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How to Not Bonk During Your Next Triathlon

how not to bonk runner

Co-authored by: Rebecca Arturo and Nicholas Fischer

The Bigger Picture

In order to have a successful race in terms of nutrition, we need to start by looking at the diet as a whole. Then, we can look at the days leading into your event, event morning, and during-event fueling

The diet as a whole should be a balanced diet that provides adequate carbohydrates, protein, and fat to fuel us and recover. It is hard to give specific details as it will depend on the athlete, the event, and their training plan. However…

Days Leading Into Your Event

The meals eaten on the days leading into a race are meals that top off energy stores. A few days prior to the event, start including an extra portion of carbohydrate foods with your meals. 

This could look like adding an extra half to 1 cup of rice, pasta, or another carbohydrate option. While this is technically carb loading, it is not a glutenous pasta party the night before your event, but rather the opportunity to top off glycogen stores in the days leading into your event. 

Portions of protein, higher fiber, and fat options should also be controlled in the meal or two prior to the event day. This way these meals digest well, fill up your energy stores and do not result in the need for excessive bathroom breaks mid-race. 

Think of a pasta meal the night before with a 3-4 oz. meatball, 1-2 cups of pasta, salad, and a slice of garlic bread. Again, these meals are very specific to the athlete. Keep in mind that athletes need more sodium than other people, so feel free to add a couple of shakes of salt to your meals.

Maintain hydration by monitoring urine color. Your urine should be a light yellow to clear color. However, if you are always seeing clear urine then you may be running the risk of overhydration. You do not need to excessively hydrate leading up to the event. Drink a normal amount of water for proper hydration as any other week.

Race Morning

Now to the pre-event meal. It is best to start with the general guidelines and then work to tailor your pre-workout meals to your needs and likes. Let us assume that you have followed the above advice for the days leading up to your event, so you are starting with topped-off glycogen stores and you are appropriately hydrated. This meal itself and timing should be practiced many times before race day with your bigger training days. 

The pre-workout meal is not filling your energy store so much as it is keeping it topped off. For pre-workout meals, we need to focus on carbs while keeping protein, fat, and fiber lower since they slow digestion down. You want the fuel going to your muscles, not your stomach. This meal can be eaten 1-4 hours before the workout or event as you want enough time to digest and not have a lot of food in your stomach. 

The closer to the event the smaller the meals and the smaller the amount of protein, fat, and fiber. As a rule of thumb, you want anywhere from half your weight up to double your weight in grams of carbs from foods that are a mix of simple and complex carbs and that digest well. Simple carbs are from foods like jelly or honey. Complex carbs are from foods like rice, pasta, potato, tortilla, etc. Protein can be limited to about 20-30 grams, fat lower than protein, and fiber lower than fat. If you are having your pre-event meal 3-4 hours out, you may also want to consider having a smaller hit of carbs within 20-30 minutes of the race start.

Again, meal size will be very individualized and depend on the event, how far before the event you are eating, and what you can tolerate. For example, I do not like large meals, so I like 2 cups of rice with 2 scrambled eggs 2 hours before the workout or event. My wife can eat the same meal with more rice and eggs and add fruit closer to the workout and be just fine. Finding your ideal pre-workout meal takes time to dial in and may change depending on schedule and other factors. 

Other examples of pre-workout meals could be a large bagel with peanut butter and jelly with a bowl of oatmeal and fruit, a burrito stuffed with rice and egg with an english muffin and jelly, or a large bowl of cereal with milk, fruit, and toast.

During Event Fueling

Fueling and hydration during an event is very individualized and is something that NEEDS to be practiced with workouts, yet is oftentimes an afterthought. So let us assume that the athlete started the event properly fed and hydrated. We want to focus on 3 aspects: carbs, fluid, and salt.

For shorter and less intense events (1-3 hours) hydration and carbs can start at about the 45-60 minute mark depending on the athlete, effort intensity, the weather, and what they can tolerate.  A general rule of thumb is 30-60 grams of carbs per hour. For longer events, fueling should start as soon as possible. In the sport of triathlon, we know we can’t start fueling until we get out of the water.

