Estimating individual muscle forces in human movement

If individual muscle forces could be routinely calculated in vivo, non-invasively, considerable insight could be obtained into the etiology of injuries and the training of muscle for rehabilitation and sport. As there are generally more muscles crossing a joint than there are degrees of freedom at the joint, determining the individual forces in the muscles crossing a joint is a non-trivial problem. This study focused on the development of the procedures necessary to estimate the individual muscle forces during a dumbell curl, and the measurement procedures required for the determination of the necessary input parameters. The procedures developed could easily be applied to other body movements. [Continues.

Wobbling mass influence on impact ground reaction forces: A simulation model sensitivity analysis

To gain insight into joint loadings during impacts, wobbling mass models have been used. The aim of this study was to investigate the sensitivity of a wobbling mass model, of landing from a drop, to the model's parameters. A two-dimensional wobbling mass model was developed. Three rigid linked segments designed to represent the skeleton each had a second mass attached to them, via two translational non-linear spring dampers, representing the soft tissue. Model parameters were systematically varied one at a time and the effect this had on the peak vertical ground reaction force and segment kinematics was examined. Model output showed low sensitivity to most model parameters but was sensitive to the timing of joint torque initiation. Varying the heel pad stiffness in the range of stiffness values reported in the literature had the largest influence on the peak vertical ground reaction force. The analysis indicated that the more proximal body segments had a lower influence on peak vertical ground reaction force per unit mass than the segments nearer the contact point, 340 N/kg, 157 N/kg and 24 N/kg for the shank, thigh and trunk respectively. Model simulations were relatively insensitive to variations in the properties of the connection between the wobbling masses and the skeleton. Given the proviso that estimates for the other model parameters and joint torque activation timings lie in a realistic range, then if the goal is to examine the effects of the wobbling mass on the system this insensitivity is an advantage. If precise knowledge about the motion of the wobbling mass is of interest, however, more experimental work is required to determine precisely these model parameters

Soft tissue motion influences skeletal loads during impacts

Soft tissue motion occurs as impulsive loads are applied to the skeletal system. It has been demonstrated that the wave like motion of these wobbling masses can reduce the loads acting on the musculoskeletal system. This is an important concept to consider, whether the loads acting on the musculoskeletal system are being determined using either inverse or direct dynamics

The influence of soft tissue movement on ground reaction forces, joint torques and joint reaction forces in drop landings

The aim of this study was to determine the effects that soft tissue motion has on ground reaction forces, joint torques and joint reaction forces in drop landings. To this end a four body-segment wobbling mass model was developed to reproduce the vertical ground reaction force curve for the first 100 ms of landing. Particular attention was paid to the passive impact phase, while selecting most model parameters a priori, thus permitting examination of the rigid body assumption on system kinetics. A two-dimensional wobbling mass model was developed in DADS (version 9.00, CADSI) to simulate landing from a drop of 43 cm. Subject specific inertia parameters were calculated for both the rigid links and the wobbling masses. The magnitude and frequency response of the soft tissue of the subject to impulsive loading was measured and used as a criterion for assessing the wobbling mass motion. The model successfully reproduced the vertical ground reaction force for the first 100 ms of the landing with a peak vertical ground reaction force error of 1.2 % and root mean square errors of 5% for the first 15 ms and 12% for the first 40 ms. The resultant joint forces and torques were lower for the wobbling mass model compared with a rigid body model, up to nearly 50% lower, indicating the important contribution of the wobbling masses on reducing system loading

The role of the heel pad and shank soft tissue during impacts: a further resolution of a paradox

The aim of this study was to test the hypothesis that by accounting for soft tissue motion of the lower leg during the impacts associated with in vivo testing, that the differences between in vivo and in vitro estimates of heel pad properties can be explained. To examine this a two-dimensional model of the shank and heel pad was developed using DADS. The model contained a heel pad element and a rigid skeleton to which was connected soft tissue which could move relative to the bone. Simulations permitted estimation of heel pad properties directly from heel pad deformations, and from the kinematics of an impacting pendulum. These two approaches paralleled those used in vitro and in vivo respectively. Measurements from the pendulum indicated that heel pad properties changed from those found in vitro to those found in vivo as relative motion of the bone and soft tissue was allowed. This would indicate that pendulum measures of the in vivo heel pad properties are also measuring the properties of the whole lower leg. The ability of the wobbling mass of the shank to dissipate energy during an impact was found to be significant. These results demonstrate the important role of both the heel pad and soft tissue of the shank to the dissipation of mechanical energy during impacts. These results provide a further clarification of the paradox between the measurements of heel pad properties made in vivo and in vitro

sj-pdf-1-spo-10.1177_17479541241247308 - Supplemental material for The relationship between ball mass and throw distance: Implications for coaching practice

Supplemental material, sj-pdf-1-spo-10.1177_17479541241247308 for The relationship between ball mass and throw distance: Implications for coaching practice by John H. Challis in International Journal of Sports Science & Coaching</p

Fig 3 -

Comparison of ankle angular velocities during stance computed using two different foot models: SINGLE—single segment foot (solid blue), MULTI—multi-segment foot (dotted red). Data computed from barefoot running at 3.1 m/s. Shaded regions show ± 1 S.D. The top row shows ankle angular velocities throughout the stance phase. Angle conventions are inversion(+)/eversion(-), abduction(+)/adduction(-), and dorsiflexion(+)/plantarflexion(-). The bottom row shows results from paired t-tests btween SINGLE and MULTI with the red dotted lines representing the t-statistic threshold for statistical significance. Gray shaded areas outside of the red dotted lines show regions with significant differences between SINGLE and MULTI.</p

Comparison of positive joint work performed at each joint in the two foot models.

The multi-segment foot model (MULTI) is the left bar group, and the single segment foot model (SINGLE) is the right bar. Ankle positive work (dark blue) was significantly different between the foot models, but the summed ankle and midfoot from MULTI (gray bar) was similar to ankle joint work from SINGLE (dark blue), suggesting that SINGLE captured midfoot joint power in the ankle joint power.</p

An integrated concept of Islamic education : a study on Islamic education in Muslim religious secondary schools in Selangor, Malaysia

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Fig 1 -

The segment reference frames for the multi-segment foot model (left), marker set (center), and the two foot models (right). The SHANK reference frame was the same for both models and the single segment foot reference frame in SINGLE was the same as the RF reference frame in MULTI. The multi-segment foot model included three segments (RF = rearfoot, FF = forefoot, and TOE). In each reference frame, the red arrow indicates the x-axis, the green arrow indicates the y-axis, and the blue arrow indicates the z-axis. The labelled markers are those of the: M1B - base of the first metatarsal; M5H - fifth metatarsal head; T5—distal edge of middle phalanx of the fifth toe; M1H - first metatarsal head; and HAL—distal edge of the proximal phalanx of the hallux.</p