The Effect of Shoe Type on a Golfer's Stability

The role of the shoe in the golf swing should be to provide a solid base of support for the application of forces. Because there is a large mediolateral component to the reaction forces at the feet during the swing, a shoe is required that is effective in providing mediolateral stability. Without the necessary stability, changes in the kinetics and kinematics of the swing may occur that could lead to inaccurate ball placement. To study the role of stability, twelve right-handed male golfers where asked to hit golf balls into an indoor driving net using a five iron golf club. All subjects were experienced golfers with self-reported handicaps of twelve or less. In-shoe pressure measurements using a Tekscan in-shoe pressure measurement system were recorded in each shoe simultaneously at 100 Hz. Ground reaction forces for each foot were collected for the same trials using two separate A.M.T.I. force platform systems sampling at 319 Hz. Identification of address and contact involved the use of a pressure sensor beneath the ball and the hitting surface. A light was iluminated while the golfer was in the address position (AD) as well as at contact (CON). This circuit was also interfaced to a microcomputer via an analog to digital converter so that AD and CON could be identified in the ground reaction force data. These positions were verified and maximum backswing (MB) was identified using a 200 Hz NEC high speed video camera. The shoe types consisted of two golf shoes, one athletic golf shoe, one running shoe, and one cross-training shoe. Analysis focused on changes in the movement of the center of pressure (COP) at the ground-shoe and shoe-foot interface, as well as position of the center of pressure at address, maximum backswing and contact. Comparison of the movement of the COP was used to indicate the relative stability of each shoe. The occurrence of the maximum deviation of the COP in the anteroposterior and medio-Iateral direction relative to MB and CON was assessed both in-shoe and at the ground-shoe interface. The results may provide evidence regarding the stability associated with golf shoes as compared with a cross-trainer or running shoe

Stratospheric aerosol modification by supersonic transport operations with climate implications

The potential effects on stratospheric aerosois of supersonic transport emissions of sulfur dioxide gas and submicron size soot granules are estimated. An interactive particle-gas model of the stratospheric aerosol is used to compute particle changes due to exhaust emissions, and an accurate radiation transport model is used to compute the attendant surface temperature changes. It is shown that a fleet of several hundred supersonic aircraft, operating daily at 20 km, could produce about a 20% increase in the concentration of large particles in the stratosphere. Aerosol increases of this magnitude would reduce the global surface temperature by less than 0.01 K

THE EFFECT OF STEP-HEIGHT ON THE KNEE ANGLES AND IN-SHOE PRESSURE DISTRIBUTIONS DURING STEP-AEROBICS

INTRODUCTION A recent trend in indoor exercise is step-aerobics. This form of aerobic exercise involves the rhythmic stepping up to and down from a fixed platform to the beat of the accompanying "pop" music. In the past, substantial research has been done on the kinematics of the climbing of actual architectural stairs (Andriacchi et al., 1980; McFayden and Winter, 1988; Laubenthal et al., 1972) but no studies, to date, have been done to explore the kinematics of this new fitness phenomenon. Therefore, the purpose of this investigation was to study the biomechanics of step aerobics. Specifically, the effect of the step-height on the knee angles and in-shoe pressure distributions of subjects performing step aerobics was evaluated. It was hoped that the results of this study could be used to help determine any possible biomechanical health concerns of participation in step aerobics

In-Shoe Pressure Distribution During Ergometer Rowing In Novice And Experienced Rowers

Distribution of foot pressure during rowing has been minimally investigated. Foot pressure distribution is most likely altered with experience ca using an increase in stability and thus efficiency duirng the rowing stroke. This study evaluated in-shoe pressure distribution differences between novice and experienced collegiate rowers during rowing on the Concept II ergometer. In shoe pressure was measured in ten subjects, five novice and five experienced, while rowing at a stroke rate of 32-34 strokes per minute. The subjects wore the same model shoe with a Tekscan in-shoe pressure measurement system placed inside each shoe, only the dominant foot was studied. Data were sampled at a rate of 100 Hz. The following variables at the shoe-foot interface were investigated during the drive and the recovery of the stroke: peak forefoot pressure, peak rearfoot pressure, and displacement of the mediolateral and longitudinal center of pressure (COP). Peak pressures were investigated to discover how the pressure is distributed during the stroke. Comparison of the COP was used to indicate the stabililty of the foot during the drive phase. The experienced rowers had a high proportion of the total in-shoe pressure in the forefoot during the drive. Generally there was less pressure exerted on the recovery phase in the experienced subjects. These subjects also had a less variable mediolateral COP and an increase in the longitudinal COP plot. To apply force correctly during the drive it seems to be necessary to place a high proportion of the pressure in the forefoot. The trend toward decreased pressure on the recovery in the experienced rowers may reflect an increased efficiency due to experience. The decrease in the mediolateral COP deviation would appear to be related to increased stability. The longitudinal COP plot showed that with experience the plantar surface in contact with the shoe during the drive increases

