Exercise Nutrition
by Rob Harvey, Oli Shannon & Lorna MacDonald
Introduction
Triathlon is contested over a range of different distances, from super-sprint events which last around 40 minutes, through to ironman races which can take between 8 and 12+ hours to complete. The demands of triathlon will inevitably change based around the distance, but the causes of fatigue remain very similar across the distances. The two biggest causes of fatigue in triathlon seem to be glycogen depletion and dehydration (Jeukendrup et al., 2005). With a correct nutritional plan, you can delay or even prevent total glycogen depletion, and minimise the risk of dehydration. The benefits of correct nutrition do not stop here however, and there are things you can eat or drink to give you a big advantage over your opponents.
Things to bear in mind:
- You don't need to be perfect but the closer you can get to these guidelines the better.
- You'll need to practise in key training sessions to find out what works best for you.
- Much of the advice applies to training too, but remember that the intensity of training sessions can be much lower than racing for a given duration.
The 2 days before Competition
Objectives:
- Maximise muscle and liver glycogen stores
- Maintain hydration status
Strategies:
- CHO Loading: The high carbohydrate diet consumed in the days leading up to competition will help top up your muscle glycogen levels, and high muscle glycogen levels seem to be associated with successful endurance performance. Following a complicated carbohydrate loading protocol in the days prior to competition is not necessary however it is advisable to consume between 8-10g CHO/kg body weight for the 2 days prior to competition.
- Optimal Hydration: Make sure you don't get thirsty. You could work based on 1ml/kcal - so if you burn 3000kcal/day then consume 3 litres of fluid. In addition, every hour of exercise you complete on top of this requires approximately one litre more. Checking the volume and colour of your urine is a good way to estimate your hydration status.
- Salt: If competing in hot conditions, add a little extra salt to your food in the 2 days prior to competition (as long as you have no medical conditions like high blood pressure). This will also encourage you to drink.
Hints and Tips:
- If you plan on having a traditional 'big pasta dinner' then do it 2 days before competition (e.g. Friday evening if you are competiting on the Sunday rather than on the Saturday night) to avoid excess residue in your digestive tract.
2-4 hours Pre-Competition
Objectives:
- Restore Liver Glycogen Stores
- Maintain hydration status
Strategies:
- Final Meal: The meal 2-4 hours before competition (i.e. breakfast) will be useful for restoring your liver glycogen stores. Liver glycogen is used to maintain blood glucose, and liver glycogen stores are partly depleted after an overnight fast as they maintain a steady flow of sugar to the brain. 2-4 hours before competition, try a meal comprising 1-2g CHO/kg body weight (some advise 2-4g CHO/kg BW!). Avoid foods high in fats and protein content and make sure it is easy to digest so keep fibre content low. For instance two English muffins, 1½tablespoons jam, 1 teaspoon marmite and 750 ml sports drink. This provides 2500 kJ, 125 g carbohydrate, 2 g fat, 14 g protein and only 4 g fibre. Foods like liquid meal supplements, sports bars, bananas and juice are also popular pre-race meal choices. In an ideal world the GI of this final meal would be low however low GI foods choices may prove more difficult to digest. Research has not found any reduction in performance from consuming high GI foods as part of the final meal.
- Optimal Hydration: To promote optimum hydration, drink at least 400-600ml of fluid approximately 2 hours before competition in addition to your normal fluid consumption. This will help keep you fully hydrated whilst allowing enough time for excretion of excess water.
Hints and Tips:
- Experiment to find the exact quantity and timing that works best for you. Too short an interval between the final meal and exercise can lead to an unsettled stomach, too long an interval can lead to hypoglycaemia (low blood glucose levels) at the onset of exercise.
- If you have the early morning jitters liquid meal supplements (e.g. PowerBar Protein PlusTM powder) provide an easily digested alternative to foods.
30-60mins pre-competition
Objectives:
If you have had a high carbohydrate diet in the days before competition, and have eaten a good breakfast, you will be in brilliant shape to compete. Those of you looking for the extra advantage may want to consider your nutrition in the 30-60 minute period before you race. There are 3 things you can do here:
- Avoid hypoglycaemia at the onset of exercise and maintain blood glucose levels of 4-5mmol/L
- Maintain hydration status
- Consider taking on board caffeine and nitrate
Strategies:
- A final CHO and fluid top up - Take on a little more carbohydrate and some fluid. Sipping 250-500ml of a drink like Lucozade while you warm up can give you a final boost of energy and fluid, which should be digested and in your system by the time you start exercise.
- Ingest caffeine - Caffeine seems to improve performance significantly, possibly through a metabolic effect, or more likely through the antagonism of adenosine receptors. It can also reduce your perceived effort (exercise feels easier). Take between 3-9 mg/kg caffeine in the hour before exercise. Caffeine tablets can be crushed up and put in your Lucozade, or you could go for a good old cup of coffee.
