University of Groningen
The interaction between wheelchair configuration and wheeling performance in wheelchair
tennis
Rietveld, Thomas; Vegter, Riemer J K; der Woude, Lucas H V; de Groot, Sonja
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Sports biomechanics
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10.1080/14763141.2020.1840617
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Rietveld, T., Vegter, R. J. K., der Woude, L. H. V., & de Groot, S. (2021). The interaction between wheelchair configuration and wheeling performance in wheelchair tennis: a narrative review. Sports biomechanics, 1-22. https://doi.org/10.1080/14763141.2020.1840617
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The interaction between wheelchair configuration
and wheeling performance in wheelchair tennis: a
narrative review
Thomas Rietveld , Riemer J. K. Vegter , Lucas H. V. der Woude & Sonja de
Groot
To cite this article: Thomas Rietveld , Riemer J. K. Vegter , Lucas H. V. der Woude & Sonja de
Groot (2021): The interaction between wheelchair configuration and wheeling performance in wheelchair tennis: a narrative review, Sports Biomechanics, DOI: 10.1080/14763141.2020.1840617 To link to this article: https://doi.org/10.1080/14763141.2020.1840617
© 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
Published online: 12 Jan 2021.
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The interaction between wheelchair configuration and wheeling
performance in wheelchair tennis: a narrative review
Thomas Rietveld a, Riemer J. K. Vegter a,b, Lucas H. V. der Woude a,b,c
and Sonja de Groot a,d,e
aUniversity of Groningen, University Medical Center Groningen, Center for Human Movement Sciences, The Netherlands; bPeter Harrison Centre for Disability Sport, School of Sport, Exercise & Health Sciences,
Loughborough University, Loughborough, UK; cCenter for Rehabilitation, University Medical Center Groningen, Groningen, The Netherlands; dAmsterdam Rehabilitation Research Center Reade, Amsterdam, The Netherlands; eDepartment of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, VU University, Amsterdam, The Netherlands
ABSTRACT
The number of wheelchair tennis players is rising internationally, yet from a scientific perspective little is known about wheelchair tennis performance. Wheelchair tennis is more complex compared to other wheelchair court sports, due to the wheelchair/racket interaction. The purpose of this narrative review was to gain insight into the influence of wheelchair configuration, i.e., the individual set-up of a wheelchair, on wheelchair tennis performance, more specifically on wheelchair mobility performance and propulsion technique. Wheelchair propul-sion while holding a racket has had little attention in both the wheel-chair mobility performance and wheelwheel-chair propulsion technique area. It is shown that the propulsion technique and wheelchair mobility performance are negatively affected by the racket. Based on the current literature, the influence of wheelchair configuration on wheel-ing performance in wheelchair tennis can mainly be described from a broader wheelchair court sport perspective, due to the lack of specific publications about wheelchair tennis. In the future more research should be conducted on wheeling performance and wheel-chair configuration in wheelwheel-chair tennis, to attain a more proper scientific foundation for optimising wheelchair tennis performance.
ARTICLE HISTORY
Received 28 July 2020 Accepted 18 October 2020
KEYWORDS
Wheelchair sports; mobility performance; propulsion technique; wheelchair-user interaction; sports wheelchair
Introduction
Since wheelchair tennis became part of the Paralympic games in 1992, its popularity is rising
(Gold & Gold, 2007). Nowadays wheelchair tennis is part of all four Grand Slams, like
Wimbledon and the Australian Open (ITF Tennis, 2016). Abled-bodied tennis already
consists of various challenging components like the small ball, the rascket, court surface- type and dimensions and opponent(s). The rules of wheelchair tennis are almost identical to the able-bodied variant, with the ‘two-bounce rule’ being the only exception (ITF Tennis,
2016). Another important difference between abled-bodied tennis and wheelchair tennis is
the addition of the wheelchair, as a result all playing actions originate from the upper body.
CONTACT Thomas Rietveld t.rietveld@umcg.nl
https://doi.org/10.1080/14763141.2020.1840617
© 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any med-ium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.
Wheelchair tennis performance is defined by the characteristics of the player, such as the tennis skills, talent and training status, in combination with the wheelchair config-uration (e.g., frame, seating, wheels, hand rim) and playing environment (e.g., court-
surface, indoor/outdoor) (Figure 1). From a wheelchair tennis athletes’ perspective,
wheelchair tennis performance will be expressed in both wheeling performance and tennis performance. The current paper focusses solely on wheeling performance, which compromises both wheelchair mobility performance and propulsion technique.
Manual wheelchair propulsion itself is a difficult task to perform, because the hands need to be coupled to the rotating rim of an already moving wheel, partly outside the visual field
(De Groot et al., 2008; Vegter et al., 2014, 2015). Wheelchair propulsion technique is defined
as the delivery of power to the hand rim of the wheelchair. This propulsion power is often described by bi-manual push and power kinetics (i.e., forces, moments, work) characteristics. Important wheelchair propulsion technique variables include, amongst others, the contact angle, negative work per cycle, net-work per cycle, frequency (push/min) and power output; these characteristics can only be measured and calculated from an instrumented wheel and its
torque signal (Figure 1) (Van der Woude et al., 1997; Vegter et al., 2014).
Propelling a wheelchair while playing tennis is an even more difficult task because the racket is held when pushing with the hands onto the hand rim. The addition of a racket reduced the maximum velocity and distance covered during the first three pushes (Goosey-
Tolfrey & Moss, 2005). Moreover, when tested on an instrumented wheelchair ergometer, the
hand holding the racket has more negative power when (de)coupling the hand with the racket Figure 1. Conceptual model of wheelchair tennis performance.
to the rim. This results in higher peak and mean power output over a shorter push-time, to
compensate for this negative power in order to go straight forward (De Groot et al., 2017).
