The Relentless Attempt to Perfect the 2-Stent Technique∗

<p><b>Individual data points for one repetition maximum before (a) and after the intervention period (b) and for average power at 40% of one repetition maximum before (c) and after the intervention period (d) for the upper-body sprint-interval training group (SIG) and the control group (CG).</b> Mean values are represented by the thick line with black circles. Significant within-group changes: *p<0.05, **p<0.001; Significant different change from pre to post between groups: ^#p<0.05.</p

Practical implementation of strength training to improve the performance of world-class cross-country skiers

Current scientific evidence suggests that sport-specific heavy strength training could be successfully included in elite endurance athletes’ training program. In fact, positive effects of short-term interventions, without any negative side-effects, have been shown repeatedly. However, there is a lack of long-term studies investigating the concurrent development of strength and endurance capacities, and there is a limited understanding of the mechanisms underlying the complex mix of strength and endurance training in the daily training plan of elite endurance athletes. In this context, cross-country skiers have shown a unique ability to build up and sustain a relatively large and strong muscle mass whilst, at the same time, having developed some of the highest maximal oxygen uptakes ever measured in humans. Accordingly, this study explores and discusses how world-class cross-country skiers implement strength training in their long-term endurance training schedule. The presented examples provide support to the scientific evidence from short-term studies, with heavy strength training being included approximately two times per week to build up strength in the preparation period and once per week to maintain strength in the competition period. Furthermore, individualized, movement-specific strength programs aiming to improve skiing technique, exercise economy/ efficiency and to delay fatigue is employed. However, the systematic use of core/stabilization exercises by the best skiers has lack of scientific support, which is also the case for the placement of strength sessions within the weekly training puzzle, the order of strength exercises during a session, as well as the influence of mental abilities and technical execution during strength sessions

Training und Coaching von weiblichen vs. männlichen Athleten auf ihrem Weg zu Gold? Einschätzungen erfolgreicher Trainer von Eliteathleten

This scientific short report investigated how successful male coaches perceive gender differences in training characteristics and coaching practice among medal-winning endurance athletes. Ten male Norwegian coaches with a track record of coaching both female and male endurance world-class athletes (total of 269 Olympic, World and European Championship medals) participated in semi-structured interviews. Inductive thematic analysis revealed that all coaches mainly adjusted their key training and coaching principles to the individual athlete, rather than gender. A coach-driven and athlete-centered individualization process was essential to create trust, mutual understanding, and optimal training content. Potential gender/sex differences were perceived in four main themes: sport-specific competition demands, physiological, psychological and interpersonal factors (e.g., gender of the coach). In this context, all coaches described how training and coaching of female athletes differs from that of men, thus considering male athletes as the reference group and male physiology and psychology as the norm. Furthermore, societal factors such as a male-dominant sports culture and underlying gender stereotypes were suggested as amplifiers of gender differences. Accordingly, our report highlights the need for female perspectives in elite sports and invites further in-depth investigations of the identified gender/sex differences within the respective disciplines of training science, physiology, psychology and sociology.publishedVersio

Fibre Reinforced Concrete: Evaluation of test methods and material development

Concrete is a structural material with excellent properties when subjected to compression, butthe abilities to resist tensile stresses are rather poor. The concrete’s tensile zone is normallyreinforced with large continuous steel bars, a combination which ensures an excellentconstruction material. Placing the re-bars generates many man-hours, which means that the reinforcement work accounts for a considerable part of the total concrete cost. An alternative to the conventional re-bars is fibre reinforced concrete. Fibre reinforced concrete is concrete reinforced with small randomly distributed discontinuous fibres instead of large unidirectional continuous steel bars. In cases where thestrength and ductility of fibre reinforced concrete is sufficient with regard to the actions, fibrereinforced concrete can be an adequate and cheaper alternative to conventionally reinforced concrete. If fibres are used together with conventional re-bars, both the total load carryingcapacity and the stiffness of the structure will increase, and the crack widths will decrease. One working hypothesis in the present thesis has been that the behaviour of fibre reinforced concrete can be uniquely described by the fibre slip, and an objective has been to investigate whether this hypothesis is correct or not. Due to the fact that the maximum fibre stress achieved during pull-out test is considerably less than the fracture stress for most fibre types,it is reasonable to assume that the fibres’ pull-out length in a real structure is identical with the crack width, because the fibres will simply loosen at the weakest side of a crack. Based on alarge number of experiments, and some simplified models which relate the experimental results to crack openings, it seems like the working hypothesis is correct. A theoretical relation between the results from energy absorption test found by two differenttest codes is established. This relation is based on the above mentioned working hypothesis,and it is shown that the theoretical relation corresponds well to an empirical relation found in the literature. A second objective has been to show that fibre reinforcement actually has sufficient strength and ductility to be used as a replacement to conventional re-bars in some types of concretestructures. A concrete called ductile high tensile strength all round concrete is developed, and this concrete shows promising properties with regard to both shear strength, bending strength and ductility. The last few pages of the present thesis deals with some paradoxes from some of the material models used to describe fibre reinforced concrete from the literature. The experiences from the experimental work, and the analyses of the results, indicate that the fibre efficiency is increased by increasing crack widths until the crack widths reaches a certain level, while most of the models suggest that fibres are most effective at smaller crack widths.PhD i konstruksjonsteknikkPhD in Structural Engineerin

