Limb Symmetry Index: Chasing Equal Function
Introduction Over the past number of decades, the sports drinks industry has expanded at a phenomenal rate. In 2018 the global sports drink industry size was valued at a staggering 22.7 billion dollars and is predicted to rise to over 30 billion by 2026 according to the Fortune Business Insights Report (2021). Although sports drinks are designed for athletes it is estimated that 60% of males and 40% of females in the U.S. are regular consumers of sports drinks while 68% of Europeans have already consumed a sport or energy drink before adulthood. (Simulescu et al. 2019). This research highlights the target market of sports drinks targets a wide range of consumers from elite athletes to children. After establishing the sports drinks industry is far from being solely reliant on high-level sporting performers, it is plausible to suggest sports drink’s main priority could be on taste and image rather on function and performance. This blog post will outline the good qualities and benefits sports drinks can have on performance when used correctly. A detailed review of sports drinks ingredients will outline the benefits these ingredients have on performance during the right circumstances. The Benefits of Sports Drinks Prevent Dehydration: The initial aim of any beverage for sport is simple, to prevent dehydration. Mild dehydration, representing a 2% body weight loss can have negative effects on athletic performance (Bergeron, 2013). Dehydration increases core body temperature above normal levels resulting in increased fatigue and declines in strength, endurance, accuracy, and motivation (Bergeron, 2013). More extreme dehydration levels represented by a 7% to 10% loss of weight have more harmful consequences potentially leading to death (Jetton et al. 2013). Athletes exercising at a high intensity and/or in high temperatures can lose up to 2 litres of fluid per hour from sweating (Raizel et al. 2019). It is advised that athletes weigh themselves before and after their sporting activity and consume 1.5 litres of fluid for every 1kg weight loss to prevent dehydration (Haff & Triplett, 2015). Therefore, to maintain optimal body function and exercise performance it is advised to consume fluids every 10-15 minutes (Raizel et al. 2019). The presence of flavour in sports drinks may increase palatability and voluntary intake when compared with water, ensuring hydration levels are maintained (Kreider et al., 2010). 2. Provide Energy Since the 1980’s research has shown the positive effects carbohydrate has on endurance exercise events (Jeukendrup, 2011). The benefits of intaking carbohydrates during endurance exercise are plentiful. Some of the benefits include the prevention of hypoglycaemia as blood glucose levels are maintained and the prevention of glycogen depletion (Jeukendrud, 2011). Glycogen is the stored form of glucose in the muscles and liver and is the body’s preferred choice of energy during high-intensity exercise (Bean, 2017). A regular intake of carbohydrates during endurance exercise will help maintain carbohydrate oxidative levels too (Jeukendrup, 2011). Thus, carbohydrate intake will provide more energy allowing the body to exercise at a higher intensity and for a longer duration by sparing energy stores. The average person has approximately 1500 calories available to them from stored glycogen (Haff & Triplett, 2015). For example, if a marathon runner burns 1000 calories per hour and 70% is from carbohydrates (700 calories), they will begin to deplete their glycogen stores in a little over 2 hours without consuming carbohydrates during exercise. It is recommended to consume 30-90g of carbohydrate per hour or 1g of carbohydrate per minute to replenish used energy and delay time to exhaustion (Haff & Triplett, 2015). As outlined, the benefit of carbohydrates during exercise is critical for the success of sports drinks. Sports drinks can be classed based on their carbohydrate quantity as either hypotonic, isotonic, and hypertonic. A hypotonic drink typically contains less than 4% carbohydrate or less than 4g per 100ml (Bean, 2017). Hypotonic drinks do not provide sufficient energy but provide a more tasteful alternative to water and can help athletes hydrate before a training session (Urdampilleta et al. 2015). An isotonic drink is typically the average sports drink and contains 4-8% carbohydrate or 4 to 8g per 100ml (Bean, 2017). Isotonic drinks have the same osmolality of the body’s fluids, meaning it contains a similar percentage of carbohydrate and electrolyte particles of the body, providing the ideal balance of refuelling energy and rehydrating as fast if not faster than water (Bean, 2017). Isotonic drinks are the best