A method for measuring the forces between the shoe and ski and upon the pole has been developed. Instrumented skis and poles are used with a portable data acquisition system that is carried by the skier in the field. Elite, top-level collegiate, and citizen skiers were used as subjects. Skiers performed the diagonal stride, and a marathon skate. Axial force levels at the forefoot were found to reach 164%, and 120% of body weight in the diagonal skate strides, respectively.
Javin C. Pierce, Malcolm H. Pope, Per Renstrom, Robert J. Johnson, Janet Dufek and Charles Dillman
Øyvind Sandbakk and Hans-Christer Holmberg
Cross-country (XC) skiing has been an Olympic event since the first Winter Games in Chamonix, France, in 1924. Due to more effective training and tremendous improvements in equipment and track preparation, the speed of Olympic XC-ski races has increased more than that of any other Olympic endurance sport. Moreover, pursuit, mass-start, and sprint races have been introduced. Indeed, 10 of the 12 current Olympic competitions in XC skiing involve mass starts, in which tactics play a major role and the outcome is often decided in the final sprint. Accordingly, reappraisal of the success factors for performance in this context is required. The very high aerobic capacity (VO2max) of many of today’s world-class skiers is similar that of their predecessors. At the same time, the new events provide more opportunities to profit from anaerobic capacity, upper-body power, high-speed techniques, and “tactical flexibility.” The wide range of speeds and slopes involved in XC skiing requires skiers to continuously alternate between and adapt different subtechniques during a race. This technical complexity places a premium on efficiency. The relative amounts of endurance training performed at different levels of intensity have remained essentially constant during the past 4 decades. However, in preparation for the Sochi Olympics in 2014, XC skiers are performing more endurance training on roller skis on competition-specific terrain, placing greater focus on upper-body power and more systematically performing strength training and skiing at high speeds than previously.
Gerald A. Smith, Jon B. Fewster and Steven M. Braudt
Olympic skiers in the women's 30-km race were analyzed as they double poled on a moderate downhill slope. Movement patterns of 20 skiers were analyzed 10 from a top finishing group and 10 from slower finishers in the bottom third of the field. Skiers in the faster group not only were faster overall in the race but were faster as they double poled through the site (6.75 vs. 6.43 m/s). Cycle length was significantly correlated with cycle velocity (r = .81). Trunk flexion and shoulder extension during poling were similar between groups; however, considerable variability of shoulder positioning was noted for both groups of skiers. Distinct shoulder-elbow-pole positioning differences were noted among skiers. Disadvantageous positionin» of the shoulder at the beginning of poling was related to poorer pole inclination during elbow extension. While many skiers in both fast and slow groups double poled with good positioning, others would benefit from greater shoulder flexion to maximize double poling performance.
Robert W. Norman and Paavo V. Komi
The purpose of this study was to determine whether world class skiers were alike in their mechanical power outputs (normalized for body mass and velocity and called mechanical cost, MTC) and body segment energy transfers when skiing in competition on level and uphill terrain using the diagonal technique. Eleven competitors were analyzed from film taken during a 15-km World Championship race on a level (1.6°) and uphill (9.0°) section of the course. Metabolic rates were estimated from assumptions concerning the efficiencies of positive and negative work and calculations, from the film, of the mechanical power produced by the skiers. The results showed that skiing on the slope was 2.2 times more demanding mechanically than skiing on a level track (MTC of 4.0 vs. 1.8 J • kg−1 • m−1, respectively). Skiers who had high MTC had low energy transfers (r = −0.9). Even in this presumably homogeneous group of elite skiers there were large individual differences in MTC and other mechanical variables, suggesting technique problems for some. Furthermore, on flat terrain the estimated metabolic rate was only about 76% of an MV02 of 80 ml • kg−1 • min−1. This suggests that speed, using the diagonal stride, may be limited by constraints on body segment utilization and not by the physiological energy delivery system of these highly trained athletes.
