http://informahealthcare.com/idt ISSN 1748-3107 print/ISSN 1748-3115 online Disabil Rehabil Assist Technol, 2013; 8(6): 496–501 ! 2013 Informa UK Ltd. DOI: 10.3109/17483107.2012.756947

ORIGINAL RESEARCH PAPER

Effects of synchronous versus asynchronous mode of propulsion on wheelchair basketball sprinting 1

Laboratoire HANDIBIO ‘‘Laboratoire de Mode´lisation et Inge´nie´rie des Handicaps’’, EA 4322, Universite´ du Sud Toulon Var, Batiment Z, La Garde Cedex, France, 2Univ Lille Nord de France, F-59000 Lille, France, 3UDSL, EA 4488, Faculte´ des Sciences du Sport et de l’Education Physique, F-59790 Ronchin, France, 4Department of Rehabilitation Sciences, Faculty of Physical Education and Physiotherapy, Katholieke Universiteit Leuven, Belgium, and 5LAMIH, Laboratoire d’Automatique de Me´canique et d’Informatique Industrielles et Humaines, Valenciennes, France Abstract

Keywords

Purpose: This study aimed to first investigate synchronous (SYN) versus asynchronous (ASY) mode of propulsion and, second, investigate the wheel camber effects on sprinting performance as well as temporal parameters. Method: Seven wheelchair basketball players performed four maximal eight-second sprints on a wheelchair ergometer. They repeated the test according to two modes of propulsion (SYN and ASY) and two wheel cambers (9 and 15 ). Results: The mean maximal velocity and push power output was greater in the synchronous mode compared to the asynchronous mode for both camber angles. However, the fluctuation in the velocity profile is inferior for ASY versus SYN mode for both camber angles. Greater push time/cycle time (Pt/Ct) and arm frequency (AF) for synchronous mode versus asynchronous mode and inversely, lesser Ct and rest time (Rt) values for the synchronous mode, for which greater velocity were observed. Conclusions: SYN mode leads to better performance than ASY mode in terms of maximal propulsion velocity. However, ASY propulsion allows greater continuity of the hand-rim force application, reducing fluctuations in the velocity profile. The camber angle had no effect on ASY and SYN mean maximal velocity and push power output.

Power output, velocity, wheelchair ergometry, wheel camber History Received 13 February 2012 Revised 2 December 2012 Accepted 4 December 2012 Published online 25 January 2013

ä Implications for Rehabilitation 





The study of wheelchair propulsion strategies is important for better understanding physiological and biomechanical impacts of wheelchair propulsion for individuals with disabilities. From a kinematical point of view, this study highlights synchronous mode of propulsion to be more efficient, with regards to mean maximal velocity reaching during maximal sprinting exercises. Even if this study focuses on well-trained wheelchair athletes, results from this study could complement the knowledge on the physiological and biomechanical adaptations to wheelchair propulsion and therefore, might be interesting for wheelchair modifications for purposes of rehabilitation.

Introduction For individuals with disabilities, wheelchair propulsion pattern is of cyclic and repetitive nature similar to bipedal and cycling pattern but could be considered as a complex and very variable pattern. In fact, if we consider two wheelchair users exercising at a similar power output, clear differences in choice of push frequency and propulsion techniques would be evident. Several researchers have examined different propulsion strategies in manual wheelchair propulsion such as forward versus reverse [1,2] and synchronous (SYN) versus asynchronous (ASY) pushrim methods [3,4]. Among them, the synchronous mode is Address for correspondence: Arnaud Faupin, UFR STAPS, Batiment K, Avenue de l’Universite´ – BP20132 83957 LA GARDE CEDEX, France. Tel: +33 (0)4 94 14 27 57. E-mail: [email protected]

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Arnaud Faupin1, Benoit Borel2,3, Christophe Meyer4, Philippe Gorce1, and Eric Watelain1,5

described by Goosey-Tolfrey and Kirk [5] as work that is done by both arms in unison in order to exert force at the same moment on the hand-rims. On the other hand, asynchronous propulsion is described as work done by the arms in an alternate fashion, so that at each contact time, only one arm applies force on the hand-rim [5]. In wheelchair basketball, some players adopted an asynchronous push strategy in some phases of the game [5], which could probably allow players to have better control and mastery of their wheelchair, required for more accurate dribbling action and for acceleration after a pivot, by increasing the time of contact with the hand-rims. In the wheelchair literature, physiological responses (VO2, HR, gross caloric output) of SYN or ASY mode of propulsion show contradictory results. Indeed, during submaximal push strategy tasks (SYN versus ASY), Glaser et al. [3] found significantly

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Table 1. Individual and means (SDs) of the anthropometric data of the participants as well as their classification and their weekly training hours.