- Consider nitrate - Nitrate is a naturally occurring compound found in beetroot and spinach. In the body it can be used to produce nitric oxide (not to be confused with nitrous oxide - the booster fuel you boy racers are sticking in your cars...). This seems to reduce the oxygen cost of exercise, making your body work more efficiently and, like caffeine, studies show it can have a big effect on your performance. You can buy little drinks (~100ml) which contain beetroot juice and are very rich in nitrate. Around 50% of the guys racing ITU Elite level are taking nitrate before they race, including both the Brownlee boys! Give it a try!!
Hints and Tips
- The advantage of competing in triathlons is that you can always urinate during the swim if you drink too much in the 60 minutes before the start!
- Make sure you have experimented with caffeine and nitrate in the consumption in your key training sessions
During Competition
Objectives:
- Prevent dehydration and electrolyte loss
- Maintain blood glucose levels
- Spare muscle and liver glycogen
- Limit muscle damage through reducing cortisol release
- Limit suppression of the immune system
Strategies:
- Hydration: Try drinking 200-250ml fluid each 15-20 minutes throughout exercise. This delivers 600-1000ml of fluid per hour to the small intestine. If this is not possible simply drink as you get thirsty and consume as much fluid as you can tolerate without causing bloating or nausea. A good goal is to consumer enough fluid to cover approximately 70% of the fluid lost through sweating.
- CHO: The table below provides good advice for carbohydrate consumption:
|
Recommended CHO intake during exercise in order to optimise performance |
|||
|
Exercise Duration |
CHO needed |
CHO intake |
Comments |
|
15-45mins |
Very small amount of CHO |
|
|
|
45mins-2hrs |
Small amounts of CHO |
Upto 30g/hr |
Can be achieved with most forms of CHO |
|
1.5hrs-3hrs |
Moderate amounts of CHO |
Upto 60g/hr |
An be achieved with CHO that is rapidly oxidised (glucose, maltodextrin) |
|
Over 2.5hrs |
Large amounts of CHO |
Upto 90g/hr |
Can only be achieved by intake of multiple transportable forms of CHO (glucose:fructose, maltodextrin:fructose) |
|
Some of the time periods overlap because individual tolerances/differences need to be taken into account. Author: Asker Jeukendrup, Published: Peak Performance 285, 1-4 2010 |
|||
Use a blend of CHO glucose and fructose based CHO sources in a 2:1 ratio as they are transported across the wall of the intestine separately.
- Electrolytes: Consume 20-80mmol of sodium for each litre of fluid consumed. Consuming a moderate amount of sodium can reduce the risk of hyponatremia, maintain plasma osmolarity, reduce fluid loss by reducing urine output and importantly sustain your drive to drink!
- Protein: Adding 8-15grams of whey protein to your sports drink may have small performance benefits in prolonged activity, due to reduce muscle protein degradation and may help speed recovery. A ratio of 4g CHO to 1g protein is an often cited optimal ratio. This is more relevant to long distance racing or day to day heavy training.
- Caffeine: Can have a performance benefit but like everything else test it in training first to see how you respond. Try an initial does of 3-9mg/kg. Remember that it takes 60-90 minutes for ingest caffeine to reach peak levels in the blood. For more information read the handout on caffeine use.
Hint and Tips:
- In training a good target is to ensure you are consuming at least 30% of the calories you are burning during the session. This can be from a CHO only or CHO+Protein in a 4:1 ratio. So if the session burns 1000kcal then aim to consume at 300kcal during the session (75g CHO or 60g CHO and 15g Protein).
- How to determine the Carbohydrate Percentage of a drink: CHO content [g] / Fluid volume [mL]) x 100: For example, 80g of CHO in 1000mL of water represents an 8% solution. Ensure you aren't mixing energy drinks stronger than an 8% solution, especially when exercising in the heat.
- Choose nutrition during competition that you like the taste of to encourage yourself to drink/eat regularly
- Remember you can't drink/eat during the swim leg of a triathlon and it's easier to drink/eat on the bike than the run so adjust your consumption to account for this.
- In longer races (4hr+), particularly when cycling, you may want to supplement sports drinks and gels with the use of bars and even "real" food. This is because you might actually get hungry and want some space in your rumbling stomach.
- Consider the types of CHO you are consuming as you may need to experiment if you suffer GI problems.
- Exercise up to an intensity of about 75%VO2max has little negative effect on gastric emptying. After this point emptying rates slow considerably as blood is diverted elsewhere. Could this be the factor limiting the intensity that you can maintain during an ironman?
- In sprint and Olympic distance events simply swilling a sports drink in your mouth may have a benefit to performance. See related article.
- The table below shows the concentration of electrolytes in sweat, plasma and intracellular (muscle) water. As mentioned above it's important to try to replace much of the sodium lost in sweat. It's not important to try to replace the potassium, calcium, magnesium and chloride lost in sweat as long as your levels are within range to begin with:
|
Electrolyte |
Plasma: mmol/L (mg/L) |
Sweat: mmol/L (mg/L) |
Intracellular: mmol/L (mg/L) |
|
Sodium |
137-144 (2466-2592) |
20-80 (360-1440) |
10 (180) |
|
Potassium |
3.5-4.9 (63-88.2) |
4-8 (72-144) |
148 (2664) |
|
Calcium |
4.4-5.2 (79.2-93.6) |
3-4 (54-72) |
0-2 (0-36) |
|
Magnesium |
1.5-2.1 (27-37.8) |
1-4 (18-72) |
30-40 (540-720) |
|
Chloride |
100-108 (1800-1944) |
30-70 (540-1260) |
2 (36) |
After Competition
Objectives:
Your muscles are more sensitive to the positive effects of consuming CHO in the 45mins following exercise. If you take advantage of it, you will be rewarded with faster. Since the muscle adaptations that lead to better performance are a result of a consistent exercise and nutrition routines this means you should take advantage of this opportunity after every workout.
