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Flow field measurements around cross-country skiers (xc skiers) are lacking in the literature to date. The aim was therefore to investigate the possibility of using particle tracking velocimetry for visualization and measurement of the flow field around xc skiers roller skiing on a treadmill in a wind tunnel. The airflow was seeded with neutrally buoyant helium-filled soap bubbles as tracer particles, following the flow without affecting it. As illumination, two different approaches were tested: first, a laser in the cameras’ line of sight (sagittal plane), then an LED unit directed vertically in a narrow slice, clearly limiting the depth of the measurement volume in the cameras’ line of sight. The flow field was studied at various speeds (3-7 m/s) around a single skier as well as around two skiers in line with the streaming airflow. It was found that the experimental approach has the potential to provide detailed insights, both qualitatively and quantitatively, into the flow field dynamics. The main challenges regarding setup, illumination, seeding, and cameras were identified, and possible improvements to streamline the experimental methodology were discussed., Validerad;2024;Nivå 1;2024-05-16 (hanlid);Full text license: CC BY-NC

Bakgrund Ansträngningsutlöst bronkkonstriktion (EIB) innebär en övergående luftvägsobstruktion i samband med ansträngning och definieras som en minskning med ≥ 10% av den forcerade utandningen under första sekunden (FEV1). EIB är vanligt bland elitskidåkare. Referenstestet för diagnostik är torrluftsprovokation men ansträngningstest (ECT) i fält anses ha högre representativitet och sensitivitet men är svårt att standardisera. ECT i köldkammare kombinerar en idrottspecifik provokation med en standardiserad miljö men har aldrig använts för att undersöka förekomsten av EIB bland vinteridrottare. Målet med studien var att kartlägga prevalensen av EIB hos elitskidåkare med hjälp av ECT i kyla. Material och metod De 31 deltagarna (16 kvinnor) var ett slumpmässigt urval av de 174 längdskidåkare och skidskyttar från Sveriges riksidrottsgymnasium och nationella idrottsutbildningar som vintern 2022 deltog i en web-enkät om luftvägssymtom, träning och astma. Sex (19%) deltagare hade använt astmamediciner för en läkardiagnostiserad astma de senaste 12 månaderna. ECT i en köldkammare utfördes (8 min löpning i -14,7 °C, Rh 77% på 85% av beräknad maxpuls) med spirometri före och 5-30 minuter efter. Resultat EIB detekterades hos 7 (23%) av deltagarna, 5 av 25 utan astma och 2 av 6 med astma. En deltagare sjönk >15% på FEV1 och hade ingen tidigare känd astma. Kön, ålder, träningstimmar, allergi, FeNO och förekomst av pip/väs från luftvägarna med andnöd de senaste 12 månaderna skiljde sig inte åt mellan deltagarna med och utan EIB. Slutsats ECT i kyla påvisar en hög förekomst av EIB hos unga, friska, svenska elitskidåkare, redan tidigt i karriären och oavsett tidigare känd astma. Att förekomsten av EIB hos skidåkarna med astma inte var högre skulle kunna vara ett resultat av deras antiinflammatoriska astmaläkemedel eller överdiagnostik.

Background and Aims: Winter endurance athletes have a high prevalence of exercise-induced bronchoconstriction (EIB) and asthma, probably due to repeated and prolonged inhalation of cold and dry air. Heat- and moisture-exchanging devices (HME) warm and humidify inhaled air and prevent EIB. The aim of this study was to share cross-country skiers and biathletes' experiences of training and competition in low temperatures, views on temperature limits, usage of HME, and consequences of cold exposure on their health. Methods: Eleven Swedish World Championship or Olympic medalists in cross-country skiing and biathlon were interviewed and transcripts were analyzed using qualitative content analysis. Results: Participants described how cold temperatures predominantly affected the airways, face, and extremities. During training, extreme cold was managed by choosing warmer clothing, modification of planned sessions, use of HME, delaying training, or changing location. In competition, participants described limited possibility for such choices and would prefer adjustment of existing rules (i.e., more conservative temperature limits), especially since they understood elite skiing in low temperatures to present an occupational hazard to their health. Participants had at times used HMEs during training in cold environments but described mixed motives for their use—that HMEs warm and humidify cold inhaled air but introduce additional resistance to breathing and can cause problems due to mucus and ice build-up. Skiers also perceived that they had become more sensitive to cold during the latter part of their careers. Conclusions: The present study gives a unique insight into the “cold” reality of being an elite athlete in skiing and biathlon. Cold exposure results in negative health consequences that are preventable, which means that rules must be followed, and organizers should acknowledge responsibility in protecting athletes from occupational hazards. Development of evidence-based

Purpose This study aimed to investigate the effects of aerodynamic drag and drafting on propulsive force (FPROP), drag area (CDA), oxygen cost (V˙O2), metabolic rate (Ė), and heart rate (HR) during roller skiing on a treadmill in a wind tunnel using the double poling technique. A secondary aim was to investigate the effects of wind versus no-wind test conditions on the same physiological parameters. Methods Ten subjects of each gender participated in the experiments. One pair of skiers of the same gender roller skied simultaneously in line with the air flow; the distance between the skiers was 2.05 m. Each pair was tested as follows: I) with wind, leading; II) with wind, drafting; and III) without wind. The treadmill inclination was 0° throughout the tests. For the wind conditions, the air velocity was similar to the treadmill belt speed: 3 to 7 m·s-1 for men and 3 to 6 m·s-1 for women. Results Drafting resulted in significantly (P < 0.05) lower FPROP,CDA, V˙O2, and Ė, compared with leading, for both genders at racing speed but not at lower speeds, whereas HR was only affected for the male skiers at racing speed. The test without wind resulted in significantly lower FPROP, V˙O2, and Ė at all tested speeds compared with the tests with wind present, whereas HR was lower only at higher speeds. Conclusions At racing speed, but not at lower speeds, the positive effects of drafting behind a skier during double poling were obvious and resulted in a lower FPROP, CDA, V˙O2, Ė, and HR. Tests without wind present put even lower demands on the skiers' physiology, which was also evident at lower speeds.