The effect of a netball game on parameters of balance

Physical Therapy in Sport 5 (2004) 200–207 www.elsevier.com/locate/yptsp

Original research

The effect of a netball game on parameters of balance Nikki Waterman, Gisela Sole*, Leigh Hale School of Physiotherapy, University of Otago, P.O. Box 56, Dunedin, New Zealand Received 27 November 2003; revised 26 May 2004; accepted 4 June 2004

Abstract Objectives: The purpose of this study was to assess whether participation of players in a netball game affected the balance parameters of postural sway and the forward lunge. Further, possible associations between changes of these parameters and time since previous injury, perceived injury recovery, grade and position played were investigated. Methods: Twenty-seven female players, aged 15–29 years, were assessed before and after a netball game, using the NeuroCom Balance Mastere version 6.1. Postural sway was assessed during unipedal stance with eyes closed, for three trials of 10 s. A forward lunge was performed three times on each leg and the lunge distance relative to body height, impact force and duration of contact were determined. Paired t-tests were used to compare the parameters before and after the game. Individual linear regressions were performed to determine whether changes in parameters were associated with time since past injury, perceived recovery of injury, grade and position played. Results: Although the increase in postural sway during unipedal stance after the netball game reached statistical significance for the preferred leg, the mean increase was 0.398 sK1, indicating a 26.4% mean increase. The relative distance of the forward lunge significantly decreased for both legs following the game, with a mean decrease of 2.66% of body height. The changes in parameters were not associated with time since injury, perceived recovery, grade and position played. Conclusions: Postural sway whilst standing on the preferred leg was more likely to increase and the lunging distance to decrease bilaterally after a netball game. However, as these changes were individual-specific, testing postural sway and the lunge pre-game would not predict possible changes incurred during a netball game. q 2004 Elsevier Ltd. All rights reserved. Keywords: Netball; Postural stability; Balance; Injury

1. Introduction Netball is a goal-scoring ball sport, demanding high levels of sport-specific skills which include running, passing, catching the ball and shooting for goals (McKay, Payne, Goldie, Oakes, & Stanley, 1996). It demands rapid acceleration to ‘break free’ from an opponent, and sudden, explosive changes in direction, combined with elevating leaps to receive a high pass, intercept a ball, or rebound after an attempted goal (Steele and Milburn, 1987). In monetary terms, netball is the second most costly sport played in New Zealand (Accident Compensation Corporation, 2002), with lower limb injuries contributing a large portion of the total injuries (Hopper & Elliott, 1993; * Corresponding author. Tel.: C64-3-479-7460; fax: C64-3-479-8414. E-mail address: [email protected] (G. Sole). 1466-853X/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.ptsp.2004.06.001

Hopper, Hopper, & Elliott, 1995b; McKay, Payne, Goldie, Oakes, & Stanley, 1996). Ankle injuries may range from 24 to 84% of total injuries, while knee injuries account for 7–33% (Accident Compensation Corporation, 2002; McKay et al., 1996). Common mechanisms of injury in netball as perceived by players, include injuries associated with landing, collision with a player or post, and being hit by the ball (Hopper & Elliott, 1993; Hopper, Elliott , & Lalor, 1995a; Hume & Steele, 2000; McKay et al., 1996). The ability to balance and maintain a stable posture is integral to the execution of most movements (Carr & Shepherd, 1998). Balance plays a fundamental part in the skills of netball playing and the mechanisms of injury such as landing. There is no external criterion against which the validity of balance measures can be established (Goldie, Bach, & Evans, 1989). A variety of balance assessment tests are therefore found in the sporting literature, such as

