bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of Medium-Chain Triacylglycerol and Carbohydrate Ingestion on Ultra-Endurance Exercise Performance
Authors: Goedecke Julia H. , Clark Virginia R. , Noakes Timothy D. , Lambert Estelle V.
Published: August 2016

The aims of the study were to determine if medium-chain triacylglycerol (MCT), ingested in combination with carbohydrate (CHO), would alter substrate metabolism and improve simulated competitive ultra-endurance cycling performance. Eight endurance-trained cyclists took part in this randomized, single-blind crossover study. On two separate occasions, subjects cycled for 270 min at 50% of peak power output, interspersed with four 75 kJ sprints at 60 min intervals, followed immediately by a 200 kJ time-trial. One hour prior to the exercise trials, subjects ingested either 75 g of CHO or 32 g of MCT, and then ingested 200 mL of a 10% CHO (wt/vol) solution or a 4.3% MCT + 10% CHO (wt/vol) solution every 20 min during the CHO and MCT trials, respectively. During the constant-load phases of the 270 min exercise trial, VO2, RER, and heart rate were measured at 30 min intervals and gastrointestinal (GI) symptoms were recorded. There was no difference in VO2 or RER between the MCT and CHO trials (P = 0.40). Hourly sprint (P = 0.03 for trial x time interaction) and time-trial times (14:30 ± 0.58 vs. 12:36 ± 1:6, respectively, P < 0.001) were slower in the MCT than the CHO trial. Half the subjects experienced GI symptoms with MCT ingestion. In conclusion, MCTs ingested prior to exercise and co-ingested with CHO during exercise did not alter substrate metabolism and significantly compromised sprint performance during prolonged ultra-endurance cycling exercise.
Altered Vitamin B12 Status in Recreational Endurance Athletes
Authors: Herrmann Markus , Obeid Rima , Scharhag Juergen , Kindermann Wilfried , Herrmann Wolfgang
Published: August 2016

This study aimed to compare the vitamin B12 and folate status of recreational endurance athletes and inactive controls by modern biomarkers. In 72 athletes (38 ± 7 y) and 46 inactive controls (38 ± 9 y) serum levels of vitamin B12, methylmalonic acid (MMA), holotranscobalamin II (holoTC), folate, and homocysteine (Hcy) were measured. Vitamin B12 and folate levels of both groups were comparable, but athletes had higher median (25.−75. percentile) MMA [242 (196 to 324) versus 175 (141 to 266) nmol/L] and holoTC concentrations [67 (52 to 93) versus 55 (45 to 70) pmol/L] than controls. Hcy was slightly lower in athletes [9.2 (7.2 to 12.6) versus 10.8 (8.9 to 12.9) nmol/L]. In controls, we found the following correlations: vitamin B12 and MMA (r = −0.38), vitamin B12 and holoTC (r = 0.51), MMA and holoTC (r = −0.36). In athletes, MMA did not correlate with vitamin B12 and holoTC. Our data suggests an altered vitamin B12 metabolism in recreational athletes that needs further investigation.
A Comparison of Three Methods of Determination of Energy Density of Elite Figure Skaters
Authors: Ziegler Paula J. , Nelson Judith A. , Tay Chloe , Bruemmer Barbara , Drewnowski Adam
Published: August 2016

Dietary energy density (kcal/g) is defined as available dietary energy per unit weight or volume of food. The consumption of energy-dense foods has been associated with increased obesity risk and with excessive weight gain. The objectives of this study were to compare how dietary energy density, calculated using three different methods relates to food choices and nutrient composition of the diets of elite figure skaters. Participants were 159 elite figure skaters attending training camps. Mean age was 18.4 y for boys (n = 79) and 15.9 y for girls (n = 80). Heights and weights were measured to calculate body-mass indices (BMI). Dietary intakes were based on 3-d food records analyzed using the Nutritionist IV program. Mean energy intakes were 2326 kcal/d for boys and 1545 kcal/d for girls. Dietary energy density, based on foods and caloric beverages only, was 1.0 kcal/g. Dietary ED was positively associated with percent energy from fat and negatively with percent energy from sugar. The main sources of dietary energy in this group were baked goods, cereals, regular soda, low-fat milk, fruit juices, bagels and pizza. Percent energy from fast foods was associated with higher dietary energy density, whereas percent energy from dairy products, soft drinks, vegetables, and fruit was associated with lower dietary energy density. These results are consistent with past observations; higher energy density diets were higher in fat. In contrast, there was a negative relationship between sugar content and energy density of the diet.
Effects of Purified Oxygenated Water on Exercise Performance during Acute Hypoxic Exposure
Authors: Wing-Gaia Stacie L. , Subudhi Andrew W. , Askew Eldon W.
Published: August 2016

The purpose of this study was to assess the effects of purified oxygenated water on exercise performance under hypoxic conditions. Nine recreational male cyclists (age = 26.6 ± 5.2 y, weight = 87.6 ± 19.5 kg, VO2peak = 46.5 ± 5.9 mL · kg−1 · min−1) completed two 600 kJ cycling time trials under hypoxic conditions (FIO2 = 13.6% O2, Pbar = 641 mmHg) separated by 2 wk. Trials were completed following 3 d ingestion of 35 mL · kg−1 · d−1 of control (CON) or experimental (EXP) water. Time to completion, heart rate (HR), rate of perceived exertion (RPE), pulse oximetry (SaO2), blood gases (PcO2 and PcCO2), and lactate were measured during the trials. Hydration was assessed with pre- and post-exercise body weight and 24-h urine specific gravity. Performance, hydration, and blood oxygenation were unaffected by EXP water. Results of this study suggest that purified oxygenated water does not improve exercise performance in moderately active males.
Preparation of Former Heavyweight Oarsmen to Compete as Lightweight Rowers Over 16 Weeks: Three Case Studies
Authors: Slater Gary J. , Rice Anthony J. , Jenkins David , Gulbin Jason , Hahn Allan G.
Published: August 2016

