Successfully managing your hydration and nutrition during a single or multi stage ultra-endurance event plays a critical role. You need to consider not only the duration, distance, terrain, temperature, altitude but also sweat rate, access to fluid and food and pack weight. Strategies and experiences vary significantly and need to be approached individually, then planned and practiced during training leading up to as well as during an event, and then fueling to recover properly. On race day, gastro-intestinal issues like nausea and/or reduced appetite are common and makes fueling a challenge and often the traditional high sugar sports nutrition products become unpalatable.
First you have to meet the daily caloric demands required to perform prolonged and repeated training sessions by eating more on the days you train longer to make up for the energy deficit which affects your ability to train and your health.
For athletes during endurance training, a macronutrient breakdown of 60% of calories from carbohydrate (5-8g/kg of bodyweight), 15% of calories from protein (1.3-2.1g/kg) and 25% from fat (1.0-1.5g/kg). Keep in mind that requirements will vary according to the duration, pace of training and body weight.
Track your food intake on an app like My Fitness Pal.
Avoid carbs 90 minutes before you start running. Ultra-runners should aim to maximize their capacity to burn fat for fuel to spare muscle glycogen stores for later on in an event.
In the early stages of preparing for an ultra-event, strategies to maximise fat oxidation is to train in a fasted state or with low glycogen stores.
Consume enough protein to aid muscle recovery, 1.6g/kg to 2g/kg per day. Consuming moderate amounts during the day, 20g every 3 hours being ideal. Protein also protects muscle mass when your calorie intake doesn’t meet your energy needs, especially in periods of high mileage.
Water content from food and fluids contribute to your hydration, so mostly let your thirst and the color of your urine guide you. Avoid excessive fluid intake and eliminate losses by weighing before and after. Replace fluid by slowly consuming more than you lost in combination with a savory food for the sodium to help retain the fluid.
In order to minimize calorie deficits before an event, load up on carbohydrates 2 days before, eating less protein and fat than usual will ensure that you have the appetite and capacity to ingest more carbs without stomach issues.
Aim for 150-300 kcal/hour for events up to 50 miles and 200-400 kcal/hour for longer events. The longer the race is the more energy you require, and longer distances at a slower pace makes it easier to ingest foods and you will use fat for energy to spare your carbohydrate stores. Higher temperatures and altitude will deplete carbohydrate stores faster, affecting energy levels, and glycogen depletion can result in cognitive issues. So aim for 30-60g of carbs (120-240 kcal) per hour, with protein (20g every 3 hours or supplement branch chain amino acids (BCAAs)) and fat to make up the rest as more than 60g/hour of carbs can cause stomach issues, and fat provides twice as many calories per gram than carbohydrates and weighs less in your pack.
Aim for 150-250ml of fluid approximately every 20 minutes but adjust hydration and electrolytes to the environmental conditions. Also don’t drink to excess as it dilutes sodium levels, aim for a sodium intake of 500-700mg/L of fluid. Commercial sports drinks have a lower concentration and it’s unlikely to achieve the required sodium levels from eating savory foods alone.
The most likely cause is the reduced blood flow to the gut as it’s diverted to fuel muscles, dehydration and/or an increase in core temperature can also contribute. Too much or a high concentration of carbs can exacerbate symptoms, so avoid products with more than 8% carbohydrate in strength. Most sports drinks are about 6% but it may help to dilute these even further which will also help with intake. But then check the sodium content and supplement with tablets.
Gels or drinks containing a combination of glucose/maltodextrin and fructose (also found in fresh and dried fruit) may also help as they’re absorbed through different pathways in the body, allowing a larger amount of carbohydrate to be consumed.
Upper GI tract issues like nausea (caused by a drop in blood sugar and taking on some carbs may relieve it) vomiting and heartburn, slow down your pace and reduce your nutrition intake, but don’t let it drop below 200 kcals/hour in races over 80km.
And it is possible to train your gut to tolerate larger amounts of carbohydrate.