Floren Colloud

Middle and ring fingers are more exposed to pulley rupture than index and little during sport-climbing: a biomechanical explanation.

BACKGROUND Finger pulley injury is a common incident observed during sport-climbing. The total rupture of one or several pulleys is highly debilitating and requires surgical reconstruction and/or rehabilitation programs. Literature reports show that fingers are not equally exposed to this injury. The ring and middle fingers are usually injured while the index and little fingers are less exposed. The objective of this study was to determine the biomechanical factors leading to the enhanced exposure of ring and middle finger pulleys. METHOD Eight subjects were required to exert maximal four-finger force in a specific sport-climbing finger posture. External fingertip forces and finger joint postures were used as input data of a specifically developed biomechanical model of the four fingers (i.e., index, middle, ring and little). This model was based on classical Newton static laws and used an optimization process to quantify the flexor tendon tensions and the pulley forces in each finger. Passive participation of ligaments was also considered into mechanical equations. FINDINGS Results showed that two main factors could explain the enhanced exposure of ring and middle fingers. Firstly, the fingertip force intensities applied by these two fingers were higher than those observed for the index and little fingers. Secondly, results show that the pulley forces of the ring and middle fingers were close to their rupture thresholds, while it was not the case for the two other fingers. This could be explained by a specific localisation of the finger pulleys of the ring and middle fingers leading to enhanced pulley forces. INTERPRETATION These results are relevant and could help clinicians to understand finger pulley pathologies and adapt the surgical interventions to reconstruct the fingers pulleys.

Improvement of upper extremity kinematics estimation using a subject-specific forearm model implemented in a kinematic chain

Human movement reconstruction is still difficult due to noise generated by the use of skin markers. The a priori definition of a kinematic chain associated with a global optimisation method allows reducing these deleterious effects. When dealing with the forearm, this approach can be improved by personalising the two axes of rotation because their common modelling is not representative of joint geometry. The aim of the present study is to evaluate the kinematic effects of personalising these two axes of rotation, determined by a functional method and implemented in a kinematic chain (AXIS model). The AXIS model was compared with a reference model (ISB model), in which the forearm axes of rotation were defined according to the recommendations of the International Society of Biomechanics. The kinematic comparison (15 subjects and 3 tasks) was based on marker residuals (actual versus model-determined), joint kinematic root mean square differences (AXIS versus ISB) and joint amplitudes (AXIS versus ISB). The AXIS model improved the pose of the forearm and hand. The reduction in marker residuals for these segments ranged between 23% and 60%. The use of a functional method was also beneficial in personalising the flexion-extension and pronation-supination axes of the forearm. The contribution of pronation-supination, in terms of joint amplitudes, was increased by 15% during the specific task. The approach developed in this study is all the more interesting since this forearm model could be integrated into a kinematic chain to be used with a global approach becoming increasingly popular in biomechanics.

Relative shank to thigh length is associated with different mechanisms of power production during elite male ergometer rowing

The effect of anthropometric differences in shank to thigh length ratio upon timing and magnitude of joint power production during the drive phase of the rowing stroke was investigated in 14 elite male rowers. Rowers were tested on the RowPerfect ergometer which was instrumented at the handle and foot stretcher to measure force generation, and a nine segment inverse dynamics model used to calculate the rowers joint and overall power production. Rowers were divided into two groups according to relative shank thigh ratio. Time to half lumbar power generation was significantly earlier in shorter shank rowers (p = 0.028) compared to longer shank rowers, who showed no lumbar power generation during the same period of the drive phase. Rowers with a relatively shorter shank demonstrated earlier lumbar power generation during the drive phase resulting from restricted rotation of the pelvic segment requiring increased lumbar extension in these rowers. Earlier lumbar power generation and extension did not appear to directly affect performance measures of the short shank group, and so can be attributed to a technical adaptation developed to maximise rowing performance.

