J. Bascou

Assessment of Field Rolling Resistance of Manual Wheelchairs

This article proposes a simple and convenient method for assessing the subject-specific rolling resistance acting on a manual wheelchair, which could be used during the provision of clinical service. This method, based on a simple mathematical equation, is sensitive to both the total mass and its fore-aft distribution, which changes with the subject, wheelchair properties, and adjustments. The rolling resistance properties of three types of front casters and four types of rear wheels were determined for two indoor surfaces commonly encountered by wheelchair users (a hard smooth surface and carpet) from measurements of a three-dimensional accelerometer during field deceleration tests performed with artificial load. The average results provided by these experiments were then used as input data to assess the rolling resistance from the mathematical equation with an acceptable accuracy on hard smooth and carpet surfaces (standard errors of the estimates were 4.4 and 3.9 N, respectively). Thus, this method can be confidently used by clinicians to help users make trade-offs between front and rear wheel types and sizes when choosing and adjusting their manual wheelchair.

A method for the field assessment of rolling resistance properties of manual wheelchairs

This article presents an examination and validation of a method to measure the field deceleration of a manual wheelchair (MWC) and to calculate the rolling resistances properties of the front and rear wheels. This method was based on the measurements of the MWC deceleration for various load settings from a 3D accelerometer. A mechanical model of MWC deceleration was developed which allowed computing the rolling resistance factors of front and rear wheels on a tested surface. Four deceleration sets were conducted on two paths on the same ground to test the repeatability. Two other deceleration sets were conducted using different load settings to compute the rolling resistance parameters (RPs). The theoretical decelerations of three load settings were computed and compared with the measured decelerations. The results showed good repeatability (variations of measures represented 6–11% of the nominal values) and no statistical difference between the path results. The rolling RPs were computed and their confidence intervals were assessed. For the last three sets, no significant difference was found between the theoretical and measured decelerations. This method can determine the specific rolling resistance properties of the wheels of a MWC, and be employed to establish a catalogue of the rolling resistance properties of wheels on various surfaces.

Repeatability of wheelchair deceleration tests using a 3-D accelerometer

Rolling resistance is an important aspect of manual wheelchair (MWC) propulsion when assessing the subject’s physical capacities and characterising the MWC’s efficiency through its energy loss. For this reason, several authors have evaluated the braking force acting on the MWC from its deceleration on the field. For this purpose, the deceleration could be calculated from experimental data either by a second-order differentiation of the rear-wheel angular displacement (Coutts 1991, 1994), or from the movement differential equations during a 6–10-m-long deceleration (Frank and Abel 1988; Vinet et al. 1998; Hoffman et al. 2003). Other authors directly measured the MWC deceleration with a 3-D accelerometer (Vaslin and Dabonneville 2000; de Saint Rémy et al. 2003). Nevertheless, the eventual ground irregularities and wheels eccentricity may have an important effect on the results because the gravity acceleration, which reaches 100 times the braking deceleration, could be partially measured along the theoretical axis of the MWC movement. This study aims at quantifying the repeatability of the MWC deceleration test on the field, in three controlled conditions, using a 3-D accelerometer.

Error estimations of wheelchair deceleration tests using a 3D accelerometer

During manual wheelchair (MWC) propulsion, the power developed by the user is useful not only to accelerate the MWC, but also to cycle up a slope and to overcome the global braking forces, which include: rolling resistance, aerodynamic drag force, bearing resistance and some other internal resistances. Among these, the rolling resistance is very important in usual MWC locomotion, whereas the others are generally neglected. Besides, some studies have claimed the rolling resistance is not equally balanced between front and rear wheels (de Saint Rémy et al. 2003; Sauret et al. 2009). From a mechanical model of MWC rolling resistance, Sauret et al. (2009) computed the rolling resistive parameters of front (lfront) and rear (lrear) wheels from MWC deceleration measured with a 3D accelerometer. This study aimed at estimating the errors of MWC deceleration measurement and rolling resistive parameters calculation. These parameters were obtained using the MWC deceleration technique (Vaslin and Dabonneville 2000; de Saint Rémy et al. 2003).

ASSESSING “POWER INPUT” OF THE MANUAL WHEELCHAIR USER DURING REAL LIFE AMBULATION

Assessing the mechanical power produced by the user of a manual wheelchair (MWC) during daily ambulation is an important issue because it highlights the users difficulties to move in his environment. Currently, this power is assessed by the power of the handrim propelling torque (PP) measured with one (or two) instrumented wheel(s) mounted on a fixed ergometer [Veeger, 1991] or on a MWC. Although this method takes into account the obvious propulsive actions of the user on both handrims (HR), it neglects the power of the user’s actions on the seat. This paper aims at presenting a new method taking into account all the user’s mechanical actions to assess the net power (PI) put by the user in the MWC system during actual ambulation on any floor using an instrumented MWC.

Turning resistance of a manual wheelchair: a theoretical study.

