Chapter 11 - Nutrition for Physical Activities.docx

Chapter 11: Nutrition for Physical Activity Energy is required to move our bodies. The longer and more intense the activity is, the more energy required. In- tensity and duration also aﬀect which fuel source is preferentially used. Healthy nutrition can supply some of these fuels and support the various non-energy needs of athletes. Active individuals have a higher need for water, carbohydrates, proteins, electrolytes and antioxidants. The consumption levels and timing of these nutrients can support both perfor- mance and recovery. By the end of this chapter, you will be able to: Diﬀerentiate between the diﬀerent forms of physical activity. Outline how and when fuels are used with respect to the intensity and duration of exercise. Outline the additional nutritional needs for those participating in higher levels of activity. Give nutritional recommendations for before, during and after exercise. Outline the uses, benefits and risks of various ergogenic aids. Physical activity is an umbrella term for voluntary body movements that expend energy. There are several diﬀer- ent forms of physical activity (Figure 11.1). Exercise is a type of physical activity that is planned and structured and whose goal is to enhance fitness. Fitness is the body’s ability to respond to tasks that are physically demanding without being exhausted. The more challenging an activity is, the more likely it is to build fitness. Sport is also planned, structured and can promote fitness, but has a competitive element and fitness may not be its main objective. Since this chapter looks at the nutritional needs of those participating in both exercise and sport, these terms will be used interchangeably. Figure 11.1: Forms of physical activity. In addition to sport and exercise, we may also participate in occupational activity to support the demands of our job or leisure activities. Active living can further support fitness and overall health. Active living is a lifestyle that includes multiple opportunities for engagement in physical activity throughout the day. Cleaning the house, walking the dog, tak- ing the stairs, dancing to our favorite song and gardening (Box 11.1) are all examples of active living. Box 9.1: An Indigenous lens: Community gardens. Gardening is an excellent example of a practice that promotes both mental health and active living. Beyond its impact on physical ac- tivity levels, the direct interaction with natural environments that occurs during gardening may have further health benefits including reducing the risk of depression and anxiety (Beyer et al., 2014) as well as obesity (Lachowycz & Jones, 2011). Community gardens may provide a further advantage to health by building cohesive communities and by allow- ing people to engage in culturally relevant practices, while decreasing the risk for food insecurity (Lovell et al., 2014). Recall from Chapter 2 that the BC First Nation’s Health Authority recommends increasing the number of community gardens so as to “bring the community togeth- er… promote healthy eating and provide nutritious foods for community events”(First Nations Health Authority, 2014). An example of one such community garden is Harmony Garden (X̱wemelch’stn pen̓em̓ áy) run by Kultsia Barbara Wyss, T’uy’t’tanat Cease Wyss, and Senaqwila Wyss, from the Squamish First Nation. Harmony Gardens, which has been run- ning since 2007, promotes Indigenous food sovereignty by celebrating Indigenous food practices and building community. A section of Harmony Garden is devoted to Indigenous plants such as salmon berries, huckleberries and Devil’s club, the latter of which has been used for its medicinal properties. In addition, part of the garden has been laid out in a way that represents the colours of the Medicine Wheel, illustrating the unity of the people that would use the garden. It also has a gazebo for public gatherings including luncheons and workshops. The garden, much like other community gardens, shows how the various factors that aﬀect health, such as physical activity, diet, mental health, community and relationships are interconnected. By learning from these practices and engaging in them, we can appreciate their many physical, mental and social benefits. As Barabara Wyss comments, “You can feel the peacefulness of the place, and it is quite enjoyable” (Harmony Garden - Community Food Security Project, 2012). For adults aged 18–64, the World Health Organization (WHO) recommends 150 min of moderate physical activ- ity or 75 min of vigorous physical activity per week in intervals of 10 min or more (World Health Organization, n.d.). For further benefits, moderate-intensity activities can be increased to 300 min per week and vigorous activities to 150 min. The WHO also recommends incorporating muscle-strengthening activities at least two times per week. These recom- mendations are more likely to lead to the many positive health eﬀects of physical activity (Figure 11.2). Indeed, physical activity is one of the best things we can