Molecular dynamics simulations showing 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) membrane mechanoporation damage under different strain paths.

Continuum finite element material models used for traumatic brain injury lack local injury parameters necessitating nanoscale mechanical injury mechanisms be incorporated. One such mechanism is membrane mechanoporation, which can occur during physical insults and can be devastating to cells, depending on the level of disruption. The current study investigates the strain state dependence of phospholipid bilayer mechanoporation and failure. Using molecular dynamics, a simplified membrane, consisting of 72 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) phospholipids, was subjected to equibiaxial, 2:1 non-equibiaxial, 4:1 non-equibiaxial, strip biaxial, and uniaxial tensile deformations at a von Mises strain rate of 5.45 × 108 s-1, resulting in velocities in the range of 1 to 4.6 m·s-1. A water bridge forming through both phospholipid bilayer leaflets was used to determine structural failure. The stress magnitude, failure strain, headgroup clustering, and damage responses were found to be strain state-dependent. The strain state order of detrimentality in descending order was equibiaxial, 2:1 non-equibiaxial, 4:1 non-equibiaxial, strip biaxial, and uniaxial. The phospholipid bilayer failed at von Mises strains of .46, .47, .53, .77, and 1.67 during these respective strain path simulations. Additionally, a Membrane Failure Limit Diagram (MFLD) was created using the pore nucleation, growth, and failure strains to demonstrate safe and unsafe membrane deformation regions. This MFLD allowed representative equations to be derived to predict membrane failure from in-plane strains. These results provide the basis to implement a more accurate mechano-physiological internal state variable continuum model that captures lower length scale damage and will aid in developing higher fidelity injury models.

Differential effects of primary motor cortex and cerebellar transcranial direct current stimulation on motor learning in healthy individuals: A randomized double-blind sham-controlled study.

The purpose of study was to compare the effect of primary motor cortex (M1) and cerebellar anodal transcranial direct current stimulation (a-tDCS) on online and offline motor learning in healthy individuals. Fifty-nine healthy volunteers were randomly divided into three groups (n=20 in two experimental groups and n=19 in sham-control group). One experimental group received M1a-tDCSand another received cerebellar a-tDCS. The main outcome measure were response time (RT) and number of errors during serial response time test (SRTT) which were assessed prior, 35min and 48h after the interventions. Reduction of response time (RT) and error numbers at last block of the test compared to the first block was considered online learning. Comparison of assessments during retention tests was considered as short-term and long-term offline learning. Online RT reduction was not different among groups (P>0.05), while online error reduction was significantly greater in cerebellar a-tDCS than sham-control group (P<0.017). Moreover, a-tDCS on both M1 and cerebellar regions produced more long-term offline learning as compared to sham tDCS (P<0.01), while short-term offline RT reduction was significantly greater in M1a-tDCS than sham-control group (P<0.05). The findings indicated that although cerebellar a-tDCS enhances online learning and M1a-tDCS has more effect on short-term offline learning, both M1 and cerebellar a-tDCS can be used as a boosting technique for improvement of offline motor learning in healthy individuals.

Effects of genu varum deformity on postural stability.

It is well known that any balance control disturbance can increase the risk of injury during sport activities. Knee deformities such as genu valgum and genu varum may perturb the line of gravity passing the lower limb joints and so disturb dynamic and static balance indices. This study was designed to investigate the effects of genu valgum and genu varum deformity on the static and dynamic balance indices. 90 non-athletic female university students (age: 21.8±1.75 years, weight: 55.8±9.6 kg, height: 161.3±11.9 cm) were assigned in one of the 3 experimental groups; normal knee (n=30), genu varum (n=30) and genu valgum (n=30), according to their knee conditions. Static and dynamic overall stability index (OSI), anteroposterior stability index (APSI), mediolateral stability index (MLSI) and falling risk were evaluated by the Biodex balance system. No significant difference was seen among these groups in terms of dynamic and static OSI and APSI, while significantly higher falling risk and lower stability was found in the genu varum group compared to the normal groups in term of dynamic and static MLSI (p<0.05). The results showed that genu varum deformity may increase the normal postural sway in the mediolateral direction and also increase falling risk.

Cervical muscle strength measurement is dependent on the location of thoracic support.

