Nutrition Position Stand for Cross Country Skiers

Written by Ben Bunting: BA, PGCert. (Sport & Exercise Nutrition) // British Army Physical Training Instructor // S&C Coach.

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Cross country skiing (often referred to as Nordic skiing) is an extremely demanding sport that requires effective recovery from food sources for athletes to perform at the optimal level for competition.

In this article we shall cover the following:

• Introduction 
• Key Points 
• Type of Sport 
• Recovery 
• Research Review 
• Physiological Demands 
• Macronutrients
• Carbohydrate
• Protein 
• Fats 
• Hydration
• Supplements 
• Sleep 
• Summary 
• Example of meal plans
• References

Position Stand: Recommended nutritional requirements for effective recovery in cross-country skiers.

Recovery after endurance exercise is of paramount importance for the elite athlete, and nutrition is a vital component of this process to help the body repair to enhance performance (Moore, 2015).

This position stand will outline the macronutrient, fluid and energy requirements for winter sport athletes, specifically cross-country skiers (XCS) post training and competition. The recommendations take into consideration the additional physiological demands due to the extreme climate (Doubt, 1991)

Key Points:

1. The sport imposes extensive physiological challenges with endurance and strength demands on the athlete resulting in increased energy requirements between 55 to 75 kcal/kg/d (Burke, 2004).

Furthermore, energy expenditure is increased at high-altitude with the additional risk of appetite suppression (due to hypoxia) which can reduce lean tissue mass and performance efficiency (Hill et al, 2011; Marriott, 2013).

Inadequate energy intake (EI) can also lead to an increased risk of infection, menstrual irregularities, a decrease in cardiovascular performance and bone health (Logue et al, 2020).

EI needs to be able to sustain performance whilst also maintaining optimal body composition for the varied terrain during competition (Bergh, 1992)

2. Carbohydrates (CHO) are the preferred fuel source for muscular activity. Depletion of glycogen stores leads to fatigue and exhaustion during long bouts of exercise that need replenishing (DI, 1991).

The recommendations are for XC skiers to consume 7-10g/kg of total CHO daily (Maughan, 2008). Post exercise CHO consumption should average 50g per 2 hours (Coyle, 1991). When recovery times are scarce, 1.2g/kg/h of CHO is recommended for rapid glycogen replenishment (Kerksick et al, 2017).

3. General protein (PRO) intake recommendations are 0.25g/kg/d to maximise muscle protein synthesis (MPS) and to be consumed in feedings at every 3 hours where training allows. Post exercise PRO consumption (15-25g) should be within 2 hours. Contemporary research suggests that maximal training adaptations can be achieved with 0.3g/kg/d. (Kerksick et al, 2017; ACSM, 2016).

4. Fat intake should be no less than 20% of the athlete’s energy intake to avoid an inadequate intake of essential fatty acids and to aid the absorption of fat-soluble vitamins.

5. Increased altitude can increase respiratory water loss due to the cold air containing less moisture, urine excretion increases along with a reluctance to drink sufficient fluids place athletes at a risk of dehydration and reduce performance (ACSM, 2019; Thomas et al, 2016). Re-hydration during recovery should be 125-150% of the deficit. Sweat rate should be measured to ascertain individual fluid requirements (ACSM, 2018). A guide it to consume 500ml 2h prior to exercise with c.150ml every 15 mins during exercise (ACSM, 2016). Alcohol consumption during recovery is discouraged due to the diuretic effects and the reduced rates of MPS (Parr et al, 2014).

6. Iron turnover is high in XC skiers to maximise absorption foods containing iron should be accompanied by a source of vitamin C (Burke, 2005; Hallberg et al, 1989).

7. Food first approach to be taken with supplements only to be used based on avoiding a nutrient deficiency which can result in greater cell damage and reduced antioxidant profiles leading to impaired performance (PHD, H.G) Any supplementation is to be under the supervision of a nutrition expert.

8. Sleep deprivation can result in impaired performance due to effects on the athlete’s metabolic, endocrine, and nutritional status with detriments toward physical and physiological adaptation to training (Halson, 2014). Young adults need 7-9 hours of sleep (Hirshkowitz et al, 2015).

What is Nordic Skiing?

Winter Games and World Championship XC races can vary in length from 1.2km for the Individual Sprint up to 50km for the Mass Start race with differences in the course profile, and applied techniques with the energy system combining aerobic and anaerobic contributions (Losnegard, 2019).

XC skiing is almost unique in endurance events due to high aerobic turnover rates combined with high work rates above VO2peak (c.120 to 160% VO2peak) and interspersed with short recovery periods during the downhill sections of the course.

