Self-reported obstructive airway symptoms are common in young cross-country skiers

The reported high use of anti-asthmatic drugs in cross-country skiers prompted a study to assess the prevalence of self-reported asthma, asthma-associated symptoms and the use of anti-asthmatic medication among cross-country skiers. A self-administered questionnaire based on the Medical Research Council questionnaire was answered by cross-country skiers in the Swedish national ski team, in upper secondary school ski-classes and in the Swedish army ( n =305). Controls ( n =141) were pupils from regular classes in the same upper secondary schools. Skiers more often gave posi- tive answers to all questions on asthma and asthma-associated symptoms. The cumulative prevalence of asthma was 15% in skiers and 6% in controls. We conclude that the common use of anti-asthmatic drugs among cross-country skiers reflects a high prevalence of self-reported asthma and asthma-associated symptoms. The causes of these differences are un-known.     

Back injuries and pain in adolescents attending a ski high school

This study compared overuse injuries, small abnormalities, and pain alone in different types of skiing and activity levels. Subjects were 45 ski high school athletes aged 15–19 years. We found the back and knees significantly more prone to activity-related injuries and pain than other body regions. Thirty subjects (67%) had low back pain on the first examination, and 17 had pain caused by overuse of the back. This was more frequent among active, young competitive boys in the cross-country skiing group, with mature height less than 99%, than among noncompetitive boys in the same group or among the alpine skiers. Neck pain was reported only by girls. Eight subjects had low back pain related to small abnormalities. The subjects were given counseling about training and physiotherapy. The 1-year follow-up found a significant reduction in back pain due to overuse injuries (from 17 to 3 subjects) and indistinct neck pain (from 10 to 2) but no reduction in pain in those with small abnormalities in the low back. Low back pain was common in young athletes, particularly in cross-country skiers. Excessively rapid progression of training and faulty technique increased back pain complaints from 36% when entering the school to 67% at the first examination. A proper evaluation and treatment of overuse injuries and accurate counseling of training types, volume, and progression reduced the low back pain problems to 29% of subjects 1 year later in spite of a maintained high activity level. A minimum entrance requirement to conditioning seems mandatory for students attending a ski high school.     

Cross-country skiing injuries and biomechanics

Cross-country skiing exercises most of the joints, muscles and tendons in the body giving the skier an all around workout. This, in combination with a low incidence of injury, makes cross-country skiing an ideal recreational and competitive sport. The new skating techniques developed during the last decade have resulted in greater velocity. The maximum speed during the diagonal stride technique is 6 m/sec compared to 8 to 9 m/sec when skating and double poling. Top-level skiers today use strong and ultra light skis of fiberglass and graphite. The ski weight is less than 500g. Today's skating technique does not require any waxing and only the cambered portion of the ski is waxed when performing the diagonal stride. The preparation of the ski course has improved with the development of special track machines. This allows top-level skiers to reach 60 to 80 km/h on downhill slopes, which has resulted in an increased risk of injury. Because cross-country skiing takes place wherever snow is available, it is difficult to establish accurate injury rates in comparison to alpine skiing which is performed on very specialised terrain at ski areas. Studies estimate the cross-country ski injury rate in Sweden to be around 0.2 to 0.5 per thousand skier days. A prospective study of cross-country ski injuries conducted in Vermont revealed an injury rate of 0.72 per thousand skier days. 75% of the injuries sustained by members of the Swedish national cross-country ski team during 1983 and 1984 were overuse injuries while 25% resulted from trauma. The most common overuse injuries included medial-tibial stress syndrome, Achilles tendon problems and lower back pain. Most common among traumatic injuries were ankle ligament sprains and fractures, muscle ruptures, and knee ligament sprains. Shoulder dislocation, acromioclavicular separation and rotator cuff tears are not infrequent in cross-country skiing. Injuries to the ulnar collateral ligament of the metacarpal phalangeal joint of the thumb (Stener's lesion) is the most common ski injury involving the upper extremity. Cross-country skiers 16 to 21 years of age complained more frequently of mild lower back pain than similarly aged non-skiers. This may result from repetitive hyperextension motions during the kick phase and the recurring spinal flexion and extension during the double poling phase. Repeated slipping on hard and icy tracks infrequently produce partial tears or microtrauma in the muscle tendinous units of the groin.(ABSTRACT TRUNCATED AT 400 WORDS)     

