Alpine Skiing

Fitness Testing Assignment: Alpine Skiing - by Ulli Julich

Contents

• Introduction
• Characteristics of a Successful Alpine Skier
• Fitness Testing Procedures
• Conclusion
• References

Introduction

Skiing is known to be a basic means of transport in Northern Europe for 3000 to 4000 years. Skiing as a competitive sport had its origin in the Scandinavian countries. In the beginning of this century skiing spread out throughout Europe and in the 1950s skiing became popular in North America (Andersen and Montgomery 1988). In the last decade it has been the fastest growing outdoor recreational activities in the USA, with 9% of the American population over 12 years of age participating in skiing (Morrissey et al 1987).

In the 1988 Olympic Games Alpine Skiing included 5 different events: Slalom, Giant slalom, Downhill, Super Giant and Combined. Usually skiers participate in more than one Alpine event. The 4 different disciplines show differences in speed, turning radius of the skis and length of the course.

The Downhill (D) course follows the fall line of the hill. The average speed for the downhill is 100 km/h with speeds of 140 km/h in steep sections of the course. The downhill skiers try to maintain an aerodynamic "tuck" position for the duration of the race, lasting 2 to 3 minutes.

The Super Giant (GS) is a combination of downhill and giant slalom with duration of about 80 to 90 seconds. These two events are termed "speed events".

Slalom (SS) races are on steep terrain with the gates close together. Because the slalom skier is constantly turning across the fall line, the average speed is lower than in GS, with 20 to 40 km/h. The SS requires the most agility compared to the other events.

Whereas Giant Slalom (GS) requires the most technical performance, in contrast to downhill, the gates are closer together, but not directly in the fall line demanding carved turns through the whole race. Average speed in GS is about 75 km/h and the race has a duration of 60 to 90 seconds. GS and SS are termed the "technical events".

The alpine combined consists of a shorter downhill course and a slalom race (Andersen and Montgomery 1988).

Alpine skiing requires aerobic and anaerobic power, muscular strength, high and complex motor skills including quickness, agility, balance, flexibility and co-ordination (Åstrand and Rodahl 1986, White and Johnson 1993). Contributing factors such as courage and appropriate psychological properties are as well highly demanded in the elite skier.

Characteristics of a Successful Alpine Skier

Body Type

The characteristics between skiers of the 4 different events seem to vary. According to the anthropometric data evaluation of the last 10 years the successful skier is now taller and heavier than in the past (Karlsson 1984). Brown and Wilkinson (1983) support these findings, using skinfold thickness measurement. They found that male skiers are quite lean (8-10%), while female skiers average 20-22% bodyfat. This indicates that the higher weight of the elite athletes is devoted to lean body mass. Slalom skiers are usually leaner than skiers of the other events, whereas downhill competitors are the heaviest (Haymes an Dickinson 1980).

Body composition appears to be an important factor in performance. Haymes and Dickinson (1980) showed that smaller, leaner males performed more successful in the SS event (had lower FIS points), while skiers with more bodyfat did better in downhill events.

Muscle Fibre Composition

Rusko et al (1978) showed that the percentage ST fibres distribution of alpine skiers is higher (63% ST in vastus lateralis, ±8 SD) than in ordinary reference subjects (47 % ST±13 SD). Whereas Tesch (1995) states that alpine skiers do not show a distinct fibre type composition, but a tendency to a preponderance of slow twitch fibres.

Similar results are reported by Anderson and Montgomery (1988) reporting a FT/ST ratio in elite Alpine skiers of 1.14. In comparison the ratio for endurance athletes is 1.03 and for high jumpers and sprinters 1.52 in average. Both muscle fibre types are recruited during SS and GS.

Muscle Glycogen Utilisation

The exercising muscle uses glycogen as both aerobic and anaerobic energy sources. The study of Eriksson et al (1977) suggests that skilled skiers (Swedish National Team Member) have the ability to reduce muscle glycogen more than recreational skiers.

Tesch et al (1978) examined the utilisation of glycogen in ST and FT fibres in skilled and unskilled skiers. They found that skilled skiers have greater glycogen depletion in the ST fibres compared with the unskilled. A possible explanation is that the experienced skier recruited more ST fibres because these fibres are more resistant to fatigue. This study suggested that GS has a greater glycogen utilisation compared to SS.

