Nutrition and Physical Activity                                                                         Topic 37 
                    Module 37.3 
                    Nutrition for Endurance and Strength Sports 
                                                                                               Nada Rotovnik Kozjek, MD, PhD  
                                                                                                                     anaesthesiologist 
                                                                      Institute of Oncology, Ljubljana, 1000, Slovenia 
                                                         Slovenian Olympic Committee, Ljubljana, 1000, Slovenia   
                                                                                                                                                 
                                                                                                                   Anja Carlsohn, PhD 
                                                                             professor for nutrition and home economics 
                                                                   University of Applied Sciences Hamburg, Germany 
                                                                                                                                                                                                                                      
                                                                                                            Peter Soeters, MD, PhD 
                                                                                                  emeritus professor of surgery 
                                                                    Maastricht University Medical Center, Maastricht,  
                                                                                                             6200, The Netherlands 
                               
                     
                    Learning Objectives 
                         To present basic terminology in sports clinical nutrition;  
                         To understand that the key goal of training is to enable the body to develop metabolic 
                          efficiency and flexibility, while specific nutritional strategies for competition are aimed 
                          at providing adequate substrates to support energy demands and cognitive function; 
                         To understand that nutritional goals for active adults and competitive athletes are not 
                          static and they require a complex knowledge of sports physiology, metabolism and 
                          nutrition to create a nutritional strategy for training and competition;  
                         To understand how to apply existing sports nutritional recommendations for planning 
                          specific nutritional strategies in sports nutrition;  
                         To understand negative clinical and performance effects of Relative Energy Deficiency 
                          Syndrome (RED-S).  
                           
                    Contents 
                    1.    Introduction  
                    2.    Terminology and basic considerations in sports clinical nutrition 
                          2.1. Terminology  
                          2.2. Aerobic and anaerobic (non-oxidative) metabolism 
                          2.3. Physique and energy demands of different athletes  
                          2.4. Periodization of nutritional strategy 
                    3.    Nutritional support in sports 
                          3.1. Energy requirements  
                          3.2. Nutrient intake recommendations  
                              3.2.1. Carbohydrate intake 
                              3.2.2. Protein intake 
                              3.2.3. Fat intake 
                         3.3. Nutritional strategies to optimize recovery 
                    4.    Clinical issues concerning the nutrition of athletes 
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                      4.1. Weight management, female athlete triad and eating disorders 
                      4.2. Gastrointestinal distress 
                      4.3. Iron deficiency and iron deficiency anaemia 
                 5.   Summary 
                 6.   References 
                       
                 Key Messages 
                 •    Exercise is a major challenge to whole-body homeostasis; 
                 •    Physiological and metabolic responses to exercise are similar to the general stress 
                      response  and  provoke  widespread  perturbations  in  numerous  cells,  tissues,  and 
                      organs,  as  a  response  to  the  increased  metabolic  activity  of  contracting  skeletal 
                      muscles;  
                 •    To meet the exercise challenge, multiple integrated and often otherwise redundant 
                      responses operate to diminish the homeostatic stress; 
                 •    The metabolic response to exercise is dictated by energy demand and duration of 
                      physical activity and substantially influences the ability to produce muscle power; 
                 •    The intake of energy and macronutrients must be personalized according to athletes’ 
                      training  plans  as  well  as  to  individual  responses  to  specific  training  stimuli  and 
                      characteristics;  
                 •    Ensuring strategic energy and nutrient availability at critical training points is not only 
                      important for optimal training, regeneration and competitive performance but also for 
                      immune system protection, and prevention of injuries, overreaching and overtraining; 
                 •    Energy availability, which considers energy intake in relation to the energy cost of 
                      exercise,  sets  an  important  foundation  for  health  and  success  of  sports  nutrition 
                      strategy. 
                                                    
