About Winter Sports

A winter sport is a sport commonly played during the winter season on snow or ice. The temperature of the winter sports performed in an outdoor environment range from - 25 to + 10° C, while the temperature of those performed indoors average 5° to 10° C. Sport-specific training and competition for many winter sport athletes commonly requires some degree of exposure to higher altitude (2,600 - 3,500m). Training and competing at altitude and in the cold weather results in a compounding of environmental stress and metabolic challenges that carry a number of nutritional implications.

The winter sports that are part of the Olympic Winter Games include biathlon, bobsleigh, curling, ice hockey, luge, skating, skeleton, and skiing. There are five disciplines of skiing and these include alpine, cross-country, ski jumping, Nordic combined, freestyle and snowboarding.

This Fuelling Fitness Article will provide the background on the nutritional implications for skiing. Specifically, the effect of altitude and cold exposure as these are unique aspects to these sports.

Seasons

The preparation phase of the annual year occurs from May to late October with a European Summer Grand Prix for Nordic combined and Ski Jumping held in August. The winter competition starts at the end of October and concludes in late March. The Olympic Games and World Championship are held during the month of February and occur 3 out of the 4 year cycle. The off-season is held during the month of April.

Each athlete competes in approximately 30 - 45 events over a five-month winter season. Fifteen to twenty of the competitions are World Cup events. The competition characteristics vary with each event as the terrain, weather, snow conditions, and frequency of competition create a variety of physical challenges for the skier.

Physical characteristics

Body composition requirements and energy systems differ greatly with each winter sport. The winter sports that require low body weight are Nordic combined and ski jumping. Nordic combined athletes are at least 5 kg and ski jumpers 10 kg below their ideal body weight. Computer simulation shows that the jump length decreases by approximately 1 m/kg of increased weight. There is a tendency for very young athletes to compete in international competitions because they generally weigh less than their older athletes of similar height. Delayed growth and maturation has also been observed in ski jumpers as well as extreme weight loss and eating disorder cases.

Maximal anaerobic power is seen as an important determinant of ski jumping performance as the sport involves the production of one powerful movement, which occurs at take-off. Nordic combined athletes require a high aerobic power and anaerobic capacity for cross-country skiing and maximal anaerobic power for ski jumping.

Historically cross-country skiers were described as tall and lean individuals. The physical structure of cross-country skiers has changed over the last twenty years with them now reported as muscular and having average height. Cross-country skiing is an endurance sport requiring a high aerobic and anaerobic capacity. Cross-country skiers have the highest VO2 max of all endurance athletes.

Successful alpine skiers appear tall and heavy with a high lean tissue mass. In general, slalom skiers tend to be lighter and leaner than speed skiers in events such as downhill and "super-G". Increased body weight may be of some benefit in alpine skiing due to gravitational forces that, at least in part, are dependent on body mass, regardless of composition. Peak anaerobic power is identified as a significant predictor of successful skiing performance.

No scientific data are available on the physique and physiological characteristics of mogul and aerial skiers. Because many aerialists have a gymnastics background, it is expected that physique characteristics are similar to gymnasts, particularly the female athlete, although aerialists appear older and heavier. Energy metabolism in freestyle skiing for both events are expected to receive a large contribution via anaerobic energy pathways due to their high intensity and short duration. Energy for the aerialist is predominantly provided by the ATP-CP system due to the short duration of a jump (6 - 7 seconds), while the mogul skier relies to a greater extent on muscle glycogen.

Training Diet

The most important nutritional factors to consider when working with winter sport athletes are the cumulative effect of cold and altitude that may lead to increased energy expenditure, greater reliance on blood glucose and muscle glycogen, and exacerbated fluid loss.