Let's Close the Gap Between Research and Practice to Discover New Land Together!

acceptedVersionAccepted author manuscript version reprinted, by permission, from International Journal of Sports Physiology and Performance, 2018, http://dx.doi.org/10.1123/ijspp.2018-0550 © Human Kinetics, Inc

The Role of Sport Science in the New Age of Digital Sport

acceptedVersion© 2019. This is the authors' accepted and refereed manuscript to the article. The final authenticated version is available online at: http://dx.doi.org/https://doi.org/10.1123/ijspp.2019-093

Physiological and Biomechanical Aspects of Sprint Skiing

Sprint cross-country skiing is a physiologically and technically complex discipline, performed as a time-trial qualification race and three subsequent knock-out heats. The racing time in a single heat is 2-4 min and is comparable to other middle-distance sports. However, sprint skiing is performed in varied terrain at constantly changing intensities using multiple techniques involving the arms and the legs to various degrees. The overall objectives of the current thesis were to examine physiological and biomechanical aspects associated with sprint skiing performance in the skating technique in elite skiers: 1) while treadmill roller skiing in the laboratory (studies I-IV), 2) during sprint competitions on snow (studies IV-V) and 3) for relationships between laboratory characteristics and performance on snow (studies IV-V). Studies I-III are comparative studies in which physiological characteristics, mechanical efficiency and gross kinematics during treadmill roller skiing were compared between male world-class and national level sprint skiers (studies I-II), and between men and women matched for performance level (study III). Study I showed that maximal aerobic capacity, gross efficiency and high speed capacity differentiated world-class from national level sprint skiers. The study also indicated that low and moderate intensity endurance training and maximal speed training is important in attaining an international level in sprint skiing. Study II demonstrated that world-class sprint skiers had a higher gross efficiency than national level skiers. A general linear relationship between work rate and metabolic rate existed, indicating that gross efficiency at moderate and high work rates provides useful information about crosscountry skiers in standardized conditions during treadmill roller skiing. Furthermore, worldclass skiers used longer cycle lengths and lower cycle rates at a given speed and generated higher maximal speeds. In study III, men showed a 17% higher peak treadmill speed at a short and long incremental test compared to women. These gender differences were slightly greater than findings in comparable endurance sports. The majority of gender differences in performance could be explained by higher maximal oxygen uptakes and lower fat percentages in men. Men and women showed similar gross efficiency. However, women showed higher fractional utilization of maximal oxygen uptake at the anaerobic threshold. In studies IV-V, elite male skiers were analyzed for speeds, work rates, technique choices and gross kinematics during two sprint time-trial competitions on snow. Furthermore, the skiers were tested for physiological and kinematical characteristics in the laboratory. Study IV analyzed the time-trial of an international sprint competition. The results showed that performance on uphill and flat terrain strongly determined sprint time-trial performance, and that performance in the last half of the race differentiated most between skiers. Estimated work rates on an uphill section of the race were approximately 60% higher than the capacities which the skiers are able to cover aerobically. Peak oxygen uptake, gross efficiency, peak treadmill speed and peak cycle length were strongly related to sprint time-trial performance, particularly to the uphill and flat sections during the last part of the race. Study V analyzed a simulated sprint race by using a high end differential global navigation satellite system with simultaneous tracking of both GPS and GLONASS satellites. This provided an opportunity for more detailed analysis of cross-country skiing. Skiers encompassed a large speed range (2.9–12.9 m·s-1) and multiple transitions between skiing techniques (range: 21–34 transitions). The results demonstrated that performance in the uphill sections had the strongest correlation to sprint performance, and that the faster skiers used the G3 technique to a greater extent than the slower skiers. Thus, this provides new knowledge on physiological and biomechanical aspects of sprint skating performance, particularly that both the maximal aerobic and peak speed capacities differed between world-class and national level sprint skiers. Furthermore, gross efficiency, while treadmill roller skiing provides relevant information strongly related to sprint performance level. Better skiers also employ longer cycle lengths at the same absolute speeds and at individual peak speeds. The gender differences in performance were slightly larger than expected; however, most of these differences could be explained by a higher maximal oxygen uptake and a lower fat percentage in men. Furthermore, the variations in speeds, work rates and techniques and, especially, speed in uphill and flat terrain are important to the skiers’ total time-trial performance. Better sprint performance