Jacob J. Sosnoff

Head Impacts During High School Football: A Biomechanical Assessment

CONTEXT Little is known about the impact biomechanics sustained by players during interscholastic football. OBJECTIVE To characterize the location and magnitude of impacts sustained by players during an interscholastic football season. DESIGN Observational design. SETTING On the field. PATIENTS OR OTHER PARTICIPANTS High school varsity football team (n = 35; age = 16.85 +/- 0.75 years, height = 183.49 +/- 5.31 cm, mass = 89.42 +/- 12.88 kg). MAIN OUTCOME MEASURE(S) Biomechanical variables (linear acceleration, rotational acceleration, jerk, force, impulse, and impact duration) related to head impacts were categorized by session type, player position, and helmet impact location. RESULTS Differences in grouping variables were found for each impact descriptor. Impacts occurred more frequently and with greater intensity during games. Linear acceleration was greatest in defensive linemen and offensive skill players and when the impact occurred at the top of the helmet. The largest rotational acceleration occurred in defensive linemen and with impacts to the front of the helmet. Impacts with the highest-magnitude jerk, force, and impulse and shortest duration occurred in the offensive skill, defensive line, offensive line, and defensive skill players, respectively. Top-of-the-helmet impacts yielded the greatest magnitude for the same variables. CONCLUSIONS We are the first to provide a biomechanical characterization of head impacts in an interscholastic football team across a season of play. The intensity of game play manifested with more frequent and intense impacts. The highest-magnitude variables were distributed across all player groups, but impacts to the top of the helmet yielded the highest values. These high school football athletes appeared to sustain greater accelerations after impact than their older counterparts did. How this finding relates to concussion occurrence has yet to be elucidated.

Biomechanical properties of concussions in high school football

INTRODUCTION Sport concussion represents the majority of brain injuries occurring in the United States with 1.6–3.8 million cases annually. Understanding the biomechanical properties of this injury will support the development of better diagnostics and preventative techniques. METHODS We monitored all football related head impacts in 78 high school athletes (mean age = 16.7 yr) from 2005 to 2008 to better understand the biomechanical characteristics of concussive impacts. RESULTS Using the Head Impact Telemetry System, a total of 54,247 impacts were recorded, and 13 concussive episodes were captured for analysis. A classification and regression tree analysis of impacts indicated that rotational acceleration (95582.3 rad·s−²), linear acceleration (996.1g), and impact location (front, top, and back) yielded the highest predictive value of concussion. CONCLUSIONS These threshold values are nearly identical with those reported at the collegiate and professional level. If the Head Impact Telemetry System were implemented for medical use, sideline personnel can expect to diagnose one of every five athletes with a concussion when the impact exceeds these tolerance levels. Why all athletes did not sustain a concussion when the impacts generated variables in excess of our threshold criteria is not entirely clear, although individual differences between participants may play a role. A similar threshold to concussion in adolescent athletes compared with their collegiate and professional counterparts suggests an equal concussion risk at all levels of play.

Mobility, Balance and Falls in Persons with Multiple Sclerosis

Background There is a lack of information concerning the relation between objective measures of gait and balance and fall history in persons with MS (PwMS). This investigation assessed the relation between demographic, clinical, mobility and balance metrics and falls history in persons with multiple sclerosis (MS). Methods 52 ambulatory persons with MS (PwMS) participated in the investigation. All persons provided demographic information including fall history over the last 12 months. Disease status was assessed with Expanded Disability Status Scale (EDSS). Walking speed, coordination, endurance and postural control were quantified with a multidimensional mobility battery. Results Over 51% of the participants fell in the previous year with 79% of these people being suffering recurrent falls. Overall, fallers were older, had a greater prevalence of assistive devices use, worse disability, decreased walking endurance, and greater postural sway velocity with eyes closed compared to non-fallers. Additionally, fallers had greater impairment in cerebellar, sensory, pyramidal, and bladder/bowel subscales of the EDSS. Conclusions The current observations suggest that PwMS who are older, more disabled, utilize an assistive device, have decreased walking coordination and endurance and have diminished balance have fallen in the previous year. This suggests that individuals who meet these criteria need to be carefully monitored for future falls. Future research is needed to determine a prospective model of falls specific to PwMS. Additionally, the utility of interventions aimed at reducing falls and fall risk in PwMS needs to be established.

