bluuebunny/crossref_metadata_2025 huggingface dataset:
A Review of Issues of Dietary Protein Intake in Humans
Authors: Bilsborough Shane , Mann Neil
Published: August 2016

Considerable debate has taken place over the safety and validity of increased protein intakes for both weight control and muscle synthesis. The advice to consume diets high in protein by some health professionals, media and popular diet books is given despite a lack of scientific data on the safety of increasing protein consumption. The key issues are the rate at which the gastrointestinal tract can absorb amino acids from dietary proteins (1.3 to 10 g/h) and the liver’s capacity to deaminate proteins and produce urea for excretion of excess nitrogen. The accepted level of protein requirement of 0.8g · kg−1 · d−1 is based on structural requirements and ignores the use of protein for energy metabolism. High protein diets on the other hand advocate excessive levels of protein intake on the order of 200 to 400 g/d, which can equate to levels of approximately 5 g · kg−1 · d−1, which may exceed the liver’s capacity to convert excess nitrogen to urea. Dangers of excessive protein, defined as when protein constitutes > 35% of total energy intake, include hyperaminoacidemia, hyperammonemia, hyperinsulinemia nausea, diarrhea, and even death (the “rabbit starvation syndrome”). The three different measures of defining protein intake, which should be viewed together are: absolute intake (g/d), intake related to body weight (g · kg−1 · d−1) and intake as a fraction of total energy (percent energy). A suggested maximum protein intake based on bodily needs, weight control evidence, and avoiding protein toxicity would be approximately of 25% of energy requirements at approximately 2 to 2.5 g · kg−1 · d−1, corresponding to 176 g protein per day for an 80 kg individual on a 12,000kJ/d diet. This is well below the theoretical maximum safe intake range for an 80 kg person (285 to 365 g/d).
The Effect of High Carbohydrate Meals with Different Glycemic Indices on Recovery of Performance during Prolonged Intermittent High-Intensity Shuttle Running
Authors: Erith Samuel , Williams Clyde , Stevenson Emma , Chamberlain Siobhan , Crews Pippa , Rushbury Ian
Published: August 2016

This study examined the effect of high carbohydrate meals with different glycemic indices (GI) on recovery of performance during prolonged intermittent high-intensity shuttle running. Seven male semi-professional soccer players (age 23 ± 2 y, body mass [BM] 73.7 ± 9.0 kg and maximal oxygen uptake 58 ± 1.0 mL · kg−1 · min−1) participated in two trials in a randomized cross-over design. On day 1, the subjects performed 90 min of an intermittent high-intensity shuttle running protocol [Loughborough Intermittent Shuttle Test (LIST)]. They then consumed a mixed high carbohydrate recovery diet (8 g/kg BM) consisting of either high (HGI) (GI: 70) or low (LGI) (GI: 35) GI foods. Twenty-two hours later (day 2) the subjects completed 75 min of the LIST (part A) followed by alternate sprinting and jogging to fatigue (part B). No differences were found between trials in time to fatigue (HGI 25.3 ± 4.0 min vs. LGI 22.9 ± 5.6 min, P = 0.649). Similarly, no differences were found between trials for sprint performance and distance covered during part B of the LIST. In conclusion, the GI of the diet during the 22 h recovery did not affect sprint and endurance performance the following day.
Effect of Exercise Intensity on Active and Passive Glucose Absorption
Authors: Lang James A. , Gisolfi Carl V. , Lambert G. Patrick
Published: August 2016

The purpose of this study was to determine the effects of exercise intensity on active and passive intestinal glucose absorption. Eight trained runners (age = 23 ± 2 y; VO2max = 62.1 ± 5.8 mL · kg−1 · min−1) performed a 1 h resting experiment and three 1 h treadmill experiments at 30, 50, or 70% VO2max in a thermoneutral environment. Immediately prior to each experiment, euhydrated subjects ingested a solution containing two non-metabolizable glucose analogs, 3-O-methyl-D-glucose (3MG; actively absorbed; 5 g) and D-xylose (passively absorbed; 5 g). During the following 5 h, all urine was collected and the amount of 3MG and D-xylose in the urine was determined. Using repeated measures ANOVA, a significant (P < 0.05) reduction in urinary excretion of each carbohydrate was observed at 70% VO2max compared to the other intensities suggesting that both active and passive intestinal absorption of glucose may be reduced during prolonged running at this intensity.
A Low Glycemic Index Meal before Exercise Improves Endurance Running Capacity in Men
Authors: Wu Ching-Lin , Williams Clyde
Published: August 2016

This study investigated the effects of ingesting a low (LGI) or high (HGI) glyce-mic index carbohydrate (CHO) meal 3 h prior to exercise on endurance running capacity. Eight male recreational runners undertook two trials (LGI or HGI) which were randomized and separated by 7 d. After an overnight fast (12 h) the subjects ingested either a LGI or HGI meal 3 h prior to running at 70% VO2max until exhaustion. The meals contained 2 g/kg body mass CHO and were isocaloric and iso-macronutrient with calculated GI values 77 and 37 for the HGI and LGI respectively. The run times for the LGI and HGI trials were 108.8 ± 4.1 min and 101.4 ± 5.2 min respectively (P = 0.038). Fat oxidation rates were higher during exercise after the LGI meal than after the HGI meal (P < 0.05). In summary, ingestion of a LGI meal 3 h before exercise resulted in a greater endurance capacity than after the ingestion of a HGI meal.
Physiological and Cognitive Responses to Caffeine during Repeated, High-Intensity Exercise
Authors: Crowe Melissa J. , Leicht Anthony S. , Spinks Warwick L.
Published: August 2016