Aerobic Metabolism

Skiing is usually classified as an anaerobic event, considering the longest event (D) takes 3 minutes (Tesch 1978). However, it is difficult to differentiate between the contribution of the energy sources in the overall energy expenditure. Specially for this particular outdoor sport, laboratory conditions are difficult to reproduce, because the involved movements are not repetitive. Most studies investigating skiing, measured oxygen consumption in laboratory or in field settings. The results indicate that aerobic power is an important factor for successful skiing. High aerobic capacity increases the ability to recover from repeated bouts of anaerobic exercise, and allows the athlete to sustain aerobic work for a longer duration (Song 1982). Because most competitions occur at altitudes between 2500- 3500m adequate aerobic power is needed.

Elite alpine skiers have a high aerobic capacity compared to normal individuals (Brown and Wilkinson, Rusko et al 1978). However the general aerobic power shown by the Italian national team with 52 ml/min/kg (Veisteinas et al 1984) and 59 ml/min/kg (Saibene 1985) is not very impressive. Andersen and Montgomery (1988) have demonstrated high variation of VO_{2 max} (49.1-70 ml/kg/min) as a result of their literature research. The highest value of 70ml/min/kg was reached by Ingemar Stenmark. This exceptional result measured in an elite athlete, may reflect the training programme of the athletes and not the actual demands of the sport (Karlson 1984). The Swedish national team seem to emphasise more the aerobic work, because the results of their members over the last 10 years period showed an average VO_{2 max} above 65 ml/kg/min (Tesch 1995).

Anaerobic Metabolism

Anaerobic power is important factor in skiing. According to the results of Veicsteinas et al the anaerobic contribution to the energy metabolism amounts 65%. According to White and Johnson (1991) anaerobic tests (repeated jump test, absolute power from vertical jump, 30 second Wingate test) appear to be better predictors of alpine skiing ability compared to aerobic power tests . Because of its high reproducibilty and simplicity the vertical jump is chosen (Bosco et al 1983). The vertical jump is a ballistic motion using the stretch shortening cycle, which has been shown to be more sportsspecific simulating skiing actions than test on a bicycle.

Strength

Skiers have very high leg strength compared to other athletes (Song 1982 and Tesch et al 1978). Haymes and Dickinson (1980) found that the most predicting performance factor in the US Ski Team men and women's leg strength.

Thigh muscles are important for balance as well as the initiation and completion of the turns. The hamstring muscles protect the knee by reducing the anterior shear that the quadriceps creates at the tibia. Furthermore very high leg strength is required to overcome the enormous external forces developed during skiing. Good developed muscles allows the skier to function at lower percentage of maximal strength which may result in less occlusion of blood flow and greater resistance to fatigue (Haymes and Dickinson 1980).

Over the last decade Alpine skiing at top level has changed significantly. Athletes are skiing smaller radii turns, using more lateral movements and relatively little up-and-down movement. These changes in technique are also associated with equipment changed. Changes that relate to the construction of the ski, the binding and the boots result in an higher demand upon the absolute strength of the alpine athlete.

Fitness Testing Procedures

For the 4 different skiing disciplines little data are available which distinguish between the physiological demands for each event. To investigate skiing performance either laboratory or on-snow measurement are used. While laboratory assessment has the advantage to control the conditions and using tests that have been demonstrated to be reliable, the on-snow assessment has the advantage of sport specificity, although the methods of data collection are limited (White and Johnson 1991). The on-snow assessment is one specific method to determine the aerobic contribution of alpine skiing.

Aerobic Test (VO_{2 max})

Protocol

Only a few studies measured oxygen uptake during skiing using portable light weight analysers. The following study of Veicsteinas et al (1984) is one of these few investigations devoted to the cost of and energy sources for this type of activity.

All 8 male subjects were top ranked members of the Italian National Team. Five skiing instructors served as control subjects. The top skiers showed an average VO_{2 max} of 52.4 ml/min/kg the control group 51.2 ml/min/kg respectively. These data were obtained by an open-circuit method during treadmill running at increasing speeds up to exhaustion.

