Snow Skiing Research Articles

A biomechanical model for actively controlled snow ski bindings.

Active control of snow ski bindings is a new design concept which potentially offers improved protection from lower extremity injury. Implementation of this concept entails measuring physical variables and calculating loading and/or deformation in injury prone musculoskeletal components. The subject of this paper is definition of a biomechanical model for calculating tibia torsion based on measurements of torsion loading between the boot and ski. Previous control schemes have used leg displacement only to indicate tibia torsion. The contributions of both inertial and velocity-dependent torques to tibia loading are explored and it is shown that both these moments must be included in addition to displacement-dependent moments. A new analog controller design which includes inertia, damping, and stiffness terms in the tibia load calculation is also presented.

Relative Motion Between Ski and Boot Under Impact Testing of Ski Bindings

The relative translation and rotation of a snow ski and boot under lateral impact of the ski is critical to the function of the ski release binding. The binding couples the ski and ski boot during skiing and releases them under potentially excessive loading of the skier’s leg. A displacement transducer was developed to measure the general, two dimensional translation and rotation of the boot relative to the ski during laboratory impact tests of bindings. The requirement that the boot and ski separate upon release of the binding complicates the transducer design. Lateral impacts were applied with a pendulum at the “ski tip”, at the “ski tail” and at the “boot toe” positions on the ski. The model leg, ankle and ski response were recorded. Significant differences in leg-ski-binding system response were observed with two commercial bindings and with the impact locations on the ski.

Identification of Lower Extremity Dynamics During Snow Skiing

Severity of the skiing environment can be interpreted only through the response of the lower extremity to the excitation of the environment. Identification of a linear, four degree of freedom, lower extremity ski torsion model was undertaken. A new procedure is introduced for filtering the deterministic trends from the random torsion data measured between the boot and ski during skiing. Trend removal is necessary for identification. The objective function for the identification was the square of the difference between the spectrum of the trend-removed torsion data and the spectrum of the model torsion. Following identification, the model responses predicted during two authentic skiing falls were computed, thus permitting a comparison of their relative severity.

Leg loading in snow skiing: Computer analyses

The complete excitation between the boot and ski was measured during snow skiing. Data from two six degree-of-freedom dynamometers mounted inside the ski were pulse-coded and FM transmitted to a remote receiving station. Data from both cruising skiing maneuvers (snowplow, stem christiana, and parallel christiana) and authentic falls were recorded. These data were subsequently analyzed both in real time and by digital computer. In the computer analyses, attention was focused on the resultant boot loads. This paper discusses two aspects of the data reduction by digital computer, computation of power spectral density estimates and normalized covariance matrices. Both of these analysis techniques not only characterize the excitation environment but also lead to important conclusions regarding safety release binding design.

Primary care of ocular emergencies

First- and second-degree flash burns can be treated by the primary care physician, but third-degree burns will require a specialist for extensive debridement and skin grafting. Actinic keratitis, often associated with welding and snow skiing, is painful but can be treated with drugs in the office. There is no treatment for eclipse burn. Alkali is more toxic to the eye than is acid and can dill corneal epithelium and endothelium. All chemical burns require copious irrigation, but a patient with an alkali burn must be sent immediately thereafter to an ophthalmic surgeion. Acute glaucoma and acute occlusion of the central retinal artery are the two major nontraumatic eye emergencies. Patients with either of these injuries should be referred to a specialist after emergency measures have been taken.

Field measurement of forces on the leg during skiing

Design of snow ski release bindings, intended to protect the leg from injury, has been hindered by the uncertainties surrounding the loading environment of skiing and the mechanisms of injury. An instrumentation system, utilizing a test ski with imbedded dynamometers and an FM‐PCM telemetry system, was developed to monitor the detailed force transmitted to the leg during actual skiing. Using this test ski subjects skied aggressively on test courses purposely set to increase the probability of falling. Unstaged falls occasionally occurred permitting measurement of the leg excitation during conditions of release and no release of the ski from the boot, as well as the excitation typical of cruising skiing. The data show the excitation of skiing to be notably higher than previously reported. The force magnitude often exceeds the typical ultimate strength of the tibial shaft in bending and torsion. The specification of design and performance criteria for release bindings are notably complicated by this observation. The contributions of muscle activity in the ski binding release problem are significant.

Analysis of Leg Loading in Snow Skiing

The complete excitation between the boot and ski was measured during skiing. Data from strain-gage force transducers mounted inside the test ski were FM transmitted to a receiving station about 3 km distant. Three skiing maneuvers (snowplow, stem christiana, parallel christiana) were tested and data from authentic falls were also recorded. Data were plotted in real-time and analyzed by digital computer. The loading histories reveal that the nonstationary loading is related to maneuver type. Torsion and bending component amplitudes, measured at the boot sole, are approximately equal to the static tibia ultimate strength in bending and torsion during both elementary skiing maneuvers and falls. In these high amplitude loading situations the skier was not injured. Data were analyzed for spectral content by the Fast Fourier Transform (FFT). Results show a 3.5 Hz cutoff frequency common to all load components and maneuvers. 3.5 Hz is a reasonable corner frequency for the human controller. Results suggest that below 3.5 Hz the skiing excitation is primarily muscle induced while above 3.5 Hz the excitation is due to ski-snow interaction.

