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Nutrition and Performance in Sport

 | 
Christophe Hausswirth

Chapter 1. Nutrition: from training to competition

Topic 2. Altitude

Yann Le Meur, Eve Tiollier, Amélie Fosse, Christophe Hausswirth, Axel Heulin, Véronique Rousseau et École Lenôtre

Texte intégral

Questions and answers

Key points
Prolonged exposure to altitude has a significant impact on nutritional behaviour. As this may affect performance, we conclude that sports success at altitude, or maintaining a high training capacity in a hypoxic environment, are closely related to the athlete’s nutritional status. Thus, athletes will have to strive for two main objectives: on the one hand, limiting the extent of weight loss and muscle mass reduction and, on the other hand, maintaining sporting performance as far as possible. In this respect, it seems beneficial to:
favour spontaneous food intake, particularly foods containing both carbohydrates and protein;
monitor hydration to maintain a positive water balance ;
plan to take iron supplements four months before the beginning of training at altitude or hypoxic training (if iron deficiency is a problem).

Does training at altitude modify athletes’ eating habits?

1Most of the studies investigating how athletes’ eating habits change during training at altitude or mountaineering show that there are modifications. Thus, at high altitude, athletes tend to reduce their food intake. This “altitude anorexia” is the main reason why weight loss is almost systematically observed after extended periods at altitude. While the reduction in body mass is mainly linked to a loss of fat mass, long-term perturbation of the energy balance can also lead to decreased muscle synthesis and increased protein oxidation during exercise. This can, ultimately, lead to reduced muscle mass. To fight against this phenomenon and maintain performance levels, it is recommended that athletes be encouraged to increase their spontaneous food intake, and to ensure that they maintain their muscle mass during the period spent at altitude. This can be helped by planning regular maximum-strength tests.

Why is it essential to maintain a high carbohydrate intake when training at altitude?

2Beyond the spontaneous reduction of food intake, several studies have shown that altitude also modifies how the energy used during exercise is resynthesized. The main effect of this is an increase in the use of muscle glycogen stores. This greater dependence on carbohydrates during exercise could balance the decrease in partial oxygen pressure in the air by favouring the use of an energy substrate which provides a greater ATP yield for a given amount of oxygen (i. e. compared to a similar amount of lipids). This hypothesis is reinforced by the observation that lipid stores are slightly less prone to depletion during exercise at altitude compared to a reference situation at sea level. Even if this greater solicitation of sugar metabolism seems to diminish in the medium term in acclimatized athletes, it remains significant, even after several weeks at altitude. This adaptation appears to be beneficial in terms of energy production, but it accelerates the decrease in muscle glycogen stores during intense training sessions. In terms of nutrition, carbohydrate intake must therefore be increased during training at altitude. Thus, the Acceptable Macronutrient Distribution Range should be adjusted so that 60% of total calories are provided by carbohydrates. Favouring a high-carbohydrate diet will limit protein oxidation, thus reducing the risk of altitude-related muscle loss. Given the spontaneous tendency of athletes to reduce their daily calorie intake when at altitude, implementation of a nutritional plan could be extremely beneficial. This will involve using the post-exercise table as far as possible and adapting timing of sugar intake (see Fact sheet No. 1 Energy recovery, p. 235). In the context of a particularly intense training course at altitude, consuming a high-carbohydrate diet for the two days before departure will help to limit the risk of muscle glycogen depletion, which can lead to a decrease in the athlete’s training capacity (see Fact sheet No. 3 Competition, p. 258).

Why is it so important to have a hydration plan when training at altitude?

3Water loss plays a significant role in the reduction in lean mass observed during periods spent at high altitudes. Indeed, in a hypoxic environment, fluids are transferred from inside cells to the extracellular environment; this intracellular dehydration can be exacerbated by poor hydration habits and inadequate hydration during training. In addition, normal daily water losses can be significantly increased when the athlete trains in a cold and dry environment, as water loss through the upper respiratory tract and the bronchial tubes can increase considerably as they play their role in heating and moistening the air. Despite this, dehydration is often not perceived as readily in the mountains as at lower altitudes, because inhaling cold air reduces the sensation of thirst. Given the effects of dehydration on performance during endurance and strength exercises, it is essential to make sure that you are appropriately hydrated when training or performing at altitude (see Fact sheet No. 10 Hydration, p. 342).

How can nutritional intake promote better sleep despite perturbations due to adapting to altitude?

4During the first days of adaptation when training at altitude, athletes generally do not sleep well, especially when they have a high training workload from the beginning of the course. This is caused by significant perturbation of sleep cycles; sleep is lighter, and thus does not afford the same degree of recovery. As a consequence, the athlete might have difficulties recovering from training and tends gradually towards a state of chronic fatigue. To help prevent this, during the first days of adaptation, the evening meal should include foods favouring sleep (see Fact sheet No. 12 Sleep and alertness, p. 371).

5Most of the research dealing with dietary adaptations to promote sleep have tried to increase the availability of tryptophan, the precursor of serotonin, which is involved in sleep. However, very few foods, as such, have been investigated in scientific studies to determine their capacity to promote sleep. Therefore, we must rely on anecdotal evidence, such as the effect of consuming high-glycaemic index carbohydrates. Consuming this type of meal decreases the time you take to fall asleep. The timing of the meal also appears to be important, with greater effects if the meal is taken four hours before going to bed, rather than one hour.

