How to Avoid Bonking in Your Triathlon Training

If you’re new to triathlon you may have heard the term recently, saw it satirically written on a fellow triathlete’s t-shirt, or even ate a “Bonk Breaker” chew, but do you know what the word actually means?

The noun/verb “bonk” is simple. It is a reference to the physiological state your body reaches when all glycogen stores have been depleted and not enough new glycogen has been restored. In other words, you’re out of gas. You’ve hit the wall.

Train for triathlon long enough and this will happen to you. We all do it at some point or another. Bonking is almost like an undesired rite of passage that every triathlete in training must go through. But, of course, we all want to avoid it. So what are the best ways to evade bonking in your triathlon training?


1. Nutrition Early

Avoiding the bonk takes discipline. Dodging it’s slowly creeping claws means taking action when you don’t necessarily feel like action needs to be taken. For instance, there often isn’t much of a desire to consume either solid or liquid nutrition within the first hour of a long triathlon training ride or run.

In fact, you may reject the idea based simply on the current state of your stomach and effort level (which we’ll get to soon). This is not a good excuse. The first hour is arguably the most important time to be taking in precious nutrients for your body to process early on.

This is because you want to delay your body’s need to dip into glycogen stores for required fuel. If it has another source of carbohydrate to utilize in the beginning, it will go for that rather than accessing your reserves early on.

In fact, the way you consume food in general has a direct effect on how your body is going to access fuel when training. So when I say that you need to nutrition early, I mean it! Your diet affects your training weeks before it even happens.

This is because the cleaner you eat, meaning a high protein diet complemented with good carbs and low to none of processed sugars, the more your body will be able to burn fat for fuel. Triathletes who have mastered this ability greatly reduce their probability of bonking. Burning fat for fuel is what is called metabolic efficiency and you can learn much more about the subject in my article, “Triathlon Nutrition – Metabolic Efficiency.”


2. Don’t Pace by How You Feel

It seems so simple, but we’ve all been guilty of it. Especially in long course triathlon training—when you’re only supposed to be exerting 65-75 percent of your functional threshold pace—it’s easy to get over-ambitious when the pace feels so relaxed.

Oh how shortsighted we can be! If you’ve trained smart, then you should know what your threshold capacity is. Based on this knowledge, you should have a good idea of what kind of pace is realistic for, say, a four hour-long ride. It doesn’t matter how easy that pace feels in the beginning. You haven’t suddenly jumped threshold capacities overnight. If you’re increasing your long ride/run pace by 10% then all that means is you’re unjustly over-confident and you need to tone it down or you’re probably going to bonk.

Greater exertion means a greater toll on your body. Your muscular fibers break down quicker, carbohydrates are depleted faster, and you sweat more resulting in greater electrolyte loss.  This is why we don’t sprint like we’re running a 100-meter dash at the start of a marathon.

In the same vain, you need to take these truths into consideration at the beginning of a long session. The pace your faster triathlete buddy can pedal or run at is probably not at the same exertion level that you would be at if you’re attempting to match up. Therefore, even if the pace feels tolerable now, it won’t two hours later when you’re bonking hard.


3. Nutrition Late

This one is sometimes the hardest to be disciplined with. In an IRONMAN triathlon, after 5-7 hours of riding you’re expected to dismount and run a full marathon. For many, this might be another 5 hours or more. The problem is on the latter half of that 112-mile bike leg we often feel even more averse to food than we did at the start. The same can be said after 18 miles of running.

Just because you may have nutritioned early doesn’t mean your body has all the fuel storage it needs for another six hours—or even one more hour. It probably doesn’t and bonking will remind you of this.

This is why it’s important to continue fueling until the very end of your triathlon training long sessions. You need to find out what kinds of food and drink mixes you’re able to put down late in the game. You also simply need to train your body to be able to handle it.

Remember that it’s best to space your fuel consumption as evenly as possible throughout the duration of your long training sessions. This makes the food and drink coming in easier on your stomach. Consistent nutrition is a key strategy for avoiding the bonk.


Avoiding bonking in triathlon training takes discipline in a number of ways. You need to consume nutrients early in your long sessions, stay conservative even when the pace feels easy, and continue to consume fuel consistently and late in the duration of the training.


What’s the worst bonk you’ve ever experienced? Have you ever been aware of violating the topics discussed and as a result bonked badly at the end of your training?

JARED MILAM is a professional triathlete, TriDot coach, and member of the Tri4Him Pro Team. He has 16 years of competitive running experience and 11 years of competitive triathlon experience with a half Iron PR of 3:59 and a full Iron PR of 8:30. Coaching under the TriDot system since 2011, Jared loves working with aspiring triathletes of all ages and performance levels.

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