Biomechanical, anthropometrical and physical profile of the North-West University Club netball players and the relationship to musculoskeletal injuries

Abstract

Background: Netball is a physically demanding game and is associated with traumatic and overuse injuries, and it is therefore associated with high injury incidences (Hopper, 1986; Eggar, 1990). Literature indicates that deficiencies of certain parameters such as biomechanics, anthropometry and physical/motor abilities (agility, balance and explosive power) could influence a netball player's susceptibility to injury as well as the player's physical performance during a game (Arnheim & Prentice, 2000; Brukner & Khan, 2001; Bell-Jenje & Bourne, 2003; Kendall, McCeary & Provance, 1993; Fuller & Drawer, 2004; Rossouw & Rossouw, 2003; Whiting & Zernicke, 1998; Jones & Knapik, 1999; Murphy, Connoly & Beynnon, 2003; Trojian & McKeag, 2006; Moss 2002; Swanik & Swanik, 1999). Fortunately, effective conditioning exercises are available to improve biomechanical deviations, inadequate anthropometry or unacceptable physical/motor abilities (agility, balance and explosive power), and therefore it is essential to identify these shortcomings prior to the start of the netball season by means of assessment occasions (Junge et ah, 2004; Gabbet, 2004; Armsey & Hosey, 2004; Schwellnus & Derman, 2001). Aims: The primary aim of this study was to determine the physical profiles of netball players from the North-West University (NWU) Netball Club aged between 18 and 23 years, with reference to the biomechanics, anthropometric measurements and physical/motor abilities (balance, agility and explosive power). The secondary aim was to identify shortcomings in the physical profiles (biomechanical variables, anthropometrical components and physical/motor abilities) of the netball players that could contribute to musculoskeletal injuries among these players. Design: A descriptive study was made of the physical profiles of NWU Netball Club players. Subjects: Female netball players from the first, second, third, fourth and the u/19 A and B teams of the North-West University Netball Club participated in this study. Forty players were tested during testing occasion one and 25 players were tested during testing occasion two. Method: The players were tested pre-season in March 2007. The tests involved a thorough biomechanical analysis, anthropometrical measurements and the determining of physical/motor abilities, including agility, balance and explosive power. These tests were conducted by applying a recent approach that measures a combination of symmetry, dynamic mobility and local stability of the body for the biomechanical assessment (Hattingh, 2003). For the anthropometric measurements, three standardised variables were used: body fat percentage by means of 6 skin fold measurements, stature by means of a tape measure, and body mass by means of a calibrated scale (Ross & Marfell-Jones, 1991); the Illinois agility run test (Kirby, 1991 & www.brianmac.demon.co.uk/illinois. htm) for agility; the computerised balance test (Techno-Therapy, 1992) for balance, and the vertical jump for explosive power, measured by means of a tape-switch sensory mat connected to a Psion organiser (Boscosystem ErgoJump www.boscosystem.com). These tests were repeated end-season in August 2007. A clinic was held for injured players every Monday and this made it possible to monitor the injuries during the season. The clinic offered a diagnostic evaluation and advice, as well as a referral to a doctor or physiotherapist for treatment, if necessary. A statistical analysis was done on all the data collected from the test batteries and injury clinics. Descriptive statistics (means, standard deviations, minimum and maximum values) were used as well as practically significant differences (d-values and p-values) (Ellis & Steyn, 2003). Results: A profile of biomechanics, anthropometry and physical/motor abilities (agility, balance and explosive power) was compiled for the NWU Netball Club players. The data of the total group of netball players revealed numerous biomechanical deviations among the netball players during the first and second testing occasion. With regard to anthropometry, the total group presented with an ideal body mass index (BMI) but with an above-average fat percentage (testing occasions one and two). The results of the first testing occasion showed that the performance of the total group was relatively acceptably regarding the agility and explosive power tests, but under-performed in the balancing test, according to the norm set for elite netball players. In the second testing occasion for the physical/motor tests, it was found that the netball club players performed relatively acceptably in the agility and balancing tests, but under-performed in the explosive power test. The biomechanical assessment of the juniors and seniors indicated that the juniors presented with less biomechanical deviations than the seniors during both testing occasions. The anthropometrical assessment indicated that the BMI results of both groups (juniors and seniors) fell in the ideal category. The juniors as well as the seniors