bluuebunny/crossref_metadata_2025 huggingface dataset:
Creatine Supplementation in Young Soccer Players
Authors: Ostojic Sergej M.
Published: August 2016

The purpose of this study was to examine the effects of acute creatine-monohydrate supplementation on soccer-specific performance in young soccer players. Twenty young male soccer players (16.6 ± 1.9 years) participated in the study and were matched and allocated to 2 randomly assigned trials: ingesting creatine-monohydrate supplement (3 × 10-g doses) or placebo for 7 days. Before and after the supplementation protocol, each subject underwent a series of soccer-specific skill tests: dribble test, sprint-power test, endurance test, and vertical jump test. Specific dribble test times improved significantly in the creatine group (13.0 ± 1.5 vs. 10.2 ± 1.8 s; p < .05) after supplementation protocol. Sprint-power test times were significantly improved after creatine-monohydrate supplementation (2.7 ± 0.4 vs. 2.2 ± 0.5 s; p < .05) as well as vertical jump height (49.2 ± 5.9 vs. 55.1 ± 6.3 cm; p < .05) in creatine trial. Furthermore, dribble and power test times, along with vertical jump height, were superior in creatine versus placebo trial (p < .05) at post-supplementation performance. There were no changes in specific endurance test results within or between trials (p > .05). There were no between-trial differences in the placebo trial (p > .05). The main finding of the present study indicates that supplementation with creatine in young soccer players improved soccer-specific skill performance compared with ingestion of placebo.
Fluid, Electrolyte, and Renal Indices of Hydration during 11 Days of Controlled Caffeine Consumption
Authors: Armstrong Lawrence E. , Pumerantz Amy C. , Roti Melissa W. , Judelson Daniel A. , Watson Greig , Dias Joao C. , Sökmen Bülent , Casa Douglas J. , Maresh Carl M. , Lieberman Harris , Kellogg Mark
Published: August 2016

This investigation determined if 3 levels of controlled caffeine consumption affected fluid-electrolyte balance and renal function differently. Healthy males (mean ± standard deviation; age, 21.6 ± 3.3 y) consumed 3 mg caffeine · kg−1 · d−1 on days 1 to 6 (equilibration phase). On days 7 to 11 (treatment phase), subjects consumed either 0 mg (C0; placebo; n = 20), 3 mg (C3; n = 20), or 6 mg (C6; n = 19) caffeine · kg−1 · d−1 in capsules, with no other dietary caffeine intake. The following variables were unaffected (P > 0.05) by different caffeine doses on days 1, 3, 6, 9, and 11 and were within normal clinical ranges: body mass, urineosmolality, urine specific gravity, urine color, 24-h urine volume, 24-h Na+ and K+ excretion, 24-h creatinine, blood urea nitrogen, serum Na+ and K+, serum osmolality, hematocrit, and total plasma protein. Therefore, C0, C3, and C6 exhibited no evidence of hypohydration. These findings question the widely accepted notion that caffeine consumption acts chronically as a diuretic.
Effect of Carbohydrate Intake on Half-Marathon Performance of Well-Trained Runners
Authors: Burke Louise M. , Wood Clare , Pyne David B. , Telford Richard D. , Saunders Philo U.
Published: August 2016

Eighteen highly-trained runners ran two half marathons in mild environmental conditions, 3 wk apart, consuming either 426 ± 227 mL of a flavored placebo drink (PLACEBO) or an equivalent volume of water (386 ± 185 mL) and a commercial gel (GEL) supplying 1.1 ± 0.2 g/kg body mass (BM) carbohydrate (CHO). Voluntary consumption of this fluid was associated with a mean BM change of ~ 2.4%. Runners performed better in their second race by 0.9% or 40 s (P = 0.03). Three runners complained of gastrointestinal discomfort in GEL trial, which produced a clear impairment of half-marathon performance by 2.4% or 105 s (P = 0.03 ) . The effect of GEL on performance was trivial: time was improved b y 0.3% or 14 s compared with PLACEBO (P = 0.52). Consuming the gel was associated with a 2.4% slower time through the 2 × 200 m feed zone; adding a trivial ~ 2 s to race time. Although benefits to half marathon performance were not detected, the theoretical improvement during 1-h exercise with CHO intake merits further investigation.
Carbohydrate Supplementation and Immune Responses after Acute Exhaustive Resistance Exercise
Authors: Carlson Lara A. , Headley Samuel , DeBruin Jason , Tuckow Alex P. , Koch Alexander J. , Kenefick Robert W.
Published: August 2016

This investigation sought to study changes in leukocyte subsets after an acute bout of resistance exercise (ARE) and to determine whether ingestion of carbohydrate (CHO) could attenuate those immune responses. Nine male track-and-field athletes (21.1 ± 1.4 yr, 177.2 ± 5.5 cm, 80.9 ± 9.7 kg, 8.7% ± 3.8% fat) and 10 male ice hockey athletes (21.0 ± 2.2 yr, 174.3 ± 6.2 cm, 79.6 ±11.1 kg, 13.9% ± 3.73% fat) participated in 2 different ARE protocols. Both experiments employed a counterbalanced double-blind research design, wherein participants consumed either a CHO (1 g/kg body weight) or placebo beverage before, during, and after a weight-lifting session. Serum cortisol decreased (p < .05) at 90 min into recovery compared with immediately postexercise. Plasma lactate, total leukocyte, neutrophil, and monocyte concentrations increased (p < .05) from baseline to immediately postexercise. Lymphocytes decreased significantly (p < .05) from baseline to 90 min postexercise. Lymphocytes were lower (p < .05) for the CHO condition than for placebo. The findings of this study indicate the following: ARE appears to evoke changes in immune cells similar to those previously reported during endurance exercise, and CHO ingestion attenuates lymphocytosis after ARE.
Antioxidant Status, Oxidative Stress, and Damage in Elite Trained Kayakers and Canoeists and Sedentary Controls
Authors: Teixeira Vitor , Valente Hugo , Casal Susana , Marques Franklim , Moreira Pedro
Published: August 2016