do for our physical, mental and social wellbeing. Proper nutrition can support our physical activity habits and complement many of these benefits. Figure 11.2: Beneﬁts of regular physical activity. Energy intake provides fuel for our exercising muscles. Recall from Chapter 3 that our energy-yielding nutrients are metabolized to form ATP. The muscle protein myosin uses ATP so muscle contractions and body movements can oc- cur. Carbohydrates and lipids are the body’s two preferred fuels for physical activity. While protein also provides energy, that is not its main role. Protein is, however, critical for the growth and repair of tissue needed to support activity. We preferentially use diﬀerent fuels at diﬀerent stages of exercise. The preferred fuel depends, in part, on whether aerobic or anaerobic metabolism is required. Aerobic activities are moderate-intensity activities that can typically be performed for longer periods of time. They increase our heart and breathing rates, but not so much that the activity is unsustainable. Examples of aerobic activities include walking, running and cycling. Aerobic means with oxygen. Since these are moderate-intensity activities, after an initial adjustment the body can adequately deliver enough oxygen to meet the demands of aerobic metabolism. Aerobic metabolism is the cellular respiration pathway discussed in Chapter 3 that leads to the production of more than 30 molecules of ATP (Figure 11.3). Carbohydrates, lipids and proteins can all be used for aerobic metabolism. Figure 11.3: Aerobic vs. anerobic metabolism. Conversely, anaerobic activities use anaerobic metabolism. Anaerobic metabolism is the metabolic pathway that can occur without oxygen and that leads to the production of lactate and a small amount of ATP. Anaerobic metabolism is required in the first couple minutes of exercise as the body adjusts to adequately deliver oxygen to the tissues. Intense activities, such as sprinting and weightlifting, also rely on anaerobic metabolism as there is not enough oxygen to meet their high demands. The only dietary fuel that can be used for anaerobic metabolism is glucose. To supplement this need, the tissues have minute amounts of ATP and creatine phosphate that can also be metabolized anaerobically. The body simultaneously uses multiple fuel sources. However, depending on the stage of exercise, one fuel will be used preferentially over others. After exercise begins, it takes our bodies a couple of minutes to determine how much oxygen to send to which tissues. This stage is accordingly anaerobic, which limits the fuels that can be used (Figure 11.4). Figure 11.4: Anaerobic fuel use during the ﬁrst two minutes of exercise. Our muscle cells have a minimal amount of ready-to-go ATP that can be used for fuel when exercise begins. Re- call that when the third phosphate group is separated from ATP, it becomes ADP. This leads to the release of energy that can fuel muscle contraction. This ATP is used up within the first 2 seconds of exercise. If activity continues, a new bond will need to be formed between ADP and a phosphate group to replenish ATP. Creatine phosphate, also known as phosphocreatine, can replenish ATP by transferring its high-energy phos- phate group to ADP (Figure 11.5). Creatine is obtained from animal products, mostly beef and fish, and can also be produced by the liver and kidneys. This creatine system is the main energy pathway that fuels activities from the point ATP is depleted to approximately the first 10 seconds of exercise. ATP and the creatine phosphate-ATP energy systems provide a quick, maximal burst of ATP before other long-term fuels are recruited. Figure 11.5: Creatine phosphate replenishes ATP. The body is in an anaerobic state for approximately the first 2 minutes of exercise (Figure 11.4). Since ATP and creatine phosphate levels drop dramatically after the first 10 seconds, another anaerobic fuel source is needed. Anaer- obic glycolysis, the anaerobic metabolism of glucose, takes up this role. This process is also known as the short-term energy system and the lactic acid system. Recall that under anaerobic conditions, glucose is metabolized into pyruvate. However, pyruvate cannot be metabolized into acetyl CoA unless oxygen is present. Pyruvate instead produces lactate (the conjugate base of lactic acid) and ATP (Figure 11.3). While this process produces much less ATP, it does so quickly and much faster than the aerobic fuel systems (Melkonian & Schury, 2020). However, this fuel system can only dominate for a limited time, as it promotes an acidic environment that cannot be sustained. This is experienced as a burning sen- sation when sprinting or weightlifting. Due to the limits of anaerobic glycolysis, the body shifts into aerobic metabolism as oxygen becomes sufficient. After the first 2 minutes of moderate-intensity activity, the body is delivering an appropriate amount of oxygen to meet its energy demands. Accordingly, two new fuel systems dominate: aerobic glycolysis and lipid metabolism (Fig- ure 11.6), the