Quantitative electromyography: response of the neck muscles to conventional helmet loading

Experiments were conducted to quantify the fatigue of neck muscles which occurs during loading of these muscles by: the head itself (CON), the conventional SPH-4 helmet (HEL), and a combination of the SPH-4 helmet with Night Vision Goggles (H/NVG). Two exercise periods of 5 min and 35 min duration, respectively, were performed by the 5 subjects, during which a subject would rotate the head laterally (from side-to-side) in the CON, HEL, or H/NVG configuration. Immediately thereafter, the subject would position his head in an isometric head dynamometer and exert a sustained right lateral (LAT) neck contraction, or forward (FOR) neck contraction at 70% of his maximum strength, during which his endurance time to fatigue was recorded, and the EMG over the right sternocleidomastoid (SCM) muscle, and over the posterior trapezius/splenius muscles was continuously recorded. The root-mean-squared (RMS) amplitude of the electromyogram (EMG) continuously increased during the fatiguing contraction, being 78% greater (on the average) by the time of fatigue, and the center frequency of the EMG power spectrum continuously decreased, being 27% less (on the average) at the fatigue end-point. Some variability with head loading configuration and contraction mode was observed. These results are significant since they demonstrate that the EMG of neck muscles can be used as a noninvasive, objective and quantitative index of the neck muscle fatigue.

Protection of the head and eyes in forestry work

The helmet used in forestry work is the same as that in industrial use. The eye protector, which is usually a face shield made from wire mesh, is fastened to the helmet. The aim of the present study was the clarification of the frequency of use of, the protection afforded by, and the need for improvement in the helmet and eye protector. A questionnaire, an interview, observations, accident and near-accident reports, and user and laboratory tests were used for this purpose. Eighty-eight percent of loggers always use a helmet, and 32% an eye protector. According to official statistics and the questionnaire, in 1980, 8 to 15 of every 100 accidents in logging injured the head or eyes. Loggers reported that the helmet was too hot in summer and too cold in winter. The low utilization rate for eye protectors is partly explained by design defects. The protectors become frosted in the winter; there is poor visibility through the protectors when it rains or is dark; the protectors cause glare in sunshine. Product development seems to be necessary so that the helmet and eye protector can better fulfill the special requirements of forestry work.

[Head injuries in childhood caused by skiing and their optimal prevention]

During the last three skiing seasons we have treated a total of 105 children in our clinical wards for skull-brain injuries caused by skiing accidents. 25 of these cases (25.2%) were operated on, mostly because of a depressed fracture (92%) with or without brain lesion/bleeding, which the children incurred by colliding with various obstacles. Uncontrolled excessive speed and careless skiing methods are the main reasons for these injuries. However, the responsibility for the increasing number of skisport-connected skull-brain injuries does not lie with the children alone, but more so with us grown-ups, i.e. the parents, teachers and physicians, as long as we do not preach and emphatically insist on the implementation of indirect and direct specific measures of accident prevention. Based on an analysis of typical injuries and their many causes we come to the conclusion that, aside from the usual precautions, only one simple, sensible and effective prevention of skull-brain injuries is feasible, namely the "protection helmet". Similar to the existing crash-helmet law for motorcylists and just like for the professional skiracers, whom the children try to imitate more and more with regard to style and speed, we earnestly urge legislation to make the wearing of a protective helmet compulsory for all skiers up to 17 years of age.

Estimating proportionate changes in rates

Quantitative measures are defined for use in health policy formulation. Consider a dichotomized risk factor for a specific disease or a protective factor known to promote health. A health policy that alters the prevalence of exposure to the factor will create corresponding proportionate changes in the disease rate and in the health rate. Statistical formulas are presented for estimating such proportionate changes. Formulas are given for cohort, case-control, and some hybrid study designs, but only for those studies where it is appropriate to present the data in a 2 X 2 table. It is assumed that the population is stable and that all subjects are observed over the same fixed time interval. Formulas for estimating the standard error of the estimate are also provided.

The economics of safety deregulation: lives and dollars lost due to repeal of motorcycle helmet laws

Between 1976 and 1980, 28 state legislatures in the United States repealed or weakened their motorcycle helmet-use laws. This paper estimates the number of excess deaths attributable to this deregulatory activity, and the associated economic costs to society. Because of data limitations, no attempt was made to estimate the excess nonfatal injuries and associated costs. We applied a variant of log-linear contingency-table analysis to the monthly counts of motorcycle fatalities in the 48 contiguous states over the period 1975 through 1980. This analysis produced estimates of the total number of deaths, in each of 36 age-sex groups, that could be attributed to changes in the helmet laws. We then estimated the direct and indirect economic costs associated with fatalities in each age-sex group. Our findings indicate that 516 excess deaths occurred in 1980 in the 28 states that weakened or repealed their helmet laws. This represented 24 percent of the total motorcycle fatalities occurring in those states. Women and younger cyclists of both sexes comprised a disproportionate share of excess deaths. The economic costs to society that are associated with the excess fatalities resulting from the repeals of helmet laws total at least $180 million.