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postural sway during bilateral stance (Derave, Tombeux, Cottyn, Pannier , & De Clercq, 2002; Hashiba, 1998; Lepers, Bigard, Diard, Gouteyron, & Guezennec, 1997; Nardone, Tarantola, Galante, & Schieppati, 1998; Nardone, Tarantola, Giordano, & Schieppati., 1997) or during unipedal stance (McGuine, Greene, Best, & Leverson, 2000; Tropp, Ekstrand, & Gillquist, 1984), and stance on movable platforms (Lepers, Bigard, Diard, Gouteyron, & Guezennec, 1997; Rowe, Wright, Nyland, Caborn, & Kling, 1999). Differing technological devices found in the sporting literature to assess balance include the NeuroCom Balance Mastere (NeuroCom International) (McGuine, Greene, Best, & Leverson, 2000), the Biodex balance system (Biodex Medical Systems) (Rowe et al., 1999), the Equiteste (NeuroCom International) (Lepers et al., 1997), and Kistler force plates (Goldie, Bach, & Evans, 1994; Nardone, Tarantola, Galante, & Schieppati, 1997, 1998). Impaired balance has been investigated as a risk factor for musculoskeletal injuries of the lower limb and as a consequence of these injuries (Goldie, Evans, & Bach, 1994; Holder-Powell & Rutherford, 2000; McGuine et al., 2000). Only one study investigating balance as a risk factor for subsequent injuries was directed towards netball players. Hopper et al. (1995a) assessed a group of 72 netball players prior to a season, timing their ability to maintain unipedal stance with eyes open and also with eyes closed. No significant differences were found between pre-season balance scores of players with subsequent injuries and uninjured players. This method of assessing balance may not have been sensitive enough to predict injury. Poor balance was identified as a risk factor for ankle injury in basketball (McGuine et al., 2000) and in soccer (Tropp, Ekstrand, & Gillquist, 1984). McGuine et al. (2000) assessed postural sway during unipedal stance in 210 basketball players prior to the basketball season, using the Balance Mastere. A positive correlation was found between the incidence of ankle sprain occurring over the following season and high postural sway. Subjects who demonstrated higher postural sway during unipedal stance had nearly seven times as many ankle sprains as subjects with low postural sway. Tropp et al. (1984) assessed 127 male soccer players using a force plate to record postural sway in unipedal stance. They found 98 players (77%) had normal values, defined as values within two standard deviations from the mean of the control group of non-soccer players. Twenty-nine players (22%) had high/pathological sway values, that is, values greater than two standard deviations from the mean of the control group. Ankle injuries that occurred over the remainder of the year were recorded and assessed. There were a significantly lower number of ankle sprains (p!0.001) in the normal sway group (11 sprains, and 11% of the normal group total) compared to the pathological sway group (12 sprains, and 41% of the pathological group total). They concluded that pathological sway values indicated an increased risk for future ankle

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injuries. Impaired balance, as defined by postural sway measures more than two standard deviations from the means, has therefore been found to be associated with increased ankle injuries in the sports of soccer and basketball. However, this association has not been established in netball players, possibly due to lack of sensitive testing procedures. Unipedal stance and forward lunging are components of tasks normally needed in the netball game. Players often need to step, lunge or stand on one leg to evade an opponent and to comply with the ‘no stepping of the grounded foot’ rule. Further, the forward lunge may be used clinically as a functional movement by physical therapists in the assessment and rehabilitation of lower extremity injuries (Brukner & Khan, 2002). However, it is not known whether components of these movements, the forward lunge and unipedal stance, change during a netball game. If these variables changed significantly during a game, it may be pertinent to assess the athlete after participation. The purpose of this study was to determine whether participation of players in a netball game affected parameters of balance, as assessed unipedal stance with eyes closed and forward lunging. Specifically, the following hypotheses were tested: H1 Sway velocity would be increased after the game for the group; H2 Lunge distance and impact would decrease and contact time would increase during the lunge; H3 These measures would be affected by past injury, and associated with perceived recovery and time since injury.

2. Methodology 2.1. Subjects Twenty-seven female players (average age 19.8G 3.5 years; weight 64.4G7.5 kg; height 172.6G5.0 cm; BMI 21.6G2.2 kg mK2) were recruited from the two highest grades of club netball (premier and senior grades) in Dunedin, New Zealand, over the 2002 season. All subjects provided informed, written consent, as approved by the University of Otago Ethics Committee. Parental consent was gained for subjects under 17 years of age. Subjects were excluded if they were under 14 years of age, had any known vestibular (inner ear) problems, had exercised (e.g. played another game) prior to testing, or did not complete an entire game of netball. The premier games consisted of four 15 min quarters while senior games consisted of four 10 min quarters. All games were played on an indoor court surface, which was concrete, covered with astroturf. Games and assessment took place at the local ambient temperature (5–10 8C).