latter of which is also known as lipid oxidation or fat oxidation. Protein can also be metabolized aerobically, but amino acid metabolism contributes a minor fraction to our overall fuel use. In minutes 2–20 of moderate-intensity exercise, aerobic glycolysis is the dominant fuel source. Blood glucose and muscle glycogen supply this need for glucose. During this time, the body starts ramping up lipid metabolism, which will become the preferred fuel source after 20 minutes of exercise. Since glucose is limited, after 20 minutes of exercise we start dipping into our main fuel source for extended activities: the aerobic metabolism of lipids. Some of these lipids come from our intramuscular fat – triglycerides stored within muscle. However, most lipids used for lipid metabolism come from our fat cells, which release free fatty acids into the blood. Since fatty acids are continuously supplied by our fat cells, we can continue to fuel exercise for an extended period. Lipids are a great fuel source for physical activity since each gram provides about 9 kcal of energy, compared to the 4 kcal of energy that is generated from carbohydrate and protein metabolism. Protein can help fuel aerobic activities, but it is never the main fuel source. In general, protein only generates a maximum of 10% of the total energy needed for prolonged exercise (Brooks, 1987). This is because it is wasteful to use amino acids to generate ATP. Recall from Chapter 3 that amino acids must lose their nitrogen-containing amino group in order to enter cellular respiration. The body would rather use an entire amino acid for the growth and repair of tissues than remove part of an amino acid and use it for fuel. Accordingly, protein is an important part of an athlete’s diet for tissue recovery and growth, but not as a fuel source. In addition to duration, the intensity of exercise can aﬀect the preferred fuel source (Figure 11.7). Low- to moder- ate-intensity activities put us in the aerobic zone. That means that the preferred fuel source will depend on the duration of the activity, as discussed above. For moderate activities lasting longer than 20 minutes, lipids are the preferred fuel Figure 11.7: Fuel use vs. exercise intensity. High-intensity activities, such as sprinting, weightlifting and plyometrics, are considered anaerobic activities. While aerobic metabolism still occurs during these activities, anaerobic glycolysis is the main energy source. According- ly, high-intensity activities rely on glucose for fuel. On certain cardio machines found in gyms, the intensity of activity is often separated into the cardio zone or the fat-burning zone. This concept is misleading, as it refers to the preferred fuel source, not the total amount of energy that is being lost from the body (Box 11.1). Table 11.1 summarizes which fuel is preferentially used during diﬀerent durations and intensities of exercise. Table 11.1: Intensity and duration vs. fuel source. Box 11.1: The misleading fat-burning zone. Treadmills and other cardio machines sometimes suggest training programs that put us into zones. The two most common are the cardio zone and the fat-burning/weight-loss zones. It is logical to assume that compared to the cardio zone, exercising in the fat-burning/weight-loss zone provides greater reductions in body fat. However, these terms refer to the preferred fuel type, not the likelihood of an activity to alter fat mass. The fat-burning/weight-loss zone is a moderate-intensity zone in which lipid metabolism is the preferred fuel source. However, this does not mean that we will burn more body fat in this zone. Recall from Chapter 10 that the main factor that determines fat loss is establishing and maintaining a caloric deficit. Accord- ingly, whichever promotes the greatest energy expenditure is most likely to promote a caloric deficit and reduction in body fat. The cardio zone is a high-intensity zone. While less fat is metabolized for fuel in this zone, a greater total amount of calories is burned (Figure 11.7). Thus, if we want to maximize energy expenditure, we will burn more total calories in the cardio zone than the fat-burning zone. However, it is more difficult to maintain higher-intensity activity for a long time. Therefore, if we exercise for longer at a lower intensity, we can burn equal or higher amounts of energy at a moderate intensity than a higher one. Again, it depends on the situation. For an equal exercise duration, however, exercising within the cardio zone is more likely to promote a caloric deficit. Athletes vary in age, gender and size and have diﬀerent training schedules and goals. Accordingly, it is best to tailor a nutrition program to the specific needs of an athlete. A dietician specializing in sports nutrition or a registered sports nutritionist can be consulted to build an individualized plan. This may be especially important for those competing in more competitive activities. In this section, we will look at general considerations for all athletes. These are summa- rized in figure 11.8. Figure 