Motorcycle-related trauma and helmet usage in North Dakota

A descriptive epidemiologic study utilizing a multi-disciplinary reporting format was undertaken to assess the impact of helmet usage on motorcycle trauma in North Dakota from 1977 through 1980. This approach yielded an 82.6% reporting increase compared to previous data collection techniques. More than 60% of the 2,934 crashes involved unhelmeted cyclists. Two-thirds of all crashes resulted in injury, with head, neck, and face (HNF) trauma accounting for 21.4% of all lesions. Compared to their helmeted counterparts, helmetless riders suffered HNF trauma 2.30 times as often, and were 3.19 times as susceptible to fatal injuries. the number of injuries and the severity of trauma were significantly higher (P = .01) for those individuals not wearing helmets. A substantial decline in usage occurred in those under 18 years of age, despite the legal requirement that this group wear protective headgear.

[Safety criteria in the problem of protection for the pilot's head against impact]

In order to determine man's tolerance, clinical symptoms of craniocerebral injuries were compared with physical characteristics of impacts. A ranking scheme of clinical manifestations of craniocerebral injuries as applied to specific flight conditions was developed. With respect to the craniocerebral injury biomechanics, clinical data were taken under statistical study, which helped to evaluate impact critical parameters and to propose a graphic scheme that can be used to describe in detail the accident and to estimate the probability of injuries of various degree over the entire range encountered in aviation and clinical practice.

Head and facial injuries after low-speed motor-cycle accidents

In the United Kingdom there appears to be little available information concerning the prevalence and the patterns of head and of facial injuries sustained in road traffic accidents by motorcyclists wearing protective helmets. The present preliminary survey was of 56 accidents in urban traffic. 50 per cent of surviving motor-cyclists incurred head injuries. Soft tissue facial wounds were sustained by 38 per cent and fractures of facial bone and teeth by 11 per cent of the injured. The majority of the accidents occurred at speeds of 30 m.p.h. or less to riders of machines of small cubic capacity. Motor-cyclists wearing open-face style helmets had more facial damage after accidents than those wearing full-face style helmets. The results of the survey suggest the need for research into the degree of protection against head and facial injuries offered by the various helmet styles and their constituent materials.

Differences in head injuries of pedal cyclist and motorcyclist casualties in Victoria

There being no legal requirement in Victoria for pedal cyclists to wear crash helmets (and only few do so), we tested the hypothesis that pedal cyclists are subject to significantly greater risk of head injury than motorcyclists, who are required by law to wear them. Injury data of 1975 to 1980 showed that there were three times more fatalities and reported non-fatal casualities among motorcyclists than among pedal cyclists. Head injuries, including fractured vault of skull, fractured base of skull, concussion and intracranial injury, were significantly more frequent among pedal cyclist casualties (P less than 0.001). The number of pedal cyclist casualties with solely head injury was twice that of motorcycle riders, and those pedal cyclist casualties had a significantly greater incidence of fractured vault of the skull. It is likely that risk of head injury for pedal cyclists would be significantly reduced if they wore protective helmets.

Rebreathing in a subject wearing an integral crash helmet

The respired air of a volunteer was analysed while he was wearing a variety of integral crash helmets. Observations were made with and without a protective balaclava, bib or scarf, or both. Rebreathing occurred and the peak inspired oxygen tension fell as low as 16.0 kPa (120 mm Hg) with a minimum inspired carbon dioxide of 2.1 KPa (16.0 mm Hg). Accessories worn or attached to the helmet which restrict airflow into the helmet should not be used. Attention should be paid to the "air conditioning" of helmets when worn with flameproof balaclavas and bibs.

Hearing damage risk to divers operating noisy tools under water

During the measurement of noise generated inside a standard hard hat and the underwater noise level produced by a pneumatic rock drill and two different high-pressure water jet lances commonly used in underwater work, noise levels were recorded of up to 170.5 dB(A), in relation to a pressure of 1 muPa, in the water close to the diver's heads. Fortunately, the noise is attenuated by the hoods/helmets worn by the divers and the raised hearing threshold in water and compressed gas. The recorded temporary threshold shifts indicate, however, that lengthy exposure might be hazardous to divers' hearing. This possibility is confirmed by a comparison of the noise levels observed in the present study with hearing damage risk criteria.

The role of helmets in reducing head injuries from motorcycle accidents: a political or medical issue?

The cases of 311 motorcycle accident victims who were seen at a major trauma center over 17 months were reviewed. The types and severity of injuries were standardized according to the Injury Severity Score (ISS) for motor vehicle accidents. Victims were categorized into groups: helmet or no helmet and major, minor or no head injury. Major injury was defined as a 3 on the Abbreviated Injury Scale for "head" (loss of consciousness for at least 15 minutes with or without skull fracture and with or without neurological deficit). THE FOLLOWING CONCLUSIONS ARE DRAWN: (1) The death rate for those with and without helmets was not significantly different, (2) the victims of fatal accidents had identical total ISS scores regardless of the presence of helmets, (3) the chance of sustaining a severe head injury was significantly higher in the no helmet group and (4) the incidence of long-term neurological defect was three times greater in the no helmet group.