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Table 1 Reported time and perceived recovery of 52 reported injuries (nZ26) Time period

Recovery

Total

Recovered less than 50%

Recovered 50–75%

Less than three months 3–12 months More than 12 months

2 0 2

3 4 1

2 2 7

1 8 20

8 14 30

Total

4

8

11

29

52

2.2. Assessment One subject only was selected from each netball game to ensure immediate re-testing on cessation of the activity. The assessment area was in close proximity to the netball courts and subjects were required to jog for up to 30 s from their netball game to the testing area. Prior to balance assessment, subjects completed a questionnaire regarding age, grade, leg preference, the latter defined as the preferred leg to step onto whilst throwing a ball. The location and type of past injuries were documented, as well as the time since injury and perceived recovery of these injuries (Table 1).

Recovered 75–90%

Recovered more than 90%

to the ground were allowed thereby keeping test repeats to a minimum and limiting recovery time (McGuine et al., 2000). If the subject opened their eyes, or stepped off the force plate, the trial was repeated (McGuine et al., 2000). The subjects performed three trials of ten seconds, with a rest of up to 10 s allowed between trials. Assessment was then repeated standing on the right leg. The centre of gravity sway velocity (8sway/s) was sampled at a frequency of 100 Hz and the mean for the three trials calculated by the Balance Mastere.

2.3. Balance assessment Balance assessment was conducted using the NeuroCom Balance Mastere version 6.1 (NeuroCom International, Clackamas, Oregon, USA), which measures force using variable inductance compression load cells. It includes a 46!152 cm (18!60 in.) force platform, interfaced to a computer. The Balance Mastere was calibrated before each testing session according to manufacturer’s guidelines. Assessments were completed prior to the warm-up before the game and immediately following the game, prior to cool down. The subjects performed two different activities per leg on the Balance Mastere: unipedal stance with eyes closed, and forward lunge. Subjects were given an explanation of the test procedure and allowed a trial run prior to assessment. Assessment of the two tasks took approximately 2–3 min. The principle investigator (NW) supervised all balance activities and gave the same instructions to all subjects. For the unipedal stance test (Fig. 1), subjects stood barefoot on their left leg, aligning their medial malleoli on the centering line of the Balance Mastere. The subjects placed their hands on their hips and raised their right leg off the ground. Assessment began when the subject closed their eyes. Testing with open eyes during the unipedal stance test was excluded as the effect of exercise on stabilometry has been shown to last only for a few minutes after cessation of the activity (Nardone et al., 1998). The duration of the test had to be limited. Further, removal of visual feedback may place more emphasis on peripheral proprioceptive input (Day, Steiger, Thompson, & Marsden, 1993). Toe touches

Fig. 1. Assessment of unipedal stance.

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a measurable change in postural sway. Reliability for the distance of the forward lunge has been documented as high (RZ0.93)(Rose & McKillop, 1998), therefore, change of 1% was taken as clinically significant for the purposes of this study. Mann-Whitney U tests were used to determine whether a difference existed in the change of postural sway and lunge distance of subjects with previous ankle injuries (nZ20) and the group of subjects with previous knee injuries (nZ3). Individual linear regressions were calculated to assess the strength of associations between balance post-game and the variables of time since previous injury, perceived injury recovery, grade and position played.

3. Results

Fig. 2. Assessment of the forward lunge.

Immediately following the unipedal stance task, subjects performed the forward lunge task (Fig. 2). The subjects were instructed to lunge forward as far and as fast as possible with their left leg and then return to the starting position. Hands were placed wherever the subject felt comfortable. Three trials were completed, with a rest of up to 10 s allowed between trials. Assessment was repeated with the right leg. The dependent variables measured by the Balance Master were the distance of the lunge as a percentage of subject’s height, contact time of the lunging leg on impact (seconds) and impact force as a percentage of subject’s body weight. 2.4. Statistical analysis Data were entered into MS Excel 2000 spreadsheets and were copied to SPSSe version 10.1. The data were explored for normal distribution prior to undertaking parametric analyses. For descriptive purposes, a ‘pathological value’ was defined as being more than two standard deviations from the mean determined by Rose and McKillop (1998) for the 20–39 year age group, namely 3.18 sK1 for the postural sway. Two-tailed paired t-tests were conducted to determine differences in balance parameters before and immediately after the game (aZ0.05). Due to the relatively poor reliability found for the single leg stance with eyes closed (RZ0.50), Rose and McKillop (1998) had calculated that a minimum difference of 13.4% was needed to depict

