| 1. |
- Stöggl, Thomas, et al.
(author)
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Automatic classification of the Sub-Techniques (Gears) used in cross-country ski skating employing a mobile phone
- 2014
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In: Sensors. - : MDPI AG. - 1424-8220. ; 14:11, s. 20589-20601
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Journal article (peer-reviewed)abstract
- The purpose of the current study was to develop and validate an automatic algorithm for classification of cross-country (XC) ski-skating gears (G) using Smartphone accelerometer data. Eleven XC skiers (seven men, four women) with regional-to-international levels of performance carried out roller skiing trials on a treadmill using fixed gears (G2left, G2right, G3, G4left, G4right) and a 950-m trial using different speeds and inclines, applying gears and sides as they normally would. Gear classification by the Smartphone (on the chest) and based on video recordings were compared. Formachine-learning, a collective database was compared to individual data. The Smartphone application identified the trials with fixed gears correctly in all cases. In the 950-m trial, participants executed 140 ± 22 cycles as assessed by video analysis, with the automatic Smartphone application giving a similar value. Based on collective data, gears were identified correctly 86.0% ± 8.9% of the time, a value that rose to 90.3% ± 4.1% (P < 0.01) with machine learning from individual data. Classification was most often incorrect during transition between gears, especially to or from G3. Identification was most often correct for skiers who made relatively few transitions between gears. The accuracy of the automatic procedure for identifying G2left, G2right, G3, G4left and G4right was 96%, 90%, 81%, 88% and 94%, respectively. The algorithm identified gears correctly 100% of the time when a single gear was used and 90% of the time when different gears were employed during a variable protocol. This algorithm could be improved with respect to identification of transitions between gears or the side employed within a given gear.
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| 2. |
- Andersson, Erik, et al.
(author)
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Analysis of sprint cross-country skiing using a differential global navigation satellite system
- 2010
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 110:3, s. 585-595
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Journal article (peer-reviewed)abstract
- The purpose was to examine skiing velocities, gear choice (G2-7) and cycle rates during a skating sprint time trial (STT) and their relationships to performance, as well as to examine relationships between aerobic power, body composition and maximal skiing velocity versus STT performance. Nine male elite cross-country skiers performed three tests on snow: (1) Maximum velocity test (Vmax) performed using G3 skating, (2) Vmax test performed using double poling (DP) technique and (3) a STT over 1,425 m. Additional measurements of VO2max during roller skiing and body composition using iDXA were made. Differential global navigation satellite system data were used for position and velocity and synchronized with video during STT. The STT encompassed a large velocity range (2.9-12.9 m s-1) and multiple transitions (21-34) between skiing gears. Skiing velocity in the uphill sections was related to gear selection between G2 and G3. STT performance was most strongly correlated to uphill time (r = 0.92, P < 0.05), the percentage use of G2 (r = -0.72, P < 0.05), and DP Vmax (r = -0.71, P < 0.05). The velocity decrease in the uphills from lap 1 to lap 2 was correlated with VO2max (r = -0.78, P < 0.05). Vmax in DP and G3 were related to percent of racing time using G3. In conclusion, the sprint skiing performance was mainly related to uphill performance, greater use of the G3 technique, and higher DP and G3 maximum velocities. Additionally, VO2max was related to the ability to maintain racing velocity in the uphills and lean body mass was related to starting velocity and DP maximal speed.
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| 3. |
- Andersson, Erik, 1984-, et al.
(author)
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Biomechanical analysis of the herringbone technique as employed by elite cross-country skiers
- 2014
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In: Scandinavian Journal of Medicine and Science in Sports. - : Wiley-Blackwell. - 0905-7188 .- 1600-0838. ; 24:3, s. 542-552
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Journal article (peer-reviewed)abstract
- This investigation was designed to analyse the kinematics and kinetics of cross-country skiing at different velocities with the herringbone technique on a steep incline. Eleven elite male cross-country skiers performed this technique at maximal, high, and moderate velocities on a snow-covered 15° incline. They positioned their skis laterally (25 to 30°) with a slight inside tilt and planted their poles laterally (8 to 12°) with most leg thrust force exerted on the inside forefoot. Although 77% of the total propulsive force was generated by the legs, the ratio between propulsive and total force was approximately fourfold higher for the poles. The cycle rate increased with velocity (1.20 to 1.60 Hz), whereas the cycle length increased from moderate up to high velocity, but then remained the same at maximal velocity (2.0 to 2.3 m). In conclusion, with the herringbone technique, the skis were angled laterally without gliding, with the forces distributed mainly on the inside forefoot to enable grip for propulsion. The skiers utilized high cycle rates with major propulsion by the legs, highlighting the importance of high peak and rapid generation of leg forces.
