| 1. |
- Ainegren, Mats
(författare)
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Roller skis' rolling resistance and grip characteristics : influences on physiological and performance measures in cross-country skiers
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis was to investigate roller ski characteristics; classical and freestyle roller skis’ rolling resistance coefficients (μR) and classical style roller skis’ static friction coefficients (μS), and to study the influence of different μR and μS on cross-country skiers’ performance and both physiological and biomechanical indices. The aim was also to study differences in skiing economy and efficiency between recreational skiers, female and male junior and senior elite cross-country skiers.The experiments showed that during a time period of 30 minutes of rolling on a treadmill (warm-up), μR decreased significantly (p<0.05) to about 60-65 % and 70-75 % of its initial value for freestyle and classical roller skis respectively. Also, there was a significant influence of normal force on μR, while different velocities and inclinations of the treadmill only resulted in small changes in μR.The study of the influence on physiological variables of a ~50 % change in μR showed that during submaximal steady rate exercise, external power, oxygen uptake, heart rate and blood lactate were significantly changed, while there were non-significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests showed that time to exhaustion was significantly changed and this occurred without a change in maximal power, maximal oxygen uptake, maximal heart rate and blood lactate, and that the influence on ratings of perceived exertion was non-significant or small.The study of classical style roller skis μS showed values that were five to eight times more than the values of μS reported from on-snow skiing with grip-waxed cross-country skis.The subsequent physiological and biomechanical experiments with different μS showed a significantly lower skiing economy (~14 % higher v̇O2), higher heart rate, lower propulsive forces coming from the legs and shorter time to exhaustion (~30 %) when using a different type of roller ski with a μS similar to on-snow skiing, while there was no difference between tests when using different pairs of roller skis with a (similar) higher μS.The part of the thesis which focused on skiing economy and efficiency as a function of skill, age and gender, showed that the elite cross-country skiers had better skiing economy and higher gross efficiency (5-18 %) compared with the recreational skiers, and the senior elite had better economy and higher efficiency (4-5 %) than their junior counterparts, while no differences could be found between the genders.
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| 2. |
- Ainegren, Mats, et al.
(författare)
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Skiing economy and efficiency in recreational and elite cross-country skiers
- 2013
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Ingår i: Journal of Strength and Conditioning Research. - 1064-8011 .- 1533-4287. ; 27:5, s. 1239-1252
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate and compare skiing economy and gross efficiency in cross-country skiers of different performance levels, ages and genders; male recreational skiers and elite senior and junior cross-country skiers of both genders. The skiers performed tests involving roller skiing on a treadmill using the gear 3 and diagonal stride techniques. The elite crosscountry skiers were found to have better skiing economy and higher gross efficiency (5-18%) compared with the recreational skiers (p < 0.05) and the senior elite had better economy and higher efficiency (4-5%) than their junior counterparts (p < 0.05), whereas no differences could be found between the genders. Also, large ranges in economy and gross efficiency were found in all groups. It was concluded that, in addition to v̇O2peak, skiing economy and gross efficiency have a great influence on the differences in performance times between recreational and junior and senior elite cross-country skiers, as well as between individual skiers within the different categories. Thus, we recommend crosscountry skiers at all performance levels to test not only v̇O2peak, but also skiing economy and efficiency.
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| 3. |
- Ainegren, Mats, et al.
(författare)
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The influence of grip on oxygen consumption and leg forces when using classical style roller skis
- 2014
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Ingår i: Scandinavian Journal of Medicine and Science in Sports. - : John Wiley & Sons. - 0905-7188 .- 1600-0838. ; 24:2, s. 301-310
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate the influence of classical style roller skis' grip (static friction coefficients, μ S) on cross-country skiers' oxygen consumption and leg forces during treadmill roller skiing, when using the diagonal stride and kick double poling techniques. The study used ratcheted wheel roller skis from the open market and a uniquely designed roller ski with an adjustable camber and grip function. The results showed significantly (P≤0.05) higher oxygen consumption (∼14%), heart rate (∼7%), and lower propulsive forces from the legs during submaximal exercise and a shorter time to exhaustion (∼30%) in incremental maximal tests when using roller skis with a μ S similar to on-snow skiing, while there was no difference between tests when using different pairs of roller skis with a similar, higher μ S. Thus, we concluded that oxygen consumption (skiing economy), propulsive leg forces, and performance time are highly changed for the worse when using roller skis with a lower μ S, such as for on-snow skiing with grip-waxed cross-country skis, in comparison to ratcheted wheel roller skis with several times higher μ S.
