo (PLA) beverages on recovery from novel eccentric exercise. Female participants performed 30 min of downhill treadmill running (–12% grade, 8.0 mph), followed by consumption of a CHO, CHO+PRO, or PLA beverage immediately, 30, and 60 min after exercise. CHO and CHO+PRO groups (n = 6 per group) consumed 1.2 g · kg body weight–1 · hr–1 CHO, with the CHO+PRO group consuming an additional 0.3 g · kg body weight–1 · hr–1 PRO. The PLA group (n = 6) received an isovolumetric noncaloric beverage. Maximal isometric quadriceps strength (QUAD), lower extremity muscle soreness (SOR), and serum creatine kinase (CK) were assessed preinjury (PRE) and immediately and 1, 2, and 3 d postinjury to assess exercise-induced muscle injury and rate of recovery. There was no effect of treatment on recovery of QUAD (p = .21), SOR (p = .56), or CK (p = .59). In all groups, QUAD was reduced compared with PRE by 20.6% ± 1.5%, 17.2% ± 2.3%, and 11.3% ± 2.3% immediately, 1, and 2 d postinjury, respectively (p < .05). SOR peaked at 2 d postinjury (PRE vs. 2 d, 3.1 ± 1.0 vs. 54.0 ± 4.8 mm, p < .01), and serum CK peaked 1 d postinjury (PRE vs. 1 d, 138 ± 47 vs. 757 ± 144 U/L, p < .01). In conclusion, consuming a CHO+PRO or CHO beverage immediately after novel eccentric exercise failed to enhance recovery of exercise-induced muscle injury differently than what was observed with a PLA drink.
Effect of Glycine Propionyl-L-Carnitine on Aerobic and Anaerobic Exercise Performance
Authors: Smith Webb A. , Fry Andrew C. , Tschume Lesley C. , Bloomer Richard J.
Published: August 2016

The purpose of this study was to evaluate the effect of glycine propionyl-Lcarnitine (GPLC) supplementation and endurance training for 8 wk on aerobicand anaerobic-exercise performance in healthy men and women (age 18–44 yr). Participants were randomly assigned to 1 of 3 groups: placebo (n = 9), 1 g/d GPLC (n = 11), or 3 g/d GPLC (n = 12), in a double-blind fashion. Muscle carnitine (vastus lateralis), VO2peak, exercise time to fatigue, anaerobic threshold, anaerobic power, and total work were measured at baseline and after an 8-wk aerobic-training program. There were no statistical differences (p > .05) between or within the 3 groups for any performance-related variable or muscle carnitine concentrations after 8 wk of supplementation and training. These results suggest that up to 3 g/d GPLC for 8 wk in conjunction with aerobic-exercise training is ineffective for increasing muscle carnitine content and has no significant effects on aerobic- or anaerobic-exercise performance.
Effect of Prior Exercise on Postprandial Triglycerides in Overweight Young Women after Ingesting a High-Carbohydrate Meal
Authors: Mitchell Joel B. , Rowe James R. , Shah Meena , Barbee James J. , Watkins Austen M , Stephens Chad , Simmons Steve
Published: August 2016

To examine the effect of prior exercise on the postprandial lipid response to a high-carbohydrate meal in normal-weight (NW = BMI h25) and overweight (OW = BMI ≥25) women (age 18–25), 10 NW and 10 OW participants completed 2 conditions separated by 1 month. In the morning, the day after control (CT = no exercise) or exercise conditions (EX = 60 min cycling at 60% VO2peak), participants consumed a high-carbohydrate meal (80% CHO, 15% protein, 5% fat; 75 kJ/kg BM) followed by 6 hr of hourly blood sampling. Blood was analyzed for triglycerides (TG), blood glucose (BG), and insulin (IN). TG levels over the 6-hr period were lower in NW than OW (p = .021) and lower in EX than in CT (p = .006). Area under the curve (AUC) for TG was lower in NW than OW (p = .016) and EX than CT (p = .003). There were nonsignificant tendencies for reduced BG over time (p = .053) and AUC (p = .083), and IN AUC was lower in EX than in CT (p = .040) for both groups and lower in NW than in OW (p = .039). Prior exercise improved TG levels after a high-carbohydrate meal in both groups, and OW women demonstrated a greater postprandial lipemic response than NW regardless of condition. There were tendencies for improved glucose removal with prior exercise in NW vs. OW. Acute exercise can improve postprandial TG responses and might also improve postprandial BG and IN after a large meal in NW and OW young women.
Changes in Resting Metabolic Rate and Substrate Oxidation after 16 Months of Exercise Training in Overweight Adults
Authors: Potteiger Jeffrey A. , Kirk Erik P. , Jacobsen Dennis J. , Donnelly Joseph E.
Published: August 2016