This study investigated the effects of caffeine on repeated, anaerobic exercise using a double-blind, randomized, crossover design. Seventeen subjects (five female) underwent cognitive (reaction time, number recall) and blood (glucose, potassium, catecholamines, lactate) testing before and after consuming caffeine (6 mg/kg), placebo, or nothing (control). An exercise test (two 60 s maximal cycling bouts) was conducted 90 min after caffeine/placebo consumption. Plasma caffeine concentrations significantly increased after caffeine ingestion, however, there were no positive effects on cognitive or blood parameters except a significant decrease in plasma potassium concentrations at rest. Potentially negative effects of caffeine included significantly higher blood lactate compared to control and significantly slower time to peak power in exercise bout 2 compared to control and placebo. Caffeine had no significant effect on peak power, work output, RPE, or peak heart rate. In conclusion, caffeine had no ergogenic effect on repeated, maximal cycling bouts and may be detrimental to anaerobic performance.
Thermic and Glycemic Responses to Bread and Pasta Meals with and Without Prior Low-Intensity Exercise
Authors: Warwick Penelope M.
Published: August 2016

The purpose of the study was to investigate thermic and glycemic responses to conventional meals with and without prior low-intensity exercise. Fourteen healthy volunteers (7 men, 7 women) undertook 4 treatments, 2 bread and 2 pasta meals, either with (E) or without (NE) prior exercise (a 45-min treadmill walk). Meals provided 58 g carbohydrate and 2360 kJ. Energy expenditure and blood-glucose concentrations were measured before and for 3 h after the meals. The thermic effect of food (TEF) was lower after pasta (121 ± 32 kJ/3 h) than after bread (154 ± 62 kJ/3 h), P = 0.009, but was not affected by exercise. Glycemic responses were lower after E (155 ± 113 mmol·L−1 ·3 h−1) than NE (199 ± 97 mmol·L−1 · 3 h−1) after pasta (P = 0.020) but not after bread. TEF was lower after pasta than bread but was not affected by prior low-intensity exercise. The effects of exercise on glycemic responses to meals were inconsistent.
A Critical Examination of Dietary Protein Requirements, Benefits, and Excesses in Athletes
Authors: Phillips Stuart M. , Moore Daniel R. , Tang Jason E.
Published: August 2016

There is likely no other dietary component that inspires as much debate, insofar as athletes are concerned, as protein. How much dietary protein is required, optimal, or excessive? Dietary guidelines from a variety of sources have settled on an adequate dietary protein intake for those over the age of 19 of ~0.8–0.9 g protein·kg body weight−1·d−1. According to U.S. and Canadian dietary reference intakes (33), the recommended allowance for protein of 0.8 g protein·kg−1·d−1 is “the average daily intake level that is sufficient to meet the nutrient requirement of nearly all [~98%] . . . healthy individuals” (p. 22). The panel also stated, “in view of the lack of compelling evidence to the contrary, no additional dietary protein is suggested for healthy adults undertaking resistance or endurance exercise” (33, p. 661). Currently, no group or groups of scientists involved in establishing dietary guidelines see a need for any statement that athletes or people engaging in regular physical activity require more protein than their sedentary counterparts. Popular magazines, numerous Web sites, trainers, and many athletes decry protein intakes even close to those recommended. Even joint position stands from policy-setting groups state that “protein recommendations for endurance athletes are 1.2 to 1.4 g/kg body weight per day, whereas those for resistance and strength-trained athletes may be as high as 1.6 to 1.7 g/kg body weight per day” (1, p. 1544). The divide between those setting dietary protein requirements and those who might be making practical recommendations for athletes appears substantial, but ultimately, most athletes indicate that they consume protein at levels beyond even the highest recommendations. Thus, one might conclude that any debate on protein “requirements” for athletes is inconsequential; however, a critical analysis of existing and new data reveals novel ideas and concepts that may represent some common ground between these apparently conflicted groups. The goal of this review was to provide a critical and thorough analysis of current data on protein requirements in an attempt to provide some guidance to athletes, trainers, coaches, and sport dietitians on athletes’ protein intake. In addition, an effort was made to clearly distinguish between “required” dietary protein, “optimal” intakes, and intakes that are likely “excessive,” perhaps not from the standpoint of health, but certainly from the standpoint of potentially compromised performance.
Neutrophil-Degranulation and Lymphocyte-Subset Response after 48 hr of Fluid and/or Energy Restriction
Authors: Laing Stewart J. , Oliver Samuel J. , Wilson Sally , Walters Robert , Bilzon James L.J , Walsh Neil P.
Published: August 2016

The aim was to investigate the effects of 48 hr of fluid, energy, or combined fluid and energy restriction on circulating leukocyte and lymphocyte subset counts (CD3+, CD4+, and CD8+) and bacterially stimulated neutrophil degranulation at rest and after exercise. Thirteen healthy men (M ± SEM age 21 ± 1 yr) participated in 4 randomized 48-hr trials. During control (CON) participants received their estimated energy (2,903 ± 17 kcal/day) and fluid (3,912 ± 140 ml/day) requirements. During fluid restriction (FR) they received their energy requirements and 193 ± 19 ml/day water to drink. During energy restriction (ER) they received their fluid requirements and 290 ± 6 kcal/day. Fluid and energy restriction (F+ER) was a combination of FR and ER. After 48 hr, participants performed a 30-min treadmill time trial (TT) followed by rehydration (0–2 hr) and refeeding (2–6 hr). Circulating leukocyte and lymphocyte counts remained unchanged for CON and FR. Circulating leukocyte, lymphocyte, CD3+, and CD4+ counts decreased by ~20% in ER and ~30% in F+ER by 48 hr (p < .01), returning to within 0-hr values by 6 hr post-TT. Circulating neutrophil count and degranulation were unaltered by dietary restriction at rest and after TT. In conclusion, a 48-hr period of ER and F+ER, but not FR, decreased circulating leukocyte, lymphocyte, CD3+, and CD4+ counts but not neutrophil count or degranulation. Circulating leukocyte and lymphocyte counts normalized on refeeding. Finally, dietary restriction did not alter circulating leukocyte, lymphocyte, and neutrophil responses to 30 min of maximal exercise.
Ramadan Fasting’s Effect on Plasma Leptin, Adiponectin Concentrations, and Body Composition in Trained Young Men
Authors: Bouhlel Ezzedine , Denguezli Myriam , Zaouali Monia , Tabka Zouhair , Shephard Roy J.
Published: August 2016

Purpose:

To evaluate the effect of Ramadan fasting on parameters of insulin resistance in trained athletes at rest and after aerobic exercise.