11.8: Summary of additional nutrient requirements for athletes. Sufficient energy intake is required to fuel activities. However, when planning for energy intake, we might also need to consider an athlete’s preferred energy balance. For instance, some sports like wrestling and weightlifting may require a higher body weight for maximum performance, while others like running or gymnastics may require a lower weight. Regardless, a good place to begin is for an athlete to determine how much energy they burn each day using the estimated energy requirement (EER) calculation outlined in Chapter 2, activity logs or energy-tracking software. If a person is trying to gain weight, they should consume energy in excess of their EER. If they are trying to lose weight, they should consume energy at a deficit to their EER. If they want to maintain weight, their energy intake should closely match their EER. While EER is helpful for estimating energy requirements, it does not consider how training inten- sities and durations can ﬂuctuate from day to day. On days when activity levels are higher, a higher energy intake may be required; the converse is also true. Another method that can be used to explore the energy needs of athletes is the concept of energy availability (EA). EA is calculated by subtracting our exercise expenditure from our energy intake. For example, if a person ate 2000 kcal in a day and burned 500 kcal through exercise, their EA would be 1500 kcal. This concept is important because it considers how much energy is left over to meet our other needs once we take exercise into account. Individuals with low EA are more likely to have health issues such as impaired bone health, hypoglycemia, low heartrate as well as eating dis- orders and depression (Melin et al., 2019). Accordingly, we need to make sure we are consuming enough energy to meet both our activity needs and the body’s foundational needs. Carbohydrates are a key fuel for both aerobic and anaerobic exercise. Recall that muscles use glucose for both types of activity, but a limited amount is available. As blood glucose and muscle glycogen decrease, so does an athlete’s ability to maintain the intensity and output needed for their activity (Coyle et al., 1986). Consuming adequate carbohy- drates can maximize glycogen stores and contribute to exercise performance. Indeed, glucose provides a higher yield of ATP over other fuels per volume of oxygen (Spriet, 2014). Glucose has also been established to maximize time to ex- haustion in athletes, and may play a role in muscle’s adaptation to exercise (Philp et al., 2012). Moreover, the brain and red blood cells, both of which are important for performance, rely on glucose as a fuel. Considering the strong evidence base to support carbohydrate’s importance to exercise nutrition, higher intakes are recommended for increasing levels of activity (Table 11.2) (Thomas et al., 2016). Meeting carbohydrate recommendations for diﬀerent levels of activities can help athletes replenish and maximize their glycogen stores, which many athletes fail to do (Burke et al., 2001; Murray & Rosenbloom, 2018). Table 11.2: Daily carbohydrate recommendations for athletes. Protein is essential for the growth and repair of tissue, including the synthesis of muscle. In the 24 hours follow- ing resistance exercise, muscle protein synthesis increases, which is coupled with an increased need for dietary protein (Burd et al., 2011). Accordingly, athletes require sufficient dietary protein to facilitate the repair and growth of these and other body proteins (Thomas et al., 2016). Protein recommendations increase from an RDA of 0.8 g/kg/day up to a range of 1.2–2.0 g/kg/day for athletes. The actual amount depends on training duration and intensity. High-quality dietary pro- tein that provides all the essential amino acids is recommended. While lipids are the primary fuel source for activities lasting more than 20 minutes, the body stores lipids and extra dietary consumption is not typically recommended for an athlete, especially if it displaces carbohydrates in the diet (Thomas et al., 2016). Conversely, fat restriction below the lower end of the acceptable macronutrient range for fat (20% of calories) is also not recommended, as it can impair the bioavailability of fat-soluble vitamins and essential fatty acids (Institute of Medicine, 2005). Vitamins and minerals regulate many physiological processes that are critical for exercise. Accordingly, micronu- trient deficiencies can compromise athletic performance and recovery. While adequate micronutrient status is important for everyone’s health and wellbeing, athletes have additional micronutrient considerations. Recall from Chapters 8 and 9 that calcium and vitamin D both contribute to bone health. Exercise, especially resistance exercise, promotes the mineralization of bones, which requires an adequate supply of these micronutrients. Accordingly, to support bone health, athletes should ensure adequate intake of both calcium and vitamin D. This is espe- cially