The higher peak power output during wheelchair propulsion of the hand holding the racket might lead to higher mechanical loads in the upper extremity.
The combination of a wheelchair and a racket makes wheelchair tennis different from other wheelchair court sports, such as wheelchair rugby or basketball, where all athletes rely heavily
on their mobility to perform the game. To that end, De Witte et al. (2018) defined wheelchair
mobility performance as the ability or inability of a person with a wheelchair on court. Main components of wheelchair mobility performance concern typical athletic behaviours like
sprinting, braking and turning (De Witte et al., 2018). Wheelchair mobility performance
can be investigated with the use of the end-times on sprint tests, acceleration/deceleration tests, and manoeuvrability tests. However, more detailed on court information can also be
gathered with the use of inertial measurement unit (IMU) or indoor tracking systems (Figure
1) (Mason et al., 2014; Rhodes et al., 2014; Van der Slikke et al., 2015, 2016, 2017).
Wheelchair mobility performance and propulsion technique are both influenced by the
configuration of the wheelchair (Vanlandewijck et al., 2001). During wheelchair propulsion
there are high mechanical loads on the upper extremity as a consequence of environmental conditions, wheelchair mechanics and individual characteristics and behaviour, so-called
Newell’s task constraints (H. E. J. Veeger et al., 2002; Van der Woude et al., 2001). To diminish
these mechanical loads and optimise the match performance, the athlete, the wheelchair and the wheelchair-athlete interface all need to interact in the most optimal way (Mason et al.,
2013; Medola et al., 2014; Van der Woude et al., 2001). The optimal configuration of
a wheelchair, together with training and changes in propulsion technique can influence these mechanical loads. Wheelchair configuration is defined as the arrangements of the parts of a wheelchair, stated differently, the individual set-up of the wheelchair (Mason
et al., 2013). From an ergonomics perspective, these can be summarised in the wheelchair
mechanics and the wheelchair-user/athlete interface (Van der Woude et al., 1986, 1989, 2001).
Small changes in the wheelchair configuration can already influence wheelchair mobility performance and propulsion technique through the different outcome measures, such as the
acceleration, forces, and power output (Mason et al., 2013). The current review is inspired by
the review of Mason et al. (2013), with a narrower focus on wheelchair tennis, given the more
complex wheelchair–athlete interface interaction a wheelchair tennis player has to face because of the racket.
The purpose of the current narrative review is to gain insight into the influence of wheelchair configuration on wheelchair tennis performance, more specifically, wheelchair
mobility performance and propulsion technique (Figure 1). It was hypothesised that
wheel-chair configuration can have a substantial influence on wheelwheel-chair mobility performance and propulsion technique in (elite) wheelchair tennis. An overview will primarily be given from a wheelchair mobility performance and propulsion technique perspective, followed by some future recommendations.
Methods
Search strategy & quality assessment
A literature search was conducted in the databases of PubMed and Web of Science. A combination of the following key words was used: ‘wheelchair mobility performance’,
‘wheelchair skill’, ‘wheelchair configuration’, wheelchair propulsion (technique)’, ‘wheelchair field’, ‘wheelchair sport(s)’, ‘wheelchair tennis’, ‘wheelchair rugby’ and ‘wheelchair basket-ball’. Articles were included when effects of wheelchair configuration on wheelchair mobility performance or wheelchair propulsion technique in wheelchair court sports was investi-gated. Articles were excluded based on the irrelevance for wheelchair tennis, use of wheel-chair racers, focus on abled-bodied research or focus on aerobic/anaerobic capacity. Only English written articles published until November 2019 were included in the final search.
A flow chart of the literature selection process can be seen in Figure 2. One article
investigated wheelchair mobility performance and wheelchair propulsion technique, leading to a total of 15 included papers.
The quality of the included articles was assessed with an adapted version of a checklist by
Webster et al. (2009), which earlier was adapted and used by Heyward et al. (2017). The reason
to assess the articles using this checklist was the unavailability of a standardised checklist for cross-sectional studies. In total 8 questions were used to investigate the methodological quality of the studies. For each question a score of 1, 0.5 or 0 could be given, representing adequate, partial adequate and inadequate, respectively. This eventually resulted in a maximum score of 8 points. No minimum scoring criteria was set due to the limited amount of papers available, yet study quality was considered in results information and conclusion.
Results
Wheelchair mobility performance
As previously mentioned, wheelchair mobility performance is defined as what an athlete is
able or not able to do with a wheelchair in the field (De Witte et al., 2018). Wheelchair
performance behaviours, like sprinting, braking and turning, either are observed on court
during matches or training sessions or evaluated in specific field tests (De Witte et al., 2018).
Most measurement devices used in the field are velocimeters and/or timing gates (Mason
et al., 2009; Mason, Van Der Woude, Lenton et al., 2012; Mason, Van Der Woude, Tolfrey,
Goosey-Tolfrey et al., 2012). Some advantages of field-based testing are the natural
environ-ment, the use of participants’ own sports wheelchair and the fact that the same surface is used
as during matches (Goosey-Tolfrey & Leicht, 2013). For standardisation purposes it was
recommended to also include coast-down testing as a part of the field testing protocol, to investigate what the potential influence of rolling resistance or power output (W) is on the
performance of the participants (Bascou et al., 2013, 2015; Lin et al., 2015; Sauret et al., 2012).
