bluuebunny/crossref_metadata_2025 huggingface dataset:
Food Sources of Calcium in a Sample of African-American and Euro-American Collegiate Athletes
Authors: Slawson Deborah Leachman , McClanahan Barbara S. , Clemens Linda H. , Ward Kenneth D. , Klesges Robert C. , Vukadinovich Christopher M. , Cantler Edwin D.
Published: August 2016

Adequate calcium intake is integral to bone health as well as for optimal athletic performance. This study was conducted to investigate: (a) food sources of calcium in a sample of collegiate athletes, (b) gender and/or ethnic differences in food sources of calcium, and (c) whether athletes that derive less of their calcium intake from dairy sources increase their calcium intake from supplements or other food sources. Participants were African-American and Euro-American NCAA Division 1-A athletes. Eighty-five men and 59 women participated. Calcium intake for the previous 7-day period was assessed with a brief calcium screen.

Men consumed significantly more calcium than women (1,354 vs. 898 mg/day), with female cross-country runners exhibiting the lowest average intake (605 mg/day). Both men and women obtained the majority of their calcium from dairy products and mixed dishes, while men consumed significantly more calcium-fortified foods. Several gender and ethnic interactions for calcium intake from food groups were found. Mean total dairy calcium intake was found to vary according to total calcium intake in men, and supplemental calcium was not used to augment low dairy intakes of calcium in any group.

While African-Americans and Euro-Americans athletes were consuming similar levels of calcium, the female athletes in the sample did not get adequate amounts.
Metabolic Response to Provision of Mixed Protein-Carbohydrate Supplementation during Endurance Exercise
Authors: Miller Sharon L. , Maresh Carl M. , Armstrong Lawrence E. , Ebbeling Cara B. , Lennon Shannon , Rodriguez Nancy R.
Published: August 2016

The interaction of substrates and hormones in response to ingestion of intact proteins during endurance exercise is unknown. This study characterized substrate and hormone responses to supplementation during endurance exercise. Nine male runners participated in 3 trials in which a non-fat (MILK), carbohydrate (CHO), or placebo (PLA) drink was consumed during a 2-hour treadmill >· run at 65% V̇O2max. Circulating levels of insulin, glucagon, epinephrine, norepi-nephrine, growth hormone, testosterone, and cortisol were measured. Plasma substrates included glucose, lactate, free fatty acids, and select amino acids. Except for insulin and cortisol, hormones increased with exercise. While post-exercise insulin concentrations declined similarly in all 3 trials, the glucagon increase was greatest following MILK consumption. CHO blunted the post-exercise increase in growth hormone compared to levels in MILK. Free fatty acids and plasma amino acids also were responsive to nutritional supplementation with both CHO and MILK attenuating the rise in free fatty acids compared to the increase observed in PLA. Correspondingly, respiratory exchange ratio increased during CHO. Essential amino acids increased significantly only after MILK and were either unchanged or decreased in CHO. PLA was characterized by a decrease in branched-chain amino acid concentrations. Modest nutritional supplementation in this study altered the endocrine response as well as substrate availability and utilization following and during an endurance run, respectively.
Food Preferences, Dieting Behaviors, and Body Image Perceptions of Elite Figure Skaters
Authors: Jonnalagadda Satya S. , Ziegler Paula J. , Nelson Judy A.
Published: August 2016

The objectives of this study were to determine food preferences, body image perceptions, dieting behaviors, and nutrient intakes of elite male and female figure skaters. Male (n = 23) and female (n = 26) figure skaters completed a food preference checklist, a questionnaire examining their demographics, dieting behaviors and body image perceptions, and 3-d food records. Male skaters had a higher preference (score ≥ 6) for grains, fruit, meat, dairy, fats, and sweets. Female skaters had higher preference for grains and fruits. Of the female skaters, 30% considered themselves overweight and indicated a preference for a thinner body contour. Both male and female skaters expressed a preference for leaner body contours for members of the opposite gender. Total energy intake, total fat (females) and dietary fiber were below the dietary recommendations. Vitamin E, vitamin D, folate (females), pantothenic acid (females), calcium (females), magnesium, potassium, and phosphorus (females) were less than two-thirds of the dietary recommendations. Macronutrient intake of male skaters was associated with preferences for the grain group, although no association was observed among female skaters. Results suggest that these behaviors and attitudes need to be assessed and addressed among figure skaters, given their impact on dietary intakes and overall well-being.
Physiological Role of Carnosine in Contracting Muscle
Authors: Begum Gulshanara , Cunliffe Adam , Leveritt Michael
Published: August 2016

High-intensity exercise leads to reductions in muscle substrates (ATP, PCr, and glycogen) and a subsequent accumulation of metabolites (ADP, Pi, H+, and Mg2+) with a possible increase in free radical production. These factors independently and collectively have deleterious effects on muscle, with significant repercussions on high-intensity performance or training sessions. The effect of carnosine on overcoming muscle fatigue appears to be related to its ability to buffer the increased H+ concentration following high-intensity work. Carnosine, however, has other roles such as an antioxidant, a metal chelator, a Ca2+ and enzyme regulator, an inhibitor of protein glycosylation and protein-protein cross-linking. To date, only 1 study has investigated the effects of carnosine supplementation (not in pure form) on exercise performance in human subjects and found no improvement in repetitive high-intensity work. Much data has come from in vitro work on animal skeletal muscle fibers or other components of muscle contractile mechanisms. Thus further research needs to be carried out on humans to provide additional understanding on the effects of carnosine in vivo.
Water Balance and Salt Losses in Competitive Football
Authors: Maughan Ronald J. , Watson Phillip , Evans Gethin H. , Broad Nicholas , Shirreffs Susan M.
Published: August 2016