Low back pain in elite cross-country skiers

Low back pain is a common complaint among competitive cross-country skiers. Fifty-three top male and 34 female skiers in the age group 16–25 were interviewed with a questionnaire regarding anthropometric parameters, training variables, back pain and other injuries. The frequency of back pain was 64% in the whole group, men affected slightly more often than women. Back pain was defined as previous or present recurrent skiing correlated backache that more or less affected skiing ability. Diagonal skiing style was the most commonly back pain-inducing style, whereas no skier experienced back pain when "skating" only. The low back was the predominant location of pain. Anthropometric and training variables seemed to be of little value in predicting back pain.     

Upper body power comparison between groups of cross-country skiers and runners.

The purpose of this study was to evaluate relationships between upper body power (UBP) and cross-country ski skating race velocity (R) in a cross sectional representation of cross-country skiers. Additionally, cross-country skiers' UBP was compared to UBP of distance runners. Participants (n = 195) were tested on a Street Arm Ergometer for UBP using a ramped maximal UBP test simulating a double poling motion. A strong relationship (r = 0.89) between UBP and RV in skiers was determined. High school skiers were separated into slow and fast groups based on reported RV; significant differences (p < 0.05) in both UBP was found to be an effective partial predictor of RV, independent of gender. Mean UBP for the cross-country runners was 46% of mean UBP for the cross-country skiers. With UBP contributing so much to performance in cross-country ski racing, it is recommended that cross-country skiers focus a large portion of their training on the specific development of that fitness component.     

Energy cost of free technique and classical cross-country skiing at racing speeds

PURPOSE: First, to measure the O(2) uptake ([OV0312]O(2)) and the blood lactate concentration during cross-country skiing at competition speed. Second, to compare these entities for the free technique and the classical technique. Further, to establish the subjects' [OV0312]O(2max) and the [OV0312]O(2) corresponding to the onset of blood lactate accumulation (OBLA, 4 mmol.L-1) during skiing, and finally to relate these entities to those of treadmill running. METHODS: Five high-level female junior cross-country skiers with a mean [OV0312]O(2max) of 63 mL.kg-1.min-1 served as subjects in five tests: examination of the [OV0312]O(2max) and the [OV0312]O(2) corresponding to the OBLA during up-hill cross-country skiing (both styles), inclined treadmill running, and a 6-km simulated cross-country ski race (both styles). RESULTS: The [OV0312]O(2max) obtained during up-hill cross-country skiing did not differ from that during treadmill running, nor did it differ between the two skiing styles. The peak heart rate was significantly lower during uphill cross-country skiing than during treadmill running. During the simulated competitions, the [OV0312]O(2) averaged 84% of the [OV0312]O(2max) or 95% of the [OV0312]O(2) at the OBLA found for uphill skiing. CONCLUSION: High-level female junior cross-country skiers are unable to ski at intensities close to their [OV0312]O(2max) or maintain an average intensity above that corresponding to their OBLA even during races lasting less than 25 min. Thus, training at intensities around the OBLA may be particularly relevant for cross-country skiers.     

Influence of body mass on cross-country ski racing performance.