Nutritional requirements for endurance athletes, particularly for winter sports, is characterised by high energy expenditure (EE), increased fluid loss, high rates of muscle and liver glycogen utilisation, and increased iron turnover (Maughan, 2013).

Energy is a concern for XC skiers with calculations for energy requirements being 90kcals per kg of bodyweight (NordicSkiRacer [online]) and reports of up to 8341kcals being spent (Maughan, 2013).

Athletes also need carbohydrate availability throughout competition and training to replace glycogen stores. Furthermore, the source of carbohydrates is important for pre, during and post exercise (Nutritional Needs of Endurance Athletes [online]).

Due to the exhaustive nature of the sport, exacerbated by the climate, the performance of the athlete rests on nutritional intake and timing which needs to be consistent and reflective of the work rate (Logue et al, 2017).

Low energy availability can lead to disruption of many bodily functions including immunity, metabolic risk, cognitive function, bone health and increase the risk of injury and thus reducing their availability to compete (Burke, 2010).

Post Ski Recovery

To perform at a world-class level, an athlete’s recovery management is essential, the recovery between exercise or competition is the period when adaptation to training occurs and should not be treated as passive. [30]

During this period, the athlete needs to refuel, replace lost fluids, and repair muscle damage by providing the body with the appropriate macro and micronutrients from various sources to delay the onset of factors such as dehydration, electrolyte imbalance, glycogen depletion and hypoglycaemia (Ivy, 2004).

Recovery and replenishment of nutrients should commence as soon as possible after high intensity exercise to initiate muscle repair and adaptation, failure to do so can delay the recovery process which may be time sensitive.

Carbohydrate sources should be available to consume every 30 minutes accompanied by protein with a ratio of 4 to 1 to Limit muscle damage and promote MPS (Peake, 2017).

Appropriate recovery minimises the risk of overtraining and can enhance competitiveness for the athlete (Kentta, 1998). Endurance athletes are vulnerable to overtraining syndrome which leads to chronic fatigue, a high risk of infection and underperformance (Gremion, 2014).

Recovery is multi-faceted and complex involving pathways, yet nutrition and rest can enhance the benefits gained from exercise adaptations (Luttrell, 2015).

The consideration for sleep is also paramount for recovery and is critical for health. Sleep deprivation results in a reduction of endurance, submaximal strength, reaction times and accuracy (Vitale et al, 2019).

Physiological Demands of Sport

The nature of XCS makes it one of the most demanding endurance sports due to the combined effort of both upper and lower limbs across varying terrains, utilizing different racing techniques in response to the course with adjustments of intensity in a cold environment at altitude (Holmberg, 2015).

Races can last as little as 2.5 minutes and extend to around 2 hours, while the courses are generally split into thirds of flat, uphill and downhill, around 50% of the time is spent going uphill with this performance being the marker of success (Holberg, 2015).

It is noted that XCS achieve exceptionally high VO2max levels (>80 and >70 mL·min−1·kg−1 for men and women) (Ingjer,2007) particularly when compared to soccer players (51,70 ml/kg/min) and non-athletes (41,53 ml/kg/min) (Rankovic et al, 2010).

This high level of aerobic capacity and power determine the outcome of competition across multiple techniques over different terrains. It is the ability to convert energy into power as efficiently as possible which separates XCS from other athletes to reach higher levels of performance (Sandbakk et al, 2010).

Notably it is the employment of both upper and lower body muscle groups that places maximal demands on oxygen supply yet maintains low blood lactate accumulation and mild arterial oxygen saturation being mild regardless of high oxygen uptake (Holmberg et al, 2006).

Two techniques are identified for XCS; classic and freestyle.

Between 1000-3000 meters in elevation is the hypoxic region where there is a decrease in air density (Michalczyk et al., 2016). For every one percent decrease in saturated blood oxygen, a 1-2% decrease in VO2max will occur. The top highest altitude XCS areas in Europe are within 2000-3400m in elevation (Snow-Online [Online]).

It is maximal aerobic capacity, gross efficiency and high-speed capacity which determines success in XCS.

Macronutrient Requirements for Athletes

Macronutrients are required for growth, repair, and maintenance of the body. They are consumed in large amounts and consist of carbohydrates, fats and proteins (Exploring Nutrients [Online])

The main fuels utilised are carbohydrates and fatty acids. Carbohydrates are the primary source of energy during exercise and the capability of the muscle to store glycogen are paramount to success with (Ortenblad et al, 2013) research demonstrating that XCS are able to store up to 100% more glycogen in their muscles than those who are untrained (Gejl et al, 2014)

The nature of XCS involves simultaneous activation of upper and lower muscle masses results in high demand for CHO availability, with studies showing that leg muscle glycogen stores are depleted from 50-10% post 10 and 50km races with arm glycogen stores showing a 30% depletion, the low temperatures also place a further demand on CHO oxidation rates (Rusko, 2003; Layden et al, 2002).