A new way to measure wheelchair mobility performance of a wheelchair athlete more in- depth and in a valid and reliable way, is the use of inertial measurement units (IMUs) (Van der
Slikke et al., 2015). Key kinematic variables describing wheelchair mobility performance in
wheelchair basketball are the average speed and acceleration and the average rotational speed
and acceleration of both wheels and the wheelchair frame (Van der Slikke et al., 2016). It is
unknown whether these are similar to the ones present in wheelchair tennis. In wheelchair tennis standardised field tests to measure wheelchair mobility performance with the use of
IMUs have also been developed and validated (Rietveld et al., 2019). These tests could be used
to study different consequences of wheelchair configuration on wheelchair behaviours.
Wheelchair propulsion technique
Wheelchair propulsion technique was already previously defined as the push and power characteristics of an individual. Wheelchair propulsion technique is mainly measured with the use of a treadmill or an ergometer in a lab setting. One of the advantages of lab-testing is in contrast to field-based testing, especially the potential high level of standardisation. With the use of lab-based testing, it is much easier to test people under exactly the same circumstances. Wheelchair propulsion on a treadmill is mechanically realistic, due to the natural form of
wheelchair propulsion with small steering corrections (Van der Woude et al., 2001). The
advantage of ergometer testing is the fact that testing conditions are highly reproducible and differences between left and right propulsion can be evaluated, which is essential in wheelchair
tennis due to the use of a racket during propulsion (Goosey-Tolfrey et al., 2018; De Groot et al.,
2017; De Klerk, Vegter, Goosey-Tolfrey et al., 2020; Van der Woude et al., 2001).
A disadvantage of an ergometer is the limited representability of the real game, no air friction is encountered, manoeuvrability cannot be mimicked, while body movement have a different effect on rolling friction and inertia.
Biomechanical parameters to measure wheelchair propulsion technique variables could also be measured in the field with the use of an instrumented measurement wheel
or IMUs (Cooper, 2009; Van der Slikke et al., 2015), which could be seen as an
advantage. A disadvantage of an instrumented measurement wheel is the relatively large mass (± 4 kg), which leads to a higher power output and negatively affects the
propulsion technique (De Groot et al., 2013). The use of IMUs is already validated
regarding measuring acceleration and angular velocity, but also for calculating
tem-poral parameters such as the cycle time and frequency (Van Der Slikke et al., 2016).
Quality of the articles
The quality of the articles investigating wheelchair configuration from a wheelchair
mobility performance perspective can be seen in Table 1 and from a propulsion
technique perspective can be seen in Table 2. The overall methodological quality of
the articles was moderate to good, meaning studies could be replicated. Overall the inclusion/exclusion criteria and reliability/validity aspects were mostly missing. Table 1. Methodological quality of articles investigating the effect of wheelchair configuration on wheelchair mobility performance in wheelchair court sports, adapted from Webster et al. (2009) and based on Heyward et al. (2017).
Participants characteristics Inclusion/ exclusion criteria stated Design appropriate to the research question Key depen-dent vari-ables measured Psychometric properties (reliability) Psychometric properties (validity) External validity of the results discussed Limitations of the study described Total score (0–8) Goosey-Tolfrey and Moss (2005) ++ – ++ ++ – – +– – 3.5 Haydon et al. (2019) ++ – ++ ++ +- – +– ++ 5 Mason et al. (2009) ++ – ++ ++ – – ++ +- 4.5 Mason et al. (2010) ++ +– ++ – – ++ ++ ++ 5.5 Mason, Van Der
Woude, Tolfrey, Goosey- Tolfrey (2012) ++ – ++ ++ – – ++ ++ 5
Mason, Van Der Woude, Lenton (2012) ++ – ++ ++ – – ++ +– 4.5 Mason et al. (2015) ++ – ++ +– – – ++ +– 4
Van Der Slikke et al. (2018)
++ – ++ ++ ++ – ++ ++ 6
T. T. J. Veeger et al. (2019)
++ – ++ ++ ++ ++ ++ – 6
Optimising wheelchair configuration
Configuration of a wheelchair can have effects on the wheelchair mobility performance of
a wheelchair athlete (Figure 3) (Mason et al., 2013). An overview of studies investigating
the effects of wheelchair configuration on wheelchair mobility performance in wheelchair
court sports is given in Table 3. The focus of these papers was on the examination of
different kinds of wheelchair configurations, to eventually improve the wheelchair mobility performance. When investigating different aspects of wheelchair configuration, it is important to only change the configuration and to keep all other factors that influence wheelchair mobility performance unchanged. Small changes in wheelchair configuration could already influence wheelchair mobility performance outcome
mea-sures (Mason et al., 2013).