Computation of the 3D kinematics in a global frame over a 40m-long pathway using a rolling motion analysis system

A rolling motion analysis system has been purpose-built to acquire an accurate three-dimensional kinematics of human motion with large displacement. Using this device, the kinematics is collected in a local frame associated with the rolling motion analysis system. The purpose of this paper is to express the local kinematics of a subject walking on a 40 m-long pathway in a global system of co-ordinates. One participant performed five trials of walking while he was followed by a rolling eight camera optoelectronic motion analysis system. The kinematics of the trials were reconstructed in the global frame using two different algorithms and 82 markers placed on the floor organized in two parallel and horizontal lines. The maximal error ranged from 0.033 to 0.187 m (<0.5% of the volume diagonal). As a result, this device is accurate enough for acquiring the kinematics of cyclic activities with large displacements in ecological environment.

Asymmetry in elite rowers: effect of ergometer design and stroke rate.

Between limb movement asymmetries and foot force production asymmetries are thought to be detrimental for both rowers performance and risk of injury, particularly when rowing frequently on ergometers. Several ergometers with different designs can be used by rowers as part of their indoor training. Hence, this study aimed to compare asymmetries in lower limb joint kinematics and foot force production with respect to ergometer design and rowing intensity. A new symmetry index was proposed to assess these asymmetries in elite rowers during a test on three ergometers. Additionally, the asymmetry in lower limb length was assessed to investigate its relationship with kinematic and kinetic asymmetries. Parameters describing medium (5–10%) or high (>10%) asymmetries were compared between rowing ergometers and intensities. Results indicated medium asymmetries for the ankle joint angle and hip–knee joint accelerations and high asymmetries for the resultant force and the ankle joint acceleration associated with a low inter-stroke variability. Kinetic asymmetry was neither correlated to kinematic asymmetry nor with lower limb length asymmetry. The use of a mobile ergometer led to higher joint acceleration asymmetries. Further studies are necessary to investigate the relation between these findings and muscular adaptations that may increase the risk of lower-back injury.

Estimation of the 3D kinematics in kayak using an extended Kalman filter algorithm: a pilot study

During sports activities, acquisition of whole body 3D kinematics in ecological conditions is challenging. Although optoelectronic systems are the most accurate solution, they are not used in these conditions because of experimental constraints (e.g. variation of light conditions, size of the volume calibrated, etc). These difficulties dramatically increase in the case of aquatic sports, such as kayaking and rowing. Recently, Begon et al. (2009a) have solved an important technological lock by placing an optoelectronic system on a rolling frame. In this way, they increased the volume of measurement while keeping a good accuracy of 3D kinematic reconstruction. Estimating joint kinematics of a human chain model using a classical approach such as a global optimisation method (GO; Lu and O’Connor 1999) with a large number of markers remains time consuming. Moreover, in our case where some segments are hidden and closed loops on the feet and the paddle must be respected, the use of kinematic constraints may be helpful. To estimate the joint kinematics of a chain model, the extended Kalman filter with kinematic constraints (EKF), based on the Kalman filter and adapted to nonlinear systems, showed promising results in biomechanics (Halvorsen et al. 2008). The comparison between GO and EKF methods has already been assessed (De Groote et al. 2008). However, these authors did not evaluate the effects of the marker number on kinematics reconstruction. The purpose of this study is to compare an EKF algorithm to a GO algorithm using three sets of skin markers and closed-loop constraints.

