The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

QUITE apart from the academic consideration that vital and medical statistics now form an obligatory part of the education of students seeking the University of London's diploma in public health, the demand for information about the methods of vital and medical statistics is increasing. The most casual reader of the newspapers is now aware that population problems are of serious practical importance and that the publications of the General Register Office cannot be ignored. It is scarcely an exaggeration to say that the recently issued preliminary report on the census of 1931 is one of the most sensational documents which has appeared for years, and that he who reads it intelligently will understand what is meant by saying that civilisation is in the melting pot. An Introduction to Medical Statistics. By Hilda M. Woods William T. Russell. Pp. x + 125. (London: P. S. King and Son, Ltd., 1931.) 7s. 6d.

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An Introduction to Medical Statistics

Purpose of the statement ▸ To provide an evidence-based, best practises summary to assist physicians with the evaluation and management of sports concussion. ▸ To establish the level of evidence, knowledge gaps and areas requiring additional research. Importance of an AMSSM statement ▸ Sports medicine physicians are frequently involved in the care of patients with sports concussion. ▸ Sports medicine physicians are specifically trained to provide care along the continuum of sports concussion from the acute injury to return-to-play (RTP) decisions. ▸ The care of athletes with sports concussion is ideally performed by healthcare professionals with specific training and experience in the assessment and management of concussion. Competence should be determined by training and experience, not dictated by

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American Medical Society for Sports Medicine position statement: concussion in sport

A controlled cortical impact model of traumatic brain injury in the rat.

Objective Cerebral concussion is common in collision sports such as football, yet the chronic neurological effects of recurrent concussion are not well understood. The purpose of our study was to investigate the association between previous head injury and the likelihood of developing mild cognitive impairment (MCI) and Alzheimer's disease in a unique group of retired professional football players with previous head injury exposure. Methods A general health questionnaire was completed by 2552 retired professional football players with an average age of 53.8 (+/-13.4) years and an average professional football playing career of 6.6 (+/- 3.6) years. A second questionnaire focusing on memory and issues related to MCI was then completed by a subset of 758 retired professional football players (> or = 50 yr of age). Results on MCI were then cross-tabulated with results from the original health questionnaire for this subset of older retirees. Results Of the former players, 61% sustained at least one concussion during their professional football career, and 24% sustained three or more concussions. Statistical analysis of the data identified an association between recurrent concussion and clinically diagnosed MCI (chi = 7.82, df = 2, P = 0.02) and self-reported significant memory impairments (chi = 19.75, df = 2, P = 0.001). Retired players with three or more reported concussions had a fivefold prevalence of MCI diagnosis and a threefold prevalence of reported significant memory problems compared with retirees without a history of concussion. Although there was not an association between recurrent concussion and Alzheimer's disease, we observed an earlier onset of Alzheimer's disease in the retirees than in the general American male population. Conclusion Our findings suggest that the onset of dementia-related syndromes may be initiated by repetitive cerebral concussions in professional football players.

Association between Recurrent Concussion and Late-Life Cognitive Impairment in Retired Professional Football Players

Objective Concussion in professional football was studied with respect to impact types and injury biomechanics. A combination of video surveillance and laboratory reconstruction of game impacts was used to evaluate concussion biomechanics. Methods Between 1996 and 2001, videotapes of concussions and significant head impacts were collected from National Football League games. There were clear views of the direction and location of the helmet impact for 182 cases. In 31 cases, the speed of impact could be determined with analysis of multiple videos. Those cases were reconstructed in laboratory tests using helmeted Hybrid III dummies and the same impact velocity, direction, and head kinematics as in the game. Translational and rotational accelerations were measured, to define concussion biomechanics. Several studies were performed to ensure the accuracy and reproducibility of the video analysis and laboratory methods used. Results Concussed players experienced head impacts of 9.3 +/- 1.9 m/s (20.8 +/- 4.2 miles/h). There was a rapid change in head velocity of 7.2 +/- 1.8 m/s (16.1 +/- 4.0 miles/h), which was significantly greater than that for uninjured struck players (5.0 +/- 1.1 m/s, 11.2 +/- 2.5 miles/h; t = 2.9, P Conclusion Concussion occurs with considerable head impact velocity and velocity changes in professional football. Current National Operating Committee on Standards for Athletic Equipment standards primarily address impacts to the periphery and crown of the helmet, whereas players are experiencing injuries in impacts to the facemask, side, and back of the helmet. New tests are needed to assess the performance of helmets in reducing concussion risks involving high-velocity and long-duration injury biomechanics.

Concussion in Professional Football: Reconstruction of Game Impacts and Injuries

Currently, angular acceleration is believed to be more damaging to the brain than linear acceleration, even though both are present in any head impact. In a recent experiment, it was found that a helmeted head sustained the same degree of angular acceleration as the unhelmeted head for the same impact, but its linear acceleration was decreased significantly. So, if angular acceleration is the cause of brain injury, then how is the brain protected by the helmet? This paper proposes a new hypothesis of brain injury and suggests that input acceleration limits should be replaced by response variables.