Organizing a Course in Snow Skiing

Organizing a Course in Snow Skiing

Personality and Leisure Time Activities

Abstract Relationships between personality traits and participation in active leisure activities were studied in three groups of males participating in skydiving, scuba diving, and snow skiing. Personality data were collected from each group through the use of a self-administered instrument. The personality data were then compared to a “normative” group of 302 males. Several pragmatic and significant relationships were discovered between personality traits and participation in the three activities. The implication is that involvement in various leisure time activities is related to an individual's personality.

Divorce Adjustment Groups

The Personnel and Guidance JournalVolume 54, Issue 5 p. 250-255 Divorce Adjustment Groups Sheila Kessler, Sheila Kessler Assistant Professor/Counselor Sheila Kessler: is an Assistant Professor/Counselor in the Counseling Center at Georgia State University in Atlanta. She became intrigued with the divorce process while she was a counselor and faculty member at the University of Nevada in Reno and currently is Director of Training for the Family Mediation Center in Atlanta, is involved in the National Task Force on Divorce Reform, and is training counselors to do divorce counseling. Herself divorced (and subsequently remarried), she feels that she has been able to be emotionally sensitive to the people in her divorce adjustment groups, having gone through the process. In addition to her professional pursuits, the author enjoys outdoor activities; she spends her spare time flying her small plane, scuba diving. snow skiing, and traveling.Search for more papers by this author Sheila Kessler, Sheila Kessler Assistant Professor/Counselor Sheila Kessler: is an Assistant Professor/Counselor in the Counseling Center at Georgia State University in Atlanta. She became intrigued with the divorce process while she was a counselor and faculty member at the University of Nevada in Reno and currently is Director of Training for the Family Mediation Center in Atlanta, is involved in the National Task Force on Divorce Reform, and is training counselors to do divorce counseling. Herself divorced (and subsequently remarried), she feels that she has been able to be emotionally sensitive to the people in her divorce adjustment groups, having gone through the process. In addition to her professional pursuits, the author enjoys outdoor activities; she spends her spare time flying her small plane, scuba diving. snow skiing, and traveling.Search for more papers by this author First published: January 1976 https://doi.org/10.1002/j.2164-4918.1976.tb04241.xCitations: 9 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume54, Issue5January 1976Pages 250-255 RelatedInformation

Modeling of the Human Leg in Ski Injuries

This study establishes that the human lower extremity-ski system has a fundamental frequency of approximately 1 Hz. The fundamental mode dominates the system response when loading times are short compared to the first natural frequency. Consequently, the use of a single degree of freedom approximation and the use of impulse criteria can provide important insights into the problem of skiing injuries. Specifically, the sport of snow skiing develops forces with frequency content in the static, transition, and impulse regions of the leg-ski response spectrum. Therefore, ski release bindings must be designed to safely and effectively couple the leg to the ski throughout this loading environment. An important means of evaluating possible binding designs is by simulating their characteristics in a computer model. The model will apply realistic loading histories to the ski or binding, will evaluate the strain in the bones and ligaments of the lower extremity, and will determine the release point of the binding. The program presented in this discussion is one stage in the development of this total system capability.

Play: early and eternal.

A systematic 12-week investigation of development of play behavior was conducted with eight socially reared rhesus monkey infants. A new, basic and primary play form termed self-motion play or peragration was identified and examined. This behavior follows a human model which includes a wide range of pleasurable activities involving motion of the body through space, e.g., rocking, swinging, running, leaping, and water or snow skiing. It can be argued that self-motion play is the initial primate play form and because of its persistence constitutes a reinforcing agent for maintaining many complex patterns and even pastimes. Monkey self-motion play in the present study was divided into five separate patterns in order to compare the relative importance of social and individual peragration play, the role of apparatus and the overall developmental relationships between the different individual and social self-motion play patterns. The data showed that from 90 to 180 days of age self-motion play was independent of other forms of play, that individual self-motion play appeared earlier and with significantly greater increases in frequency than did social self-motion play, and that apparatus was a necessary component for significant increases in social self-motion play. Other findings were that self-motion play existed independent of locomotion and, though initiated by exploration, was separate from it. Therapeutic implications of self-motion play were discussed.