Strenuous physical activity is known to generate reactive oxygen species to a point that can exceed the antioxidant defense system and lead to oxidative stress. Dietary intake of antioxidants, plasma enzymatic (superoxide dismutase, glutathione reductase [Gr], and glutathione peroxidase [GPx]) activities, nonenzymatic (total antioxidant status [TAS], uric acid, α-tocopherol, retinol, α-carotene, β-carotene, lycopene, and lutein + zeaxanthin) antioxidants, and markers of lipid peroxidation (thiobarbituricacid-reactive substances [TBARS]) and muscle damage (creatine kinase [CK]) were measured in 17 elite male kayakers and canoeists under resting conditions and in an equal number of age- and sex-matched sedentary individuals. Athletes showed increased plasma values of α-tocopherol (p = .037), α-carotene (p = .003), β-carotene (p = .007), and superoxide dismutase activity (p = .002) and a lower TAS level (p = .030). Antioxidant intake (α-tocopherol, vitamin C, and β-carotene) and plasmatic GPx, Gr, lycopene, lutein + zeaxanthin, retinol, and uric acid levels were similar in both groups. Nevertheless, TBARS (p < .001) and CK (p = .011) levels were found to be significantly higher in the kayakers and canoeists. This work suggests that despite the enhanced levels of antioxidants, athletes undergoing regular strenuous exercise exhibited more oxidative stress than sedentary controls.
Isocaloric Carbohydrate Versus Carbohydrate-Protein Ingestion and Cycling Time-Trial Performance
Authors: Toone Rebecca J. , Betts James A.
Published: August 2016

This study was designed to compare the effects of energy-matched carbohydrate (CHO) and carbohydrate-protein (CHO-PRO) supplements on cycling time-trial performance. Twelve competitive male cyclists and triathletes each completed 2 trials in a randomized and counterbalanced order that were separated by 5–10 d and applied in a double-blind manner. Participants performed a 45-min variable-intensity exercise protocol on a cycle ergometer while ingesting either a 9% CHO solution or a mixture of 6.8% CHO plus 2.2% protein in volumes providing 22 kJ/kg body mass. Participants were then asked to cycle 6 km in the shortest time possible. Blood glucose and lactate concentrations were measured every 15 min during exercise, along with measures of substrate oxidation via indirect calorimetry, heart rate, and ratings of perceived exertion. Mean time to complete the 6-km time trial was 433 ± 21 s in CHO trials and 438 ± 22 s in CHO-PRO trials, which represents a 0.94% (CI: 0.01, 1.86) decrement in performance with the inclusion of protein (p = .048). However, no other variable measured in this study was significantly different between trials. Reducing the quantity of CHO included in a supplement and replacing it with protein may not represent an effective nutritional strategy when the supplement is ingested during exercise. This may reflect the central ergogenic influence of exogenous CHO during such activity.
Does Hepatic Hepcidin Play an Important Role in Exercise-Associated Anemia in Rats?
Authors: Liu Yu-Qian , Chang Yan-Zhong , Zhao Bin , Wang Hai-Tao , Duan Xiang-Lin
Published: August 2016

Some athletes are diagnosed as suffering from sports anemia because of iron deficiency, but the regulatory mechanism remains poorly understood. It is reported that hepcidin may provide a way to illuminate the regulatory mechanism of exercise-associated anemia. Here the authors investigate the hepcidin-involved iron absorption in exercise-associated anemia. Twelve male Wistar rats (300 ± 10 g) were randomly divided into 2 groups, 6 in a control group (CG) and 6 in an exercise group (EG, 5 wk treadmill exercise of different intensities with progressive loading). Serum samples were analyzed for circulating levels of IL-6 by means of enzyme-linked immunosorbent assay (ELISA). The expression of hepatic hepcidin mRNA was examined by real-time polymerase chain reaction analysis. The protein levels of divalent metal transporter 1 (DMT1), ferroportin1 (FPN1), and heme-carrier protein 1 (HCP1) of duodenum epithelium were examined by Western blot. The results showed that the amount of iron and ferritin in serum were lower in EG than in CG (p < .05). The levels of IL-6 and white blood cells were greater in EG than in CG (p < .01). The expression of DMT1, HCP1, and FPN1 was significantly lower in EG than in CG (p < .01). The mRNA expressions of hepatic hepcidin and hemojuvelin in skeletal muscle were remarkably higher in EG than in CG. The data indicated that inflammation was induced by strenuous exercise, and as a result, the transcriptional level of the hepatic hepcidin gene was increased, which further inhibited the expression of iron-absorption proteins and led to exercise-associated anemia.
Elite Adolescent Athletes’ Use of Dietary Supplements: Characteristics, Opinions, and Sources of Supply and Information
Authors: Diehl Katharina , Thiel Ansgar , Zipfel Stephan , Mayer Jochen , Schnell Alexia , Schneider Sven
Published: August 2016