To strengthen the depth of lightweight rowing talent, we sought to identify experienced heavyweight rowers who possessed physique traits that predisposed them to excellence as a lightweight. Identified athletes (n = 3) were monitored over 16 wk. Variables measured included performance, anthropometric indices, and selected biochemical and metabolic parameters. All athletes decreased their body mass (range 2.0 to 8.0 kg), with muscle mass accounting for a large proportion of this (31.7 to 84.6%). Two athletes were able to maintain their performance despite reductions in body mass. However, performance was compromised for the athlete who experienced the greatest weight loss. In summary, smaller heavyweight rowers can successfully make the transition into the lightweight category, being nationally competitive in their first season as a lightweight.
The Influence of Biological Maturation on Fat and Carbohydrate Metabolism during Exercise in Males
Authors: Stephens Brooke R. , Cole Andrew S. , Mahon Anthony D.
Published: August 2016

This study examined substrate use during exercise in early-pubertal (EP), mid-pubertal (MP), late-pubertal (LP), and young-adult (YA) males. Fuel use was calculated using the RER and VO2 response during cycling exercise at 30 to 70% of VO2peak. Significant group by intensity interactions were found for lactate, RER, percent CHO, and fat use, in addition to fat and CHO oxidation rates, which suggest a maturation effect on substrate use during exercise. While significance was not achieved at all intensities, post hoc analyses revealed greater fat use, lower CHO use, and lower lactate concentrations in EP and MP compared to LP or YA. No differences were noted between EP and MP or LP and YA at any intensity, suggesting the development of an adult-like metabolic profile occurs between mid- to late-puberty and is complete by the end of puberty.
Gender Differences in the Psychological Response to Weight Reduction in Judoists
Authors: Yoshioka Yoshiko , Umeda Takashi , Nakaji Shigeyuki , Kojima Arata , Tanabe Masaru , Mochida Noriko , Sugawara Kazuo
Published: August 2016

We examined gender-related differences in the psychological response to weight reduction in 43 judoists. Twenty-two males and 8 females who required weight reduction [weight reduction (WR) group] (the average percentages of weight reduction observed for males and females were 3.4% and 4.9%, respectively), and 5 males and 8 females who did not require weight reduction (non-WR group). The POMS scores were measured before and after weight reduction. The TMD (total mood disturbance) score in POMS significantly increased after weight reduction only in WR group males. In the female WR group, the anger and depression scores decreased after weight reduction, and the pre-value of the TMD score in this group was relatively high. The psychological stress may be caused by anxiety engendered by the overall concept of weight reduction before actual weight reduction in females, whereas in males it may be caused by the actual weight reduction.
Blood Lipid Responses after Continuous and Accumulated Aerobic Exercise
Authors: Mestek Michael L. , Garner John C. , Plaisance Eric P. , Taylor James Kyle , Alhassan Sofiya , Grandjean Peter W.
Published: August 2016

The purpose of this study was to compare blood lipid responses to continuous versus accumulated exercise. Nine participants completed the following conditions on separate occasions by treadmill walking/jogging at 70% of VO2max : 1) one 500-kcal session and 2) three 167 kcal sessions. Total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG) concentrations were measured from serum samples obtained 24 h prior to and 24 and 48 h after exercise. All blood lipid responses were analyzed in 2 (condition) × 3 (time) repeated measures ANOVAs. HDL-C increased by 7 mg/dL over baseline at 48 h post-exercise with three accumulated sessions versus 2 mg/dL with continuous exercise (P < 0.05). Triglyceride concentrations were unchanged in both conditions. These findings suggest that three smaller bouts accumulated on the same day may have a modestly greater effect for achieving transient increases in HDL-C compared to a continuous bout of similar caloric expenditure.
Protective Effect of Physical Activity Independent of Obesity on Metabolic Risk Factors
Authors: Li Chia-Lin , Liu Feng-Hsuan , Lin Jen-Der
Published: August 2016

The purpose of this prospective study was to examine the effect of physical activity independent of obesity on metabolic risk factors. A total of 358 participants were recruited from the Department of Health Management of Chang Gung Medical Center. Physical activity was assessed using a 3-d activity record. Body-mass index (BMI) and metabolic risk factors were also assessed. Our findings demonstrate that an effect of obesity that was statistically independent of the levels of physical activity is associated with metabolic risk factors. Moreover, physical activity displayed inverse associations with triglycerides, and fasting plasma glucose and a positive association with HDL cholesterol. Those participants with time spent in moderate activity more than 0.5 h each day had significantly less risk of high fasting glucose. Significantly, these associations were independent of BMI.
Awareness and Use of Caffeine by Athletes Competing at the 2005 Ironman Triathlon World Championships
Authors: Desbrow Ben , Leveritt Michael
Published: August 2016

This study assessed the knowledge, prevalence, and quantity of caffeine use by athletes competing at the 2005 Ironman Triathlon World Championships. Caffeine-related questionnaires were self-administered to 140 (105 male and 35 female, 40.3 ± 10.7 y) athletes representing 16 countries. Fifty of these athletes further consented to immediate post-race blood samples for analysis of plasma caffeine and paraxanthine using high-performance liquid chromatography (HPLC). Seventy-two percent of 70 athletes correctly identified caffeine as being an unrestricted substance in triathlon. The majority of athletes [125 (89%)] were planning on using a caffeinated substance immediately prior to or throughout the race. Cola drinks (78%), caffeinated gels (42%), coffee (usually pre-race) (37%), energy drinks (13%), and NoDoz tablets (9%) were the most popular caffeinated choices. Mean ± standard deviation (and range) post race plasma caffeine and paraxanthine levels were 22.3 ± 20 μmol/L (1.7 to 98.4) and 9.4 ± 6 μmol/L (1.8 to 28.9), respectively. Seven athletes (14%) finished with plasma caffeine levels > 40 μmol/L. Plasma values from elite athletes did not differ from age group competitors. Despite the prevalence of its consumption and the training experience of this athletic group, over one quarter of athletes remained either confused or uninformed about caffeine’s legality. Levels of plasma caffeine taken immediately post race indicated that athletes typically finish with quantities of caffeine that have been shown to improve endurance performance (i.e., ~ 20 μmol/L or a dose of > 3 mg/kg body weight).
Hydration during Exercise in Warm, Humid Conditions: Effect of a Caffeinated Sports Drink
Authors: Millard-Stafford Mindy L. , Cureton Kirk J. , Wingo Jonathan E. , Trilk Jennifer , Warren Gordon L. , Buyckx Maxime
Published: August 2016