The influence of body mass on cross-country skiing performance was evaluated by (i) a theoretical analysis of the relationship between body mass (M) and on one hand the maximal aerobic power and on the other the power expense of skiing, (ii) timing skiers in varied terrain during ski racing, (iii) comparing racing success between light and heavy skiers, and (iv) relating maximal aerobic power of skiers and power expense of skiing to body mass. The theoretical analysis indicated that the maximal aerobic power scaled with M2/3, while the mass exponent for the power expenses ranged from 1/3 to 1. The net result was that heavy skiers appear to be favored in all types of terrain but the steep uphills. During ski racing, heavy skiers displayed a tendency to be faster in all types of terrain, although no statistically significant effect was found. The racing success tended to be greater in heavy skiers among males but not among females. During skiing, maximal aerobic power and the power expense of skiing scaled with M0.7 and M0.4, respectively, indicating an advantage for the heavy skier. Altogether, these observations indicate that heavy skiers are favored, but also that other factors are more important than body mass for cross-country ski racing performance.     

Effect of skiing speed on ski and pole forces in cross-country skiing

PURPOSE: The present study characterized pole and ski forces in classical technique cross-country skiing. Eight elite junior cross-country skiers performed diagonal skiing at 65%, 75%, 90%, and 100% of maximum speed on a stable 100-m-low uphill (2.5 degrees ). METHOD:: The ski and the pole forces (vertical (Fz) and horizontal (Fy) directions) on the right and left sides were recorded separately when the skier skied over a special custom-made force platform system placed at the end of the uphill course. The entire system consisted of four separate 20-m-long rows of 1-m-long force plates connected in series, row by row. RESULTS: When the forces were averaged for the various functional phases of skiing cycle, the ski Fz during the gliding phase decreased and the braking ski Fy and Fz remained the same with higher skiing speed. During the subsequent kick phase, both ski Fy and Fz increased significantly as a function of the skiing speed. Consequently, the Fy ratio between the ski and the pole plant increased with faster skiing speed. Simultaneously measured EMGs from five different muscles showed that the abdominals had a pattern of increasing activation with increase in speed of skiing. All the other muscles, vastus lateralis (VL), rectus femoris (RF), erector spinae (ES), and medial gastrocnemius (MG), were obviously active in the preloading and the kick phases. CONCLUSIONS: The speed dependence of the ski and the pole force distributions in the present study are important for further understanding of the complexity of cross-country skiing. Especially relevant is to use these results as basis for studies aimed at better understanding of the propulsive force production, when more comprehensive EMG analysis is complemented with simultaneous kinematic recordings at varied slope, speed, and waxing conditions.     

Assessment of the reliability of a custom built Nordic Ski Ergometer for cross-country skiing power test

AIM: Despite the recent development of cross-country ski technique having led to an increase in the importance of upper body power, there is a substantial lack of specific equipment for upper body force and power evaluation. In order to achieve good reproducibility of the skiing motion, a new upper body ergometer has been developed in our lab and tested by elite cross-country skiers. In this study, the reliability of this device was assessed comparing upper body power measurements with double poling ski performance in the field. METHODS: The new apparatus consists of an electric motor acting as load and actively controlled by a personal computer on the basis of force and velocity data. Nine cross-country skiers (age: 21.7+/-3.12 years; body weight: 72.2+/-3.8 kg), competing at international level, performed a ski test on a 1.2 km long sprint track and a 50 s exercise on the Nordic Ski Ergometer. The velocity of the last section (180 m, slope 1.37%) of the track, performed using the double poling technique at maximal voluntary intensity, was related to the upper body power measured at the ergometer. RESULTS: Mean upper body power was 9.22+/-2.29 W kg(-1), while average velocity on the section considered was 6.66+/-0.67 m s(-1). A high correlation (R(2)=0.871) was found between upper body power and ski velocity. CONCLUSION: In addition to overcoming the main limitations that affect traditionally used equipment, the strong relationship between the parameters obtained with the new ergometer and ski velocity indicates their ability to assess athletes performance. The new apparatus could therefore be considered a ski specific testing equipment for cross-country skiers which is useful for reproducing upper body involvement in cross-country ski-ing in a laboratory setting.     

Cross-Country Skiing

Lighter-weight equipment, better groomed trails, and the increasing popularity of ski-skating techniques have introduced a new element to cross-country skiing: speed. Although the overall injury rate remains low, the number of traumatic injuries in cross-country skiers appears to be increasing. Most ski injuries, however, are still caused by overuse and can be easily prevented with proper conditioning.     