choice during exercise over 1 hour at replacing fluids lost and replenishing energy used while topping up electrolyte levels (Urdampilleta et al. 2015). Hypertonic drinks have a carbohydrate of approximately 10% and higher and are typically the standard “soft drinks”. Despite having a higher concentration of carbohydrates than isotonic drinks, they take longer to absorb due to having a higher osmolality rate and are not ideal for sports performance (Bean, 2017). Hypertonic drinks may aid at energy replenishment when consumed after a long duration activity rather than during exercise (Urdampilleta et al. 2015) Sports drinks that contain 6% to 8% carbohydrate which is in the isotonic range, allow for faster gastric emptying during exercise (Raizel et al. 2019). Sports drinks that have a blend of sugars (sucrose, fructose, glucose, etc.) making up the carbohydrate content promote greater carbohydrate absorption compared to having just one sugar present (Raizel et al. 2019). Different sugars are absorbed through different routes in the intestine and intaking a variety of sugars increases the likelihood of carbohydrates being supplied to the active muscles (Sousa et al. 2007). Evidence suggests that a sports drink with a carbohydrate profile of fructose to glucose ratio between 2:1 to 1:1 enhances gastric emptying, intestinal fluid absorption, and fluid delivery thus increasing carbohydrate oxidation resulting in improved endurance performance (Jeukendrup and Moseley, 2010).3. Electrolyte Balance A potential problem with just consuming water during prolonged exercise or exercise in a hot environment is hyponatremia. Electrolytes are lost through sweat with sodium chloride and potassium to a lesser degree being the most prevalent (Kilding et al. 2009). Athletes who are exercising at a high intensity or long duration and only hydrate with water can dilute their blood sodium to dangerously low levels (Haff & Triplett, 2015). This is hyponatremia and it can be measured by having a blood sodium level of below 130 mmol/L (Haff & Triplett, 2015). The symptoms of dehydration and hyponatremia are remarkably similar, including nausea, muscle cramps, headaches, and disorientation (Almond et al. 2005). Therefore, an athlete may mistakenly think they are dehydrated and continue to drink more water resulting in diluting blood sodium levels even further. If blood sodium levels fall below 120 mmol/L it can cause seizures and the potential risk of death (Almond et al. 2005). To avoid hyponatremia athlete’s fluid intake should not exceed sweat loss and sodium should be consumed during exercises ideally through a sports drink. The N.S.C.A recommended during prolonged activity in hot weather, adults should consume a drink containing 20 to 30 milliequivalents per litre of sodium and 2 to 5 milliequivalents per litre of potassium with a carbohydrate content between 5-10% (Haff & Triplett, 2015). Other Ingredients Other ingredients can be added to sports drinks mainly for taste and palatability reasons. Typically, if you enjoy the flavour and taste, the more you are going to drink and the more you are going to buy that product. Typically, vitamins, herbs, and amino acids are common in sports drinks (Raizel et al. 2019). Vitamins and herbs like green tea extract are added to sports drinks due to their proposed health benefits (Raizel et al. 2019). Amino acids are the building blocks of protein and it is proposed ingesting essential amino acids during exercise may prevent muscle protein breakdown, however, the evidence is mixed on this. (Raizel et al. 2019). Bicarbonate can be added to sports drinks too. Bicarbonate is a muscle buffer and counteracts the negative effects of hydrogen ions during high-intensity exercise when blood lactate is accumulating (Haff & Triplett, 2015). Bicarbonate can delay time to fatigue but many people find it difficult to tolerate as it can cause gastrointestinal distress (Raizel et al. 2019). More evidence is needed on the lesser-known ingredients in sports drinks to fully understand if they have a positive impact on performance. Side Effects Since the sugar content is quite high in sports drinks, when consumed in excess amounts it can lead to obesity, diabetes, and cardiovascular disease (Raizel et al. 2019). However, these conditions tend to be seen in the non-athletic population who over-consume sports drinks while living a sedentary lifestyle (Raizel et al. 2019). Adverse effects of sports drinks can become more pronounced if mixed with alcohol and for that reason, it is important not to consume both too close together (Raizel et al. 2019). Regarding children, research for sports drinks optimizing athletic performance in youth is sparse (Pound & Blair, 2017). Sweat