ANALYZING INTRA-CYCLE VELOCITY PROFILE DURING WHEELCHAIR RACING PROPULSION: A PRELIMINARY STUDY

Recent technological improvements made it possible to monitor manual wheelchair (MWC) racing intra-cycle velocity profile under in-situ conditions. Based on the hypothesis that the intra-cycle velocity profile is related to the contribution of the upper body in racing MWC propulsion, it could be used for in-situ technical analysis. Four elite MWC racing athletes were equipped with IMUs during a 400 m race, and propulsion cycles were studied once constant speed was reached. Trunk flexion angle and trunk flexion speed were monitored, as well as manual wheelchair linear velocity. This preliminary study shows that intra-cycle velocity profile appears to be athlete specific. Future research coupling such measurements with pushrim contact detection systems could help further understanding the complexity of MWC racing propulsion’s technique and timing

A method for the field assessment of rolling resistance properties of manual wheelchairs, Computer Methods in Biomechanics and Biomedical Engineering

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.The authors would like to thank the French National Research Agency (ANR) for its financial support to the SACR-FRM project (ANR-06-TecSan-020) and to the CERAH for the loan of all the manual wheelchairs evaluated in this work

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.This material was based on work supported by the SACR-FRM project, French National Research Agency (ANR-06-TecSan-020) and the Centre d’Etudeset de Recherche sur l’Appareillage des Handicapés (loaned all MWCs required to fulfill this work

Drag force mechanical power during an actual propulsion cycle on a manual wheelchair

Revue IRBM : http://www.em-consulte.com/revue/irbm/International audienceThe object of this study was to compute the mechanical power of the resultant braking force during an actual propulsion cycle with a manual wheelchair on the field. The resultant braking force was calculated from a mechanical model taking into account the rolling resistances of the front and rear wheels. Both the resultant braking force and the wheelchair velocity were not constant during the propulsion cycle and varied according to the subject's fore-and-aft and vertical movements in the wheelchair. These variations had logical repercussions on the braking force mechanical power, which ranged from 20.6 to 34.5 W (mean = 29.6 W) during the propulsion cycle. The mechanical power was also calculated from the conditions of a classical drag-test, by the product of the cycle mean velocity and a constant braking force corresponding to a 60 % rear wheels distribution of the subject-and- wheelchair's weight. This second mechanical power (32.4 W) was 10 % higher than the average of the instantaneous power. Beyond the need of a clear definition of the two phases of the propulsion cycle, this study showed that the assumption on wheelchair locomotion usually admitted on laboratory ergometers cannot be applied in field studies, and that the kinetic energy variations during the cycle propulsive phase should be considered for evaluating the subject's mechanical work and power

COMPARISON OF PEAK LUMBAR LORDOSIS BETWEEN SOME BASIC MOVEMENTS OF RHYTHMIC GYMNASTICS

To assist coaches in managing gymnasts, a good knowledge of the movements most likely to cause back pain is required. In rhythmic gymnastics (RG), this can be considered as identifying movements involving very high lumbar curvatures. To quantify the lumbar lordosis during some basic RG movements (ring, penché, penché with rotation, split leap, turning split leap, and front and back walkovers), eight gymnasts were enrolled and a 3D motion analysis was performed based on motion capture data, a musculoskeletal model and low-dose biplanar radiographs for model personalisation purposes. The ring and both the front and back walkovers were the movements studied involving the lumbar spine in extension the most but also resulting in the highest dispersion between gymnasts. Hence, future works should investigate the causes of this greater dispersion

Comparison of hip joint mechanical energetics in table tennis forehand and backhand drives: a preliminary study

Hip joints are highly involved in table tennis. Some authors found both pelvic angular velocity and hip joint torques are related to the racket velocity. Others have also demonstrated how some of the best players have higher ranges of motion of the lower-limb joints. Therefore, the mechanical work generated by the playing-side-hip can be seen as indicator of the playing intensity associated with different strokes. The aim of this study was to quantify the hip joint mechanical work and power during four classical strokes. Motion capture acquisitions were performed on two international players. A biplanar radiographic acquisition was also performed to personalize the biomechanical model. Hip joint velocity and torques were calculated on the dominant side, allowing mechanical power and work to be calculated between the end of backswing and the ball impact. The highest level of mechanical work from the hip joint was found for forehand drive against backspin and forehand topspin drive with pivot. A backhand drive required the lowest hip mechanical work, and the forehand drive against topspin was found to be intermediate. The lower work required from the backhand stroke makes it suitable as a waiting stroke

A method for the field assessment of rolling resistance properties of manual wheelchairs, Computer Methods in Biomechanics and Biomedical Engineering

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.The authors would like to thank the French National Research Agency (ANR) for its financial support to the SACR-FRM project (ANR-06-TecSan-020) and to the CERAH for the loan of all the manual wheelchairs evaluated in this work

IS BALL-RACKET CONTACT CONCOMITANT WITH THE MAXIMAL RACKET SPEED IN YOUNG TRAINED TABLE TENNIS PLAYERS?

Previous table tennis studies have broadly assumed the racket to reach its maximal speed at ball-racket impact but only few identified this instant experimentally. Hence, there remains a lack of information regarding the validity of this hypothesis and therefore a need to develop a strategy to identify ball-racket contact that can be implemented into future experimentations. A 3D motion capture system was used to measure racket movements of seven young talents (12.6 ± 0.8 years old) -a category that had not been tested yet- during topspin forehand and backhand drives. Ball-racket impacts were identified with a synchronized microphone. Maximal racket speed and sound peak occurrences were compared, and racket parameters (speed, orientation) were calculated at both events. Differences emerged when examining participants individually for forehand drives and over the whole cohort for backhand drives, with consequences on both racket orientation and speed between the two events. As it was shown that ball-racket contact is not always concomitant with the maximal racket speed, futures studies should add supplementary equipment such as a synchronized microphone to identify the exact impact time

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.International audienceThis 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

On the use of knee functional calibration to determine the medio-lateral axis of the femur in gait analysis: Comparison with EOS biplanar radiographs as reference

Accurate calibration of the medio-lateral axis of the femur is crucial for clinical decision making based on gait analysis. This study proposes a protocol utilizing biplanar radiographs to provide a reference medio-lateral axis based on the anatomy of the femur. The biplanar radiographs allowed 3D modelling of the bones of the lower limbs and the markers used for motion capture, in the standing posture. A comprehensive analysis was performed and results from biplanar radiographs were reliable for 3D marker localization (±0.35 mm) and for 3D localization of the anatomical landmarks (±1 mm), leading to a precision of 1° for the orientation of the condylar axis of the femur and a 95% confidence interval of ±3° after registration with motion capture data. The anatomical condylar axis was compared to a conventional, marker-based, axis and three functional calibration techniques (axis transformation, geometric axis fit and DynaKAD). Results for the conventional method show an average difference with the condylar axis of 15° (SD: 6°). Results indicate DynaKAD functional axis was the closest to the anatomical condylar axis, mean: 1° (SD: 5°) when applied to passive knee flexion movement. However, the range of the results exceeded 15° for all methods. Hence, the use of biplanar radiographs, or an alternative imaging technique, may be required to locate the medio-lateral axis of the femur reliably prior to clinical decision making for femur derotational osteotomies