Joint loads and muscle force distribution during classical and jazz pirouettes

Purpose: The objective of this study was to analyze the muscle force distribution and lower limb joint loading during two types of pirouettes and check which muscle in which pirouette generates the highest force and which joint is the most loaded. Methods: Skilled dancers (n = 16) performed single-turn pirouettes in jazz and classic styles. Kinematic and kinetic data were collected using the Vicon system and Kistler plates. The joint reaction forces and muscle forces were calculated using a musculoskeletal model in the AnyBody Modeling System. Results: No statistically significant differences were found for the duration of the turn in both pirouettes. The range of motion in all joints of supporting leg in sagittal plane and in hip joint in frontal plane for non-supporting leg were significantly higher in classic pirouette. The ankle joint was the most loaded joint in both pirouettes and its maximal value was significantly higher in classic pirouette. The force generated by ankle plantar flexors muscles was significantly greater in the jazz pirouette in turn phase. For the nonsupport limb, external hip rotators generated significantly greater force when performing the classic pirouette. Conclusions: It seems that early stage dancers may start their lessons with jazz pirouettes, where necessary joint mobility is lesser. They also are supposed to increase muscle strength and body awareness with such proceedings. A better awareness of the mechanical loads on the musculoskeletal system which a dancer performing pirouettes faces should have an impact on the way dance classes are conducted and choreographic elements are sequenced.

How does the ski boot affect human gait and joint loading?

Study aim: To investigate the effect of wearing ski boots on kinematic and kinetic parameters of lower limbs during gait. Furthermore, loads in lower limb joints were assessed using the musculoskeletal model. Material and methods: The study examined 10 healthy women with shoe size 40 (EUR). Kinematic and kinetic data of walking in ski boots and barefoot were collected using a Vicon system and Kistler plates. A musculoskeletal model derived from AnyBody Modeling System was used to calculate joint reaction forces. Results: Wearing ski boots caused the range of motion in the knee joint to be significantly smaller and the hip joint to be significantly larger. Muscle torques were significantly greater in walking in ski boots for the knee and hip joints. Wearing ski boots reduced the reaction forces in the lower limb joints by 18% for the ankle, 16% for the knee, and 39% for the hip. Conclusions: Ski boot causes changes in the ranges of angles in the lower limb joints and increases muscle torques in the knee and hip joints but it does not increase the load on the joints. Walking in a ski boot is not destructive in terms of forces acting in the lower limb joints.

Assessing the efficiency of exoskeletons in physical strain reduction by biomechanical simulation with AnyBody Modeling System

Introduction Recently, many industrial exoskeletons for supporting workers in heavy physical tasks have been developed. However, the efficiency of exoskeletons with regard to physical strain reduction has not been fully proved, yet. Several laboratory and field studies have been conducted, but still more data, that cannot be obtained solely by behavioral experiments, are needed to investigate effects on the human body. Methods This paper presents an approach to extend laboratory and field research with biomechanical simulations using the AnyBody Modeling System. Based on a dataset recorded in a laboratory experiment with 12 participants using the exoskeleton Paexo Shoulder in an overhead task, the same situation was reproduced in a virtual environment and analyzed with biomechanical simulation. Results Simulation results indicate that the exoskeleton substantially reduces muscle activity and joint reaction forces in relevant body areas. Deltoid muscle activity and glenohumeral joint forces in the shoulder were decreased between 54 and 87%. Simultanously, no increases of muscle activity and forces in other body areas were observed. Discussion This study demonstrates how a simulation framework could be used to evaluate changes in internal body loads as a result of wearing exoskeletons. Biomechanical simulation results widely agree with experimental measurements in the previous laboratory experiment and supplement such by providing an insight into effects on the human musculoskeletal system. They confirm that Paexo Shoulder is an effective device to reduce physical strain in overhead tasks. The framework can be extended with further parameters, allowing investigations for product design and evaluation.

A NOVEL GAIT TRAINING DEVICE FOR BEDRIDDEN PATIENTS’ REHABILITATION

To assist bedridden patients to do rehabilitation exercise in bed, a kind of adjustable rehabilitation training device was designed and kinematic analysis was performed on the model of this device. It is shown that this device can generate trajectory similar to the ankle trajectory of normal gait. Based on the analysis, the human–machine integrated model was then built and biomechanical analysis was applied on it by AnyBody Modeling System. Regarding the forces of some mainly used muscles as study object, the mapping relationships between patient’s posture and tendon forces under the same conditions were analyzed, all these results suggested that this novel device has the capacity to train different muscles with the most appropriate postures and thus it has the potential application in future.

Physical Stresses on Caregivers when Pulling Patients Up in Bed: Effect of Repositioning Aids and Patient Weight

Manual patient handling is a major cause of musculoskeletal disorders (MSDs) among caregivers. Pulling patients up in bed (PUIB) is one of the most frequently performed patient handling activities, for which repositioning aids are usually recommended. However, it is not clear how to choose repositioning aids for a patient of a given weight, such that the risk of MSDs can be reduced. The current study investigates the physical stresses on caregivers across three patient weight levels, and for common types of repositioning aids during the PUIB activity. Ten caregivers were recruited to preform PUIB tasks while motion capture, ground reaction force, and hand reaction force were measured. Spinal compressive load (L5/S1) was estimated using AnyBody Modeling System software. Repositioning aids and patient weight significantly affected the physical stresses on caregivers. Peak L5/S1 compressive load, peak pulling force, and perceived exertion were lowest for the air-assisted repositioning devices, second lowest for the friction reducing sheet, second highest for the turn and position systems, and highest for the draw sheet. Except for the air-assisted repositioning device, other tested repositioning aids are not adequate to mitigate the risk of MSDs. A mechanical lift should be considered as a robust alternative to repositioning aids that can safely accommodate all patient regardless of weight.

Muscle-Tendon Unit Parameter Estimation of a Hill-Type Musculoskeletal Model Based on Experimentally Obtained Subject-Specific Torque Profiles

The aim of this study was to generate a subject-specific musculoskeletal muscle model, based on isometric and isovelocity measurements of the whole lower extremity. A two-step optimization procedure is presented for optimizing the muscle-tendon parameters (MTPs) for isometric and isovelocity joint torque profiles. A significant improvement in the prediction of joint torque profiles for both the solely isometric and a combined isometric and dynamic method of optimization when compared to the standard scaling method of the AnyBody Modeling System (AMS) was observed. Depending on the specific purpose of the model, it may be worth considering whether the isometric-only would be sufficient, or the additional dynamic data are required for the combined approach.