BACKGROUND: In all studies in which the strength of the neck extensor muscles has been measured, the level of thoracic support has been adjusted differently so direct comparison of the results is not possible. OBJECTIVE: To measure and compare the isometric force and isometric torque of neck extensor muscles at different levels of thoracic support. METHODS: Twenty healthy women volunteered for the study. The maximum isometric force of the neck extensor muscles was measured with the thoracic support located at five different levels. The highest level was set at the level of the spine of the scapula (level I) and the other levels were located 2.5 cm lower than the previous one, with the lowest level set 10 cm below the highest level. The maximum isometric torque for each level was calculated by multiplying the isometric force by the length of the lever arm measured from the upper tip of the thoracic support to the centre point of the cell load at the occiput. RESULTS: The maximum isometric force and maximum isometric torque of the neck extensor muscles were increased step by step from 130.5 N to 138.9 N, 141.9 N, 147.9 N and 155.4 N and from 33.7 Nm to 38.7 Nm, 42.5 Nm, 47.2 Nm and 52.7 Nm, respectively. Except for the isometric force of the cervical extensor muscles measured at levels II and III, the differences between the other levels were significant (p<0.05). There was a significant correlation between isometric force and isometric torque measurements of the neck extensor muscles at different levels (0.81

Open versus closed kinetic chain exercises for patellar chondromalacia.

SUBJECT: Conservative treatment of patellar chondromalacia has been the subject of several studies. One recommended treatment is a strengthening exercise of the quadriceps muscle, which may be performed in closed or open kinetic chains. This study was designed to compare the effect of straight leg raise (SLR) and semi-squat exercises on the treatment of patellar chondromalacia, which has not been done to date. MATERIAL AND METHODS: 32 female university students with a diagnosis of patellar chondromalacia were randomly assigned to two experimental groups: SLR and semi-squat exercise. Before starting exercise protocols, Q angle, maximal isometric voluntary contraction force (MIVCF) of quadriceps, crepitation, circumference of thigh 5 and 10 cm above the patella and patellofemoral pain according to the visual analogue scale (VAS) were assessed. Both groups then followed a 3-week programme of quadriceps muscle strengthening exercises (SLR or semi-squat) starting with 20 exercises twice a day and increasing each session by 5 exercises every 2 days. All measurements were repeated at the end of each week and then again 2 weeks after the 3-week exercise programme. RESULTS: Reduced Q angle (mean differences (SD) 0.8 (0.3), p = 0.016) and crepitation (19.9 (8.5), p = 0.04), and an increase in the MIVCF of the quadriceps (15.8 (5.6), p = 0.01) and thigh circumference (1.5 (0.3), p = 0.001) were found in semi-squat group compared with SLR group. However, patellofemoral pain was decreased significantly in both groups. CONCLUSION: The results of this study indicate that semi-squat exercises (closed kinetic chain) are more effective than SLR exercise (open kinetic chain) in the treatment of patellar chondromalacia. More studies are needed to investigate the long-term effect of these types of exercise.

The effect of motor learning in facioscapulohumeral muscular dystrophy patients.

Two models of motor learning (ML) practice (complex and simple) were used to investigate upper limb function in individuals with facioscapulohumeral dystrophy (FSHD). The effect of ML practice was studied by examining changes in the ability to undertake a simulated drinking task. In the complex model, seven FSHD patients and seven age- and gender-matched healthy volunteers were studied. Performance was assessed by measurement of the electromyographic (EMG) activity of the biceps brachii and brachioradialis, elbow joint flexion, shoulder joint flexion and abduction, maximum acceleration at the onset of movement, movement time and reaction time, both before and after a 30-min complex ML task. In the simple model, a second group of six FSHD patients and six age- and gender-matched healthy subjects were studied. The same parameters were measured as for the complex ML task, except that the EMG activity of the triceps and deltoid muscles (anterior part) were measured instead of that of the brachioradialis. In both studies, the FSHD patients showed significantly larger values for all parameters except the flexion of shoulder joint and reaction time, compared with controls before the ML task. In the FSHD group, while the complex ML resulted in decreases in the brachioradialis EMG activity (P<0.005) and reaction time (P<0.0001), the simple ML model resulted in significant changes towards the normal value in all parameters measured except shoulder flexion. The change in the measured variables towards normal values indicates that ML may help to improve performance in FSHD.