Is head injury caused by linear or angular acceleration

OBJECTIVE: National Football League game video was analyzed for the typical locations of severe helmet impacts in professional football By use of selected cases that were reconstructed in laboratory tests and reported previously, the magnitude and direction of force causing concussion was determined for these locations METHODS: Multiple video views were obtained for 182 severe helmet impacts that occurred between 1996 and 2001 From a top view, the helmet was divided into 45-degree quadrants with 0 degrees eyes forward From a side view, it was divided into seven equal levels, four (+Q1 to +Q4) above the head center of gravity and three below (-Q1 to -Q3) The initial helmet contact was located in these regions Thirty-one impacts were reconstructed with helmeted Hybrid III dummies involving 25 concussions Measurement of head translational and rotational acceleration was used to determine the average and +/-1 standard deviation in responses, with impacts reflected to the right side RESULTS: From video, the majority (71%) of impact is to the helmet shell primarily from a striking player's helmet, arm, or shoulder pad to the side (45-135 degrees) or from ground contact to the back (135-180 degrees) Most impacts were high on the helmet at +Q2 to +Q4 The remainder (29%) were primarily from helmet contact on the facemask at an oblique frontal angle (0-45 degrees) and -Q3 to +Q1 height From reconstructions, concussion occurred with the lowest peak head acceleration in facemask impacts at 78 +/- 18 g versus an average 107 to 117 g for impacts on other quadrants (t = 290, P

Concussion in professional football: location and direction of helmet impacts-Part 2.

Objective: The biomechanics of the head for punches to the jaw and the risk of head injury from translational and rotational acceleration were studied. Methods: Seven Olympic boxers from five weight classes delivered 18 straight punches to the frangible face of the Hybrid III dummy. Translational and rotational head acceleration, neck responses, and jaw pressure distribution were measured. High speed video recorded each blow and was used to determine punch velocity. Equilibrium was used to determine punch force, energy transfer, and power. Results: Punch force averaged 3427 (standard deviation (SD) 811) N, hand velocity 9.14 (SD 2.06) m/s, and effective punch mass 2.9 (SD 2.0) kg. Punch force was higher for the heavier weight classes, due primarily to a higher effective mass of the punch. Jaw load was 876 (SD 288) N. The peak translational acceleration was 58 (SD 13) g, rotational acceleration was 6343 (SD 1789) rad/s 2 , and neck shear was 994 (SD 318) N. Conclusions: Olympic boxers deliver straight punches with high impact velocity and energy transfer. The severity of the punch increases with weight class.

https://bjsm.bmj.com/content/bjsports/39/10/710.full.pdf

Biomechanics of the head for Olympic boxer punches to the face

OBJECTIVE: Impacts causing concussion in professional football were simulated in laboratory tests to determine collision mechanics. This study focuses on the biomechanics of concussion in the struck player. METHODS: Twenty-five helmet impacts were reconstructed using Hybrid III dummies. Head impact velocity, direction, and helmet kinematics-matched game video. Translational and rotational accelerations were measured in both players’ heads; 6-axis upper neck responses were measured in all striking and five struck players. Head kinematics and biomechanics were determined for concussed players. Head displacement, rotation, and neck loads were determined because finite element analysis showed maximum strains occurring in the midbrain after the high impact forces. A model was developed of the helmet impact to study the influence of neck strength and other parameters on head responses. RESULTS: The impact response of the concussed player’s head includes peak accelerations of 94 28 g and 6432 1813 r/s 2 , and velocity changes of 7.2 1.8 m/s and 34.8 15.2 r/s. Near the end of impact (10 ms), head movement is only 20.2 6.8 mm and 6.9 2.5 degrees. After impact, there is rapid head displacement involving a fourfold increase to 87.6 21.2 mm and 29.9 9.5 degrees with neck tension and bending at 20 ms. Impacts to the front of the helmet, the source of the majority of National Football League concussions, cause rotation primarily around the z axis (superior-inferior axis) because the force is forward of the neck centerline. This twists the head to the right or left an average of 17.6 12.7 degrees, causing a moment of 17.7 3.3 Nm and neck tension of 1704 432 N at 20 ms. The head injury criterion correlates with concussion risk and is proportional to ∆V 4 /d 1.5 for half-sine acceleration. Stronger necks reduce head acceleration, ∆V, and displacement. Even relatively small reductions in ∆V have a large effect on head injury criterion that may reduce concussion risks because changes in ∆V change head injury criterion through the 4th power. CONCLUSION: This study addresses head responses causing concussion in National Football League players. Although efforts are underway to reduce impact acceleration through helmet padding, further study is needed of head kinematics after impact and their contribution to concussion, including rapid head displacement, z-axis rotation, and neck tension up to the time of maximum strain in the midbrain. Neck strength influences head ∆V and head injury criterion and may help explain different concussion risks in professional and youth athletes, women, and children.

David C. Viano

Papers

Concussion in Professional Football: Reconstruction of Game Impacts and Injuries

Is head injury caused by linear or angular acceleration

Concussion in professional football: location and direction of helmet impacts-Part 2.

Biomechanics of the head for Olympic boxer punches to the face

Concussion in professional football: biomechanics of the struck player—part 14