The current literature on wheelchair mobility performance while holding a racket is scarce. Only one study has investigated wheelchair mobility performance in wheelchair
tennis using a tennis racket (Goosey-Tolfrey & Moss, 2005). With the addition of
a racket an extra constraint is added to the wheelchair-user interface, which will influence the wheelchair mobility performance. In the study of Goosey-Tolfrey and
Moss (2005) the differences between wheelchair propulsion with and without holding
a racket was investigated with the use of a 20-metre sprint test in the field. During the first three pushes, while holding a racket, the mean and peak velocity were reduced, while lesser distance (0.16 m) was covered. Also, the number of pushes to cover 20 metres increased, indicating shorter cycle times when holding the racket. It was also stated that in wheelchair tennis around 60% of the maximum velocity was achieved after the first three pushes, while in wheelchair basketball this value was around 80% of
peak velocity (Coutts, 1990; Goosey-Tolfrey & Moss, 2005). This already demonstrates
Table 2. Methodological quality of articles investigating the effect of wheelchair configuration on propulsion technique in wheelchair court sports, adapted from Webster et al. (2009) and based on Heyward et al. (2017). Participants characteristics Inclusion/ exclusion criteria stated Design appropriate to the research question Key depen-dent vari-ables measured Psychometric properties (reliability) Psychometric properties (validity) External validity of the results discussed Limitations of the study described Total score (0–8) De Groot et al. (2017) ++ – ++ ++ +- – +– ++ 5 De Groot et al. (2018) ++ – ++ ++ +– – +– ++ 5 Faupin et al. (2004) ++ – ++ ++ – +– ++ ++ 5.5 Faupin et al. (2013) ++ – ++ +- – ++ ++ ++ 5.5 Mason et al. (2011) ++ – ++ ++ – – ++ – 4 Mason, Van Der Woude, Tolfrey, Lenton (2012) ++ – ++ ++ – – ++ +– 4.5 Mason et al. (2015) ++ – ++ +– – – +– +– 3.5
the difficulty of wheelchair propulsion while holding a racket and the need for optimisation of the configuration of the wheelchair specifically for this sport.
An overview of studies investigating the effects of wheelchair configuration (Figure 3)
on wheelchair propulsion technique in wheelchair court sports is given in Table 4. The
focus of these papers is on the examination of different kinds of wheelchair configura-tions, to eventually improve the wheelchair propulsion technique.
There is unfortunately a lack of knowledge on wheelchair propulsion while holding a racket regarding wheelchair propulsion technique. De Groot et al.
(2017) gave a more detailed description of the propulsion technique while holding
a racket. For this study, wheelchair tennis players were tested with and without a racket during submaximal and sprinting tests on a wheelchair ergometer with and without a racket to investigate the difference in biomechanical parameters. The propulsion technique was definitely altered during the submaximal tests with the addition of a racket. Due to the power losses before and after the push, the participant needs to compensate these typical power losses to equate external power requirements, producing more positive power during the effective part of the push, in order to go straight forward and maintain the speed. Also, lower push times and shorter contact angles were found. In the sprinting test similar results were seen, meaning that both sprinting and submaximal propulsion negatively affected the propulsion technique by the addition of a racket. Authors suggested that on the long term, the ineffective propulsion technique might lead to injuries in the upper extremity due to the higher peak forces on the racket hand side.
To prevent injuries and optimise performance hand rims are being redesigned to improve the coupling and decoupling of the hand with the racket to the hand rim and
hopefully reduce the negative power output (De Groot et al., 2018; Koopman et al., 2016).
In the study of De Groot et al. (2018) a new squared-profile hand rim was tested and
compared to a regular hand rim. The same protocol was used as the previous study (De Figure 3. Wheelchair configurations of a typical wheelchair tennis chair, adapted from (Double
Table 3. Overview of articles investigating the effect of wheelchair configurations on wheelchair mobility performance in wheelchair court sports. Participants (n) Age (y) M/F Wheelchair Objective Study aspects Outcome measures Measurement device Results Goosey- Tolfrey and Moss ( 2005 ) WT (8) 34 (± 7) 8/0 Own chair Effect of racket on velocity of WP 12 x 20 m sprint v, d Velocometer v & d reduced by third push Haydon et al. ( 2019 ) WR (6) -6/0 Adjustable rugby chair Optimise wheelchair set- up 2x 5 m sprint, Illinois agility drill, skill test t, (rot) v, a IMUs, timing
gates, video analysis
Orthogonal design can be used to select near- optimal setup Mason et al. ( 2009 ) WR (10) 30 (± 5) 9/1 Own chair Influence of glove type 4x Acc drill, sprint drill and agility drill br, backward pulling, acc, v, t Velocometer & Timing gates Current choice of glove preferable, due to modification and adaptation Mason et al. ( 2010 ) WB (3), WR (3) & WT (3) 39 (± 5) 9/0 – Wheelchair configuration for optimal WMP
Performance indicators, Principal
and supplementary areas wheelchair configuration Interview – Stability important performance indicator, minor modifications affect performance Mason, Van Der Woude,
Tolfrey, Goosey- Tolfrey (2012
) WB (11) & WT (3) 23 (± 6) 11/3 Top End Transformer, Invacare Effect of rear-wheel camber 4x 20 m sprint, linear mobility, manoeuvrability (15/18/20/24°) t, br, v, acc, #pushes Velocometer & Timing gates 18° or 20° favourable for all aspects of linear and non-linear MP Mason, Van Der Woude, Lenton (2012 ) WB (13) 24 (± 7) 13/0 Top End Transformer Invacare Effect of wheel size 3x 20 m sprint, linear mobility drill, agility drill (24/25/27 inch) t, acc, #pushes Velocometer & Timing gates 26-inch wheels improved maximal sprinting performance Mason et al. ( 2015 ) AB (3) 28 (± 8) 8/0 RGK Quattro Effect wheel stiffness, tyre type, type orientation 8 x 20 m sprint t Timing gates New Spinergy wheels quicker acc, Equaliser better overall, no effect tubeless tyres (Continued )
Table 3. (Continued). Participants (n) Age (y) M/F Wheelchair Objective Study aspects Outcome measures Measurement device Results Van Der Slikke et al. ( 2018 ) WB (20) 30 (± 12) 13/7 Own chair Effect of grip, seat height and mass 15