Purpose:

To determine whether 16 months of moderate-intensity exercise training changes resting metabolic rate (RMR) and substrate oxidation in overweight young adults.

Methods:

Participants were randomly assigned to nonexercise control (CON, 18 women, 15 men) or exercise (EX, 25 women, 16 men) groups. EX performed supervised and verified exercise 3–5 d/wk, 20–45 min/session, at 60–75% of heart-rate reserve. Body mass and composition, maximal oxygen consumption (VO2max), RMR, and resting substrate oxidation were assessed at baseline and after 9 and 16 months of training.

Results:

EX men had significant decreases from baseline to 9 months in body mass (94.6 ± 12.4 to 89.2 ± 9.5 kg) and percent fat (28.3 ± 4.6 to 24.5 ± 3.9). CON women had significant increases in body mass (80.2 ± 8.1 to 83.2 ± 9.2 kg) from baseline to 16 months. VO2max increased significantly from baseline to 9 months in the EX men (3.67 ± 0.62 to 4.34 ± 0.58 L/min) and EX women (2.53 ± 0.32 to 3.03 ± 0.42 L/min). RMR increased from baseline to 9 months in EX women (1,583 ± 221 to 1,692 ± 230 kcal/d) and EX men (1,995 ± 184 to 2,025 ± 209 kcal/d). There were no significant differences within genders for either EX or CON in fat or carbohydrate oxidation. Fat oxidation was significantly higher for women than for men at 9 months in both CON and EX groups.

Conclusions:

Regular moderate-intensity exercise in healthy, previously sedentary overweight and obese adults increases RMR but does not alter resting substrate oxidation. Women tend to have higher RMR and greater fat oxidation, when expressed per kilogram fat-free mass, than men.
Effect of Caffeine on Leg-Muscle Pain during Intense Cycling Exercise: Possible Role of Anxiety Sensitivity
Authors: Gliottoni Rachael C. , Motl Robert W.
Published: August 2016

This experiment examined the effect of a moderate dose of caffeine on perceptions of leg-muscle pain during a bout of high-intensity cycling exercise and the role of anxiety sensitivity in the hypoalgesic effect of caffeine on muscle pain during exercise. Sixteen college-age women ingested caffeine (5 mg/kg body weight) or a placebo and 1 hr later completed 30 min of cycling on an ergometer at 80% of peak aerobic capacity. The conditions were completed in a counterbalanced order, and perceptions of leg-muscle pain were recorded during the bouts of exercise. Caffeine resulted in a large reduction in leg-muscle pain-intensity ratings compared with placebo (d = −0.95), and the reduction in leg-muscle pain-intensity ratings was larger in those with lower anxiety-sensitivity scores than those with higher anxiety-sensitivity scores (d = −1.28 based on a difference in difference scores). The results support that caffeine ingestion has a large effect on reducing leg-muscle pain during high-intensity exercise, and the effect is moderated by anxiety sensitivity.
Dose Effect of Caffeine on Testosterone and Cortisol Responses to Resistance Exercise
Authors: Beaven C. Martyn , Hopkins Will G. , Hansen Kier T. , Wood Matthew R. , Cronin John B. , Lowe Timothy E.
Published: August 2016

Introduction:

Interest in the use of caffeine as an ergogenic aid has increased since the International Olympic Committee lifted the partial ban on its use. Caffeine has beneficial effects on various aspects of athletic performance, but its effects on training have been neglected.

