Date of Award

2015

Degree Type

Thesis

Degree Name

Doctor of Philosophy

School

School of Exercise & Health Sciences

Faculty

Faculty of Health, Engineering and Science

First Advisor

Dr Jeremy M Sheppard

Second Advisor

Dr Sophia Nimphius

Third Advisor

Professor Robert U Newton

Abstract

Study 1: Development of a comprehensive performance testing protocol for competitive surfers

Purpose: Appropriate and valid testing protocols for evaluating the physical performances of surfing athletes is not well refined. The purpose of this project was to develop, refine, and evaluate a testing protocol for use with elite surfers, including measures of anthropometry, strength and power, and endurance. Methods: After pilot testing and consultation with athletes, coaches and sport scientists, a specific suite of tests was developed. Forty-four competitive junior surfers (16.2±1.3 years, 166.3±7.3 cm, 57.9±8.5 kg) participated in this study involving a within-day repeated measures analysis, using an Elite Junior Group of 22 international competitors (EJG), to establish reliability of the measures. To reflect validity of the testing measures, a comparison of performance results was then undertaken between the EJG and an age-matched Competitive Junior Group of 22 nationally competitive surfers (CJG). Results: Percent Typical Error of Measurement (%TEM) for primary variables gained from the assessments ranged from 1.1-3.0%, with intra-class correlation coefficients ranging from 0.96- 0.99. One-way analysis of variance revealed that the EJG had lower skinfolds (p=0.005, d=0.9) compared to the CJG, despite no difference in stature (p=0.102) or body mass (p=0.827). The EJG were faster in 15 m sprint-paddle velocity (pd=1.3), had higher lower-body isometric peak force (p=0.04, d=0.7), and superior endurance paddling velocity (p=0.008, d=0.9). Conclusions: The relatively low %TEM of these tests in this population allows for high sensitivity to detect change. The results of this study suggest that competitively superior junior surfers are leaner, and possess superior strength, paddling power, and paddling endurance.

Study 2: Comparison of physical capacities between non-selected and selected elite male competitive surfers for the national team

Purpose: The purpose of this study was to determine whether a previously validated performance testing protocol for competitive surfers was able to differentiate between Australian elite junior surfers selected (S) to the national team, and those not selected (NS). Methods: Thirty-two elite male competitive junior surfers were divided into two groups (S=16; NS=16). The mean age, stature, body mass, sum of 7 skinfolds and lean body mass ratio (mean ± SD) were 16.17 ± 1.26 y, 173.40 ± 5.30 cm, 62.35 ± 7.40 kg, 41.74 ± 10.82 mm, 1.54 ± 0.35 for the S athletes and 16.13 ± 1.02 y, 170.56 ± 6.6 cm; 61.46 ± 10.10 kg; 49.25 ± 13.04 mm; 1.31 ± 0.30 for the NS athletes. Power (countermovement jump; CMJ), strength (isometric mid-thigh pull), 15 m sprint paddling, and 400 m endurance paddling was measured. Results: There were significant (p ≤ 0.05) differences between the S and NS athletes for relative vertical jump peak force (p=0.01, d=0.9), CMJ height (p=0.01, d=0.9), time to 5, 10, and 15 m sprint paddle, sprint paddle peak velocity (p=0.03, d=0.8; PV), time to 400 m (p=0.04, d=0.7) and endurance paddling velocity (p=0.05, d=0.7). Conclusions: All performance variables, particularly CMJ height, time to 5, 10, and 15 m sprint paddle, sprint paddle PV, time to 400 m and endurance paddling velocity can effectively discriminate between S and NS competitive surfers and this may be important for athlete profiling and training program design.