Quantifying gait abnormalities in persons with multiple sclerosis with minimal disability

Abnormalities in gait kinematics in persons with multiple sclerosis (PwMS) who have mild disability have been noted using motion capture systems. However, it is not clear if these abnormalities can be detected with clinically feasible technology. This investigation examined if the spatiotemporal markers of gait including variability metrics can distinguish between PwMS with minimal disability and controls with clinically feasible technology. 43 PwMS with minimal disability and 43 healthy controls completed four walking trials along a 26 foot long pressure sensitive pathway (GAITRite). Spatiotemporal markers of gait including variability metrics were determined. Statistical analysis revealed that PwMS walked slower, with fewer, shorter, wider steps and spent a greater percentage of a gait cycle in double support than controls. Additionally, PwMS had greater variability in the time between steps, single support percent and step width than controls. Collectively, the results highlight that PwMS, in the absence of clinical gait impairment, have subtle but detectable differences in gait and that these alterations can be detected with clinically feasible technology. The current results raise the possibility of targeting walking deviations earlier in disability progression in PwMS.

Are age-related increases in force variability due to decrements in strength?

The purpose of this investigation was to examine the relationship between strength and the magnitude and time sequential structure of force variability. Young and old adults produced isometric force via index finger abduction to a visually presented target corresponding to a constant force level of 5 or 25% maximal voluntary contraction (MVC). Cluster analysis was used to divide subjects into groups based on age and strength. The variability of older adults was greater and showed more time dependent structure than their younger counterparts. The force output of weaker subjects was also more variable and had a stronger sequential structure. Indeed, when MVC was controlled for there was no significant age effect on force variability. The relationship between strength and variability remained significant, however, when chronological age was controlled for. The findings revealed that the established age-related changes in force variability are more fundamentally due to the association between strength and force variability and provide a further challenge to using chronological age as a marker of the biological aging process in studies of motor control.

The chronic effects of concussion on gait

OBJECTIVE To examine the effects of concussion on gait patterns of young adults with and without a history of concussion during single- and dual-task paradigms. DESIGN Cross-sectional evaluation. SETTING A research laboratory. PARTICIPANTS Persons with (n=28; mean, 6.32y postinjury) and without (n=40) a concussion history. INTERVENTION Not applicable. MAIN OUTCOME MEASURES A battery of gait analyses during single- and dual-task conditions. Normalized velocity, step length, stride width, number correct from cognitive task, time in single-leg stance, and time in double-leg stance were the variables of interest. Gait was analyzed using an electronic walkway system, and the Brooks visuospatial cognitive task was used to index cognition. RESULTS Data analyses using multiple 2-way repeated-measures analyses of variance and correlations indicated that participants with a history of concussion spent significantly more time in a double-leg stance and significantly decreased time in a single-leg stance and had slower gait velocity. There also was a significant negative correlation between number of concussions and time in single-leg stance and positive correlations between number of concussions and time in double-leg stance and double-stance percent. CONCLUSION These findings suggest that persons with a history of concussion adopt a more conservative gait strategy.

Multiple Sclerosis and Postural Control: The Role of Spasticity

UNLABELLED Sosnoff JJ, Shin S, Motl RW. Multiple sclerosis and postural control: the role of spasticity. OBJECTIVES To examine the association between spasticity and postural control in subjects with multiple sclerosis (MS). DESIGN Cross-sectional. SETTING Motor control laboratory. PARTICIPANTS Subjects with MS (n=16, 2 male) and age and sex-matched subjects (n=16) participated in the investigation. All subjects with MS had Expanded Disability Status Scale scores between 0 and 4.5 and modified Ashworth scale scores between 1 and 3. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Postural control was measured with a force platform that quantifies ground reaction forces and moments in mediolateral and anteroposterior directions. Postural control was indexed with anterior-posterior sway range, medial-lateral sway range, 95% elliptical area of the deviations of center of pressure (COP), velocity of COP sway, and the frequency at which 95% of spectral profile was contained. Participants with MS further underwent assessment of the soleus Hoffman reflex (H-reflex) as an index of spasticity. RESULTS Cluster analysis on H-reflex data identified groups of MS participants with high spasticity (n=7) and low spasticity (n=9). There were no differences in age, duration of MS, and disease severity between MS groups. There were no differences in anterior-posterior sway range between any of the groups. The high spasticity group had greater COP area, velocity, and mediolateral sway compared with the low spasticity and control group, and the low spasticity group had postural control values between the high spasticity and control groups. CONCLUSIONS The pattern of results suggests that spasticity contributes to postural deficits observed in MS.