Purpose:

To investigate the acute effect of caffeine on the exercise-associated increases in testosterone and cortisol in a double-blind crossover study.

Methods:

Twenty-four professional rugby-league players ingested caffeine doses of 0, 200, 400, and 800 mg in random order 1 hr before a resistance-exercise session. Saliva was sampled at the time of caffeine ingestion, at 15-min intervals throughout each session, and 15 and 30 min after the session. Data were log-transformed to estimate percent effects with mixed modeling, and effects were standardized to assess magnitudes.

Results:

Testosterone concentration showed a small increase of 15% (90% confidence limits, ± 19%) during exercise. Caffeine raised this concentration in a dose-dependent manner by a further small 21% (± 24%) at the highest dose. The 800-mg dose also produced a moderate 52% (± 44%) increase in cortisol. The effect of caffeine on the testosterone:cortisol ratio was a small decline (14%; ± 21%).

Conclusion:

Caffeine has some potential to benefit training outcomes via the anabolic effects of the increase in testosterone concentration, but this benefit might be counteracted by the opposing catabolic effects of the increase in cortisol and resultant decline in the testosterone:cortisol ratio.
Hormonal Response to Carbohydrate Supplementation at Rest and after Resistance Exercise
Authors: Schumm Sean R. , Triplett N. Travis , McBride Jeffrey M. , Dumke Charles L.
Published: August 2016

This investigation examined the anabolic-hormone response to carbohydrate (CHO) supplementation at rest and after resistance exercise. Nine recreationally trained men randomly underwent 4 testing conditions: rest with placebo (RPL), rest with CHO (RCHO), resistance exercise with placebo (EPL), and resistance exercise with CHO (ECHO). The resistance-exercise protocol was four sets of Smith machine squats with a 10-repetition-maximum load, with 90-s rests between sets. Participants then consumed either a placebo or CHO (24% CHO, 1.5 g/kg) drink. Blood was taken before exercise (Pre), immediately after testing (Post), and then 15 (15P), 30 (30P), and 60 (60P) min after drink ingestion. Blood was analyzed for cortisol, glucose, insulin, and total testosterone (TTST). Cortisol did not change significantly in any condition. Glucose concentrations increased significantly from Pre to 15P and 30P during RCHO and Pre to 15P, 30P, and 60P in ECHO (p ≤&.05). Insulin concentrations increased significantly from Pre to 15P, 30P, and 60P in the RCHO and ECHO conditions (p ≤&.05). There were no significant changes in TTST concentrations during RPL or RCHO. Both EPL and ECHO demonstrated a significant elevation in TTST concentrations from Pre to Post (p ≤&.05). During ECHO, TTST concentrations at 60P were significantly lower than Pre levels (p ≤&.05), but there were no significant treatment differences in TTST concentrations at any time point during the EPL and ECHO conditions. Ingesting CHO after resistance exercise resulted in decreased TTST concentrations during recovery, although the mechanism is unclear.
Effect of Preexercise Meals with Different Glycemic Indices and Loads on Metabolic Responses and Endurance Running
Authors: Chen Ya Jun , Wong Stephen H. , Wong Chun Kwok , Lam Ching Wan , Huang Ya Jun , Siu Parco M.
Published: August 2016

