Cross-country (XC) ski races involve a variety of formats, two different techniques and tracks with highly variable topography and environmental conditions. In addition, XC skiing is a major component of both Nordic combined and biathlon competitions. Research in this area, both in the laboratory and field, encounters certain difficulties that may reduce the reliability and validity of the data obtained, as well as complicate comparisons between studies. Here, 13 international experts propose specific guidelines designed to enhance the quality of research and publications on XC skiing, as well as on the biathlon and Nordic combined skiing. We consider biomechanical (kinematic, kinetic and neuromuscular) and physiological methodology (at the systemic and/or muscle level), providing recommendations for standardization/control of the experimental setup. We describe the types of measuring equipment and technology that are most suitable in this context. Moreover, we also deal with certain aspects of nomenclature of the classical and skating sub-techniques. In addition to enhancing the quality of studies on XC skiing, Nordic combined and biathlon, our guidelines should also be of value for sport scientists and coaches in other disciplines where physiological and/or biomechanical measurements are performed in the laboratory and/or outdoors.
The Tour de Ski (TDS: 6–9 sprint and distance races across 9–11 days) represents the most intense competition series of the cross-country (XC) ski season and is characterized by accumulated stress from consecutive days of high-intensity (~ 85%–160% VO2 max) racing, travel, cold temperatures and low to moderate altitude (500–1500 m above sea level). Here, nutritional strategies play a key supportive role for optimized health, recovery and performance. This narrative review aims to provide an evidence-based discussion on the energetic demands of the TDS and recommendations for nutritional strategies to optimize health and performance of XC skiers during and following the TDS. We highlight several challenges that may arise during the TDS, including the following: poor energy availability (EA) due to decreased appetite or a pressure to maintain a low body weight, suboptimal carbohydrate availability due to a failure to replenish muscle glycogen stores across consecutive-day racing and increased risk of illness due to a combination of factors, including high-intensity racing, poor nutrition, sleep, travel and hygiene. We encourage XC skiers to maintain optimal overall EA across the ~ 1.5-week period, ensure high daily carbohydrate availability, as well as the use of strategies to maintain a healthy immune system. In addition, we include practical guidelines on the management of nutrition support prior to and during the TDS. We recognize that many nutritional questions remain unanswered both in the context of elite XC ski racing and specifically for extreme demands like the TDS that should be addressed in future investigations.
The present review deals with the current scientific knowledge related with ski jump landing. A specific focus is given on the landing biomechanics, the methods utilized for its analysis and the injuries connected to the landing phase. Despite the demonstrated importance for the safety and the performance of ski jumpers, the landing and its preparation are rarely investigated. In this paper, after having firstly described the execution of landing and its preparation and the reason why is important to analyze it, an overview of the current status of the research related to the landing biomechanics is reported (kinetics, kinematics, electromyographic activation, aerodynamics, computer simulation). The third part describes the methods and technologies utilized in literature to analyze the landing and its preparation (video cameras, inertial sensors, force insoles, wind tunnel and computer simulation). After that, an overview of the injuries related to landing is reported. The final section proposes future research in the field of biomechanics of ski jump landing in different fields, such as computer simulations, kinematic analysis, equipment development and biomechanics of female athletes.
Although reliable feedback is crucial to improving the performance of competitive alpine skiers, the coach's eye may not be sensitive enough to detect small, but highly significant “mistakes”. Monitoring of the performance of alpine ski racers by inertial motion units (IMU) has proven to be of value in this context and here we summarize practical and methodological aspects of this approach. Methodologically, the IMUs employed should combine high sampling frequencies with minimal signal drift. The sensors should be positioned to sense the movement of the bones in a given body segment while being protected as much as possible against impact with the ski gates. The data obtained, often synchronized with input from Global Satellite Navigation Systems (GNSS), are usually refined utilizing advanced biomechanical models and other computerized approaches. In practice, the combination of inertial sensors and GNSS allows accurate monitoring of skiing kinematics (technique) and the movement of the skier’s center-of-mass, also allowing analysis of both whole-body vibrations (WBV) and loss of mechanical energy. Presentation of the findings to coaches and athletes can be facilitated by synchronizing them with video recordings. Recent advances in IMU technology, including miniaturization, wireless communication, direct storage of data in the cloud, and processing with artificial intelligence may allow these sensors, in-combination with GNSS, to become real-time virtual alpine ski coaches, perhaps the next step in the development of this sport.
