[Show abstract][Hide abstract] ABSTRACT: Abstract The age-related progression of elite athletes to their career-best performances can provide benchmarks for talent development. The purpose of this study was to model career performance trajectories of Olympic swimmers to develop these benchmarks. We searched the Web for annual best times of swimmers who were top 16 in pool events at the 2008 or 2012 Olympics, from each swimmer's earliest available competitive performance through to 2012. There were 6959 times in the 13 events for each sex, for 683 swimmers, with 10 ± 3 performances per swimmer (mean ± s). Progression to peak performance was tracked with individual quadratic trajectories derived using a mixed linear model that included adjustments for better performance in Olympic years and for the use of full-body polyurethane swimsuits in 2009. Analysis of residuals revealed appropriate fit of quadratic trends to the data. The trajectories provided estimates of age of peak performance and the duration of the age window of trivial improvement and decline around the peak. Men achieved peak performance later than women (24.2 ± 2.1 vs. 22.5 ± 2.4 years), while peak performance occurred at later ages for the shorter distances for both sexes (∼1.5-2.0 years between sprint and distance-event groups). Men and women had a similar duration in the peak-performance window (2.6 ± 1.5 years) and similar progressions to peak performance over four years (2.4 ± 1.2%) and eight years (9.5 ± 4.8%). These data provide performance targets for swimmers aiming to achieve elite-level performance.
[Show abstract][Hide abstract] ABSTRACT: There is a need for fair measures of country sport performance that include athletes not winning medals. PURPOSE: To develop a measure of country performance based on athlete ranks in the sport of swimming. METHODS: Annual top-150 ranks in Olympic pool-swimming events were downloaded for 1990 through 2011. For each athlete on a given rank, a score representing the athlete's performance potential was estimated as the proportion of athletes on that rank who ever achieved top rank. Country scores were calculated by summing its athletes' scores over all 32 events. Reliability and convergent validity were assessed via year-to-year correlations and correlations with medal counts at major competitions. The method was also applied to ranks at the 2012 Olympics to evaluate country swimming performance. RESULTS: The performance score of an athlete on a given rank was closely approximated by 1/rank. This simpler score has two practical interpretations: an athlete ranked seventh (for example) has a chance of 1/7 of ever achieving top rank; and for purposes of evaluating country performance, seven such athletes are equivalent to one athlete on the top rank. Country scores obtained by summing 1/rank of its athletes had high reliability and validity. This approach produced scores for 168 countries at the Olympics, whereas only 17 countries won medals. CONCLUSIONS: We have used the sport of swimming to develop a fair and inclusive measure representing country performance potential. This measure should be suitable for assessing countries in any sports with world rankings or with athletes at major competitions.
International journal of sports physiology and performance 04/2013; · 2.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: There is need for valid and powerful research designs to assess performance effects of interventions in squads of elite athletes. PURPOSE: To develop a design for investigating effects on competition performance, using performance of athletes in other squads as a control. METHODS: We used competition swim times downloaded from USAswimming.org for a season ending in the US Open, and assumed an intervention had been applied to athletes in one of the larger squads (Ford) at one competition (Santa Clara). Data were included only for swimmers who achieved >900 Hy-Tek points at the USA Swimming Nationals. Each swimmer's points were used to select their best event. Times for the resulting 368 best-event swims in 7 competitions by 148 swimmers in 19 squads were analyzed to determine the uncertainty (90% confidence interval) of the effect of the hypothetical intervention. Further analyses were performed with other selection criteria. Uncertainties were compared with those in other recent studies of competitive senior swimmers. RESULTS: Uncertainty in the effect of an intervention applied to Ford for Santa Clara would have been ±0.8%. Applying other data-selection criteria resulted in generally more uncertainty. Uncertainties in recent studies of competitive swimmers using conventional designs ranged between ±0.7% and ±2.2%. CONCLUSION: For the sport of swimming, the effects with this new design are at least as precise as those of conventional research designs using performance tests, and the outcomes are likely to have higher validity. The new design should be useful for assessing the effect of an intervention representing a substantial change from a baseline of usual practice in any sport where athletes compete often against athletes of other squads.
Medicine and science in sports and exercise 07/2012; · 4.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Research on the performance effects of acute carbohydrate supplementation is comprehensive. Here we present the first meta-analytic review of this research.