This study examined the effect of ingesting 3 isocaloric meals with different glycemic indices (GI) and glycemic loads (GL) 2 hr before exercise on metabolic responses and endurance running performance. Eight male runners completed 3 trials in a randomized order, separated by at least 7 days. Carbohydrate (CHO) content (%), GI, and GL were, respectively, 65%, 79, and 82 for the high-GI/high-GL meal (H-H); 65%, 40, and 42 for the low-GI/low-GL meal (L-L); and 36%, 78, and 44 for the high-GI/low-GL meal (H-L). Each trial consisted of a 1-hr run at 70% VO2max, followed by a 10-km performance run. Low-GL diets (H-L and L-L) were found to induce smaller metabolic changes during the postprandial period and during exercise, which were characterized by a lower CHO oxidation in the 2 trials (p < .05) and a concomitant, higher glycerol and free-fatty-acid concentration in the H-L trial (p < .05). There was no difference, however, in time to complete the preloaded 10-km performance run between trials. This suggests that the GL of the preexercise meal has an important role in determining subsequent metabolic responses.
Influence of Carbohydrate-Protein Beverage on Cycling Endurance and Indices of Muscle Disruption
Authors: Valentine Rudy J. , Saunders Michael J. , Todd M. Kent , St. Laurent Thomas G.
Published: August 2016

Carbohydrate–protein (CHO+Pro) beverages reportedly improve endurance and indices of muscle disruption, but it is unclear whether these effects are related to total energy intake or specific effects of protein.

Purpose:

The authors examined effects of CHO+Pro on time to exhaustion and markers of muscle disruption compared with placebo (PLA) and carbohydrate beverages matched for carbohydrate (CHO) and total calories (CHO+CHO).

Methods:

Eleven male cyclists completed 4 rides to exhaustion at 75% VO2peak. Participants consumed 250 ml of PLA, CHO (7.75%), CHO+CHO (9.69%), or CHO+Pro (7.75%/1.94%) every 15 min until fatigue, in a double-blind design.

Results:

Time to exhaustion was significantly longer (p < .05) in CHO+Pro (126.2 ± 25.4 min) and CHO+CHO (121.3 ± 36.8) than PLA (107.1 ± 30.3). CHO (117.5 ± 24.2) and PLA were not significantly different. Similarly, CHO+Pro was not significantly different from CHO and CHO+CHO. Postexercise plasma creatine kinase was lower after CHO+Pro (197.2 ± 149.2 IU/L) than PLA (407.4 ± 391.3), CHO (373.2 ± 416.6), and CHO+CHO (412.3 ± 410.2). Postexercise serum myoglobin was lower in CHO+Pro (47.0 ± 27.4 ng/mL) than all other treatments (168.8 ± 217.3, 82.6 ± 71.3, and 72.0 ± 75.8). Postexercise leg extensions at 70% 1RM were significantly greater 24 hr after CHO+Pro (11.3 ± 4.1) than PLA (8.8 ± 3.7), CHO (9.7 ± 4.3), and CHO+CHO (9.5 ± 3.6).

Conclusion:

These findings suggest that at least some of the reported improvements in endurance with CHO+Pro beverages might be related to caloric differences between treatments. Postexercise improvements in markers of muscle disruption with CHO+Pro ingestion appear to be independent of carbohydrate and caloric content and were elicited with beverages consumed only during exercise.
Development of Individual Hydration Strategies for Athletes
Authors: Maughan Ronald J. , Shirreffs Susan M.
Published: August 2016

Athletes are encouraged to begin exercise well hydrated and to consume sufficient amounts of appropriate fluids during exercise to limit water and salt deficits. Available evidence suggests that many athletes begin exercise already dehydrated to some degree, and although most fail to drink enough to match sweat losses, some drink too much and a few develop hyponatremia. Some simple advice can help athletes assess their hydration status and develop a personalized hydration strategy that takes account of exercise, environment, and individual needs. Preexercise hydration status can be assessed from urine frequency and volume, with additional information from urine color, specific gravity, or osmolality. Change in hydration during exercise can be estimated from the change in body mass that occurs during a bout of exercise. Sweat rate can be estimated if fluid intake and urinary losses are also measured. Sweat salt losses can be determined by collection and analysis of sweat samples, but athletes losing large amounts of salt are likely to be aware of the taste of salt in sweat and the development of salt crusts on skin and clothing where sweat has evaporated. An appropriate drinking strategy will take account of preexercise hydration status and of fluid, electrolyte, and substrate needs before, during, and after a period of exercise. Strategies will vary greatly between individuals and will also be influenced by environmental conditions, competition regulations, and other factors.
Creatine, Arginine α-Ketoglutarate, Amino Acids, and Medium-Chain Triglycerides and Endurance and Performance
Authors: Little Jonathan. P. , Forbes Scott C. , Candow Darren G. , Cornish Stephen M. , Chilibeck Philip D.
Published: August 2016