The authors’ aim was to examine the prevalence of (daily) dietary-supplement (DS) use among elite adolescent athletes and to differentiate use by different types of DS according to their function. Data were analyzed for associations between users of these DS types, sociodemographic, sport-specific characteristics, and opinion on the need for DS. In addition, sources of supply and information were examined. In the framework of the GOAL Study, 1,138 German elite adolescent athletes (14–18 yr) answered questions about DS. The data were analyzed to identify groups at risk for using DS after a classification by supplemental function. Of the young athletes, 91.1% reported DS use during the previous month. (Daily) DS use was significantly associated with sex, kind of sport, and the weekly duration of sporting activity. Furthermore, some athletes were required to use DS by their sporting organization. DS use was more likely in these athletes than in those whose sporting organizations had no such requirement. Overall, DS with short- and long-term supplemental function were mostly associated with the use of magnesium. However, DS with medium-term muscle-building function played an important role among daily users. The main source of information about DS was coaches; main source of supply was parents. Professional education is urgently needed, as 9 out of 10 athletes used DS, and strong positive opinions toward the use of DS were present, particularly in the DS users.
Environmental Temperature and Exercise-Induced Blood Oxidative Stress
Authors: Quindry John , Miller Lindsey , McGinnis Graham , Kliszczewiscz Brian , Slivka Dustin , Dumke Charles , Cuddy John , Ruby Brent
Published: August 2016

Previous research findings indicate that environmental temperature can influence exercise-induced oxidative-stress responses, although the response to variable temperatures is unknown. The purpose of this study was to investigate the effect of warm, cold, and “neutral,” or room, environmental temperatures on the blood oxidative stress associated with exercise and recovery. Participants (N = 12, age 27 ± 5 yr, VO2max = 56.7 ± 5.8 ml · kg-1 · min-1, maximal cycle power output = 300 ± 39 W) completed 3 exercise sessions consisting of a 1-hr ride at 60% Wmax, at 40% relative humidity in warm (33 °C), cold (7 °C), and room-temperature environments (20 °C) in a randomized crossover fashion. Rectal core temperature was monitored continually as participants remained in the respective trial temperature throughout a 3-hr recovery. Blood was collected preexercise and immediately, 1 hr, and 3 hr postexercise and analyzed for oxidative-stress markers including ferric-reducing ability of plasma (FRAP), Trolox-equivalent antioxidant capacity (TEAC), lipid hydroperoxides, and protein carbonyls. Core temperature was significantly elevated by all exercise trials, but recovery core temperatures reflected the given environment. FRAP (p < .001), TEAC (p < .001), and lipid hydroperoxides (p < .001) were elevated after warm exercise while protein carbonyls were not altered (p > .05). These findings indicate that moderate-intensity exercise and associated recovery in a warm environment elicits a blood oxidative-stress response not observed at comparable exercise performed at lower temperatures.
Increase in Skeletal-Muscle Glycogenolysis and Perceived Exertion With Progressive Dehydration During Cycling in Hydrated Men
Authors: Logan-Sprenger Heather M. , Heigenhauser George J. F. , Jones Graham L. , Spriet Lawrence L.
Published: August 2016

This study investigated the effects of progressive mild dehydration during cycling on whole-body substrate oxidation and skeletal-muscle metabolism in recreationally active men. Subjects (N = 9) cycled for 120 min at ~65% peak oxygen uptake (VO2peak 22.7 °C, 32% relative humidity) with water to replace sweat losses (HYD) or without fluid (DEH). Blood samples were taken at rest and every 20 min, and muscle biopsies were taken at rest and at 40, 80, and 120 min of exercise. Subjects lost 0.8%, 1.8%, and 2.7% body mass (BM) after 40, 80, and 120 min of cycling in the DEH trial while sweat loss was not significantly different between trials. Heart rate was greater in the DEH trial from 60 to 120 min, and core temperature was greater from 75 to 120 min. Rating of perceived exertion was higher in the DEH trial from 30 to 120 min. There were no differences in VO2, respiratory-exchange ratio, total carbohydrate (CHO) oxidation (HYD 312 ± 9 vs. DEH 307 ± 10 g), or sweat rate between trials. Blood lactate was significantly greater in the DEH trial from 20 to 120 min with no difference in plasma free fatty acids or epinephrine. Glycogenolysis was significantly greater (24%) over the entire DEH vs. HYD trial (433 ± 44 vs. 349 ± 27 mmol · kg−1 · dm−1). In conclusion, dehydration of <2% BM elevated physiological parameters and perceived exertion, as well as muscle glycogenolysis, during exercise without affecting whole-body CHO oxidation.
Case Study: Beverage Temperature at Aid Stations in Ironman Triathlon
Authors: Burdon Catriona A. , Johnson Nathan A. , Chapman Phillip G. , Muhamed Ahmad Munir Che , O’Connor Helen T.
Published: August 2016

Purpose:

The aim of this study was to measure the effect of environmental conditions and aid-station beverage-cooling practices on the temperature of competitor beverages.

Methods:

Environmental and beverage temperatures were measured at three cycling and two run course aid stations at the 2010 Langkawi, Malaysia (MA), and Port Macquarie, Australia (AU), Ironman triathlon events. To measure the specific effect of radiant temperature, additional fluid-filled (600 ml) drink bottles (n = 12) were cooled overnight (C) and then placed in direct sun (n = 6) or shade (n = 6) near to a cycle aid station at AU.