Fluid balance and sweat electrolyte losses were measured in the players and substitutes engaged in an English Premier League Reserve competitive football match played at an ambient temperature of 6–8 °C (relative humidity 50–60%). Intake of water and/or sports drink and urine output were recorded, and sweat composition was estimated from absorbent swabs applied to 4 skin sites for the duration of the game. Body mass was recorded before and after the game. Data were obtained for 22 players (age 21 y, height 180 cm, mass 78 kg) and 9 substitutes (17 y, 181 cm, 72 kg). All were male. Two of the players were dismissed during the game, and none of the substitutes played any part in the game. Mean ± SD sweat loss of players amounted to 1.68 ± 0.40 L, and mean fluid intake was 0.84 ± 0.47 L (n = 20), with no difference between teams. Corresponding values for substitutes, none of whom played in the match, were 0.40 ± 0.24 L and 0.78 ± 0.46 L (n = 9). Prematch urine osmolality was 678 ± 344 mOsm/kg: 11 of the 31 players provided samples with an osmolality of more than 900 mOsm/kg. Sweat sodium concentration was 62 ± 13 mmol/L, and total sweat sodium loss during the game was 2.4 ± 0.8 g. These descriptive data show a large individual variability in hydration status, sweat losses, and drinking behaviors in a competitive football match played in a cool environment, highlighting the need for individualized assessment of hydration status to optimize fluid-replacement strategies.
Application of Protein or Protein Hydrolysates to Improve Postexercise Recovery
Authors: van Loon Luc J.C.
Published: August 2016

Protein, protein hydrolysates, and amino acids have become popular ingredients in sports nutrition. The use of protein, protein hydrolysates, and amino acid mixtures has multiple applications when aiming to improve post exercise recovery. After exhaustive endurance-type exercise, muscle glycogen repletion is the most important factor determining the time needed to recover. Coingestion of relatively small amounts of protein and/or amino acids with carbohydrate can be used to augment postprandial insulin secretion and accelerate muscle glycogen synthesis rates. Furthermore, it has been well established that ingesting protein, protein hydrolysates, and amino acid can stimulate protein synthesis and inhibit protein breakdown and, as such, improve net muscle protein balance after resistance- or endurance-type exercise. The latter has been suggested to lead to a more effective adaptive response to each successive exercise bout. To augment net muscle protein accretion, athletes involved in resistance-type exercise generally ingest both protein and carbohydrate during post exercise recovery. However, carbohydrate ingestion after resistance-type exercise does not seem to be warranted to further stimulate muscle protein synthesis or improve whole-body protein balance when ample protein has already been ingested. Because resistance-type exercise is also associated with a substantial reduction in muscle glycogen content, it would be preferred to coingest some carbohydrate when aiming to accelerate glycogen repletion. More research is warranted to assess the impact of ingesting different proteins, protein hydrolysates, and/or amino acids on muscle protein accretion after exercise.
Methods to Standardize Dietary Intake Before Performance Testing
Authors: Jeacocke Nikki A. , Burke Louise M.
Published: August 2016

When testing is undertaken to monitor an athlete’s progress toward competition goals or the effect of an intervention on athletic outcomes, sport scientists should aim to minimize extraneous variables that influence the reliability, sensitivity, or validity of performance measurement. Dietary preparation is known to influence metabolism and exercise performance. Few studies, however, systematically investigate the outcomes of protocols that acutely control or standardize dietary intake in the hours and days before a performance trial. This review discusses the nutrients and dietary components that should be standardized before performance testing and reviews current approaches to achieving this. The replication of habitual diet or dietary practices, using tools such as food diaries or dietary recalls to aid compliance and monitoring, is a common strategy, and the use of education aids to help athletes achieve dietary targets offers a similarly low burden on the researcher. However, examination of dietary intake from real-life examples of these protocols reveals large variability between and within participants. Providing participants with prepackaged diets reduces this variability but can increase the burden on participants, as well as the researcher. Until studies can better quantify the effect of different protocols of dietary standardization on performance testing, sport scientists can only use a crude cost–benefit analysis to choose the protocols they implement. At the least, study reports should provide a more comprehensive description of the dietary-standardization protocols used in the research and the effect of these on the dietary intake of participants during the period of interest.
Carbohydrate-Electrolyte Drink Ingestion and Skill Performance During and After 2 hr of Indoor Tennis Match Play
Authors: McRae Kirsty A. , Galloway Stuart D.R.
Published: August 2016