Caffeine is regarded as a diuretic despite evidence that hydration is not impaired with habitual ingestion. The purpose of this study was to determine whether a caffeinated sports drink impairs fluid delivery and hydration during exercise in warm, humid conditions (28.5 °C, 60% relative humidity). Sixteen cyclists completed 3 trials: placebo (P), carbohydrate-electrolyte (CE), and caffeinated (195 mg/L) sports drink (CAF+CE). Subjects cycled for 120 min at 60–75%VO2max followed by 15 min of maximal-effort cycling. Heart rate and rectal temperature were similar until the final 15 min, when these responses and exercise intensity were higher with CAF+CE than with CE and P. Sweat rate, urine output, plasma-volume losses, serum electrolytes, and blood deuterium-oxide accumulation were not different. Serum osmolality was higher with CAF+CE vs. P but not CE. The authors conclude that CAF+CE appears as rapidly in blood as CE and maintains hydration and sustains cardiovascular and thermoregulatory function as well as CE during exercise in a warm, humid environment.
Estimated Energy Expenditure and Physical Activity Patterns of Adolescent Distance Runners
Authors: Eisenmann Joey C. , Wickel Eric E.
Published: August 2016

The purpose of this study was to examine the estimated total energy expenditure (TEE) and physical activity patterns of adolescent distance runners. Twenty-eight (20 male, 8 female) adolescent distance runners self-reported their daily physical activity with the Bouchard 3-d diary. Mean values for TEE, 57.4 ± 11.6 and 51.0 ± 9.8 kcal·kg−1·d−1, and activity energy expenditure (AEE), 26.7 ± 10.4 and 21.0 ± 8.8 kcal·kg−1·d−1, when expressed per kilogram body mass were not significantly different between males and females, respectively (P = 0.18). When expressed in absolute terms, TEE, 3609 ± 927 and 2467 ± 426 kcal/d, and AEE, 1688 ± 746 and 977 ± 269 kcal/d, were significantly higher in males than in females, respectively. The results document the energy expenditure and self-reported physical activity of adolescent distance runners and might be used to address recommendations for adequate dietary energy requirements in this group, which in turn is important for energy balance in the context of normal growth, health, and physical performance.
Effect of Preexercise Ingestion of Modified Cornstarch on Substrate Oxidation during Endurance Exercise
Authors: Johannsen Neil M. , Sharp Rick L.
Published: August 2016

The purpose of this study was to investigate differences in substrate oxidation between dextrose (DEX) and unmodified (UAMS) and acid/alcohol-modified (MAMS) cornstarches. Seven endurance-trained men (VO2peak = 59.1 ± 5.4 mL·kg−1·min−1) participated in 2 h of exercise (66.4% ± 3.3% VO2peak) 30 min after ingesting 1 g/kg body weight of the experimental carbohydrate or placebo (PLA). Plasma glucose and insulin were elevated after DEX (P < 0.05) compared with UAMS, MAMS, and PLA. Although MAMS and DEX raised carbohydrate oxidation rate through 90 min of exercise, only MAMS persisted throughout 120 min (P < 0.05 compared with all trials). Exogenous-carbohydrate oxidation rate was higher in DEX than in MAMS and UAMS until 90 min of exercise. Acid/alcohol modification resulted in augmented carbohydrate oxidation with a small, sustained increase in exogenous-carbohydrate oxidation rate. MAMS appears to be metabolizable and available for oxidation during exercise.
Voluntary Dehydration in Runners Despite Favorable Conditions for Fluid Intake
Authors: Passe Dennis , Horn Mary , Stofan John , Horswill Craig , Murray Robert
Published: August 2016

This study investigated the relationship between runners’ perceptions of fluid needs and drinking behavior under conditions of compensable heat stress (ambient temperature = 20.5 ± 0.7 °C, 68.9 °F; relative humidity = 76.6%). Eighteen experienced runners (15 men, 40.5 ± 2.5 y, and 3 women, 42 ± 2.3 y) were given ad libitum access to a sports drink (6% carbohydrate-electrolyte solution) at Miles 2, 4, 6, and 8. After the run (75.5 ± 8.0 min), subjects completed questionnaires that required them to estimate their individual fluid intake and sweat loss. Dehydration averaged 1.9% ± 0.8% of initial body weight (a mean sweat loss of 21.6 ± 5.1 mL·kg−1·h−1). Subjects replaced only 30.5% ± 18.1% of sweat loss and underestimated their sweat loss by 42.5% ± 36.6% (P ≤ 0.001). Subjects’ self-estimations of fluid intake (5.2 ± 3.2 mL·kg−1·h−1) were not significantly different from actual fluid intake (6.1 ± 3.4 mL·kg−1·h−1) and were significantly correlated (r = 0.63, P = 0.005). The data indicate that even under favorable conditions, experienced runners voluntarily dehydrate (P ≤ 0.001), possibly because they are unable to accurately estimate sweat loss and consequently cannot subjectively judge how much fluid to ingest to prevent dehydration. This conclusion suggests that runners should not depend on self-assessment to maintain adequate hydration, underscores the need for runners to enhance their ability to self-assess sweat losses, and suggests that a predetermined regimen of fluid ingestion might be necessary if they wish to maintain more optimal hydration.
Well-Trained Endurance Athletes’ Knowledge, Insight, and Experience of Caffeine Use
Authors: Desbrow Ben , Leveritt Michael
Published: August 2016