In the on-snow assessment VO₂ was measured using O₂ and CO₂ Beckman analysers and a Collins dry-gas meter after exact calibration at altitude. The expired air was collected in a balloon placed in a sack fixed on the skier's shoulders. Heart rate was continuously monitored by a portable Holter tape recorder fixed to the subject's belt. Lactate concentration was determined by an enzymatic method in blood withdrawn from the cubital vein immediately before the race and at the 5th min of recovery. The O₂ equivalent of Lactate was assumed to be 3.15 ml O₂/kg bodyweight for an increase of blood lactate of 1 mmol/l.

The field test was set up at an altitude of 2850 m. The track was traced by experts according to international standard for SS and GS (length, slope and number of gates). After preliminary trials, tracks were chosen requiring about 55 seconds for SS and 70 seconds for GS for all-out performance by top skiers. After 10 minutes of light skiing with the apparatus for measuring VO₂ and the electrocardiographic recorder in place, the expired air was collected in 3 different bags:

1. at rest for 3 minutes (bag 1)
2. from the start to the end of the task (bag 2)
3. during the first 2 minutes of recovery (bag 3).

The change of bag 2 to 3 occurred in 2-3 seconds, with the skier standing, so that at most one breath was lost.

Then the total oxygen cost ( DVO₂ tot) of each performance was calculated.

Results

In both top skiers VO_{2 max} was 52.4±7.8 ml/min/kg and in the control subjects 51.2±4.7 ml/min/kg, which is similar to moderately fit individuals.

Former studies showed that elite skiers perform at approximately 90% of their VO_{2 max}, whereas unskilled skiers reach 65-75% of VO_{2 max} (Tesch 1978). However the results of Veicsteinas et al (1984) suggest that referred to the time, the energy demands are equivalent to 160% VO_{2 max} during GS and 200% during SS respectively. The data of Saibene et al (1985) show 120% of VO_{2 max} for GS are lower than those found by Veicsteinas et al.

The latter research team calculated from their data, that in SS and GS the energy sources were about 40 % aerobic, 20% alactic, and 40% lactic metabolism.

Therefore White and Johnson (1991) and Tesch (1995) conclude that maximal aerobic power or aerobic capacity are unlikely determinants for success in high level skiing.

Anaerobic Test (60 second vertical jump test)

Protocol

The vertical jump test was first introduced as a measurement of general muscle power by Sargent (1924). A number of test protocols have been derived from the Sargent test.

Bosco et al (1983) used the following protocol to evaluate the mechanical power:

The flight time of consecutive vertical jumps during a certain time period (60 seconds) is measured. An electronic apparatus called "Ergojump" (Junghans GmbH-Schramberg, BRD) is therefore used. This apparatus consists of a digital timer (±0.001 second) connected by a cable to a resistive (capacitative) platform. The timer is triggered by the feet of the subject at the moment of release from the platform, and will be stopped at the moment of contact coming down. This way the flight time (tf) of the subject during the jump is recorded. In this protocol subjects perform consecutive jumps, therefore the timer sums the respective tf of the single jump. For the estimation of maximal mechanical power of the leg extensor muscles, the protocol requires that the subject jumps continuously with maximal effort on the platform for a certain period (60 seconds). To standardise the knee angle displacement at the contact phase, the subject is asked to bend the knees to about 90 degrees. Horizontal and lateral displacement should be minimised in order to avoid unmeasurable work output. Subjects were instructed to keep their hands on the hips throughout the jump. The total displacement of centre of gravity above the ground (h in meters) was calculated using recorded flight time (tf in seconds) applying ballistic laws.

Total displacement (m):

Where g = 9.81 m.s^-2

Average mechanical power (W/kg):

Where Tt = Total performance time (60 sec)
Tf = Sum of total flight time
Tc= Total contact time.

If the total time (Tt) of the jumps series is 60s, the power formula can be written:

Where n is the number of jumps.

Thirty-eight subjects participated in the study. They all performed the jumping test and sprinting test (60 meter dash) on one day and Wingate (60 seconds) and Margaria at the next day.

