The purpose of the study was to examine the biomechanical-physiological effects of different frequencies using the double poling technique in cross-country skiing. Nine elite skiers roller-skied ...using poling frequencies of 40, 60 and 80 cycles·min
−1
(Pf
40,
Pf
60
, Pf
80
) at submaximal treadmill speeds (12, 18, 24 km·h
−1
). Cycle characteristics, pole forces, joint angles and physiological responses were measured. Comparing Pf
40
versus Pf
60
versus Pf
80
(all variables different at
P
< 0.05), absolute poling time decreased by up to 46%, as did absolute and relative (% cycle time) recovery times, at almost all speeds. Peak force, impulse of force and time to peak force decreased, whereas impact force increased with frequency at almost all speeds. Elbow ranges of motion and angular velocities, hip and knee angle maxima and flexion/extension ranges of motion per cycle decreased, whereas hip and knee angle minima, ranges of motion per minute and angular extension velocities during recovery phase all increased with frequency at nearly all speeds. Oxygen uptake and heart rate increased up to 13% (Pf
40–60
versus Pf
80
) at all speeds. Pulmonary ventilation increased most distinctly at the highest speed. Blood lactate was lowest at Pf
60
and highest at Pf
80
(J-shape curve) at 24 km·h
−1
. Gross efficiency decreased with higher frequency at all speeds. These results demonstrate different biomechanical and physiological demands at different frequencies with the beneficial effects of lower poling frequencies at submaximal speeds. For training purposes, we suggest that cross-country skiers would benefit by training with different poling frequencies to vary their training load.
This study aimed to 1) determine basic physiological demands during a simulated on-snow cross-country skiing (XCS) race when using grip-waxed skis (all classic XCS techniques CLASSIC), versus ...glide-waxed skis for exclusive double poling (DP) and 2) analyze in which track sections DP is different from CLASSIC under controlled gliding conditions in elite junior and senior skiers.
Nineteen male and female elite XC skiers performed 1) two randomized simulated XCS races over 5.3 km using DP or CLASSIC measuring section times, V˙O2, HR, blood lactate, and RPE; and 2) V˙O2peak tests using diagonal stride and DP on treadmill.
The total group showed no differences in performance or physiological responses between DP and CLASSIC. Elite male skiers achieved improved (~23 s, P < 0.05), male juniors equal (P > 0.05) and females worse (~43 s, P < 0.05) performance with DP versus CLASSIC. Flat and undulating terrain favored DP in men, whereas uphill favored CLASSIC in females (~60 s). Uphill sections showed the greatest group differences. Greater RPE was found in the arms during DP, whereas RPE was greater in the legs using CLASSIC. V˙O2peak in DP was ~95% of V˙O2max.
Male skiers demonstrated superior performance with exclusively using DP on a Fédération International de Ski regulation-compliant XCS track, whereas junior males achieved similar, and females' weaker performance using DP versus CLASSIC. The greatest potential in females is in uphill sections where they distinctly lose time. Exclusive DP might only be beneficial in athletes with high upper-body capacity, and double-pole-specific training and technique. To generalize the findings of the current study, further analysis of snow conditions and course topography is required.
Increases in physical (e.g., high-intensity running and sprinting), technical (e.g., passing rate), and tactical (e.g., player density) aspects made elite level soccer more challenging within the ...past years. The aim of the study was to evaluate whether these evolutions are also been reflected in changes in anthropometric and fitness characteristics between former (2002 to 2005) and current (2012 to 2015) elite Austrian youth development center (U13 to U14) and soccer academy (U15 to U18) players. A battery of anthropometric, general and soccer-specific fitness tests was conducted annually at the end of each year. Independent
-test and Cohen's
(ES) were calculated to compare the two four-year periods (2530 vs. 2611 players) at each age group separately. Current players were significantly faster in 20 m sprint (ES = 0.26-0.50) and reaction test (ES = 0.15-0.39, except for U18), but less flexible at sit-and-reach (ES = -0.19 to -0.55), in all age categories. Whereas height (ES = 0.26-0.32), body mass (ES = 0.11-0.18) and countermovement jump (ES = 0.24-0.26) increased significantly at youth development center level, current academy players performed superior at shuttle sprint (ES = 0.21-0.59), hurdles agility run (ES = 0.24-0.49), and endurance run (ES = 0.11-0.20). These changes over time in speed, change-of-direction ability, lower-body power, coordination, and endurance were attributed to modern training approaches (e.g., modified games and change-of-direction drills) and modifications in selection politics (e.g., coaches favor speed and decision-making skills).