Methods:

Nine male rugby players (age 19 ± 2 yr, height 1.78 ± 0.74 m) were tested 3 times: 1 week before observance of Ramadan (C), at the end of the first week (R1), and during the fourth week (R2). They performed a progressive cycle-ergometer test at each visit. Data collected at rest and at the end of aerobic exercise included simple anthropometry (body mass, body-mass index, body fat, fat-free mass), biochemical parameters (serum glucose, cholesterol, HDL cholesterol, triglycerides, creatinine, and serum proteins), and selected hormone concentrations (plasma insulin, leptin, and adiponectin).

Results:

Ramadan fasting was associated with a reduction of body mass and body fat (R2 vs. C, p < .01) without significant change in leptin or adiponectin levels.

Conclusion:

Lipolysis might have occurred because of increased plasma triglycerides and HDL cholesterol concentrations.
Acute Effects of Dietary Ginger on Quadriceps Muscle Pain during Moderate-Intensity Cycling Exercise
Authors: Black Christopher D. , O’Connor Patrick J.
Published: August 2016

Ginger has known hypoalgesic and anti-inflammatory properties. The effects of an oral dose of ginger on quadriceps muscle pain, rating of perceived exertion (RPE), and recovery of oxygen consumption were examined during and after moderateintensity cycling exercise. Twenty-five college-age participants ingested a 2-g dose of ginger or placebo in a double-blind, crossover design and 30 min later completed 30 min of cycling at 60% of VO2peak. Quadriceps muscle pain, RPE, work rate, heart rate (HR), and oxygen uptake (VO2) were recorded every 5 min during exercise, and HR and VO2 were recorded for 20 min after exercise. Compared with placebo, ginger had no clinically meaningful or statistically significant effect on perceptions of muscle pain, RPE, work rate, HR, or VO2 during exercise. Recovery of VO2 and HR after the 30-min exercise bout followed a similar time course in the ginger and placebo conditions. The results were consistent with related findings showing that ingesting a large dose of aspirin does not acutely alter quadriceps muscle pain during cycling, and this suggests that prostaglandins do not play a large role in this type of exercise-induced skeletal-muscle pain. Ginger consumption has also been shown to improve VO2 recovery in an equine exercise model, but these results show that this is not the case in humans.
Carbohydrate and Protein Hydrolysate Coingestion’s Improvement of Late-Exercise Time-Trial Performance
Authors: Saunders Michael J. , Moore Rebecca W. , Kies Arie K. , Luden Nicholas D. , Pratt Casey A.
Published: August 2016

This study examined whether a carbohydrate + casein hydrolysate (CHO+ProH) beverage improved time-trial performance vs. a CHO beverage delivering ~60 g CHO/hr. Markers of muscle disruption and recovery were also assessed. Thirteen male cyclists (VO2peak = 60.8 ± 1.6 ml · kg−1 · min−1) completed 2 computer-simulated 60-km time trials consisting of 3 laps of a 20-km course concluding with a 5-km climb (~5% grade). Participants consumed 200 ml of CHO (6%) or CHO+ProH beverage (6% + 1.8% protein hydrolysate) every 5 km and 500 ml of beverage immediately postexercise. Beverage treatments were administered using a randomly counterbalanced, double-blind design. Plasma creatine phosphokinase (CK) and muscle-soreness ratings were assessed immediately before and 24 hr after cycling. Mean 60-km times were 134.4 ± 4.6 and 135.0 ± 4.0 min for CHO+ProH and CHO beverages, respectively. All time differences between treatments occurred during the final lap, with protein hydrolysate ingestion explaining a significant (p < .05) proportion of betweentrials differences over the final 20 km (44.3 ± 1.6, 45.0 ± 1.6 min) and final 5 km (16.5 ± 0.6, 16.9 ± 0.6 min). Plasma CK levels and muscle-soreness ratings increased significantly after the CHO trial (161 ± 53, 399 ± 175 U/L; 15.8 ± 5.1, 37.6 ± 5.7 mm) but not the CHO+ProH trial (115 ± 21, 262 ± 88 U/L; 20.9 ± 5.3, 32.2 ± 7.1 mm). Late-exercise time-trial performance was enhanced with CHO+ProH beverage ingestion compared with a beverage containing CHO provided at maximal exogenous oxidation rates during exercise. CHO+ProH ingestion also prevented increases in plasma CK and muscle soreness after exercise.
Increased Lipid Peroxidation in Trained Men after 2 Weeks of Antioxidant Supplementation
Authors: Lamprecht Manfred , Hofmann Peter , Greilberger Joachim F. , Schwaberger Guenther
Published: August 2016

Purpose:

To assess the effects of an encapsulated antioxidant concentrate (EAC) and exercise on lipid peroxidation (LIPOX) and the plasma antioxidant enzyme glutathione peroxidase (Pl-GPx).

