NUTRITION RECOMMENDATIONS FOR ALTITUDE TRAINING

KEY POINTS

Altitude research and associated nutrition reviews have mainly focused on high to extreme altitudes (> 3,000 m). Recent data and associated practical nutrition recommendations are emerging from studies conducted at altitudes where athletes typically train (~1,600–2,400 m).

• Until further research on carbohydrate and fat oxidation and/or protein metabolism during exercise is conducted during the types of training undertaken by athletes at low to moderate altitudes (~1,600–2,400 m), guidelines for altered macronutrient needs remain theoretical and should align with sea-level recommendations.
• It is not clear whether low to moderate altitudes have alternative effects on energy availability (EA) requirements and/or risk for Relative Energy Deficiency in Sport, but there are several recent studies to suggest that EA will play an important role in optimizing hypoxic adaptations.
• The micronutrient iron is especially important at altitude, as hypoxia results in a distinct environment where the erythropoietic drive increases reticulocyte formation and hemoglobin mass gains, which are dependent upon adequate iron availability.
• A common theme that has emerged is that more research in physiology, metabolism and nutrition should focus on low to moderate altitudes that elite athletes use for training.

INTRODUCTION

The implementation of altitude training to optimize elite athlete performance rose to prominence prior to and during the 1968 Mexico City Olympics (held at 2,250 m above sea level). Since this time, there has been an explosion in the utilization of altitude, as well as the supporting science, in the preparation of elite athletes for competition (Mujika et al., 2019). By extension, given the altered hypoxic environment and resultant altered metabolism, there are many unique nutrition-based recommendations required to optimize altitude adaptations. However, most of the research and the associated nutrition reviews have focused on high to extreme altitudes (> 3,000 m) (Bergeron et al., 2012). Therefore, the focus of this Sport Science Exchange (SSE) article will be on the novel data and associated practical nutrition recommendations that are emerging from work at low to moderate altitudes that athletes typically implement into their periodized training (~1,600–2,400 m). For a comprehensive review, see Stellingwerff et al. (2019b).

GENERAL NUTRITION AND HYDRATION RECOMMENDATIONS AT LOW TO MODERATE ALTITUDES

Many elite athletes travel to specific global altitude training locations for 2–4 week training camps, repeated several times per year, rather than reside continually at altitude (Mujika et al., 2019). Therefore, it should be recognized that when most athletes enter any “training camp” situation, regardless of the altitude, they tend to increase training loads. So regardless of the hypoxic stress, the practitioner, along with coaches and athletes, should not neglect the sea-level importance of contemporary sports nutrition guidelines. Although it is commonly accepted that altitude results in increased carbohydrate (CHO) oxidation during exercise, and thus CHO intake requirements, it should be noted that the study demonstrating this was conducted at 4,300 m (Brooks et al., 1991), and another study in females at the same altitude actually showed decreased CHO utilization (Braun et al., 2000). Therefore, until further metabolism research (CHO vs. fat oxidation, protein metabolism) is conducted during the types of training undertaken by athletes at low to moderate altitudes (~1,600–2,400 m), guidelines to address macronutrient needs remain theoretical, and should align with sea-level recommendations (Burke et al., 2019; Stellingwerff, 2013; Stellingwerff et al., 2019a).

The lower air humidity associated with most altitude environments, along with hypoxia, are also likely to increase fluid losses at rest and during training. Furthermore, there are increased respiratory water losses coupled with hypoxic-induced diuresis that can also result in significant increases in water requirements at altitude to prevent dehydration (Butterfield et al., 1992). Therefore, increased hydration diligence and hydration status monitoring should be implemented. These include monitoring urine characteristics and daily body mass (BM) changes and being proactive with fluid intake during and after training sessions and with meals. Table 1 highlights unique altitude training camp situations that may require enhanced monitoring and/or nutritional interventions for the practitioner to consider with their athletes.

EFFECTS OF ALTITUDE ON ENERGY AVAILABILITY, BODY MASS AND ADAPTATION

Energy availability (EA) is a concept reflecting the amount of energy that is available after exercise for use by other body processes (such as endocrine, immune, skeletal and reproductive systems) and is calculated as energy intake (EI) minus exercise energy expenditure (EEE) relative to fat-free mass. Optimal EA is not only an important consideration at sea level, but also while at altitude, especially given the increased stress of hypoxia. This concept of low EA has recently been coined Relative Energy Deficiency in Sports (RED-S), and can have important and significant outcomes not only on athlete health but also performance (Mountjoy et al., 2018). However, it is not clear whether low to moderate altitudes have alternative effects on EA requirements and/or increase the risk of RED-S, but there are several recent studies to suggest that EA will play an important role in optimizing hypoxic adaptations.