important for those with lower EA who may be lacking in these and other micronutrients (Thomas et al., 2016). In addition to its role in bone health, vitamin D has emerged as a potential mediator of muscle health. A system- atic review of five randomized control trials found that vitamin D3 supplementation improved muscle strength (Chiang et al., 2017). However, another systematic review of 13 randomized control trials found that supplementing vitamin D did not significantly improve performance (Farrokhyar et al., 2017). This is a newer area of investigation and more research is needed to determine whether vitamin D supplementation provides a performance advantage. Nonetheless, for bone and overall health, athletes should ensure adequate vitamin D status (Farrokhyar et al., 2015). Iron is an essential component of the two proteins hemoglobin and myoglobin, which help transport oxygen in blood and muscle, respectively. Iron deficiency compromises oxygen delivery and can progress to iron deficiency anemia, which promotes tiredness and decreased exercise capacity. Even without anemia, iron deficiency can compromise muscle function and athletic ability (Lukaski, 2004). Further, athletes have a higher iron need and are at a higher risk for iron defi- ciency, especially if their heme iron intake is low. Accordingly, it is imperative that athletes achieve adequate iron status to support performance and health. Increasing iron intake from food is the primary strategy for reducing the risk of iron deficiency in athletes (Thomas et al., 2016). Recall from Chapter 9 that heme iron from animal products is more bioavailable than nonheme iron found in plant products. Animal products are also advantageous because they do not contain phytates, oxalates or tannins, which can compromise iron absorption in plants. Consuming iron sources with vitamin C can improve iron absorption. Iron supplements may also be used, but they are recommended as a second course of action due, in part, to their ability to promote gastrointestinal distress (Peeling et al., 2014). Exercise increases the production of free radicals. Free radicals can oxidize and damage muscles and impair their function (Peternelj & Coombes, 2011). Antioxidant activity can mitigate this damage. However, athletes may have lower total antioxidant capacity (Watson et al., 2005). Accordingly, ensuring adequate antioxidant intake from foods is recom- mended (Thomas et al., 2016). Recall from Chapter 8 and 9 that various micronutrients are themselves antioxidants or contribute to antioxi- dant activity by acting as cofactors. Foods rich in vitamins E, C, provitamin A, selenium, zinc, sulfur, magnesium and the B vitamins can help increase an athlete’s total antioxidant capacity. A varied diet rich in whole foods can supply these antioxidants. Conversely, antioxidant supplements, especially when they exceed the upper limit, have not been shown to improve athletic performance, unless they reverse a deficiency (Lukaski, 2004). Little to no change will be seen in an athlete who overconsumes vitamins and minerals beyond required levels. The timing of nutrient intake is an important determinant of exercise performance and recovery (Hawley & Burke, 1997). For a person who exercises for an hour or less, a significant change in dietary carbohydrate prior to exercise is typically unnecessary. However, for those who exercise for longer, a pre-exercise meal that contains carbohydrates is the best established way to promote exercise performance (Ormsbee et al., 2014). Specifically, the American College of Sports Medicine and the Canadian and American dietician organizations recommend consuming 1–4 g/kg body weight of carbohydrate 1–4 hours before exercising for more than 60 minutes (Thomas et al., 2016). They recommend consuming easily digestible carbohydrate-rich sources that are low in fibre and fat. These maximize performance while lowering the potential for digestive stress. For those competing in longer events, glycogen supercompensation may be indicated. It is common for marathoners and those participating in endurance competitions to load up on pasta or pancakes the night before their big event (Figure 11.9). This is glycogen supercom- pensation, commonly known as carbo-loading. This strategy aims to maximize glycogen stores to promote optimal carbohydrate fuel use during endurance events. Indeed, this strategy has been shown to increase the time to exhaustion as well as overall per- formance (Coyle et al., 1986; Hawley et al., 1997). To carbo-load, 10–12 g/kg body weight of carbohydrate is recommended per day for the two days preceding the activity (Thomas et al., 2016). Figure 11.9: Consuming pasta the night before an endurance event can contribute to glycogen supercompensation To reduce the risk of dehydration, sufficient water intake is also recommended before exercise. Individual water needs vary according to physiology and the environmental temperature. However, consuming 5–7 mL/kg body weight of water at least 4 hours prior to exercise can help