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

PROPRIOCEPTION OF ANKLE JOINT IN YOUNG HOCKEY PLAYERS

Postural control stability is significantly affected by proprioception in the lower limb. Moreover, the lack of proprioceptive feedback that results from injuries, such as ankle injury, may allow the excessive or inappropriate loading of a joint4, and is one of the factors that leads to progressive degeneration of the joint and continued deficits in joint dynamics, balance, and coordination. Much clinical research has demonstrated that individuals with proprioception and neuromuscular response deficits as a result of injury, lesions, and joint degeneration are less capable of maintaining postural stability and equilibrium. However, no normal reference data on ankle proprioception represented by kinesthesia in healthy young people are available. And if some exercise, such as hockey /skating exerts effects on ankle proprioception is unclear. The objectives of the study were to study the ankle kinesthesia in plantarflexion-dorsiflexion and inversion-eversion movements in healthy young people and young hockey players so as to get a preliminary understanding to the ankle proprioception of healthy young people and to examine the effects of hockey exercise on ankle proprioception

IMPACT FREQUENCY VALIDATION OF HEAD IMPACT SENSOR TECHNOLOGY FOR USE IN SPORT

Head impact frequency has been identified as a contributing factor to long-term trauma experienced by the brain. A peak linear acceleration greater than 20g has been proposed as defining a single impact. The purpose of this study was to examine the accuracy of a single head impact sensor to identify 209 impacts under short

MEASUREMENT ACCURACY OF HEAD IMPACT MONITORING SENSOR IN SPORT

Head injury and brain trauma exposure in sport have been recognized as potential contributors to long-term neurological disorders. As a result sensors have been proposed as an impact severity monitoring tool for on-field measurement of head accelerations. The purpose of this study was to characterize the accuracy of a head impact monitoring sensor system. Peak acceleration responses from a Smart lmpact Monitor (SIM) sensor were compared against reference sensors from a Hodgson-WSU headform. The headform with SIM was impacted for 7 impact conditions and 3 inbound energies. Moderate to strong positive correlations were found between the SIM and reference sensors for all impact conditions. At higher inbound energy the SIM overestimated, suggesting that under higher risk conditions the SIM represents a conservative tool in identifying dangerous impacts

CORRELATIONS BETWEEN HEAD ROTATIONAL KINEMATICS AND BRAIN TISSUE STRAIN FOR LOW AND HIGH LEVEL FOOTBALL HELMET IMPACTS

This study examined the correlation between head angular velocity and acceleration with brain strain for low and high level impacts. Impacts at 2.4m/s (low) and 11m/s (high) were delivered to a American football helmeted Hybrid III headform using a centric/non-centric protocol. A finite element model calculated strain from headform accelerations. The lowlevel impact data were obtained from a previous subset eliciting angular responses occurring at 20g, therefore linear acceleration relationships were not examined. High correlations (r=>0.8) existed for non-centric conditions between strain with angular acceleration and velocity, while centric conditions had moderate relationships (r=0.50.68). This research demonstrates that kinematic-strain relationships are dependent on the impact event, and that a single variable may not represent strain under all conditi

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

A comparison in a youth population between those with and without a history of concussion using biomechanical reconstruction

OBJECTIVE: Concussion is a common topic of research as a result of the short- and long-term effects it can have on the affected individual. Of particular interest is whether previous concussions can lead to a biomechanical susceptibility, or vulnerability, to incurring further head injuries, particularly for youth populations. The purpose of this research was to compare the impact biomechanics of a concussive event in terms of acceleration and brain strains of 2 groups of youths: those who had incurred a previous concussion and those who had not. It was hypothesized that the youths with a history of concussion would have lower-magnitude biomechanical impact measures than those who had never suffered a previous concussion. METHODS: Youths who had suffered a concussion were recruited from emergency departments across Canada. This pool of patients was then separated into 2 categories based on their history of concussion: those who had incurred 1 or more previous concussions, and those who had never suffered a concussion. The impact event that resulted in the brain injury was reconstructed biomechanically using computational, physical, and finite element modeling techniques. The output of the events was measured in biomechanical parameters such as energy, force, acceleration, and brain tissue strain to determine if those patients who had a previous concussion sustained a brain injury at lower magnitudes than those who had no previously reported concussion. RESULTS: The results demonstrated that there was no biomechanical variable that could distinguish between the concussion groups with a history of concussion versus no history of concussion. CONCLUSIONS: The results suggest that there is no measureable biomechanical vulnerability to head impact related to a history of concussions in this youth population. This may be a reflection of the long time between the previous concussion and the one reconstructed in the laboratory, where such a long period has been associated with recovery from injury

Proceedings from the Ice Hockey Summit III: Action on Concussion

The Ice Hockey Summit III provided updated scientific evidence on concussions in hockey to inform these five objectives: 1) describe sport-related concussion (SRC) epidemiology, 2) classify prevention strategies, 3) define objective, diagnostic tests, 4) identify treatment, and 5) integrate science and clinical care into prioritized action plans and policy. Our action plan evolved from 40 scientific presentations. The 155 attendees (physicians, athletic trainers, physical therapists, nurses, neuropsychologists, scientists, engineers, coaches, and officials) voted to prioritize these action items in the final Summit session. 1) Establish a national and international hockey data base for SRC at all levels, 2) eliminate body checking in Bantam youth hockey games, 3) expand a behavior modification program (Fair Play) to all youth hockey levels, 4) enforce game ejection penalties for fighting in Junior A and professional hockey leagues, 5) establish objective tests to diagnose concussion at point of care (POC), and 6) mandate baseline testing to improve concussion diagnosis for all age groups. Expedient implementation of the Summit III prioritized action items is necessary to reduce the risk, severity, and consequences of concussion in the sport of ice hockey