Creatine (Cr) supplementation increases muscle mass, strength, and power. Arginine α-ketoglutarate (A-AKG) is a precursor for nitric oxide production and has the potential to improve blood flow and nutrient delivery (i.e., Cr) to muscles. This study compared a commercial dietary supplement of Cr, A-AKG, glutamine, taurine, branchedchain amino acids, and medium-chain triglycerides with Cr alone or placebo on exercise performance and body composition. Thirty-five men (~23 yr) were randomized to Cr + A-AKG (0.1 g · kg−1 · d−1 Cr + 0.075 g · kg−1 · d−1 A-AKG, n = 12), Cr (0.1 g · kg−1 · d−1, n = 11), or placebo (1 g · kg−1 · d−1 sucrose, n = 12) for 10 d. Body composition, muscle endurance (bench press), and peak and average power (Wingate tests) were measured before and after supplementation. Bench-press repetitions over 3 sets increased with Cr + A-AKG (30.9 ==6.6 → 34.9 ± 8.7 reps; p < .01) and Cr (27.6 ± 5.9 → 31.0 ± 7.6 reps; p < .01), with no change for placebo (26.8 ± 5.0 → 27.1 ± 6.3 reps). Peak power significantly increased in Cr + A-AKG (741 ± 112 → 794 ± 92 W; p < .01), with no changes in Cr (722 ± 138 → 730 ± 144 W) and placebo (696 ± 63 → 705 ± 77 W). There were no differences in average power between groups over time. Only the Cr-only group increased total body mass (79.9 ± 13.0→81.1 ± 13.8 kg; p < .01), with no significant changes in lean-tissue or fat mass. These results suggest that Cr alone and in combination with A-AKG improves upper body muscle endurance, and Cr + A-AKG supplementation improves peak power output on repeated Wingate tests.
Nutritional Habits of Flemish Adolescent Sprint Athletes
Authors: Aerenhouts Dirk , Hebbelinck Marcel , Poortmans Jacques R. , Clarys Peter
Published: August 2016

Purpose and Methods:

To investigate dietary habits of Flemish adolescent track and field athletes using a 7-d weighed-food record. Besides adequacy for growth, development, and physical performance, dietary health aspects were considered.

Results:

Twenty-nine girls and 31 boys, with minimum 2 yr of track and field training practice, were recruited. All participants had daily breakfast (girls 22.5% ± 5.5% of total energy intake [TEI]; boys 19.8% ± 7.3%). Fruit in girls and juices and sports drinks in boys were consumed mostly between meals (girls 21.3% ± 8.1% of TEI; boys 24.3% ± 10.1%). Soft drinks contributed considerably to energy intake between meals in both sexes. Protein intake (1.5 ± 0.3 g · kg–1 · d−1 for both sexes) was within the recommended daily intake (RDI) for strength athletes. Mean daily carbohydrate intake in girls was lower than in boys (girls 5.1 ± 1.1 g/kg; boys 6.0 ± 0.9 g/kg), with mono- and disaccharides contributing 26% to TEI in both sexes. Total fat intake was above 30% of TEI in more than half the participants, and only 10 participants had a saturated-fat intake below 10% of TEI. Fiber intake (girls 23.7 ± 7.9 g; boys 29.1 ± 11.2 g) was far below the Belgian RDI. Intake of vitamins and minerals were generally low, despite micronutrient supplementation in 37.5% of the participants.

Conclusion:

Few athletes reached all nutrient RDIs. Unhealthy food habits with regard to refined sugars, fat, and micronutrients were observed. These adolescent sprinters should be encouraged to consume more nonsweetened beverages, fruits, and vegetables.