Fatty acids are stored and obtained within the bloodstream and the muscles as intramyocellular lipids in amounts up to four times more than untrained individuals.

Endurance exercise stimulates protein synthesis and degradation. It is debated whether there is an additional need for protein intake other than the recommendations already established (Holmberg, 2015; Gilba, 2007).

However, it was surmised by literature published in 2019 that post vigorous exercise oxidation rates increased compared to those during rest and post moderate exercise (Gerlof et al, 2019).

Furthermore, if individuals do not consume adequate energy (due to altitude induced loss of appetite) during periods of catabolic stress they are at risk of losing lean muscle mass (Carbone et al, 2012) which can lead to a loss of performance and increase the risk of injury, therefore this could warrant increased protein intake over the current guidance (Pons et al, 2018).

Carbohydrate Requirements for Endurance Athletes

Levine et al, observed in the early 1900s that low blood sugar levels post endurance exercise was the cause for fatigue. They tested this theory by feeding marathon runners a high carbohydrate diet which significantly improved the athlete’s performance.

Carbohydrates serve as the primary fuel during high-intensity exercise, and muscle glycogen can provide over 32 calories per minute during exercise leading to rapid depletion of stored glycogen.

Glycogen can also be replenished quickly when carbohydrate sources are consumed (Academy, USS, 2008). While fat can also be used as a fuel during exercise, it is not as efficient during oxidation whereby carbohydrate generates rc=120kcal per mole of respired oxygen against 100kcal per mole of oxygen for fatty acids (Jeukendrup, 2004).

CHO can support utilization of aerobic and anaerobic pathways (Bernadot et al., 2016) and will provide a greater yield of ATP that is delivered to mitochondria for energy (Spiret, 2014).

Research into recreational marathon running has demonstrated that glycogen depletion is likely to happen around 33km, yet elite athletes with larger leg muscles and greater aerobic capacities can avoid this depletion (Romijn et al, 1993).

Therefore, carbohydrate loading during recovery can influence recovery by allowing an endurance athlete of a given aerobic capacity and well-developed leg and arm muscles to perform at higher speeds and avoidance of failure experienced with glycogen depletion (Rapoport, 2010)

It was observed that during two days of training and competition, the majority of female and male elite XCS were carbohydrate deficient for their needs (Carr et al, 2019).

Daily Requirements

Recommendations for CHO intake vary slightly, but for athletes who have very high exercise demands aim to ingest 7-12g of CHO per kg of body mass on a daily basis (Burke et al, 2012)

For maximal glycogen refuelling, it is suggested that 1g per kg of body weight is optimal to kick starting the process. (Burke & Cox, 2010).

CHO ingestion post exercise should amount to no less than 200g in 4 hours post exercise with 600g within 24 hours (Coyle, 1991).

Carbohydrate Type

For rapid replenishment of CHO, foods with a high GI should be chosen (Burke & Cox, 2010), these can be in the form of sports drinks, energy gels (maltose and glucose) or fruits this is because it has been found that low GI foods are not as effective as replenishing muscle glycogen stores, nor is fructose although it does enhance liver glycogen restoration (Kerksick et al, 2017)

If a longer recovery opportunity is available (24 hours or more) there is less need to be picky about the GI index of foods and a variety should be consumed (Bean, 2006).

Carbohydrate Timing 

Research demonstrated that glycogen replenishment rates were 50% faster and more complete when CHO was ingested within 30 minutes of exercise compared to waiting 2 hours (Burke & Cox, 2010).

Further study has also concurred these findings whereby glycogen can be quickly and maximally replenished by ingesting 0.6-1.0g per kg of bodyweight within 30 minutes of exercise and again every 2 hours for the following 4 to 6 hours (JI, I. 1998) or when aggressive CHO loading was ingested every 30 minutes post exercise for up to 3.5 hours (Jentjens, 2003) Further suggestions advise 1.g/kg/hr every 15 minutes up to 5 hours post exercise (Tarnopolsky et al, 2005).

Some studies have suggested that there is a window of opportunity within 1 to 2 hours post exercise to effectively restore glycogen due to the body being primed for blood glucose to be delivered to the muscle and being stored (Van Loon et al, 2000).

