Evaluation of the Long-term Reliability of Motor Uni Discharge Rates obtained by Decomposition of the Surface Electromyographic Signal

This study evaluated the long-term reliability of motor unit discharge rates (MUDRs) during isometric contractions at 60% maximum voluntary contraction (MVC), obtained by decomposition of the surface electromyographic (sEMG) signal from the flexor carpi radialis (FCR) and tibialis anterior (TA). There were four test sessions: one week between sessions 1 and 2; six weeks between sessions 2, 3, and 4. Participants performed 3 maximal isometric contractions of the wrist flexors and 3-isometric ramp contractions to 60% MVC. A load cell and 5-pin electrode (dEMG System, Delsys, Inc., Boston, MA) were used to monitor force and sEMG, respectively. The MUDRs were obtained using the Precision Decomposition Algorithm III in the dEMG Analysis software, and calculated as the inverse of the smoothed firing intervals. The mean discharge rate was calculated during a one-second window centered at the plateau portion of the 60% MVC ramp contraction. Maximal isometric strength during wrist flexion and dorsiflexion was also monitored. Across the four test sessions, maximal isometric strength of the wrist flexors and dorsiflexors increased 10 and 11.85%, respectively (p’s0.94). The MUDRs for the FCR (5.2%) and TA (7.8%) also exhibited slight fluctuations across the four test sessions (p’s<0.01). The consistency of MUDR values within each subject was still considered good, as the intraclass correlation coefficient for both measures was R=0.79. It was concluded that the overall long-term reliability of MUDRs in both the FCR and TA was good

EFFECT OF IMPACT SURFACE ON EQUESTRIAN FALLS

This study examines the effect of impact surface on head kinematic response and maximum principal strain (MPS) for equestrian falls. A helmeted Hybrid Ill headform was dropped unrestrained onto three impact surfaces (steel, turf and sand) and three locations. Peak resultant linear acceleration, rotational acceleration and duration of the impact events were measured. A finite element brain model was used to calculate MPS. The results revealed that drops onto steel produced higher peak linear acceleration, rotational acceleration and MPS but lower impact durations than drops to turf and sand. However, despite lower MPS values, turf and sand impacts compared to steel impacts still represented a risk of concussion. This suggests that equestrian helmets standards do not properly account for the loading conditions experienced in equestrian accidents

Effect of impact surface in equestrian falls

34th International Conference on Biomechanics in Sports, Tsukuba, Japan, 18-22 July 2016This study examines the effect of impact surface on head kinematic response and maximum principal strain (MPS) for equestrian falls. A helmeted Hybrid III headform was dropped unrestrained onto three impact surfaces of different stiffness (steel, turf and sand) and three locations. Peak resultant linear acceleration, rotational acceleration and duration of the impact events were measured. A finite element brain model was used to calculate MPS. The results revealed that drops onto steel produced higher peak linear acceleration, rotational acceleration and MPS but lower impact durations than drops to turf and sand. However, despite lower MPS values, turf and sand impacts compared to steel impacts still represented a risk of concussion. This suggests that certification standards for equestrian helmets do not properly account for the loading conditions experienced in equestrian accidents.European Commission Horizon 2020Marie Skiodowska-Curie gran

Interrelationships of Muscular Endurance Among Specific Muscle Groups for Continuous and Intermittent Static Contraction in Men

178 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1979.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

The influence of impact angle on the dynamic response of a Hybrid III headform and brain tissue deformation

ASTM Symposium on the Mechanism of Concussion in Sports, Atlanta, Georgia, USA, 13 November 2012The objective of this study was to investigate the influence of impact angle on the dynamic response of a Hybrid III headform and brain tissue deformation by impacting the front and side of the headform using four angle conditions (0°, at the impact site and 5, 10 and 15° rightward rotations of the headform from 0°) as well as three additional angle conditions of -5, - 10 and -15° (leftward rotations from 0°) at the side location to examine the effects of the neckform. The acceleration-time curves were used as input into a finite element model of the brain where maximum principal strain was calculated. The study found that an impact angle of 15° significantly influencesthe results when measured using linear and rotational acceleration and maximum principal strain. When developing sophisticated impact protocols and undertaking head injury reconstruction research, it is important to be aware of impact angle.Deposited by bulk importkpw11/10/1

Comparison of MADYMO and physical models for brain injury reconstruction

Brain injury is researched using physical, mathematical, anatomical, and computational models. However, there has been little research to quantify the expected differences between these methods of brain injury research. The purpose of this research was to compare the brain deformation responses of identical traumatic brain injury (TBI) reconstructions, which were conducted first with Mathematical Dynamic Models (MADYMO) and then again with a Hybrid III headform. The ensuing finite element modelling was done using the University College Dublin Brain Trauma Model. The brain deformation parameters were analysed in discrete regions of interest which matched the TBI lesion as identified on computed tomography scans of the subject. The results indicated that overall the Hybrid III provided responses which were of considerably larger magnitude than the MADYMO simulation for all metrics analysed. The larger magnitude responses are likely a product of the more rigid nature of the Hybrid III in comparison to the MADYMO simulations. Interestingly, when the results are compared to the literature, the Hybrid III results match well with mild traumatic brain injury (mTBI) and TBI research, while the MADYMO simulations produce what would be considered very low local brain deformation responses for TBI lesions.Deposited by bulk impor