This descriptive cross-sectional study assessed the perceptions, knowledge, and experiences of caffeine use by athletes competing at the 2005 Ironman Triathlon World Championships. Questionnaires were distributed to 140 athletes (105 men and 35 women, 40.3 ± 10.7 y old) representing 16 countries during prerace registration. A large proportion (73%) of these endurance athletes believe that caffeine is ergogenic to their endurance performance, and 84% believe it improves their concentration. The most commonly reported positive caffeine experiences related to in-competition use of cola drinks (65%) and caffeinated gels (24%). The athletes’ ability to accurately quantify the caffeine content of common food items was limited. The most popular sources of caffeine information were self-experimentation (16%), fellow athletes (15%), magazines (13%), and journal articles (12%). Over half the athletes (53%) could not identify an amount of caffeine required to improve their triathlon performance. Mean (± standard deviation) suggested doses were 3.8 (± 3) mg/kg body weight. Few side effects associated with taking caffeine during exercise were reported.
Nutritional Adequacy of Different Menu Settings in Elite Spanish Adolescent Soccer Players
Authors: Garrido Guadalupe , Webster Anthony L , Chamorro Manuel
Published: August 2016

The article describes a study that evaluated the adequacy of 2 different menu settings in a group of elite adolescent Spanish soccer players. Five-day food intake was assessed on 2 occasions, while athletes were consuming a flexible “buffet-style” diet (B; n = 33) and a fixed “menu-style” diet (M; n = 29). For all principal meals of the day food weighing was performed, and snacks were recorded by self-report. M provided significantly higher total energy and carbohydrate intakes than B. Breakfast and snacks both provided more energy in M. Calories obtained from fat were excessive in both settings. Calcium and vitamin D were below recommendations in B but not in M. Fiber, magnesium, folate, vitamin A, and vitamin E intake fell below recommended values in both settings. M provided significantly greater quantities of magnesium and vitamins D and E. Both feeding options were far from optimal in satisfying current scientifically based recommendations for active adolescents.
The Effects of Nutritional Supplementation Throughout an Endurance Run on Leucine Kinetics during Recovery
Authors: Miller Sharon L. , Gaine P. Courtney , Maresh Carl M. , Armstrong Lawrence E. , Ebbeling Cara B. , Lamont Linda S. , Rodriguez Nancy R.
Published: August 2016

This study determined the effect of nutritional supplementation throughout endurance exercise on whole-body leucine kinetics (leucine rate of appearance [Ra], oxidation [Ox], and nonoxidative leucine disposal [NOLD]) during recovery. Five trained men underwent a 2-h run at 65% VO2max, during which a carbohydrate (CHO), mixed protein-carbohydrate (milk), or placebo (PLA) drink was consumed. Leucine kinetics were assessed during recovery using a primed, continuous infusion of 1-13C leucine. Leucine Ra and NOLD were lower for milk than for PLA. Ox was higher after milk-supplemented exercise than after CHO or PLA. Although consuming milk during the run affected whole-body leucine kinetics, the benefits of such a practice for athletes remain unclear. Additional studies are needed to determine whether protein supplementation during exercise can optimize protein utilization during recovery.
Sweat Mineral-Element Responses during 7 h of Exercise-Heat Stress
Authors: Montain Scott J. , Cheuvront Samuel N. , Lukaski Henry C.
Published: August 2016

Context:

Uncertainty exists regarding the effect of sustained sweating on sweat mineral-element composition.

Purpose:

To determine the effect of multiple hours of exercise-heat stress on sweat mineral concentrations.

Methods:

Seven heat-acclimated subjects (6 males, 1 female) completed 5 × 60 min of treadmill exercise (1.56 m/s, 2% grade) with 20 min rest between exercise periods in 2 weather conditions (27 °C, 40% relative humidity, 1 m/s and 35 °C, 30%, 1 m/s). Sweat was collected from a sweat-collection pouch attached to the upper back during exercise bouts 1, 3, and 5. Mineral elements were determined by using inductively coupled plasma-emission spectrography.

Results:

At 27 °C, sweat sodium (863 [563] µg/mL; mean [SD]), potassium (222 [48] µg/mL), calcium (16 [7]) µg/mL), magnesium (1265 [566] ng/mL), and copper (80 [56] ng/mL) remained similar to baseline over 7 h of exercise-heat stress, whereas sweat zinc declined 42–45% after the initial hour of exercise-heat stress (Ex1 = 655 [362], Ex3 = 382 [168], Ex5 = 355 [288] µg/mL, P < 0.05). Similar outcomes were observed for sweat zinc at 35 °C when sweat rates were higher. Sweat rate had no effect on sweat trace-element composition.