activities (sprinting, braking,
turning, WB activities) t, rot (v), rot (acc) IMUs Distributed additional mass most effect on WMP T. T. J. Veeger et al. ( 2019 ) WB (60) 25 (± 9) 44/16 Own chair Improving WMP in WB 15
activities (sprinting, braking,
turning, WB activities) t Video analysis Focus on wheel size, hand-rim diameter, camber angle, vertical distance between shoulder and wheel axis; between seat height and footplate *WB = wheelchair basketball, WR = wheelchair rugby, WT = wheelchair tennis, AB = abled-bodied, br = braking, t = time, v = velocity, d = distance, ac = acceleration, rot = rotational, WMP = wheelchair mobility performance, IMU = inertial measurement unit
Table 4. Overview of articles investigating the effect of wheelchair configuration on wheelchair propulsion technique in wheelchair court sports. Participants (n) Age (y) M/F Wheelchair Objective Study aspects Outcome measure Measurement device Results De Groot et al. ( 2017 ) WT (8) 23 (± 6) 4/4 Adjustable chair Effect of racket on WP technique 3 x submax, 6 x sprint PO, W, v, Pt, Ct, Ca, fr Ergometer Racket has negative consequences on WP technique De Groot et al. ( 2018 ) WT (8) 23 (± 6) 4/4 Adjustable chair Effect of a squared profile rim on WP technique 3 x submax, 6 x sprint PO, W, v, Pt, Ct, Ca, fr Ergometer No differences between squared profile and regular rim on WP technique Faupin et al. ( 2004 ) WB (8) 25 (± 4) 8/0 Top End X-Terminator- type Effects of rear-wheel camber on the propulsion technique 3 x 8s max sprint PO, T, v, Ct, Pt, acc, F, Rt Ergometer (VP 100 HANDI, HEF Techmachine Increasing camber angle increase in T & PO, decrease in v Faupin et al. ( 2013 ) WB (7) 25 (± 4) 7/0 TOP End
X-terminator Invacare Corporation
SYM vs. ASY propulsion and camber angle 4 x 8s sprint (SYM/ASY and 9 and 15°) Pt, Ct, fr, PO, v, T Ergometer (VP100 HANDI, HEF Techmachine) SYM, better max sprint ASY, less fluctuations Camber angle no effect Mason et al. ( 2011 ) WB(11) & WT (3) 23 (± 6) 11/3 Top End Transformer, Invacare Effects of Camber 4 x 4 min propulsion (2.2 m/s; 15/ 18/20/24°) PO, ME, Rt, Pa, Ct, Pt, fr Treadmill (H/P/Cosmos Saturn) Increasing camber angle, increase ME Mason, Van Der Woude, Tolfrey, Lenton ( 2012 ) WB (13) 24 (± 7) 9/4 Top End
Transformer; Invacare Elyria,
OH Effects of wheel and hand-rim size on submax propulsion 3 x 4 min propulsion (2.2 m/s; 24/ 25/26 inch) PO, F, W, fr, Pt, Pa, VO2, ME Treadmill (H/P/Cosmos Saturn), SMART Wheel (Three Rivers holding) Decreasing wheel size increase F Mason et al. ( 2015 ) AB (8) 30 (± 5) 8/0 RGK Quattro Effect wheel stiffness, tyre type, type orientation 16 x 3 min (8 wheels, 2 speeds) PO, Pt, fr, VO2, Ergometer (VP Handisport- 25, techmachine) No differences WP technique * WB = wheelchair basketball, WR = wheelchair rugby, WT = wheelchair tennis, AB = abled-bodied, WP = wheelchair propulsion, Pt = push time, Ct = cycle time, fr = frequency, Rt = recovery time, Ca = contact angle, T = torque, PO = power output, ME = mechanical efficiency, v = velocity, W = work, acc = acceleration, t = time, SYM = symmetry, ASY = asymmetry, Pa = push angle, F = force
Groot et al., 2017). No differences were seen in propulsion technique variables between the two different hand rims on submaximal propulsion level. When sprinting, the regular hand rim showed better performance on maximal velocity, acceleration and the push frequency compared to the squared-profile hand rim. Differences could be explained due to unfamiliarity of the participants with the new rim, since it is difficult to change an already existing propulsion technique.
A broader view from wheelchair court sports
Since there was only one article specified on wheelchair mobility performance and two articles specified on wheelchair propulsion technique in wheelchair tennis, a broader view will be given from the other wheelchair court sports keeping a wheelchair tennis perspective in mind. First, an optimal configuration will be discussed based on a qualitative examination and regression analysis, before going into detail on specific areas as the seating orientation and the wheel configuration.
A qualitative examination of wheelchair configuration for the optimal wheelchair mobility performance configuration in wheelchair court sports has been conducted by
Mason et al. (2010). With the help of semi-structured interviews, the perception of
certain areas of wheelchair configuration were investigated. In this study, three important themes were discussed: performance indicators, principal areas’ and supplementary areas of wheelchair configuration.
The most important performance indicators for wheelchair tennis were the
stability, initial acceleration and manoeuvrability (Mason et al., 2010). Initial
acceleration was important due to the first two pushes from a rolling start, to react properly to the shot of an opponent. The ability to turn was also an important area, due to the frequency that turns are performed. Wheelchair tennis players are more in control of their wheelchair and do not have obstacles to avoid, like in other wheelchair sports.
The most important principal areas of wheelchair configuration for wheelchair tennis were the seat height, fore-aft seat position, seat backrest and camber angle
(Mason et al., 2010). Both a lower seat height and a larger camber angle were
suggested to positively influence the turning ability of wheelchair tennis players. A more anterior seating position and the backrest of the seat allowed players to assist with striking of the ball. For the supplementary areas of wheelchair config-uration, the focus should be on the foot-plate position and tyre pressure (Mason
et al., 2010). Greater manoeuvrability was achieved by placing the feet underneath
the seat, which results in more body weight closer to the axis passing through the centres of both rear wheels, decreasing the moment of inertia. Tyre pressure was important due to the different surfaces’ wheelchair tennis is played on. It was suggested that tyre pressure must be adjusted based on the surface competed on, but it is unknown what recommendations should be given. All above-mentioned areas are qualitatively investigated with the use of practical experts in the field. It would benefit wheelchair tennis to investigate these areas in a more systematic way using objective measurement techniques.