Results:

During both events, beverage temperature increased over time (p < .05) as environmental conditions, particularly radiant temperature increased (p < .05). Mean beverage temperature ranged between 14–26°C and during both events was above the palatable range (15–22°C) for extended periods. At AU, bottles placed in direct sunlight heated faster (6.9 ± 2.3 °C·h−1) than those in the shade (4.8 ± 1.1°C·h−1, p = .05).

Conclusion:

Simple changes to Ironman aidstation practices, including shade and chilling beverages with ice, result in the provision of cooler beverages. Future studies should investigate whether provision of cool beverages at prolonged endurance events influences heat-illness incidence, beverage-consumption patterns, and competitor performance.
Vitamin D Status and Supplementation in Elite Irish Athletes
Authors: Magee Pamela J. , Pourshahidi L. Kirsty , Wallace Julie M. W. , Cleary John , Conway Joe , Harney Edward , Madigan Sharon M.
Published: August 2016

Background:

A high prevalence of vitamin D insufficiency/deficiency, which may impact on health and training ability, is evident among athletes worldwide. This observational study investigated the vitamin D status of elite Irish athletes and determined the effect of wintertime supplementation on status.

Methods:

Serum 25-hydroxyvitamin D [25(OH)D], calcium, and plasma parathyroid hormone were analyzed in elite athletes in November 2010 (17 boxers, 33 paralympians) or March 2011 (34 Gaelic Athletic Association [GAA] players). A subset of boxers and paralympians (n = 27) were supplemented during the winter months with either 5,000 IU vitamin D3/d for 10–12 weeks or 50,000 IU on one or two occasions. Biochemical analysis was repeated following supplementation.

Results:

Median 25(OH)D of all athletes at baseline was 48.4 nmol/L. Vitamin D insufficiency/deficiency (serum 25(OH)D <50 nmol/L) was particularly evident among GAA players (94%) due to month of sampling. Wintertime supplementation (all doses) significantly increased 25(OH)D (median 62.8 nmol/L at baseline vs. 71.1 nmol/L in April or May; p = .001) and corrected any insufficiencies/deficiencies in this subset of athletes. In contrast, 25(OH)D significantly decreased in those that did not receive a vitamin D supplement, with 74% of athletes classed as vitamin D insufficient/deficient after winter, compared with only 35% at baseline.

Conclusions:

This study has highlighted a high prevalence of vitamin D insufficiency/deficiency among elite Irish athletes and demonstrated that wintertime vitamin D3 supplementation is an appropriate regimen to ensure vitamin D sufficiency in athletes during winter and early spring.
Positional Performance Profiling of Elite Ice Hockey Players
Authors: Vescovi Jason D. , Murray Teena M. , VanHeest Jaci L.
Published: August 2016

Purpose:

The primary purpose of this study was to determine whether positional profiling is possible for elite ice hockey players by examining anthropometric characteristics and physiological performance. In addition, performance ranges and percentiles were determined for each position (forwards, defensemen, and goalkeepers) on all dependent variables.

Methods:

A retrospective, cross-sectional study design was used with performance data from ice hockey players (mean age = 18.0 ± 0.6 years) attending the 2001 (n = 74), 2002 (n = 84), and 2003 (n = 92) Combines. Four anthropometric characteristics and 12 performance tests were the dependent variables. A 3 × 3 (position × year) 2-way ANOVA was used to determine whether any significant interactions were present. No significant interactions were observed, so the data were collapsed over the 3-year period and positional characteristics were analyzed using a 1-way ANOVA.

Results:

Defenders were heavier and/or taller compared with the other 2 positions (P ≤ .01), whereas goalkeepers showed greater body-fat percentage compared with that of forwards (P = .001). It was found that goalkeepers had significantly lower strength measures for the upper body (P ≤ .043) and lower anaerobic capacity (P ≤ .039) values compared with at least one other position, but they had greater flexibility (P ≤ .013). No positional differences were observed for the broad jump, vertical jump, aerobic power, or curl-ups.

Conclusion:

The current findings provide evidence supporting the use of anthropometric measurements, upper body strength, and anaerobic capacity to effectively distinguish among positions for elite-level ice hockey players.
Off-Ice Performance and Draft Status of Elite Ice Hockey Players
Authors: Vescovi Jason D. , Murray Teena M. , Fiala Kelly A. , VanHeest Jaci L.
Published: August 2016

Purpose:

The primary purpose of this study was to determine whether tests performed at the National Hockey League (NHL) Combine could distinguish draft status (ie, the round selected). A secondary aim was to provide performance ranges and percentiles for each of the dependent variables.

Methods:

A retrospective, cross-sectional study design was used with performance data and draft order from 2001, 2002, and 2003 Combine participants. Draft round was divided into 5 classifications (rounds 1, 2, 3, 4, and 5 through 9), and performances on 12 physical tests served as dependent variables. Three multiple analyses of covariance (MANCOVAs) were used to determine the significance of performance scores at the NHL Combine on draft selection. Age (years), body mass (kg), height (cm), and percentage body fat were treated as covariates.

Results:

Overall, MANCOVA results indicated no significant effect of performance on draft selection for 2001, 2002, or 2003. Subsequent univariate tests revealed that no single dependent variable was able to distinguish between draft rounds for any of the 3 years sampled.