Conclusions:

Sweat sodium, potassium, and calcium losses during multiple hours of sustained sweating can be predicted from initial sweat composition. Estimates of sweat zinc losses, however, will be overestimated if sweat zinc conservation is not accounted for in sweat zinc-loss estimates.
Protein and Protein Hydrolysates in Sports Nutrition
Authors: van Loon Luc J.C. , Kies Arie K. , Saris Wim H.M.
Published: August 2016

With the increasing knowledge about the role of nutrition in increasing exercise performance, it has become clear over the last 2 decades that amino acids, protein, and protein hydrolysates can play an important role. Most of the attention has been focused on their effects at a muscular level. As these nutrients are ingested, however, it also means that gastrointestinal digestibility and absorption can modulate their effcacy significantly. Therefore, discussing the role of amino acids, protein, and protein hydrolysates in sports nutrition entails holding a discussion on all levels of the metabolic route. On May 28–29, 2007, a small group of researchers active in the field of exercise science and protein metabolism presented an overview of the different aspects of the application of protein and protein hydrolysates in sports nutrition. In addition, they were asked to share their opinions on the future progress in their fields of research. In this overview, an introduction to the workshop and a short summary of its outcome is provided.
Effects of Sodium Bicarbonate, Caffeine, and Their Combination on Repeated 200-m Freestyle Performance
Authors: Pruscino Cathryn L. , Ross Megan L.R. , Gregory John R. , Savage Bernard , Flanagan Troy R.
Published: August 2016

The purpose of this study was to investigate the effects of sodium bicarbonate (NaHCO3), caffeine, and their combination on repeated 200-m freestyle performance. Six elite male freestyle swimmers ingested NaHCO3 (0.3 g/kg; B), caffeine (6.2 ± 0.3 mg/kg; C), a combination of both (B+C), and placebo (P) on 4 separate occasions before completing 2 maximal 200-m freestyle time trials (TT1 and TT2) separated by 30 min. No significant differences (p = .06) were observed for performance in TT1 (B 2:03.01 ± 0:03.68 min, C 2:02.42 ± 0:03.17 min, B+C 2:01.69 ± 0:03.19 min, P 2:03.77 ± 0:03.21 min) or TT2 (B 2:02.62 ± 0:04.16 min, C 2:03.90 ± 0:03.58 min, B+C 2:01.70 ± 0:02.84 min, P 2:04.22 ± 0:03.75 min). The drop-off in performance time from TT1 to TT2, however, was significantly greater when C was ingested than with B (−1.5%, p = .002) or B+C (–1.2%, p = .024). This is likely because of the lower blood pH and slower recovery of blood HCO3 post-TT1 after C ingestion. These findings suggest that the ergogenic benefit of taking C alone for repeated 200-m swimming performance appears limited. When combined with NaHCO3, however, its negative impact on repeated maximal exercise performance is reversed.
Should We Be Concerned about the Vitamin D Status of Athletes?
Authors: Willis Kentz S. , Peterson Nikki J. , Larson-Meyer D. Enette
Published: August 2016

A surprisingly high prevalence of vitamin D insufficiency and deficiency has recently been reported worldwide. Although very little is known about vitamin D status among athletes, a few studies suggest that poor vitamin D status is also a problem in athletic populations. It is well recognized that vitamin D is necessary for optimal bone health, but emerging evidence is finding that vitamin D deficiency increases the risk of autoimmune diseases and nonskeletal chronic diseases and can also have a profound effect on human immunity, inflammation, and muscle function (in the elderly). Thus, it is likely that compromised vitamin D status can affect an athlete’s overall health and ability to train (i.e., by affecting bone health, innate immunity, and exercise-related immunity and inflammation). Although further research in this area is needed, it is important that sports nutritionists assess vitamin D (as well as calcium) intake and make appropriate recommendations that will help athletes achieve adequate vitamin D status: serum 25(OH)D of at least 75 or 80 nmol/L. These recommendations can include regular safe sun exposure (twice a week between the hours of 10 a.m. and 3 p.m. on the arms and legs for 5–30 min, depending on season, latitude, and skin pigmentation) or dietary supplementation with 1,000–2,000 IU vitamin D3 per day. Although this is significantly higher than what is currently considered the adequate intake, recent research demonstrates these levels to be safe and possibly necessary to maintain adequate 25(OH)D concentrations.
The Influence of Supplementation with Artichoke (Cynara scolymus L.) Extract on Selected Redox Parameters in Rowers
Authors: Skarpañska-Stejnborn Anna , Pilaczynska-Szczesniak Lucia , Basta Piotr , Deskur-Smielecka Ewa , Horoszkiewicz-Hassan Magorzata
Published: August 2016

High-intensity physical exercise decreases intracellular antioxidant potential. An enhanced antioxidant defense system is desirable in people subjected to exhaustive exercise. The aim of this study was to investigate the influence of supplementation with artichoke-leaf extract on parameters describing balance between oxidants and antioxidants in competitive rowers. This double-blinded study was carried out in 22 members of the Polish rowing team who were randomly assigned to a supplemented group (n = 12), receiving 1 gelatin capsule containing 400 mg of artichoke-leaf extract 3 times a day for 5 wk, or a placebo group (n = 10). At the beginning and end of the study participants performed a 2,000-m maximal test on a rowing ergometer. Before each exercise test, 1 min after the test completion, and after a 24-hr restitution period blood samples were taken from antecubital vein. The following redox parameters were assessed in red blood cells: superoxide dismutase activity, glutathione peroxidase activity, glutathione reductase activity, reduced glutathione levels, and thiobarbituric-acid-reactive-substances concentrations. Creatine kinase activity and total antioxidant capacity (TAC) were measured in plasma samples, lactate levels were determined in capillary blood samples, and serum lipid profiles were assessed. During restitution, plasma TAC was significantly higher (p < .05) in the supplemented group than in the placebo group. Serum total cholesterol levels at the end of the study were significantly (p < .05) lower in the supplemented group than in the placebo group. In conclusion, consuming artichoke-leaf extract, a natural vegetable preparation of high antioxidant potential, resulted in higher plasma TAC than placebo but did not limit oxidative damage to erythrocytes in competitive rowers subjected to strenuous training.
Ergogenic Effects of Low Doses of Caffeine on Cycling Performance
Authors: Jenkins Nathan T. , Trilk Jennifer L. , Singhal Arpit , O’Connor Patrick J. , Cureton Kirk J.
Published: August 2016