Twenty-two tennis players were individually studied on 2 occasions. They performed a prematch skill test, a 2-hr tennis match against an equally ranked opponent, and a postmatch skill test. A carbohydrate-electrolyte (CHO-E; Lucozade Sport) or flavor-matched placebo-electrolyte (PL) beverage was administered in a double-blind fashion. During the trials, heart-rate and movement intensity were monitored, and the match was recorded for performance analysis. There were no differences in skill-test scores pre- to postmatch or between trials (154 ± 38 pre- and 160 ± 35 postmatch on PL, 155 ± 36 pre- and 165 ± 33 postmatch on CHO-E). CHO-E ingestion elevated blood glucose concentration throughout the match, and participants reported feeling more energetic (general activation) and more tense (high activation) 1 hr into the match than at baseline (p < .05). Participants in the CHO-E trial spent more time in moderate-intensity activity and less time in low-intensity activity than on PL. Performance analysis revealed that CHO-E ingestion increased overall serve success (M ± SD, 68% ± 7% for CHO-E vs. 66% ± 7% for PL; p < .05) and success of first serves (65% ± 9% for CHO-E, 61% ± 7% for PL; p < .01) and serves to the advantage side (70% ± 9% for CHO-E, 66% ± 7% for PL; p < .05). Return success was greater during the second set of the match (p < .05) in the CHO-E trial. Differences in serve and return success were not associated with blood glucose response to CHO or player ability.
Gene Polymorphism in Angiotensin-I-Converting Enzyme and Physical Activity Among Normotensive Chinese
Authors: Wong Wai Pong , Zhao Yi , Koh Woon-Puay
Published: August 2016

The angiotensin-I-converting enzyme (ACE) I/D gene polymorphism has been studied for its role in determining habitual physical activity level, but there is no information from Asian populations. The objective of this study was to determine whether this ACE gene polymorphism was associated with physical activity level among Chinese in Singapore. In this cross-sectional study, 110 normotensive Chinese in Singapore, age 21–61 yr, completed the short-form version of the International Physical Activity Questionnaire and contributed buccal cell samples for genotyping of the ACE I/D gene polymorphism using polymerase chain-reaction amplification. They also provided demographic information and underwent anthropometric measurements. Physical activity level was expressed as continuous (in kcal/wk) and categorical (low, moderate, or high) data. The 3 genotypes of ACE were DD (homozygous for the deletion allele), II (homozygous for the insertion allele), and ID. Among the participants, 28.2% reported low, 49.1% moderate, and 22.7% high physical activity level. Frequencies of the genotypes were 11.8% for DD, 42.7% for ID, and 45.5% for II. ACE genotype was independently associated with physical activity level. After age, gender, and body-mass index were adjusted for, individuals with DD or ID genotypes were more likely to report insufficient or low physical activity level than those with II genotypes (odds ratio = 6.88; 95% confidence interval: 2.26, 20.94). In conclusion, the I/D polymorphism of the ACE gene is significantly associated with self-reported physical activity level in normotensive Chinese Singaporeans.
Influence of Artistic Gymnastics on Iron Nutritional Status and Exercise-Induced Hemolysis in Female Athletes
Authors: Sureira Thaiz Mattos , Amancio Olga Silverio , Braga Josefina Aparecida Pellegrini
Published: August 2016

This study evaluates the relationship between body iron losses and gains in artistic gymnastics female athletes. It shows that despite the low iron intake and exercise-induced hemolysis, iron deficiency or iron-deficiency anemia does not occur, but partial changes in the hematological profile do. The hypothesis that gymnasts’ nutritional behavior contributes to anemia, which may be aggravated by exercise-induced hemolysis, led to this cross-sectional study, conducted with 43 female artistic gymnasts 6–16 yr old. The control group was formed by 40 nontraining girls, paired by age. Hemogram, serum iron, ferritin, soluble transferrin receptor, haptoglobin, total and fractional bilirubin, Type I urine, and parasitologic and occult fecal blood tests were evaluated. The athletes presented mean hematimetric and serum iron values (p = .020) higher than those of the control group. The bilirubin result discarded any hemolytic alteration in both groups. The haptoglobin results were lower in the athlete group (p = .002), confirming the incidence of exercise-induced hemolysis. Both groups presented low iron intake. The results suggest that artistic gymnastics practice leads to exerciseinduced hemolysis and partially changes the hematological profile, although not causing iron deficiency or iron-deficiency anemia, even in the presence of low iron intake.
Case Study: Nutritional Strategies of a Cyclist With Celiac Disease During an Ultraendurance Race
Authors: Black Katherine Elizabeth , Skidmore Paula , Brown Rachel Clare
Published: August 2016

Food intolerance is becoming increasingly prevalent, and increasing numbers of athletes have celiac disease. This poses challenges as dietary recommendations for exercise are largely based on gluten-containing carbohydrate-rich foods. The K4 cycle race covers 384 km around the Coromandel Peninsula, New Zealand. Lack of sleep, darkness, and temperature variations pose a number of nutritional challenges. Limited food choices present those with celiac disease with even greater challenges. This case study describes the intakes of one such athlete during training and competing in the K4. Nutritional intakes were obtained during training using weighed-food records and during the race via dietary recall and the weighing of foods pre- and postrace. As simple substitution of gluten-containing foods for gluten-free foods leads to increased energy intake, alternatives need to be considered. During the race, insufficient energy was consumed to meet the nutritional guidelines for endurance performance. This was probably due to the nature of the course, racing conditions, the consistency of gluten-free food, and, toward the end of the race, sensory-specific satiety.
Nausea and High Serum Osmolality During a Simulated Ultraendurance Adventure Race: A Case-Control Study
Authors: Bowen Robyn L. , Adams J. Harold , Myburgh Kathryn H.
Published: August 2016

Purpose:

A 29-year-old elite adventure-race athlete presented with a 10-month history of nausea appearing during or after ultraendurance races. The athlete noted recent worsening of symptoms, including lightheadedness, dark rings under the eyes, and weakness as nausea became worse, and was unable to complete races. Possible diagnoses included dehydration or over hydration, renal damage, and gastrointestinal malfunction.