Conclusions:

Using draft status as an indicator of ice hockey performance, it appears that off-ice tests cannot accurately predict ice hockey playing ability in an elite group of athletes. This might stem from homogeneity of the Combine participants, a lack of validity of the tests, or other factors (eg, on-ice hockey skills, psychological variables, etc) that play a role in draft selection.
Using Mathematical Modeling in Training Planning
Authors: Busso Thierry , Thomas Luc
Published: August 2016

This report aims to discuss the strengths and weaknesses of the application of systems modeling to analyze the effects of training on performance. The simplifications inherent to the modeling approach are outlined to question the relevance of the models to predict athletes’ responses to training. These simplifications include the selection of the variables assigned to the system’s input and output, the specification of model structure, the collection of data to estimate the model parameters, and the use of identified models and parameters to predict responses. Despite the gain in insight to understand the effects of an intensification or reduction of training, the existing models would not be accurate enough to make predictions for a particular athlete in order to monitor his or her training.
Diurnal Variation in Swim Performance Remains, Irrespective of Training Once or Twice Daily
Authors: Martin Louise , Nevill Alan M. , Thompson Kevin G.
Published: August 2016

Purpose:

Fast swim times in morning rounds are essential to ensure qualification in evening finals. A significant time-of-day effect in swimming performance has consistently been observed, although physical activity early in the day has been postulated to reduce this effect. The aim of this study was to compare intradaily variation in race-pace performance of swimmers routinely undertaking morning and evening training (MEG) with those routinely undertaking evening training only (EOG).

Methods:

Each group consisted of 8 swimmers (mean ± SD: age = 15.2 ± 1.0 and 15.4 ± 1.4 y, 200-m freestyle time 132.8 ± 8.4 and 136.3 ± 9.1 s) who completed morning and evening trials in a randomized order with 48 h in between on 2 separate occasions. Oral temperature, heart rate, and blood lactate were assessed at rest, after a warm-up, after a 150-m race-pace swim, and after a 100-m time trial. Stroke rate, stroke count, and time were recorded for each length of the 150-m and 100-m swims.

Results:

Both training groups recorded significantly slower morning 100-m performances (MEG = +1.7 s, EOG = +1.4 s; P < .05) along with persistently lower morning temperatures that on average were –0.47°C and –0.60°C, respectively (P < .05). No differences were found in blood-lactate, heart-rate, and stroke-count responses (P > .05). All results were found to be reproducible (P > .05).

Conclusions:

The long-term use of morning training does not appear to significantly reduce intradaily variation in race-pace swimming or body temperature.
Acute Effects of Soccer Training on White Blood Cell Count in Elite Female Players
Authors: Avloniti Alexandra A. , Douda Helen T. , Tokmakidis Savvas P. , Kortsaris Alexandros H. , Papadopoulou Evropi G. , Spanoudakis Emmanouil G.
Published: August 2016

Purpose:

To investigate the acute changes in leukocyte number and cortisol after a single bout of soccer training.

Methods:

Ten elite female national-team soccer players and 8 nonathletes participated in the study. The duration of the exercise was 2 h, and it was performed at an intensity of 75% of maximal heart rate (HRmax). Blood samples were taken before, immediately after, and 4 h after a soccer training session to determine total white blood cells; the subsets of neutrophils, lymphocytes, monocytes, eosinophils, and basophils; and cortisol. At the same time, blood samples were obtained from nonathletes who refrained from exercise.

Results:

Data analysis indicated a significant increase in total white blood cells in the athletes postexercise (P < .001). The leukocytosis was still evident after 4 h of recovery (78% higher than the preexercise values), and there was a significant difference between athletes and nonathletes (P < .001). This leukocytosis was primarily caused by neutrophilia—there were no significant differences in lymphocytes after the end of exercise or between the 2 groups (P > 0.05). In addition, there was a statistically significant difference in cortisol concentration between athletes and nonathletes after the exercise (P < .001).

Conclusion:

These findings revealed that the single bout of soccer training at an intensity of 75% of HRmax induced leukocytosis without affecting the lymphocyte count in elite female athletes and probably the effectiveness of cellular components of adaptive immunity. Coaches should provide adequate time (>4 h) until the next exercise session.
Power and Power Potentiation Among Strength–Power Athletes: Preliminary Study
Authors: Stone Michael H. , Sands William A. , Pierce Kyle C. , Ramsey Michael W. , Haff G. Gregory
Published: August 2016

Purpose:

To assess the effects of manipulating the loading of successive sets of midthigh clean pulls on the potentiation capabilities of 7 international-level US weightlifters (4 men, 3 women).

Methods:

Isometric and dynamic peak-force characteristics were measured with a force plate at 500 Hz. Velocity during dynamic pulls was measured using 2 potentiometers that were suspended from the top of the right and left sides of the testing system and attached to both ends of the bar. Five dynamic-performance trials were used (in the following order) as the potentiation protocol: women at 60, 80, 100, 120, and 80 kg and men at 60, 140, 180, 220, and 140 kg. Trials 2 vs 5 were specifically analyzed to assess potentiation capabilities. Isometric midthigh pulls were assessed for peak force and rate of force development. Dynamic lifts were assessed for peak force (PF), peak velocity (PV), peak power (PP), and rate of force development (RFD).

Results:

Although all values (PF, PV, PP, and RFD) were higher postpotentiation, the only statistically higher value was found for PV (ICCα = .95, P = .011, η2 = .69).

Conclusions:

Results suggest that manipulating set-loading configuration can result in a potentiation effect when heavily loaded sets are followed by a lighter set. This potentiation effect was primarily characterized by an increase in the PV in elite weightlifters.
The Optimal Downhill Slope for Acute Overspeed Running
Authors: Ebben William P.
Published: August 2016

Purpose:

This study evaluated a variety of downhill slopes in an effort to determine the optimal slope for overspeed running.