The purpose of this experiment was to learn whether low doses of caffeine have ergogenic, perceptual, and metabolic effects during cycling. To determine the effects of 1, 2, and 3 mg/kg caffeine on cycling performance, differentiated ratings of perceived exertion (D-RPE), quadriceps pain intensity, and metabolic responses to cycling exercise, 13 cyclists exercised on a stationary ergometer for 15 min at 80% VO2peak, then, after 4 min of active recovery, completed a 15-min performance ride 60 min after ingesting caffeine or placebo. Work done (kJ/kg) during the performance ride was used as a measure of performance. D-RPE, pain ratings, and expired-gas data were obtained every 3 min, and blood lactate concentrations were obtained at 15 and 30 min. Compared with placebo, caffeine doses of 2 and 3 mg/kg increased performance by 4% (95% CI: 1.0–6.8%, p = .02) and 3% (95% CI: –0.4% to 6.8%, p = .077), respectively. These effects were ergogenic, on average, but varied considerably in magnitude among individual cyclists. There were no effects of caffeine on D-RPE or pain throughout the cycling task. Selected metabolic variables were affected by caffeine, consistent with its known actions. The authors conclude that caffeine preparations of 2 and 3 mg/kg enhanced performance, but future work should aim to explain the considerable interindividual variability of the drug’s ergogenic properties.
Effect of Creatine Supplementation and Resistance-Exercise Training on Muscle Insulin-Like Growth Factor in Young Adults
Authors: Burke Darren G. , Candow Darren G. , Chilibeck Philip D. , MacNeil Lauren G. , Roy Brian D. , Tarnopolsky Mark A. , Ziegenfuss Tim
Published: August 2016

The purpose of this study was to compare changes in muscle insulin-like growth factor-I (IGF-I) content resulting from resistance-exercise training (RET) and creatine supplementation (CR). Male (n = 24) and female (n = 18) participants with minimal resistance-exercise-training experience (≥1 year) who were participating in at least 30 min of structured physical activity (i.e., walking, jogging, cycling) 3–5 ×/wk volunteered for the study. Participants were randomly assigned in blocks (gender) to supplement with creatine (CR: 0.25 g/kg lean-tissue mass for 7 days; 0.06 g/kg lean-tissue mass for 49 days; n = 22, 12 males, 10 female) or isocaloric placebo (PL: n = 20, 12 male, 8 female) and engage in a whole-body RET program for 8 wk. Eighteen participants were classified as vegetarian (lacto-ovo or vegan; CR: 5 male, 5 female; PL: 3 male, 5 female). Muscle biopsies (vastus lateralis) were taken before and after the intervention and analyzed for IGF-I using standard immunohistochemical procedures. Stained muscle cross-sections were examined microscopically and IGF-I content quantified using image-analysis software. Results showed that RET increased intramuscular IGF-I content by 67%, with greater accumulation from CR (+78%) than PL (+54%; p = .06). There were no differences in IGF-I between vegetarians and nonvegetarians. These findings indicate that creatine supplementation during resistance-exercise training increases intramuscular IGF-I concentration in healthy men and women, independent of habitual dietary routine.
Chicken Breast Attenuates High-Intensity-Exercise-Induced Decrease in Rat Sarcoplasmic Reticulum Ca2+ Handling
Authors: Mishima Takaaki , Yamada Takashi , Sakamoto Makoto , Sugiyama Minako , Matsunaga Satoshi , Maemura Hirohiko , Shimizu Muneshige , Takahata Yoshihisa , Morimatsu Fumiki , Wada Masanobu
Published: August 2016

This study was conducted to determine whether dietary chicken-breast extract (CBEX), a rich source of histidine-containing dipeptides, could modify exerciseinduced changes in sarcoplasmic reticulum (SR) function. After 5 weeks of dietary CBEX, SR Ca2+-handling ability was examined in the vastus lateralis muscles of rats subjected to high-intensity running for 2.5 min. Dietary CBEX caused an approximately 15% and 45% increase (p < .01) in muscle carnosine and anserine concentrations, respectively. In resting muscles, depressions in SR Ca2+–ATPase activity were evoked by dietary CBEX without concomitant changes in SR Ca2+ uptake and release rates. The data confirm that high-intensity exercise depresses SR Ca2+ handling. In spite of the same run time, SR Ca2+ handling was reduced to a lesser degree in muscles of CBEX-containing-chow-fed rats than in standard-chow-fed rats (p < .05). These results suggest that dietary CBEX might attenuate deteriorations in SR Ca2+-handling ability that occur with high-intensity exercise.
Effects of an Amino Acid–Carbohydrate Drink on Exercise Performance after Consecutive-Day Exercise Bouts
Authors: Skillen Rebecca A. , Testa Massimo , Applegate Elizabeth A. , Heiden Eric A. , Fascetti Andrea J. , Casazza Gretchen A.
Published: August 2016

This study examined the effect of amino acids in a carbohydrate beverage on cycling performance. Twelve male athletes (28.5 pp2.1 yr) cycled at 75% VO2peak for 90 min followed by a ride to exhaustion at 85% VO2peak, before (T1) and on 2 consecutive days (T2 and T3) after 2 weeks of supplementation with 3.6% carbohydrate plus 1% amino acids (AA) or 4.6% carbohydrate-only (CHO) isocaloric beverages. Muscle damage was assessed by plasma creatine kinase (CK), and muscle fatigue by changes in vertical jump pre- to postexercise. Muscle soreness, overall fatigue, and changes in mood state were assessed using questionnaires. Plasma CK was lower for AA in T3 (214.0 ss13.5 vs. 485.9 11191.4 U/L immediately post, 213.9 ÷ 13.1 vs. 492.0 ÷ 199.4 U/L 5 hr post, and 194.9 ÷ 17.9 vs. 405.9 ÷ 166.6 U/L 24 hr postexercise in AA and CHO, respectively). Time to exhaustion decreased from T2 to T3 only in CHO (10.9 ÷ 2.5 to 12.6 ÷ 3.2 vs. 13.8 ÷ 2.8 to 7.8 ÷ 1.5 min in AA and CHO, respectively). Vertical-jump change from pre- to postexercise was greater in T3 for the CHO treatment. Total fatigue score and mood disturbance decreased significantly only with AA in T3. The addition of AA to a carbohydrate beverage after consecutive-day exercise bouts reduced muscle damage as indicated by CK levels, decreased fatigue, and maintained exercise performance compared with consuming carbohydrate alone.
Effect of Caffeine on Quadriceps Muscle Pain during Acute Cycling Exercise in Low versus High Caffeine Consumers
Authors: Gliottoni Rachael C. , Meyers John R. , Arngrímsson Sigurbjörn Á. , Broglio Steven P. , Motl Robert W.
Published: August 2016