Participants

Age (years)

Mass (kg)

Height (cm)

Disability

IWBF point classification

Volume (hours/week)

1 2 3 4 5 6 7 Means (SD)

20 24 27 32 25 22 24 25(4)

36 52 60 68 75 103 68 66(19)

150 180 168 168 180 194 175 174(13)

SCI SCI Polio Polio Ortho AB AB –

1.5 1.5 4 4 4.5 5 5 –

4 6 6 6 6 6 4 –

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IWBF, International Wheelchair Basketball Federation; SCI, spinal cord injury; polio, post poliomyelitis; ortho, orthopedic involvement of knee; AB, able bodied; SD, standard deviation.

reduced metabolic and cardiopulmonary responses during ASY versus SYN mode of propulsion and in contrary, different investigations show that SYN mode appeared to be more economical, least physiologically stressful than the ASY mode of propulsion [5,6]. Finally, Lenton et al. [4] have shown no physiological differences between SYN and ASY modes of propulsion, even if ASY propulsion demonstrated lesser physiological responses and increased gross and net efficiency. However, previous studies have shown differences in their exercise and evaluation protocols. They have also one common point: the exercise proposed by these studies was not representative of repeated sprinting-activity characteristics of collective wheelchair sports. Indeed, in wheelchair basketball, the ability to start and sprint from standstill is very important as the movement dynamics in wheelchair basketball (and also in rugby) are specifically related to handling the wheelchair and can be defined as starting, sprinting, braking, turning (pivoting) and blocking [7]. Similarly, Mason et al. [8] have identified in 2010 four important areas that they felt were paramount to successful sports performance: stability, initial acceleration, maneuverability and sprinting. These specific dynamics of wheelchair basketball must be taken into account in the study design. Since sprinting is considered as an important component of the performance in wheelchair basketball as well as in other wheelchair sports and has been rarely investigated, we have decided to focus especially on the sprinting component of our athletes. In fact, to the best of the authors’ knowledge, studies [3– 6,9,10] focusing on wheelchair propulsion mode (i.e. SYN versus ASY) did not really aim at its impact on wheelchair basketball sprinting. Since it is essential to consider maximal sprinting velocity as performance criteria in wheelchair basketball, it would be therefore of great importance to investigate its influence by the choice of propulsion mode. Consequently, we aimed to compare the two propulsion modes and their effect on sprinting performance (velocity and power output) as well as temporal parameters (push time, cycle time, recovery time, etc.). As wheel camber has been already shown to influence sprinting performance [11], we also assessed the effect of propulsion mode combined with two wheel cambers (9 and 15 ) in order to determine if an optimal combination of wheelchair setup/ propulsion could be determined for sprinting performance.

Materials and methods Participants This study was performed with seven male participants who were all members of the same wheelchair basketball club in the French elite Championship. The means and standard deviations (SDs) of the anthropometric data (age, mass, height, disability, classification, daily training hours) are given in Table 1. For the international competition, players are placed into eight

Figure 1. Configuration of the experimental setup (wheelchair on the ergometer).