Timing is important because the body can store muscle glycogen at a rate of around 5% per hour, and therefore it may take 24 hours to fully replenish (Burke, 2010).

The Role of Protein

Endurance exercise stimulates whole-body protein turnover, and performance can be enhanced by consuming adequate protein intake shortly after exercise to stimulate protein synthesis.

The muscle cells of endurance athletes will build more proteins that can transport glucose and fats to be used for fuel (Burke, 2010).

It has been stated that post-exercise protein intake for the endurance athlete can be potentially useful to optimize physical performance.

Protein intake timing is often debated, yet, to not consume any protein will not offer any benefit and may have a negative effect (Burke, 2010).

Most studies into protein supplementation have focused on resistance training rather than its effects on endurance exercise which limits our knowledge regarding its effect on performance, however, dietary protein intake has a critical role in many of the physiological process in the body (Cintineo et al, 2018).

It can also provide energy, but at just 4kcal obtained from 1g it is not the ideal fuel source (Wu, 2016).

Requirements for Endurance Athletes

Athletes looking to optimize training adaptations should look to consume 1.4-1.6g per kg of bodyweight per day.

Furthermore, for those undergoing chronic training and during a calorie restriction a higher intake of 2.3-3.1g/kg/d is suggested to maintain lean muscle mass (Protein – British Nutrition Foundation [Online]).

This higher recommendation maybe appropriate for XCS skiers who appear to consume fewer calories than required which may compromise athletic performance (Jager et al, 2017).

Certainly, a study by Kato, et al. (2016) suggests that endurance athletes should be consuming 1.2-2g/kg/d to maintain protein balance and to benefit capillarization, synthesis and turn-over of mitochondrial proteins and proteins involved in oxygen transport including haemoglobin and myoglobin.

Post exercise protein intake should be no more than 25g in a single serving. MPS appears to be stimulated at 10g and plateaus at 20-25g (Papadopoulou et al, 2012).

Protein Types and Functions

Rapidly digesting proteins are preferred for recovery that contain 600-3000mg of leucine and other amino acids (Burke & Cox, 2010). Animal sources such as dairy and meats are ideal or a combination of mixed vegetable proteins (Jager et al, 2017).

For night-time recovery, casein protein can increase MPS while asleep (Burke & Cox) while combining CHO and PRO enhances recovery and muscle building (Jager et al, 2017).

Timing of Protein Intake

Levenhagen et al. (2001) observed that protein degradation was not affected by the timing of protein feeding post exercise, however, MPS was increased 3-fold when supplementation was immediate compared to a 3-hour delay of PRO consumption (Bean, 2006).

Further study also recommends PRO consumption within 2 hours post exercise (Levenhagen et al, 2001 & Phillips, 2011) with subsequent PRO feeding every 3 to 4 hours (Beelen, 2010).

Healthy Fats for Athletes

Some fats are essential and provide fuel substrates for exercise while also facilitating the absorption of fat-soluble vitamins A, D and E. Fat is also an essential element of all cell membranes (Bean, 2006).

It has also been stated that Omega-3 fatty acids may increase the deliverance of oxygen to the muscles which can promote endurance and muscle recovery.

Recommendations for athletes stipulate that the proportion of calorie intake for saturated fats to not exceed 10% (ACSM, 2016) and research into the metabolic flexibility of a high fat diet for performance is limited and not considered beneficial for those athletes who partake in high-intensity training or competition (Burke, 2015).

Daily Requirement of Fat

Meyer and Simmons (2009) observe that winter athletes’ fat intake can range from 25-40% of total EI, with the higher levels possibly among the less experienced skiers with a lack of nutritional knowledge but the intake of fats is to be no different in winter athletes to that of summer sport athletes (Meyer, 2011).

Athletes should not restrict their daily intake of fats to less than 20% of total energy intake as this may restrict the intake of fat-soluble vitamins, carotenoids, essential fatty acids and potentially conjugates linoleic acids (Vitale, 2019).

Intake of fats should not exceed 30% of calorie intake, yet it is recommended that a higher intake (within the guidelines) improves circulating testosterone concentrations than a fat restrictive diet. If the athlete is looking to decrease body fat to adjust body composition suited to XCS their intake should be 0.51g/hg/day (Pramukova, 2011).

Type of Fats

Essential polyunsaturated fatty acids offer the most health benefit for athletes (Kreider et al, 2010). As such, consumption of salmon, tuna and mackerel, flaxseeds, pumpkin seeds walnuts and oils such as olive oil, flaxseed and soy oil is recommended (Varga, 2008).