rates for children tend to differ when compared with adults thus it is rare for children to exercise in a dehydrated state (Pound & Blair, 2017). Although sports drinks may be warranted for youth athletes performing a vigorous activity, it appears their use is unnecessary for the average child partaking in physical activity or daily play-based physical activity (Pound & Blair, 2017). The main adverse effect associated with sports drinks appears to be their effect on dental health. Tooth erosion is the dissolution of tooth mineral caused by external sources as opposed to tooth decay caused by internal sources such as plaque and bacteria (Kaye, 2017). Erosion starts with an initial softening of the enamel surface and eventually leading to permanent loss of tooth volume and thinning of the tooth surface (Arnauteanu et. al. 2015). Erosion will occur if the solution around the enamel has a pH lower than 5.5 (Kaye, 2017). Most sports drinks have a pH normally between 2.5 to 4.5 (Jena et al. 2019). One study assessed 795 participants and found concerning results. Tooth erosion was present in 26% of people who were considered “low consumer” with a daily sports drink intake of less than 250ml and a staggering 77% of people who consumed greater than 750ml per day were affected by tooth erosion (Sovik et al. 2015). This is a grave concern, considering that is not out of the ordinary for athletes to consume higher than 750ml of sports drinks per day, especially during intense training sessions or events (Sovik et al. 2015). In the 2012 London Olympics, 30% of medical visits to athletes were dental consultations and were only second to musculoskeletal problems (Vanhegan et al. 2013). Interestingly other factors aside from sports drinks such as race pace, training frequency, and gastroesophageal reflux contribute to tooth erosion too in endurance runners (Antunes et al. 2017). During intense and long-duration endurance activities athletes can experience changes in saliva flow and pH, also leading to tooth erosion (Antunes et al. 2017). A serious problem for athletes who drink sports drinks is the hyposalivation that occurs during exercise (Kaye, 2017). As mentioned earlier, athletes in prolonged events or hot conditions lose a lot of fluid through perspiration. Increased perspiration rate decreases saliva and causes dryness in the mouth, also known as xerostomia (Kaye, 2017). Saliva aids in neutralising the acid contained in foods and drinks and reduces harmful effects by quickly clearing food and drink from the mouth (Kaye, 2017). Saliva can also provide calcium and phosphorus to help protect tooth enamel (Kaye, 2017). However, with less saliva in the mouth, the athlete loses its tooth protection mechanism, and they are going to tend to drink more of a sports drink to counteract xerostomia leading to a potent remedy for tooth erosion. Sports drink companies are looking to counteract this, and sometimes calcium can be added as an ingredient, aiming to increase the pH of the drink thus reducing the erosion potential of the drink (Milosevic, 2004). Adding calcium and phosphate to isotonic drinks may keep saliva at a normal pH, inhibiting tooth demineralisation (Antunes et al. 2017). However, current ingredients already in sports drinks cause the opposite effect such as citric acid which is added to sports drinks for flavour. When citric acid is in the mouth it binds to calcium and phosphorus reducing teeth defence and increasing the erosion capabilities of a sports drink (Kaye, 2017). Perhaps, focusing on potentially reduces or lessening the effects of current ingredients in some sports drinks rather than added more ingredients to counteract the harmful effects may be a better solution. Conclusion To conclude, sports drinks can be good for athletes when used correctly and at the right time. They tend to be most suited over longer duration activities (1+ hour) and during hot or humid weather conditions. Evidence shows they can be just as effective as water for replacing lost fluids preventing dehydration. They provide energy by replenishing used glycogen stores increasing the athlete’s time to exhaustion. They also ensure electrolyte balance is not comprised preventing dangerous conditions such as hyponatremia. Isotonic sports drinks are preferred over hypotonic and hypertonic during exercise to optimize performance. Adverse effects lean towards non-athletic individuals over-consuming sports drinks rather than athletes carefully using sports drinks; however, dental health cannot be ignored, and it is important athletes are aware of tooth erosion caused by sports drinks. For this reason, athletes need to be mindful of their dental health and only consume sports drinks when necessary.
