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The influence of playing position on the biomechanical demands of netball match-play
Summary.
Netball is an intermittent team sport with specific positional roles, dictated by rules which
restrict activity to certain zones within the court. Each of the seven positions therefore has
specific technical and physical demands, with implications for the physical response to
match-play. GPS-mounted accelerometers provide a contemporary and non-invasive means
of quantifying body load on court, and our results showed that playing position did influence
body load. The Center was exposed to the greatest load, and in each movement plane,
reflecting their technical and tactical remit on court. Consistently the Goal Keeper and Goal
Shooter had the lowest load. There was equal contribution from medio-lateral and anterio-
posterior load, reflecting the multi-directional nature of netball. Given the emphasis on jump
landings and sudden decelerations, netball presents a high risk of injury to the ankle and
knee, reflecting epidemiological observations. The position-specific loading should
influence conditioning and injury prevention strategies.
Author Information:
Kim Fish, Matt Greig PhD,
Sports Injuries Research Group, Dept. of Sport & Physical Activity,
Edge Hill University, St Helens Road, Ormskirk, Lancs L39 4QP, United Kingdom
Corresponding Author: Dr Matt Greig: Tel: (+44) 01695 584848
Fax: (+44) 01695 584812
E-mail: [email protected]
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The influence of playing position on the biomechanical demands of netball match-play
Abstract
Background: Netball is an intermittent and multi-directional team sport, played on a
relatively small court. Rules restrict movement of certain positions within the court, and as
such each of the seven positions has a unique physical, technical and tactical remit. The aim
of the present study was to investigate the influence of playing position on mechanical
loading during netball match-play. Methods: Twenty female collegiate netball players (age
= 20.1 ± 1.5 years, height 1.71 ± 0.08m, weight = 65 .02 ± 8.27 kg) were analysed over nine
competitive matches. Each player wore a GPS device, with tri-axial accelerometry sampled
at 100Hz. Body load was standardised for time on court, and quantified in each movement
plane. The relative contributions of each planar vector to total accumulated body load were
also quantified for each position. Results: There was a significant (P < 0.01) main effect for
playing position on total load, with the Center exposed to the greatest load (13.7 ± 1.8
au·min-1) which was significantly higher than all other positions. The Goal Shooter was
exposed to the lowest load (6.2 ± 1.4 au·min-1), significantly lower than all other positions
except GK. This pattern was evident in each of the planar directions. The relative
contribution of each movement plane to total body load did not vary between positions, at ~
25:27:47 % for anterio-posterior : medio-lateral : vertical load. Conclusions: The physical
and technical demands of each position altered the magnitude of mechanical loading during
match-play. The equivalence in medio-lateral and anterio-posterior loading reflects the
multi-directional activity profile, with implications for injury prevention and performance
enhancement.
Key Words: netball, load, injury, force, GPS
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INTRODUCTION
Netball is played on a 30.5 x 15.25 m court, over four 15 minute quarters, with a team
comprising seven players. The intermittent, multi-directional and irregular activity profile is
further complicated by specific rules, with court restrictions determining which areas of the
court in which each position can operate. The seven different positions comprise center court
(C, WA, WD), shooters (GA, GS) and defenders (GK, GD). Each position therefore has
unique physical demands in addition to the technical and tactical remit within the team (1),
reflected in position-specific anthropometric characteristics (2). Time motion analyses have
reported that the center position (C) covers a greater total distance than the goal-keeper (GK)
and goal-shooter (GS) positions (3,4), however only these three positions were considered.
The technical and tactical demands of each position, and the relatively small court size, are
also likely to influence movement patterns beyond gross measures such as distance covered.
Technical elements such as stride length and stride frequency will also differ between
positions (3). The intermittent and multi-directional nature of netball, allied to the small
court size, places a high demand on acceleration, change of direction, and landing mechanics.
Netball imposes a footwork rule which further increases the complexity of the biomechanical
demands, with players required to decelerate fully to a landing position with one step. These
movement requirement increases the risk of injury (5,6), particularly in female athletes (7),
and epidemiological research has consistently reported the ankle and knee as the primary
sites of injury in netball (2,8,9). The mechanical demands of netball are therefore important
for both performance enhancement and injury prevention, with these demands likely to be
position-specific.
The accelerometer function of GPS-mounted technologies provides a contemporary and
innovative means of obtaining biomechanical data on court. Accelerometers have been
reported to have good reliability in the measurement of biomechanical load (10) and have
been used in numerous team sports (11,12). The tri-axial function of the accelerometer
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enables three-dimensional data to be collected at high frequency during match-play,
providing a measure of movement quality. This approach has been used recently to
investigate the influence of playing standard (13), with higher standard players exposed to
greater load. In our study it is hypothesised that the technical and tactical demands of each
position will influence measures of biomechanical load, with the Center (C) position exposed
to the greatest load, reflecting the distance covered. Our aim was to further investigate the
influence of playing position on the tri-axial contributions to load, with implications for
optimising training and (p)rehabilitation regimes.