is related to more application of the G3 technique and to longer cycle lengths within this technique. Faster skiers showed higher peak oxygen uptake, gross efficiency and high speed capacity. These capacities were specifically correlated to the ability to maintain high speed on uphill and flat terrain throughout a sprint race. &nbsp;Sprintlangrenn er ein fysiologisk og biomekanisk kompleks disiplin som blir utført som ein prolog og tre etterfølgjande utslagsløp. Konkurransetidene i kvart enkelt heat er 2-4 min og kan samanliknast med andre mellomdistanseidrettar. Sprintlangrenn blir imidlertid gjennomført i kupert terreng og med varierande arbeidsintensitet og innslag av ulike teknikkar som involverer underkropp og overkropp i ulik grad. Den overordna målsetjinga med denne avhandlinga var å undersøke fysiologiske og biomekaniske aspekt som er assosiert med prestasjonen i sprint skøyting hos elite langrennsløparar: 1) på rulleskitredemølle i laboratoriet (studia I-IV), 2) i sprintkonkurransar på snø (studia IV-V), og 3) for samanhengar mellom laboratorium-karakteristikkar og sprintprestasjonen på snø (studia IV-V). Studia I-III undersøker forskjellar i fysiologiske karakteristikkar, mekanisk effektivitet og kinematikk mellom mannlege verdsklasse og nasjonal klasse sprintlangrennsløparar (studia III) og mellom mannlege og kvinnelege sprintlangrennsløparar på tilsvarande prestasjonsnivå (studie III). Studie I viser at maksimal aerob kapasitet, mekanisk effektivitet og hurtigheit skil verdsklasse frå nasjonal klasse sprintlangrennsløparar. Studiet indikerer også at låg- og moderat-intensiv uthaldstrening og maksimal hurtigheitstrening er viktig for å nå internasjonalt nivå i sprintlangrenn. Studie II viser at verdsklasse sprintlangrennsløparar har betre mekanisk effektivitet enn løparar på nasjonalt nivå. Studiet viser ein generell lineær samanheng mellom arbeidsratar og energiforbruk og indikerer at målingar av mekanisk effektivitet gir nyttig og valid informasjon om langrennsløparar som blir samanlikna under standardiserte vilkår på rulleskitredemøller. Studiet demonstrerer også at verdsklasse løparane har lengre sykluslengder og lågare syklusfrekvens på ei gitt fart. Studie III viser at menn oppnår 17 % høgre fart enn kvinner både på ein kort og ein lang prestasjonstest med trinnvis aukande fart på rulleskitredemølla. Resultata indikerer at prestasjonsforskjellane mellom kjønna hovudsakleg kan forklarast av høgare maksimalt oksygenopptak og lågare feittprosent hos menn, og at forskjellane er noko større enn det litteraturen viser i andre tilsvarande uthaldsidrettar. Kvinner og menn har lik effektivitet, mens kvinner har høgare prosentvis utnytting av maksimalt oksygenopptak ved anaerob terskel. I studia IV-V vart fart, arbeidsratar, teknikkval og kinematikk undervegs i sprintkonkurransar undersøkt. Vidare blei samanhengar mellom fysiologiske og kinematiske karakteristikkar i laboratoriet og sprintprestasjonen på snø undersøkt. I studie IV vart prologen i ein internasjonal sprintkonkurranse analysert. Resultata viser at prestasjonen i motbakke og i flatt terreng er sterke forklaringsvariablar for den totale prologprestasjonen. Studiet indikerer også at prestasjonen i siste halvdelen av løypa skil løparane mest. Estimerte arbeidsratar i motbakke indikerer eit totalt arbeid omlag 60% høgare enn det løparane klarer å dekke med aerob energi. Maksimalt oksygenopptak, mekaniske effektivitet, fartskapasitet og sykluslengde var sterkt relatert til sprintprestasjonen, og spesielt til farta i flatt terreng og motbakkar i siste halvdelen av løpet. I studie V vart ein simulert sprintprolog analysert ved bruk av ein høgteknologisk differensial GPS, med svært høg samplingsfrekvens og nøyaktigheit, som hadde samtidig mottak av GPS- og GLONASS-satellittar. Løparane gjennomførte sprintkonkurransen i variert terreng, noko som førte til eit spenn i hastigheiter frå 2.9 til 12.9 m·s-1 og som inkluderte 21–34 teknikkendringar. Motbakkeprestasjonen var høgast korrelert til total prestasjon, og betre skiløparar brukte dobbeldansteknikken i større grad, samanlikna med mindre gode løparar. Samanfatta så bidreg denne avhandlinga med ny kunnskap om fysiologiske og biomekaniske aspekt av sprintlangrenn i skøyting. Det viser at både maksimal aerob kapasitet og fartskapasitet skil verdsklasse frå nasjonal klasse sprintlangrennsløparar. Det er også vist at målingar av mekanisk effektivitet på rulleskitredemølle gir valid informasjon og er sterkt relatert til prestasjonsnivået til løparane. Dei beste løparane bruker lengre sykluslengder både på same submaksimale fart og på si høgste individuelle fart. Forskjellane mellom mannlege og kvinnelege sprintløparar i prestasjon er noko større enn forventa. Det meste av desse kjønnsforskjellane kan forklarast av at menn har høgare maksimalt oksygenopptak og lågare feittprosent. Undervegs i sprintprologar viser løparane store variasjonar i fart, arbeidsratar og vekslar stadig mellom ulike teknikkar. Spesielt er farta i motbakkar og flatt terreng mot slutten av løpa betydningsfull for prologprestasjonen. Betre prologprestasjon er linka til meir bruk av dobbeldansteknikken og lengre sykluslengder innan denne teknikken. Betre utøvarar har også høgare maksimalt oksygenopptak, effektivitet og fartskapasiet, noko som vart relatert til evna til å oppretthalde høg fart i motbakkar og flatt terreng gjennom eit sprintløp.PhD i helsevitenskapPhD in Health Scienc

