Characterisation of Postural Control During a Surf-like Postural Assessment

Introduction

Surfing is a popular sport practiced at competitive and recreational levels on beaches worldwide. At a competitive level, surfing requires various high intensity physical capacities, such as muscular strength and endurance, balance, postural control and neuromuscular coordination. In addition, athletes are also subject to external factors such as different ocean currents, wind orientation, type of sea floor, size of the waves, water temperature and contact with the board and other surfers, among other factors; these factors require quick and efficient adaptations from the athletes. Nowadays, surfing has become an even more acrobatic and dynamic sport, particularly at competitive levels, increasing the number of injuries acquired while riding waves. The adoption of an incorrect posture due to instability of the board as well as the environment during the course of manoeuvers, generates the ideal scenario for injury to occur. The evaluation of postural control in a surfer is a challenge for sports science and injury prevention researchers. This analysis is necessary so as to assess surfers sensorimotor control, in order to implement injury prevention strategies and to adopt specific training practices out of the water. However, the aquatic environment is hostile for electronic equipment, making it difficult to measure and acquire data concerning postural parameters.

There are several studies that developed an electronic solution to determine the kinesiological variables a surfer’s body is exposed to (e.g., force and acceleration); this has contributed to the understanding of the mechanisms responsible for the occurrence of injuries. However, in these studies no surfers were evaluated. The evaluation of postural control in different profiles of surfers is important to understand if variables such as participating in competitions and exhibiting better execution of techniques, as well as being older (greater maturity) and/or having more years of practice could influence movement control, allowing individuals to perform the manoeuvers more efficiently. This study aimed to characterise, through surf-like postural assessment, the postural control that surfers perform, in order to understand which factors could lead to greater or inferior control of the centre of pressure (CoP).

Methods

A cross-sectional descriptive survey was used to collect data in this study. This study was approved by the Ethics Committee of the Algarve Regional Health Administration. Written informed consent was obtained from all participants; if under 18 years of age, the informed consent was signed by parents (or the individual who was legally responsible).

Population

The study population comprised Portuguese surfers residing in southern Portugal. The study included both males and females, and participants were eligible for inclusion if they were 8 years of age or older. All participants agreed to participate voluntarily in the research.

To be included, volunteers had to have no injuries at the moment (self-reported), had to have been practicing surfing for at least one year, with at least one training session per week, and had to be available to be present during data acquisition sessions.

Measures

Measuring instruments included a questionnaire and a force platform. Data were collected in Portimão city (south of Portugal), in different places: Portimão Surf Club, Future Surfing School, Play Surf School and Fisiorider Office, in 2016. Based on a previous study7, a specific questionnaire was used. This questionnaire was applied to a sample of 101 competitive surfers (85.1% male; n = 85), aged 10 to 44 years (19.3±7.2 years), who participated in the Regional Circuit of the South and Lisbon area in 2015. The questionnaire included questions about age, gender, position of the feet on the board ("regular" - used the left foot forward and the right foot back, or "goofy" - right foot forward and left foot back), level (recreational or competitive athlete), years of practice, frequency of training per week, participation in competitions in last year, model of boards. The questionnaire was administered by a researcher with substantial experience in this field. The questionnaire was administered via interview. The researcher did not interfere with the volunteer’s opinion or produce biased answers, and was able to clarify any possible doubts or questions raised by the volunteers. For the evaluation of postural behaviour, a force platform (Footscan® Plate RSscan International, version Balance 2nd generation) was used. Postural balance control was evaluated through the length, amplitude and area travelled by the centre of pressure (CoP) displacement (vertical projection of the centre of gravity on the support base) of a subject standing with bipedal support. The sampling frequency was set at 50 Hz (number of points/sec). The force platform was positioned on the top of a surfboard, which was located on the top of a Bozu (inverted hemi sphere) to simulate, as much as possible, the instability associated with the movement carried out to catch a wave (Figure 1). The orientation of the board took into account the classification of surfers as "regular" or "goofy" (related to the position of the feet).

Results

In the group who had up to five years of surf practice, differences in CoP displacement in the mid-lateral direction (38.69mm versus 30.21mm), the CoP path length (2079.49mm versus 1635.90mm) and the CoP sway area (251.36mm2 versus 161.69mm2) were statistically significant (p≤0.05), compared with those who had more than five years of surf practice. In the group of surfers who were less than 18 years of age, displacement in the mid-lateral direction (38.30mm versus 30.54mm) and the length (2059.50mm versus 1652.89mm) were statistically significant (p≤0.05), compared to older surfers.

Conclusions

Younger surfers and those who had up to five years of practice showed greater displacement of the CoP. These data are necessary for adopting injury prevention strategies, and specific training.