Predictors of wheelchair mobility performance to eventually improve wheelchair mobility
performance in wheelchair basketball were described by T. T. J. Veeger et al. (2019) with the
help of regression models. All participants were tested with the use of a wheelchair mobility performance test, consisting of 15 important components that define wheelchair basketball
(De Witte et al., 2018). These components are sprints, manoeuvrability drills and specific
wheelchair basketball activities. Three IMUs were attached to the wheelchair to collect and calculate (rotational) velocity/acceleration values. The vertical distance between the top of the shoulder and wheel axis and the vertical distance between the seat and footrest were the best predictors of wheelchair mobility performance. An increase in the vertical distance from shoulder to wheel axis and decrease in vertical distance from seat to footrest led to the best performance. Both vertical distances are highly correlated with the elbow angle and the seat height. The camber angle, wheel size and hand rim size were the last three modifiable variables, which were only present in one of the models. Camber angle, wheel size and hand rim size all had a positive association with wheelchair mobility performance, meaning an increase led to better performance.
Seating
The seat orientation of a wheelchair can, for example, vary in height, depth, width, fore-aft position and angle. The fore-aft position is defined as the anterior/posterior position of the chair. The weight of the wheelchair and the distribution of the mass also play an important
role. Seat height in wheelchair basketball was investigated by Van Der Slikke et al. (2018) with
the use of the beforementioned wheelchair mobility test, used by T. T. J. Veeger et al. (2019).
Several test conditions were tested in a random order. The conditions consisted of a 7.5% lowered/elevated seat height, 7.5% increased mass at the centre/distributed. Elevation of the seat height reduced the performance, both the forward and rotational aspect. The addition of mass, in general, resulted in a reduction of the forward acceleration, while distributing the
mass affected the rotational performance. In accordance with Mason et al. (2010) it was
suggested to move the foot plate under the chair, aligning the mass with the rear wheel axis.
In a study by Haydon et al. (2019) a robust design approach was used to evaluate
wheelchair rugby chair configuration on an individual level. In their study, wheelchair mobility performance was tested for six individuals using a variety of settings, includ-ing the seat height, seat depth and seat angle. Usinclud-ing an orthogonal array, allowed them to only test a reduced amount of settings instead of all possible combinations of wheelchair settings. In their paper a case study is described of an individual athlete to show the possibilities of using such an orthogonal approach to find an optimal setting for each individual. On a group level, it was shown that half of the participants preferred the new setup over the current setup, a typical response for choosing the current set-up was familiarity with the material.
Wheels
The wheel size of a sports wheelchair is an important part of the wheelchair interface.
Mason, Van Der Woude, Lenton et al. (2012) investigated the effect of wheel sizes (24, 25
and 26 inch) in wheelchair basketball. Wheel size was tested on linear mobility (straight line sprinting) and manoeuvrability (turning capabilities). With increasing wheel size, the initial velocity and mean and peak velocities increased, which resulted in improved times on 20-metre sprint test. No effects were found on the linear mobility and
manoeuvrability for the wheel size. The manipulation of the wheel size positively affected the sprinting performance, while no bearing on linear mobility and manoeuvrability was detected. A 26-inch wheel was therefore proposed by Mason, Van Der Woude, Lenton
et al. (2012) as the best performing setting. Although this was true in the context of this
study, this might not be generalisable to all wheelchair tennis players. In the study of
Mason, Van Der Woude, Tolfrey, Lenton et al. (2012) the effect of the wheel size on the
propulsion technique was investigated (24, 25, 26 inch), with the use of 3 × 4 minutes propulsion on an ergometer and the use of an instrumented measurement wheel, i.e.,
a Smartwheel (Cooper, 2009). Smaller wheel sizes led to higher forces and power output,
and a greater contact angle. The higher mean power output generated with the smaller wheel size resulted from a higher angular velocity and momentum. Mason, Van Der
Woude, Tolfrey, Lenton et al. (2012) suggested that a reduction in power output and
oxygen cost and consequently an improved economy is of great relevance in wheelchair court sports, which was the case in greater wheel sizes.
Camber angle
The camber angle is defined as the angle between the wheel and the vertical. A wider wheelbase with an increased camber, provides the wheelchair user with improved
stability (Trudel et al., 1997). Mason, Van Der Woude, Tolfrey, Goosey-Tolfrey et al.
(2012) investigated the effect of camber angle (15, 18, 20 and 24 degrees) in wheelchair
basketball on linear mobility and manoeuvrability. With a camber angle of 18° or 20°, the initial contact velocity and mean and peak velocities increased, which resulted in improved times on 20-metre sprint tests. Using a camber angle of 24°, the linear mobility decreased compared to all other settings. For the camber angle, the 18° and 20° setting were the most favourable for all aspects of mobility performance, linear and non-linear.