Practical implementation of strength training to improve the performance of world-class cross-country skiers

Current scientific evidence suggests that sport-specific heavy strength training could be successfully included in elite endurance athletes’ training program. In fact, positive effects of short-term interventions, without any negative side-effects, have been shown repeatedly. However, there is a lack of long-term studies investigating the concurrent development of strength and endurance capacities, and there is a limited understanding of the mechanisms underlying the complex mix of strength and endurance training in the daily training plan of elite endurance athletes. In this context, cross-country skiers have shown a unique ability to build up and sustain a relatively large and strong muscle mass whilst, at the same time, having developed some of the highest maximal oxygen uptakes ever measured in humans. Accordingly, this study explores and discusses how world-class cross-country skiers implement strength training in their long-term endurance training schedule. The presented examples provide support to the scientific evidence from short-term studies, with heavy strength training being included approximately two times per week to build up strength in the preparation period and once per week to maintain strength in the competition period. Furthermore, individualized, movement-specific strength programs aiming to improve skiing technique, exercise economy/efficiency and to delay fatigue is employed. However, the systematic use of core/stabilization exercises by the best skiers has lack of scientific support, which is also the case for the placement of strength sessions within the weekly training puzzle, the order of strength exercises during a session, as well as the influence of mental abilities and technical execution during strength sessions.publishedVersionCopyright (c) 2018 Kinesiology. This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License