Measuring the Influence of Neck Compliance on Brain Tissue Strain

The aim of this study was to determine if a change in neckform compliance could influence maximum principal strain in the brain white and grey matter, the brain stem and the cerebellum. This was done by impacting a Hybrid III headform with a 16.6 kg impactor arm at 5 m/s. Three different Hybrid III neckforms were used: 1) one 50th percentile male neckform - standard neckform; 2) one 50th percentile male neckform plus 30 per cent compliance - soft neckform; 3) one 50th percentile male neckform minus 30 per cent compliance - stiff neckform. The kinematic data obtained was then used to drive a finite element model developed by University College Dublin. The results showed that a decrease in neckform compliance had a significant effect on maximal principal strain in the cerebellum, where the stiff neck (0.050 ± 0.004) generated higher maximum principal strains than the standard neck (0.036 ± 0.003) and the soft neck (0.037 ± 0.001). There were no significant differences between the stiff (0.122 ± 0.013), standard (0.114 ± 0.020) and soft neck (0.119 ± 0.019) in the white matter; the stiff (0.168 ± 0.011), standard (0.176 ± 0.011) and soft neck (0.176 ± 0.007) in the grey matter; or the stiff (0.080 ± 0.003), standard (0.081 ± 0.006) and soft neck (0.085 ± 0.009) in the brain stem. The results were not linked to brain injury due to the absence of a commonly accepted threshold.Deposited by bulk impor

Assessing women\u27s lacrosse head impacts using finite element modelling

Recently studies have assessed the ability of helmets to reduce peak linear and rotational acceleration for women\u27s lacrosse head impacts. However, such measures have had low correlation with injury. Maximum principal strain interprets loading curves which provide better injury prediction than peak linear and rotational acceleration, especially in compliant situations which create low magnitude accelerations but long impact durations. The purpose of this study was to assess head and helmet impacts in women\u27s lacrosse using finite element modelling. Linear and rotational acceleration loading curves from women\u27s lacrosse impacts to a helmeted and an unhelmeted Hybrid III headform were input into the University College Dublin Brain Trauma Model. The finite element model was used to calculate maximum principal strain in the cerebrum. The results demonstrated for unhelmeted impacts, falls and ball impacts produce higher maximum principal strain values than stick and shoulder collisions. The strain values for falls and ball impacts were found to be within the range of concussion and traumatic brain injury. The results also showed that men\u27s lacrosse helmets reduced maximum principal strain for follow-through slashing, falls and ball impacts. These findings are novel and demonstrate that for high risk events, maximum principal strain can be reduced by implementing the use of helmets if the rules of the sport do not effectively manage such situations

Protective capacity of an ice hockey goaltender helmet for three events associated with concussion

The purpose of this study was to assess the protective capacity of an ice hockey goaltender helmet for three concussive impact events. A helmeted and unhelmeted headform was used to test three common impact events in ice hockey (fall, puck impacts and shoulder collisions). Peak linear acceleration, rotational acceleration and rotational velocity as well as maximum principal strain and von Mises stress were measured for each impact condition. The results demonstrated the tested ice hockey goaltender helmet was well designed to manage fall and puck impacts but does not consistently protect against shoulder collisions and an opportunity may exist to improve helmet designs to better protect goaltenders from shoulder collisions.European Commission Horizon 2020Ontario Graduate Scholarship in Science and Technolog

Assessing women's lacrosse head impacts using finite element modelling

Recently studies have assessed the ability of helmets to reduce peak linear and rotational acceleration for women's lacrosse head impacts. However, such measures have had low correlation with injury. Maximum principal strain interprets loading curves which provide better injury prediction than peak linear and rotational acceleration, especially in compliant situations which create low magnitude accelerations but long impact durations. The purpose of this study was to assess head and helmet impacts in women's lacrosse using finite element modelling. Linear and rotational acceleration loading curves from women's lacrosse impacts to a helmeted and an unhelmeted Hybrid III headform were input into the University College Dublin Brain Trauma Model. The finite element model was used to calculate maximum principal strain in the cerebrum. The results demonstrated for unhelmeted impacts, falls and ball impacts produce higher maximum principal strain values than stick and shoulder collisions. The strain values for falls and ball impacts were found to be within the range of concussion and traumatic brain injury. The results also showed that men's lacrosse helmets reduced maximum principal strain for follow-through slashing, falls and ball impacts. These findings are novel and demonstrate that for high risk events, maximum principal strain can be reduced by implementing the use of helmets if the rules of the sport do not effectively manage such situations