Zjišťování průběhu změn teploty sněhu v běžecké stopě

Jan Ondráček; Jan Novotný ml.; Jan Novotný; Božena Paugschová

doi:10.5817/sts2010-2-5

Zjišťování průběhu změn teploty sněhu v běžecké stopě

Studia sportiva ◽

10.5817/sts2010-2-5 ◽

2010 ◽

Vol 4 (2) ◽

pp. 43-48

Author(s):

Jan Ondráček ◽

Jan Novotný ml. ◽

Jan Novotný ◽

Božena Paugschová

Keyword(s):

Infrared Thermography ◽

Repeated Observations ◽

Frequency Sampling ◽

Dynamic Thermography ◽

Snow Temperature ◽

Classical Competition

Friction of pair of skis increases the temperature of the snow in the skiing track.Th is temperature is connected with the use of specifi c wax in rising tube in the ski for classic. Th e main aim of our thesis is to fi nd out with a help of infrared thermography if the change of this temperature of skiing track before and aft er passage of the team of skiers is so important that it can infl uence service of skies for competition reasons. To fi nd out the changes of snow temperature in the skiing track we have used thermographical system FLIR SC 620 with frequency sampling of 30Hz.Th is system was used aft er passage of a group of 11 skiers. Signifi cant continual increase of snow temperature has been indicated when group of skiiers passed (0,87±0,153 °C) and decrease to original level 10 - 30 seconds aft er passage of skiers. Flat dynamic thermography could help, on given conditions, for ”correction” of tactic in classical competition with collective start and also when choosing correct wax. In order to be able to get more signifi cant fi ndings it is neccessary to make repeated observations on conditions that are similar to real competition or right during classical competition with the skiing track on plain or ascending surface.

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Teplota sněhu při běhu na lyžích v obraze dynamické termografie (pilotní studie)

Studia sportiva ◽

10.5817/sts2010-2-3 ◽

2010 ◽

Vol 4 (2) ◽

pp. 25-32

Author(s):

Jan Novotný Sr. ◽

Jan Novotný

Keyword(s):

Pilot Study ◽

Infrared Thermography ◽

Linear Dependence ◽

Thermodynamic Studies ◽

Thermal Changes ◽

Cross Country ◽

Snow Temperature ◽

Image Frequency ◽

Moving Speed

The effect of ski friction on the snow temperature increasing is known. Th e made water fi lm facilitates the ski moving. Th e aim of our pilot study was to ascertain a capability of the dynamic infrared thermography to register the quick thermal changes at determined point of snow before and aft er ski moving. We monitored snow aft er immediately before and aft er 12 runs of recreational cross-country skier by dynamic infrared thermography FLIR SC620 with image frequency 30 Hz. We found signifi cant increasing of snow temperature (by 0,2 to 1,7°C), linear dependence of snow warming on ski moving speed, and temperature increasing aft er ski waxing. Th e study confi rmed the dynamic infrared thermography ability to register very quick changes at determined point of snow temperature before and aft er (less than 0,033 s) cross-country skier moving. We have opened next thermodynamic studies for profound understanding of cross-country ski friction and gliding on snow.

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Změna teplot sněhu při běhu na lyžích v obraze sekvenční termografie

Studia sportiva ◽

10.5817/sts2010-2-13 ◽

2010 ◽

Vol 4 (2) ◽

pp. 109-118

Author(s):

Jan Novotný ◽

Jan Ondráček ◽

Jan Novotný sr.

Keyword(s):

Infrared Thermography ◽

Paired Comparison ◽

Wilcoxon Test ◽

Graphic System ◽

Temperature Changes ◽

Change Of State ◽

Rapid Changes ◽

Baseline Temperature ◽

Rapid Temperature ◽

Dynamic Thermography

Twenty years ago it was shown that friction increases the temperature of snow skis. Change of state permits for water skis glide. Th e aim of this pilot study was to determine whether dynamic infrared thermography is able to capture rapid changes in temperature of snow some areas (not just at one point), the ski tracks before and aft er passing. We monitored the snow on the track aft er 60 races two runners in various weights (86 and 73 kg) on two types of skis and lubrication (for classic and skating cross) and three diff erent speeds (3,04±0,180, 3,81±0,273 a 5,30±0,314 m.s-1). Measurements of infrared radiation and the calculation of snow surface temperature immediately before and aft er passing skier was carried out thermo-graphic system FLIR SC620 with 30 Mhz. Nonparametric Wilcoxon test for paired comparison of values was found signifi cant increases in temperature aft er the snow cleared the skies: runner A from -3,71 to -3,50 °C (p=0,000000) and runner B from -3,75 na -3,50 °C (p=0,000000). To return to the baseline temperature is within 5 seconds aft er passing. Diff erences were demonstrated in the heat of snow between runners with diff erent masses and for the use of diff erent types of skis. Th e study confi rmed the ability of dynamic infrared thermography to register a very rapid temperature changes of snow in an area immediately before and aft er crossing the cross-country skiers. Dimensional dynamic thermography would seem to contribute to the choice of the correct strategy and lubrication in ski racing. However, it is necessary to make a series of validation studies.

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