Background and Aim: Accurate control of movement is one of the multiple components in skillful motor performance that can be impaired by disease. Trackingtests quantify the effects oftreatments designed toimprovecontrol of movement and they are considered as anideal protocol forimproving motor control. The purpose of the present study was to examine reliability of the control error during target tracking tasks in trunk region in sagittal transverse torque plane in healthy subjects.

Materials and Methods: Nine healthy subjects (4 females and 5 males) randomly performed target tracking tasks at levels of 0% to 80% Maximum Voluntary Exertions (MVE) and twelve different directions (0 ̊, 30 ̊, 60 ̊, …, 330 ̊) twice in upright standing posture. In this study, the tracking system included a moving target circle, which moved on a straight line in specific direction from 0 to 80% of individual MVE with speed of 6% MVE/S.The direction of isometric trunk exertion was presented to participants in the online visual feedback by a computer monitor positioned in front of them. Trunk controllability was determined by computing the control errors (Absolute Value Error from the Target [AVET], Error from the Target Path [ETP] and Error from the Target in the Target Path [ETTP]) during each performance. Relative reliability (Intra-class Correlation Coefficient [ICC]) of the control error in each direction was determined. Also absolute reliability (Standard Error of Measurement [SEM]) and Minimal Detected Change (MDC95) were computed.

Results:The results have shown that ICC for AVET, ETP and ETTP ranged from 0.81 to 0.99, 0.71 to 0.98 and 0.7 to 0.99, respectively. Also SEM for these variables ranged between 0.003- 0.013, 0.001- 0.009 and 0.003- 0.011, respectively and finally MDC95 ranged between 0.008 to 0.036 for AVET, 0.003 to 0.025 for ETP and 0.008 to 0.03 for ETTP.

Conclusion: The study showed high and very high reliability for control error measures during target tracking tasks in sagittal transverse torque plane in asymptomatic subjects. Therefore this performance may be used as a test in trunk controllability assessment.

Abstract

Background and aim: One of the important health problems in societies, especially among aged population is osteoporosis. Loss of bone density in bone structures is called osteoporosis which increases the risk of fracture due to a decrease of bone stiffness and bone strength. One of the most common sites for osteoporosis-related fractures is the spine. Current assessment of osteoporosis status is based on bone densitometry tools like QCT (Quantitative Computed Tomography) or DEXA (Dual Energy X-ray absorptionmetry). With these methods it is only possible to estimate density regardless of the morphology of trabecular constructing parts (rods and plates). The microstructure of cancellous bone in the vertebrae can be varied based on age, sex, race, etc. The cellular solids theory is a common procedure to model porous materials and we have attempted to present a model parametrical for trabecular bone as a rod like structure based on cellular solids method.

Materials & Methods: In order to model trabecular bone as foam, like what exists in vertebrae core, a finite element code has been written by APDL capability in ANSYS. This parametric code can produce different lattices that can represent various structural and material properties. Then each cubic sample was loaded under compression displacement to failure point to obtain the stress-strain curve. The stress-strain curve is used to calculate mechanical properties of simulated bone model. In order to compare with experimental results, the model has been reconstructed for 6 bone samples were taken from two different vertebrae donors one has 78 years old and the other one has 91 years old then stiffness and strength predictions have been done.

Results: The results have shown that the mechanical properties of experimental results fall between lower and upper limits of model output and it is due to unknown connectivity level for all samples. The model is capable of presenting a band for mechanical properties. Plus the lattices that simulated bone samples taken from cadavers can predict stiffness and strength better than density-based relationships for mechanical properties.

Conclusion: According to the findings of the current study, the strength and stiffness or other mechanical properties of trabecular tissues in vertebrae are highly affected by many parameters like material specification of bone tissue and morphology characteristics like connectivity. It can be concluded that risk of fracture in vertebrae is a function of various factors beyond the bone mineral density that is evaluated by measurements such as DEXA and QCT. This has been shown that our cellular solid model may improve the assessments of mechanical properties of trabecular bone structures.

