Thomas Stöggl

Analysis of a simulated sprint competition in classical cross country skiing

The objectives of this project were first to analyze the physiological response of a classical cross country (XC) skiing sprint competition, second, to examine the relationships of kinematic and physiological variables with sprint performance and third, to test the hypothesis that maximal speed in double poling (DP) and diagonal stride (DIAG) predicts sprint performance. Twelve elite skiers performed a treadmill‐based simulation of a sprint competition that included two maximal speed tests (DP, DIAG), a test and three sprint heats over a 3.5‐h period. VO2, lactate, heart rate (HR) and kinematic variables were measured. Maximal DP and DIAG speed, the level of repeatedly produced lactate values and skiing technical aspects positively correlated with sprint performance. Fastest skiers produced longer cycle lengths in all techniques at equal poling frequency. VO2 variables showed no correlation to sprint performance. VO2, tidal volume (VT), and lactate decreased over the heats. XC‐sprint performance in classical style depends on speed abilities, technique use, fatigue resistance, and anaerobic capacity. The relationship of maximal speed with sprint performance suggests (a) integrating maximal speed tests in XC sprint diagnostics and (b) emphasizing training models for XC skiing‐specific speed abilities to improve performance in XC skiing sprint.

Short and long term adaptation of variability during walking using unstable (Mbt) shoes

BACKGROUND The purpose of the study was to compare the variability of biomechanical variables during treadmill walking using unstable shoes (Masai Barefoot Technology, MBT, Roggwil, Switzerland) and conventional shoes, before and after a 10 week (wk) training period. METHODS Cycle characteristics, plantar pressure distribution, whole body 3D kinematics, and electromyographic signals of selected leg muscles during ground contact were recorded on 12 Sport Science students while walking on a treadmill with both conventional and unstable shoes before and after a 10 wk training intervention. The intervention consisted of more than 4h use of unstable shoes during daily activity. The standard deviation of 15 consecutive cycles in each analyzed variable was taken as the measure for variability. FINDINGS The main pattern was marked by a 35% (SD 10%) higher variability with the unstable shoes at pretest when compared with the conventional shoes, but decreased 30% (SD 12%) (both P<0.05) during the training intervention to almost equal variability in between the two shoe situations. This was especially true with regard to variables representing within gait characteristics (peak foot force, joint angles, etc.), whereas in variables describing the overall gait cycle (e.g. cycle rate, impulse of total force, etc.) no difference between MBT and conventional shoes at pre and post tests were found. INTERPRETATION The current study supports the idea that the unstable shoe serves as a motor constraint applicable during everyday activity, provoking increased variability during walking. In addition, a decrease in movement variability on the MBT shoes during the training intervention to the level of conventional shoes was observed.

General strength and kinetics: fundamental to sprinting faster in cross country skiing?

To determine relationships between general strength, maximal skiing speed (Vmax), pole and leg kinetics and kinematics, 16 male elite skiers underwent three Vmax tests in 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 Vmax were technique dependent. Power output in bench press and bench pull were related to Vmax in DP and diagonal stride, whereas each 1 repetition maximum was related to V2. Isometric squats were not associated with Vmax in all three techniques, whereas jump height and rate of force development during squat 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 Vmax when compared with the slower skiers. General strength and power 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.

Kinematic Determinants and Physiological Response of Cross-Country Skiing at Maximal Speed

PURPOSE The scope of the study was to a) transfer the maximal anaerobic running test (MART) to a treadmill-based cross-country roller skiing test protocol for skating and classic style, b) analyze the development and determinants of kinematic and physiological parameters from submaximal to maximal skiing speeds, c) analyze the effects of fatigue on skiing technique, and d) test the hypotheses that maximal skiing speed is related to cycle length and that the fastest skiers show shorter thrust combined with longer swing phases. METHODS Up to 24 elite skiers performed MART tests in double poling, diagonal stride and V2 skating, with roller skis on a treadmill. Anthropometrics, blood lactate, HR, and kinematics were determined. RESULTS When compared with former studies, faster skiing speeds of up to 34% were reported. Skiers improved speed by increasing cycle rate while trying to maintain cycle length. In the diagonal stride and V2 skating at maximal skiing speeds, skiers used contrary technical strategies to maintain the speed, whereas in double poling, a tendency toward an optimum in cycle length and cycle rate was established. Duration for the pole thrusts was around 180 ms for V2 skating and 210 ms for double poling. Highest relation to performance was found for the duration of the swing phases of arms and legs. CONCLUSIONS The increase in skiing speed and cycle length, compared with former studies and the positive relation between swing phase duration, stresses the importance of effective thrust phases within a short period. Therefore, it is recommended to increase the proportion of training aimed at the improvement of specific explosive strength and maximal power to increase the impulse of force.

Relationships between body composition, body dimensions, and peak speed in cross-country sprint skiing

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 body composition and/or body dimension characterizes a successful sprint skier. Our hypothesis was that body height and lean body 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: r = 0.77, P < 0.01; diagonal stride: r = 0.60, P < 0.05) and was the 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 (r = 0.75, P < 0.01), body mass index (r = 0.66, P < 0.01), total lean mass (r = 0.69, P < 0.01), and body mass (r = 0.57, P < 0.05) were positively related to double poling peak speed. Total lean mass (absolute: r = 0.58, P < 0.05; relative: r = 0.76, P < 0.001) and relative lean mass of the trunk, arms (both r = 0.72, P < 0.01), and legs (r = 0.54, P < 0.05) 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.