Methods:

The subject (S) and a case-control athlete (C) performed an 11-hour simulated race (field test) ending in the laboratory. Blood samples were drawn, and body mass and food and drink ingested were noted at regular intervals.

Results:

Symptoms were replicated in S, whose vomitus contained undigested solids consumed during exercise. Over 11 hours, fl uid loss was similar in S (9.6 L) and C (10.3 L), but fluid intake for S was 4.8 L versus 9.9 L for C. Body mass decreased 6% in S and 1.8% in C. S presented with elevated serum urea and creatinine before and after and elevated osmolality after the field test. A week after the fi eld test, creatinine clearance was low in S but not C (83 vs 160 mmol per 24-hour urine, respectively). S was instructed to increase fluid intake throughout the day, to match fluid lost during training, and to refrain from long races. After 2 months, his serum urea, creatinine, and osmolality were normal, and creatinine clearance improved to 133 mmol per 24-hour urine. He repeated the fi eld test and experienced no nausea.

Conclusions:

Nausea in ultraendurance athletes might be an early symptom of chronic but reversible renal strain or insensitivity to high osmolality.
Effect of Starting Cadence on Sprint-Performance Indices in Friction-Loaded Cycle Ergometry
Authors: Wright Rachel L. , Wood Dan M. , James David V.B.
Published: August 2016

The aims of the study were to investigate whether starting cadence had an effect on 10-s sprint-performance indices in friction-loaded cycle ergometry and to investigate the influence of method of power determination. In a counterbalanced order, 12 men and 12 women performed three 10-s sprints using a stationary (0 rev/min), moderate (60 rev/min), and high (120 rev/min) starting cadence Calculated performance indices were peak power, cadence at peak power, time to peak power, and work to peak power. When the uncorrected method of power determination was applied, there was a main effect for starting cadence in female participants for peak power (stationary 635 ± 183.7 W, moderate 615.4 ± 168.9 W and high 798.4 ± 120.1 W) and cadence at peak power (89.8 ± 2.3 rev/min, 87.9 ± 21.5 rev/min, and 113.1 ± 12.5 rev/min). For both the uncorrected and directly measured methods of power determination in men and women, there was a main effect for starting cadence for time to peak power and work to peak power. In women, for an uncorrected method of power determination, it can be concluded that starting cadence does affect peak power and cadence at peak power. This effect is, however, negated by a direct-measurement method of power determination. In men and women, for both uncorrected and directly measured methods o power determination, time to peak power and work to peak power were affected by starting cadence. Therefore, a higher-cadence start is unsuitable, particularly when sprint-performance indices are determined from an uncorrected method.
Neuromuscular and Endocrine Responses of Elite Players During an Australian Rules Football Season
Authors: Cormack Stuart J. , Newton Robert U. , McGuigan Michael R. , Cormie Prue
Published: August 2016

Purpose:

To examine variations in neuromuscular and hormonal status and their relationship to performance throughout a season of elite Australian Rules Football (ARF).

Methods:

Fifteen elite ARF players performed a single jump (CMJ1) and 5 repeated countermovement jumps (CMJ5), and provided saliva samples for the analysis of cortisol (C) and testosterone (T) before the season commenced (Pre) and during the 22-match season. Magnitudes of effects were reported with the effect size (ES) statistic. Correlations were performed to analyze relationships between assessment variables and match time, training load, and performance.

Results:

CMJ1Flight time:Contraction time was substantially reduced on 60% of measurement occasions. Magnitudes of change compared with Pre ranged from 1.0 ± 7.4% (ES 0.04 ± 0.29) to −17.1 ± 21.8% (ES −0.77 ± 0.81). Cortisol was substantially lower (up to −40 ± 14.1%, ES of −2.17 ± 0.56) than Pre in all but one comparison. Testosterone response was varied, whereas T:C increased substantially on 70% of occasions, with increases to 92.7 ± 27.8% (ES 2.03 ± 0.76). CMJ1Flight time:Contraction time (r = .24 ± 0.13) and C displayed (r = −0.16 ± 0.1) small correlations with performance.