The effects of the camber angle on wheelchair propulsion technique variables were
investigated in a wide range of angles, 9 till 24 degrees (Faupin et al., 2004; Mason et al.,
2011). In the study of Faupin et al. (2004) three camber angles (9, 12 and 15 degrees) were
investigated. Velocity decreased and power output increased with an increased camber
angle with the use of 3 x 8 s sprints on an ergometer. The study of Mason et al. (2011) had
critique on the standardisation method of Faupin et al. (2004). In the study of Mason
et al. (2011) the seat height was adjusted to compensate for the changes in camber angle,
which was lacking in the study of Faupin et al. (2004). In the study of Mason et al. (2011)
a total of four camber angles (15, 18, 20 and 24 degrees) were investigated with the use of 4 × 4 min propulsion on a treadmill. The angles used in this study are more
representa-tive for the angles currently used in wheelchair court sports (Mason et al., 2011). A larger
camber angle led to a higher power output and mechanical efficiency. An improvement in mechanical efficiency does not necessarily lead to a reduction in economy, which makes a larger camber angle not the most optimal setting.
Tyres and grip
Not only the size and camber of the wheel affected the sprinting performance, also the
tyres (e.g., pressure, thread) influenced the performance in the field (Mason et al., 2015).
In a study of Mason et al. (2015) five different wheels/tyres were compared with the use of
condition, as well as the Spinergy TUFO and Celeritas 300 with tubeless tyres, which can reach pressures up to 12–16 bar. Initial acceleration, over 2.5 m and 5 m, was better in the new Spinergy condition compared to the used one, while no differences were found at the end of the 20 m sprint. Overall the Equaliser wheel reported the quickest times, with no differences between the new and used condition, meaning that condition seemed to have
no influence on the Equaliser tyres. In the study of Mason et al. (2015) the five wheels
were also investigated with the use of a deflection test to define the stiffness and 2 × 3 min submaximal propulsion to define the differences in propulsion technique. The stiffness of a wheel can be described by the resistance under loading. The Celeritas 300 wheel was the least stiff, compared to the other wheels investigated. No differences in wheelchair propulsion technique could be seen between the wheels.
The grip between the hand and the wheels were investigated in both wheelchair rugby and
basketball. In a study of Van Der Slikke et al. (2018) the overall grip, tested by using rubberised
gloves, hardly affected the wheelchair mobility performance in wheelchair basketball. In their study rubberised gloves were used to increase the grip, tested with the aforementioned
wheelchair mobility performance test. Mason et al. (2009) investigated the effect of four
different kinds of gloves on agility, sprint and acceleration in wheelchair rugby. Results showed that participants performed best on all aspects, agility, sprint and acceleration by wearing gloves which were customised and modified to the requirements of each individual. This showed that it is still questionable which structure could best be used to attain more grip.
Discussion and implications
The impact of the racket
Studies investigating wheelchair propulsion while holding a racket were scarce, meaning still a lot of knowledge is lacking. It is known that a racket influences performance, both
in the field and the lab (Goosey-Tolfrey & Moss, 2005; De Groot et al., 2017, 2018). It is
recommended to also test inexperienced wheelchair tennis players if big changes to the
design of a chair are made (De Groot et al., 2018). Inexperienced players have not
developed a preference in technique yet. Learning a new skill is always a difficult task, but changing your technique after using the same technique your whole life might even be more challenging. It is essentials for players to be open-minded and willing to invest
time to learn a new complex technique (De Koning et al., 2000).
Still many important areas need to be investigated, to reduce the higher peak and mean
power output of the racket hand (De Groot et al., 2017), and eventually improve the game
of wheelchair tennis. Wheelchair mobility performance as well as wheelchair propulsion technique might benefit from a more specific focus on wheelchair propulsion while holding a racket. An important aspect to consider is the loading on the shoulder complex in more detail. It would be of great interest to investigate the consequences a racket and a different kind of rim have on the muscle loading as well as the joint pressure of the shoulder joint.
Future recommendations
Wheelchair configuration influences wheelchair mobility performance and wheelchair propulsion technique of a wheelchair tennis player. Both areas would benefit from
a more proper scientific foundation. If athletes want to compete on a high level, in a safe environment, with minimal risk of injury, a solid configuration of the wheelchair is essential. For wheelchair tennis the only principal area investigated was a different hand rim, but wheelchair rugby and wheelchair basketball gave indications of the most valuable areas to focus on.
In wheelchair tennis no specific rules are set regarding the configuration of a wheelchair, indicating all areas could be adjusted to come to an optimal wheelchair
tennis chair (ITF Tennis, 2020). This leads to self-exploration; players are using a bucket
or are sitting on their knees to optimise their configuration and performance (Figure 4).
The development of the wheelchair tennis chair is changing, leading to more questions, which can all benefit from more scientific research.
The most important principal areas of wheelchair configuration for wheelchair tennis
according to Mason et al. (2010) were the seat height, fore-aft seat position, seat backrest and
the rear wheel camber. The study was only based on interviews, but the interviews were of a high quality and it is important to know the opinion of the athlete. These principal areas
were in accordance with the regression predictors in the study of T. T. J. Veeger et al. (2019)
for wheelchair basketball. The wheel size and elbow angle were also predictors, and elbow
angle has strong correlations with the seat height (T. T. J. Veeger et al., 2019). Unfortunately,
scientific research on seating, wheels and camber angle is lacking in wheelchair tennis.
In wheelchair basketball, a more elevated seat height led to a reduction in performance
(Van Der Slikke et al., 2018), but it is still unknown which seat height is favourable. It was
also suggested aligning the mass with the rear wheel axis, i.e., moving the feet under the wheelchair. This is especially important since turning is considered an important aspect in wheelchair tennis and a more distributed mass leads to a reduction in rotational
aspects (Mason et al., 2010; Van der Slikke et al., 2020; Van Der Slikke et al., 2018). Not
only in wheelchair tennis, but also in the other wheelchair court sports the research regarding seating is lacking, as no information is available about the seat width, fore-aft position and seat angle. In ‘regular’ wheelchair research already multiple studies have
been performed to investigate the effects of seating (Stankovits, 2000; Van der Woude
et al., 1989). This information is highly valuable, and gives good indications about the optimal seating position based on the elbow extension, which is around 100–120°. Figure 4. Innovative wheelchair tennis chairs.
