Surfing is a judged sport. As a result, there is an element of subjectivity in terms of what type of performance gets a good score. Results obtained in the present study, examining world elite surfers, clearly show that surfing performance is difficult to predict. These observations are consistent with the popular notion that the predictability of a surfer's performance is low. To our knowledge, this is the first study reporting variability of performance outcomes in a subjective (i.e., externally judged), non-time-based sport such as surfing.
Comparison of the variability of competitive outcomes between surfers and those reported in other sports, such as swimming (12,13), running (7), or weightlifting (9), is difficult because, among other things, surfing is not a time-based sport. The reliability of competitive performance in swimmer and runners, expressed as a coefficient of variation (CV), has been reported to range from 1.2 to 3.1% and from 1.2 to 4.2%, respectively. Converting results in our study to CV, values for surfers were much higher, ranging from 32.9 to 700.6%. Several factors are likely to explain the origin of these differences between surfers and time-based sports. The obvious explanation is that the subjective nature of surfing performance assessment induces an inherent degree of variability compared with, e.g., the objective (i.e., time based) performance assessment in running or swimming. However, surfers contesting within the ASP circuits, either WCT or WQS, have to fulfill the same judging criteria to maximize their scoring opportunities (8). While the complete suppression of these subjective elements associated with surfing judging seems to be difficult, this uniformity in the judging criteria should avoid, at least partially, large disparities in judges' performance outcomes. Therefore, some other factors need to be considered to further explain the low consistency in surfing performance observed in the present study.
Competitive success in surfing is believed to depend on the complex interactions between many variables (10). In addition to the complex interrelationships between surfer's psychological, tactical, cognitive, biomechanical, and physiological capacity, specific to every sport, surfing performance can also be influenced by several external factors such as equipment, wave conditions, level of the opponents and, as previously mentioned, judging (10,11). Among all these factors, wave conditions (i.e., type, shape, and height) are likely to be the most relevant to explain the high degree of surfers' performance variability. Wave conditions can vary drastically from day-to-day at the same surfing venue (2): swell size, speed and direction, tides, currents, the characteristics of the shore bottom, kelp, and wind direction and strength all affect wave conditions. Every surf venue has a unique set of variables that will ultimately define the “anatomy” of a particular wave. Thus, wave conditions would eventually dictate what manoeuvres will be possible on any given day (2). It is possible that different wave characteristics better fit particular surfers' technical skills. For example, “rights” (i.e., waves that break from the “peak” to the surfer's right) might be better for “regular footer” surfers (i.e., a stance in which the right foot is at the rear on the board) than for “goofy footer” surfers (i.e., a stance in which the left foot is at the rear on the board). This is because regular footer surfers are gliding over the wave facing their look to the wall of the wave, which is believed to be advantageous for fast and precise surfing. Therefore, we speculate that the low performance predictability observed in top surfers might arise from the multiple combinations of possible competition scenarios that surfing venues may offer. Further research is required to quantify the contribution of these different factors on surfing competitive performance.
For WQS seeded surfers, the variation in performance between events was smaller than for WCT and WQS unseeded surfers. A possible explanation for this, somewhat better predictability in competitive performance for WQS seeded surfers, is that seeded surfers entered the competition in latter rounds than unseeded surfers. That is, seeded surfers started the competition closer to the final and, therefore, they performed a lower number of rounds than unseeded surfers. The possibility to dispute a higher number of rounds by unseeded surfers might have been related to the increased variability in competitive results observed in the present study. Familiarity with competition is also another likely factor for the reduced variability in seeded surfers, as surfers are seeded based on the results obtained in the previous season.
To change an elite athlete's chance of improving his/her position in a competition, an intervention has to change that athlete's performance by an amount equivalent to ∼0.5 the typical variation in an athlete's performance from competition to competition (∼0.2 expressed in Cohen units) (3,5,6). The variation between competitions for the top male professional surfers ranged from 0.61 to 1.04 Cohen units. That is, the test (i.e., competition) noise is much higher than the smallest worthwhile change. As tests suitable for detecting such small changes in performance need to be less noisy than the typical variation of the athlete between events, assessment of changes in competitive performance in surfing as a result of short-term (i.e., between consecutive competitions) training, nutritional, or other interventions in surfers appear to be problematic (3,5,6). A practical solution could be average the score of several competitions in a row to reduce the noise (5). If we assume that the smallest worthwhile change in performance that has a substantial effect on the athlete's chance of improving his/her final placement in a competition is ∼0.5 (or 0.2 expressed in Cohen units) of the typical variation of performance in competitions, then the smallest worthwhile change in performance for a surfer is ∼0.5 (0.2 Cohen units) of the typical error in the events (3,5,6). The smallest worthwhile change in performance is half the noise, so the noise is twice as big as the signal. In the present study, if we assume the minimum typical variation of performance of 0.61 Cohen units in this cohort of top level and we take the average performance across 10 events, the noise will be halved (i.e., noise-0.8-divided by root 10), which makes the noise (0.19 Cohen units) slightly smaller than the signal (0.20 Cohen units) (5). Coaches and scientists are advised to consider these time frames when examining possible performance enhancement interventions and when evaluating the progression in competitive performance of top-level surfers.
In summary, we have demonstrated that performance of professional surfers is difficult to predict. The typical variation (within-subject variation expressed as a Cohen ES) in competitive performance ranged from 0.61 to 1.04. The reasons for this relatively high competitive performance variability could be related to a number of factors, including nonreplicable and unpredictable environmental factors within and between events and the subjective nature of surfing performance assessment. This study provides a framework for examining the significance of changes in competitive performance assessment in top professional surfers.
Changes is competitive performance are the major concern of professional athletes and their support team. The present study is the first investigating the variability in competitive performance in an externally judged sport such as surfing. The results of the present study suggest that performance of elite surfers is not very stable (i.e., difficult to predict) throughout the competitive season. Information about this variation in performance is also important for those interested in factors that affect competitive performance, such coaches and sport scientists. Considering the large variability in competitive performance reported in this study, a practitioner monitoring an elite, male, professional surfer will have little hope of noticing small to moderate changes in competitive performance between consecutive events. Thus, testing the effects of acute short-term nutritional training or other interventions appears to be impractical in surfers. On the basis of these observations, several competitions in a row appear to be needed for tracking the smallest worthwhile performance change in competition scores in this cohort of surfers as a result of different training interventions. Moreover, this time frame (i.e., several competitions in a row) is needed to monitor competitive progression in top-level surfers. We also advice coaches and sport scientist to analyze surfer's performance in different wave conditions to determine how best to make such changes in performance.
The excellent statistical guidance provided by Dr. Will G. Hopkins is greatly appreciated.
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Keywords:© 2010 National Strength and Conditioning Association
elite athletes; reliability; surfing; reproducibility of competitive performance