The aim of this study was to identify performance‐determining factors in biathlon standing shooting in rest and after intense exercise. Eight Finnish national‐ and nine junior‐team biathletes ...participated in the study. Participants fired 40 resting shots (REST) and 2 × 5 competition simulation shots (LOAD) after 5 minutes of roller skiing at 95% of peak heart rate. Hit percentage, aiming point trajectory and postural balance were measured from each shot. Cleanness of triggering (ATV, movement of the aiming point 0‐0.2 second before the shot) and vertical stability of hold (DevY) were the most important components affecting shooting performance both in REST (DevY, R = −0.61, P < .01; ATV, R = −0.65, P < .01) and in LOAD (DevY, R = −0.50, P < .05; ATV, R = −0.77, P < .001). Postural balance, especially in shooting direction, was related to DevY and ATV. Stability of hold in horizontal (F(1,15) = 7.025, P < .05) and vertical (F(1,15) = 21.285, P < .001) directions, aiming accuracy (F(1,15) = 9.060, P < .01), and cleanness of triggering (F(1,15) = 59.584, P < .001) decreased from REST to LOAD, accompanied by a decrease in postural balance. National‐ and junior‐team biathletes differed only in hit percentage in REST (92 ± 8% vs 81 ± 8%, P < .05) and left leg postural balance in shooting direction in LOAD (0.31 ± 0.18 mm vs 0.52 ± 0.20 mm, P < .05), and the intense exercise affected the shooting technical components similarly in both national and junior groups. Biathletes should focus on cleanness of triggering and vertical stability of hold in order to improve biathlon standing shooting performance. More stable postural balance in shooting direction could help to improve these shooting technical components.
To identify biomechanical predictors that distinguish between high- and low-score athletes in biathlon shooting and to determine the relationships among these variables in field testing.
Twenty-two ...biathletes (8 female, 14 male) from the World Cup, the European Cup, and a federal youth squad each fired 3 clips of 5 shots in prone and standing shooting positions without physical load, followed by 2 respective series in both disciplines during a simulated 12.5-km pursuit race on roller skis. Biomechanical variables describing triggering, rifle force in the back shoulder, and body and rifle sway were calculated over the last 0.5 second before firing. For computed linear discriminant analyses, subjects were divided into high- and low-level performers based on mean scores for each condition separately. In addition, correlations among all biomechanical factors were calculated.
Regarding prone shooting, shoulder force in the rest condition and vertical rifle sway in the race simulation were shown to be main discriminators. Several body- and rifle-sway variables were found to be predictors in standing rest shooting. Body sway across the shooting line discriminated the groups in the standing race situation tendentially. Thus, the main performance predictors changed due to fatigue. Correlations between triggering and rifle sway, shoulder force and rifle sway, and body sway and rifle sway were discovered.
Referring to the current results, athletes are recommended to focus on vertical rifle sway in prone position and on body sway across the shooting line during standing shooting when fatigued.
Several methods could be used to measure the forces from skis or roller skis in cross-country skiing. Equipment that could measure medio-lateral forces may be of good help for investigating the ...relevant skating techniques. The aim of this study was to validate a pair of newly designed two-dimensional force measurement roller skis. The vertical and medio-lateral forces which were perpendicular to the body of the roller ski could be measured. Forces were resolved into the global coordinate system and compared with the force components measured by a force plate. A static and dynamic loading situation for the force measurement roller ski was performed to reveal the validity of the system. To demonstrate whether the force measurement roller ski would affect roller skiing performance on a treadmill, a maximum speed test with the V2 technique was performed by using both normal and force measurement roller skis. The force-time curves obtained by these two different force measurement systems were shown to have high similarity (coefficient of multiple correlations > 0.940). The absolute difference for the forces in the X and Z directions over one push-off cycle was 3.9−33.3 N. The extra weight (333 g) of the force measurement roller ski did not affect the performance of the skiers. Overall, the newly designed two-dimensional force measurement roller ski in this study is valid for use in future research during daily training for skate skiing techniques.
This study evaluated two approaches for estimating the total propulsive force on a skier's center of mass (COM) with double-poling (DP) and V2-skating (V2) skiing techniques. We also assessed the ...accuracy and the stability of each approach by changing the speed and the incline of the treadmill. A total of 10 cross-country skiers participated in this study. Force measurement bindings, pole force sensors, and an eight-camera Vicon system were used for data collection. The coefficient of multiple correlation (CMC) was calculated to evaluate the similarity between the force curves. Mean absolute force differences between the estimated values and the reference value were computed to evaluate the accuracy of each approach. In both DP and V2 techniques, the force-time curves of the forward component of the translational force were similar to the reference value (CMC: 0.832-0.936). The similarity between the force and time curves of the forward component of the ground reaction force (GRF) and the reference value was, however, greater (CMC: 0.879-0.955). Both approaches can estimate the trend of the force-time curve of the propulsive force properly. An approach by calculating the forward component of GRF is a more appropriate method due to a better accuracy.