classification levels for participation (from 1 to 4.5), based on the International Wheelchair Basketball Federation [12]. Class 5 is only used for able-bodied participants in the ‘‘French Handisport Federation’’ classification. All participants were fully informed of any risks before giving their written informed consent to participate in these experiments. The experimental procedures were approved by the local hospital ethics committee and complied with the ethical standards of the 1975 Helsinki Declaration. Materials All participants used the same wheelchair (Top End XTerminator, Invacare CorporationÕ , Elyria, OH) designed for basketball for each trial. The weight and length was 13 kg and 80 cm, respectively. The angle between the back and the seat was fixed at 75 , the seat was inclined by 15 and the back was placed vertically. The height of the back was 28 cm, while the depth and width were 42 and 39 cm, respectively. The diameter of the wheels was 64 cm; the tube tires were inflated to 8 bars. According to previous studies focusing on wheelchair propulsion mode [4–6,10], no individual adjustments relative to anthropometrics of the participants were made. A standardized chair configuration eliminated effects of wheelchair design/setup on measurements [6]. The wheelchair was placed on an original ergometer (VP100 HANDI, HEF TecmachineÕ , Andrezieux-Boutheon, France, Figure 1) comprised of a system of two pairs of independent rollers [13]. This ergometer was adapted on the lines of the VP100 HTE ergometer validated and presented by Devillard et al. [14] The ergometer was equipped with two electromagnetic brakes

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(Type ZS, Friedrichshafen, Germany), producing a braking torque from 0 Nm to 4 Nm, one on each side of the roller system, which are mounted on a force sensor. The roller system was calibrated prior to the beginning of the study with a control kit for a 0, 1, 2, 3 and 4 Nm gauging range. Two incremental encoders with high resolution (3600 points per rotation) were used to measure the wheels’ instantaneous velocity. The velocity and force signals were sampled at 100 Hz, and then transposed to a NI-6024E data acquisition card (National InstrumentÕ , Austin, TX) in a computer (Victor Technologies 386SXÕ ).

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Testing procedure After a standardized warm-up and familiarization phase of 10 min (during this familiarization phase of 10 min, the participants tested the different adjustments), all of the participants performed in a random order four maximal eight-second sprints. They repeated the test according to two modes of propulsion (SYN and ASY) and two wheel cambers (9 and 15 ). At the audio and visual signs given by the experimenter, the participant performed a sprint from standstill as fast as possible for eight seconds with encouragement from the experimenters. Between each sprint, a complete rest period of five minutes was imposed during which time the experimenter proceeded with the adjustments of the wheelchair’s camber angle and the ergometer. No propulsion technique was imposed on the participant, neither before nor during experimentation. Trunk movements were not restricted because no subject involved in the study used a strap during competition. Before each sprint, the individual residual torque (Tr), due to the distortion of the tire on the rollers, and the rolling resistance of both rollers and wheelchair, were measured. For this, we used the method of Theisen et al. [15] The participants completed two or three maximal pushes on the hand-rim, and then maintained the predetermined ‘‘standard’’ position (the trunk leaned slightly forward with the elbows on the knees and the chin in the hands) until the wheels came to a complete stop. Measurements All of the values were recorded separately for the two wheels of the wheelchair. In accordance with the protocol of Veeger et al. [16], the first three seconds of the sprint (corresponding to the start) were not analyzed. Figure 2 is an example of velocity and power output developed during SYN and ASY sprints. For each sprint, the following values were recorded: the mean velocity per propulsion cycle (Vm), the cycle time (Ct), the time of the propelling phase (Pt: pulling and pushing phases during which the user propels the wheels of his wheelchair: hand in contact with the wheel), as well as the relative time in a percentage of the total cycle time (Pt/Ct). The temporal parameters (Ct, Pt) were determined by the acceleration and deceleration phases of the wheels observed on the instantaneous speed curve. For ASY strategy, arm frequency (AF) was calculated by obtaining right and left arm cadences separately, taking hand-rim contact with the hand as indicator of their cadence and then by adding both values [6,9,10]. Fluctuation in the velocity profile (FPV) was the difference in maximum and minimum velocity in cycle propulsion. The total external power output developed during the push phase (Ptot) is the sum of the power developed by the participant to overcome the inertia during the push phase (Pi) and the brake power (Pb) developed to overcome the residual torque [11,13] given, respectively, by the following equations:

Pi ¼ ðTi:oÞ Pb ¼ ðTr:oÞ

with Ti (Nm) defined by the torque needed to overcome the inertia, o (rad.s1) the angular velocity of the rollers and Tr the residual torque defined above. Statistical analysis For each parameter, the means and SDs were calculated. After ensuring that the normal distribution and the covariance homogeneity were satisfied, two-factor ANOVA for repeated measures with a 2  2 design (two modes of propulsion: ASY and SYN; two wheel cambers: 9 and 15 ) was applied to determine the effect of the type of propulsion on the biomechanical parameters. A Bonferroni post hoc test was applied to determine the location of any significant main effects. The level of significance was set at p50.05. All statistical analyses were performed using Matlabß (Mathworks, Natick, MA) and Statistica softwareß (Statsoft, Tulsa, OK). The Pearson method was used for Vm correlation testing between modes of propulsion (ASY versus SYN).