prevent dehydration in most individuals (Thomas et al., 2016). During exercise, we lose water through sweat and exhalation, and we must rehydrate to maintain water bal- ance. Regardless of duration, water intake during activity is recommended to prevent dehydration, which can negatively aﬀect both performance and health (Figure 11.10). As little as a 2% drop in body weight due to dehydration is enough to increase perceived eﬀort and impair output (American College of Sports Medicine, Sawka, et al., 2007). Water needs vary by individual. Drinking water liberally during exercise may be sufficient. To be sure, we can weigh ourselves before and after exercise to determine our level of dehydration. Every kilogram of weight lost is equal to a litre of water lost (Amer- ican College of Sports Medicine, Sawka, et al., 2007). Therefore, if half a kilogram is lost between the beginning and end of activity, that means we have lost a half litre (two cups) of water. Figure 11.10: Negative eﬀects of dehydration. Longer bouts of exercise lead to more sweating and more ﬂuid and electrolyte losses (American College of Sports Medicine, Sawka, et al., 2007; Cheuvront et al., 2003). If athletes only replace water and not electrolytes, they are at higher risk for hyponatremia and other electrolyte imbalances (Montain et al., 2006). Endurance athletes competing in hotter environments are at higher risk for the negative eﬀects of ﬂuid and electrolyte loss as well as for the development of heat illness. Recall from Chapter 4 that heat illness is associated with an increase in body temperature and can lead to dizziness, muscle cramping and collapse (American College of Sports Medicine, Armstrong, et al., 2007). Accordingly, for longer activities, especially those in a hotter environment, both ﬂuid and electrolyte replacement is imperative. Since sweating rates vary dramatically, so will water and electrolyte needs. Consuming 375–500 mL of water every 10–15 minutes will typically be enough to reduce dehydration (Kerksick et al., 2017). For longer events, sports drinks or electrolyte powders can help replenish lost electrolytes. People who exercise for a moderate amount of time (e.g., 30–60 minutes) or at a lower intensity do not usually require extra fuel during exercise. Indeed, they will typically have enough blood glucose, muscle glycogen and stored lip- ids to sustain exercise. Furthermore, eating during exercise can promote gastrointestinal side eﬀects such as indigestion. However, for endurance activities lasting more than 60 minutes, including stop and start events like soccer, 30–60 g/hour of easily digested carbohydrate is recommended (Thomas et al., 2016). This can be increased to 90 g/hour for ultra-en- durance events lasting more than 2.5 hours. Sports gels and candies are easy to carry and can help meet these needs. Also, sports drinks typically contain simple carbohydrates and can also help meet the additional water and electrolyte needs of longer activities Following exercise, we have three nutritional priorities: promoting the growth and repair of muscles, replenishing lost ﬂuids and electrolytes, and refilling glycogen stores (Figure 11.11). In the 24 hours following an exercise session, muscle protein synthesis increases, as does our sensitivity to dietary protein (Thomas et al., 2016). In the first two hours following exercise, consuming high-quality protein sources maximizes muscle protein synthesis (Kerksick et al., 2017). A protein intake of 0.25–0.3 g/kg body weight that includes about 10 g of essential amino acids is recommended during this timeframe (Thomas et al., 2016). Milk-based protein is often recommended as a high-quality protein source following exercise. It is easily digested, contains water, electrolytes and carbohydrates and is especially high in the branched-chain amino acid leucine. Several studies have shown that consuming milk-based protein after resistance exercise is associated with increases in muscle strength beyond that evi- denced with other protein sources (Hartman et al., 2007; Josse et al., 2011). In the 30–40 minutes following exercise, both glucose transport into muscle cells and glycogen synthesis increase (Murray & Rosenbloom, 2018). Consuming a post-exercise meal that includes whole sources of carbohydrate can help promote this glycogen synthesis. If an athlete has less recovery time (<8 hours) before their next bout of exercise, a more aggressive carbohydrate refuelling protocol is indicated. In this case, consuming 1.2 g/kg body weight for the first hour following exercise is recommended (Kerksick et al., 2017; Thomas et al., 2016). Sources with a high glycemic index can be included to maximize glycogen recovery. If a meal that contains whole foods is consumed following exercise, it will most likely replace electrolyte loses. To replenish ﬂuids, any post-exercise drop in body weight should be addressed by consuming the appropriate amount of water lost. Athletes, especially those competing in elite sports, are more likely to use ergogenic aids, which