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| 4. |
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| 5. |
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| 6. |
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| 7. |
- Andersson, Erik, et al.
(author)
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The effects of skiing velocity on mechanical aspects of diagonal cross-country skiing
- 2014
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In: Sports Biomechanics. - : Informa UK Limited. - 1476-3141 .- 1752-6116. ; 13:3, s. 267-284
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Journal article (peer-reviewed)abstract
- Cycle and force characteristics were examined in 11 elite male cross-country skiers using the diagonal stride technique while skiing uphill (7.5 degrees) on snow at moderate (3.5 +/- 0.3m/s), high (4.5 +/- 0.4m/s), and maximal (5.6 +/- 0.6m/s) velocities. Video analysis (50Hz) was combined with plantar (leg) force (100Hz), pole force (1,500Hz), and photocell measurements. Both cycle rate and cycle length increased from moderate to high velocity, while cycle rate increased and cycle length decreased at maximal compared to high velocity. The kick time decreased 26% from moderate to maximal velocity, reaching 0.14s at maximal. The relative kick and gliding times were only altered at maximal velocity, where these were longer and shorter, respectively. The rate of force development increased with higher velocity. At maximal velocity, sprint-specialists were 14% faster than distance-specialists due to greater cycle rate, peak leg force, and rate of leg force development. In conclusion, large peak leg forces were applied rapidly across all velocities and the shorter relative gliding and longer relative kick phases at maximal velocity allow maintenance of kick duration for force generation. These results emphasise the importance of rapid leg force generation in diagonal skiing.
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| 8. |
- Björklund, Glenn, 1972-, et al.
(author)
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Biomechanical influenced differences in O2 extraction in diagonal skiing: arm versus leg
- 2010
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In: Medicine & Science in Sports & Exercise. - : Lippincott Williams & Wilkins. - 0195-9131 .- 1530-0315. ; 42:10, s. 1899-1908
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Journal article (peer-reviewed)abstract
- Biomechanically Influenced Differences in O-2 Extraction in Diagonal Skiing: Arm versus Leg. Med. Sci. Sports Exerc., Vol. 42, No. 10, pp. 1899-1908, 2010. Purpose: This study aimed to determine whether the differences in oxygen extraction and lactate concentration in arms and legs during cross-country skiing are related to muscle activation or force production and how these differences are influenced by a reduction in exercise intensity. Methods: Nine well-trained male cross-country skiers (age = 22 +/- 3 yr, (V) over dotO(2max) = 5.3 +/- 0.3 L.min(-1) and 69 +/- 3 mL.kg(-1).min(-1)) performed diagonal skiing on a treadmill for 3 min at 90% followed by 6 min at 70% of (V) over dotO(2max). During the final minute of each workload, arterial, femoral, and subclavian venous blood was collected for determination of blood gases, pH, and lactate. EMG was recorded from six upper-and lower-body muscles, and leg and pole forces were measured. Cardiorespiratory variables were monitored continuously. Results: Oxygen extraction in the legs was higher than that in the arms at both 90% and 70% of (V) over dotO(2max) (92% +/- 3% vs 85% +/- 6%, P < 0.05 and 90% +/- 3% vs 78% +/- 8%, P < 0.001). This reduction with decreased workload was more pronounced in the arms (-9.8% +/- 7.7% vs -3.2% +/- 3.2%, P < 0.01). EMGRMS for the arms was higher, and pole ground contact time was greater than the corresponding values for the legs (both P < 0.01). At both intensities, the blood lactate concentration was higher in the subclavian than that in the femoral vein but was lowered more in the subclavian vein when intensity was reduced (all P < 0.001). Conclusions: The higher muscle activation (percentage of maximal voluntary isometric contraction) in the arms and the longer ground contact time of the poles than the legs contribute to the lower oxygen extraction and elevated blood lactate concentration in the arms in diagonal skiing. The better lactate recovery in the arms than that in the legs is aided by greater reductions in muscle activation and pole force when exercise intensity is reduced.