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| 4. |
- Ainegren, Mats, 1963-
(författare)
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The rolling resistances of roller skis and their effects on human performance during treadmill roller skiing
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modern ski-treadmills allow cross-country skiers, biathletes and ski-orienteers to test their physical performance in a laboratory environment using classical and freestyle techniques on roller skis. For elite athletes the differences in performance between test occasions are quite small, thus emphasising the importance of knowing the roller skis’ rolling resistance coefficient, µR, in order to allow correct comparisons between the results, as well as providing the opportunity to study work economy between different athletes, test occasions and core techniques.Thus, one of the aims of this thesis was to evaluate how roller skis’ µR is related to warm-up, mass, velocity and inclination of the treadmill. It was also necessary to investigate the methodological variability of the rolling resistance measurement system, RRMS, specially produced for the experiments, with a reproducibility study in order to indicate the validity and reliability of the results.The aim was also to study physiological responses to different µR during roller skiing with freestyle and classical roller skis and techniques on the treadmill as a case in which all measurements were carried out in stationary and comparable conditions.Finally, the aim was also to investigate the work economy of amateurs and female and male junior and senior cross-country skiers during treadmill roller skiing, i.e. as a function of skill, age and gender, including whether differences in body mass causes significant differences in external power per kg due to differences in the roller skis’ µR.The experiments showed that during a warm-up period of 30 minutes, µR decreased to about 60-65% and 70-75% of its initial value for freestyle and classical roller skis respectively. For another 30 minutes of rolling no significant change was found. Simultaneous measurements of roller ski temperature and mR showed that stabilized mR corresponds to a certain running temperature for a given normal force on the roller ski. The study of the influence on mR of normal force, velocity and inclination produced a significant influence of normal force on mR, while different velocities and inclinations of the treadmill only resulted in small changes in mR. The reproducibility study of the RRMS showed no significant differences between paired measurements with either classical or the freestyle roller skis.The study of the effects on physiological variables of ~50% change in µR,showed that during submaximal steady state exercise, external power, oxygen uptake, heart rate and blood lactate were significantly changed, while there were non significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests showed that time to exhaustion was significantly changed and this occurred without a significantly changed maximal power, maximal oxygen uptake, maximal heart rate and blood lactate, and that the influence on ratings of perceived exertion was non significant or small.The final part of the thesis, which focused on work economy, found no significant difference between the four groups of elite competitors, i.e. between the two genders and between the junior and senior elite athletes. It was only the male amateurs who significantly differed among the five studied groups. The study also showed that the external power per kg was significantly different between the two genders due to differences in body mass and mR, i.e. the lighter female testing groups were roller skiing with a relatively heavier rolling resistance coefficient compared to the heavier testing groups of male participants.
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| 5. |
- Ainegren, Mats, 1963-, et al.
(författare)
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Work economy of amateur and elite cross-country skiers during treadmill roller skiing
- 2009
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Ingår i: 4th Asia Pacific Congress on Sports Technology, APCST2009. - 9781921426384
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Konferensbidrag (refereegranskat)abstract
- This study focused on the work economy of cross-country skiers during treadmill roller skiing in the perspectives; skill, age and gender. The study was investigating the external power output from elevating the transported mass against gravity and overcoming the roller skis rolling resistance, and the internal power from measured oxygen uptake and energy consumption. The roller skis rolling resistance was measured with a fixture on the ski-treadmill and the results showed a significant correlation between normal force and rolling resistance. The results also showed that it was only the amateur skiers who significantly differed in work economy among the five studied groups.
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| 6. |
- Björklund, Glenn, et al.