Conclusion:

The response of CMJ1Flight time:Contraction time suggests periods of neuromuscular fatigue. Change in T:C indicates subjects were unlikely to have been in a catabolic state during the season. Increase in C compared with Pre had a small negative correlation with performance. Both CMJ1Flight time:Contraction time and C may be useful variables for monitoring responses to training and competition in elite ARF athletes.
Assessment of an International Breaststroke Swimmer Using a Race Readiness Test
Authors: Thompson Kevin G. , Garland Stephen W.
Published: August 2016

Competitive swimmers routinely undertake a 7 X 200-m incremental step test to evaluate their fitness and readiness to compete.1 An exercise protocol more closely replicating competition swimming speeds may provide further insight into the swimmer’s physiological and technical readiness for competition. This case study reports data over a 3-year period from 11 Race Readiness Tests, which were completed, in addition to the 7 X 200-m test, as an attempt to provide the swimmer and coach with a fuller assessment. For this individual, data provided objective information from which to assess training status and race readiness following a transition from 200-m to 100-m race training. Data also raised a question as to whether a 100-m maximal effort 10 minutes before another one actually enhances performance owing to a priming effect.
Cycling Efficiency and Performance Following Short-Term Training Using Uncoupled Cranks
Authors: Williams Andrew D. , Raj Isaac Selva , Stucas Kristie L. , Fell James W. , Dickenson Diana , Gregory John R.
Published: August 2016

Objectives:

Uncoupled cycling cranks are designed to remove the ability of one leg to assist the other during the cycling action. It has been suggested that training with this type of crank can increase mechanical efficiency. However, whether these improvements can confer performance enhancement in already well-trained cyclists has not been reported.

Method:

Fourteen well-trained cyclists (13 males, 1 female; 32.4 ± 8.8 y; 74.5 ± 10.3 kg; Vo2max 60.6 ± 5.5 mL·kg−1·min−1; mean ± SD) participated in this study. Participants were randomized to training on a stationary bicycle using either an uncoupled (n = 7) or traditional crank (n = 7) system. Training involved 1-h sessions, 3 days per week for 6 weeks, and at a heart rate equivalent to 70% of peak power output (PPO) substituted into the training schedule in place of other training. Vo2max, lactate threshold, gross efficiency, and cycling performance were measured before and following the training intervention. Pre- and post testing was conducted using traditional cranks.

Results:

No differences were observed between the groups for changes in Vo2max, lactate threshold, gross efficiency, or average power maintained during a 30-minute time trial.

Conclusion:

Our results indicate that 6 weeks (18 sessions) of training using an uncoupled crank system does not result in changes in any physiological or performance measures in well-trained cyclists.
Relationship Between Relative Net Vertical Impulse and Jump Height in Jump Squats Performed to Various Squat Depths and With Various Loads
Authors: McBride Jeffrey M. , Kirby Tyler J. , Haines Tracie L. , Skinner Jared
Published: August 2016

Purpose:

The purpose of the current investigation was to determine the relationship between relative net vertical impulse (net vertical impulse (VI)) and jump height in the jump squat (JS) going to different squat depths and utilizing various loads.

Methods:

Ten males with two years of jumping experience participated in this investigation (Age: 21.8 ± 1.9 y; Height: 176.9 ± 5.2 cm; Body Mass: 79.0 ± 7.1 kg, 1RM: 131.8 ± 29.5 kg, 1RM/BM: 1.66 ± 0.27). Subjects performed a series of static jumps (SJS) and countermovement jumps (CMJJS) with various loads (Body Mass, 20% of 1RM, 40% of 1RM) in a randomized fashion to a depth of 0.15, 0.30, 0.45, 0.60, and 0.75 m and a self-selected depth. During the concentric phase of each JS, peak force (PF), peak power (PP), jump height (JH) and relative VI were recorded and analyzed.

Results:

Increasing squat depth corresponded to a decrease in PF and an increase in JH, relative VI for both SJS and CMJJS during all loads. Across all squat depths and loading conditions relative VI was statistically significantly correlated to JH in the SJS (r = .8956, P < .0001, power = 1.000) and CMJJS (r = .6007, P < .0001, power = 1.000). Across all squat depths and loading conditions PF was statistically nonsignificantly correlated to JH in the SJS (r = –0.1010, P = .2095, power = 0.2401) and CMJJS (r = –0.0594, P = .4527, power = 0.1131). Across all squat depths and loading conditions peak power (PP) was significantly correlated with JH during both the SJS (r = .6605, P < .0001, power = 1.000) and the CMJJS (r = .6631, P < .0001, power = 1.000). PP was statistically significantly higher at BM in comparison with 20% of 1RM and 40% of 1RM in the SJS and CMJJS across all squat depths.

Conclusions:

Results indicate that relative VI and PP can be used to predict JS performance, regardless of squat depth and loading condition. However, relative VI may be the best predictor of JS performance with PF being the worst predictor of JS performance.
Repeated-Sprint Ability: Where Are We?
Authors: Dawson Brian
Published: August 2016

Repeated-sprint ability (RSA) is now well accepted as an important fitness component in team-sport performance. It is broadly described as the ability to perform repeated short (~3–4 s, 20–30 m) sprints with only brief (~10–30 s) recovery between bouts. Over the past 25 y a plethora of RSA tests have been trialed and reported in the literature. These range from a single set of ~6–10 short sprints, departing every 20–30 s, to team-sport game simulations involving repeating cycles of walk-jog-stride-sprint movements over 45–90 min. Such a wide range of RSA tests has not assisted the synthesis of research findings in this area, and questions remain regarding the optimal methods of training to best improve RSA. In addition, how RSA test scores relate to player “work rate,” match performance, or both requires further investigation to improve the application of RSA testing and training to elite team-sport athletes.
Improvement of 800-m Running Performance With Prior High-Intensity Exercise
Authors: Ingham Stephen A. , Fudge Barry W. , Pringle Jamie S. , Jones Andrew M.
Published: August 2016

Prior high-intensity exercise increases the oxidative energy contribution to subsequent exercise and may enhance exercise tolerance. The potential impact of a high-intensity warm-up on competitive performance, however, has not been investigated.