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        1.  Introduction 
         
        Nutritional strategies for active adults and competitive athletes are based on scientific 
        findings regarding the underlying mechanisms of various physiological phenomena induced 
        by  exercise,  including  the  recovery  process.  Optimal  interaction  of  diet  and  exercise 
        provides a powerful tool to enhance metabolic health and sports performance.   
        The metabolic demands of exercise are dictated by the energy demands and the duration 
        of physical activity as well as by numerous issues relating to the speed, force, duration, 
        and intensity of muscle contractions. In addition, the total muscle mass engaged in the 
        activity  must  also  be  considered  for  a  complete  understanding  of  the  physiological 
        responses to exercise. The resulting metabolic demands have to be met within a limited 
        disruption of homeostasis. 
        In recent years, knowledge in the field of sports sciences has grown immensely and created 
        a vibrant environment of applied research in sports nutrition. The integration of scientific 
        findings with the insights from the field of applied nutrition on how to cover individual 
        metabolic needs of exercise has led to an increasingly sophisticated practice of sports 
        nutrition. The times of recommending a “sports diet” or using fixed amounts of nutrients 
        in any sports or exercise activities are over. Nutritional support should be adjusted to the 
        specific demands of every athlete. The strategically adjusted consumption of key nutrients, 
        depending on the specific needs of an individual, aims at enhancing athletic performance 
        and regeneration, thus allowing an athlete to reach his or her full genetic potential and 
        benefit from physical activities which vary in duration and intensity (1).  
        Currently, an appropriate strategy for nutritional support is based on evidence provided by 
        general scientific recommendations and then applied to various forms of endurance and 
        dynamic voluntary exercise as well as to specific forms of power and strength sports. 
        Therefore,  the  guidelines  for  clinical  sports  nutrition  represent  various  general 
        recommendations for  energy  intake,  amounts  and  composition  of  nutrients  and  fluid 
        intake, and also specific recommendations for the type of sport and/or exercise activity 
        and for different phases in the training process (Fig. 1).  
        However, the most important part of sports nutrition is to enable an athlete to turn his or 
        her nutritional goals into practical use of foods, fluids, and sport nutrition supplements. As 
        the dietary intake of food has immediate as well as long-term effects on the athlete’s well-
        being, health, and athletic performance, the nutritional strategy should be tailored also in 
        accordance with other factors that could potentially influence food choices and composition. 
        These issues are influenced by the athletes’ lifestyle, food preferences, personality and 
        their  social  and  cultural  circumstances.  In  addition,  the  culture  of  a  specific  sport, 
        interactions  between  athletes  and  opinions  of  coaches  and  trainers  may  influence 
        nutritional  beliefs  and  attitudes  towards  food.  Therefore,  the  content  and  the  way  of 
        delivering sports nutritional education must be tailored to individual athletes but in the 
        context of their specific group.  
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                   Fig. 1 Personalized sports nutritional strategy 
         
        2.  Terminology  and  Basic  Considerations  in  Sports  Clinical 
          Nutrition 
        2.1 Terminology 
         
        The term exercise is defined as any activity involving force and power production by 
        voluntary  coordinated  activation  of  the  appropriate  skeletal  muscles  (2).  However, 
        voluntary exercise is more than just an orchestrated assembly of muscle contractions; 
        whole-body, voluntary exercise induces a range of additional physiological responses that 
        are critical for muscle performance enhancement and development of movement skills.  
        Importantly, many effects observed in animals and isolated systems frequently differ from 
        those seen in humans in vivo, so care should be taken when extrapolating responses from 
        one set of conditions or a given experimental model to another (3).  
        Endurance exercise represents a spectrum of rhythmic exercises like walking, running, 
        cycling, swimming, triathlon, skiing, and others. Within these sports, there are different 
        disciplines. During sustained rhythmic exercise like cycling or running, the contraction 
        times are short, there is little disruption of muscle blood flow and minimal perturbations in 
        blood pressure (BP).  
        Intense exercise events that require high power outputs of relatively shorter duration for 
        success are considered as power sports (4). Typical power sports are medium-distance 
        running,  track  cycling,  Olympic  rowing,  canoeing/kayaking,  and  swimming  (4).  An 
        isometric or static contractions of high force but short duration may compress blood vessels 
        within the contracting musculature and limit blood flow and oxygen delivery to those 
        muscles while simultaneously increasing BP.  
        Power is defined as the amount of work performed per unit of time (2). It reflects the 
        ability  to  exert  maximum  muscular  contraction  instantly  or  in  an  explosive  burst  of 
        movements. The two components of power are strength and speed (e.g. jumping or a 
        sprint start). From the energetic, and also nutritional, point of view, it is important to 
        understand that power is the rate at which work can be performed or the rate of the 
        transformation of metabolic potential energy to work and/or heat.  
        Power in sport can be determined for a single body movement, a series of movements, or 
        a large number of repetitive movements. It can be determined instantaneously at any point 
        in a movement, or averaged for any portion of a movement or bout of exercise (3). In 
        complex human motions, the maximum output of mechanical power is reached with 
        approximately 50% of the maximum force and velocity of a given athlete (5).           
        Optimal power output demands effective muscle coordination and mechanical efficiency of 
        limb movement, meaning that optimal sports performance requires the consideration of 
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