At the 2022 Winter Olympics in Beijing, the XC skiing, biathlon and nordic combined events will be held at altitudes of ~ 1700 m above sea level, possibly in cold environmental conditions and while requiring adjustment to several time zones. However, the ongoing COVID-19 pandemic may lead to sub-optimal preparations. The current commentary provides the following evidence-based recommendations for the Olympic preparations: make sure to have extensive experience of training (> 60 days annually) and competition at or above the altitude of competition (~ 1700 m), to optimize and individualize your strategies for acclimatization and competition. In preparing for the Olympics, 10–14 days at ~ 1700 m seems to optimize performance at this altitude effectively. An alternative strategy involves two–three weeks of training at > 2000 m, followed by 7–10 days of tapering off at ~ 1700 m. During each of the last 3 or 4 days prior to departure, shift your sleeping and eating schedule by 0.5–1 h towards the time zone in Beijing. In addition, we recommend that you arrive in Beijing one day earlier for each hour change in time zone, followed by appropriate timing of exposure to daylight, meals, social contacts, and naps, in combination with a gradual increase in training load. Optimize your own individual procedures for warming-up, as well as for maintaining body temperature during the period between the warm-up and competition, effective treatment of asthma (if necessary) and pacing at ~ 1700 m with cold ambient temperatures. Although we hope that these recommendations will be helpful in preparing for the Beijing Olympics in 2022, there is a clear need for more solid evidence gained through new sophisticated experiments and observational studies.
To analyze the inter-limb coordination patterns and energy recovery of elite cross-country skiers performing double poling (DP).
Thirty-three elite athletes in three track sections of FIS-WC races, with different slopes (2°, 0° and − 1.5°). Stereo vision capture system (50 Hz cameras) and 3D analysis were used to extract: kinematic parameters (center of gravity, velocity); joint angles and angular velocities; energy (potential and kinetic) and energy recovery indices R% and R(t) during the entire DP cycle and within poling (R pol) and swing phase (R swi).
Average race velocity of the centre of gravity (V ave) significantly varied according to slopes (5.4, 7.3 and 8.3 m/s). This correlated with differences in the angular velocities of the most relevant joints. Elbow flexion angular velocity in the early portion of poling phase was higher according to the slope variations (− 137, − 171 and − 202 deg/s, for the slopes 2°, 0° and − 1.5°, respectively), indicating the possible modulation of muscular stretch shortening cycle (SSC). A similar trend was observed for shoulder angular velocity which increased during poling phase, and for knee extension velocity during swing phase, and for knee extension velocity during swing phase. R% decreased significantly for the − 1.5° slope (32% and 24% vs. 15%); R(t) was higher for the R swi. Significant differences were observed in trunk-elbow, trunk-shoulder, trunk-knee and elbow-shoulder patterns for the − 1.5° slope with respect to the others.
Despite the modest variation of the track’s slope, the effects on propulsion and recovery strategies were different.
To biomechanically profile force generation connected to the complex role of the trunk in double poling in a representative sample of Para-Nordic sit-skiers.
Twelve male World Cup Para-Nordic sit-skiers (sport classes: LW10–12) were skiing on flat snow terrain at submaximal speed of 4.5 m/s (~ 73% maximum speed). 2D video (50 Hz) and pole force analyses (1000 Hz) were performed synchronously, examining angle, force and cycle characteristics to analyse the role of the trunk in generating propulsion.
LW10–11.5 skiers lost between 21% and 4% propulsive force versus LW12 athletes only due to different geometrics of the trunk and pole angle at an equal axial pole force. While LW10–11 skiers indicated trunk extension or position maintenance during pole thrust, LW11.5–12 skiers showed strong trunk flexion combined with smaller pole angles to the ground. Hence, LW11.5–12 skiers could create larger propulsive forces and therefore greater cycle lengths at lower cycle rates at the same speed. Maximum speed increased from LW10 to LW12 and was significantly correlated to trunk flexion range of motion (r = 0.63) and cycle length (r = 0.59). Trunk flexion ROM showed a significant relationship to the impulse of propulsive force (r = 0.63) and pole angle to the ground (r = − 0.76) (all P < 0.05).
