Sport’s Drinks - Do they work?
Sports drinks are enriched with nutrients and substances to benefit the health and sports performance of the athlete; however the extent to which sports drinks may benefit performance relies on the many factors that shall be discussed in detail below.
To briefly summarise; sports drinks should be strongly considered by endurance athletes to optimise performance through the replenishment of glycogen stores and reduction of dehydration risk, whilst use in strength sports appears unwarranted for the majority of athletes and water could be considered an adequate drink accompanied by proper peri-workout nutrition.
The key constituent ingredients that all sport’s drinks integrally contain are fluids, carbohydrates and electrolytes. All of these key-components can benefit sports performance in some ways when timed appropriately in the certain situations (particularly endurance events lasting longer than 1 hour); however the extent to which these components will enhance performance ultimately depend on the nutrient status of the individual and the duration and intensity of event.
Each of the key component’s will be discussed below:
Hydration
The fluid component of the sports drink exists to prevent or reduce the risk of dehydration in strength or endurance events.
Sufficient hydration helps with the maintenance of exercise capacity and reduces rating of perceived exertion (RPE). Above 2% dehydration has been found to largely cause a reduction in blood volume, which makes the blood thicker; causing a decrease in blood flow, sweat rate, heat loss. The body attempts to attenuate this through quickening the heart rate; however this leads to an increased core body temperature and rate of glycogen use; which ultimately reduces performance output as lactic acid is produced as a breakdown product of glycogen, which causes skeletal muscle fatigue by increasing the acidity of muscle pH.
Athletes performing high intensity activity commonly have sweat rates of 1.0 – 2.5 L per hour and should aim to match their fluid intake with their sweat rate. However this figure should be scaled to the duration of the exercise. If athletes fail to take on board water during exercise; then an effective rehydration strategy should be to consume 100- 150% of the sweat loss after exercise to ensure effective post-exercise rehydration for optimal recovery. However, important to note is that when recovery time is extended to more than 12 hours, a positive hydration status is achieved with ad libitum food and fluid consumption amounting to the general guidelines of 2-3L of water per day.
Carbohydrates
Whilst is appears advantageous for both types of athletes: strength and endurance to drink fluids throughout exercise to maintain a positive hydration status; carbohydrate consumption intra-workout appears unwarranted in most cases for strength athletes.
Sports drinks contain carbohydrates to maintain blood glucose (between 4.0 and 5.5 mmol/L) and minimise losses of muscle glycogen by ensuring an adequate supply; however, for the majority, consumption will only benefit athletes carrying out activities that last for longer than one hour as activities lasting less than this duration, i.e. weight-training, will not deplete muscle glycogen to an extent that will reduce performance (except if training intensity is very high or if athlete has low glycogen stores).
Consuming a diet rich in carbohydrates, along with ingesting carbohydrates during and following exercise, can improve performance and speed recovery, even just rinsing the mouth with carbohydrate solutions without swallowing has been shown to improve certain aspects of exercise performance such as time to exertion.
During exercise of over 75% VO2max, (very strenuous i.e. running beyond 19km/hr) energy utilisation increases rapidly from 150mg/min, 60% from glycogen at rest to about 1000 mg/min, 90% from glycogen. Therefore, the body commonly depletes its limited glycogen supply (~500g in muscle; ~80g in the liver-) over exercise lasting >90 mins as utilisation can’t keep up with the demand, even with gluconeogenic metabolism producing glucose from amino acids and glycerol. Therefore sports drinks provide a mixture of glucose and fructose to encourage rapid absorption in the small intestine to replenish glycogen stores. The body can utilise 90g/carbohydrates a minute in a mixed-sugar drink (fructose+ glucose) compared to just 60g/carbhydrates for a pure glucose drink; which has implications on what sports drink to consume depending on the intensity and duration, as events >2.5h may benefit from higher intakes of up to 90 g / h whilst 30–60g per hour appears appropriate between events lasting between 1 to 2 hours. Therefore; it is advised to choose drinks ranging from 4-8% carbohydrates and specific to the duration of the endurance event, as drinks with too high of a percentage of carbohydrates (i.e. coke has 11.25% carbohydrates) will not be absorbed as efficiently and could cause stomach upset.
Electrolytes
Sports drinks usually contain electrolytes; such as sodium, calcium, magnesium and potassium to replace those lost in sweat. Sodium is of importance as it is the major electrolyte lost in sweat. In exercise lasting longer than 90 minutes or circumstances where heavy sweating occurs; 450mg of sodium per hour is recommended to promote an adequate hydration status by two mechanisms; as it helps to maintain and restore plasma volume and osmolality by continuing thirst sensation (thus drinking) and also by increases body fluid retention. Ensure to get sufficient intakes of magnesium, calcium, potassium and sodium in the diet to begin exercise with an adequate electrolyte status, as otherwise muscle contraction (and function) will be impaired.
Other ingredients
For completeness; whilst the integral constituents of a sports drinks have been discussed above; there are plenty more ingredients often added to sports drinks; although they may be less essential and often have less research displaying their efficacy. Particularly commonly added ingredients may include B-vitamins, ginseng, guarana, and vitamin c. Whilst research demonstrates the former and latter’s efficacy in promoting an energy yielding metabolism and for lesser inflammation respectively; this is due to their fundamental physiological roles respectfully of being energy co-factors and anti-oxidants, rather than their ergogenic properties. No performance ergogenic effects of vitamins (including all B-Vitamins and vitamin C) were reported in well-nourished individuals in the International Society of Sports Nutrition (2018)
One particularly beneficial ergogenic ingredient with lots of scientific literature supporting it’s use includes caffeine, however caffeine’s potential will be discussed in another blog post in due course as it has many physiological functions and performance enhancing benefits.
Overall:
Overall, sports drinks may have certain health promoting benefits (such as water and sodium to offset dehydration) and sports performance benefits (providing glucose for respiring muscles); however, all ingredients efficacy, necessity and safety should be considered before selection, especially as sports drinks are now commonly being merged with energy drinks in supermarkets, consumed by in-active individuals or by individuals that partake in exercise that doesn’t warrant the need for sports drinks.