presented with above-average values for fat percentages. During the first tests the juniors performed better than the seniors on two (agility and balance) of the three physical/motor tests. The average agility scores for both groups fell in the average category, while the average value for the ability to balance was unacceptable. The seniors presented with a better average score for explosive power than the juniors, but the averages of both groups were considered acceptable. However, upon the second testing occasion the seniors outperformed the juniors in all three physical/motor tests. The averages for agility and balance were considered acceptable, but the averages for explosive power performances were unacceptable. Among the centre and goal players the biomechanical data revealed that the goal players presented with less biomechanical deviations than the centre players during the first and second tests. The anthropometric assessment indicated that both groups presented with ideal BMI and with above-average fat percentages (testing occasions one and two). In all three physical/motor tests (agility, balance and explosive power) in the first and second testing occasions, the centre players performed better than the goal players. During the first testing occasion, both groups performed acceptably in the agility and explosive power test, but they underperformed in the balance test. However, during the second testing occasion, the results of the centre players were acceptable for all three physical/motor tests, but the goal players underperformed in the explosive power test. The data of the first and second testing occasion indicated that the B-grade players presented with better biomechanics than the A-grade players in most of the tests. For the anthropometric assessment, both groups (A- and B-grade players) presented with ideal BMI averages, but with above-average fat percentages. The physical/motor tests revealed that the A-grade players performed better than the B-grade players in all three physical/motor tests (agility, balance and explosive power). The averages of the A- and B-grade players were considered acceptable for all three physical/motor tests during the first testing occasion, but during the second testing occasion the B-grade players underperformed in the explosive power test. A comparison of the results of the first and second testing occasion shows that the biomechanics and the anthropometrical status of the total group deteriorated through the season, although insignificantly so. The physical/motor abilities (agility and balance) of the total group improved significantly, with a significant decrease in performance on the explosive power test. The same tendencies were identified among the different groups (juniors and seniors; centre and goal players; A- and B-grade players), namely a deterioration in biomechanics and anthropometry, an improvement in agility and balance, and a decrease in explosive power abilities. A netball epidemiological study was done on the data collected in the weekly injury clinics. The study recorded 46 injuries among the NWU Netball Club players during the season. The overall injury incidence (7.63 injuries/1000 player-hours) of the total group of netball players of this study was higher than the injury incidences for existing studies on netball (Ekstrand & Tropp, 1990). The seniors, centre players and A-grade players presented with higher injury incidences than the juniors, goal players and B-grade players respectively. The body part mostly affected by injuries was the ankle joint, with incorrect landing as the most common cause of injury. Conclusion: A physical profile of every NWU Netball Club player (aged between 18 and 23 years) was documented, and included a thorough biomechanical analysis, an assessment of the player's anthropometrical status and performance in physical/motor ability tests, which consisted of an agility run, balancing and an explosive power test. Numerous biomechanical deviations, unacceptable anthropometry and average physical/motor abilities were identified among the netball players. These physical deficiencies could negatively influence a netball player's performance and could also contribute to musculoskeletal injuries. The injury incidence for the total group of netball players revealed a higher prevalence than previous studies on netball players. This could be ascribed to the numerous biomechanical deviations, unacceptable anthropometry and average physical/motor abilities which were identified among the netball players. A comparison of the incidences of injury among the different groups (juniors and seniors; centre and goal players; and A- and B-grade players) indicated that the groups (seniors, centre players and A-grade players) which presented with more biomechanical stressors, presented with more injuries during the season (higher incidences of injury) than their counterparts (juniors, goal players and B-grade players), who performed better on the biomechanical assessments. Therefore, the conclusion could be made that netball players with more biomechanical deviations sustain more injuries than netball players with better biomechanical status.