Although it is questionable what the optimal seating position would be in a wheelchair sports setting with the more advanced sports wheelchairs.
Important findings with respect to the camber angle and wheel size for wheelchair basketball were the higher forces and power output in smaller wheel sizes and larger camber
angles (Mason et al., 2011; Mason, Van Der Woude, Tolfrey, Lenton et al., 2012). Also,
larger wheel sizes and a camber angle of 18° or 20° let to better sprinting performances in
the field (Mason, Van Der Woude, Lenton et al., 2012; Mason, Van Der Woude, Tolfrey,
Goosey-Tolfrey et al., 2012). In the studies of Mason, Van Der Woude, Lenton et al. (2012)
and Mason, Van Der Woude, Tolfrey, Lenton et al. (2012) standardisation between wheel/
camber conditions was achieved by adjusting the seat height to standardise the elbow angle.
For the studies of Mason et al. (2011) and Mason, Van Der Woude, Tolfrey, Goosey-
Tolfrey et al. (2012) investigating camber angle, also the distance between the shoulder and
top dead centre of the wheel were standardised. Adjustment of the seat height is a form of standardisation, but it is also known that changing the seat height influences the dynamic
stability of the chair (Sauret et al., 2013). It is important to investigate the effect of different
camber angles on manoeuvrability, while holding a racket, because the racket could influence the manoeuvrability. Nowadays, more players are using 27-inch wheels in wheel-chair tennis. Given the fact that larger wheel sizes led to the most positive results, it would be beneficial to also investigate larger wheel sizes, since it is unknown if 26 inch was the
optimum (Mason, Van Der Woude, Lenton et al., 2012).
The type of wheel suggested to be used in wheelchair court sports is the Equaliser, since it led to the best performances in the field and has no negative effects on the
propulsion technique (Mason et al., 2015). The investigation of different tyre types and
pressures is an important aspect to consider regarding wheelchair tennis, since the sport is played on multiple surfaces, i.e., hardcourt, grass and clay. Also the study of Mason
et al. (2015) showed the importance of tyre maintenance and the possible benefit of high-
pressure tubeless tyres as important areas to investigate in the future.
Finally, it would be of great benefit for wheelchair tennis research to close the gap between lab, field, training and match testing, while accounting for power output (W) in
each and any condition (De Klerk, Vegter, Leving et al., 2020). It is important to define
which mobility performance characteristics and biomechanical parameters best define
wheelchair tennis, also keeping the different divisions in mind (Mason et al., 2020; Van
der Slikke et al., 2020). Standardisation is of high value to interpret data, to achieve this,
power output (W) is a key parameter, next to (rotational) speed and acceleration (De Klerk,
Vegter, Leving et al., 2020; Van der Woude et al., 2001). Refined measurement tools, such as
IMUs and light measurement wheels are proposed to be used to give a better understanding of field performance in a more standardised way. For the lab, wheelchair roller ergometers are potential innovations that help understand wheeling performance in athletes (De Klerk,
Vegter, Goosey-Tolfrey et al., 2020; De Klerk, Vegter, Veeger et al., 2020). All this
information could eventually lead to a more proper foundation for wheelchair tennis research in general and the configuration of the wheelchair tennis chair.
Limitations
The results of this review have to be interpreted with care. Continued motor adaptation is an important part in manual wheelchair research; investigating wheelchair
configurations typically requires more time for familiarisation in participants or
ath-letes for that matter (Vegter et al., 2014, 2015). Also, most research on wheelchair
mobility performance and wheelchair propulsion technique in court sports is con-ducted with the use of wheelchair basketball or wheelchair rugby players. It is impor-tant to notice that, although those court sports and wheelchair–athlete combinations have lots of similarities with wheelchair tennis, the racket has an effect on wheelchair
propulsion (Goosey-Tolfrey & Moss, 2005; De Groot et al., 2017). Wheelchairs in
wheelchair tennis are becoming more optimised towards the demands of the individual and the game, which sets it further apart from the other wheelchair court sports. Despite these differences between wheelchair sports, this overview is helpful to give a future direction of wheelchair tennis research.
Another aspect is the quality of the evidence of the articles. The overall quality of the articles was moderate to good, but this has to be taken with care, since no standardised checklist was used to define the methodological quality. Although there is no standardised checklist available, it was still important to assess the quality of the articles.
Conclusion
The research on the effect of wheelchair configuration on wheeling performance in wheelchair tennis is scarce. There is still much knowledge to gain, which could benefit wheelchair configuration and subsequently wheelchair tennis performance. Conducting more systematic research in wheelchair propulsion while holding a racket needs to be the main focus. Eventually, the bigger step towards understanding the complex skill of wheelchair tennis and its configuration can be made.
Acknowledgments
The authors would like to thank Double Performance for the providence of a figure of a wheelchair tennis chair.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Funding
This work was supported by the University Medical Center Groningen, University of Groningen.
ORCID
Thomas Rietveld http://orcid.org/0000-0002-7753-9958 Riemer J. K. Vegter http://orcid.org/0000-0002-4294-6086 Lucas H. V. der Woude http://orcid.org/0000-0002-8472-334X Sonja de Groot http://orcid.org/0000-0001-8463-2563
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