Cross-country skiing (XCS) embraces a broad variety of techniques applied like a gear system according to external conditions, slope topography, and skier-related factors. The continuous detection of ...applied skiing techniques and cycle characteristics by application of unobtrusive sensor technology can provide useful information to enhance the quality of training and competition. (1) Background: We evaluated the possibility of using a high-precision kinematic global navigation satellite system (GNSS) to detect cross-country skiing classical style technique. (2) Methods: A world-class male XC skier was analyzed during a classical style 5.3-km time trial recorded with a high-precision kinematic GNSS attached to the skier's head. A video camera was mounted on the lumbar region of the skier to detect the type and number of cycles of each technique used during the entire time trial. Based on the GNSS trajectory, distinct patterns of head displacement (up-down head motion) for each classical technique (e.g., diagonal stride (DIA), double poling (DP), kick double poling (KDP), herringbone (HB), and downhill) were defined. The applied skiing technique, skiing duration, skiing distance, skiing speed, and cycle time within a technique and the number of cycles were visually analyzed using both the GNSS signal and the video data by independent persons. Distinct patterns for each technique were counted by two methods: Head displacement with course inclination and without course inclination (net up-down head motion). (3) Results: Within the time trial, 49.6% (6 min, 46 s) was DP, 18.7% (2 min, 33 s) DIA, 6.1% (50 s) KDP, 3.3% (27 s) HB, and 22.3% (3 min, 03 s) downhill with respect to total skiing time (13 min, 09 s). The %Match for both methods 1 and 2 (net head motion) was high: 99.2% and 102.4%, respectively, for DP; 101.7% and 95.9%, respectively, for DIA; 89.4% and 100.0%, respectively, for KDP; 86.0% and 96.5%, respectively, in HB; and 98.6% and 99.6%, respectively, in total. (4) Conclusions: Based on the results of our study, it is suggested that a high-precision kinematic GNSS can be applied for precise detection of the type of technique, and the number of cycles used, duration, skiing speed, skiing distance, and cycle time for each technique, during a classical style XCS race.
Double poling (DP) as a main technique in cross-country skiing has developed substantially over the last 15 yr. The purpose of the present study was to analyze the question, "How do modern elite ...skiers control DP speed?"
Twelve male elite cross-country skiers roller skied using DP at 9, 15, 21, and 27 km.h(-1) and maximum velocity (V(max)). Cycle characteristics, pole and plantar forces, and elbow, hip, and knee joint angles were analyzed.
Both poling frequency and cycle length increased up to 27 km.h (-1)(P < 0.05), with a further increase in poling frequency at V(max) (P < 0.05). Peak pole force, rate of force development, and rearfoot plantar force increased with submaximal velocities (V(sm)), whereas poling time and time-to-peak pole force gradually shortened (P < 0.05). Changes in elbow joint kinematics during the poling phase were characterized by a decreased angle minimum and an increased flexion and extension ranges of motion as well as angular velocities across V(sm) (P < 0.05), with no further changes at V(max). Hip and knee joint kinematics adapted across V(sm) by 1) decreasing angles at pole plant and angle minima during the poling phase, 2) increasing the ranges of motion and angular velocities during the flexion phases occurring around pole plant, and 3) increasing extension ranges of motion and angular velocities during the recovery phase (all P values <0.05), with no further changes at V(max).
Elite skiers control DP speed by increasing both poling frequency and cycle length; the latter is achieved by increased pole force despite reduced poling time. Adaptation to higher speeds was assisted by an increased range of motion, smaller angle minima, and higher angular velocities in the elbow, the hip, and the knee joints.
This study focused on resolving the differences in economy between two common sit-skiing postures used by disabled athletes, suspected to be the most and least effective. Ten experienced non-disabled ...male cross-country skiers went through an incremental testing protocol with an ergometer simulating double poling in two sitting postures "kneeing" and "knee-high." The protocol consisted of 3 × 4 min steady-state stages (13, 22, and 34% of maximal sprint power output). Subjects' respiratory gases and heart rate were measured and blood lactate concentrations were determined. In addition, pulling forces and motion capture recordings were collected. Oxygen consumption was 15.5% (
< 0.01) higher with "knee-high" compared to "kneeing" at stage three. At stage three cycle rate was 13.8% higher (
< 0.01) and impulse of force 13.0% (
< 0.05) and hip range of motion 46.6% lower (
< 0.01) with "knee-high" compared to "kneeing." "Kneeing" was found to be considerably more economical than "knee-high" especially at 34% of maximum sprint power output. This might have been due to higher cycle rate, lower impulse of force and smaller hip range of motion with "knee-high" compared to "kneeing." This indicates that sit-skiers should adopt, if possible, posture more resembling the "kneeing" than the "knee-high" posture. Combining such physiological and biomechanical measurements and to further develop them to integrated miniature wearable sensors could offer new possibilities for training and testing both in the laboratory and in the field conditions.
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