A Whistle-Stop Tour of Pre, During & Post Exercise Nutrition
This is one of the most commonly asked questions of nutritionists and dietitians alike, and the answer can vary – a lot! In attempting to answer this question, there is likely to be a whole host of different variables to consider – let me give you a few examples! First take into consideration the energetics of your sport: what type of training session or event are you going to take part in? What intensity are you likely to be operating at? For what duration? Are you training in a fatigued state or going to train again later the same day? Then there’s the practicalities of competition: are there ample opportunities to eat before or during the event? What sort of nutrition is available? Which foods do you trust? What is your budget? Also consider how you might be feeling – perhaps pre-event anxiety always diminishes your appetite? Let me guess, you also have longer-term body composition goals to encompass this period of eating into as well?!
Confused? I don’t blame you! Let’s try to break this down step-by-step...
Hydration And Exercise
Hydration is always a good place to start. It’s a simple aspect of exercise nutrition, but one that many underestimate, despite its potential to make or break your performance. Exercising in a hypo-hydrated state (following an uncompensated loss of water) is associated with several negative outcomes – a list of these can be found in the infographic below (1). As part of the Eatwell Guide (2016), the public health guidelines recommend 8 glasses (or 8 x 200ml) of fluid per day, though for the athletic population this number can be increased to 3.5 Litres daily or 500ml every two to three hours or so (2). [IP1] It is also important to note that this includes all beverages except alcohol. Although you may have heard that caffeinated drinks (like tea and coffee) exhibit a slight diuretic impact, they still offer a ‘net hydrating’ effect, which means that their capacity to hydrate outweighs their potential to dehydrate (3). Since no two training sessions are the same, perhaps because of the work planned, duration, temperature or otherwise, there is no all-encompassing rule for pre-exercise fluid intake.
As a base recommendation, ingesting 5-7ml/kg bodyweight of fluid four hours prior to activity is likely to negate the implications of hypohydration (4). However, should the athlete fail to urinate, or produce dark/highly concentrated urine, a further 3-5ml/kg bodyweight two hours pre-exercise followed by another bolus (portion/amount of food) after warming up may be necessary. Where possible, additional fluid should be consumed in small amounts but continuously throughout exercise (around 400-800ml per hour), avoiding excessive quantities that are likely to cause gastrointestinal discomfort.
Following exercise, the primary objective is not only to recover from the previous session, but replenish for the next one (5). Through time and experience, some trainees may have the ability to intuitively hydrate according to their training demands, however, another method is to develop a ‘pre-hydration protocol’ (6). Assuming that the majority of weight lost through exercise is fluid, you can monitor your bodyweight before and after training to calculate typical fluid losses – see the infographic below for an example.
Despite the fact that many sports drinks contain electrolytes such as sodium and potassium, it appears that the addition of these components may not be necessary for many sporting endeavours, unless you are in a severely dehydrated state. However, with emerging evidence of neurological-based benefits from electrolyte compositions in solution, such as enhanced force production and attenuation of fatigue, there appears to be a growing rationale behind their usage (7).
Carbohydrates And Exercise
Here’s where it may get a little tricky. Carbohydrates are the fuel of choice for higher intensity exercise modalities, and can be utilised most effectively following carbohydrate ingestion. For certain sporting disciplines, the expedited rates of carbohydrate oxidation require manipulation techniques to maximise fuelling capacity, for instance, carbohydrate loading. This strategy involves a high carbohydrate pre-event consumption (around 8-12g/kg); however, as many authors have pointed out, this quantity may simply not be necessary for shorter duration activities (8).
The ultimate factor dictating the ideal carbohydrate quantity prior to exercise is an athlete’s daily intake of carbohydrates, typically with regards to body composition goals, which leaves a pre-training ‘carbohydrate allowance’. This pre-training bolus promotes carbohydrate availability during exercise, which can then be further supplemented by consuming light, carbohydrate rich (around 25-30g) snacks 60 minutes prior to activity (9).
The body has a large (and trainable) capacity to ingest and assimilate carbohydrates during exercise (10). Under usual conditions, glucose can be absorbed at a rate of 1g/min, though this can be increased to 1.5g/min when paired with another source (e.g. fructose). However, for sessions preceding one hour, such a high quantity is rarely necessary. Where appropriate (usually for endeavours exceeding 90 minutes), carbohydrates can be ingested in fluid form (e.g. a sports drink with 6-8% carbohydrate content) or in a gel form (often with caffeine) (11).