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| 9. |
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| 10. |
- Göpfert, Caroline, et al.
(author)
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Biomechanical characteristics and speed adaptation during kick double poling on roller skis in elite cross-country skiers
- 2013
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In: Sports Biomechanics. - : Informa UK Limited. - 1476-3141 .- 1752-6116. ; 12:2, s. 154-174
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Journal article (peer-reviewed)abstract
- Recent developments in cross-country ski racing should promote the use of kick double poling. This technique, however, has not been the focus in athletes' training and has barely been investigated. The aims of the present study were to develop a function-based phase definition and to analyse speed adaptation mechanisms for kick double poling in elite cross-country skiers. Joint kinematics and pole/plantar forces were recorded in 10 athletes while performing kick double poling at three submaximal roller skiing speeds. A speed increase was associated with increases in cycle length and rate, while absolute poling and leg push-off durations shortened. Despite maintained impulses of force, the peak and average pole/leg forces increased. During double poling and leg push-off, ranges of motion of elbow flexion and extension increased (p < 0.05) and were maintained for hip/knee flexion and extension. Cycle length increase was correlated to increases in average poling force (r = 0.71) and arm swing time (r = 0.88; both p < 0.05). The main speed adaptation was achieved by changes in double poling technique; however, leg push-off showed high variability among elite skiers, thus illustrating important aspects for technique training.
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| 11. |
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| 12. |
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| 13. |
- Soehnlein, Quirin, et al.
(author)
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THE EFFECT OF 16-WEEK PLYOMETRIC TRAINING ON EXPLOSIVE ACTIONS IN EARLY TO MID-PUBERTY ELITE SOCCER PLAYERS
- 2014
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In: Journal of Strength and Conditioning Research. - 1064-8011 .- 1533-4287. ; 28:8, s. 2105-2114
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Journal article (peer-reviewed)abstract
- Plyometric training (PT) programs are widely used to improve explosive actions in soccer players of various ages, although there is debate about optimal training duration and time course of improvement. Twenty-two early to mid-puberty elite soccer players were assigned to a control group (CG, n = 10, regular soccer training) or a plyometric training group (PTG, n = 12, regular soccer training substituted with 2 PT sessions each week). Both groups trained for 16 weeks during the in-season period. Control group performed only tests at baseline and after intervention, whereas PTG performed additional tests after 4, 8, and 12 weeks. During each test, subjects' performances in speed (10 and 30 m; 5 and 20 m), agility, shuttle run, multiple 5 bounds (MB5), and standing long jump (LJ) were recorded. The PTG showed improved performance in 20-m sprint time (-3.2%), agility time (-6.1%), MB5 distance (+11.8%), and LJ distance (+7.3%) (all, p <= 0.05) after 16 weeks. All these improvements were higher compared with CG (all, p <= 0.05). The time course of improvement in the PT group showed that 20-m sprint time improved after 16 weeks (p = 0.012); agility after 4 (p = 0.047) and 8 weeks (p = 0.004) but stopped after 12 weeks (p = 0.007); MB5 after 8 (p = 0.039), 12 (p = 0.028), and 16 weeks (p < 0.001); and LJ improved after 4 (p = 0.045), 12 (p = 0.008), and 16 weeks (p < 0.001). Plyometric training seems to be an appropriate training tool to enhance some but not all explosive actions. The results indicate that the duration of a PT program is highly dependent on what type of explosive actions should be improved, or whether several explosive actions should be improved at the same time.
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| 14. |
- Stöggl, Thomas, 1977-, et al.