Timing post exercise

There is limited information regarding fat intake timings, particularly concerning recovery (Kerksick et al, 2017). It is suggested that fat should be accompanied by CHO loading (Vitale, 2019).

Importance of Hydration for Athletes

Endurance athletes are susceptible to dehydration, and even more so when competing or training at altitude and in extreme climates.

Even a 1-2% bodyweight loss of fluid will negatively affect performance and cause problems maintaining core temperature (Antonio et al, 2008).

Additionally, the cold climate can impair thirst sensation, reduce the desire to drink and has shown that soldiers operating in cold climates can be as dehydrated as operating in hot weather with up to 3-8% of bodyweight dehydration.

The cold air contains much less water vapour than warmer air which can exacerbate respiratory water loss (Marriott et al, 1996).

Additional problems can occur with consuming fluids at low temperatures. Strategies to combat loss and replenish fluids can include choosing warmer drinks, including hot chocolate that could double up as a warming recovery and fluid replacement drink (Penney, S.).

Additionally, sports drinks are better than water due to the sodium content helping retain water and prevent hyponatraemia, these could be kept in thermal containers to prevent freezing (SDA, 2015).

Additional consideration should be given to adding glycerol to water as Freund (1995) demonstrated that in cold weather adding glycerol doubled water retention of the fluid consumed than when it wasn’t added.

Glycerol also adds calories to the water than would benefit XCS and it reduces the freezing point of water, and thus could be useful in the cold climates that skiers train and compete.

Rehydration strategies include drinking 150% of the amount lost through sweat, respiration and excretion (McDermott et al, 2017). Including 1.0g/kg/BW of glycerol to 1.5l of fluid consumed post exercise enhances the plasma volume replenishment (Rosendal et al, 2010).

What Supplements should an Athlete take?

There is the concern of high iron turnover in XCS (Haymes et al, 1986). This needs to be monitored and addressed through dietary interventions on an individual athlete basis with the potential use of an iron supplement.

Athletes are to take a ‘food first’ approach to their diet, thus, they should be able to get all of their macro and micronutrients from food sources. Additionally, Sousa et al (2016) reported that those athletes who were using supplements were less likely to suffer from a micronutrient deficiency and were unlikely to benefit from using dietary supplements.

However, there are a small number of compounds that could have additional benefit as outlined by the ACSM (2016) which may be considered for use for XCS.

Supplements of interest are:

• Caffeine
• Beta-alanine
• Nitrate
• Sodium bicarbonate
• Creatine

XCS combined both anaerobic and aerobic activity with 50% of the time being spent going uphill with short periods of recovery during the downhill sections of the course.

The bursts of high intensity anaerobic activity present a case for creatine, sodium bicarbonate and beta-alanine which can both improve work capacity and performance during high rates of anaerobic glycolysis.

There is evidence suggesting the use of nitrate and caffeine to improve exercise tolerance, reduce the perception of fatigue, and improve output for longer which would complement the endurance aspects of XCS.

Limitations

Individually, these supplements have evidence demonstrating their effectiveness, yet when combined there is a lack of cohesion even when theoretically certain pairings could be beneficial as surmised by Burke (2018).

The exception appears to be combining caffeine and creatine. (Doherty et al., 2002; Trexler et al., 2016) Caffeine in doses of 3-4.5mg/kg/BW have shown a significant performance benefit (Stadheim et al, 2014).

Importance of Sleep for Athletes

Disturbances in sleep has a negative effect on athlete performance due to the implications on recovery, repair, immuno-suppression, and training adaptations (Reilly, 2007).

While athletes are identified to have poorer sleep due to a few factors it is now recognised that sleep is a foundation of performance (Halson, 2017). Nine hours of sleep are recommended for elite athletes and should be considered as important as diet and training (Vitale et al, 2019).

Position Stand Summary

The following summary is based on evidence informed principles presented in this position stand.

XCS are susceptible to inadequate EI which results in fatigue, potential injury, infection, and reduced performance. During the recovery phase CHO and PRO should be consumed as per the guidelines in combination for optimal muscle glycogen restoration and MPS.

Fat consumption should be monitored and not exceed 30% of total EI nor should it be below 20% to ensure adequate fat-soluble vitamin absorption.

Fluid intake needs to be adequate in consideration of altitude, climate and ‘sweat rate’. The addition of glycerol is advised to improve fluid retention, increase EI and prevent water from freezing.

Food is the primary source of micronutrient intake, but iron turnover should be monitored. The combination of caffeine and creatine should be considered as per the guidelines to assist with performance.

Meal Plan Examples

Table 1. Example of post training/competition (<30mins) feeding suggestions.

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