Methods:

Eight trained male cyclists (VO2max > 55 ml · kg−1 · min−1) participated in this randomized, placebo-controlled, double-blinded, crossover study and undertook 4 cycle-ergometer bouts: 2 moderate exercise bouts over 90 min at 45% of individual VO2max and 2 strenuous exercise bouts at 75% of individual VO2max for 30 min. The first 2 exercise tests—1 moderate and 1 strenuous—were conducted after 4 weeks wash-out and after 12 and 14 days of EAC (107 IU vitamin E, 450 mg vitamin C, 36 mg β-carotene, 100 μg selenium) or placebo treatment. After another 4 weeks wash-out, participants were given the opposite capsule treatment and repeated the 2 exercise tests. Physical exercise training was equal across the whole study period, and nutrition was standardized by a menu plan the week before the tests. Blood was collected before exercise, immediately postexercise, and 30 min and 60 min after each test. Plasma samples were analyzed for LIPOX marker malondialdehyde (MDA) and the antioxidant enzyme pl-GPx.

Results:

MDA concentrations were significantly increased after EAC supplementation at rest before exercise and after moderate exercise (p < .05). MDA concentrations showed no differences between treatments after strenuous exercise (p > .1). Pl-GPx concentrations decreased at all time points of measurement after EAC treatment (p < .05).

Conclusions:

The EAC induced an increase of LIPOX as indicated by MDA and decreased pl-GPx concentrations pre- and postexercise.
Water and Salt Balance of Well-Trained Swimmers in Training
Authors: Maughan Ronald J. , Dargavel Lisa A. , Hares Rachael , Shirreffs Susan M.
Published: August 2016

This study investigated fluid and electrolyte balance in well-trained male and female swimmers during 2 training sessions. Participants were 17 nationally ranked swimmers measured during a period of intensive training. Sweat loss was assessed from changes in body mass after correction for fluid intake and urine collection. Sweat composition was measured from waterproof absorbent patches applied at 4 skin sites. Air and pool-water temperatures were 36 °C and 27.4 °C, respectively. Training lasted 105 min in each session. All measured variables were similar on the 2 testing days. Mean sweat-volume loss was 548 ± 243 ml, and mean sweat rate was 0.31 ± 0.1 L/hr. Mean fluid intake was 489 ± 270 ml. Mean body-mass loss was 0.10 ± 0.50 kg, equivalent to 0.1% ± 0.7% dehydration. Mean pretraining urine osmolality was 662 ± 222 mOsm/kg, which was negatively associated with both mean drink volume consumed (p = .044, r2 = .244) and mean urine volume produced during training (p = .002, r2 = .468). Mean sweat Na+, K+, and Cl− concentrations (mmol/L) were 43 ± 14, 4 ± 1, and 31± 9, respectively; values were not different between males and females and were not different between days except for a marginal difference in K+ concentration. The average swimmer remained hydrated during the session, and calculated sweat rates were similar to those in previous aquatic studies.
Making the Weight: A Case Study From Professional Boxing
Authors: Morton James P. , Robertson Colin , Sutton Laura , M Don P.
Published: August 2016

Professional boxing is a combat sport categorized into a series of weight classes. Given the sport’s underpinning culture, boxers’ typical approach to “making weight” is usually via severe acute and/or chronic energy restriction and dehydration. Such practices have implications for physical performance and also carry health risks. This article provides a case-study account outlining a more structured and gradual approach to helping a professional male boxer make weight for the 59-kg superfeatherweight division. Over a 12-week period, the client athlete adhered to a daily diet approximately equivalent to his resting metabolic rate (6–7 MJ; 40% carbohydrate, 38% protein, 22% fat). Average body-mass loss was 0.9 ± 0.4 kg/wk, equating to a total loss of 9.4 kg. This weight loss resulted in a decrease in percent body fat from 12.1% to 7.0%. In the 30 hr between weigh-in and competition, the client consumed a high-carbohydrate diet (12 g/kg body mass) supported by appropriate hydration strategies and subsequently entered the ring at a fighting weight of 63.2 kg. This nutritional strategy represented a major change in the client’s habitual weight-making practices and did not rely on any form of intended dehydration during the training period or before weighing in. The intervention demonstrates that a more gradual approach to making weight in professional boxing can be successfully achieved via a combination of restricted energy intake and increased energy expenditure, providing there is willingness on the part of the athlete and coaches involved to adopt novel practices.
Evaluation of Iranian College Athletes’ Sport Nutrition Knowledge
Authors: Jessri Mahsa , Jessri Maryam , RashidKhani Bahram , Zinn Caryn
Published: August 2016

The purpose of this study was to assess the nutrition knowledge and the factors determining this knowledge in Iranian college basketball and football athletes. By highlighting gaps in nutrition knowledge of these athletes, sport nutrition professionals may begin to address these gaps by educating athletes with a view toward minimizing injury and enhancing sport performance. Sixty-six basketball and 141 football players (response rate 78.4%) from 4 medical and 8 nonmedical universities in Tehran agreed to participate in this cross-sectional study. A 2-part questionnaire was used; the first part comprised questions identifying demographic information, and the second part comprised a previously well-validated questionnaire on sport nutrition knowledge. The overall knowledge score was 33.2% (± 12.3%). Men scored 28.2% (± 12.7%), and women, 38.7% (± 14.2%). In both genders, the highest score was obtained for the nutrients subcategory, and the supplements subcategory was the most poorly answered. When compared with their peers, a significantly higher score was obtained by women (p < .001), athletes at medical universities (p < .001), and those obtaining nutrition information from reputable sources (p = .03). The coach was cited by 89.4% of athletes as their main source of nutrition information. This study showed that the sport nutrition knowledge of these athletes is inadequate. Considering that this substandard level of knowledge may contribute to poor dietary behaviors, these athletes would benefit from nutrition-related training and education.
Nutritional Strategies to Promote Postexercise Recovery
Authors: Beelen Milou , Burke Louise M. , Gibala Martin J. , van Loon Luc J.C.
Published: August 2016