(author)
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Biomechanical determinants of oxygen extraction during cross-country skiing
- 2013
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In: Scandinavian Journal of Medicine and Science in Sports. - : Wiley. - 0905-7188 .- 1600-0838. ; 23:1, s. e9-e20
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Journal article (peer-reviewed)abstract
- To determine the relationship of muscle activation, force production, and cycle characteristics to O2 extraction during high- and lower-intensity double poling (DP), nine well-trained male cross-country skiers performed DP on a treadmill for 3 min at 90% VO2peak followed by 6 min at 70%. During the final minute at each workload, arterial, femoral, and subclavian venous blood were collected for determination of partial pressure of O2, partial pressure of CO2, pH, and lactate. Electromyography (EMG) was recorded from six upper and lower body muscles, leg and pole forces were measured, and cardiorespiratory variables were monitored continuously. O2 extraction was associated with time point of peak pole force (PFpeak), duration of recovery, EMG activity, and lower body use. Arm O2 extraction was lower than in the legs at both intensities (P < 0.001) and was reduced to a lesser extent upon decreasing the workload (P < 0.05). Arm root-mean-square EMG was higher during the poling phase and entire cycle compared with the legs (P < 0.001). Blood lactate was higher in the subclavian than in femoral vein and artery (P < 0.001) and independent of intensity. O2 extraction was correlated to low muscle activation, later PFpeak, prolonged poling time, and extensive dynamic lower body use. Cycle rate and recovery time were associated with O2 extraction during high-intensity exercise only.
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| 15. |
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| 16. |
- Stöggl, Thomas, et al.
(author)
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Do Anthropometrics, Biomechanics, and Laterality Explain V1 Side Preference in Skiers?
- 2013
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In: Medicine & Science in Sports & Exercise. - 0195-9131 .- 1530-0315. ; 45:8, s. 1569-1576
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Journal article (peer-reviewed)abstract
- PURPOSE: In cross-country (XC) skiing, the V1 and V2 alternate skate techniques are asymmetric, and skiers can choose either the right or left side for pole support. The overall purpose of this study was to investigate V1 side preference in elite XC skiers, notably by documenting V1 skate side preference, dominant and nondominant V1peak speeds, left- to right-side differences (ΔL-R) in laboratory-based measurements, and relationships between side preference data. METHODS: Sixteen male elite XC skiers completed one incremental speed test using V1 on their dominant side and another incremental speed test using V1 on their nondominant side while roller-skiing on a treadmill. During these tests, V1peak speed, pole forces, and plantar forces were measured. A whole-body dual-energy x-ray absortiometry (DXA) scan measured anthropometric parameters and questionnaires established side preference for V2 alternate, overall laterality in XC skiing, handedness, footedness, and injury prevalence. RESULTS: Left-to-right V1 side preference was equally distributed among skiers. V1peak speed was approximately 4.5% greater on the dominant versus nondominant sides. V1peak Δ L-R were positively related to Δ L-R in V1-dominant peak pole forces only. Questionnaire data indicated that more skiers preferred V2 alternate right, with moderate correlations between preferred V1 and V2 alternate sides. The expression of a dominant side in V1 and V2 alternate increased as skiing speed increased from moderate to 15-km endurance-race to sprint-race speeds. However, no relationships were established between V1 or V2 side preference and handedness, footedness, or number of one-sided injuries. CONCLUSIONS: ΔL-R in measurements provide limited explanations for V1 side preferences in elite XC skiers. In fact, no systematic relations exist between V1 side preferences and anthropometric, biomechanical, or questionnaire data. Copyright © 2013 by the American College of Sports Medicine.
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| 17. |
- Stöggl, Thomas, et al.
(author)
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General strength and kinetics: fundamental to sprinting faster in cross country skiing?