are common- ly known as performance enhancers (Knapik et al., 2016; Maughan et al., 2007). These products are taken in order to improve output, muscular gains and/or recovery. While some ergogenic aids may be beneficial to an athlete, a discussion with a sports nutritionist or dietician should precede consumption so the potential for negative side eﬀects is minimized. Creatine supplements (Figure 11.12) are one of the most popular nutritional supplements for athletes (Kreider et al., 2017). They help maximize muscle cre- atine stores, which are not typically saturated. Indeed, these supplements have been shown to boost the levels of creatine within muscles, thus providing more fuel for anaerobic activities. Creatine supplement may promote performance in high-intensity activities, especially those performed in short intervals (Bemben & Lamont, 2005; Bird, 2003; Kreider et al., 2017). Evidence also supports the potential benefits of creatine for enhancing muscle mass, glycogen synthesis, anaerobic threshold and exercise recovery (Kreider et al., 2017). The International Society of Sports Nutrition recommends a supplementation protocol of 5 g of creatine mo- nophosphate four times per day for five to seven days to fill creatine stores (Kreider et al., 2017). Following this, 3–5 g of creatine monophosphate a day can be continuously taken to maintain stores. Adding creatine to a carbohydrate and protein beverage may further promote ameliorated training responses (Kreider et al., 2017). Since creatine supplements are not typically produced from animal products, they can also be consumed by vegans and vegetarians. This may be particularly advantageous, since vegetarians tend to have lower muscular stores of creatine and show greater gains with supplementation (Benton & Donohoe, 2011; Burke et al., 2003). The most common side eﬀect of creatine use is weight gain due to water retention. Muscle cramps and gastro- intestinal symptoms, such as diarrhea and abdominal discomfort may also occur, but otherwise more than 1000 studies on creatine use have found no significant adverse eﬀect (Francaux & Poortmans, 2006). When deciding whether to take creatine supplements, we should consider our specific goals as well as the potential side eﬀects and cost of using supple- ments. Protein supplements are consumed as protein powders or as individual or grouped amino acid supplements. They are mainly taken to enhance recovery and promote muscle growth and repair. Indeed, adequate protein intake is necessary for the protein synthesis and tissue repair that occurs after exercise. In North America, adequate protein intake can easily be achieved though diet alone. However, commercial protein supplements are typically easy to consume and are often mixed with other nutrients that may be lacking in an athlete’s diet. Recall from Chapter 7 that supplements of the branched-chain amino acids leucine, isoleucine and valine are sometimes taken for their ergogenic potential. Indeed, they have been shown to reduce low to moderate amounts of muscle damage in resistance athletes (Fouré & Bendahan, 2017). They have also been shown to improve muscle protein synthesis (Jackman et al., 2017) as well as reduce soreness after more demanding bouts of exercise (Rahimi et al., 2017). We can purchase branched-chain amino acids at supplement stores, or we can simply consume a diet that contains high-quality protein to meet our needs. Caﬀeine is not a nutrient; it is a psychoactive drug. For decades, it has been used within sport for its mild stimulating eﬀects (Figure 11.13), and for good reason. An umbrella review of other systematic reviews concluded that caﬀeine improved exercise performance in a number of ways (Grgic et al., 2019). Muscular strength and endurance, aerobic endurance and anaerobic power all improve with caﬀeine intake. Benefits are more significant with aerobic activities as compared to anaero- bic ones. However, most studies into caﬀeine’s eﬀects focus on younger males. More studies may provide insight into whether these eﬀects are the same in women as well as middle-aged and older individuals. The International Society of Sports Nutrition states that caﬀeine has an enhancing eﬀect when consumed in doses of 3–6 mg/kg (Goldstein et al., 2010). They further assert that caﬀeine’s ergogenic eﬀect is most pronounced when consumed in a state that does not include water. Conversely, water-based caﬀeine sources, such as coﬀee and tea, may promote gastro- intestinal eﬀects that negatively impact exercise performance. Surprisingly, even though caﬀeine is a diuretic, it has not been found to negatively impact ﬂuid balance during exercise. Figure 11.13: Caﬀeine is a popular ergogenic aid. Figure 11.14: Hydroxymethylbutyrate supplements. Hydroxymethylbutyrate (HMB) is a compound produced by the breakdown of the essential amino acid leucine (Figure 11.14). It has been shown to decrease protein breakdown while increasing protein synthesis (Holecek et al., 2009; Holeček, 2017). HMB has been studied for its potential eﬀects