Results In Table 2, the means (SDs) Vm were between 3.1  0.5 m  s1 in 15 -ASY condition and 4  0.4 m  s1 in 9 -SYN condition. For the Ptot, the smallest was in 9 -ASY condition (120.2  31.8W) and the biggest in 15 -SYN condition (274.6  45.6). There was a statistical difference between the mode and the camber but no interaction between these two parameters. As for the temporal variables (Ct, Pt, Rt, Pt/Ct and AF), no significant differences were found between camber angles (Table 2). However, there was an increase (not significant, p ¼ 0.07) in Pt proportional to the wheel camber. Temporal parameters were not influenced by wheel camber but by propulsion modes. We found lower Ct and Rt values for synchronous and inversely, Pt/Ct and AF were greater for synchronous mode versus asynchronous one. The FPV is inferior to ASY (0.07  0.03 and 0.10  0.04) versus SYN (0.10  0.02 and 0.17  0.06), whatever the camber angle. In Table 3, Pearson’s correlation coefficients between Vm in the four conditions were only statistically significant for SYN strategy between 9 and 15 (9 -SYN versus 15 -SYN) and ASY between 9 and 15 (9 -ASY versus 15 -ASY). No statistical differences were observed between 9 and 15 for ASY versus SYN condition, nor 9 -ASY versus 15 -SYN.

Discussion The main purpose of the study was to investigate the SYN versus ASY mode of propulsion and their effect on sprinting performance. To the best of the author’s knowledge, no studies have focused on the impact of propulsion mode (i.e. SYN versus ASY) on wheelchair basketball sprinting. The major finding of this study is that the SYN mode compared to the ASY mode is more efficient in regard to reaching mean maximal velocity during maximal sprinting exercises. Whatever the mode of propulsion, the increase in wheelchair camber was associated with a significant increase in Ptot and a significant decrease in Vm. This is in agreement with previous studies [11,13] which have reported such results as a consequence of an increased rolling resistance on the roller ergometer. Synchronous versus asynchronous mode The greater results of this part are a statistically significant higher Vm of the SYN (between 3.5  0.4 and 4.0  0.4 m  s1) versus ASY (between 3.1  0.5 and 3.4  0.5 m  s1) mode as well a

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Figure 2. Example of velocity and power output developed by a typical participant during (a) synchronous and (b) asynchronous sprint.

Table 2. Means and SDs of the measured variables: velocity (Vm), fluctuation in the velocity profile (FPV), total power (Ptot), cycle time (Ct), propelling time (Pt), recovery time (Rt) and arm frequency (AF). Synchronous

Mode Camber

9 1

Vm (m  s ) FPV (m  s1) Ptot (W) Ct (ms) Pt (ms) Rt (ms) Pt/Ct (%) AF (pushes/min)



4.0  0.4 0.10  0,02 163.9  40.0 413.6  36.8 145.7  12.7 267.9  33.1 28.0  2.4 292  24

Asynchronous 



15

9

3.5  0.4 0.17  0.06 274.6  45.6 426.4  28.8 157.1  9.5 269.3  26.4 26.3  2.9 282  18

3.4  0.5 0.07  0.03 120.2  31.8 612.9  190.7 142.1  23.8 470.7  166.9 24.2  3.5 212  59

ANOVA 15



3.1  0.5 0.10  0.04 172.3  39.5 637.9  182.3 159.3  31.5 478.6  154.4 23.7  5.4 202  59

NS, non-significant differences; Mod, mode; Cam, camber; Int, interaction between mode and camber. *p50.05 and ***p50.001.