Leg preference was left in 11 subjects, right in 15 subjects and one subject had no preferred preference. Nine subjects were from the premier grades, and 18 were from the senior grades. Of the 108 quarters played by the 27 players, eight were played as goal keeper, 19 as goal defence, 13 as wing defence, 18 as centre, 18 as wing attack, 22 as goal attack and 15 as goal shoot. Seventeen players played the entire game at one position, while ten players played two positions throughout the game. The 26 subjects had a total of 52 self-proclaimed past lower limb injuries. Only one subject had not incurred a lower limb injury. Fourteen subjects had incurred injuries on their preferred leg only, eleven had bilateral injuries, and one subject had injuries on the non-preferred leg only. Ankle sprains accounted for 55.8% of all injuries, followed by knee injuries (19.2%), shin and calf injuries (13.5%) and other foot and ankle injuries (11.5%). Twenty-one subjects (77.8%) had incurred previous ankle sprains. These had occurred bilaterally in 10 subjects, of the preferred leg only in 10 further subjects, and one subject had incurred an ankle sprain of the non-preferred leg only. Reported time since injury and self-perceived recovery of the injury are described in Table 1. Of the injuries, 57.7% had occurred more than 12 months previously, and 55.8% had recovered by more than 90%. 3.1. Bilateral comparison The means and standard deviations for the forward lunge and unipedal stance parameters are shown in Table 2. Before the game, postural sway was slightly lower whilst standing on the preferred leg than on the nonpreferred leg, although this did not reach statistical significance (pZ0.059). After the game, no significant difference was found when comparing the postural sway means of either leg (pZ0.842). No statistically significant differences were found between the parameters of the preferred and non-preferred legs measured during the forward lunge.

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Table 2 MeansGSD of dependent variables from balance assessment pre- and post-netball game (nZ27) Dependent variables Postural sway, preferred leg (8 s ) Postural sway non-preferred leg (8 sK1) Distance lunged, preferred leg (% of height) Distance lunged, non-preferred leg (% of height) Impact force, preferred leg (% of weight) Impact force, non-preferred leg (% of weight) Contact time, preferred lunging leg (s) Contact time, non-preferred lunging leg (s) K1

Pre-game mean

Post-game mean

Change (%)

p-value

1.87G0.70 2.06G0.65 56.22G5.28 56.22G5.86 31.56G6.11 32.11G7.47 0.90G0.24 0.88G0.23

2.26G0.81 2.29G0.82 53.56G6.03 53.56G5.82 32.19G8.68 32.48G8.53 0.89G0.23 0.88G0.26

26.43G42.35 15.34G41.02 K4.80G5.06 K4.68G4.98 2.20G20.06 2.25G19.22 K1.86G12.17 K1.96G10.65

0.005* 0.138 0.00* 0.00* 0.624 0.765 0.264 0.485

*p!0.05.

3.2. Single-leg stance The average postural sway during preferred unipedal stance significantly increased post-game compared to pregame (Table 2). However, the change in postural sway on the non-preferred leg was not significant. H1 was therefore supported for the preferred leg only. The large standard deviation in postural sway of both legs indicate wide individual responses (Table 2). No significant difference was found for these changes in subjects with injuries of the preferred leg and those with bilateral injuries. Table 3 shows that postural sway on the preferred and the non-preferred leg increased more in the group of subjects who had sustained a previous ankle sprain than in subjects with previous knee injuries, although this did not reach statistical significance. Although the postural sway increased in most subjects post-game, it decreased by more than 13.4% on the preferred leg in four subjects and on the non-preferred leg in five subjects, indicating improved balance abilities after the game in 16.7% of the legs tested. Postural sway increased more than 13.4% in fourteen subjects (51.9%) on the preferred leg, and in nine (33.3%) on the non-preferred leg. It therefore increased by more than the minimum required change in 42.6% of the legs tested. Of these, the sway increased bilaterally more than 13.4% in only four subjects. 3.3. Forward lunge The average distance of the forward lunge decreased significantly for both legs during the game (Table 2), partly supporting H2. The average decrease in distance lunged was approximately 4.5 cm for both legs. No statistically

