What’s Bonking? Causes, Risks, and Prevention


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Bonking is a dreaded expertise and happens when the physique turns into functionally depleted of glycogen. This exhaustion of gas shuts down the physique’s skill to exert itself. The time period will get thrown round loads, however in the event you’ve ever bonked, you understand how unhealthy it may be and the way onerous it's to get better from. So simply what's a bonk, why is it a nasty factor, and how will you keep away from it?

For extra info on bonking, try Ask a Cycling Coach Ep. 261.

Bonking Key Takeaways:

  • Bonking is attributable to a useful depletion of Glycogen
  • Bonking could cause muscle loss, weaken the immune system, result in disruptions in coaching, and put you in bodily hazard
  • Glycogen depletion could be a helpful coaching method, however ought to be used rigorously and moderately
  • Use coaching rides to fine-tune your dietary methods
  • Develop a fueling plan earlier than you get on the bike, and use reminders to observe this plan throughout your exercise or occasion.

What's Bonking?

Bonking is a standard time period for the useful depletion of glycogen, introduced on by train. In different phrases, it’s the situation wherein your muscle groups run out of gas, with profound results on efficiency and well-being.

Many cyclists use the time period bonking to evenly describe a scarcity of vitality or a late-race second when the legs cramp, and the engine appears to fail. Whereas these are all signs of bonking, and it’s not a scientific time period, it does have a selected which means. Extreme fatigue ensuing from going too onerous throughout a trip is normally a symptom of outpacing your skill. Alternatively, Bonking tends to happen solely on longer rides while you absolutely exhaust your vitality provides. When you expertise it, you always remember it, and also you by no means need it to occur once more.

What Does Bonking Really feel Like?

A real bonk isn't just a flat feeling or drained legs. It’s a complete incapability to proceed, marked by nausea, excessive bodily weak spot, poor coordination, and a profoundly terrible feeling. Primarily, bonking is exercise-induced hypoglycemia or low blood sugar. Usually, bonking is preceded by waves of progressively worsening signs.

At first, chances are you'll really feel hungry or exhibit detrimental self-talk that ultimately results in a rise in your charge of perceived exertion (RPE). As a bonk will get worse, chances are you'll develop a headache, nausea, shaking fingers, lack of focus, or dizziness. If the bonking continues, so does the chance of confusion and the shortcoming to perform bodily.

It’s important to acknowledge what bonking appears like, not solely in your well being and security, as a result of the earlier you notice the issue, the faster you apply the answer.

Bonking Signs

  • Excessive bodily weak spot
  • Nausea
  • Poor Coordination
  • Shaking fingers
  • Dizziness
  • Cognitive impairment

Bonking Causes

Bonking happens when the muscle groups turn out to be functionally depleted of glycogen, the carbohydrate vitality shops by which the physique fuels itself. Even within the worst bonk, the muscle groups usually are not utterly empty of glycogen, with someplace between 10% and 30% of the unique provide remaining. Nonetheless, the scarcity of obtainable vitality renders the muscle groups unable to proceed working successfully. 

Precisely why this happens is the topic of some debate and analysis. A conventional idea, often called the “catastrophe model,” says that bonking and exhaustion happen as muscle perform reaches its physiological restrict and begins to fail. Newer analysis suggests the mind acts as a “central governor” to restrict the muscle groups preemptively, shutting their perform down as vitality provides run low to stop injury. Regardless of the trigger, the impact is profound.

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Why Bonking is Unhealthy

Bonking is especially vicious. It feels horrible and impacts your common well being and wellbeing. Not solely can bonking break a trip, exercise, or race, however it could derail your coaching and future efficiency.

Muscle Loss

Throughout train, the physique is in a catabolic state of stress. A rise in cortisol causes blood glucose ranges to rise, making extra of the physique’s carbohydrate gas out there to allow onerous work. An absence of carbohydrates shifts the metabolism to different gas sources, more and more burning fats and ultimately protein. This can be a state wherein the physique is basically consuming itself, consuming its personal muscle as an vitality provide. Since we want our muscle groups to show pedals, it ought to be apparent why that is lower than very best.

Immune Suppression

The rising science of immuno-metabolism suggests a connection between carbohydrates and the immune system’s skill to battle an infection. It’s well-known that train has a helpful long-term impact on immunity, however overtraining and bonking could cause the alternative. Similar to muscle groups, immune cells include glycogen and use it as a gas supply. Research present that depleting this glycogen provide renders the immune cells much less efficient in doing their job- basically, your immune cells can bonk!

That is one cause why restoration is so essential in coaching, and why pushing the physique to the purpose of failure in bonking will be harmful. Suppressed immune perform can final from 24-72 hours after the trip, relying on how deeply you run your self down.

Coaching Disruption and Bodily Hazard

Coaching is cumulative, and every particular person exercise in a coaching plan is designed with the next exercise in thoughts. Bonking disrupts this rhythm by creating an enormous quantity of unproductive fatigue and stress. In lots of instances, bonking goes hand-in-hand with dehydration, as riders who usually are not consuming sufficient are sometimes not consuming sufficient, both. Glycogen itself is water-dense, and working out of it reduces the quantity of obtainable hydration throughout the muscle groups. Dehydration is harmful and compounds the fatigue and detrimental results bonking leaves behind. 