How to reconstruct athlete movement during outdoor rowing? A pilot study

The gold standard in human biomechanics for measuring the three-dimensional (3D) whole-body movement of an athlete is to use an optoelectronic motion capture system and skin markers (Leardini et al. 2005). Skin markers placed on the athlete are directly used to reconstruct the whole-body movement, i.e. to calculate the joint angles, using either a direct, local or global numerical method (Lu and O’Connor 1999). Although this kind of motion capture system is appropriate for laboratory experiments, its use can be limited for outdoor measurements. This is the case for onwater sport activities, e.g. rowing. The acquisition volume needs to be large to record several cycles. The water will produce important light changes and make the placement of the cameras problematic. Moreover, using optoelectronic motion capture systems represents a non-negligible human and financial cost and can be time consuming. These last features will be problematic when workingwith athletes and coaches because they want easy-to-use equipment and immediate feedback that is usable during training sessions. An alternative to optoelectronic motion capture systems can be the use of inertial measurement units (IMUs). Generally, an IMU contains three components (a gyroscope, an accelerometer and a magnetometer) to give the orientation, i.e. the three rotation angles, of the body segment on which it lies (Cutti et al. 2008). However, using about 20 IMUs, i.e. one on each segment, will not meet the above exigencies asked by athletes and coaches. Thus, the final idea will be to place a few IMUs on key body segments and use an appropriate numerical method to obtain the whole-body movement during on-water rowing. To reach this main objective, a step-by-step approach was chosen. The goal of this first study was to develop numerical methods to reconstruct the 3D movement of the lower limbs. This choice was supported by the idea that the lower limbs would be easier to reconstruct than the upper limbs because their movement is more planar and involved fewer degrees of freedom (dof). The aim of this study was to assess the kinematic fidelity of reconstructed movements.

Joint action with a virtual robotic vs. human agent

Abstract Prior research has revealed that when performing joint action tasks with a human co-actor, we automatically form representations not only of our own action, but also of the action of the co-actor we are interacting with, creating an action discrimination problem. Studies suggest these processes are affected by the human/non-human nature of the agent the task is shared with. In two experiments (Experiments 1 and 2), we measured the Joint Simon Effect (JSE) as an index of action discrimination, using a virtual version of the joint go/no-go task in which the task was shared with a virtual robotic vs. human hand. Furthermore, both experiments tested whether the JSE was affected by sensorimotor experience during which the participant manipulated the virtual robotic hand via an exoskeleton (vs. passive observation of movements of the virtual robotic hand). Experiment 2 replicated Experiment 1, except that prior to the joint action task, participants were informed about the robotic vs. human nature of the two virtual hands (no such information was given in Experiment 1). Both experiments demonstrated a significant JSE, which did not differ between robotic and human partner. Analysis of the results further indicates that the JSE obtained in the robotic condition was not modified after manipulating the virtual robotic hand. These results suggest that the human vs. non-human appearance of the partner is not a determinant of joint action performance in virtual settings.

Kinematics of the lumbar muscles in rowing: a preliminary study

Rowing is a very physical activity requiring full range of joint motion associate with the generation of large forces at the feet and hands. The low back joints act to transfer these forces between the upper and lower extremities. As a result, low back injuries are the most common injuries observed in rowing, comprising 25–45% of the reported injuries requiring a medical attention (Teitz et al. 2001). Although many studies have been conducted on low back injuries in rowing during the last decades, only few clinical implications for the practitioners have been published until now. Like recent studies focused on asymmetry (e.g. Fohanno et al. 2015), the number and complexity of the structures involved make difficult to establish easyto-use indexes that would help practitioners to prevent rowers from low back injuries. The estimation of low back muscle kinematics may help to better understand the mechanisms that lead to low back injuries. This approach, however, requires (i) adapting prior musculoskeletal models published in gait analysis to both rowing specificities and (ii) estimating the low back muscles maximum passive length to be used as the reference. This study aimed at assessing low back muscles kinematics during rowing. We hypothesized that the maximum lengths reached by the low back muscles during the rowing cycle are close to their respective maximum passive lengths and individual technique leads to differences between rowers.

Action co-representation during task sharing and sensorimotor experience: A comparison study between Human-Human and Human-Robot interaction

Non-human agents are taking a growing place in our society, in various areas (e.g. professional, private or medical) and serving numerous purposes. Therefore, understanding the way we interact with them seems crucial. In this experiment, we focused on both Human-Human and Human-Robot Interactions. The goal of the study was to extend knowledge concerning action co-representation in task sharing. We aimed to demonstrate that prior sensorimotor experience with a virtual robotic hand (via an exoskeleton) could improve action co-representation of this agent. We used an extended version of the Simon task (Joint Simon task) to evaluate action co-representation of others action.