Results

The results of the study showed a high correlation (r=0.87, n=12 males) of jumping test and Wingate test therefore either of this two tests can be used for determination of explosive power. The power output calculated for jumping (20 W/kg) was much higher than that calculated for Wingate (7W/kg) and Margaria (14 W/kg) test respectively. This seemed to be primarily attributed to the large values recorded for the jumping test, because similar values were found in the literature for Wingate and Margaria. The authors contribute this finding to the different mechanical behaviour of the leg muscle while jumping. The power out put during jumping does not measure only the power of the chemomechanical conversion. Leg extensor muscles follow the stretch-shortening cycle activation during jumping. This type of muscular activity allows the storing and re-use of elastic energy. The gravitational potential energy affects jumping exercises more than when running uphill, and it is negligible in bicycling. Consequently work and power output are higher for jumping related to the use of the stretch shortening cycle compared to activities where muscles only concentrically. In addition leg muscles work alternatively while cycling and work and rest simultaneously during jumping exercise.

The Wingate test showed much higher concentration of blood lactate (ª15mM/l) the jumping test also requires anaerobic energy system (8mM/l). That means that during a 60 sec jumping performance a great proportion of the work by anaerobic energy-yielding processes.

Bosco et al (1983) concluded based on the high reproducibility (r=0.95) of the jumping test, that the jumping test may give the possibility of evaluating mechanical power of the lower extremity muscles during explosive stretch-shortening type exercise, which includes both metabolic and mechanical behaviour of muscles.

The jumping test can be criticised as an inappropriate for skiers, because calf muscle are intensively used during jumping. Because of the skiboot construction which restricts movement in the ankle joint, little muscle activity has been shown in calf muscles while skiing.

Strength

The use of isokinetic dynamometers gave the opportunity to examine force velocity relationship of different athletes. Male Alpine skiers demonstrated increased strength preferentially at slow concentric speed as shown by Brown and Wilkinson (1983) and Haymes and Dickinson (1980) found similar results for both gender. At concentric muscle actions with high angular velocity they displayed lower knee extensor strength than sprinter and jumper (Haymes and Dickinson 1980). Male alpine skiers had more strength than females except at 30 degrees/seconds when expressed relative to the lean body weight.

Protocol of Brown and Wilkinson (1983)

Their sample consisted of 42 male alpine skiers, members of Canadian national (n=10), divisional (n=10), or club (n=22) teams. Subjects were tested with a Cybex II isokinetic dynamometer in seated position with the thigh restrained. The axis of the dynamometer was aligned with the knee joint. Then the lever arm was adjusted according to the leg length and strapped to the tibia 2 cm proximal to the malleoli. After three practise/warm-up contractions with each leg, three maximal contractions were recorded with the right leg at 30 degree/second (deg/s), followed by a one minute pause, and then at 180 deg/s. The results for quadriceps and hamstrings were expressed as torque corrected for each subject's body mass (Nm/kg).

Results

In the study of Brown and Wilkinson no significant limb strength difference were observed between national and divisional skiers (Table 1). However, national skiers had a significant greater leg strength at both speeds. The national skiers demonstrated also a lower strength ratio than the club skiers.

Table 1. Isokinetic leg strength of male alpine racers (adapted from Brown and Wilkinson 1983)

	National (n=10)	Divisional (n=10)	Club (n=22)
PT 30 deg/s (Nm/kg)	3.98±0.14*	3.88±0.17	3.44±0.10
PT 180 deg/s (Nm/kg)	2.08±0.05	2.07±0.07	2.01±0.09
Hamstring/Quadriceps ratio (%)	57.6±1.4*	61.8±1.7	65.6±1.9

Values are means ± SE
*Significant p<0.01 difference from club team

Alpine skiing always has been characterised as an explosive movement, perhaps because the high speed achieved, while performing lateral direction changes. However, research indicate that knee and hip angular velocities are quite slow even in SS. The knee joint angle velocity lies between 20-50 deg/s during concentric and eccentric action of a turning GS, and they are not much higher in a slalom race and marginally lower in SG.

No data are available for D but it could be assumed that the knee angular velocity is also low for both muscle actions. EMG measurements have shown that GS is dominated by eccentric muscle action (Hintermeister et al 1995). Although GS, SG and SS require slow knee angle movement using the knee extensor muscle in eccentric mode, Tesch (1995) failed to show that elite skiers have more eccentric strength than other power athletes.