Purpose:

To test the hypothesis that a high-intensity warm-up would speed VO2 kinetics and enhance 800-m running performance in well-trained athletes.

Methods:

Eleven highly trained middle-distance runners completed two 800-m time trials on separate days on an indoor track, preceded by 2 different warm-up procedures. The 800-m time trials were preceded by a 10-min self-paced jog and standardized mobility drills, followed by either 6 × 50-m strides (control [CON]) or 2 × 50-m strides and a continuous high-intensity 200-m run (HWU) at race pace. Blood [La] was measured before the time trials, and VO2 was measured breath by breath throughout exercise.

Results:

800-m time-trial performance was significantly faster after HWU (124.5 ± 8.3 vs CON, 125.7 ± 8.7 s, P < .05). Blood [La] was greater after HWU (3.6 ± 1.9 vs CON, 1.7 ± 0.8 mM; P < .01). The mean response time for VO2 was not different between conditions (HWU, 27 ± 6 vs CON, 28 ± 7 s), but total O2 consumed (HWU, 119 ± 18 vs CON, 109 ± 28 ml/kg, P = .05) and peak VO2 attained (HWU, 4.21 ± 0.85 vs CON, 3.91 ± 0.63 L/min; P = .08) tended to be greater after HWU.

Conclusions:

These data indicate that a sustained high-intensity warm-up enhances 800-m time-trial performance in trained athletes.
Validity of Boston Marathon Qualifying Times
Authors: Vanderburgh Paul M.
Published: August 2016

Purpose:

To assess the validity of Boston Marathon qualifying (BMQ) standards for men and women.

Methods:

Percent differences between BMQ and current world records (WR) by sex and age group were computed. WR was chosen as the criterion comparison because it is not confounded by intensity, body composition, lifestyle, or environmental factors. A consistent difference across age groups would indicate an appropriate slope of the age-vs-BMQ curve. Inconsistent differences were corrected by adjusting BMQ standards to achieve a uniform percentage difference from WR.

Results:

BMQ standards for men were consistently ~50% slower than WR (mean 51.5% ± 1.4%, range 49.6–54.4%), thus demonstrating acceptable validity. However, BMQ standards for women indicated convergence with WR as age increased (mean 45.8% ± 13.7%, range 17.5–58.9%). The women’s BMQ standards were revised to yield a consistent 50% deviation from WR across age groups (50.9% ± 0.8%, range 49.2–52.2%). Applied to all 16,773 women in the 2012 Chicago Marathon, the suggested BMQ standards would lead to a 4.90% success rate, compared with 8.39% using the current standard. This compared with a 9.6% success rate for all 20,681 men of the same race.

Conclusions:

The current women’s BMQ standards appear too lenient for women 18–54 y and too strict for women 55–80 y but yield equitable gender representation in percentage of qualifiers. The current men’s and suggested women’s BMQ standards appear valid but would lead to approximately 40% fewer women achieving BMQ standards.
New Outer Grip Technique Used by Elite Gymnasts in Performing the Felge to Handstand Mount
Authors: Takei Yoshiaki , Dunn J. Hubert , Nohara Hiroshi , Kamimura Mamoru
Published: August 2016

The subjects were 25 American and 28 Japanese gymnasts filmed during national championships. Performances were analyzed to determine the effect of grip technique at bar regrasp. It was hypothesized that the new outer grip technique would achieve significantly higher body angle and center of gravity (CG) than the inner grip technique at bar regrasp, qualities that are essential for successful performance of the basket to handstand mount on the parallel bars. It was further hypothesized that the new outer grip technique would achieve significantly (a) greater angular speed of arm rotation and vertical displacement of CG during the upward inverted swing and (b) higher body angle and CG at bar release. The results revealed significant differences in all of the areas hypothesized in favor of the new outer grip technique. Although the technique must be refined to control the tendency for excessive body arching at bar release, the new outer grip has the technical advantage for pursuing virtuosity points and new maneuvers.
Reducing Errors in Kinetic Calculations: improved Synchronization of Video and Ground Reaction Force Records
Authors: O'Connor Brian J. , Yack H. John , White Scott C.
Published: August 2016

A strategy is presented for temporally aligning ground reaction force and kinematic data. Alignment of these data requires marking both the force and video records at a common event. The strategy uses the information content of the video signal, which is A/D converted along with the ground reaction force analog signals, to accomplish this alignment in time. The vertical blanking pulses in the video signal, which define the start of each video field, can be readily identified, provided the correct A/D sampling rate is selected. Knowledge of the position of these vertical blanking pulses relative to the synchronization pulse makes it possible to precisely align the video and analog data in time. Choosing an A/D sampling rate of 598 Hz would enable video and analog data to be synchronized to within 1/1,196 s. Minimizing temporal alignment error results in greater accuracy and .reliability in calculations used to determine joint kinetics.
Biomechanical Characteristics of Preactivation and Pulling Phases of Snatch Lift
Authors: Lee Yung-Hui , Huwang Chin-Yang , Tsuang Yang-Hwei
Published: August 2016

