An investigation on the effects of recreational surfing on control of force and posture in older surfers
Zhou, S, Martin, F, Bezerra, P & Crowley, Z 2008, 'An investigation on the effects of recreational surfing on control of force and posture in older surfers', International Convention on Science, Education and Medicine in Sport, Guangzhou, China, 1-5 August, ICSEMIS Organizing Committee. vol. 3, p. 336.
The sport of surfing has been growing rapidly in popularity and Australia has a relatively large surfing population. However, limited scientific investigations have been conducted into this sport. Particularly, the long-term physiological adaptations of participating in surfing have not been examined. Exercises that require precise joint movements and depend on a double weight bearing stance have shown positive effects on balance control in older adults. The aim of this study was to investigate whether older adults who had been participating in surfing for more than 40 years would demonstrate superior performance in control of balance and posture as compared to age-matched and physically active non-surfers.
Methodology / Methods
One group of surfer with age 55-65 years volunteered for the study. The selection criteria were that they had participated in surfing at least twice per week for at least 40 years, and currently were surfing on average 7.5 hours per week. Eleven eligible subjects were recruited from the local population. Another group of the age-matched subjects (n = 11) were recruited as control. They were healthy and participated in walking, golf and/or cycling at least twice per week. The physiological variables measured for comparison between two groups included joint position sense (JPS), maximal voluntary contraction force (MVC), rate of force development (RFD), steadiness in control of muscle force at 5, 15 and 25%MVC levels, and body sway in standing position under four different conditions. The parameters that were measured for postural sway included total area, range covered, mean velocity and random movements (diffusion coefficients) in all four directions, as recorded via a force plate (Kistler, Type 9287) and analysed using custom designed software. Four muscle groups were investigated, including knee extensors and flexors and the ankle dorsi-and plantar flexors. Descriptive and ANOVA statistical analysis (SPSS) were used to assess differences between groups, with alpha level set at P < 0.05.
The results indicated that older surfers had significantly lower muscle force fluctuations in the steadiness tests. The standard deviation of force variations in the surfers was significantly lower at 15 and 25% MVC of the knee flexors (P= 0.027 and 0.035 respectively) and at 25% MVC of the ankle plantar flexors (P=0.012) than the control subjects. When assessing the coefficient of variation, the two groups were deemed different at 5, 15 and 25% MVC of the knee flexors (P= 0.000 for all variables) and at 5 and 25% MVC of the ankle plantar flexors (P= 0.029 and 0.001 respectively). The older surfers also showed less postural sway in standing position. The long-term diffusion coefficient in the anterior-posterior direction was significantly lower (P = 0.04) as was the short-term-diffusion coefficient in the medial-lateral direction (P = 0.03). The results indicated that the surfer group had less random movement in all directions, especially when reliance on proprioceptive feedback was highest from the ankle joint.
Discussions / Conclusions
The findings from this preliminary investigation suggest that long-term recreational surfing caused specific neuromuscular adaptations in older male surfers as compared to an age-matched, healthy and active control group. These adaptations may have resulted in increased muscular steadiness of the knee flexors and the ankle plantar flexors, and improved postural control under the experimental conditions. Possible implications of these findings in relation to ageing may be that long-term surfing reduces or even reverses the age-related decline in neuromuscular function which can ultimately lead to improved quality of life.