A Comparison Of Five Mechanical Work Algorithms For Different Footstrike Patterns And Speeds During Distance Running

The mechanical work done by a runner during an average stride cyde has been calculated with a variety of algorithms that generate values that may vary by an order of magnitude. The application of different algorithms to the same data set is uncommon, and does not seem to have been used at all to compare different foot strike patterns (FSP) during distance running. Average stride cycle values from five work algorithms for forefoot strike (ffs) and heel strike (hs) running at three different running speeds are presented. In general order from most to least restrictive: Wn allows no transfer between segments; Ww, within-segment transfer only; WwbAS, transfer within and between adjacent segments only; WwbLT, within and between segments of the same limb and the trunk; and, Wwb, within- and between-segment transfer with no restrictions. The primary difference in these algorithms is the amount of energy transfer they permit between and among body segments. Twelve highly skilled, male distance runners each ran with both FSP at three speeds ranging from 3.58 to 4.58 m-s-l. High-speed video (200 Hz) was used to track eight segment endpoint markers in the left sagittal plane. An ll-segment model was used with symmetry assumed to generate right side values. Among the algorithms, the no-transfer method (Wn) produced the highest work estimates. An absolute difference of -300 joules-stride-1 (-15-20%) existed across speeds between the no-transfer and within-transfer algorithms. There was then a relatively large decrease to the span of values generated from the other three algorithms. WwbAS was slightly higher than the remaining two algorithms, moreso in relative terms as speed increased. WwbLT increased slightly over speed (-40% slow->fast), while Wwb, the least restrictive, demonstrated almost no change across speeds (-1 % slow->fast). On average, these differences converged absolutely (75->20 joules-stride-1) and relatively (9.8%->2.5%) with increased speed; i.e., differences between the two .FSP decreased as speed increased. At all speeds for each algorithm, hs was lower than ffs. Collapsed across speeds, hs as percentage of ffs was 96.7 (Wn), 96.5 (ww)- 96.7 (WwbAS), 95.8 (WwbLT) and 89.4% (Wwb). Wwb across speeds consistently showed the largest relative differences between FSP, due perhaps in part to low absolute values. However, FSP differences still decreased with increased speed. This algorithm, therefore, appears to preserve the ordinal relationship and the trend in relative change between FSP across speeds reflected in the other four algorithms. Overall, the consistency across all algorithms of absolute and relative decrease between FSP with increased speed suggests variations in actual kinematics, not algorithms, are responsible for observed differences

Trends in aerosol abundances and distributions

The properties of aerosols that reside in the upper atmosphere are described. Special emphasis is given to the influence these aerosols have on ozone observation systems, mainly through radiative effects, and on ambient ozone concentrations, mainly through chemical effects. It has long been appreciated that stratospheric particles can interfere with the remote sensing of ozone distribution. The mechanism and magnitude of this interference are evaluated. Separate sections deal with the optical properties of upper atmospheric aerosols, long-term trends in stratospheric aerosols, perturbations of the stratospheric aerosol layer by volcanic eruptions, and estimates of the impacts that such particles have on remotely measured ozone concentrations. Another section is devoted to a discussion of the polar stratospheric clouds (PSC's). These unique clouds, recently discovered by satellite observation, are now thought to be intimately connected with the Antarctic ozone hole. Accordingly, interest in PSC's has grown considerably in recent years. This chapter describes what we know about the morphology, physical chemistry, and microphysics of PSC's

SYMPOSIUM ON RECENT DEVELOPMENTS IN DATA ANALYSIS

The purpose of this symposium is to present recent developments in biomechanical data analyses in two areas. First, current methods used in a dynamical systems approach will be described. Second, two statistical approaches, Principal Components Analysis and Functional Data Analysis, will be presented. The emphasis in this symposium will be on how to use each of these recent analysis techniques