Eighty-eight randomized crossover studies in which carbohydrate supplements were consumed with or without protein before and/or during exercise provided 155 estimates for performance effects in time-to-exhaustion tests or in time trials with or without a preload. For the mixed-model meta-analysis, all effects were converted into percentage changes in mean power in a non-preloaded time trial and weighted using percentage standard errors derived from exact p-values (in a minority of studies) or from estimated errors of measurement (in all other studies). Publication bias was assessed with a plot of t-values for the random-effect solutions versus standard errors. Probabilistic inferences were derived with reference to thresholds for small, moderate and large effects on performance of 0.5, 1.5 and 2.7%.
Publication bias was reduced by excluding studies with a standard error >1.25%. In the remaining 73 studies and 122 estimates, the meta-analysed performance effects of carbohydrate supplements ranged from clear large improvements of ∼6% to clear moderate impairments of ∼2%. The best supplement inferred from the analysis consisted of a ∼3-10% carbohydrate-plus-protein drink providing ∼0.7 g/kg/h glucose polymers, ∼0.2 g/kg/h fructose and ∼0.2 g/kg/h protein. Substantial increases in the benefit of a supplement were probably small with an additional 9-hour fast and with the inclusion of ∼0.2 g/kg/h of protein, probably small to moderate with ingesting the first bolus not at the start of exercise but 1-4 hours before exercise, and possibly small with increasing the frequency of ingestion by three boluses per hour. Substantial reductions in the benefit of a supplement were possibly moderate with a supplement providing >0.25 g/kg/h fructose, and possibly small with an increase in ambient temperature of 10°C. The effect in subjects with maximal oxygen consumption higher by 10 mL/kg/min was probably trivial, and the effects of exercise duration were dependent on the concentration of carbohydrate plus protein in the supplement. The effect of including salt was unexpectedly trivial, and the effect of gender was unclear.
Carbohydrate supplements with an appropriate composition and administration regimen can have large benefits on endurance performance. More research and better reporting are required to investigate the moderating effects of gender and salt.
Sports Medicine 09/2011; 41(9):773-92. · 5.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: There is a need for a sophisticated approach to track athletic performance and to quantify factors affecting it in practical settings.
To demonstrate the application of mixed linear modeling for monitoring athletic performance.
Elite sprint and middle-distance swimmers (three females and six males; aged 21-26 yr) performed 6-13 time trials in training and competition in the 9 wk before and including Olympic-qualifying trials, all in their specialty event. We included a double-blind, randomized, diet-controlled crossover intervention, in which the swimmers consumed caffeine (5 mg x kg(-1) body mass) or placebo. The swimmers also knowingly consumed varying doses of caffeine in some time trials. We used mixed linear modeling of log-transformed swim time to quantify effects on performance in training versus competition, in morning versus evening swims, and with use of caffeine. Predictor variables were coded as 0 or 1 to represent absence or presence, respectively, of each condition and were included as fixed effects. The date of each performance test was included as a continuous linear fixed effect and interacted with the random effect for the athlete to represent individual differences in linear trends in performance.
Most effects were clear, owing to the high reliability of performance times in training and competition (typical errors of 0.9% and 0.8%, respectively). Performance time improved linearly by 0.8% per 4 wk. The swimmers performed substantially better in evenings versus mornings and in competition versus training. A 100-mg dose of caffeine enhanced performance in training and competition by approximately 1.3%. There were substantial but unclear individual responses to training and caffeine (SD of 0.3% and 0.8%, respectively).
Mixed linear modeling can be applied successfully to monitor factors affecting performance in a squad of elite athletes.
Medicine and science in sports and exercise 07/2010; 42(7):1339-44. · 4.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Creatine kinase (CK) is a marker of muscle damage and pathology present as multiple tissue-specific circulating isoforms. CK is often measured using enzyme activity assays that are unable to distinguish these isoforms. We have developed an immunoassay specific for the MM isoform of CK, found predominantly in skeletal muscle, which uses very small volumes of plasma (1-2 microL). A sandwich enzyme-linked immunosorbent assay (ELISA) for CK-MM was developed using isoform-specific antibodies. Cross-reactivity with CK-BB and MB isoforms was also assessed. The ELISA was validated using plasma samples from a group of athletes, and the measured CK-MM concentrations were correlated with CK enzyme activity assays measured by a contractor using the same samples. The CK-MM ELISA has a limit of detection of 0.02 ng/mL, an IC(50) of 2.3 ng/mL, and 5.8% cross-reactivity with CK-MB. CK-MM concentrations measured using this assay correlate well (p<0.0001, Spearman r=0.89) with enzyme activity assays. The CK-MM-specific ELISA can be used to help assess skeletal muscle damage independent of enzyme activity or interference from other CK isoforms, leading to more precise studies of muscle biology.