Harri Luchsinger, Jan Kocbach, Gertjan Ettema and Øyvind Sandbakk
Biathlon is an Olympic sport combining cross-country skiing with the skating technique and rifle shooting. Biathletes carry a 3.5-kg-long rifle around the ski tracks and stop at the shooting range to perform 5 shots in the prone or standing position between the 2.5- to 5.0-km laps. In the biathlon
Nicolas Berryman, Iñigo Mujika, Denis Arvisais, Marie Roubeix, Carl Binet and Laurent Bosquet
described as a percentage of VO 2 max or maximal heart rate. 3 , 4 In recent years, however, convincing evidence has emerged indicating that strength training may also have a positive impact on middle- and long-distance performance (running, cycling, cross-country skiing) and its key determinants for
Kevin Boldt, Anthony Killick and Walter Herzog
A 1:1 locomotion–respiration entrainment is observed in galloping quadrupeds, and is thought to improve running economy. However, this has not been tested directly in animals, as animals cannot voluntarily disrupt this entrainment. The purpose of this study was to evaluate metabolic economy in a human gait involving all four limbs, cross-country skiing, in natural entrainment and forced nonentrainment. Nine elite cross-country skiers roller skied at constant speed using the 2-skate technique. In the first and last conditions, athletes used the natural entrained breathing pattern: inhaling with arm recovery and exhaling with arm propulsion, and in the second condition, the athletes disentrained their breathing pattern. The rate of oxygen uptake (VO2) and metabolic rate (MR) were measured via expired gas analysis. Propulsive forces were measured with instrumented skis and poles. VO2 and MR increased by 4% and 5% respectively when skiers used the disentrained compared with the entrained breathing pattern. There were no differences in ski or pole forces or in timing of the gait cycle between conditions. We conclude that breathing entrainment reduces metabolic cost of cross-country skiing by approximately 4%. Further, this reduction is likely a result of the entrainment rather than alterations in gait mechanics.
Nicolas Fabre, Stéphane Perrey, Loïc Arbez and Jean-Denis Rouillon
This study aimed (1) to determine whether paced breathing (synchronization of the expiration phase with poling time) would reduce the metabolic rate and dictate a lower rate of perceived exertion (RPE) than does spontaneous breathing and (2) to analyze the effects of paced breathing on poling forces and stride-mechanics organization during roller-ski skating exercises.
Thirteen well-trained cross-country skiers performed 8 submaximal roller-skiing exercises on a motorized driven treadmill with 4 modes of skiing (2 skating techniques, V2 and V2A, at 2 exercise intensities) by using 2 patterns of breathing (unconscious vs conscious). Poling forces and stride-mechanics organization were measured with a transducer mounted in ski poles. Oxygen uptake (VO2) was continuously collected. After each bout of exercise RPE was assessed by the subject.
No difference was observed for VO2 between spontaneous and paced breathing conditions, although RPE was lower with paced breathing (P < .05). Upper-limb cycle time and recovery time were significantly (P < .05) increased by paced breathing during V2A regardless of the exercise intensity, but no changes for poling time were observed. A slight trend of increased peak force with paced breathing was observed (P = .055).
The lack of a marked effect of paced breathing on VO2 and some biomechanical variables could be explained by the extensive experience of our subjects in cross-country skiing.
Øyvind Sandbakk, Silvana Bucher Sandbakk, Matej Supej and Hans-Christer Holmberg
This study examined the influence of turn radius on velocity and energy profiles when skidding and step turning during more and less effective downhill turns while cross-country skiing. Thirteen elite female cross-country skiers performed single turns with a 9- or 12-m radius using the skidding technique and a 12- or 15-m radius with step turning. Mechanical parameters were monitored using a real-time kinematic Global Navigation Satellite System and video analysis. Step turning was more effective during all phases of a turn, leading to higher velocities than skidding (P < .05). With both techniques, a greater radius was associated with higher velocity (P < .05), but the quality of turning, as assessed on the basis of energy characteristics, was the same. More effective skidding turns involved more pronounced deceleration early in the turn and maintenance of higher velocity thereafter, while more effective step turning involved lower energy dissipation during the latter half of the turn. In conclusion, the single-turn analysis employed here reveals differences in the various techniques chosen by elite cross-country skiers when executing downhill turns of varying radii and can be used to assess the quality of such turns.
Maria Heikkilä, Raisa Valve, Mikko Lehtovirta and Mikael Fogelholm
–20 years old. The three main sports among the participants were cross-country skiing ( n = 53 coaches and n = 111 athletes), orienteering ( n = 13 and n = 110), and biathlon ( n = 6 and n = 38). Other sports were endurance running and racewalking, triathlon, cycling, swimming, rowing, and canoeing