Methods:

Thirteen NCAA Division III college athletes who participated in soccer, track, and football ran 40-yd (36.6-m) sprints, on downhill slopes of 2.1°, 3.3°, 4.7°, 5.8°, and 6.9° in random order. All sprints were timed using the Brower Timing System Speedtrap II. Data were analyzed with SSPS 15.0. A 1-way repeated-measures analysis of variance revealed significant main effects for the test slopes (P = .000). Bonferroni-adjusted pairwise comparisons determined that there were a number of differences between the hill slopes.

Results:

Analysis reveals that 40-yd sprints performed on hill slopes of approximately 5.8° were optimal compared with flatland running and the other slopes assessed (P < .05). Sprinting on a 5.8° slope increased the subjects’ maximal speed by an average of 0.35 s, resulting in a 6.5% ± 4.0% decrease in 40-yd sprint time compared with fatland running. Compared with the 4.7° slope, the 5.8° slope yielded a 0.10-s faster 40-yd sprint time, resulting in a 1.9% increase in speed.

Conclusions:

Those who train athletes for speed should use or develop overspeed hills with slopes of approximately 5.8° to maximize acute sprinting speed. The results of this study bring into question previous recommendations to use hills of 3° downhill slope for this form of overspeed training.
Prediction of Flatwater Kayaking Performance
Authors: van Someren Ken A. , Howatson Glyn
Published: August 2016

Purpose:

To determine the relative importance of anthropometric and physiological attributes for performance in the 1000-m, 500-m, and 200-m flatwater kayaking events.

Methods:

Eighteen competitive male kayakers completed performance trials over the 3 distances and a battery of anthropometric and physiological tests.

Results:

Performance times (mean ± SD) for 1000 m, 500 m, and 200 m were 262.56 ± 36.44 s, 122.10 ± 5.74 s, and 41.59 ± 2.12 s, respectively. Performance in all 3 events was correlated with a number of physiological parameters; in addition, 500-m and 200-m performance was correlated with upper body dimensions. 1000-m time was predicted by power output at lactate turnpoint expressed as a percentage of maximal aerobic power, work done in a 30-s ergometry test and work done in a 2-min ergometry test (adjusted R2 = 0.71, SEE = 5.72 s); 500-m time was predicted by work done and the fatigue index in a 30-s ergometry test, work done in a 2-min ergometry test, peak isometric and isokinetic function (adjusted R2 = 0.79, SEE = 2.49 s); 200-m time was predicted by chest circumference, humeral breadth, peak power, work done, and the fatigue index in a 30-s ergometry test (adjusted R2 = 0.71, SEE = 0.71 s).

Conclusions:

A number of physiological variables are correlated with performance in all events. 1000-m, 500-m, and 200-m times were predicted with a standard error of only 2.2%, 2.0%, and 1.7%, respectively.
Effects of Arms-Only Swimming Training on Performance, Movement Economy, and Aerobic Power
Authors: Konstantaki Maria , Winter Edward , Swaine Ian
Published: August 2016

Context:

Forward propulsion in freestyle swimming is predominantly achieved through arm action. Few studies have assessed the effects of arm training on arm power and swimming performance, yet there have not been any investigations on the effects of arms-only swimming training on swimming performance and physiological responses to arm exercise.

Purpose:

To investigate the changes in arms-only and full-stroke swimming performance, movement economy and aerobic power after an arms-only swimming training program.

Methods:

Fifteen male county level swimmers were assigned either to an experimental (ES, n = 8) or control group (CS, n = 7). For six weeks ES performed arms-only freestyle swimming exercises for 20% of their weekly training distance three times per week, whereas CS performed their usual swimming training. Before and after the training program, both groups performed a) two time trials, 186 m using arms-only (186ARMS) and 372 m using full-stroke (372FULL) freestyle swimming, and b) an incremental arm-pulling exercise test. The time to complete the trials was recorded. Peak oxygen uptake (VO2peak), peak exercise intensity (EIpeak) submaximal oxygen uptake at 60 W (VO2−60) and exercise intensity at ventilatory threshold (VTW) were determined from the exercise test.

Results:

After training, ES had improved in 186ARMS (−14.2 ± 3.6%, P = .03), VO2−60 (−22.5 ± 2.3%, P = .04), EIpeak (+17.8 ± 4.2%, P = .03), and VTW (+18.9 ± 2.3%, P = .02), but not in VO2peak (P = .09) or in 372FULL (P = .07). None of the measures changed in CS (P > .05).

Conclusion:

Arms-only swimming training at 20% of the weekly training distance is an effective method to improve arm conditioning during the preparatory phase of the annual training cycle.
Neuromuscular and Endocrine Responses of Elite Players to an Australian Rules Football Match
Authors: Cormack Stuart J. , Newton Robert U. , McGuigan Michael R.
Published: August 2016

Purpose:

To examine the acute and short-term responses of variables obtained during a single countermovement jump (CMJ1); repeated countermovement jump involving 5 consecutive efforts without a pause (CMJ5); and cortisol, testosterone, and testos-terone-to-cortisol ratio (T:C) to an elite Australian Rules Football (ARF) match with a view to determining which variables may be most useful for ongoing monitoring.

Methods:

Twenty-two elite ARF players participating in a preseason cup match performed a CMJ1 and a CMJ5 and provided saliva samples 48 h before the match (48pre), prematch (Pre), postmatch, 24 h post (24post), 72 h post (72post), 96 h post (96post), and 120 h post (120post). The magnitude of change in variables at each time point compared with Pre and 48pre was analyzed using the effect size (ES) statistic.