During postexercise recovery, optimal nutritional intake is important to replenish endogenous substrate stores and to facilitate muscle-damage repair and reconditioning. After exhaustive endurance-type exercise, muscle glycogen repletion forms the most important factor determining the time needed to recover. Postexercise carbohydrate (CHO) ingestion has been well established as the most important determinant of muscle glycogen synthesis. Coingestion of protein and/or amino acids does not seem to further increase muscle glycogensynthesis rates when CHO intake exceeds 1.2 g · kg−1 · hr−1. However, from a practical point of view it is not always feasible to ingest such large amounts of CHO. The combined ingestion of a small amount of protein (0.2–0.4 g · (0.2−0.4 g · kg−1 · hr−1) with less CHO (0.8 g · kg−1 · hr−1) stimulates endogenous insulin release and results in similar muscle glycogen-repletion rates as the ingestion of 1.2 g · kg−1 · hr−1 CHO. Furthermore, postexercise protein and/or amino acid administration is warranted to stimulate muscle protein synthesis, inhibit protein breakdown, and allow net muscle protein accretion. The consumption of ~20 g intact protein, or an equivalent of ~9 g essential amino acids, has been reported to maximize muscle protein-synthesis rates during the first hours of postexercise recovery. Ingestion of such small amounts of dietary protein 5 or 6 times daily might support maximal muscle protein-synthesis rates throughout the day. Consuming CHO and protein during the early phases of recovery has been shown to positively affect subsequent exercise performance and could be of specific benefit for athletes involved in multiple training or competition sessions on the same or consecutive days.
Regular Dark Chocolate Consumption’s Reduction of Oxidative Stress and Increase of Free-Fatty-Acid Mobilization in Response to Prolonged Cycling
Authors: Allgrove Judith , Farrell Emily , Gleeson Michael , Williamson Gary , Cooper Karen
Published: August 2016

This study investigated the effects of regular consumption of dark chocolate (DC), rich in cocoa polyphenols, on plasma metabolites, hormones, and markers of oxidative stress after prolonged exhaustive exercise. Twenty active men cycled at 60% maximal oxygen uptake (VO2max) for 1.5 hr, with the intensity increased to 90% VO2max for a 30-s period every 10 min, followed by a ride to exhaustion at 90% VO2max. In the 2 wk before exercise participants consumed 40 g of DC or an isocarbohydrate-fat control cocoa liquor–free chocolate (CON) twice daily and once 2 hr before exercise in a randomized, counterbalanced, crossover design. Venous blood samples were taken immediately before exercise, postexercise (fixed duration), postexhaustion, and after 1 hr of recovery. F2-isoprostanes were significantly lower (post hoc tests: p < .001) at exhaustion and after 1 hr of recovery with DC. Oxidized low-density lipoproteins were significantly lower with DC (p < .001) both before and after exercise and at exhaustion. DC was also associated with ~21% greater rises in free fatty acids during exercise (main effect: p < .05). Changes in circulating glucose, insulin, glucagon, cortisol, and interleukin (IL)-6, IL-10, and IL-1ra were unaffected by treatment. Time to exhaustion at 90% VO2max was not significantly different between trials (398 ± 204 and 374 ± 194 s for DC and CON, respectively). These results suggest that regular DC intake is associated with reduced oxidative-stress markers and increased mobilization of free fatty acids after exercise but has no observed effect on exercise performance.
The Acute Effect of Ingesting a Quercetin-Based Supplement on Exercise-Induced Inflammation and Immune Changes in Runners
Authors: Konrad Manuela , Nieman David C. , Henson Dru A. , Kennerly Krista M. , Jin Fuxia , Wallner-Liebmann Sandra J.
Published: August 2016

This study tested the acute anti-inflammatory and immune-modulating influence of a quercetin-based supplement consumed by endurance athletes 15 min before an intense 2-hr run. In this randomized, crossover study, 20 runners (11 men, 9 women, age 38.4 ± 2.1 yr) completed two 2-hr treadmill runs at 70% VO2max (3 wk apart). Subjects ingested either 4 quercetin-based chews (Q-chew) or placebo chews (PL) 15 min before the runs. The 4 Q-chews provided 1,000 mg quercetin, 120 mg epigallocatechin 3-gallate, 400 mg isoquercetin, 400 mg each eicosapentaenoic acid and docosahexaenoic acid, 1,000 mg vitamin C, and 40 mg niacinamide. Subjects provided blood samples 30 min before, immediately after, and 1 hr postexercise and were analyzed for plasma quercetin, total blood leukocytes (WBC), C-reactive protein (CRP), 9 cytokines (IL-6, TNFα, GM-CSF, IFNγ, IL-1β, IL-2, IL-8, IL-10, and IL-12p70), granulocyte (GR) and monocyte (MO) phagocytosis (PHAG), and oxidative-burst activity (OBA). Plasma quercetin increased from 80.0 ± 26.0 μg/L to 6,337 ± 414 μg/L immediately postexercise and 4,324 ± 310 μg/L 1 hr postexercise after ingestion of Q-chews, compared with no change in PL (p < .001). Exercise caused significant increases in, CRP, GM-CSF, IL-10, IL-1β, IL-2, IL-6, IL-8, TNFα, GR-PHAG, and MO-PHAG and decreases in GR-OBA and MO-OBA, but no differences in the pattern of change were measured between Q-chew and PL trials. Acute ingestion of Q-chews 15 min before heavy exertion caused a strong increase in plasma quercetin levels but did not counter postexercise inflammation or immune changes relative to placebo.
Energy Intakes of Ultraendurance Cyclists During Competition, an Observational Study
Authors: Black Katherine E. , Skidmore Paula M.L. , Brown Rachel C.
Published: August 2016