Polarized training has greater impact on key endurance variables than threshold, high intensity, or high volume training

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.

Biomechanical comparison of the double-push technique and the conventional skate skiing technique in cross-country sprint skiing

Abstract The aims of the study were to: (1) adapt the “double-push” technique from inline skating to cross-country skiing; (2) compare this new skiing technique with the conventional skate skiing cross-country technique; and (3) test the hypothesis that the double-push technique improves skiing speed in a short sprint. 13 elite skiers performed maximum-speed sprints over 100 m using the double-push skate skiing technique and using the conventional “V2” skate skiing technique. Pole and plantar forces, knee angle, cycle characteristics, and electromyography of nine lower body muscles were analysed. We found that the double-push technique could be successfully transferred to cross-country skiing, and that this new technique is faster than the conventional skate skiing technique. The double-push technique was 2.9 ± 2.2% faster (P < 0.001), which corresponds to a time advantage of 0.41 ± 0.31 s over 100 m. The double-push technique had a longer cycle length and a lower cycle rate, and it was characterized by higher muscle activity, higher knee extension amplitudes and velocities, and higher peak foot forces, especially in the first phase of the push-off. Also, the foot was more loaded laterally in the double-push technique than in the conventional skate skiing technique.

Lower extremity joint loading during level walking with Masai barefoot technology shoes in overweight males

The purpose of this study was to evaluate the effects of Masai barefoot technology (MBT) shoes on lower extremity joint loading in overweight males during level walking. Therefore, lower extremity kinematics, kinetics, and muscle electromyographic signals of the vastus lateralis (VL), biceps femoris (BF), and gastrocnemius medialis (GM) were recorded in 10 overweight males at a self‐chosen walking speed with MBT shoes and conventional shoes. Selected peak joint moments, maximal joint force loading rates, mean muscle intensities, and co‐activation indices of the VL/BF, as well as of the VL/GM were analyzed and compared for the two shoe conditions using paired Students t‐tests (α=0.05). Results showed that walking with MBT shoes reduced first peak knee adduction moments in overweight subjects. During midstance and terminal stance, increases in VL/GM co‐activation, accompanied by increases in VL and GM (only terminal stance) intensities were found for the MBT situation. Kinetic variables analyzed to assess ankle and hip joint loading did not exhibit any statistical differences. These results suggest that using MBT shoes diminishes medial compartment loads at the knee without overloading hip or ankle joints in overweight males. However, the additional muscle loading should not be overlooked, and warrants further investigation.

Biomechanical pole and leg characteristics during uphill diagonal roller skiing

Diagonal skiing as a major classical technique has hardly been investigated over the last two decades, although technique and racing velocities have developed substantially. The aims of the present study were to 1) analyse pole and leg kinetics and kinematics during submaximal uphill diagonal roller skiing and 2) identify biomechanical factors related to performance. Twelve elite skiers performed a time to exhaustion (performance) test on a treadmill. Joint kinematics and pole/plantar forces were recorded separately during diagonal roller skiing (9°; 11 km/h). Performance was correlated to cycle length (r = 0.77; P < 0.05), relative leg swing (r = 0.71), and gliding time (r = 0.74), hip flexion range of motion (ROM) during swing (r = 0.73) and knee extension ROM during gliding (r = 0.71). Push-off demonstrated performance correlations for impulse of leg force (r = 0.84), relative duration (r = − 0.76) and knee flexion (r = 0.73) and extension ROM (r = 0.74). Relative time to peak pole force was associated with performance (r = 0.73). In summary, diagonal roller skiing performance was linked to 1) longer cycle length, 2) greater impulse of force during a shorter push-off with larger flexion/extension ROMs in leg joints, 3) longer leg swing, and 4) later peak pole force, demonstrating the major key characteristics to be emphasised in training.

Force interaction and 3D pole movement in double poling

The aim of this study was to analyze double poling using combined kinetic and 3D kinematic analysis at high skiing speeds as regards pole force components, pole angles and pole behavior during the poling and swing phase. The hypothesis was that a horizontal pole force is more predictive for maximal skiing speed (Vmax) than the resultant pole force. Sixteen elite skiers performed a double‐poling Vmax test while treadmill roller skiing. Pole forces and 3D kinematics of pole movement at a speed of 30 km/h were analyzed and related to Vmax. The duration of the “preparation phase” showed the strongest relationship with Vmax (r=0.87, P<0.001). Faster skiers generated longer cycle lengths with longer swing and poling times, had less inclined pole angles at pole plant and a later peak pole force. Horizontal pole forces were not more highly related to Vmax compared with the resultant pole force. Impact force was not related to Vmax. At high skiing speeds, skiers should aim to combine high pole forces with appropriate timing of pole forces and appropriate pole and body positions during the swing and poling phase. The emphasis in training should be on the development of specific strength capacities for pole force production and the utilization of these capacities in double‐poling training sessions.