Mod

Cam

Int

* *** *** *** NS *** *** ***

* *** *** NS NS (0.07) NS NS NS

NS NS NS NS NS NS NS NS

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Table 3. Pearson’s correlation coefficients comparison between velocity (Vm) in the four conditions. Vm C9_Syn C9_Asyn C15_Syn C15_Asy

C9_Syn

C9_Asy

C15_Syn

C15_Asy

– – – –

0.55 – – –

0.88** 0.42 – –

0.65 0.79* 0.66 –

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C9, 9 of wheel camber condition; C15, 15 of wheel camber condition; Asy, asynchronous; Syn, synchronous. *p50.05 and ** p50.01.

greater push power whatever the wheel camber. Different investigations of the mode of propulsion show that physiological responses of SYN mode are more efficient than for ASY mode [5]. During submaximal propulsion, Goosey-Tolfrey and Kirk [5] suggested that the SYN mode of wheelchair propulsion was more economical than the ASY mode when AF was lower (40 pushes min1). In our study, with greater AF (between 202  59 and 282  18 pushes min1), synchronous mode was more efficient than asynchronous mode with regard to mean maximal velocity. This was similar to handcycling results, which Lenton et al. [6] pointed out the role of the trunk as a possible contribution for this efficiency. In fact, in handcycling, different authors [13,17–19] proposed that the beneficial effects of the SYN mode may also be caused by the implication of the larger muscle mass of the trunk, which would allow the weight of the trunk to be effectively used in propulsion. In Table 3, we have highlighted a correlation between velocity and wheel camber; however, no correlation between velocity and propulsion mode was observed. Consequently, players going faster using SYN mode are not necessarily the ones going faster using the ASY mode. Such result can be explained by a functional potential difference among wheelchair basketball players (i.e. their functional abilities depending on their disability level), especially trunk function and also on their ability to perform. However, physiological responses in SYN or ASY mode of propulsion show contradictory results in regard to wheelchair propulsion. In fact, during submaximal push strategy tasks (SYN versus ASY), Glaser et al. [3] found significantly greater efficiencies during ASY versus SYN mode of propulsion. Lenton et al. [4] proposed that ASY propulsion allows greater continuity of the hand-rim force application, reducing fluctuations in the velocity profile and therefore, the inertial forces overcome with each stroke are reduced. Our results are in line with this hypothesis. Indeed, the FPV is inferior for ASY (0.07  0.03 and 0.10  0.04) versus SYN (0.10  0.02 and 0.17  0.06) in both camber angles. Spatiotemporal parameters are not influenced by wheel camber but by propulsion mode. We found greater Pt/Ct and AF for synchronous mode versus asynchronous mode and inversely, lesser Ct and Rt values for synchronous one for which greater velocity was found. We suggest that such increases may be the result of, on one hand, a more important recovery phase between two pushes for one arm as a consequence of asymmetrical arm movement and on the other hand, by a trunk rotation resulting from this asymmetry. Limitations and future recommendations A limitation of this study concerns the use of only one standardized basketball wheelchair on a stationary ergometer. However, in accordance with previous studies focusing on wheelchair propulsion mode, no individual adjustments relative to anthropometrics of the participants were made. A standardized chair configuration eliminated influences of the chair designs/

setups on the study outcomes [6]. The use of a stationary ergometer could explain why the participants had no problem keeping the front wheel parallel to the propelling direction during the ASY mode in wheelchair. One should be cautious extrapolating these data since a steering condition was not permitted. Indeed, steering is suggested to involve trunk function in a different way. A second limitation of this study is the choice to not include the first three seconds of each sprint session into the analysis, according to the protocol of Veeger et al. [16]. But, for some wheelchair basketball players, it can be seen that, after the third second of sprint, stationary velocity is neither achieved in SYN condition nor in ASY condition (Figure 1). Therefore, the parameters Vm and Ptot can be affected by this transitory period during which the user is reaching his maximal velocity. At last, future studies assessing a larger sample and considering athlete classification are needed in the field with individual wheelchair.

Conclusion Under the current experimental conditions of this study, we have shown that SYN mode leads to better performance than ASY mode, in terms of maximal propulsion velocity. However, the fluctuation in the velocity profile is inferior for ASY versus SYN for both the camber angles. Therefore, ASY propulsion allows greater continuity of the hand-rim force application, reducing fluctuations in the velocity profile. Clearly, future experiments need to be performed in the field with a larger sample athlete classification.

Declaration of interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

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