Results:

A substantial decrement in the pre- to postmatch comparison occurred in the ratio of CMJ1 Flight time:Contraction time (ES −0.65 ± 0.28). Cortisol (ES 2.34 ± 1.06) and T:C (ES −0.52 ± 0.42) displayed large pre- to postmatch changes. The response of countermovement variables at 24post and beyond compared with pre-match and 48pre was varied, with only CMJ1 Flight time:Contraction time displaying a substantial decrease (ES −0.32 ± 0.26) postmatch compared with 48pre. Cortisol displayed a clear pattern of response with substantial elevations up to 24post compared with Pre and 48pre.

Conclusion:

CMJ1 Flight time:Contraction time appears to be the most useful variable for monitoring neuromuscular status in elite ARF players due to its substantial change compared with 48pre and prematch. Monitoring cortisol, due to its predictable pattern of response, may provide a useful measure of hormonal status.
Athletic Performance and the Oral Contraceptive
Authors: Rechichi Claire , Dawson Brian , Goodman Carmel
Published: August 2016

Some reports suggest variation in physiological responses and athletic performance, for female athletes at specific phases of the menstrual cycle. However, inconsistent findings are common due to the inappropriate verification of menstrual cycle phase, small subject numbers, high intra- and interindividual variability in estrogen and progesterone concentration, and the pulsatile secretion of these hormones. Therefore, the oral contraceptive (OC) cycle may provide a more stable environment in which to evaluate the acute effect of reproductive hormones on physiological variables and exercise performance. To date, most of the OC research has compared differences between OC use and nonuse, and few researchers have examined within-cycle effects of the OC. It is also apparent that OC use is becoming far more prevalent in athletes; hence the effect of the different exogenous and endogenous hormonal profiles on athletic performance should be investigated. Research to date identifies potential for variation in aerobic performance, anaerobic capacity, anaerobic power and reactive strength throughout an OC cycle. The purpose of this review is to present and evaluate the current literature on the physiology of exercise and athletic performance during the OC cycle.
Gender Comparison of Physiologic and Perceptual Responses in Recreational Marathon Runners
Authors: Loftin Mark , Sothern Melinda , Tuuri Georgianna , Tompkins Connie , Koss Cathie , Bonis Marc
Published: August 2016

Purpose:

The aim of this investigation was to compare gender differences in physiologic and perceptual responses during a 1-h run at recent marathon pace and running economy at three speeds in recreational marathon runners.

Methods:

In a counterbalanced design, 10 men and 10 women completed a 1-h treadmill run and a running economy test. Treadmill speed for the 1-h run ranged from 141 to 241 m·min−1 and 134, 168, and 188 m·min−1 for running economy. Physiologic parameters (oxygen uptake, carbon dioxide production, pulmonary ventilation, and heart rate) and perceived exertion were measured. Repeated-measures ANOVA was used to compare any gender differences (P < .05) during the 1-h run and a two-way ANOVA was used to compare running economy. With this sample, estimated marathon energy expenditure, body composition, and maximal physiologic function was reported.1

Results:

With the exception of an allometric expression of VO2 (mL·min−1·kg BW−0.75), similar gender physiologic and perceptual responses were found during the 1-h run. Although not significant, the females exercised at a higher percent VO2max (8% to 9%) during the run. Similar gender differences were also noted during the running economy tests.

Conclusions:

Although the male runners completed a recent marathon significantly faster than the females, similar gender physiologic and perceptual responses were generally found during the 1-h treadmill run and the running economy tests.
Laterality of Hand Grip and Elbow Flexion Power in Right Hand–Dominant Individuals
Authors: Aoki Hiroki , Demura Shinichi
Published: August 2016

Purpose:

This study aimed to compare the laterality, and its gender difference, of hand grip and elbow flexion power according to load in right hand–dominant individuals.

Results:

The subjects were 15 healthy young males (age 22.1 ± 0.7 y, height 171.3 ± 3.4 cm, mass 64.5 ± 4.1 kg) and 15 healthy young females (age 22.4 ± 1.0 y, height 161.1 ± 3.0 cm, mass 55.4 ± 4.6 kg). Isotonic peak power was measured with 6 different loads ranging from 20% to 70% of maximum voluntary contraction (MVC) for grip and elbow flexion movements.

Results:

The peak power was significantly larger in males than in females in both movements (ratio, males:females was 58.1:49.4%). The dominant right hand had larger peak power in all loads for hand grip power (ratio, dominant:nondominant was 83.6:71.1%) and in loads of 20% to 50% MVC for elbow flexion power (88.7:85.7%) in both genders, confirming laterality in both movements. The peak power ratio of the dominant right hand to the nondomi-nant left hand was significantly larger in hand grip than in elbow flexion for all loads in females.

Conclusion:

Even though laterality was confirmed in both grip and elbow flexion, gender difference is more marked in hand grip.
Measuring Circadian Advantage in Major League Baseball: A 10-Year Retrospective Study
Authors: Winter W. Christopher , Hammond William R. , Green Noah H. , Zhang Zhiyong , Bliwise Donald L.
Published: August 2016

Purpose:

The effect of travel on athletic performance has been investigated in previous studies. The purpose of this study was to investigate this effect on game outcome over 10 Major League Baseball (MLB) seasons.

Methods:

Using the convention that for every time zone crossed, synchronization requires 1 d, teams were assigned a daily number indicating the number of days away from circadian resynchronization. With these values, wins and losses for all games could be analyzed based on circadian values.