Journal of science and medicine in sport / Sports Medicine Australia. 10/2008; 13(1):117-9.
[Show abstract][Hide abstract] ABSTRACT: There have been few studies of the effects of nutritional strategies in training and competition settings in elite athletes. This thesis represents four studies that were performed to investigate the effect of specific acute supplementation protocols on performance and/or recovery from exercise. Studies 1-3 were experimental investigations of the recovery and/or performance effects of carbohydrate, carbohydrate-protein or caffeine supplements in elite swimmers. Study 4 was a meta-analytic review of the effects of acute carbohydrate supplementation on endurance performance. In Study 1, we have provided some evidence that consuming carbohydrate during and carbohydrate-protein immediately after a 2-h high-intensity swim session induces better recovery in plasma creatine kinase and salivary IgA compared with consuming water during exercise and carbohydrate-protein immediately after, and compared with consuming only carbohydrates during and immediately after exercise. These effects may indicate reduced muscle damage and better mucosal immunity in the upper respiratory tract. The inclusion of protein in the carbohydrate supplement also reduced inflammatory responses. As demonstrated in the meta-analysis (Study 4), consuming carbohydrate and carbohydrate-protein supplements during exercise can have large benefits in endurance performance: The best supplement inferred from the analysis consisted of the best regime derived from the analysis consisted of ingesting a ~3-10% carbohydrate-plus-protein drink providing ~0.7 g•kg-1•h-1 glucose polymers, ~0.2 g•kg-1•h-1 fructose and ~0.2 g•kg 1•h 1 protein in multiple boluses before and during exercise. Caution is required to extrapolate the results of the meta-analysis to short-duration exercise, because the meta-analysis included only one study with exercise duration <25 min. In Study 2, we found possible performance impairments in the last step of a 7x200-m step test (change in performance time 0.9%; 90% confidence limits ±1.1%) and in a 100-m time trial (0.1%; ±0.6%) with ingestion of a carbohydrate-protein supplement. In Study 3, we have provided some evidence that ingesting ~100 mg caffeine 75 min before training or competition time trials enhances performance in elite swimmers by ~1.3%. This intervention was part of a methodological investigation of a novel application of mixed linear modeling for monitoring athletic performance. Through this PhD research, we have demonstrated clear performance and recovery effects with specific acute supplementation protocols in elite swimmers. We have provided a novel approach to investigate effects of treatments in elite athletes, and we have demonstrated large effects with carbohydrate supplementation regimes in endurance exercise in an innovative meta-analytic review. We encourage athletes, sports scientists and coaches to estimate magnitudes of effects of treatments and individual responses to treatments using linear modeling of performance times.
[Show abstract][Hide abstract] ABSTRACT: Claims have been made that consumption of carbohydrate-protein-electrolyte supplements during prolonged endurance exercise enhance performance and recovery from exercise, but the effects on short-term swim endurance exercise are unclear. In the present study, we have investigated the effects of a carbohydrate-protein-electrolyte supplement on performance in a 7x200-m step-test and 100-m time-trial in highly-trained swimmers. The performance measures in this study were highly reliable. There is some evidence that the supplement impaired performance in the last step of the step-test. The effect on lactate threshold was unclear, but if anything performance in this measure was impaired too. We have also found that ingesting a single bolus of the carbohydrate-protein-electrolyte supplement 10 min before the 100-m time-trial has little effect on performance. The swimmers experienced more muscle soreness and coped less with exercise in both the step-test and time-trial when the supplement was consumed. An increase in blood glucose may be the cause of the impairments in performance and subjective ratings, but more research is needed here. We advise against the use of carbohydrate-protein-electrolyte in short-term endurance performance tests and before races in competitions. Attached is the manuscript of "Acute effects of a carbohydrate-protein-electrolyte supplement on performance in swimmers", which we will submit to an academic journal. This project was realized with financial support ($5266) of SPARC, for which we are very grateful.