- Replenish muscle glycogen stores
- Start the replenishment of fluid and electrolytes
- Initiate tissue repair and set the stage for muscle growth
- Reduce muscle damage and support the immune system
- Shift the metabolic machinery into an anabolic (muscle building) state from a catabolic (muscle-depleting) state.
Strategies:
- Replace expended CHO stores: As soon as possible post race, consume 1.5g CHO/kg of body weight. Best taken in liquid form as this is quickly absorbed and help re-hydration. Mix of glucose sources for quick release and fructose for a slightly slower release. Continue to consume 1-1.2g CHO/Hr for upto 4 hours post activity before continuing with normal eating patterns. The length of this period should be approximately equal to activity duration. So for a 70kg athlete following a race lasting 2.5 hours this would be 105g CHO take within 30mins post race, then 70-84g CHO taken at 1 hr post race and 2hr post race before returning to normal eating patterns.
- Rehydrate: The fluid loss from competition can be estimated from changes in body weight. A loss of 1kg of body weight means a sweat loss of ~1Litre. Try to replace 1.5litres of fluid for each kg of body weight lost in addition to your normal fluid requirements. This may take a number of hours to achieve if weight loss is significant. Sweat rates are very individual as well as being affected by the intensity of exercise and environmental conditions.
- Caffeine and recovery: It is widely know that caffeine can help improve your performance when ingested before exertion. In the past 4 years, research has emerged which suggests caffeine may also be useful during the recovery period. A well designed study from Birmingham University (Pedersen et al., 2008) found that glycogen recovery was 66% higher over a 4-hour period when cyclists consumed caffeine and carbohydrate together versus a carbohydrate only supplement. It seems that caffeine may increase intestinal carbohydrate uptake, and when the recovery period is short (e.g. between training sessions) you may benefit from a cup of coffee (or a bar of chocolate!) with your high carbohydrate snack.
- Provide amino acids - This is for the resynthesis of protein that may have been damaged during exercise. CHO and Protein should be consumed in approximately 4:1 ratio during the 45mins post exercise. So for each gram of CHO consumed, take in 0.25g. If using a supplement then it is best to consume egg or whey protein products which contain all of the essential amino acides and a healthy dose of key branched-chain amino acids (leucine, isoleucine and valine).
- Continue replacing electrolytes: Aim to replace all of the electrolytes lost in sweat. Sodium is the electrolyte most likely to need replenishing.
- Reduce the acidity of body fluids: During exercise body fluids shift increasingly toward an acidic state. If this acidic state is allowed to continue for a prolonged period post exercise the risk of nitrogen loss (from muscle) and calcium loss (from bone) is greatly increased. The net alkaline effect of these substances counteracts the increased acidity. Fruit and vegetables are the only foods that have a net alkaline-enhancing effect so these should be included in your recovery drinks or snacks.
Hints and Tips
- In training a good target is to ensure you are consuming at least 40% of the calories you burned during the session in your post training recovery drink. Ideally this should be from CHO+Protein in a 4:1 ratio. So if the session burns 1000kcal then aim to consume at least 400kcal within 30mins of finishing the session (100g CHO or 80g CHO and 20g Protein).
- Under optimal CHO intake conditions glycogen replenishes at a rate of about 5% per hour so even under the best circumstances it requires at least 20 hours to re-establish glycogen stores after a glycogen depleting exercise bout.
- If the electrolytes lost in sweat are not replaced you will not retain the ingested fluid and a diuretic response is invoke, preventing full recovery even when ingesting large volumes of fluid (Maughan and Leiper 1995)
- Chocolate milk is an excellent choice for this initial post exercise recovery window combined with some fruit or fruit juice and some sodium (pinch of salt). If you don't like chocolate milk then try this as a homemade recovery drink - Blend together: 12-24 Oz fruit juice (apple, grapefruit, orange or pineapple are all relatively high Glycaemic load and electrolyte content), 2-6 Tablespoons of Glucose, 1.5-4 tablespoons of Protein Powder (either egg white or whey), 2-3 pinches of salt, Ice (if frozen berries weren't used)
Sources:
- Oli 'The Professor' Shannon and Lorna 'Nutrition' MacDonald
- AIS Website: http://www.ausport.gov.au/ais/nutrition/factsheets
- The Paleo Diet For Athletes by Loren Cordain and Joe Friel
- Performance Nutrition Handbook - Pacific Health Labs
- ACSM guidelines
- Various Journal Articles
- Various Workshop notes
- Experience working with athletes