Endurance events >10 hr are becoming increasingly popular but provide numerous physiological challenges, several of which can be attenuated with optimal nutritional intakes. Previous studies in ultraendurance races have reported large energy deficits during events. The authors therefore aimed to assess nutritional intakes in relation to performance among ultraendurance cyclists. This observational study included 18 cyclists in a 384-km cycle race. At race registration each cyclist’s support crew was provided with a food diary for their cyclist. On completion of the race, cyclists were asked to recall their race food and drink intakes. All food and fluids were analyzed using a computer software package. Mean (SD) time to complete the race was 16 hr 21 min (2 hr 2 min). Mean (SD) energy intake was 18.7 (8.6) MJ, compared with an estimated energy requirement for the race of 25.5 (7.4) MJ. There was a significant negative relationship between energy intake and time taken to complete the race (p = .023, r2 = −.283). Mean (SD) carbohydrate, fat, and protein intakes were 52 (27), 15.84 (56.43), and 2.94 (7.25) g/hr, respectively. Only carbohydrate (p = .015, r2 = −.563) and fat intake (p = .037, r2 = −.494) were associated with time taken to complete the race. This study demonstrates the difficulties in meeting the high energy demands of ultraendurance cycling. The relationship between energy intake and performance suggests that reducing the energy deficit may be advantageous. Given the high carbohydrate intakes of these athletes, increasing energy intake from fat should be investigated as a means of decreasing energy deficits.
Effect of Sprint Interval Exercise on Postexercise Metabolism and Blood Pressure in Adolescents
Authors: Burns Stephen F. , Oo Hnin Hnin , Tran Anh Thanh Thuy
Published: August 2016

The current study examined the effect of sprint interval exercise on postexercise oxygen consumption, respiratory-exchange ratio (RER), substrate oxidation, and blood pressure in adolescents. Participants were 10 normal-weight healthy youth (7 female), age 15–18 years. After overnight fasts, each participant undertook 2 trials in a random balanced order: (a) two 30-s bouts of sprint interval exercise on a cycle ergometer and (b) rested in the laboratory for an equivalent period. Timematched measurements of oxygen consumption, RER, and blood pressure were made 90 min into recovery, and substrate oxidation were calculated over the time period. Total postexercise oxygen uptake was significantly higher in the exercise than control trial over the 90 min (mean [SD]: control 20.0 [6.0] L, exercise 24.8 [9.8] L; p = .030). After exercise, RER was elevated above control but then fell rapidly and was lower than control 30–60 min postexercise, and fat oxidation was significantly higher in the exercise than control trial 45–60 min postexercise. However, total fat oxidation did not differ between trials (control 4.5 [2.5] g, exercise 5.4 [2.7] g; p = .247). Post hoc tests revealed that systolic blood pressure was significantly lower than in control at 90 min postexercise (control 104 [10] mm Hg, exercise 99 [10] mm Hg; p < .05). These data indicate that acute sprint interval exercise leads to short-term increases in oxygen uptake and reduced blood pressure in youth. The authors suggest that health outcomes in response to sprint interval training be examined in children.
Effect of Intake of Different Dietary Protein Sources on Plasma Amino Acid Profiles at Rest and after Exercise
Authors: Burke Louise M. , Winter Julie A , Cameron-Smith David , Enslen Marc , Farnfield Michelle , Decombaz Jacques
Published: August 2016

The authors undertook 2 crossover-designed studies to characterize plasma amino acid (AA) responses to the intake of 20 g of protein. In Study 1, 15 untrained and overnight-fasted subjects consumed 20 g protein from skim milk, soy milk, beefsteak, boiled egg, and a liquid meal supplement. In Study 2, 10 fasted endurance-trained subjects consumed 20 g protein from a protein-rich sports bar at rest and after a 60-min submaximal ride. Plasma AA concentrations were measured immediately before and for 180 min after food ingestion using a gas-chromatography flame-ionization detection technique. A pharmacokinetic analysis was undertaken for profiles of total AAs (TAA), essential AAs, branched-chain AAs (BCAA), and leucine. Although area-under-the-curve values for plasma TAA were similar across protein sources, the pattern of aminoacidemia showed robust differences between foods, with liquid forms of protein achieving peak concentrations twice as quickly after ingestion as solid protein-rich foods (e.g., ~50 min vs ~100 min) and skim milk achieving a significantly faster peak leucine concentration than all other foods (~25 min). Completing exercise before ingesting protein sources did not cause statistically significant changes in the pattern of delivery of key AAs, BCAAs, and leucine apart from a 20–40% increase in the rate of elimination. These results may be useful to plan the type and timing of intake of protein-rich foods to maximize the protein synthetic response to various stimuli such as exercise.
The Effect of Progressive Resistance Training on Oxidative Stress and Antioxidant Enzyme Activity in Erythrocytes in Untrained Men
Authors: Azizbeigi Kamal , Azarbayjani Mohammad Ali , Peeri Maghsoud , Agha-alinejad Hamid , Stannard Stephen
Published: August 2016