The biomechanical characteristics of 13 snatch lifts performed by 4 elite athletes were analyzed. Electromyographic data, ground reaction force index (GRFI), knee angular velocities, barbell velocities, and lifting time were obtained 0.2 s before the lift, for the first pulling phase (FP), and for the second pulling phase (SP). The preactivation, normalized electromyographic values correlated negatively with GRFI (p < .01). In the FP and SP, all of the parameters correlated positively with each other except lifting time. GRFI in the FP also correlated positively with GRFI, maximum knee angular velocities, and maximum barbell velocities of the SP (p < .01). In the SP, the ground reaction force reached its maximum first, followed by knee angular velocity and then barbell velocity. Barbell velocity reached its maximum before the knee and the hip joint were fully extended. When the correlation of parameters between the consecutive phases of snatch weight lifting was analyzed, it was demonstrated that the preactivation of trunk and leg muscles is important in the activation of the reflectory system in order to fully utilize the forces for generating lifting speed in the pulling phase.
A Three-Dimensional Analysis of the Men’s Compulsory Vault Performed at the 1992 Olympic Games
Authors: Takei Yoshiaki , Blucker Erik P. , Dunn J. Hubert , Myers Scott A. , Fortney Virginia L.
Published: August 2016

The 20 highest scored handspring with full-turn vaults performed during the 1992 Olympic Games were compared with those receiving the 20 lowest scores. Hypotheses were that the vaults receiving high scores would (a) demonstrate larger horizontal velocity at takeoff from the board and larger vertical velocity at takeoff from the horse and (b) demonstrate greater amplitude of postflight, higher center of gravity (CG) at the completion of the full twist, and superior landing performance than those receiving low scores. Two 16-mm Locam II DC cameras, each operating at a nominal frame rate of 100 Hz, recorded the vaults. It was concluded that the vaults receiving high scores demonstrated (a) larger horizontal velocity and translational kinetic energy at takeoff from the board, larger vertical velocity and translational kinetic energy at takeoff from the horse, and greater amplitude of postflight; (b) greater heights of CG from the beginning of the second-quarter twist to halfway through the third-quarter twist; and (c) superior landing performance than those receiving low scores.
A Control Scheme for an Opposed Recumbent Tandem Human-Powered Bicycle
Authors: Cloyd Scott O. , Hubbard Mont , Alaways LeRoy W.
Published: August 2016

Feedback control of a human-powered single-track bicycle is investigated through the use of a linearized dynamical model in order to develop feedback gains that can be implemented by a human pilot in an actual vehicle. The object of the control scheme is to satisfy two goals: balance and tracking. The pilot should be able not only to keep the vehicle upright but also to direct the forward motion as desired. The two control inputs, steering angle and rider lean angle, are assumed to be determined by the rider as a product of feedback gains and “measured” values of the state variables: vehicle lean, lateral deviation from the desired trajectory, and their derivatives. Feedback gains are determined through linear quadratic regulator theory. This results in two control schemes, a “full” optimal feedback control and a less complicated technique that is more likely to be usable by an inexperienced pilot. Theoretical optimally controlled trajectories are compared with experimental trajectories in a lane change maneuver.
Forces and Moments at the Knee and Boot Top: Models for an Alpine Skiing Population
Authors: Yee Albert G. , Mote C. Daniel
Published: August 2016

The purpose of this study was to identify regression models to predict moments at the boot top and knee from the force components at the bindings for a sample of skiers. Six subjects skied a slalom course, first with their boots set to the least stiff setting and then with their boots set to the most stiff setting. Six load component dynamometers measured force and moment components at the toe and heel bindings. An electrogoniometer measured ankle flexion. Regression models were developed for the subject sample that predicted quasi-static moment components at the boot top and knee from measurements of ankle flexion and the quasi-static force components at the bindings. Large anterior bending moment was not necessarily accompanied by large ankle flexion, which emphasized that binding designs and standards for injury prevention must account for forces and moments at the sites of potential injury, rather than limiting consideration to boot stiffness or forces at the bindings.
Lower-Extremity Kinetic Response to Activity Program Dosing in Older Adults
Authors: Salem George J. , Wang Man-Ying , Azen Stanley P. , Young Jean T. , Greendale Gail A.
Published: August 2016

The purpose of this investigation was to determine the effects of two doses of a weighted vest on acute lower-extremity gait kinetics in older adults. Peak ankle, knee, and hip net joint moments were quantified in 56 men and women volunteers (73.8 ± 6.9 years old) enrolled in a 6-month physical activity study. At the initial study visit, participants underwent 6 walking trials (3 with vest, 3 without vest) at their normal pace. During the vest-wearing trials, participants wore a vest loaded with either 0% of body weight (BW) (n = 19), 3% of BW (n = 16), or 5% of BW (n = 21). With acute application of the vests, maximum peak plantarflexion moments increased by 5.7% in the 5% BW group compared to the 0% BW group, p < 0.01. Compared to the 0% vest-weight group, knee extension moments increased by 13.8% when 5% BW was applied, p < 0.01; a marginally significant treatment effect was evident in the 3% BW group, p = 0.04. Despite these acute alterations, knee strength and physical performance did not improve when subjects wore the vests 2 hours a day, 4 days a week for 27 weeks, without additional exercise prescription. These findings suggest that: (a) the acute changes in vest-mediated lower-extremity kinetics are not systemic but joint specific and load dependent, and (b) weighted vest prescription should be greater than 5% BW without prescribed exercise, or should include prescribed exercises, to invoke long-term strength and physical performance gains in older adults.
A Method for Classifying Co-contraction of Lumbar Muscle Activity
Authors: Hughes Richard E. , Bean James C. , Chaffin Don B.
Published: August 2016