The effect of pre-season dance training on physical indices and back pain in elite cross-country skiers: a prospective controlled intervention study

OBJECTIVE: To evaluate the effect of pre-season dance training on back pain, joint mobility, and muscle flexibility, and on speed and agility in elite cross-country skiers. METHODS: 26 skiers participated (mean (SD) age, 19 (3.9) years). An intervention group (n = 16) had 12 weeks of dance training; a control group (n = 10) did not dance; otherwise both groups followed a similar pre-season physical training programme. Joint mobility and muscle flexibility of the spine, hip, and ankle were measured. Two sports related functional tests (slalom and hurdle) were also done. All measurements/tests were carried out before and after the dancing period. RESULTS: Four (of six) subjects from the intervention group who initially complained of ski related back pain did not report back pain after the dance training; the three subjects with back pain from the control group were unchanged. At study onset the intervention group had a slightly impaired range of motion in the spine compared with the control group. After dance training, there was a better relation between kyphosis of the thoracic spine and lordosis of the lumbar spine, and a 7.1 degrees increase in hip flexion with the knee extended (p = 0.02). In the control group hip extension decreased by 0.08 m on average (p = 0.01). No positive effects of dance training on sports related functional tests were observed. CONCLUSIONS: Preseason dance training improved the range of hip motion and joint mobility and the flexibility of the spine. These improvements might explain the reduction in ski related back pain in the intervention group.     

Anterior compartment pressures in cross-country skiers. A comparison of classic and skating skis.

This paper compares the pressure changes in the anterior compartment of the leg when cross-country skiing using the skating method on either skating skis or classic skis. Intracompartmental pressures of the right leg were recorded from the tibialis anterior muscle of 10 subjects at rest and 15 seconds after 10 to 12 minutes of cross-country skiing on a designated course. All subjects completed two trials on different days. In one trial, subjects used skating skis and for the other trial, classic skis were used for the skating technique. Although the average pressure increase was higher for the classic ski trials than for the skating ski trials, the difference was not significant. This finding indicates that cross-country skiers who skate on a classic ski as opposed to a shorter skating ski do not experience a significantly greater increase in their anterior compartment pressure. Thus, it appears that the type of ski used is not the most significant factor contributing to chronic compartment syndrome.     

Occurrence and trends in ski injuries in Norway

OBJECTIVES: To provide an overview of ski injuries in Norway and to describe the changes between 1990 and 1996. METHODS: All ski injuries (7966) treated at four hospitals providing health care to a defined population of about 11% of the Norwegian population were registered prospectively from 1990 to 1996. For this study, 6462 injuries sustained in cross country skiing, downhill skiing, telemark skiing, and snowboarding were selected for further analysis. RESULTS: The relative distribution of ski injuries by type of skiing changed significantly from 1990 to 1996 (p<0.001). Injuries from snowboarding showed the highest relative increase, and those sustained during downhill skiing showed a decline. The proportion of fractures in all types of skiing increased during the study period (p=0.001). The proportion of injuries to knee/lower leg decreased and the proportion to the forearm/wrist/hand increased during the study period (p=0.03). The mean age of the injured skiers differed significantly among the different types of skiing activity (p<0.001): cross country skiers were the oldest followed by telemark skiers, downhill skiers, and snowboarders. CONCLUSIONS: Ski injury surveillance results in early detection of changes in temporal injury trends, allowing timely adjustment of injury prevention strategies. Injuries from snowboarding are on the increase in Norway, warranting more effective injury prevention measures.


     

Bronchial hyperresponsiveness in skiers: field test versus methacholine provocation?