Results:

19,079 of the 24,121 games (79.1%) were played between teams at an equal circadian time. The remaining 5,042 games consisted of teams playing at different circadian times. The team with the circadian advantage won 2,620 games (52.0%, P = .005), a winning percentage that exceeded chance but was a smaller effect than home field advantage (53.7%, P < .0001). When teams held a 1-h circadian advantage, winning percentage was 51.7% (1,903–1,781). Winning percentage with a 2-h advantage was 51.8% (620–578) but increased to 60.6% (97–63) with a 3-h advantage (3-h advantage > 2-hadvantage = 1-h advantage, P = .036). Direction of advantage showed teams traveling from Western time zones to Eastern time zones were more likely to win (winning percentage = .530) than teams traveling from Eastern time zones to Western time zones (winning percentage = .509) with a winning odds 1.14 (P = .027).

Conclusion:

These results suggest that in the same way home field advantage influences likelihood of success, so too does the magnitude and direction of circadian advantage. Teams with greater circadian advantage were more likely to win.
Nocturnal Heart Rate Variability Following Supramaximal Intermittent Exercise
Authors: Hani Al Haddad , Laursen Paul B. , Said Ahmaidi , Martin Buchheit
Published: August 2016

Purpose:

To assess the effect of supramaximal intermittent exercise on long-term cardiac autonomic activity, inferred from heart rate variability (HRV).

Methods:

Eleven healthy males performed a series of two consecutive intermittent 15-s runs at 95% VIFT (i.e., speed reached at the end of the 30-15 Intermittent Fitness Test) interspersed with 15 s of active recovery at 45% VIFT until exhaustion. Beat-to-beat intervals were recorded during two consecutive nights (habituation night and 1st night) before, 10 min before and immediately after exercise, as well as 12 h (2nd night) and 36 h (3rd night) after supramaximal intermittent exercise. The HRV indices were calculated from the last 5 min of resting and recovery periods, and the first 10 min of the first estimated slow wave sleep period.

Results:

Immediate post-supramaximal exercise vagal-related HRV indices were significantly lower than immediate pre-supramaximal exercise values (P < .001). Most vagal-related indices were lower during the 2nd night compared with the 1st night (eg, mean RR intervals, P = .03). Compared with the 2nd night, vagal-related HRV indices were significantly higher during the 3rd night. Variables were not different between the 1st and 3rd nights; however, we noted a tendency (adjusted effect size, aES) for an increased normalized high-frequency component (P = .06 and aES = 0.70) and a tendency toward a decreased low-frequency component (P = .06 and aES = 0.74).

Conclusion:

Results confirm the strong influence of exercise intensity on short- and long-term post exercise heart rate variability recovery and might help explain the high efficiency of supramaximal training for enhancing indices of cardiorespiratory fitness.
Acute Carbohydrate Ingestion Affects Lactate Response in Highly Trained Swimmers
Authors: Millard-Stafford Melinda L. , Brown Mary Beth , Snow Teresa K.
Published: August 2016

Purpose:

Effects of acute carbohydrate ingestion on blood lactate (BLa) response to graded exercise was examined in highly trained male and female swimmers.

Methods:

Twenty-three swimmers performed the United States Swimming Lactate Protocol, a graded interval test (5 × 200 on 5 min), following ingestion of carbohydrate sports drink (CHO) and placebo (PLA).

Results:

There was no difference in heart rate (P = .55), swim velocity (P = .95), or ratings of perceived exertion (P = .58) between beverages. There was a signifcant main effect for gender (P = .002) on BLa during all swim stages and recovery. In females, BLa was 27% to 50% higher for CHO during the first (P = .009) and second (P = .04) swim stages. Predicted BLa at selected swim velocity was higher (P = .048) for CHO versus PLA in females at 1.27 m·s−1 and higher (P < .02) for men at 1.4 m·s−1. Mean (±SD) BLa was significantly (P = .004) greater for CHO (2.7 ± 1.2) compared with PLA (2.0 ± 1.1 mmol·L−1) during the second test stage and when normalized relative to velocity (P = .004). Peak BLa after the final swim (9.6 ± 3.1 vs. 9.0 ± 3.2 mmol·L−1, P = .36) was not different between CHO and PLA.

Conclusions:

Acute CHO ingestion alters the BLa: swim velocity relationship during moderate intensity swims of an incremental swim test, particularly for females. Therefore, pretest beverage ingestion should be standardized during the administration of BLa testing to prevent potential erroneous interpretations regarding athlete’s training status.
The Science of Sex Verification and Athletic Performance
Authors: Tucker Ross , Collins Malcolm
Published: August 2016

The division of athletes into male and female categories for competition is a widely accepted practice and is ordinarily straightforward, requiring no intervention from authorities. However, for reasons ranging from deliberate cheating to complex medical conditions resulting in ambiguous development of sex organs, the controversy of sex verification in athletic events has existed for 70 years. Testing procedures, initially implemented to prevent cheating by men masquerading as women, have produced humiliating outcomes for women athletes who were often for the first time confronted with the possibility that they have one of the disorders of sex development. Sporting authorities have and continue to formulate position stands for the management of such cases. An important missing component in this debate is the sound scientific evidence to determine (a) whether a performance advantage actually exists and (b) how large it might be. The division of competition into separate categories and the large difference in sporting performance between male and female necessitate that sport-governing bodies define the boundaries between the sexes in a just and fair manner for all participating athletes. This review will therefore provide the historical context of the debate and aim to discuss relevant physiological and performance aspects of the sex verification process.