(författare)
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Blood lactate recovery and respiratory responses during diagonal skiing of variable intensity
- 2011
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Ingår i: European Journal of Sport Science. - : Informa UK Limited. - 1746-1391 .- 1536-7290. ; 11:5, s. 317-326
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Tidskriftsartikel (refereegranskat)abstract
- The aims of the study were to investigate blood lactate recovery and respiratory variables during diagonal skiing of variable intensity in skiers at different performance levels. Twelve male cross-country skiers classified as elite (n=6; VO2max=73±3 ml. kg-1. min-1) or moderately trained (n=6; VO2max=61±5 ml. kg-1. min-1) performed a 48-min variable intensity protocol on a treadmill using the diagonal stride technique on roller skis, alternating between 3 min at 90% and 6 min at 70% of VO2max. None of the moderately trained skiers were able to complete the variable intensity protocol and there was a difference in time to exhaustion between the two groups (elite: 45.0±7.3 min; moderately trained: 31.4±10.4 min) (P<0.05). The elite skiers had lower blood lactate concentrations and higher blood base excess concentrations at all 70% workloads than the moderately trained skiers (all P<0.05). In contrast, VE/VO2 and VE/VCO2 at the 70% VO2max workloads decreased independently of group (P<0.05). Partial correlations showed that VO2max was related to blood lactate at the first and second intervals at 70% of VO2max (r=-0.81 and r=-0.82; both P<0.01) but not to VE/VO2, VE/VCO2 or the respiratory exchange ratio. Our results demonstrate that during diagonal skiing of variable intensity, (1) elite skiers have superior blood lactate recovery compared with moderately trained skiers, who did not show any lactate recovery at 70% of VO2max, suggesting it is an important characteristic for performance; and (2) the decreases in respiratory exchange ratio, VE/VO2, and VE/VCO2 do not differ between elite and moderately trained skiers.
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| 7. |
- Björklund, Glenn, 1972-, et al.
(författare)
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The balancing act between skiing and shooting – the determinants of success in biathlon pursuit and mass start events
- 2022
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Ingår i: Journal of Sports Sciences. - : Informa UK Limited. - 0264-0414 .- 1466-447X. ; 40:1, s. 96-103
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to investigate how skiing speed (SS), number of missed targets (MT) and range time (RT) were associated with final rank in biathlon pursuit and mass start competitions. Data were collected from the International Biathlon Union’s database over 17 seasons. Biathletes were categorised into three groups (rank 1–3, G3; rank 4–10, G10; rank 11–20, G20). Multinomial regression was used to identify odds ratios associated with group rank in both sexes. The only variable found to be consistently related to G3 in both pursuit and mass start was MT (men OR 1.206–1.729 and women OR 1.340–3.124, all p < 0.01). SS during lap four of pursuit and mass start was most strongly related to G3 for both sexes (men OR 0.231–0.094 and women OR 0.339–0.126, all p < 0.001). RT during shooting four in pursuit was most strongly related to G3 compared to G10 and G20 (men OR 1.067; 95% CI, 1.030–1.105 and women OR 1.076; 95% CI, 1.020–1.134, all p < 0.001, respectively). Accordingly, MT was most strongly related to final rank in both sexes, while SS during lap four and last RT was also significant.
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| 8. |
- Björklund, Glenn, 1972-, et al.
(författare)
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The Determinants of Performance in Biathlon World Cup Sprint and Individual Competitions
- 2022
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Ingår i: Frontiers in Sports and Active Living. - : Frontiers Media SA. - 2624-9367. ; 4:March, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The present study aimed to determine the association of skiing speed (SS), range time (RT), and the number of missed targets (MT) with rank in sprint and individual biathlon competitions.Methods: Data were collected from the International Biathlon Union's database for 17 seasons (2002/2003–2018/2019). Furthermore, the biathletes were divided into three rank groups (G3, rank 1–3; G10, rank 4–10; and G20, rank 11–20). Multinominal regression was used to detect odds ratios associated with group rank for both sexes, separately.Results: MT was the only variable that was constantly related to G3 (OR 1.90–6.35, all p < 0.001) for both women and men. SS was associated with G3 in the last lap in the sprint for both sexes (OR 0.46–0.66, all p < 0.001) and RT for standing shooting (OR 1.04–1.14, all p < 0.05).Conclusion: These results show that shooting is the fundamental factor for performance in both competitions, but that SS is increasingly important for the last lap in the sprint for both sexes. Further, a fast RT in the standing shooting for women in individual and men in the sprint seems important for improving final rank.