Conclusion

Elite skiers can be differentiated from non-elite skiers on the basis of power, strength and motor characteristics. However, as skiing is a typical technique dependent sports, no special physiological variable is dominant that can definitely predict performance within high level performance (White and Johnson 1993). However, the potential use of certain tests that have shown validity and reliability lies in talent identification. Furthermore tests can be used to monitor the compliance and effectiveness of training. Another area where these tests can be used is the evaluation of the effectiveness of a rehabilitation program following injury. Because the tests have shown to be sports specific in terms of intensity and movement pattern, these tests are useful for the athlete's assessment to his readiness to return to on-snow training and competition (Reid et al 1997).

References

Andersen RE and Montgomery DL (1988)

Physiology of Alpine Skiing. Sports Medicine 6:210-221.

Åstrand PO and Rodahl K (1986)

Textbook of work physiology. (3rd ed.) New York: Mc Graw Hill.

Bosco C, Luhtanen P, Komi PV (1983)

A simple method for measurement of mechanical power in jumping. European Journal of Applied Physiology 50:273-282.

Bosco (1997)

Evaluation and Planning of conditioning training for alpine skiers. In: Mueller E et al (Eds): Science and skiing. London: E & FN Spon, 1997

Bacharach DW, Duvillard von SG (1995)

Intermediate and long-term anaerobic performance of elite Alpine skiers. Medicine and Science in Sports and Exercise 27(3):305-309.

Brown SL and Wilkinson JG (1983)

Characteristics of national, divisional, and club male alpine ski racers. Medicine and Science in Sports and Exercise 15(6):491-495.

Eriksson A, Forsberg A, Nilsson, Karlsson (1978)

Muscle strength, EMG activity, and oxygen uptake during downhill skiing. In: Biomechanics VI-A Asmussen E and Jørgensen (Eds) Baltimore: University Park.

Haymes EM, Dickinson AL (1980)

Characteristics of elite male and female ski racers. Medicine and Science in Sports and Exercise 12(3):153-158.

Hintermeister RA, O'Connor DD, Dillman CJ, Suplizio CL, Lange GW, Steadman JR (1995)

Muscle activity in slalom and giant slalom skiing. Medicine and Science in Sport and Exercise: 27(3):315- 322.

Jasmin BJ, Montgomery DL, Hoshizaki TB (1989)

Applicability of the hexagonal obstacle test as a measure of anaerobic endurance for alpine skiers. Sports Training, Medicine and Rehabilitation 1:155-163.

Morrisey MC, Seto JL, Brewster CE, Kerlan RK (1987)

Conditioning for skiing and ski injury prevention. Journal of Orthopaedic and Sports Physical Therapy 8(9):428-437.

Karlson J (1984)

Profiles of cross-country and alpine skiers. Clinics in Sports Medicine 3(1):245-265.

Rusko H, Havu M, Karvinen E (1978)

Aerobic performance capacity in athletes: European Journal of Applied Physiology 38:151-159.

Saibene F, Cortli G, Gavazzi, Magistri P (1985)

Energy sources in alpine skiing (giant slalom). European Journal of Applied Science 53:312-316.

Song TMK (1982)

Relationship of physiological characteristics to skiing performance. Physician and Sportmedicine 10:97-102.

Tesch PA (1995)

Aspect on muscle properties and use in competitive Alpine skiing. Medicine and Science in Sports and Exercise 27(3):310-314.

Vandewalle H, Pérès G, Hugues M (1987)

Standard anaerobic exercise tests. Sports Medicine 4:268-289.

Veicsteinas A, Ferretti G, Margonato V, Rosa G, Tagliabue D (1984)

Energy costs of and energy sources for alpine skiing in top athletes. Journal of Applied Physiology 56(5):1187-1190.

White AT and Johnson SC

Physiological comparison of International, National and Regional alpine skiers. International Journal of Sports Medicine 12(4):374-378.

White AT and JohnsonSC (1993)

Physiological aspects and injury in elite alpine skiers. Sports Medicine 15(3):170-178.

Exercise Physiology Educational Resources 1998