| 1. |
- Tinmark, Fredrik, et al.
(författare)
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Elite golfers' kinematic sequence in full-swing and partial-swing shots
- 2010
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Ingår i: SPORT BIOMECH. - : Informa UK Limited. - 1476-3141 .- 1752-6116. ; 9:4, s. 236-244
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate whether kinematic proximal-to-distal sequencing (PDS) and speed-summation are common characteristics of both partial and full-swing shots in golf players of different skill levels and genders. A total of 45 golfers participated, 11 male tournament professionals, 21 male and 13 female elite amateurs. They performed partial shots with a wedge to targets at three submaximal distances, 40, 55 and 70m, and full-swing shots with a 5 iron and a driver for maximal distance. Pelvis, upper torso and hand movements were recorded in 3D with an electromagnetic tracking system (Polhemus Liberty) at 240Hz and the magnitude of the resultant angular velocity vector of each segment was computed. The results showed a significant proximal-to-distal temporal relationship and a concomitant successive increase in maximum (peak) segment angular speed in every shot condition for both genders and levels of expertise. A proximal-to-distal utilization of interaction torques is indicated. Using a common PDS movement strategy in partial and full-swing golf shots appears beneficial from mechanical and control points of view and could serve the purpose of providing both high speed and accuracy.
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| 2. |
- Andersson, Erik, et al.
(författare)
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The effects of skiing velocity on mechanical aspects of diagonal cross-country skiing
- 2014
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Ingår i: Sports Biomechanics. - : Informa UK Limited. - 1476-3141 .- 1752-6116. ; 13:3, s. 267-284
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Göpfert, Caroline, et al.
(författare)
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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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Ingår i: Sports Biomechanics. - : Informa UK Limited. - 1476-3141 .- 1752-6116. ; 12:2, s. 154-174
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Mikkola, Jussi, et al.
(författare)
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Changes in performance and poling kinetics during cross-country sprint skiing competition using the double-poling technique
- 2013
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Ingår i: Sports Biomechanics. - : Routledge. - 1476-3141 .- 1752-6116. ; 12:4, s. 355-364
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Tidskriftsartikel (refereegranskat)abstract
- In this study, changes in skiing performance and poling kinetics during a simulated cross-country sprint skiing competition were investigated. Twelve elite male cross-country skiers performed simulated sprint competition (4 × 1,150 m heat with 20 min recovery between the heats) using the double-poling technique. Vertical and horizontal pole forces and cycle characteristics were measured using a force plate system (20-m long) during the starting spurt, racing speed, and finishing spurt of each heat. Moreover, heat and 20-m phase velocities were determined. Vertical and horizontal pole impulses as well as mean cycle length were calculated. The velocities of heats decreased by 2.7 ± 1.7% (p = 0.003) over the simulated competition. The 20-m spurting velocity decreased by 16 ± 5% (p < 0.002) and poling time increased by 18 ± 9% (p < 0.003) in spurt phases within heats. Vertical and horizontal poling impulses did not change significantly during the simulation; however, the mean forces decreased (p < 0.039) (vertical by 24 ± 11% and horizontal by 20 ± 10%) within heats but not between the heats. Decreased heat velocities over the simulated sprint and spurting velocities within heats indicated fatigue among the skiers. Fatigue was also manifested by decreased pole force production and increased poling time.
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| 5. |
- Sommer, Marius, 1974-, et al.
(författare)
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Synchronized metronome training induces changes in the kinematic properties of the golf swing
- 2014
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Ingår i: Sports Biomechanics. - : Taylor & Francis Group. - 1476-3141 .- 1752-6116. ; 13:1, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to evaluate possible effects of synchronized metronome training (SMT) on movement dynamics during golf swing performance, as captured by kinematic analysis. A one-group, between-test design was applied on thirteen male golfers (27.5 ± 4.6 years old, 12.7 ± 4.9 golf handicap) who completed twelve sessions of SMT over a four week period. Pre- and post-assessments of golf swings made with three different clubs (4-iron, 7-ironand pitching wedge) were performed using a three-dimensional motion capture system. Club peak velocity at three different swing phases andcross-correlation analysis of time-series signals were made on joint couplings(wrist-elbow-shoulder) of both arms, and between joints and the club, during the full golf swing. There were significantly higher cross-correlations between joint-couplings and concomitant changes of the associated phase-shift differences, as well as reduced phase-shift variability at post-test. No significant effect of SMT was found for the club peak velocities. We suggest that domain-general influences of SMT on the underlying brain-based motorcontrol strategies lead to a more coordinated movement pattern of the golf swing performance, which may explain previous observations of significantly improved golf shot accuracy and decreased variability after SMT.
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| 6. |
- Stöggl, Thomas, et al.
(författare)
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Mechanical behaviour of cross-country ski racing poles during double poling
- 2013
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Ingår i: Sports Biomechanics. - : Informa UK Limited. - 1476-3141 .- 1752-6116. ; 12:4, s. 365-380
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Tidskriftsartikel (refereegranskat)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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