- 2011
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In: Scandinavian Journal of Medicine and Science in Sports. - : Wiley. - 0905-7188 .- 1600-0838. ; 21:6, s. 791-803
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Journal article (peer-reviewed)abstract
- To determine relationships between general strength, maximal skiing speed (16 male elite skiers underwent three double poling, diagonal stride and V2 on a treadmill. The analyzed skiing speeds and leg and arm kinetics were among the highest ever recorded. Relationships between general strength exercises and Power output in bench press and bench pull were related to maximum was related to V2. Isometric squats were not associated with height and rate of force development during squat jump Vmax), pole and leg kinetics and kinematics,Vmax tests inVmax were technique dependent.Vmax in DP and diagonal stride, whereas each 1 repetitionVmax in all three techniques, whereas jump were. Analysis of kinetics and kinematics revealed that it was not exclusively the magnitude of applied forces during skiing, but the timing and proper instant of force application were major factors discriminating between faster and slower skiers. For all techniques, the faster skiers used different skiing strategies when approaching with the slower skiers. General strength and power Vmax when compared per se seem not to be major determinants of performance in elite skiers, whereas coordination of these capacities within the different and complex skiing movements seems to be the discriminating factor.
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| 18. |
- Stöggl, Thomas, et al.
(author)
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Magnitude and variation in muscle activity and kinematics during walking before and after a 10-week adaptation period using unstable (MBT) shoes
- 2012
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In: Footwear Science. - : Informa UK Limited. - 1942-4280 .- 1942-4299. ; 4:2, s. 131-143
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Journal article (peer-reviewed)abstract
- Objectives: The purpose of this study was to compare the magnitude and variability of electromyographic (EMG) and kinematic variables during treadmill walking using unstable (Masai Barefoot Technology, MBT) shoes and conventional shoes, before and after a 10-week training period.Methods: Twelve Sport Science students were analysed while walking on a treadmill with both conventional and unstable shoes, before and after a 10-week training intervention consisting of more than 4 h of use of unstable shoes during daily activity. Cycle characteristics, plantar pressure distribution, whole-body three-dimensional (3D) kinematics and EMG signals of selected leg muscles during the entire gait cycle and its subphases were recorded. The coefficient of variation of 20 consecutive cycles in each variable analysed was taken as the measure of variability.Results: A trend towards higher variability but equal magnitude was observed with MBT shoes compared with conventional shoes at the pre-intervention test (pre-test) regarding kinematic and EMG variables. The training period led to interaction effects (p < 0.05 to 0.01) demonstrating a global attenuation in the variability of kinematic and EMG variables in both shoe conditions, with greater reduction in the MBT situation, or an increase in variability with conventional shoes to higher post-test variability compared with MBT. Both situations revealed equal cycle times ( 1.05 s) but a shortened duration of loading response (136 vs. 146 ms) and terminal stance (211 vs. 223 ms) and an increased duration of midstance (293 vs. 282 ms) and swing time (408 vs. 386 ms) when comparing MBT with conventional shoes (all p<0.05 to 0.001). Training led to a global reduction in cycle time (p<0.05) and ground contact time (p<0.01) in both shoe conditions.Conclusions: The results support the idea that the unstable shoe serves as a motor constraint applicable during everyday activity, inducing changes in the gait pattern with both MBT and conventional shoes. In selected EMG and kinematic variables, an interaction effect towards a greater decrease in movement variability in MBT compared with conventional shoes or an increase in variability with conventional shoes towards a higher post-test variability compared with MBT was observed. © 2012 Copyright Taylor and Francis Group, LLC.
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| 19. |
- Stöggl, Thomas, et al.
(author)
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Mechanical behaviour of cross-country ski racing poles during double poling
- 2013
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In: Sports Biomechanics. - : Informa UK Limited. - 1476-3141 .- 1752-6116. ; 12:4, s. 365-380
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Journal article (peer-reviewed)abstract
- The purpose of this study was to evaluate the behaviour of cross-country ski poles during double poling on a treadmill using three-dimensional kinematics. The results were compared with standard laboratory tests of the pole manufacturers. A total of 18 skiers were analysed at two speeds (85% and 95% of the maximal speed) at grades of 1.5% and 7%. Variables describing cycle characteristics, bending stiffness, bending behaviour, and trajectories of the pole markers were analysed. Triangular-shaped poles demonstrated the greatest stiffness and lowest variability in maximal bending. Softer poles demonstrated greater variability in bending behaviour and lost ground contact at high skiing speeds, which for some skiers resulted in failure to complete high-speed tests. Considerable variations in pole behaviour for similar poles between skiers were observed, which might be attributed to differences in technique, indicating that mechanical properties of the poles did not exclusively determine pole behaviour in the dynamic situation. The greatest magnitude of pole bending was in the middle part of the pole, which differed from the standard static pole analysis of the manufacturer. Increases in grade demonstrated the greatest effect on pole bending. Distinct differences from the pole manufacturers' laboratory measures were apparent, suggesting that basic pole testing might be adapted.