Keywords: Cellular solids, Risk of fracture, Vertebrae, Trabecular bone, Finite element model

Background and Aim: The target tracking tests is a known method to quantify the performance of the neuromuscular system. It has been used in several studies for evaluation of neuromuscular control strategies. The purpose of the present study was to examine the effect of direction and speed of isometric trunk exertion on the trunk controllability during the target tracking tests in sagittal versus axial rotation torque plane.

Materials and Methods: Twenty- two healthy subjects (13 female and 9 male) randomly performed target tracking tasks at levels of 0% to 80% Maximum Voluntary Exertions (MVE) and seven different directions (0 ̊ , 30 ̊ , 60 ̊ , …, 180 ̊ ) in upright standing posture. In this study, the tracking system included a moving target circle, which moved on a straight line in specific direction from 0 to 80% of individual MVE with speed of 5, 6 and 7% MVE/s . The d irection of isometric trunk exertion was presented to participants in the real time visual feedback by a computer monitor positioned in front of them. Trunk controllability was determined by computing the control errors (Absolute Value Error from the Target [AVET], Error from the Target Path [ETP] and Error from the Target in the Target Path [ETTP]) during each performance. Analysis of variance was used to test the effect of speed and direction of isometric trunk exertion on trunk controllability.

Results: The results have shown that the direction of isometric trunk exertion had significant effect on the AVET and ETTP (p= 0.000) while the effect of speed and interaction between direction and speed were not significant. The error decomposition in to two independent parts showed that the only direction of exertion on ETTP was significant (p= 0.000) and speed of exertion on any of them ( ETP and ETTP ) was not significant. On the other hand, Borg scale (a simple method of rating perceived exertion) significantly affected by direction (p= 0.000) and speed (p= 0.000) of exertion during the target tracking tests.

Conclusion: According to the findings of the current study, the effect of d irection of isometric trunk exertion on the controllability was significant. Trunk controllability was significantly decreased during rotational exertions which may impair trunk neuromuscular coordination, increasing the risk of developing low back pain.

Keywords: Target t racking t ests , T runk controllability , Speed and d irectio n of isometric trunk exertion

Background and Aim : The tracking tests are a known method to measure and quantify the performance of the neuromuscular system. They are also one of the accurate and flexible methods for measurement of the performance capacity of sensory-motor control or sensory-motor coordination. The purpose of the present study was to examine reliability of the torque error during trajectory tracking tasks in trunk region in torque-time plane in healthy subjects.

Materials and Methods: Twenty healthy subjects (7 female and 13 male) randomly performed target tracking tasks with two patterns (sinusoidal and saw shape). The sinus and saw tracking tasks had two periodic cycles included 10 seconds (3 cycles) and 15 seconds (2 cycles). The amplitude of the signal was set at about 30% to 70% of Maximum Voluntary Exertions (MVE) of each participant. The tracking tasks were performed in 6 directions of uniaxial exertion (flexion, extension, left and right rotation, and left and right lateral bending). Absolute error mean and the performance of the tracking task were determined by calculating Relative Root Mean Square Error (RRMSE) for each participant during each trial. Relative reliability (Intraclass Correlation Coefficient: ICC) of the error mean and RRMSE for all participants was determined. Also absolute reliability (Standard Error of Measurement: SEM) and Minimal Detected Change ( MDC₉₅ ) were computed.

Results: The results have shown that ICC, SEM and MDC₉₅ for error mean ranged from 0.5 to 0.87, 0.002 to 0.006 and 0.007 to 0.016, respectively. Also these variables for RRMSE ranged between 0.5- 0.86, 0.05- 0.024 and 0.065- 0.139, respectively.

Conclusion: The repeatability analysis showed high and very high reliability for torque errors ( Error Mean, RRMSE ) measures during trajectory tracking tasks in torque time plane in asymptomatic subjects. Therefore this performance can be used for quantification of trunk controllability and also mentioned variables as reliable parameters in researches.

Keywords: Reliability, Trajectory tracking tests, Torque error, Isometric trunk exertion