An interesting avenue of research is carbohydrate mouth rinsing – defined as swilling a carbohydrate containing solution in the oral cavity without ingestion. This can provide the positive benefits of carbohydrates (e.g. increases in central drive and motivation) without the negative ramifications of its consumption, such as gastrointestinal distress (12). As such, carbohydrate mouth rinsing can be useful in a host of specific circumstances, such as during fasting periods, where carbohydrate availability is low or when appetite is diminished (e.g. when nervous). Since carbohydrate ingestion is known to attenuate adaptations to exercise, it is also a way of attaining desirable performance benefits without compromising such adaptive processes.
Carbohydrate ingestion is less critical post training, unless there is a need to immediately fuel in the proximity of subsequent activity. In most cases, intakes of 1g/kg in the meal post training will be sufficient for glycogen replenishment and maximising muscle protein synthesis via the concomitant increase in insulin secretion (13). With variations in fibre content across different carbohydrate sources, it is generally advisable to opt for lower fibre sources pre-exercise and leave the high fibre carbohydrate sources until after training. This is done to avoid excess ‘gut weight’ or gastrointestinal discomfort during exercise.
Protein And Exercise
Despite the heavy marketing, calculating and meeting protein targets is relatively simple. Many coaches and athletes opt for around 1.4-2.2g/kg of bodyweight, which is likely to deliver all daily needs (14). Research suggests that around 0.25-0.4g/kg bodyweight is ideal to support the immediate recovery period post-exercise (15). However, around a 20g source of a complete (containing all essential amino acids) protein is likely to suffice, providing that the source is rich in essential amino acids (like leucine). Consuming similar boluses of protein three to four times daily has been found to maximise muscle protein synthesis, with more frequent ingestion found not to provide any further benefit.
An often overlooked area is pre-exercise protein ingestion. To maximise and induce sufficient amino acid availability for muscle protein synthesis, (16) suggest dividing protein intake pre and post exercise. You’ve probably been advised that faster acting sources (e.g. whey concentrate/isolate) are to be ingested immediately post training, and that you should opt for slower-released forms (e.g. casein) before bed. Whilst this a sufficiently effective strategy, it is important to recognise that minimal transient changes in amino acid availability are not to be held in greater precedence than simply hitting daily/weekly goals on a consistent basis – in other words, no need to rush home for that ‘anabolic window’!
Fats And Exercise
Fats are a longer term store of energy, especially when compared to carbohydrates. As such, large lipid boluses are not typically recommended before or during exercise (17). This is well-demonstrated by a number of studies which have trialled intra-workout fat ingestion, such as medium chain triglycerides, which appear to offer little to no observable benefit (18). Coupling this with the gastrointestinal disturbances associated with fat ingestion pre-exercise, it is generally agreed that fats should be kept low before training to avoid interferences with gastric emptying or distress. In addition, low to moderate amounts of fat have not been found to impair protein synthesis. Therefore, it is important that fat intake does not replace the necessary quantities of carbohydrates and protein, especially in the early post-training period. However, as an essential macronutrient, it is important that fats are consumed outside of proximity to training. Since fat recommendations for athletes are not dissimilar from non-athletes, a good range to aim for is 20-30% of daily energy intake (19).
Contingency Planning For Exercise
Ok that’s all great, but what if life has got in the way, the cupboards are empty or you’ve travelled to an event and forgot to bring anything with you! Either way you are left completely unprepared. Enter contingency planning! See below a range of basic ingredients, and see if you can create a pre, during and post nutrition meal. Try and use some of the principles mentioned above, and remember, it may not be perfect or feature on your Instagram ‘foodie’ highlight reel, but it may just be the only option in seemingly dire circumstances!
To end on a few clichés, always remember that “the best plan is one that you can stick to”. What appears most optimal is useless (practically speaking) if it is not repeatable. Make sure to plan wisely, set realistic goals and always remember to “listen to your body”.
I hope you’ve found this article informative, feel free to get in touch if you have any questions 🙂 @danielfindlaynutrition
Daniel Findlay is a recent graduate from MSc Sports and Exercise Nutrition and BSc (Hons) Nutrition. He is also a 4th Degree Black Belt Taekwon-do Instructor, looking to combine his passions of nutrition and exercise metabolism by pursuing a career in research.