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| 20. |
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| 21. |
- Stöggl, Thomas, et al.
(author)
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Polarized training has greater impact on key endurance variables than threshold, high intensity, or high volume training
- 2014
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In: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 5, s. Art. no. 33-
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Journal article (peer-reviewed)abstract
- Endurance athletes integrate four conditioning concepts in their training programs: high-volume training (HVT), "threshold-training" (THR), high-intensity interval training (HIIT) and a combination of these aforementioned concepts known as polarized training (POL). The purpose of this study was to explore which of these four training concepts provides the greatest response on key components of endurance performance in well-trained endurance athletes. Methods: Forty eight runners, cyclists, triathletes, and cross-country skiers (peak oxygen uptake: (VO2peak): 62.6 ± 7.1 mL·min-1·kg-1) were randomly assigned to one of four groups performing over 9 weeks. An incremental test, work economy and a VO2peak tests were performed. Training intensity was heart rate controlled. Results: POL demonstrated the greatest increase in VO2peak (+6.8 ml·min·kg-1 or 11.7%, P < 0.001), time to exhaustion during the ramp protocol (+17.4%, P < 0.001) and peak velocity/power (+5.1%, P < 0.01). Velocity/power at 4 mmol·L-1 increased after POL (+8.1%, P < 0.01) and HIIT (+5.6%, P < 0.05). No differences in pre- to post-changes of work economy were found between the groups. Body mass was reduced by 3.7% (P < 0.001) following HIIT, with no changes in the other groups. With the exception of slight improvements in work economy in THR, both HVT and THR had no further effects on measured variables of endurance performance (P > 0.05). Conclusion: POL resulted in the greatest improvements in most key variables of endurance performance in well-trained endurance athletes. THR or HVT did not lead to further improvements in performance related variables. © 2014 Stöggl and Sperlich.
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| 22. |
- Stöggl, Thomas, et al.
(author)
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Relationships between body composition, body dimensions, and peak speed in cross-country sprint skiing
- 2010
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In: Journal of Sports Sciences. - : Routledge, Travel & Francis group. - 0264-0414 .- 1466-447X. ; 28:2, s. 161-169
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Journal article (peer-reviewed)abstract
- In modern sprint cross-country skiing, strength and maximal speed are major determinants of performance. The aims of this study were to ascertain the anthropometric characteristics of world-class sprint skiers and to evaluate whether a specific bodycomposition and/or body dimension characterizes a successful sprint skier. Our hypothesis was that body height and leanbody mass are related to peak speed in double poling and diagonal stride. Fourteen male national and international elite skiers performed two peak speed tests in double poling and diagonal stride roller skiing on a treadmill and were analysed using dual-energy X-ray absorptiometry to determine body composition and body dimensions. Relative pole length was positively correlated with both techniques (double poling: only variable that was part of the multiple regression model for both double poling and diagonal stride peak speed. Body height was not correlated with any technique, whereas lean trunk mass (r¼0.77, P50.01; diagonal stride: r¼0.60, P50.05) and was ther¼0.75, P50.01), body mass index (r¼0.66, Ppeak speed. Total lean mass (absolute:arms (both conclusion, skiers should aim to achieve a body composition with a high percentage of lean mass and low fat mass. A focus on trunk mass through increased muscle mass appears to be important, especially for double poling. The use of longer poles (percent body height) seems to be advantageous for both double poling and diagonal stride peak speed, whereas body dimensions do not appear to be a predictive factor.50.01), total lean mass (r¼0.69, P50.01), and body mass (r¼0.57, P50.05) were positively related to double polingr¼0.58, P50.05; relative: r¼0.76, P50.001) and relative lean mass of the trunk,r¼0.72, P50.01), and legs (r¼0.54, P50.05) were positively related to diagonal stride peak speed. In conclusion, skiers should aim to achieve a body composition with a high percentage of lean mass and low fat mass. A focus on trunk mass through increased muscle mass appears to be important, especially for double poling. The use of longer poles (percent body height) seems to be advantageous for both double poling and diagonal stride peak speed, whereas body dimensions do not appear to be a predictive factor.