This experiment examined the effect of a moderate dose of caffeine on quadriceps muscle pain during a bout of high-intensity cycling in low- versus high-caffeine-consuming males. College-age men who were low (≤100 mg/day; n = 12) or high (≥400 mg/day; n = 13) habitual caffeine consumers ingested caffeine (5 mg/kg body weight) or a placebo in a counterbalanced order and 1 hr later completed 30 min of cycle ergometry at 75–77% of peak oxygen consumption. Perceptions of quadriceps muscle pain, as well as oxygen consumption, heart rate, and work rate, were recorded during both bouts of exercise. Caffeine ingestion resulted in a statistically significant and moderate reduction in quadriceps muscle-pain-intensity ratings during the 30-min bout of high-intensity cycle ergometry compared with placebo ingestion in both low (d = −0.42) and high (d = −0.55) caffeine consumers. The results suggest that caffeine ingestion is associated with a moderate hypoalgesic effect during high-intensity cycling in college-age men who are low or high habitual caffeine consumers, but future work should consider better defining and differentiating pain and effort when examining the effects of caffeine during acute exercise.
Effect of Preexercise Glycemic-Index Meal on Running When CHO-Electrolyte Solution Is Consumed during Exercise
Authors: Wong Stephen H.S , Chan Oi Won , Chen Ya Jun , Hu Heng Long , Lam Ching Wan , Chung Pak Kwong
Published: August 2016

Purpose:

This study examined the effect of consuming carbohydrate- (CHO) electrolyte solution on running performance after different-glycemic-index (GI) meals.

Methods:

Nine men completed 3 trials in a randomized counterbalanced order, with trials separated by at least 7 days. Two hours before the run after an overnight fast, each participant consumed a high-GI (GI = 83) or low-GI (GI = 36) CHO meal or low-energy sugar-free Jell-O (GI = 0, control). The 2 isocaloric GI meals provided 1.5 g available CHO/kg body mass. During each trial, 2 ml/kg body mass of a 6.6% CHO-electrolyte solution was provided immediately before exercise and every 2.5 km after the start of running. Each trial consisted of a 21-km performance run on a level treadmill. The participants were required to run at 70% VO2max during the first 5 km of the run. They then completed the remaining 16 km as fast as possible.

Results:

There was no difference in the time to complete the 21-km run (high-GI vs. low-GI vs. control: 91.1 ± 2.0 vs. 91.8 ± 2.2 vs. 92.9 ± 2.0 min, n.s.). There were no differences in total CHO and fat oxidation throughout the trials, despite differences in preexercise blood glucose, serum insulin, and serum free-fatty-acid concentrations.

Conclusion:

When a CHO-electrolyte solution is consumed during a 21-km run, the GI of the preexercise CHO meal makes no difference in running performance.
Effect of Ingesting a Honey-Sweetened Beverage on Soccer Performance and Exercise-Induced Cytokine Response
Authors: Abbey Elizabeth L. , Rankin Janet Walberg
Published: August 2016

Purpose:

This study compared the effect of a honey-sweetened beverage with those of a commercial sports drink and a placebo on performance and inflammatory response to a 90-min soccer simulation.

Methods:

Ten experienced male soccer players randomly performed 3 trials (honey [H], sports drink [S], and placebo [P]), consuming the beverage before and during halftime for a total of 1.0 g/kg carbohydrate for H and S. Performance measures included 5 sets (T1–T5) of a high-intensity run and agility and ball-shooting tests followed by a final progressive shuttle-run (PSR) test to exhaustion. Blood samples were drawn pretest, posttest (B2), and 1 hr posttest (B3) for markers of inflammation, oxygen radical absorbance capacity (ORAC), and hormone response.

Results:

T2–T5 were significantly slower than T1 (p < .05), and a decrease in PSR time was observed from baseline (–22.9%) for all treatments. No significant effect of the interventions was observed for any performance measures. Plasma IL-1ra levels increased posttest for all treatments (65.5% S, 63.9% P, and 25.8% H), but H was significantly less than S at posttest and P at B3. Other cytokines and ORAC increased at B2 (548% IL-6, 514% IL-10, 15% ORAC) with no difference by treatment.

Conclusion:

Acute ingestion of honey and a carbohydrate sports drink before and during a soccer-simulation test did not improve performance, although honey attenuated a rise in IL-1ra. Ingestion of carbohydrate and/or antioxidant-containing beverages at frequencies typical of a regulation match may not be beneficial for trained soccer players.
L-Lactic Acid’s Improvement of Swimming Endurance in Mice
Authors: Zhang Guihua , Shirai Nobuya , Suzuki Hiramitsu
Published: August 2016