Upon ascent to altitude, the sympathetic nervous system is up-regulated. It has been shown that this hypoxia-induced rise in catecholamines is both acute and chronic, with the main objective to preserve blood flow and oxygen delivery to tissues and organs. The acute rise in epinephrine results in changes in heart rate, stroke volume, and cardiac output. Norepinephrine's rise occurs later, peaking by day seven at altitude and remaining elevated through the course of exposure. The elevation of norepinephrine leads to an increase in ventilation, vasoconstriction, as well as blood and vascular pressure.

Altitude exposure is frequently accompanied by weight loss caused, at least in part, by negative energy balance due to appetite suppression and increased energy expenditure. Work in the cold may increase energy requirements, with 10 - 15% of the rise in energy expenditure probably accounted for by the inefficiency of exercising in heavy snow and thermoregulation.  Factors, in addition to ambient temperature, including wind chill, radiation from the sun, and humidity which can influence the physiological strain of defending core temperature in the cold.

It has previously been demonstrated that fuel selection at high altitude shifts to a greater use of blood glucose for men both at rest and during exercise compared to sea level. Also it has been shown that carbohydrate oxidation may be elevated up to six-fold during shivering thermogenesis. This rise in carbohydrate oxidation is provided by greater plasma glucose turnover, muscle glycolysis, as well as glycogenolysis.

Living and/or training at altitude increases the athletes need for adequate iron stores in order for hematological adaptations to occur. Although well managed today, iron deficiency and depletion remain the most prevalent nutritional deficiency in winter sports. Today a complicating factor is the ability to manage and limit strategies used by athletes to manipulate hematological indices, even though they may be viewed as natural.

Fluid Needs

Fluid requirements are higher in the cold compared to temperate environments, as cold air contains less water than warmer air, even if relative humidity is the same. Thus, cold exposure leads to a small but significant increase in respiratory water loss. In addition, cold temperatures can result in an impaired thirst response and increased diuresis, possibly leading to hypohydration and subsequent voluntary dehydration.

Nordic combined and ski jumping athletes compete in the European Summer Grand Prix and athletes wear their winter suits during summer training and competition. Consequently, fluid requirements are elevated due to a high sweat rate.

Unfortunately, to date, there are no specific recommendations for fluid replacement during exercise in the cold and/or at altitude for winter sport athletes. It is estimated that the athletes fluid demands are half of those recommended for similar summer sports.

What Should I Eat/Drink During Competition?

Energy provided for cross-country skiing performance is predominantly supplied by aerobic metabolism and the utilization of carbohydrate and fat. For cross country events longer than 15 kms event feeds (sport drink) are provided to the athletes. Transporting a large volume of fluid onto the ski course and keeping the temperature of the beverages at 10 - 20° C are challenges encountered by the coaches. It is recommended that warm sports drinks be carried in leak-proof containers that have thermal covers.

For the other skiing events fluid is provided at the end of the first and final run or jump. Carbohydrate rich snack foods are available to athletes if needed. Food is however eaten if there is a race delay due to weather conditions.

What About Recovery?

Due to the large anaerobic contribution to alpine and freestyle skiing performance, a high rate of glycogen utilization is likely to occur during a day of intense ski training. Glycogen stores can be reduced to 50% of initial value after a typical day of training for skiing. For cross country skiing fatigue during a prolonged training session or ski-race is often associated with the near or complete depletion of glycogen stores. Consequently recovery of these stores should start as soon as possible after prolonged and/or high-intensity training and racing. 

A further challenge to the skiers is the delayed return to accommodation sites after training, which may slow recovery time and affect the next day's training.

How to get involved

Australia is starting to be internationally successful in freestyle, snowboard and alpine skiing. Presently the Australian Government is supporting Australians involvement in sliding sports and cross country skiing. To cover the sports nutrition aspects in winter sports, the integration of a sports dietitian into a team is essential. To get involved Sport Dietitians need to travel, witness and understand the sports and the challenges the athletes experience.

Author: Susie Parker-Simmons, Sports Dietitian and Physiologist,  United States Ski and Snowboard Team.

Click here to download  Winter Sport fact sheet (65KB)