The psychological facet of bonking could be a highly effective deterrent to coaching, too. As cyclists, we often push ourselves additional than we expect we are able to. The extraordinarily uncomfortable expertise of a bonk is perhaps simply the discouraging affiliation your unconscious must impose additional limits. Worse, it usually results in conditions which might be simply plain harmful. Cognitive perform declines in tandem with muscular skill, creating short-term psychological and bodily impairment. Judgement, stability, and imaginative and prescient can all be negatively affected. 

Depletion and Adaptation

The aim of any coaching is to disrupt homeostasis and power the physique to adapt. Using in a glycogen-depleted state can stimulate extra environment friendly storage and use of glycogen sooner or later. As well as, using with low glycogen and glucose ranges within the bloodstream causes extra fats to be metabolized as gas. Nonetheless, each of those diversifications will be focused via safer and extra productive means than an outright bonk. Lengthy/gradual distance rides, cautious post-ride carbohydrate restriction, and low-intensity rides with out additional sugar can work in direction of this finish with out vital detrimental penalties. 

How Lengthy does it take to Recuperate From Bonking?

Often, the worst nausea and weak spot of a bonk will be resolved comparatively rapidly with ample foods and drinks, however that doesn’t imply you’ve recovered. By definition, bonking is a big and disruptive occasion in your physique, pushing you properly past the stress of very best or productive coaching. Sadly, this implies the results of a bonk can linger lengthy after the acute results have resolved.

Simply how lengthy is determined by how depleted you’ve allowed your physique to turn out to be, but it surely’s usually worsened by the truth that most bonks happen on huge rides. This implies along with the heavy coaching load of the trip itself, your physique can also be burdened with the added restoration of your caloric depletion.

Restoration from a bonk normally takes no less than a couple of days, and typically longer. Throughout this time chances are you'll end up extra run down, drained, and hungry than regular, and it’s essential to provide your physique the remainder and vitamin it wants. Your immune system may be compromised for as much as 3 days afterward, so take your restoration significantly; getting sick on account of bonking might disrupt your coaching for weeks to return.

What to Do If You Bonk

If you end up starting to bonk, do not forget that foods and drinks are the answer. Nausea continuously makes consuming tough when bonking, regardless of the physique’s determined want for gas. To counter this impact, ingest some liquids along with your meals. As soon as your physique will get a style of restorative carbohydrates, the mind normally responds favorably, however it could take a number of minutes after consuming to start feeling higher.

Don’t hesitate to name a pal or member of the family for a trip in the event you bonk. Useful depletion is a severe and counterproductive occasion, and your precedence afterward ought to be a secure restoration. Pedaling miles house in a compromised state can worsen your situation and considerably set again your upcoming coaching; it’s additionally probably harmful.

The way to Keep away from Bonking

One of the simplest ways to keep away from bonking is fairly easy—give your physique sufficient foods and drinks to remain fueled throughout your exercise! This sounds straightforward, but it surely’s usually tougher than you would possibly suppose. Listed below are some useful tricks to maintain your self fueled.

Determine Out Your Consumption Charge

Every of us have our personal distinctive carbohydrate and caloric consumption requirement, and particular person tolerance for what we are able to abdomen throughout a exercise or race. Don’t wait till race day to be taught what works for you. Coaching rides are a good time to experiment with totally different fueling schedules, and to check out stable vs. liquid meals or a mix of the 2. Additionally, maintain hydration in thoughts and take a look at totally different electrolyte drinks and mixes. Candy Spot exercises are perfect for this experimentation; correct vitamin makes these exercises noticeably simpler, and they're simply onerous sufficient to make an honest approximation of a race’s calls for.

Develop a Plan Earlier than Your Journey

Determine earlier than your trip begins how a lot you’ll have to eat and drink, and set benchmarks for your self to observe. This may occasionally imply figuring out to eat a sure variety of gels by a selected level within the trip, otherwise you would possibly even set your self a timer to recollect to eat one thing each half hour. Should you’re using with a pal or teammate, look out for one another and supply reminders to take care of good vitamin collectively. No matter technique you select, plan ahead- when you’re on the bike, it’s too late to reliably make sensible fueling decisions.

Extra on Biking Vitamin and Bonking:

For extra biking coaching information, hearken to Ask a Biking Coach Podcast— the one podcast devoted to creating you a quicker bike owner. New episodes are launched weekly.


  1. Noakes, T., Peltonen, J., Rusko, H. (2001). Proof {that a} central governor regulates train efficiency throughout acute hypoxia and hyperoxia
  2. Murray, B., Rosenbloom, C. ( 2018). Fundamentals of glycogen metabolism for coaches and athletes
  3. Neiman, D., Wentz, L. (2018) The compelling hyperlink between bodily exercise and the physique’s protection system

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