INTRODUCTION: Asthma is frequently reported in endurance athletes, particularly in cross-country skiers. It has been reported that an exercise field test performed with the competitive type of exercise is the better for diagnosing asthma and bronchial hyperresponsiveness in athletes than bronchial provocation with methacholine. OBJECTIVE: The main objective was to compare an exercise field test consisting of a skiing competition with methacholine bronchial provocation in the diagnosis of asthma and bronchial hyperresponsiveness among skiers. METHODS: Twenty-four elite cross-country skiers from the Norwegian national teams (males/females = 16/8) were included in the study. The cumulative dose of inhaled methacholine causing a 20% fall in forced expiratory volume in 1 s (FEV1) (PD20) was compared with reduction in lung function (FEV1) >or= 10% from before to after an exercise field test consisting of a cross-country skiing competition, 10 km (males) and 7 km (females), respectively. RESULTS: Nine out of 24 (37.5%) athletes experienced a positive methacholine test (PD20 < 8 micromol) (2 females and 7 males), whereas only 2 of the 24 subjects (8.3%) had reductions in FEV1 >or= 10% after the exercise field test. A significant negative correlation was found between age and bronchial responsiveness, r = -0.47, P = 0.02. CONCLUSION: The methacholine bronchial provocation test is more sensitive than a sport specific exercise field test for identifying athletes with asthma and/or bronchial hyperresponsiveness.     

Self-reported asthma and exercise-induced asthma symptoms in high-level competitive cross-country skiers

The prevalence of asthma and exercise-induced respiratory symptoms in 153 high-level Norwegian cross-country skiers and 306 control subjects were assessed in a postal survey. The response rates were 100% for the skiers and 79% for the controls. A present or past history of asthma was reported by 14% of the skiers and 5% of the controls. The prevalence of asthma increased signhcantly with increasing age among the skiers but not among the control subjects. The majority of the controls who reported asthma dated the onset of the disease to childhood, while the skiers dated the onset of asthma primarily to late adolescence or early adult life. The skiers used anti-asthmatic medication significantly more often than did the controls. Exercise-induced respiratory symptoms such as chest tightness, shortness of breath, cough, wheezing and sputum production were re- ported by 2–3 times as many skiers as controls. Exacerbation of respiratory symptoms was frequently associated with cold weather, humid weather or with recovering from an airway infection. The results of the present study indicate that cross-country skiers may be at an increased risk for acquiring obstructive respiratory disorders.     

Epidemiology of alpine skiing injuries in lowlanders

During one alpine skiing season injuries were registered prospectively among 951 Danish alpine skiers. The injury incidence was 19.4 injuries per 1000 skiing days, or 3.4 injuries per 1000 skiing hours. The incidence of injuries treated by a doctor was 5.9 injuries per 1000 skiing days, which is 2–5 times higher than previously reported. Lower extremity doctor-treated injuries comprised 65% of the total and upper extremity doctor-treated injuries 25% - a distribution seen 25 years ago in alpine skiing countries. Only 18% of the thumb injuries were seen by a doctor. Neither age, preholiday training, self-rated skiing ability, ski school attendance during the week nor the use of rented versus owned equipment significantly influenced the risk of injury.     

Maximal strength training improves work economy in trained female cross-country skiers.

PURPOSE: The present study examines the hypothesis that maximal strength training improves work economy and anaerobic threshold in trained female cross-country skiers while working on a ski ergometer. METHODS: Fifteen female cross-country skiers (17.9 +/- 0.3 yr, 166.7 +/- 1.3 cm, 60.1 +/- 1.9 kg, and 55.3 +/- 1.3 mL x kg(-1) x min(-1)) participated in the study. Eight skiers made up the high-intensity strength-trained group, and seven served as the control group. Endurance performance was tested on a specially instrumented ski ergometer. Strength training and testing simulated double poling in cross-country skiing. RESULTS: A significant (P < 0.001) improvement in double-poling economy on the ski ergometer was observed among the strength-trained group. Anaerobic threshold did not change during the experimental period for either group. After a 9-wk training period, time to exhaustion increased from 5.2 (+/-0.9) to 12.3 (+/-1.6) min (P < 0.001) and from 4.0 (+/-0.9) to 6.3 (+/-0.9) min (P < 0.01) for the strength and control group, respectively. Time to exhaustion was significantly higher (P < 0.001) for the strength group compared with the control group after training. One repetition maximum increased 14.5% (1.8) (P < 0.001) in the strength group but was unchanged in the control group. Expressed in relation to peak force at one repetition maximum, strength training resulted in a significant reduction in the relative available force employed working on the ski ergometer (P < 0.01). Time to peak force at maximal aerobic velocity on the ski ergometer was significantly reduced in the strength-training group (P < 0.01). CONCLUSIONS: It is concluded that maximal strength training in the upper-body improved the double-poling performance by improved work economy. Work economy was improved by a reduction in relative workload and time to peak force while double poling.     

