How to Bonk Proof Your Running



In my first two marathons, I totally bonked. I was on pace, then suddenly I slowed. Soon, I was reduced to a walk and I no longer cared about my time. I hit the wall and it wasn’t pretty.

Heading into my third marathon, I set my mind to bonk-proofing my running in training by employing some very specific workouts. On race day, the bonk never came and I finished strong during the final 10K.

Here’s how I approached my training differently:


To bonk or hit the wall is to reach a point of exhaustion where you experience a sudden or dramatic reduction in your pace. It’s not tiredness. It’s exhaustion of mind, body, and soul.

Exercise scientists have been working for years to find out the exact cause of bonking. Early on, they looked at muscle carbohydrate (glycogen) stores, blood glucose (sugar) and muscle damage, but nothing was definitive.

Then they looked at the brain and nervous system. They found changes in neurotransmitters and within the central nervous system. But again, there were always exceptions to when runners should have bonked but didn’t, and some bonked when it wasn’t expected.


The current theory is that bonking is a complex interaction of all of the peripheral factors, like muscle glycogen, blood glucose levels, muscle damage and fatigue, as well as central factors (some at the conscious level and some subconscious). In a nutshell, the brain operates like a car’s computer system. In a car with stability control, for example, if the computer receives feedback that the car is out of control, the computer will do all it needs to do to keep you safe.

In the body, renowned researcher Tim Noakes calls this the central governor, and it acts similarly to the computer in your car. Noakes suggests that your brain, based on feedback from the body and within the brain itself, perceives that running at your race pace for the race distance is a threat. As a result, it produces the initial feelings of fatigue, similar to how you feel in miles 15 to 20 in a marathon.

If you keep running at that current pace, it makes you feel more and more fatigued and gets ready to cut the power. If you keep going, the brain believes this threat is becoming dire and shuts down power to the muscles.

The result? You bonk.

However, if you can keep your brain (i.e., the central governor) happy so it doesn’t perceive your race pace for the race distance as a significant threat, it will let your body keep racing along. Luckily, the bonk point is trainable, and with exposure to training and some specific bonking runs, your central governor won’t put the brakes on – instead, it will help power you to the finish.


In the first running boom of the 1970s, the rule of thumb was that your bonk point was three times your average daily mileage. So, if you were preparing for the marathon, you better average roughly 9 miles a day in order to push your bonk point past the 26.2 miles of the marathon.

But there’s a strategy to bonk-proof your body without having to run 60-plus miles per week.

The first step: Find your current bonk point. Warning: This isn’t easy or fun.

As you probably suspect, you’re going to have to run until exhaustion and see how long that takes. You don’t have to run fast. Again, bonking isn’t just tiredness. It’s the point where you simply can’t maintain your pace anymore and are slowed significantly (usually 2 to 3 minutes slower than long-run pace, often to the point where you must walk).

Note: Your true bonk point is how long you can run without fueling. Fueling delays the bonk, so you should avoid carbohydrates before or during this bonking run. For many runners, carb-free running leads to bonking in 1.5-2.5 hours.

Once you know your bonk point, extend it by utilizing the strategies here. You should see your bonk point extend by 30 to 60 minutes across your training plan and that will pay big dividends in your long races.


Once you know your bonk point, you want to challenge it every seven to 14 days with a no-carb run lasting 80 to 90 percent of your bonk point. From a two-hour bonk-point example, you’d need to execute no-carb runs of 1 hour, 36 minutes (80 percent of the bonk point) to 1 hour, 48 minutes (90 percent). Aim to get several of these runs in during the final 12 to 16 weeks before your half marathon or marathon.

Note: You won’t fully bonk on these runs – you’ll get tired and signal your body and mind to quickly adapt to this type of running.

Because training should be aimed at improving your bonk point, you should retest your bonk point every four weeks or so to see if it has changed. I suspect you’ll see that your bonk point is farther out, meaning you’ll then need to extend the distance of your 80 to 90 percent, no-carb runs to reflect your increasing bonk point.

There are four other ways to bonk-proof yourself:

  1. Run more. Within your race-specific training phase (the last 10 weeks before your race), add another run to your weekly routine. You don’t have to do this every week but if your body is feeling OK, with no persistent aches or pains, add another easy 30- to 60-minute run to your week.
  2. Extend your average runs. If your runs typically average one hour, bump it up to 75 minutes. These additional 15 minutes help teach your body and mind that long-distance running is nothing to get worried about.
  3. Add a midweek long run. You’ll need to be smart about how this fits in with your other workouts, but a midweek long run of 90-105 minutes is a great way to build resistance to the bonk.
  4. Do more carb-free running. As with the bonk-point test run, work toward doing more of your running with no carbs. Fuel for your key workouts, but on regular runs, begin to run carb-free.

A big part of bonk-proofing yourself means lots of practice running at your goal race pace. Your body becomes more economical at the paces you run, so race pace training is a great way to bonk-proof. Racing too fast, too early is often the demise of runners.

Lastly, make sure you focus on the duration – not the speed – of your long, easy runs. While you will certainly want to do some race-specific long runs (fast finish or pace practice runs), it’s better for you to run longer and slower than the shorter and faster. Read this article about recommended specific speed work workouts for marathoners.


Bonk-proofing works, but you need to be smart about implementing it.

  1. Always carry a rescue gel and fluids with you in case you really need it. Runners susceptible to hypoglycemia may want to skip this type of training.
  2. Run in areas where help is close by (and not a remote road or trail) – just in case you get woozy.
  3. Bonk-point test runs are hard on the body (and mind), so you need to plan extended recovery time after them. I find that an additional two to three recovery days beyond my normal long run recovery is a good rule of thumb.
  4. Keep an eye on your musculoskeletal system and make sure your recovery isn’t only about feeling better mentally, but also being ready physically.
  5. This strategy is NOT for race day. I repeat: This strategy is NOT for race day.
  6. I highly recommend this strategy only for runners who have proven they can complete the distance and now want to finish faster.
  7. The limit on bonk-point runs is 3-3.5 hours. If you can run carb-free for three hours, it is unlikely (given a proper race strategy and race day fueling) that you’ll hit the wall in your next race.

Next: Is it time to rethink your marathon training program?


Written By Greg McMillan
Called “one of the best and smartest distance running coaches in America” by Runner’s World’s Amby Burfoot, Greg McMillan is renowned for his ability to combine the science of endurance performance with the art of real-world coaching. While getting his graduate degree in Exercise Science he created the ever-popular McMillan Running Calculator – called “The Best Running Calculator” by Outside Magazine. A National Champion runner himself, Greg coaches runners from beginners to Boston Qualifiers (15,000+ and counting!) to Olympians.

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