The impact of impairment on the force production profiles and its physiological-biomechanical consequences need further investigation also in other terrains and at wider spectrums of skiing speeds. The evident problem of low numbers of LW10–11 skiers in World Cup needs creative future solutions for research.
The purpose was to investigate whether an increased amount of training while carrying the rifle affects skiing in well-trained biathletes at submaximal and maximal workloads during a pre-season period lasting a minimum of 12 weeks.
Seventeen well-trained biathletes (9 females, 8 males) were assigned to an intervention (IG, n = 10) or control (CG, n = 7) group. Before (T1) and after (T2) the training intervention all participants performed, using treadmill roller-skiing, a submaximal test without the rifle on one day and two submaximal workloads and a maximal time trial (TT) with the rifle on a subsequent day. Between T1 and T2 all participants performed a minimum of 12 weeks of normal training, the only difference between groups being that IG performed more of their training sessions carrying the rifle.
IG performed more training compared to CG (15.4 ± 1.1 vs. 11.2 ± 2.6 h/week, P < 0.05), including a higher amount of training with the rifle (3.1 ± 0.6 vs. 1.1 ± 0.3 h/week, P < 0.001). Speed at 4 mmol/L of blood lactate increased significantly for CG from T1 to T2 (P = 0.028), while only tended to increase for IG (P = 0.058). Performance during the TT, VO2max and the aerobic metabolic rate increased significantly from T1 to T2, although the differences disappeared when including the speed at baseline as a covariate.
According to the present results, increasing training while carrying the rifle by 2 h/week does not appear to improve skiing performance in well-trained biathletes. In addition, physiological markers at submaximal and maximal intensities while carrying the rifle were not affected after the training intervention.
The aim of the present study was to evaluate the trunk strength capacity of alpine ski racers aged 10–18 years, who were tested during the last 15 years, to identify reference values for trunk flexor to extensor strength ratios according to age and sex.
In total, 2841 participants (1605 males, 1236 females; 10–18 years) were included, who were pupils of a famous skiing-specific secondary modern school or members of the provincial ski team between 2006 and 2020. The maximum isometric trunk flexion and extension strength was measured using the slightly modified Back Check. Sex-specific differences were assessed with Student’s t test or Mann–Whitney-U test. Univariate analyses of variance or Kruskal–Wallis-H tests were used to assess differences between age groups. Descriptive sex- and age-specific reference values were calculated (norm area: mean ± ½ standard deviation).
Sex-specific differences were found for both flexion (starting at 11 years) and extension strength (starting at 12 years) (P < 0.001). Lower flexion to extension strength ratios were identified for males (0.89 ± 0.18) compared with females (0.82 ± 0.15), but the ratios remained constant across age groups for both sexes.
The present study provides age- and sex-specific reference values for trunk flexion to extension strength ratios for 10- to 18-year old youth and adolescent ski racers. The data of the present study represent a large data pool of youth ski racers at a high-performance level; thus, coaches can use the reference values for comparing the ratios of their athletes.
Wide skis are the most popular ski sold in the United States and are skied routinely in all types of terrain, especially by young skiers. This study investigated the influence of slalom (SL, 64 mm underfoot width) and wide skis (WS, 97.7 mm underfoot width) on perceptual responses, timed performance, edge inclination angles, and EMG in young alpine ski racers. Thirteen subjects, mean age 12.8 ± 0.5 years, completed one run on each of two courses which were set to approximate the different turning radii of each ski. They completed a Likert-type questionnaire to assess components of self-efficacy after each run. EMG activity was recorded on the gluteus medius (GM), vastus lateralis, tibialis anterior and peroneus longus (PL). Perceptions of confidence, aggressiveness, speed, and skiing on line were significantly greater, by about 31%, for SL than WS regardless of course. Turn times were significantly less by 4% for SL than WS, peak edge inclination angle was 7% greater for SL than WS, and PL activity was 40% less for SL compared to WS. Young racers are developing skills to improve their racing techniques and are still forming technique strategies to deal with the many factors present in skiing which may disrupt learning progressions. With lower perceptual and performance responses on WS, young ski racers who ski on groomed snow with WS could be interfering with the adaptation of fundamental racing technique at a critical time in their development.