The Engineering Characteristics of Snow Skis—Part 1: Static Bending and Torsional Characteristics

This paper presents the results of analytical and experimental studies of static bending and torsional characteristics of snow skis. The purpose of the work is to develop analytical and experimental techniques that would be useful to the ski designer who must continually explore the applicability of new materials and geometric arrangements to snow ski construction. A brief review of composite shallow beam theory is presented in a form directly applicable to ski analysis. The experimental setup to verify the analytical results is described.

The Snow Ski as a Dynamic System

Paper reports research on dynamic system characteristics of snow skis. Laboratory and field measurements of frequency response, running surface pressure excitation, and static system characteristics are intended to provide a data base of physical information to guide future design and research. Laboratory testing procedures used give meaningful information for “straight running” but not for “turning.” In general, the turning and straight running maneuvers must be examined independently. This paper summarizes the general research observations with a minimum of detail included.

自然公園内の施設に関する研究

Outdoor recreation trends in America shown by a Bureau of Outdoor Recreation survey of participation in outdoor recreation activities. Data on which this report based was gathered by the Bereu of the Census under contract to the Bureau of Outdoor Recreation during the summer months of June, July and August, 1965. It sould be pointed out that heaviest public participation in a number of other important recreation activities, such as hunting, ice skating, snow skiing, football games and others takes place at other seasons.By the year 2000, their participation in the major forms of summertime outdoor recreation activities will be 4 times greater than it was in 1960. This is because by 1965 they already enjoyed 51 percent more outdoor recreation experiences in the major activities each summer than thay did in 1960. Now pressures on public and private outdoor recreation facilities are exceeding previous expectations by wide margins. In the natural parks we will need more recreation opportunities and service, many more visitor accomodation and facilities.

Snow Structure and Ski Fields. By G. Seligman, B.A. Being an Account of Snow and Ice Forms Met with in Nature and a Study on Avalanches and Snowcraft. With an Appendix on Alpine Weather. By 0. K. M. Douglas, B.A. Pp. xii + 555. London: Macmillan & Co., Ltd., 1936. 25s

Snow Structure and Ski Fields. By G. Seligman, B.A. Being an Account of Snow and Ice Forms Met with in Nature and a Study on Avalanches and Snowcraft. With an Appendix on Alpine Weather. By 0. K. M. Douglas, B.A. Pp. xii + 555. London: Macmillan & Co., Ltd., 1936. 25s

The Transport of Sand by Wind

The subject of course is but a special case of the general problem of the transport of solid particles by fluids. The Reynolds' Numbers involved are of the same order, whether sand is transported by air or water, and the type of motion of the grains, and their resulting drag on the fluid, appear to be much the same, though too close a parallel should not be drawn since the density ratios of sand and fluid differ greatly in the two cases. But because of the greater simplicity of experiments with air, especially in pitot-tube velocity measurements, it is possible that new facts applicable to sand-water transportation may emerge from the study of sand-air transportation. There would appear to be a closer resemblance between the behaviour of sand in air and that of drifting snow. For instance the peculiarly solid formation of wind-slab snow which G. Seligman describes in his book, 'Snow Structure and Ski Fields,' seems to have a very exact counterpart in a certain type of sand deposit which can be reproduced experimentally. Here again much might be learnt about snow-drifting from experiments made with sand, which is a far more convenient medium. The particles dealt with are defined as hard grains small enough to be set in motion by the direct forward velocity of the fluid, but too massive to be seriously affected during their flight by the less violent velocities of the fluid's internal movements. Small particles of dust are seriously affected by these internal movements, but their behaviour is beyond the scope of this paper. As an example of the susceptibility of sand grains to wind motion, a fine grain of the size (0-25 mm. diam.) commonly found at the crests of dunes when shot into still air at a speed of 4 m./sec. (9 miles per hour), travels 20 cm. before its speed is reduced by 50 per cent. Wind-driven, the sand grains move in bounds (or in saltation 2), rising steeply into the air stream, and there being urged forward by the pressure of the wind upon them. By their weight they fall to the ground again, but with a high horizontal velocity component acquired from the air. On impact with

Snow Structure and Ski Fields

Snow Structure and Ski Fields

Snow Structure and Ski Fields: Being an Account of Snow and Ice Forms Met with in Nature and a Study on Avalanches and Snowcraft

Snow Structure and Ski Fields: Being an Account of Snow and Ice Forms Met with in Nature and a Study on Avalanches and Snowcraft

Snow struckture and ski fields, by g. Seligman, B.A., F.R.Met.Sco., with an appendix on Alpine weather by C. K. M. Douglas, B.A., F.R.Met.Soc. London (Macmillan and Co.), 1936, Medium 8°. Pp. vii+555, illus. 25s

Snow struckture and ski fields, by g. Seligman, B.A., F.R.Met.Sco., with an appendix on Alpine weather by C. K. M. Douglas, B.A., F.R.Met.Soc. London (Macmillan and Co.), 1936, Medium 8°. Pp. vii+555, illus. 25s