Previous mild traumatic brain injury and postural-control dynamics

CONTEXT Postural control and cognitive function are adversely affected by acute mild traumatic brain injury (mTBI). Whether postural-control deficits persist beyond the acute stage in individuals with a history of mTBI is unclear. OBJECTIVE To determine if postural-control deficits persist in individuals with a history of mTBI. DESIGN Retrospective cross-sectional study. SETTING University research laboratory. PATIENTS OR OTHER PARTICIPANTS As part of an ongoing investigation examining cognitive and motor deficits associated with mTBI, 224 individuals participated in the study. Of these, 62 participants self-reported at least 1 previous physician-diagnosed mTBI. INTERVENTION(S) Postural control was assessed using the NeuroCom Sensory Organization Test (SOT) postural-assessment battery. MAIN OUTCOME MEASURE(S) The SOT postural assessment yields 4 indices of postural control: a composite balance score, a visual ratio score, a somatosensory score, and a vestibular score. Postural dynamics were also examined by calculating approximate entropy of center-of-pressure excursions in the anteroposterior and mediolateral axis for each test condition. RESULTS Minimal differences in the SOT indices were noted among individuals with and without a history of previous mTBI (P > .05). In the group with a history of mTBI, anteroposterior postural irregularity decreased as postural difficulty increased. In contrast, the group without a history of mTBI displayed increased postural irregularity in the mediolateral direction. CONCLUSIONS Individuals with a history of mTBI exhibited altered postural dynamics compared with individuals without a history of mTBI. These findings support the notion that changes in cerebral functioning that affect postural control may persist long after acute injury resolution.

Influence of spasticity on mobility and balance in persons with multiple sclerosis.

Background and Purpose: Spasticity is a motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes that presumably affects mobility and balance. This investigation examined the hypothesis that persons with multiple sclerosis (MS) who have spasticity of the lower legs would have more impairment of mobility and balance compared to those without spasticity. Methods: Participants were 34 ambulatory persons with a definite diagnosis of MS. The expanded disability status scale (EDSS) was used to characterize disability in the study sample. All participants underwent measurements of spasticity in the gastroc-soleus muscles of both legs (modified Ashworth scale), walking speed (timed 25-foot walk), mobility (Timed Up and Go), walking endurance (6-minute walk test), self-reported impact of MS on walking ability (Multiple Sclerosis Walking Scale-12), and balance (Berg Balance Test and Activities-specific Balance Confidence Scale). Results: Fifteen participants had spasticity of the gastroc-soleus muscles based on modified Ashworth scale scores. The spasticity group had lower median EDSS scores indicating greater disability (P=0.03). Mobility and balance were significantly more impaired in the group with spasticity compared to the group without spasticity: timed 25-foot walk (P = 0.02, d = −0.74), Timed Up and Go (P = 0.01, d = −0.84), 6-minute walk test (P < 0.01, d = 1.03), Multiple Sclerosis Walking Scale-12 (P = 0.04, d = −0.76), Berg Balance Test (P = 0.02, d = −0.84) and Activities-specific Balance Confidence Scale (P = 0.04, d = −0.59). Discussion and Conclusion: Spasticity in the gastroc-soleus muscles appears to have negative effect on mobility and balance in persons with MS. The relationship between spasticity and disability in persons with MS requires further exploration.

The relationship of athlete-reported concussion symptoms and objective measures of neurocognitive function and postural control.

Objective:Concussed athlete evaluations often include symptoms, balance, and neurocognitive assessments. We sought to identify the relationship between subjective symptom reports and objective clinical measures. Design:A retrospective assessment. Setting:A research laboratory. Patients:Concussed collegiate-level athletes (N = 32, 19.7 years) evaluated pre- and postinjury (less than 48 hours). Intervention:Each athlete completed an inventory of concussion-related symptoms, the NeuroCom Sensory Organization Test (SOT), and ImPACT neurocognitive assessment. Spearman correlations between balance symptoms and SOT scores and cognitive symptoms and ImPACT scores were completed. Main Outcome Measures:Symptoms related to balance and cognitive deficits, SOT composite balance and visual, vestibular, and somatosensory ratios, and ImPACT output scores. Results:Significant Spearman correlations were noted between reports of “dizziness” and the SOT composite balance (rs = -0.55) and vestibular ratio (rs = -0.50). Similarly, “balance problems” were significantly correlated with composite balance (rs = -0.52) and the somatosensory (rs = -0.41), visual (rs = -0.39), and vestibular ratios (rs = -0.57). The cognitive symptom of “feeling mentally foggy” and ImPACT variables of reaction time (rs = 0.36) and “difficulty concentrating” and verbal memory score (rs = -0.41) were significantly related. Finally, reports of “difficultly remembering” were significantly related to the verbal memory score (rs = -0.48) and reaction time (rs = 0.36). Conclusions:These findings indicate self-report symptoms are associated with athlete deficits in postural control and cognitive function. The moderate relationship between the symptom reports and the objective measures warrants the continued use of all measures. A reduction in the number of symptoms concussed athletes respond to may be justified to reduce redundancy.