Interaction of potential intrinsic and extrinsic risk factors in ACL injured recreational female skiers

The aim of this study was to investigate the interaction of potential intrinsic and extrinsic risk factors in ACL injured recreational female skiers. 93 female recreational skiers who had suffered a non-contact ACL injury and 93 age-matched controls completed a self-reported questionnaire relating to intrinsic risk factors (menstrual history, BMI, previous knee injuries, self reported weekly sports participation) and extrinsic risk factors (type of ski used, time of last binding adjustment, snow condition, weather and slope difficulty). A logistic regression model revealed the following independent ACL injury risk factors for female recreational skiers: icy snow conditions (odds ratio, 24.33; 95% confidence interval, 6.8-86.5, P<0.001), skiing during snowfall (odds ratio, 16.63; 95% confidence interval, 1.8-152.1, P=0.013), use of traditional skis (odds ratio, 10.49; 95% confidence interval, 2.0-54.5, P=0.005), and preovulatory phase of menstrual cycle (odds ratio, 2.59; 95% confidence interval, 1.2-5.5, P=0.013). In conclusion, ACL injuries in female recreational skiers are the result of a complex interaction of intrinsic and extrinsic risk factors.     

The energy cost of cross-country skiing among elite competitors

The energy costs of skiing with the diagonal stride technique was investigated in 15 members of the men's and women's national cross-country ski teams and in 5 recreational skiers. Oxygen uptake was measured directly by means of a portable bag-method for each subject during level skiing at 3 different skiing speeds. The oxygen cost of double poling vs. diagonal stride techniques was also measured in 3 subjects during level skiing. Although a strong linear relationship was found between VO2 and speed of skiing (r = 0.868, p less than 0.001), there was considerable variation even among elite competitors. The VO2-skiing speed relationship was parallel to that obtained for running, but the O2 cost of skiing was found to be 10--12 ml/kg in excess of that predicted for level running at the same speed. On flat terrain, the O2 cost of the double poling technique as used in fast skiing was found to be higher than that for diagonal striding.     

The influence of body mass in cross-country skiing

The influence of body weight on the performance in cross-country skiing has been studied by: dimensional analysis of the ratio (R) between the factors of importance to power production (VO2max, acceleration of gravity) and the braking powers, e.g., friction and air resistance; measuring the energy cost of level skiing (N = 6); comparing male world class skiers (N = 5) with less successful ones (N = 34) and female winners of the National Championships (N = 9) with non-winners (N = 9) in regard to the relationship between body weight and VO2max. The dimensional analysis revealed that R was less than unity for rather steep uphills. For level, downhill, and less steep uphill skiing, R was greater than unity. Thus, skiers who are light will be favored in steep uphill slopes, whereas heavier skiers have advantages in the other parts of the track. Energy cost per kilogram for level skiing was inversely related to the transported mass. Per unit of distance, this cost was positively related to velocity. The world class skiers displayed significantly greater VO2max than the less successful ones, regardless of the unit used. The lowest standard deviation among the world class skiers was attained when expressing VO2max as ml X min-1 X kg-2/3. The present results indicate that R will be quite close to unity and therefore the performance capability would theoretically be independent of body mass. Furthermore, VO2max is preferably expressed as ml X min-1 X kg-2/3 for cross-country skiers.