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No description available.

No description available.

Forces associated with head lifting efforts as well as mouth pressure were measured on four supine normal men, at five different lung volumes from FRC to TLC, and with the head positioned at two different heights above the bed. Positioning the head at one of the two heights (3cm and 10cm) provided for a change in length of the sternocleidomastoid (SCM) muscle. Graded efforts of head lift, and graded inspiratory pressure manoeuvres were executed and corresponding electromyograms of the SCM were measured. The mass lifted during efforts of head lift under static conditions (HSL) was measured with a self-contained transducer system located under the head of the subject. The muscle pressures at different lung volumes were obtained from pressure transducer records by adding the pressure-volume relaxation curve to the inspiratory mouth pressure-volume curve. The electromyogram of the SCM was obtained from surface electrodes, amplified and processed with a smoothing integrator to obtain the mean rectified electromyogram (MRE). For every subject, the relationships between MRE and MASS LIFTED, and between MRE and MUSCLE PRESSURE were linear for every lung volume at every head height above the bed ( r² >0.95 ). Data from all subjects were put together to form a single linear relationship (MRE vs MASS LIFTED and MRE vs MUSCLE PRESSURE) for every head height above the bed. The variability was greater at 3cm than at 10cm of head height. For both the head lift manoeuvre and the respiratory manoeuvre, there was a greater variability due to lung volume, on the slope and intercept of the curves at 3cm, than at 10cm of head height. Furthermore, more EMG was generated at 10 cm than at 3cm for a constant mechanical output, i.e., head lift or muscle pressure. Statistical tests were performed on the curves. Slope and intercept of the curves at different lung volumes, for a specific manoeuvre and head height above the bed were not significantly different ( p<0.05 ). The curves at different lung volumes were then put together to form a single linear relationship for both manoeuvres at both heights. Slope and intercept of the "pooled" curves, at both 3cm and at 10cm, were tested for both head lift and respiratory manoeuvres. It was found that the slopes were significantly different ( p<0.05 ) while the intercepts were net. Using the input variable, MRE, as the common factor, a linear relationship between the two output variables, MASS LIFTED and MUSCLE PRESSURE, was determined at each head height. Interpretation of the resulting relationships shows that: (a) About 50% of the maximum inspiratory muscle pressure can be generated without using the SCM muscle. (b) For the head located at 3cm above the bed, the production of muscle pressure from 50% to 100% Pmusc(max) corresponds to lifting, with the head, a mass equivalent to 4.5 times the head mass, while at 10cm above the bed, the same respiratory manoeuvre corresponds to lifting a mass equal to 1.3 times the head mass. (c) Changes in lung volume do not bring about as great changes in length of the SCM muscle as do changes in head height. / Thesis / Master of Engineering (ME)

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No description available.

No description available.

The purpose of this study was to determine the linear accelerations, angular rates, and angular accelerations of the center of gravity of the head during daily activities and to determine the effect of angular terms on the linear accelerations. A total of 700 experiments were conducted with 18 subjects performing 13 different tasks. Resultant maxima were 93.6 m/s² for linear acceleration, 931.3 rad/s for angular acceleration and 9.03 rad/s for angular rate. Comparisons by gender were statistically significant in 21.9% of cases. Qualitatively, subject effort appeared to be the most important factor. Average error was strongly influenced by the type of motion in each event, ranging from -3.1% to 115.2% when converting from mouthpiece resultant accelerations to center of gravity acceleration. Error increases as angular rates and accelerations increase. Mouthpiece array accelerations are statistically significantly different than center of gravity accelerations in 86.3% of comparisons. Array designs from the literature are significantly different than center of gravity accelerations with equal frequency to the mouthpiece. Peak accelerations from Allen et al 1994 may require correction of up to 2G and 80% to obtain center of gravity accelerations. Angular terms must be accounted for even at daily activity levels. / Master of Science

Sports related concussions result in 300,000 brain injuries in the United States each year. The purpose of this study was to utilize an in-helmet system that measures and records linear head accelerations to analyze head impacts from collegiate football. The Head Impact Telemetry (HIT) System is an in-helmet system with six spring mounted accelerometers and an antenna that transmits data via radio frequency to a sideline receiver and laptop computer system. The data reported by the HIT System includes the time of impact, location of impact, and linear acceleration resultant of the head center of gravity. The algorithm and in-helmet application for this system were validated in five series of tests. In particular, the validation emphasized that the HIT System measurements are of the player's head and not helmet accelerations as evidenced by the helmet acceleration being 16.6 (± 3.2) times greater than the peak head accelerations measured by the HIT System and dummy cg accelerometers. Using 130 head impacts in five different test configurations, the mean error in measuring peak linear acceleration was 0.01% (±18%). A total of 11,604 head impacts were recorded from the Virginia Tech football team throughout the 2003 and 2004 football seasons during 22 games and 62 practices from a total of 52 players. The acceleration data distribution was right skewed with a mean impact acceleration magnitude of 20.9 g and maximum value of 172.6 g. The HIC determined for each impact from a 15 millisecond time period was similarly distributed with the mean equal to 17.9, and the maximum equal to 969.6. A total of three impacts with three different players resulted in concussions. These impacts had peak linear accelerations of 55.7 g, 136.7 g, and 117.6 g with HIC values of 120.6, 518.4, and 355.6 respectively. Each of these hits was among the highest recorded for each respective player. Although the incidence of injury data is limited, this study presents an extremely large data set from human head impacts that provides valuable insight into the lower bounds of mild traumatic brain injuries. / Master of Science

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