MATERIALS AND METHODS
To participate in the study players were required to have no injury history in the lower limb
for the previous three months, neurologic or balance disorder or chronic ankle instability as
determined by the Cumberland Ankle Instability Tool. Twenty female collegiate netball
players (age = 20.1 ± 1.5 years, height 1.71 ± 0.08m, weight = 65 .02 ± 8.27 kg) with a
minimum two training sessions and one match per week completed the study. All players
provided written informed consent in accordance with the departmental ethical procedures
and following the principles outlined in the Declaration of Helsinki.
Experimental Design
Competitive matches played at the host institution (to standardise playing surface) were
analysed during the 2013/14 season. Playing positions were classified as goal-keeper (GK),
goal-defence (GD), wing-defence (WD), center (C), wing-attack (WA), goal-attack (GA),
and goal-shooter (GS). Data was collected on all players, including substitutes, over nine
matches using a commercially available GPS unit (MinimaxX S4, Catapult Innovations,
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Melbourbe, Australia) located at the upper back and contained within a vest worn underneath
the netball dress.
Tri-axial accelerometer data was sampled at 100Hz, to calculate accumulated body load (10)
in each of the sagittal, frontal and transverse planes throughout each match. Time on court
for each player was also determined, to enable load to be standardised for playing time and
thus reported in arbitrary units (au·min-1). The relative contributions (%) of each movement
plane to total body load were also determined.
Statistical Analysis
The absolute and relative (as a percentile contribution to total load) load in each of the three
movement planes are reported as mean + SD, with significance set at P ≤ 0.05. Repeated
measures ANOVA was used to investigate the influence of playing position for each variable.
All statistical analysis was completed using PASW Statistics Editor 18.0 for windows (SPSS
Inc., Chicago, USA).
RESULTS
There was a significant (P < 0.01) main effect for playing position on total accumulated body
load (Figure 1). Playing position C exhibited the greatest total load (13.7 ± 1.8 au·min-1),
which was significantly higher than all positions. GS was exposed to the lowest load (6.2 ±
1.4 au·min-1), significantly lower than all other positions except GK.
** Insert Figure 1 near here **
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Figure 2 summarises the influence of playing position on accumulated load in each of the
planar vector directions. Body load in the sagittal plane, representing accelerations in the
anterio-posterior direction, also exhibited a significant main effect for playing position (P <
0.01). C displayed the highest sagittal plane load (3.4 ± 0.5 au·min-1), significantly higher
than all other playing positions. GS presented the lowest score (1.7 ± 0.5 au·min-1),
significantly lower than C, GD and WA.
Body load in the frontal plane, representing acceleration in the medio-lateral direction,
exhibited a similar pattern of position-specific loading (P < 0.01), with C (3.9 ± 0.5 au·min-1)
again exhibiting the highest values. The medio-lateral load for C was significantly higher
than for all other playing positions except WA. GS and GK exhibited the lowest medio-
lateral load, significantly lower than all other positions.
The greatest loads were exhibited in the transverse plane, reflecting vertical accelerations. A
similar pattern was observed with a significant main effect for playing position (P < 0.01).
Again C exhibited the highest load (6.4 ± 0.9 au·min-1), and GS the lowest load (2.7 ± 0.6
au·min-1), with GS significantly lower than all position except GK.
** Insert Figure 2 near here **
Given the consistency in the pattern of positional influence on each directional load, the
relative planar contributions to load showed no significant main effect for playing position.
The average relative contributions of the anterio-posterior, medio-lateral and vertical
directions to total load were ~ 25:27:47 (Figure 3).
** Insert Figure 3 near here **
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DISCUSSION
The aim of our study was to examine the influence of playing position on body load during
netball match-play, utilising GPS-mounted tri-axial accelerometry to quantify load. The
observation that the Center (C) exhibited the greatest total body load supports time motion
analyses (3,4,13,14). This positional influence on mechanical load was observed in each of
the three planar vectors. C is the most operational player on the court, and has a higher
workload than other positions as they are able to operate in all thirds of the court, with the
fewest restrictions on court coverage. Our findings also support notational observations that
GD and WA are the next most active (4). The high accumulated body loads reflect that the
C has a technical and tactical requirement to always be involved in the passing schedule as an
offer, or back-up offer, which predictably will mean more running, more distance covered
and more work done (3,4,14,15). The technical nature of GD & WA, suggest that the high
body loads are down to position specific activity, rather than the constant ‘running’ nature of
C. The technical demands of each position vary, and as such their activity profile and
locomotion characteristics will vary. A high load could be obtained by covering a great
distance, or by covering shorter distances but at higher intensity, or with increased emphasis
on high acceleration landings during marking and rebounding for example.
WA has a similar technical and tactical remit to C, however can only operate in two thirds of
the court (minus the shooting circle). The WA role is fundamentally the lead attack for the
team, incorporating a variety of attacking manoeuvres, including dodging, changing direction
and short, rapid sprints (6). These technical requirements, despite the smaller playing area,
result in a high accumulated body load in comparison with other positions. In contrast, GS
and GK only operate in one third of the court and thus the movements will be limited and the
distance covered will be shorter (3,4,14). When the ball does reach the goal circle, the actions
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completed by GS and GK in shooting and marking requirements often involve the player
being stationary.