The aim of this study was to investigate the effect of L-lactic acid on swimming endurance of mice. Mice (n = 50) were injected intraperitoneally with saline, then with L-lactic acid (either 25 mg/kg or 50 mg/kg body weight), then after 2 days with the same doses of glucose, and after another 2 days again with L-lactic acid at the same doses. Swimming times to exhaustion were determined at 30 min after each injection, in a tank filled with 25 cm of water maintained at 23 °C. After another week, mice were given either saline, L-lactic acid, or glucose (25 or 50 mg/kg) dissolved in saline and sacrificed after 30 min for biochemical analyses. The ratios of swimming times of L-lactic acid or glucose injections to saline injection were calculated as an index for endurance changes. Swimmingtime ratios for mice injected with L-lactic acid were significantly higher at either dose than for those injected with the corresponding doses of glucose (p < .05). The ratio of swimming time was greater in those given a dose of 50 mg/kg than in those given 25 mg/kg for mice in the L-lactic acid groups (p < .05) but not in the groups given glucose. There were no marked differences in biochemical parameters of plasma and muscle lactate, muscle and liver glycogen, or plasma glucose and nonesterified fatty acid between the L-lactic acid, glucose, and saline injection groups. These results suggest that L-lactic acid can enhance swimming endurance of mice and that this action is dose dependent.
12 Weeks of Combined Exercise Is Better Than Aerobic Exercise for Increasing Growth Hormone in Middle-Aged Women
Authors: Seo Dong-Il , Jun Tae-Won , Park Kae-Soon , Chang Hyukki , So Wi-Young , Song Wook
Published: August 2016

Background:

The purpose of this study was to examine the effects of combined exercise training on growth hormone (GH), insulin-like growth factor-1 (IGF-1), and metabolic-syndrome factors and determine whether the changes in GH and/or IGF-1 induced by exercise correlate to the metabolic-syndrome factors in healthy middle-aged women (50–65 years of age).

Methods:

The participants were randomly assigned into an aerobic-exercise training (walking + aerobics) group (AEG; n = 7), a combined-exercise training (walking + resistance training) group (CEG; n = 8), or a control group (CG; n = 7). Exercise sessions were performed 3 times per wk for 12 wk. The aerobic-exercise training consisted of walking and aerobics at 60–80% of heart-rate reserve, and the combined-exercise training consisted of walking and resistance exercise at 50–70% of 1-repetition maximum.

Results:

GH, percentage body fat, fasting glucose, systolic blood pressure, and waist circumference were significantly improved in CEG (p < .05). However, GH induced by exercise training showed no correlation with metabolic-syndrome factors. IGF-1 was not significantly increased in either AEG or CEG compared with CG.

Conclusion:

These results indicate that the combined-exercise training produced more enhancement of GH, body composition, and metabolic-syndrome factors than did aerobic-exercise training.
The Dietary Flavonoid Quercetin Increases VO2max and Endurance Capacity
Authors: Davis J. Mark , Carlstedt Catherine J. , Chen Stephen , Carmichael Martin D. , Murphy E. Angela
Published: August 2016

Quercetin, a natural polyphenolic flavonoid substance present in a variety of food plants, has been shown in vitro and in animal studies to have widespread health and performance benefits resulting from a combination of biological properties, including antioxidant and anti-inflammatory activity, as well as the ability to increase mitochondrial biogenesis. Little is known about these effects in humans, however, especially with respect to exercise performance. The authors determined whether quercetin ingestion would enhance maximal aerobic capacity and delay fatigue during prolonged exercise in healthy but untrained participants. Twelve volunteers were randomly assigned to 1 of 2 treatments: (a) 500 mg of quercetin twice daily dissolved in vitamin-enriched Tang or (b) a nondistinguishable placebo (Tang). Baseline VO2max and bike-ride times to fatigue were established. Treatments were administered for a period of 7 days using a randomized, double-blind, placebo-controlled, crossover study design. After treatment both VO2max and ride time to fatigue were determined. Seven days of quercetin feedings were associated with a modest increase in VO2max (3.9% vs. placebo; p < .05) along with a substantial (13.2%) increase in ride time to fatigue (p < .05). These data suggest that as little as 7 days of quercetin supplementation can increase endurance without exercise training in untrained participants. These benefits of quercetin may have important implications for enhancement of athletic and military performance. This apparent increase in fitness without exercise training may have implications beyond that of performance enhancement to health promotion and disease prevention.
Adaptation of Insulin-Resistance Indicators to a Repeated Bout of Eccentric Exercise in Human Skeletal Muscle
Authors: Green Michael S. , Doyle J. Andrew , Ingalls Christopher P. , Benardot Dan , Rupp Jeffrey C. , Corona Benjamin T.
Published: August 2016

This study determined whether disrupted glucose and insulin responses to an oral glucose-tolerance test (OGTT) induced by eccentric exercise were attenuated after a repeated bout. Female participants (n = 10, age 24.7 ± 3.0 yr, body mass 64.9 ± 7.4 kg, height 1.67 ± 0.02 m, body fat 29% ± 2%) performed 2 bouts of downhill running (DTR 1 and DTR 2) separated by 14 d. OGTTs were administered at baseline and 48 hr after DTR 1 and DTR 2. Maximum voluntary isometric quadriceps torque (MVC), subjective soreness (100-mm visual analog scale), and serum creatine kinase (CK) were assessed pre-, post-, and 48 hr post-DTR 1 and DTR 2. Insulin and glucose area under the curve (38% ± 8% and 21% ± 5% increase, respectively) and peak insulin (44.1 ± 5.1 vs. 31.6 ± 4.0 μU/ml) and glucose (6.5 ± 0.4 vs. 5.5 ± 0.4 mmol/L) were elevated after DTR 1, with no increase above baseline 48 hr after DTR 2. MVC remained reduced by 9% ± 3% 48 hr after DTR 1, recovering back to baseline 48 hr after DTR 2. Soreness was elevated to a greater degree 48 hr after DTR 1 (48 ± 6 vs. 13 ± 3 mm), with a tendency for greater CK responses 48 hr after DTR 1 (813 ± 365 vs. 163 ± 43 U/L, p = .08). A novel bout of eccentric exercise confers protective effects, with subsequent bouts failing to elicit disruptions in glucose and insulin homeostasis.