This study was undertaken to investigate the effects of progressive resistance-training (PRT) on plasma oxidative stress and antioxidant enzyme activity in erythrocytes. Twenty male volunteers were randomly assigned to 2 groups: PRT and control. Blood samples were collected before and after 8 wk of PRT and analyzed for enzymatic activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) in erythrocytes, plasma total antioxidant capacity (TAC), and malondialdehyde concentration (MDA, an index of lipid per oxidation in plasma). Resistance training commenced with 8 exercises on nonconsecutive days for 8 wk at 50% of estimated 1-repetition maximum (E1RM) and reached 80% E1RM by Week 8. The results showed that PRT significantly increased erythrocyte SOD activity (1,323 ± 212.52 vs. 1,449.9 ± 173.8 U/g Hb, p = .014). Plasma concentration of MDA also decreased (5.39 ± 1.7 vs. 3.67.4 ± 0.7 nmol/ml, p = .030), although TAC (1.42 ± 0.21 vs. 1.61 ± 0.19 mmol/L, p = .1530) and GPx (39.87 ± 11.5 vs. 48.18 ± 14.48 U/g Hb, p = .883) activity did not undergo any considerable changes. Based on these data, the authors conclude that an 8-wk program of PRT strengthens the defensive system of erythrocytes against free-radical damage and therefore can be applied as a useful approach to alleviate oxidative stress.
Paced Breathing in Roller-Ski Skating: Effects on Metabolic Rate and Poling Forces
Authors: Fabre Nicolas , Perrey Stéphane , Arbez Loïc , Rouillon Jean-Denis
Published: August 2016

Purpose:

This study aimed (1) to determine whether paced breathing (synchronization of the expiration phase with poling time) would reduce the metabolic rate and dictate a lower rate of perceived exertion (RPE) than does spontaneous breathing and (2) to analyze the effects of paced breathing on poling forces and stride-mechanics organization during roller-ski skating exercises.

Methods:

Thirteen well-trained cross-country skiers performed 8 submaximal roller-skiing exercises on a motorized driven treadmill with 4 modes of skiing (2 skating techniques, V2 and V2A, at 2 exercise intensities) by using 2 patterns of breathing (unconscious vs conscious). Poling forces and stride-mechanics organization were measured with a transducer mounted in ski poles. Oxygen uptake (VO2) was continuously collected. After each bout of exercise RPE was assessed by the subject.

Results:

No difference was observed for VO2between spontaneous and paced breathing conditions, although RPE was lower with paced breathing (P< .05). Upper-limb cycle time and recovery time were significantly (P< .05) increased by paced breathing during V2A regardless of the exercise intensity, but no changes for poling time were observed. A slight trend of increased peak force with paced breathing was observed (P= .055).

Conclusion:

The lack of a marked effect of paced breathing on VO2and some biomechanical variables could be explained by the extensive experience of our subjects in cross-country skiing.
VO2 Attained During Treadmill Running: The Influence of a Specialist (400-m or 800-m) Event
Authors: V.B. James David , Sandals Leigh E. , Draper Stephen B. , Maldonado-Martín Sara , Wood Dan M.
Published: August 2016

Purpose:

Previously it has been observed that, in well-trained 800-m athletes, VO2max is not attained during middle-distance running events on a treadmill, even when a race-type pacing strategy is adopted. Therefore, the authors investigated whether specialization in a particular running distance (400-m or 800-m) influences the VO2 attained during running on a treadmill.

Methods:

Six 400-m and six 800-m running specialists participated in the study. A 400-m trial and a progressive test to determine VO2max were completed in a counterbalanced order. Oxygen uptakes attained during the 400-m trial were compared to examine the influence of specialist event.

Results:

A VO2 plateau was observed in all participants for the progressive test, demonstrating the attainment of VO2max. The VO2max values were 56.2 ± 4.7 and 69.3 ± 4.5 mL · kg−1 · min−1 for the 400-m- and 800-m-event specialists, respectively (P = .0003). Durations for the 400-m trial were 55.1 ± 4.2 s and 55.8 ± 2.3 s for the 400-m- and 800-m-event specialists, respectively. The VO2 responses achieved were 93.1% ± 2.0% and 85.7% ± 3.0% VO2max for the 400-m- and 800-m-event specialists, respectively (P = .001).

Conclusions:

These results demonstrate that specialist running events do appear to influence the percentage of VO2max achieved in the 400-m trial, with the 800-m specialists attaining a lower percentage of VO2max than the 400-m specialists. The 400-m specialists appear to compensate for a lower VO2max by attaining a higher percentage VO2max during a 400-m trial.
Live High + Train Low: Thinking in Terms of an Optimal Hypoxic Dose
Authors: Wilber Randall L.
Published: August 2016

“Live high-train low” (LH+TL) altitude training allows athletes to “live high” for the purpose of facilitating altitude acclimatization, as characterized by a significant and sustained increase in endogenous erythropoietin and subsequent increase in erythrocyte volume, while simultaneously enabling them to “train low” for the purpose of replicating sea-level training intensity and oxygen flux, thereby inducing beneficial metabolic and neuromuscular adaptations. In addition to natural/terrestrial LH+TL, several simulated LH+TL devices have been developed including nitrogen apartments, hypoxic tents, and hypoxicator devices. One of the key issues regarding the practical application of LH+TL is what the optimal hypoxic dose is that is needed to facilitate altitude acclimatization and produce the expected beneficial physiological responses and sea-level performance effects. The purpose of this review is to examine this issue from a research-based and applied perspective by addressing the following questions: What is the optimal altitude at which to live, how many days are required at altitude, and how many hours per day are required? It appears that for athletes to derive the hematological benefits of LH+TL while using natural/terrestrial altitude, they need to live at an elevation of 2000 to 2500 m for >4 wk for >22 h/d. For athletes using LH+TL in a simulated altitude environment, fewer hours (12-16 h) of hypoxic exposure might be necessary, but a higher elevation (2500 to 3000 m) is required to achieve similar physiological responses.
The Relationships Between Science and Sport: Application in Triathlon
Authors: Millet Gregoire P. , Bentley David J. , Vleck Veronica E.
Published: August 2016