6In other studies, tryptophan was provided directly, not as food but in the form of supplements. It is worth noting that the best food source of tryptophan is milk, and that carbohydrate consumption creates a favourable hormonal environment for its entry into the brain (leading to serotonin synthesis). In contrast, consuming protein (meat, fish, eggs) reduces the availability of serotonin in the brain and favours the synthesis of other neurotransmitters such as dopamine and noradrenalin, which have stimulating effects.

7Other foods which are thought to have calming effects include plants such as valerian, hops, lemon, hawthorn, passionflower. Among these, the one that has been the focus of most research is valerian. However, the results obtained so far are contradictory, and we cannot currently confirm that this plant promotes sleep. Nevertheless, if taken as an infusion, these plants can help promote sleep through two effects: a behavioural effect, where this habit is part of the bedtime ritual, and due to its action on core body temperature. Consuming a hot drink decreases the core temperature, which is required for good sleep. Similarly, a glass of hot, sweet milk combines three conditions favourable to sleep: tryptophan intake (milk), favourable hormonal context (carbohydrates) and decrease in internal temperature (hot drink).

Should athletes take vitamin or mineral supplements before and during training at altitude?

8Most of the time, athletes who are preparing for a training course at altitude plan to take vitamin and mineral supplements. Even though there is currently no clear evidence that increasing vitamin intake is advantageous in this context, it is essential to make sure you have adequate iron stores to adapt, and react positively, in physiological terms, to the environmental stress caused by the altitude change. Indeed, hypoxia constitutes the strongest demand on the body’s iron stores, exceeding even the demands of pregnancy. To adapt to hypoxia, the body responds by stimulating red blood cell production, which draws on iron reserves. This enhances the blood’s capacity to transport oxygen (red blood cells fix oxygen thanks to a haeme group containing an iron atom). An anaemic athlete will thus have difficulty training and recovering at higher altitude, since their body will not be able to implement the necessary physiological adaptations for acclimatization to this new environment. Therefore, it is essential to assess the level of the iron stores (i. e ferritin levels) for each athlete before starting the training course, and iron supplements should be taken if necessary. The iron status can only be improved over several weeks; therefore, this type of intervention will need to be planned at least a month before the start of the training course.

Practical applications

1. Before the training course

Three months before

9► Have your iron status checked

10› If you are iron deficient, consult a professional to start supplementation, so you can start the course with an optimal iron status

Three days before

11► Increase the carbohydrate content of your food

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12► Add a carbohydrate snack in the afternoon

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2. During the course: general recommendations

Image 10000000000000210000001F332268A1.jpg Energy intake: hunger mechanisms are modified. Eat at least as much as usual, if not more. Focus on increasing your intake of carbohydrates (complex carbohydrates, fruit).

13 Increase your carbohydrate intake

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14► Maintain a high intake of polyphenols and antioxidants

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15► Maintain a high protein intake without necessarily increasing the quantities

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16 Monitor your hydration

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17 Drink regularly throughout the day

Pay particular attention to your hydration status. To do so, check the colour of your urine Image 10000000000001510000002860BA0386.jpg

3. During the course: training

Before

18 Make sure you are well hydrated

During

19 For the same exercise performed at altitude, the body burns more carbohydrates, and water losses are increased

Image 1000000000000407000001E3600D2C09.jpg

After

20 Main priority: water and energy recovery (see Fact sheet No. 1 Energy recovery, p. 235)

21► If the meal is to be eaten more than 30 minutes after the end of training, you shouold have a snack

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4. Improve how you sleep during the course

Dinner

22 Preferably eat between 3 and 4 hours before going to bed

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23 Drink herbal tea (valerian, lemon, passion flower, hops) or a glass of sweetened hot milk in the evening. This can help you to get to sleep

Image 100000000000002300000021133C4BE5.jpgImage 10000000000000230000001EAE0ED3FB.jpg Errors to avoid

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Breakfast

Eat an additional source of proteins Image 100000000000012E0000001E13E22CD6.jpg

Recipe

Golden mash and black pudding

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Photo credit: Thibaut Ruggeri.

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24Serves 2

25Preparation time: 20 minutes

26Cooking time: 50 minutes

Difficulty: Image 10000000000000290000001FEE6AE643.jpg

27Ingredients

28 250 g black pudding

29 400 g floury potatoes

30 50 g onions

31 200 g apples (Golden Delicious or russet apples)

32 150 g semi-skimmed milk

33 1 pinch of turmeric

34 10 g oil

35 30 g breadcrumbs

36 Salt, pepper

37 2 small curly endives

38Wash, peel and chop the potatoes.

39Steam them for 20 to 25 minutes, and mash them in a potato ricer.

40Heat the milk and turmeric. Add to the mashed potatoes. Season.

41Chop the onion and cut the apple into small cubes.

42Sweat the onions in the oil, add the diced apple and cook for 5 minutes.

43Remove the skin from the black pudding. Mash the pudding with a fork.

44Spread a layer of mashed potatoes at the bottom of a dish, scatter with the cooked apples and top with a layer of mashed pudding. Finish with a layer of mashed potatoes.

45Sprinkle with breadcrumbs.

46Preheat the oven to 200 ° C and bake for 20 to 25 minutes until golden.

47Serve with small curly endives.

48Chef’s note

49Thanks to the black pudding, this meal is very rich in iron: it covers almost one-and-a-half times the daily requirements for women (and two-and-a-half times those of men). However, it is high in calories so it should therefore be combined with a light starter (a raw vegetable or a vegetable soup) and a fresh fruit-based dessert (for example, an orange salad: the vitamin C will help with iron assimilation).

50Nutritional analysis per person

Energy (Cal)

Carbs (g)

736

64

Lipids (g)

Protein (g)

44

21

Auteurs

© INSEP-Éditions, 2015

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