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| 9. |
- Brandts, Maxime, et al.
(författare)
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The effect of rifle carriage on skiing performance and angular kinematics in biathletes
- 2022
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Konferensbidrag (refereegranskat)abstract
- AimTo assess the effect of rifle carriage on skiing performance and angular kinematics in biathletes,and whether the rifle’s effect on angular kinematics could explain its effect on skiing performance, under ecologically valid conditions.MethodsTwenty-nine biathletes (11 females, 18 males) performed two maximum effort skiing time-trials on snow, once with and once without rifle. During time-trials, biathletes wore a three-dimensional motion analysis system to measure maximum angle, minimum angle and range of motion of knee, hip and elbow flexion. A two-way mixed model analysis of variance and multilevel linear model were used to assess the effect of rifle carriage on skiing performance and angular kinematics respectively. In case of a significant effect, a Pearson correlation coefficient was calculated to assess the relation between the rifle’s effect on the respective angular measure and the rifle’s effect on skiing speed.ResultsSkiing performance was impaired with rifle compared to without rifle (P<.001; ƞ2p=0.04). No effect of rifle carriage was observed on any angular measure, except for maximum elbow flexion(P=.03; Cohen f 2<0.01). Maximum elbow flexion was reduced with rifle compared to without rifle (mean difference 11.9±37.6°). Pearson correlation coefficient revealed a positive correlation between the rifle’s effect on maximum elbow flexion and its effect on skiing speed (r=0.19; P=.04).Practical applicationThe results demonstrate the negative impact of rifle carriage on biathlon skiing performance and suggest that maximum elbow flexion plays a role. Therefore, upper body contributions, elbow flexion angles in particular, might be of interest for biathlon coaches.
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| 10. |
- Burger, Claudia, et al.
(författare)
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Climate change, breeding date and nestling diet : how temperature differentially affects seasonal changes in pied flycatcher diet depending on habitat variation
- 2012
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Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 81:4, s. 926-936
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Tidskriftsartikel (refereegranskat)abstract
- 1. Climate warming has led to shifts in the seasonal timing of species. These shifts can differ across trophic levels, and as a result, predator phenology can get out of synchrony with prey phenology. This can have major consequences for predators such as population declines owing to low reproductive success. However, such trophic interactions are likely to differ between habitats, resulting in differential susceptibility of populations to increases in spring temperatures. A mismatch between breeding phenology and food abundance might be mitigated by dietary changes, but few studies have investigated this phenomenon. Here, we present data on nestling diets of nine different populations of pied flycatchers Ficedula hypoleuca, across their breeding range. This species has been shown to adjust its breeding phenology to local climate change, but sometimes insufficiently relative to the phenology of their presumed major prey: Lepidoptera larvae. In spring, such larvae have a pronounced peak in oak habitats, but to a much lesser extent in coniferous and other deciduous habitats. 2. We found strong seasonal declines in the proportions of caterpillars in the diet only for oak habitats, and not for the other forest types. The seasonal decline in oak habitats was most strongly observed in warmer years, indicating that potential mismatches were stronger in warmer years. However, in coniferous and other habitats, no such effect of spring temperature was found. 3. Chicks reached somewhat higher weights in broods provided with higher proportions of caterpillars, supporting the notion that caterpillars are an important food source and that the temporal match with the caterpillar peak may represent an important component of reproductive success. 4. We suggest that pied flycatchers breeding in oak habitats have greater need to adjust timing of breeding to rising spring temperatures, because of the strong seasonality in their food. Such between-habitat differences can have important consequences for population dynamics and should be taken into account in studies on phenotypic plasticity and adaptation to climate change.
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