Study 3: The development and evaluation of a drop and stick method to assess landing skills in various levels of competitive surfers

The purpose of this study was to develop and evaluate a drop and stick (DS) test method and to assess dynamic postural control in senior elite (SE), junior elite (JE), and junior development (JD) surfers. Nine SE, 22 JE, and 17 JD competitive surfers participated in the study. The athletes completed five drop and stick trials barefoot from a pre-determined box height (0.5 m). The lowest and highest time to stabilisation (TTS) trials were discarded, and the average of the remaining trials were used for analysis. The SE group demonstrated excellent single measures repeatability (ICC=0.90) for TTS, whereas the JE and JD demonstrated good single measures repeatability (ICC 0.82 and 0.88, respectively). In regards to relative peak landing force (rPLF), SE demonstrated poor single measures reliability compared to JE and JD groups. TTS for SE (0.69 ± 0.13 s) group was significantly (p=0.04) lower than the JD (0.85 ± 0.25 s). There were no significant (p=0.41) differences in the TTS between SE (0.69 ± 0.13 s) and JE (0.75 ± 0.16 s) groups or between the JE and JD groups (p=0.09). rPLF for SE (2.7 ± 0.4 body mass; BM) group was significantly lower than the JE (3.8 ± 1.3 BM) and JD (4.0 ± 1.1 BM), with no significant (p=0.63) difference among the JE and JD groups. A possible benchmark approach for practitioners would be to use TTS and rPLF as a qualitative measure of dynamic postural control using a reference scale to discriminate amongst groups.

Study 4: Effects of stable and unstable resistance training on strength, power, and sensorimotor abilities in adolescent surfers

The purpose of this study was to investigate two different resistance-training interventions (unstable or stable) on strength, power, and sensorimotor abilities in adolescent surfers. Ten competitive female and male high school surfers were assessed before and after each of 2 x 7-week training intervention, using a within-subjects cross-over study design. Results for strength revealed no condition by time interaction or main effect for condition. However, there was a significant main effect for time, with significant strength gains post-training. There was a significant condition by time interaction for power exhibited as a significant decrease from pre- to post-training in the unstable condition, while the stable condition approached significant improvement. These results suggest that unstable and stable resistance training are equally effective in developing strength in previously untrained competitive surfers, but with little effect on sensorimotor abilities. However, unstable training is inferior for the development of lower body power in this population.

Study 5: Effect of four weeks detraining on power, strength, and sensorimotor ability of adolescent surfers

The purpose of this study was to investigate the effect of four weeks of detraining on power, strength, and sensorimotor ability in adolescent surfers. Nineteen adolescent surfers with an overall mean age, mass, and stature (mean ± SD) of 14.1 ± 1.6 y, 54.0 ± 10.8 kg and 165.1 ± 9.0 cm, respectively, volunteered to participate in four weeks of detraining (surfing participation maintained but resistance training ceased) following seven weeks of periodized resistance training. Power (vertical jump height; VJH), maximal isometric strength (isometric mid-thigh pull; IMTP), and sensorimotor ability (time to stabilization during a drop and stick (DS); TTS) pre-test results were determined from the conclusion (post-test) of the first seven-week training block while post-test results were measured at the start (pre-test) of a second seven-week training block. Four weeks of detraining significantly decreased the following variables: VJH by -5.26%, (p = 0.037, d = -0.40), vertical jump peak velocity by -3.73% (p = 0.001, d = -0.51), maximal isometric strength by -5.5%, (p = 0.012, d = -0.21), and relative maximal isometric strength by -7.27% (p = 0.003, d = -0.47). Furthermore, sensorimotor ability worsened, as assessed by TTS, with a significant increase of 61.36% (p = 0.004, d = 0.99), indicating athletes took longer to stabilize from a dynamic landing task. This demonstrates that surfing, in the absence of resistance training, is not a sufficient training stimulus to maintain physical characteristics. Adolescent surfers with a relatively low training age should avoid cessation of resistance training and strive to maintain consistent resistance training in conjunction with surf training in order to avoid negative decrements in physical characteristics that are associated with surfing performance.

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