This means you should be fueling either in transition or in the first few minutes on your bike. For events 3+ hours you can eat as much as 90 grams of carb per hour depending on what is tolerated. It is a good idea to know what fueling options will be offered at your event and test them to see how you tolerate them.

As far as fluids, a general rule is 4-16 oz. fluids every 10-15 min. The goal is to replace what you sweat, which will depend on a lot of factors like weather, event duration, the athlete, etc. So it will be a great idea to know what the weather could be like for an event and practice in those conditions. 

Salt. You also want about 600-1500 mg of sodium each hour. This can come from sports drinks or food. And to make this easy, you can use plain old table salt if you want to add more to your drink. Pink Himalayan salt is not special and will not give a meaningful increase in minerals. ¼ tsp. of table salt will give you about 600 mg of sodium.

Other Considerations

Train Appropriately & Practice Everything

When we think about not bonking in a race, we automatically think about proper fueling and the nutrition factors discussed above. However, there are also other factors to consider in preparing to avoid the physical and mental bonk.

  • Be prepared in your training. In my mind, the event is more about the process of getting to the start line than it is about crossing the finish line. Don’t neglect proper training and then expect an amazing finish.
  • Practice your nutrition during training. Practice the products you will be using, the timing of your fueling at race effort, accessing your fuel on the ride and run, and even your pre-event meal. It does you no good to know all of the information above if your stomach can’t handle the fuel you are trying to use and you don’t dial in your specific plan.
  • Ride your bike in conditions that are similar to what you will likely see on race day. If you know your race is along the coast and historically has a lot of wind, then you aren’t doing yourself any favors by riding the trainer instead of the road because it’s too windy out when your long ride is scheduled. Safety does always come first, but get outside when possible, even if the conditions aren’t ideal.
  • Train your running and cycling on terrain of similar elevation, at least a few times a month if not readily available in your area. I’m not saying that you should avoid hill training if you have a flat course or vice versa, as both can be great training resources, but you do need to get comfortable or at least familiar with riding flats if you will be doing 56 or 112 miles of flat. Your muscles need to get used to the specific demands of your event and your course.
  • Ride your race bike outside. Get comfortable with it. I see way too many triathletes only ride on the trainer until race day and then feel out of control and inefficient.
  • Get in the open water for practice. The pool is a great training tool, but it is not the same as open-water swimming. 
  • Don’t do anything new on race day. No new shoes. Don’t try new goggles out. Don’t let race day be the first time you are wearing a swim cap and find out they give you headaches. Practice everything down to wearing your race kit and knowing how to have your hair to get out of a cap and into a helmet efficiently. Local brick workouts with a tri club or even smaller races far out from your target race are great options for practicing these things.

Have a Race Plan

  • This should be based on your training. Know your target effort zones. Know how these zones should feel based on both RPE and heart rate.
  • Don’t go out too hard or fast. Control your excitement
  • Don’t be afraid of flexibility with your plan. Should race morning throw any surprises at you, be ready to adjust without letting it get to your head.
Becky Arturo
Becky Arturo
Endurance Coach, Physical Therapist at Weights and Plates Endurance | Website

Becky Arturo is the co-founder of Weights and Plates Endurance Coaching. Becky Arturo received her doctorate degree in physical therapy and started practicing as a sports and orthopedic physical therapist in 2019. She is also a certified strength and conditioning specialist as well as a USA Triathlon certified coach. Learn more about Becky

Nicholas Fischer
Nicholas Fischer
Endurance Coach, Registered Dietitian at Weights and Plates Endurance | Website

Nicholas Fischer has been a registered dietitian since 2012 and offers over a decade of experience working with endurance athletes. Nicholas has spent time coaching and providing nutrition education for the Pittsburgh Marathon, USA Cycling, and multiple other cycling and running teams around the country. Learn more about Nicholas