The positional influence on accumulated body load is naturally affected by the tactical
coupling of certain positions, for example GD marks GA, and GK marks GS. Their court
restrictions, and activity patterns in the game are therefore largely matched. However, the
defending player (GD, GK) exhibited greater load than their directly opposing attacking
player (GA, GS). The higher load in defending positions reflects notational observations
(3,8), with the defender reacting to the movement of the attacker and trying to restrict scoring
and receiving opportunities. Even if the attacker remains stationary the defender will be
required to move around their opponent to prevent the attacker from receiving the ball (3).
The position-specific nature of the movement demands is likely to influence the injury risk to
each player. Despite the greater load exposure to C, injury incidence is higher for GD (8).
The emphasis on multi-directional landings and pivoting during technical skills increases the
biomechanical load on the lower extremities and prolonged, frequent occurrence of this
action will increase the risk of injury (16). The small court size, further exacerbated by zone
restrictions for different positions, and the multi-directional activity profile create a unique
movement pattern. The planar contributions to total body load (anterio-posterior : medio-
lateral : vertical) revealed a 25:27:47 ratio. Whilst previous research is limited in this area,
these values are comparable with previous studies of netball match-play (13) but differ
considerably from an equivalent 36:14:50 ratio in soccer match-play (17). Soccer shares
many activity profile characteristics in being intermittent, multi-directional, and irregular.
The anterio-posterior contribution in soccer is far greater than in netball match-play, with a
much more balanced contribution between medio-lateral and anterio-posterior load in netball.
These differences reflect the variations in playing area, and highlight the specific movements
carried out in each sport, and by each position. GK was unique in having a greater percentile
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contribution from anterio-posterior than medio-lateral, whereas C and WA had significantly
greater contribution from medio-lateral load than anterio-posterior. These observations
highlight the specific technical roles and the mechanical demands of those position-specific
skills sets.
Jumping, and subsequently landing, is a fundamental skill in netball and has been associated
with a high risk of injury, particularly in female sports (7). Netball landings often follow a
caught pass (14,18) and the technical element negates the opportunity for controlled landings,
with the jump executed within the context of the game. The takeoff and landing will often
include a change of direction, with coincident plantar flexion and inversion of the ankle and
genu valgum of the knee increasing the risk of injury (19,20). The Center court players (C,
WA & WD) will exhibit different technical jumps to the shooters and defenders because of
their activity profile, and players who have access to the Center third (C, WA, WD, GA &
GD) complete more landings (4) than the players who don’t (GS & GK). The mechanical
load, and in particular the planar contributions to load, will have implications for the
incidence, type, and site of injury. These findings should also guide the development and
modification of conditioning and prehabilitation regimes.
Tri-axial accelerometry using commercially available GPS micro-technologies was able to
differentiate between playing positions during netball match-play, and substantiated
notational analyses. Combining notation with GPS analysis would further enhance our
understanding of the mechanical demands of netball. Individual skills could be subjected to
further biomechanical analysis to quantify joint loading, but this would detract from the
ecological validity provided by match-play analysis. To further investigate the specific injury
risks of match-play, the location of the GPS device (or accelerometer) could be changed, to
provide site-specific data. The apparent coupling of workload between directly opposing
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positions, and the different mechanical loading of each position should influence position-
specific training regimes.
CONCLUSION
GPS-mounted tri-axial accelerometry provides an appropriate means of quantify mechanical
load during netball match-play. The rules of the game, and the different technical/tactical
remit of each position on court creates a position-specific pattern in mechanical load. The
Center was subjected to the greatest load, and this was evident in all movement planes, with
implications for performance enhancement and injury prevention. The Goal Keeper and Goal
Shooter exhibited the lowest load, reflecting notational analyses. The coupling of positions
on court, and the position-specific pattern of load, should guide the development and
modification of condition and prehabilitation regimes.
The parity between medio-lateral and anterio-posterior load reflects the multi-directional
nature of the sport, further increasing the complexity of the mechanical demands and
indicative of an injury epidemiology centred at the ankle and knee joints. Further research
should consider the potential for directly quantifying joint loading during match-play.
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LEGENDS TO FIGURES
Figure 1. The influence of playing position on total accumulated body load.
Figure 2. The influence of playing position on accumulated body load in each movement
plane.
Figure 3. The influence of playing position on the planar percentile contributions to total
load.
GK GD WD C WA GA GS4
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Position
Accu
mul
ated
Load
(au/
min
)
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GK GD WD C WA GA GS0
1
2
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7
Anterio-PosteriorMedio-LateralVertical
Position
Accu
mul
ated
Load
(au/
min
)
GK GD WD C WA GA GS0%
25%
50%
75%
100%
26.8 24.9 23.5 24.9 23.4 26.7 27.3
25.4 26.7 25.9 28.8 28.6 27.6 28.5
47.8 48.4 47.4 46.3 48.0 45.7 44.2
VerticalMedio-LateralAnterio-Posterior
position
13
1
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