significant differences were found for pre- and post-game impact force or contact time of the lunge, partly rejecting H2. There was a trend for the relative distance of the lunge to decrease more in subjects with previous knee injury than in those with ankle injury (Table 3), however, this difference did not reach statistical significance. There were no significant correlations between either postural sway, distance of lunge, contact time of lunge or impact force of lunge post-game and the individual independent variables of perceived injury recovery, time since injury, grade or position. H3 was therefore rejected for these independent variables. 3.4. Individual responses Responses were individual-specific, with no consistent trend being evident. Table 4 and Fig. 3 show characteristics of the subjects with either pre- or post-game postural sway measures within the defined ‘pathological’ sway measure of greater than 3.18 sK1. No clear pattern emerged with regards to their injuries, time since injury and perceived recovery.

4. Discussion The main findings from this study were that postural sway during unipedal stance of the preferred leg increased significantly and the lunge distance decreased bilaterally following a netball game, suggesting that balance may deteriorate during a netball game. However, the changes were individual specific and were not predicted by perceived recovery and time since injury. The greater increase of postural sway whilst standing on the preferred leg may reflect greater use of that leg during

Table 3 Rate of change in variables, as a percentage of pre-game values, comparing subjects with a previous ankle sprain to those without Variable

Ankle injury NZ20 MeanGSD

Knee injury NZ3 MeanGSD

p-value

Change in postural sway, preferred leg Change in postural sway, non-preferred leg Change in lunge distance, preferred leg Change in lunge distance, non-preferred leg

30.37G48.60 23.03G46.12 K4.26G5.28 K4.80G4.38

16.49G11.11 K1.80G6.25 K8.18G7.29 K6.48G8.33

0.855 0.121 0.386 0.891

N. Waterman et al. / Physical Therapy in Sport 5 (2004) 200–207 Table 4 Characteristics of individual players with some postural sway measures within the ‘Pathological’ range Subject no.

Injuries

Self-reported time since injury

Self-perceived recovery

5

Bilateral ankle sprains Bilateral ankle sprains

Both within 3–12 months

Both legs: 50–75% 50–75%

14

16

Bilateral ankle sprains; preferred leg knee meniscus injury

21

Preferred leg ankle sprain Preferred leg ankle sprain

25

Preferred leg: 2 weeks earlier Non-preferred leg: O12 months All injuriesO12 months

O90% 100%

O12 months

O90% O90%

O12 months

O90%

O12 months: more than 12 months ago.

play, with possible changes in neuromuscular function. Other studies investigating balance assessment parameters following exercise have used mainly symmetrical movement such as walking and running (Derave, De Clercq, Bouckaert, & Pannier, 1998; Derave, Tombeux, Cottyn, Pannier, & De Clercq, 2002; Hashiba, 1998; Lepers et al., 1997; Nardone et al., 1997, 1998; Rowe et al., 1999; Seliga, Bhattacharya, Succop, Wickstrom, Smith, & Willeke, 1991). Rowe, Wright, Nyland, Caborn, & Kling, (1999) found mediolateral deflection was statistically significant following cheerleading practise, but not anteroposterior deflection. Similar significant results for mediolateral centre of pressure following walking and running on a treadmill were found by Derave et al. (1998). Nardone et al. (1998) found that both the sway area and the sway path were statistically significant after uphill treadmill walking. Hashiba (1998) found the mean displacement of fore-back postural sway from a neutral standing position was significantly higher after seven minutes of treadmill walking or running, but not after seven minutes of natural running. Although results of these studies showed changes in balance

Fig. 3. Postural sway pre- and post-game of subjects displaying at least one measure within the ‘pathological’ range above 3.18 sK1.