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| 23. |
- Stöggl, Thomas, et al.
(author)
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Repeated high intensity bouts with long recovery : Are bicarbonate or carbohydrate supplements an option?
- 2014
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In: Scientific World Journal. - : Hindawi Limited. - 2356-6140 .- 1537-744X. ; , s. Art. no. 145747-
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Journal article (peer-reviewed)abstract
- The effects of varying recovery modes and the influence of preexercise sodium bicarbonate and carbohydrate ingestion on repeated high intensity performance, acid-base response, and recovery were analyzed in 12 well-trained males. They completed three repeated high intensity running bouts to exhaustion with intervening recovery periods of 25 min under the following conditions: sodium bicarbonate, active recovery (BIC); carbohydrate ingestion, active recovery (CHO); placebo ingestion, active recovery (ACTIVE); placebo ingestion, passive recovery (PASSIVE). Blood lactate (BLa), blood gases, heart rate, and time to exhaustion were collected. The three high intensity bouts had a duration of 138 ± 9, 124 ± 6, and 121 ± 6 s demonstrating a decrease from bout 1 to bout 3. Supplementation strategy had no effect on performance in the first bout, even with differences in pH and bicarbonate (HC O 3 -). Repeated sprint performance was not affected by supplementation strategy when compared to ACTIVE, while PASSIVE resulted in a more pronounced decrease in performance compared with all other interventions. BIC led to greater BLa, pH, and HC O 3 - values compared with all other interventions, while for PASSIVE the opposite was found. BLa recovery was lowest in PASSIVE; recovery in pH, and HC O 3 - was lower in PASSIVE and higher in BIC.
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| 24. |
- Swarén, Mikael, 1980-
(author)
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Experimental test setups and simulations in skiing mechanics
- 2014
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Licentiate thesis (other academic/artistic)abstract
- Product testing and development are essential parts in sports and for the athletes in their quest to reach the podium. Manufacturers of sports equipment often use basic test methods which do not test the equipment in a sports specific way. Much of the equipment used by world-class athletes is chosen based only on subjective tests and the athletes’ feelings. One short term aim was therefore to develop test methods for objective tests of sports equipment that also tested the equipment in a sports specific way. Another aim was to integrate mechanics and simulations to enhance the understanding of the test results. The more long term aims are to contribute to increased theoretical knowledge regarding test methods for sports equipment and to contribute to the development of test methods to create new and better sports equipment. Experimental tests combined with simulations can give valuable information to improve the performance and safety of sports equipment. Three studies dealt with the issue of objective yet sport specific test methods for sports equipment. The main methodological advancement is the modification of established test methods together with conventional mechanics calculations. New test devices and methodologies are proposed for alpine ski helmets and cross-country ski poles. Suggestions are given for improved test setups as well as theoretical simulation are introduced for glide tests of skis. The results show how sport specific test methodologies together with theoretical calculations can improve the objectiveness and relevance when testing sports equipment. However, the collected and used data require high precision to obtain high accuracy in the simulations. High data accuracy can be an issue in field measurements but also due to manufacturers not disclosing key material data. Still, the used methods and calculations in this thesis produce relevant and reliable results which can be implemented to accurate evaluations of different sports equipment. Even though it has not been a first priority aim in this work, the results from the alpine helmet study have been used by helmet manufacturers to design new helmets with increased safety properties. This further show how an objective and sport specific test approach together with theoretical simulation can improve sports equipment and in the longer perspective, also the athletes’ performances.
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