on athletic perfor- mance, muscular growth and recovery, lean body mass, strength, power and aerobic performance. After considering the available evidence, the International Society of Sports Nutrition asserted that HMB may improve recovery by decreasing muscular damage (Wilson et al., 2013). Further, they deemed this supplement as safe for use at a range of ages. An athlete suﬀering from a vitamin or mineral deficiency may see a significant improvement in their performance when vitamin and mineral intakes are increased to adequacy levels. This can be done through a well-planned and varied diet. However, little to no change will be seen in athletes who overconsume vitamin and mineral supplements beyond adequacy levels (Knapik et al., 2016; Thomas et al., 2016). Anabolic steroids, also known as anabolic-androgenic steroids, are synthetic compounds similar to the male hormone testosterone. They are taken by some athletes to increase muscle mass, strength and performance, but are not recommended. All major sporting and athletic organizations ban their use due to their side eﬀects and the unfair com- petitive advantage they oﬀer. Steroids promote a wide range of negative side eﬀects, including severe acne, increased risk of tendon issues and aggressive behaviours (Piacentino et al., 2015). There are also cardiovascular risks such as increased LDL, decreased HDL and increased blood pressure. They are also associated with psychiatric symptoms such as mood and schizophrenia-relat- ed disorders. Furthermore, they can promote fertility consequences, such as shrinking testes and decreased testosterone levels, which can last for months (Christou et al., 2017). Now that cannabis is legal in Canada, there is an increased focus on its eﬀects on a range of outcomes, including athletic performance. However, there are very few studies that examine these potential eﬀects. Reviews of the current research found no significant improvement in athletic performance with cannabis use (Kennedy, 2017; Trinh et al., 2018). Conversely, they were shown to have negative side eﬀects such as chest pain and a reduction in strength. More research is needed to establish the relationship between cannabis and athletic performance; for now, caution is recommended. Proper nutrition is important for exercise performance, recovery and improvement. Nutrition needs will vary depending on the individual and the specific activity being performed. People who exercise at lower frequencies, intensi- ties and durations may not need to significantly alter their nutrition. For them, a well-planned and varied diet of nutri- ent-dense whole foods is recommended. However, the more active an athlete is, the more important nutrition becomes. Athletes have higher requirements for energy, carbohydrate, protein, antioxidants, ﬂuids and micronutrients. Also, the timing of their consumption can provide an added benefit to performance and recovery. A dietician with a specialization in sports nutrition or a certified sports nutritionist can be consulted to provide a program that considers an athlete’s individual needs. Regular physical activity promotes physical, mental and social wellbeing. Exercise is a type of physical activity that is planned and structured and aimed at improving fit- ness. We preferentially use diﬀerent fuel sources for diﬀerent intensities and durations of exercise. Anaerobic activities such as high-intensity exercises rely primarily of anaerobic glycolysis. Creatine phosphate and ATP are also anaerobic fuels, but they are used up almost immediately. After the first 2 min of exercise, aerobic metabolism is preferentially used, which relies primarily on glucose and lipid metabolism. Protein is a minor fuel for exercise. A healthy pre-exercise meal focuses on providing enough ﬂuids and carbohydrates, while mini- mizing digestive issues. Beyond frequent hydration, most people do not require nutrient intake during exercise. Those ex- ercising for longer durations may benefit from carbohydrate and electrolyte intake during exercise. Following exercise, our priorities are consuming enough protein to promote muscle growth and recovery, replenishing ﬂuid and electrolyte loss, and refilling our glycogen stores through carbohy- drate intake. There are various ergogenic aids that may support athletic performance. Creatine monophos- phate, caﬀeine, HMB and branched-chain amino acids have a sufficient evidence base to support their use. To promote health, 150 min of moderate- to vigorous-intensity activity per week is recommended. This can be attained in bouts of at least 10 min. Athletes who participate in higher levels of physical activity can consult a certified sports nutrition- ist or sports dietician to create an individualized nutrition plan. Those exercising for hours a day should increase their total carbohydrate intake according to the protocol outlined in Table 11.2. Glycogen supercompensation can help maximize time to exhaustion in activities lasting more than 90 min. 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