The relationships between sport sciences and sports are complex and changeable, and it is not clear how they reciprocally influence each other. By looking at the relationship between sport sciences and the “new” (~30-year-old) sport of triathlon, together with changes in scientific fields or topics that have occurred between 1984 and 2006 (278 publications), one observes that the change in the sport itself (eg, distance of the events, wetsuit, and drafting) can influence the specific focus of investigation. The sport-scientific fraternity has successfully used triathlon as a model of prolonged strenuous competition to investigate acute physiological adaptations and trauma, as support for better understanding cross-training effects, and, more recently, as a competitive sport with specific demands and physiological features. This commentary discusses the evolution of the scientific study of triathlon and how the development of the sport has affected the nature of scientific investigation directly related to triathlon and endurance sport in general.
Hydration Status, Knowledge, and Behavior in Youths at Summer Sports Camps
Authors: Decher Nora R. , Casa Douglas J. , Yeargin Susan W. , Ganio Matthew S. , Levreault Michelle L. , Dann Catie L. , James Camille T. , McCaffrey Megan A. , O’Connor Caitlin B. , Brown Scott W.
Published: August 2016

Purpose:

To assess the hydration status and level of hydration knowledge of youths at summer sports camps.

Methods:

Sixty-seven active youths, 57 males (mean ± SD, 12 ± 2 y, 136 ± 16 cm, 50.6 ± 21.1 kg) and 10 females (13 ± 2 y, 153 ± 8 cm, 45.2 ± 9.0 kg) participated in 4 d of sports camp. Hydration status was assessed before the first practice (AM) and after the second practice (PM). Participants completed suriveys assessing hydration knowledge (HAQ) and hydration habits on day 3 and a self-assessment (EQ#1).

Results:

Mean AM urine specific gravity (USG) and urine osmolality (Uosm) scores ranged from minimal to significant dehydration across 4 d, even when temperatures were mild. Correlations between hydration indices and EQ#1, ranging from 0.11 to −0.51, were statistically significant (P< .05), indicating that subjects recognized when they were doing a good or bad job hydrating. HAQ did not correlate strongly with hydration indices suggesting other impediments to hydration. Thirst correlated negatively with EQ#1 (from −0.29 to −0.60).

Conclusion:

Hydration at summer sports camp is a concern and special efforts need to be made to help youths develop hydration strategies.
Physiological Responses to Cold Water Immersion Following Cycling in the Heat
Authors: Halson Shona L. , Quod Marc J. , Martin David T. , Gardner Andrew S. , Ebert Tammie R. , Laursen Paul B.
Published: August 2016

Cold water immersion (CWI) has become a popular means of enhancing recovery from various forms of exercise. However, there is minimal scientific information on the physiological effects of CWI following cycling in the heat.

Purpose:

To examine the safety and acute thermoregulatory, cardiovascular, metabolic, endocrine, and inflammatory responses to CWI following cycling in the heat.

Methods:

Eleven male endurance trained cyclists completed two simulated ~40-min time trials at 34.3 ± 1.1°C. All subjects completed both a CWI trial (11.5°C for 60 s repeated three times) and a control condition (CONT; passive recovery in 24.2 ± 1.8°C) in a randomized cross-over design. Capillary blood samples were assayed for lactate, glucose, pH, and blood gases. Venous blood samples were assayed for catecholamines, cortisol, testosterone, creatine kinase, C-reactive protein, IL-6, and IGF-1 on 7 of the 11 subjects. Heart rate (HR), rectal (Tre), and skin temperatures (Tsk) were measured throughout recovery.

Results:

CWI elicited a significantly lower HR (CWI: Δ116 ± 9 bpm vs. CONT: Δ106 ± 4 bpm; P = .02), Tre (CWI: Δ1.99 ± 0.50°C vs. CONT: Δ1.49 ± 0.50°C; P = .01) and Tsk. However, all other measures were not significantly different between conditions. All participants subjectively reported enhanced sensations of recovery following CWI.

Conclusion:

CWI did not result in hypothermia and can be considered safe following high intensity cycling in the heat, using the above protocol. CWI significantly reduced heart rate and core temperature; however, all other metabolic and endocrine markers were not affected by CWI.
The Effects of Wearing Lower-Body Compression Garments During Endurance Cycling
Authors: Scanlan Aaron T. , Dascombe Benjamin J. , R.J. Reaburn Peter , Osborne Mark
Published: August 2016

Purpose:

The present investigation examined the physiological and performance effects of lower-body compression garments (LBCG) during a one-hour cycling time-trial in well-trained cyclists.

Methods:

Twelve well-trained male cyclists ([mean ± SD] age: 20.5 ± 3.6 years; height: 177.5 ± 4.9 cm; body mass: 70.5 ± 7.5 kg; VO2max: 55.2 ± 6.8 mL·kg−1·min−1) volunteered for the study. Each subject completed two randomly ordered stepwise incremental tests and two randomly ordered one-hour time trials (1HTT) wearing either full-length SportSkins Classic LBCG or underwear briefs (control). Blood lactate concentration ([BLa−]), heart rate (HR), oxygen consumption (VO2) and muscle oxygenation (mOxy) were recorded throughout each test. Indicators of cycling endurance performance were anaerobic threshold (AnT) and VO2max values from the incremental test, and mean power (W), peak power (W), and total work (kJ) from the 1HTT Magnitude-based inferences were used to determine if LBCG demonstrated any performance and/or physiological benefits.

Results:

A likely practically significant increase (86%:12%:2%; η2 = 0.6) in power output at AnT was observed in the LBCG condition (CONT: 245.9 ± 55.7 W; LBCG: 259.8 ± 44.6 W). Further, a possible practically significant improvement (78%:19%:3%; η2 = 0.6) was reported in muscle oxygenation economy (W·%mOxy−1) across the 1HTT (mOxy: CONT: 52.2 ± 12.2%; LBCG: 57.3 ± 8.2%).

Conclusions:

The present results demonstrated limited physiological benefits and no performance enhancement through wearing LBCG during a cycling time trial.