Concurrent activation of muscles on opposite sides of joints is a common phenomenon. In simple planar mechanical systems, it is easy to identify such an electromyographic pattern as co-contraction of agonist and antagonist muscles. In complex 3-D systems such as the lumbar spine, it is more difficult to precisely identify whether EMG recordings represent co-contraction. Qualitative definitions of antagonist muscles emphasize that their actions wholly oppose the action of the prime movers. The qualitative definition of antagonist muscles was used to formulate a mathematical requirement for there to be co-contraction of agonists and antagonists. It was shown that the definition of co-contraction implies muscle activity beyond what is required to maintain equilibrium. The method was illustrated by classifying EMG recordings made of the lumbar region musculature during tasks involving combined torso extension and axial twisting loads. The method, which identified muscle activity in excess of that required to maintain static equilibrium, could be used to identify conditions in which muscle activation is required for something other than merely maintaining moment equilibrium.
Initiating Rotation in Back and Reverse Armstand Triple Somersaults Tuck Dives
Authors: Murtaugh Karen , Miller Doris I.
Published: August 2016

To determine strategies for initiating rotation in armstand back and reverse triple somersaults tuck dives from the 10-m platform, videotaped records of 17 elite male divers performing in competitions between 1995 and 1999 were analyzed. Linear and angular momenta at last contact were similar for both dives. Although the lower extremity actions were comparable, they occurred significantly earlier (p < .05) in reverse triple takeoffs, allowing divers to enter the tuck more quickly. As divers lean, the moment arm of the vertical platform reaction force increases with respect to the CG. The vertical platform reaction force moment promotes back and opposes reverse somersaulting angular momentum. Meanwhile, the horizontal platform reaction force moment promotes reverse and opposes back somersaulting angular momentum. Consequently, divers performing reverse triples maintained a more vertical trunk position during the early part of the takeoff, while those executing back triples leaned further before initiating lower and upper extremity actions to exert force against the platform. Since the strategy for reverse rotation may result in the head passing close to the platform and there is very little to gain in degree of difficulty, it is recommended that competitors execute back rather than reverse somersaulting armstand dives.
Modeling Resistance of a Four-Link Biped to Lateral Push
Authors: Dietrich Gilles , Wing Alan Mark , Gilles Martine , Nimmo-Smith Ian
Published: August 2016

This paper presents a conceptual model for studying the contribution of each leg to sideways stability of a four-link biped. It was assumed that a linear feedback controller maintained balance with torque related to the deviation from a reference value of the angle made by the trunk with the vertical. Predictions for ground reaction forces produced in resisting sideways push at the pelvis, based on simulation using a simple linear controller, are presented for two special cases (using one or both legs). This simple model was then compared to experimental data in which participants were asked to resist a sideways push. It was observed that all participants employed a strategy in which one leg was used to develop the force response. With this simple model, it was possible to simulate different kinds of responses to the balance perturbation. This model could be considered the first step of a more complex model in order to include specific components related to physiological parameters.
A Nonlinear Rheological Model for Active and Passive Skeletal Muscle
Authors: Corr David T. , Vanderby Ray , Best Thomas M.
Published: August 2016

An existing rheological model of skeletal muscle (Forcinito et al., 1998) was modified with a nonlinear Maxwell fluid element to provide a phenomenological model capable of analyzing the strain-stiffening behavior typically found in passive, and occasionally observed in active, skeletal muscle. This new model describes both active and passive muscular behavior as a combination of the behavior of each model component, without requiring prior knowledge of the force-length or force-velocity characteristics of the muscle.
Accuracy of a System for Measuring Three-Dimensional Torso Kinematics during Manual Materials Handling
Authors: Giorcelli Rebecca J. , Hughes Richard E. , Current Richard S. , Myers John R.
Published: August 2016

This paper describes a procedure developed and validated to assess the accuracy of an infrared-based motion measurement system used to perform a kinematic analysis of the torso with respect to the pelvis during simulated lifting tasks. Two rigid reflective marker triads were designed and fabricated for attachment to the thorax over the 6th thoracic vertebra and the pelvis. System accuracy was assessed for planar rotation as well as rotations about multiple orthogonal axes. A test fixture was used to validate known triad orientations. The spatial coordinates of these triads were collected at 120 Hz using a ProReflex motion measurement system. Single value decomposition was used to estimate a rotation matrix describing the rigid body motion of the thorax triad relative to the sacral triad at each point in time. Euler angles corresponding to flexion, lateral bending, and twisting were computed from the rotation matrix. All measurement error residuals for flexion, lateral bending, and twisting were below 1.75°. The estimated mean measurement errors were less than 1° in all three planes. These results suggest that the motion measurement system is reliable and accurate to within approximately 1.5° for the angles examined.