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parameters after exercise, the different types of exercise, duration and intensities of exercise, and different equipment used make it difficult to directly compare balance changes pre- and post-exercise with the current study. Toe touches were allowed during the unipedal stance test, as in previous studies (Berg, Maki, Williams, Holliday, & Wood-Dauphinee, 1992; Derave et al., 2002; McGuine et al., 2000). Allowing toe touches with balance assessment is controversial, however, it is thought that eliminating touchdowns from the data might remove the balance component that the clinician is attempting to measure (Palmieri, Ingersoll, Stone, & Krause, 2002). Indeed, Goldie et al. (1989) found that 42 out of 56 trials of unipedal stance with eyes closed on the preferred leg and 53 out of 56 trials of unipedal stance with eyes closed on the non-preferred leg were disturbed due to toe touching of the non-weightbearing leg. For the purposes of this study, it was paramount to complete the assessment within the shortest period possible to decrease the possibility of recovery of balance following the game. Disqualifying tests where toe touches were performed would have increased the testing duration. This study found that the bilateral decrease of average distance of the forward lunge post-game was statistically significant, and amounted to an average decrease in distance of 4.5 cm. This may be an adaptation to fatigue, possibly providing greater stability and better balance, and reducing the potential risk of injury by decreasing the momentum. Alternatively, it may be an adaptation to the netball game, where the subject decreases the length of the lunge for better performance on the netball court and this alteration in neuromuscular programming may have remained during post-game testing. The actual effect that the decrease in lunge distance has on performance or on injury risk is not known. Force impact and contact time of the lunging leg were not significantly different post-netball game. This may mean that the decrease in lunge length may have provided sufficient stability in the fatigued state that force impact and contact time of the lunging leg remained unaltered. It is unlikely that the changes found during testing postgame were due primarily to a learning affect of the unipedal stance or forward lunge. With practice, it would be expected that postural sway would decrease and subjects would be able to lunge further (as per instructions ‘to lunge forward as far and as fast as you can’). The opposite results were found for the mean sway velocity in this study. However, postural sway decreased by more than 13.4% in 16.7% of legs tested, showing an improvement in balance during single leg stance. A learning effect could therefore have occurred in these subjects. The role of changes in balance parameters as risk factors for injury in netball players is not yet known. In this study the self-reported site of injury, perceived recovery and time since injury could not be used to predict pre- and post-game values in balance parameters.

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These findings support those of Holder-Powell and Rutherford (2000) who found no relationship between impaired balance performance and type of musculoskeletal injury and time since injury. In the current study, a trend was evident that subjects with ankle injuries were more likely to have increased postural sway post-game than subjects who had incurred knee injuries. The latter group had a greater chance of a decreased lunge distance than the subjects with ankle injuries. Findings by O’Connell, George, and Stock (1998) that no differences in postural sway in a group of subjects with anterior cruciate ligament insufficiency and a group of asymptomatic subjects would support this trend. However, a larger group of subjects would be needed to confirm this observation. Due to the large standard deviation and ranges of parameters pre- and post-game, a clinical implication of our results would be that each player would need to be assessed individually. Although the change in postural sway on the preferred legs was small (a mean increase of 0.398 sK1), this amounted to a rate of increase of 26.4%. Testing before a game or within a clinic would not predict balance abilities on the court nor after a game. As testing equipment is normally not available at the courtside, clinical tests could be used, such as the Balance Error Scoring System (BESS) (Riemann, Guskiewicz, & Shields, 1999). This test makes use of a battery of three progressive stance variations (double, single, and tandem) on two different surfaces (firm and foam). Number of errors, such as opening eyes, stepping, or lifting the forefoot or heel, are counted whilst the athlete maintains the stance for 20 s. This system has been shown to correlate well with assessment of postural sway conducted on the Balance Mastere (Riemann, Guskiewicz, & Shields, 1999). McGuine et al. (2000) found that in a cohort of basketball players, an increased postural sway significantly increased risk of subsequent ankle sprains. As the present study was a cross-sectional study that included only one uninjured player, findings cannot be used to draw conclusions with regards to risk of injury and increased postural sway or changes in lunge parameters. Further, the clinical significance of changes in balance should be investigated, for example, the amount of change required to increase injury risk and affect performance. A prospective study including a larger cohort of players may provide more information with regards to the effect of different injuries on balance and functional movements.

5. Conclusion The aim of this study was to determine whether active participation in a netball game affects parameters of balance in premier and senior players. Average postural sway on the preferred leg deteriorated post-game and distance of lunge shortened bilaterally, compared to pre-game values. However,

the changes were clinically small and individual specific, and were not predicted by independant variables of self-reported previous injury, perceived recovery of injury, time since the injury. Individual assessments of balance and functional movement would be necessary for netball players, and it may be recommended that this assessment also be performed immediately after activity if impaired balance might be present.

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