The study of the resistances opposed to the motion of a manualwheelchair (MWC)was generally limited to the case of the straightforward displacement (Kauzlarich et al. 1984; Frank andAbel 1989; deSaint-Rémyet al. 2007; Sauret et al. 2012). Indeed, this movement often occurs during the daily activity and is a source of fatigue. However, other situations could lead to increase the fatigue of the MWC user, such as mounting ramps (Bascou et al. 2013) or propelling theMWC on a cross slope (Sauret et al. 2013). Among the various situations, the rotation of theMWCoften occurs during daily and sports activities and is subjected to the ‘turning resistance’. However, few authors studied this resistance (Kauzlarich et al. 1984; Frank and Abel 1989) and only Kauzlarich et al. (1984) reported values of MWC turning resistance, showing that this resistance was not negligible. As a consequence, seeking to decrease the turning resistance could lead to decrease both the fatigue and the risk of upper limb musculo-skeletal disorders of the MWC user, especially when the turning situation is repeated. Based on the conclusions of previous studies focused on rolling resistance (Sauret et al. 2012), it was hypothesised that turning resistance could be decreased from geometrical changes of the MWC, such as the wheel radii or the mass distribution on front wheels. Thus, the aim of this studywas to investigate the influence of MWC settings on turning resistance from a theoretical point of view.

Evolutions of the wheelchair user's centre of mass and centre of pressure according to the seat fore-aft position during sprinting: a case study of an elite wheelchair tennis player

When competing, wheelchair elite tennis players must perform various actions on the court to achieve victory. Among these actions, the straightforward displacement requires to accelerate the Manual Wheel Chair (MWC) until reaching the maximal possible velocity, in order to minimize the time needed to travel the distance required to hit the ball. During propulsion, the fore-aft position of the seat with respect to the rear wheels is reported to affect upper limb kinematics [Gorce, 2012], [Kotajarvi, 2004] and propulsion velocity [Freixes, 2010]. In addition, it will change the fore-aft distribution of the mass that directly affects the rolling resistance [Sauret, 2012]. Indeed, moving the seat backward should decrease the rolling resistance but may also increase the MWC fore-aft instability that the subject would have to balance. As a consequence, optimizing the fore-aft position of the wheelchair necessitates a compromise for the tennis player and must be carefully studied. Thus, the aim of this study was to evaluate the influence of the seat fore-aft position on time displacements of both the subject’s centre of mass (COM) and subject-and-MWC centre of pressure (COP) during propulsion at maximal velocity.

Rolling resistance index of manual wheelchairs

Rolling resistance of manual wheelchair (MWC) is an important criterion when choosing a MWC. Previous studies on this topic concluded that rolling resistance not only depended on the total mass of the {User + MWC} system but mainly on its foreaft distribution [1, 2, 3, 4, 5]. Our recent works allowed quantifying rolling resistance parameters (distance between theoretical and real centres of pressure in the contact area) of various front and rear wheels on two floors. It was showed that these parameters depended on wheels types (roller, standard or soft roll casters and rear wheels pneumatics vs solid rear wheels) and could be very different on hard smooth and carpet surfaces [4, 5]. These surfaces can be considered representative of floors extend on which MWC users usually roll. Results provided by experiments and equation presented in [2, 4, 5] allow computing rolling drag force according to the subject-specific fore-aft distribution of the total mass, which depends on the user’s anthropometric properties, and from the MWC materials and adjustments. In practice, a user only rolling on hard smooth surfaces would likely prefer some MWC properties, which may be different from those he would have chosen if he only rolls on carpet. In this scope, this study aims at defining an index, which characterises the subject-specific rolling resistance with regard to its main daily rolling surface.

Whole limb push-off work in people with transtibial amputation during slope ascent.

Unilateral transtibial amputation impairs locomotion, especially in daily living outdoor situations. As an example, slope ascent requires specific gait adjustments such as hip power generation during single support followed by ankle power generation during second double support. Hip extensor strengthening could help people with transtibial amputation for hip propulsion in slope ascent (Langlois et al. 2014). Energy storage and return (ESAR) foot-ankle prostheses have been designed to absorb and release elastic energy in an attempt to restore some functions of the amputated limb. However, it remains unclear how ESAR feet contribute to center of mass propulsion, especially during slope ascent. Simple models were recently developed to globally analyze gait in an energetic point of view by computing the center of mass mechanical work (Donelan et al. 2002; Kuo et al. 2005). Particularly, several hypotheses permit to estimate for each lower limb the whole limb push-off work during double support (Kuo et al. 2005). Using this approach, step-to-step transition was investigated during level walking, in ablebodied subjects wearing prosthetic foot (Caputo & Collins 2014) and in people with transtibial and transfemoral amputation (Houdijk et al. 2009; Bonnet et al. 2014), and in slopes in able-bodied subjects (Franz et al. 2012). Up to now, no study quantified prosthetic and contralateral push-off work during slope ascent in a below-knee amputee population. Thus, the aim of the study is to investigate center of mass mechanical work adjustments during the propulsion period during slope ascent for two inclinations of slopes compared to level walking in people with transtibial amputation.

Measurement of wheelchair adjustment effects on turning deceleration

Manual wheelchair (MWC) locomotion combines straightforward and turning motions, in everyday life as well as in sport practice. Many authors demonstrated the effects of various MWC properties, such as geometry or wheel type, for straightforward displacements (Brubaker 1986; Medola et al. 2014), while only few studies have investigated their influence for turning motion (Bascou et al. 2014; Caspall et al. 2013; Kauzlarich, Bruning, and Thacker 1984). In particular, the impact of wheelchair setup on its turning deceleration, which characterizes the MWC tendency to stop its turning motion, is unclear. This study aims at clarifying the effects of MWC adjustments on turning deceleration in the field, using a fractional factorial design.