Motorcycle fatalities: analysis of Birmingham coroner's records

Analysis of the evidence from 55 coroner's inquests concerning 51 separate motorcycle accidents is reported. Fatal injuries were frequently associated with excessive speed and alcohol consumption. High speed was more common with more powerful machines. Negotiating outside bends seemed particularly hazardous. However, the errors of other road users were the most significant individual cause of fatal accidents. All motorcycle drivers were male, with a peak age group of 17, and most accidents occurred in the summer, frequently in the late evening. Some measures to reduce this mortality are discussed.

Puck impact response of ice hockey face masks

A sample of new ice hockey face masks was struck over the nose or eye of a headform by pucks shot at velocities of 11-39 m/s (25-87 m.p.h.). Deformation of the masks was studied from high speed film. Acceleration pulses transmitted to the center of gravity of the headform were recorded. Peak accelerations never exceeded 86 G's and were well below reported concussion thresholds (200 G's). The film showed contact of the mask or puck with the face at puck velocities of 28 m/s (60 m.p.h.) and above. These results indicate a somewhat lower "safe" puck impact velocity (28 m/s) than that stated by the Canadian Standards Association (32 m/s) under the standard which applied to these masks. Some boys 12 years and older can shoot pucks at 28 m/s (60 m.p.h.). We urge that all manufacturers of sports protective equipment incorporate state of the science, quantitative evaluations of their products, beyond minimum CSA standard testing, in their design programs to improve the quality of information transmitted to the public.

Biomechanics of hyperextension injuries to the cervical spine in football

The biomechanics of cervical spine hyperextension injuries in football players were assessed by using quasi-static-free body analyses. Three situations, i.e., "cases," corresponding to the loading conditions created by three different helmet designs, were examined with the following assumptions: (1) the helmet rim is cut high enough posteriorly so that it does not impinge upon the posterior cervical spine, (2) the helmet rim impacts at the level of the fourth cervical vertebra, and (3) the posterior rim of the helmet strikes the shoulder pads. The results of the analyses suggest that the most dangerous hyperextension situation is Case 1 which leads to high forces and possibly serious injury to the upper cervical spine. The impact of the posterior rim of the helmet at the fourth cervical vertebra (Case 2) significantly reduces these forces. This finding directly conflicts with the so-called "guillotine" mechanism of injury. The impact of the posterior rim of the helmet on the shoulder pads (Case 3) creates the least hazardous loading conditions.

Cineradiographic study of football helmets and the cervical spine

A total of 16 men (4 professional football players, 5 high school athletes, and 7 hospital personnel) was studied by cineradiography to evaluate the possible roles of the posterior rim of the football helmet in causing neck injuries. The men ranged from tall elongated neck individuals to short chunky neck individuals. Moving picture (16-mm) films were produced from a series of lateral view cineradiograms that were taken to document the path and position of the posterior rim of the helmet relative to the spinal column as the subject moved his head from the fully flexed to the fully extended positions under several loading conditions. Five different helmets, all from different companies, were used in the studies. No contact existed at any time between the posterior rim of any of the five helmets worn and the fourth cervical vertebral spinous process; in fact, it did not come close to the spinous process of vertebrae C1 through C6. The notion of the posterior rim of the helmet being capable of striking the cervical spine about the C4 to C5 level is without foundation.

Sports-related eye injury. A preventable problem

Sports-related eye injuries pose a substantial and preventable problem. Ophthalmologists, by educating their patients regarding the risks of eye injuries in various sports and the benefits availability of protective equipment, have the potential to prevent injury to well over 100,000 eyes each year. General guidelines and recommended levels of eye protection for various sports are given. The appendix lists suppliers of protective equipment.

The repeal of helmet use laws and increased motorcyclist mortality in the United States, 1975-1978

Monthly mortality figures for motorcyclists for each state in the United States were obtained for the period January 1975 through December 1978. Twenty-four states revealed or weakened their helmet use laws at various dates within this period. Two of these states subsequently reintroduced a strengthened law. This paper measures the effects of these law changes on motorcyclist mortality. The states that repealed or weakened their helmet laws were matched with one or more states from the same geographic region that either did not have helmet use laws or did not change such existing laws in this four-year period. The effect of weakening the law in each state was then estimated in three steps: 1) the mortality data from each state for the period prior to repeal were regressed on smoothed data from the matched states; 2) these equations were used to predict the numbers of motorcyclist deaths that would have been expected in each state in the period following the repeal or weakening of the law if the laws had not been changed; 3) these numbers of expected deaths were then compared with the actual numbers of deaths that occurred. Of the 26 law changes, it was found that 23 resulted in a greater number of actual deaths in the period following the repeal or weakening of the law than were predicted to occur if the law had not been changed. It is estimated that the repeals or weakening of motorcyclist helmet use laws were typically followed by almost 40 per cent increases in the numbers of fatally injured motorcyclists.