Simultaneous in-air and underwater 3D kinematic analysis of swimmers: Feasibility and reliability of action sport cameras.

This study explored the potential of reconstructing the 3D motion of a swimmer's hands with accuracy and consistency using action sport cameras (ASC) distributed in-air and underwater. To record at least two stroke cycles of an athlete performing a front crawl task, the cameras were properly calibrated to cover an acquisition volume of 3 m in X, 8 m in Y, and 3.5 m in Z axis, approximately.

Postural adjustments preceding string release in trained archers.

Optimal postural stability is required to perform in archery. Since the dynamic consequences of the string release may disturb postural equilibrium, they should be integrated into an archer motor programme to optimize postural stability. This study aimed to characterize the postural strategy archers use to limit the potentially detrimental impact of the bow release on their postural stability and identify characteristics that may explain a better performance.

Biomechanical comparison between manual and motorless device assisted patient handling: sitting to and from standing position.

Although lots of assistive devices have been studied to fight against caregivers' work-related musculoskeletal disorders, stand-and-turn devices effects on biomechanical constraints are still unknown. The aim of this study is to provide and compare quantitative data on loads in the low back area resulting from the use of a motorless stand-and-turn device and from manual patient handling. Nine caregivers participated to motion capture and ground reaction forces measurement sessions of three cases of handling: manual handling with one caregiver, manual handling with two caregivers, motorless device assisted handling.

Reliability of a Repeated High-Intensity Effort Test for Elite Rugby Union Players.

This study aimed to adapt a repeated high-intensity effort (RHIE) test to the rugby union physical demands and assess both sprint time and tackle indices reliability. Following a familiarization session, sixteen elite rugby union players completed two RHIE tests consisting of 12 × 20 m sprint + tackle. Total sprint time and total g-force during tackling, average sprint time and average g-force as well as percentage decrement and percentage decrement were considered for the analysis.

Moving system with action sport cameras: 3D kinematics of the walking and running in a large volume.

Traditionally, motion analysis in clinical laboratories using optoelectronic systems (MOCAP) is performed in acquisition volumes of limited size. Given the complexity and cost of MOCAP in larger volumes, action sports cameras (ASC) represent an alternative approach in which the cameras move along with the subject during the movement task. Thus, this study aims to compare ASC against a traditional MOCAP in the perspective of reconstructing walking and running movements in large spatial volumes, which extend over the common laboratory setup.

Identification of Noise Covariance Matrices to Improve Orientation Estimation by Kalman Filter.

Magneto-inertial measurement units (MIMUs) are a promising way to perform human motion analysis outside the laboratory. To do so, in the literature, orientation provided by an MIMU is used to deduce body segment orientation. This is generally achieved by means of a Kalman filter that fuses acceleration, angular velocity, and magnetic field measures.

Are Action Sport Cameras Accurate Enough for 3D Motion Analysis? A Comparison With a Commercial Motion Capture System.

The aim of this study was to assess the precision and accuracy of an Action Sport Camera (ASC) system (4 GoPro Hero3+ Black) by comparison with a commercial motion capture (MOCAP) system (4 ViconMX40). Both systems were calibrated using the MOCAP protocol and the 3D markers coordinates of a T-shaped tool were reconstructed, concurrently. The 3D precision was evaluated by the differences in the reconstructed position using a Bland-Altman test, while accuracy was assessed by a rigid bar test (Wilcoxon rank sum).

Simple and efficient thermal calibration for MEMS gyroscopes.

Gyroscopes are now becoming one of the most sold MEMS sensors, given that the many applications that require their use are booming. In the medical field, gyroscopes can be found in Inertial Measurement Units used for the development of clinical tools that are dedicated to human-movement monitoring. However, MEMS gyroscopes are known to suffer from a drift phenomenon, which is mainly due to temperature variations.

Comparative study between fully tethered and free swimming at different paces of swimming in front crawl.

Tethered swimming is a method often used to measure or enhance the physical and technical resources of swimmers. Although it is highlighted that the technique used in tethered swimming is probably different from that used in free conditions, there are few comparative studies on this subject. The current study aims to compare fully tethered and free swimming based on kinematic hand parameters (orientation, velocity and acceleration of the hand, sweepback and angle of attack), which are known to act directly on the generation of propulsive forces.

Unsteady computational fluid dynamics in front crawl swimming.

The development of codes and power calculations currently allows the simulation of increasingly complex flows, especially in the turbulent regime. Swimming research should benefit from these technological advances to try to better understand the dynamic mechanisms involved in swimming. An unsteady Computational Fluid Dynamics (CFD) study is conducted in crawl, in order to analyse the propulsive forces generated by the hand and forearm.

Comparison of calibration methods for accelerometers used in human motion analysis.

In the fields of medicine and biomechanics, MEMS accelerometers are increasingly used to perform activity recognition by directly measuring acceleration; to calculate speed and position by numerical integration of the signal; or to estimate the orientation of body parts in combination with gyroscopes. For some of these applications, a highly accurate estimation of the acceleration is required. Many authors suggest improving result accuracy by updating sensor calibration parameters.

Kinematic hand parameters in front crawl at different paces of swimming.

The aim of this study was to investigate the evolution of kinematic hand parameters (sweepback angle, angle of attack, velocity, acceleration and orientation of the hand relative to the absolute coordinate system) throughout an aquatic stroke and to study the possible modifications caused by a variation of the swimming pace. Seventeen competitive swimmers swam at long distance, middle distance and sprint paces. Parameters were calculated from the trajectory of seven markers on the hand measured with an optoelectronic system.

Can optimal marker weightings improve thoracohumeral kinematics accuracy?

Local and global optimization algorithms have been developed to estimate joint kinematics to reducing soft movement artifact (STA). Such algorithms can include weightings to account for different STA occur at each marker. The objective was to quantify the benefit of optimal weighting and determine if optimal marker weightings can improve humerus kinematics accuracy.

The role of the entry-and-stretch phase at the different paces of race in front crawl swimming.

The aim of this study was to determine the role played by the entry-and-stretch phase in the coordination of swimming, at the different paces of race. Three national level swimmers (two men and one woman) were recorded, in lateral and bottom views, in three swimming paces: sprint (50 m and 100 m), middle-distance (200 m and 400 m) and long-distance (800 m and 1500 m). Anatomical landmark positions were obtained by manual digitalisation of the videos.

Segment-embedded frame definition affects the hip joint centre precision during walking.

Due to marker-specific soft tissue artefacts, the choice of the markers defining the segment-embedded frame affects the functional joint centre location, with subsequent error propagation to joint kinematics and kinetics in gait analysis. Our aim was to assess the effect of the number and placement of markers on the precision of the hip joint centre (HJC) location during walking. Twelve markers (2x6) were attached to the pelvis and left thigh of 15 young male subjects.

Assessment of reproducibility of thigh marker ranking during walking and landing tasks.

The aim of this paper is to analyse the repeatability of marker deformation and marker ranking across subjects and motor tasks. A method based on the solidification of the thigh with optimized rototranslation was applied which used 26 markers placed on the left thigh. During five trials of landing and five trials of walking for eight participants, the deformation between the actual positions of the 26 markers and the recalled positions from solidification were calculated.

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.

Comparison of the SCoRE and HA methods for locating in vivo the glenohumeral joint centre.

A recent paper has described a new functional method, the symmetrical centre of rotation (SCoRE), for locating joint centre position [Ehrig, R.M., Taylor, W.