“The only time to eat diet food is while you’re waiting for the steak to cook.” ~Julia Child
You’re training for a marathon. You’ve been diligent about increasing miles gradually, stretching like crazy, eating well. It’s three weeks before your event and you are in the middle of the longest run of your life. You’re 15 miles in, with 5 to go and you’re feeling pretty good. Your legs are a little tired, your stomach is growling a bit. Nothing to worry about.
Suddenly, your legs feel like blocks of lead. You can’t seem to take a step, and you even find yourself weaving a little bit. Out of nowhere you begin to sweat more heavily, your hands start shaking, and you feel as if you might vomit. Your running partner asks if you are ok, and you find it difficult to form words.
Congratulations, you have just experienced a “bonk”.
The “Classic” Bonk
The classic bonk is due to low blood sugar: your body has consumed all of its available calories and is no longer able to keep up with the demand for energy. Low blood sugar should be taken seriously, and once you reach this state you are heading for a medical emergency if you don’t get calories into yourself in a hurry. Most of the time, we feel the bonk before it is critical. However, blood sugar below 60 can be life threatening. While elevated blood sugar causes inflammation and damages organs over time, it is hypoglycemia which leads diabetics into coma and death.
If you are feeling queasy and shaky, but your head is clear, you can rescue yourself pretty quickly by eating some simple carbohydrates. An orange or a candy bar will do, or you can chomp down on a gel or some carbohydrate blocks. It typically takes only a few minutes for simple carbohydrates to get from your mouth to your blood stream, so you start to feel better fast. If your head is fuzzy and you are alone, there is still not much you can do besides eat some sugar. If you are with a friend, make sure he or she does not leave you alone until you have recovered enough that you are no longer experiencing confusion or unsteadiness.
Consuming sugar will give you a quick fix to get out of the emergency, but it will not cure the problem. If you reach this state, you are out of reserves. You will need a combination of protein and fat to stabilize your blood sugar or you will be on a roller-coaster of sugar highs and bonks for the rest of the day which is extremely hard on your body and will likely be devastating to your event performance.
The best remedy for this type of bonk is prevention. There are many prescriptions for how many calories per hour to consume for various types of physical activity, and the bottom line is that regardless of your event you MUST continue to put calories in as you are exercising. Whether you use a sports drink, gels, or solid foods, a good rule of thumb is to consume at least 200 calories per hour if you will be exercising for more than 2 hours.
With endurance exercise such as a marathon or long distance cycling event, blood sugar is not the only reason for a bonk. You can run out of minerals as well. Sweating over a long period of time depletes sodium and potassium. Repetitive use of muscles for hours on end can deplete calcium. Running too low on any of these will leave you feeling awful, destroys your performance, and can be life threatening.
The Sodium Bonk
Sodium is needed for normal function of all your cells. I have had several occasions on long distance bike rides were I have abruptly started to feel sleepy. At 2 in the afternoon, after a solid night of sleep, without more exertion than expected for the ride at hand, I’ve wanted to put the bike in a ditch and curl up beside it for a nap. Every time I’ve felt this way, sodium was at fault. Eating a few crystals of salt had me feeling normal again in minutes. How do you know if you are low on sodium? Even if you don’t get the profound sleepiness I’ve experienced, if potato chips no longer taste salty you’re in trouble.
Again, the ideal answer is prevention rather than trying to fix low sodium after it occurs. Most sports drinks contain enough sodium that you are unlikely to deplete it if you are consuming a bottle per hour of activity.
The Potassium Bonk
Potassium is also necessary for cellular function, and it is another electrolyte which is easily depleted in endurance activities and while working out on a hot day. If you’ve ever been driven in from a few hours of lawn work on a hot day by a nasty headache, chances are you’ve experienced potassium depletion. The primary symptom of acute potassium depletion is a headache, and it will feel like an awful migraine. You can avoid this by eating a banana or two during your workout, taking a potassium supplement, or using a sports drink which contains potassium.
The Calcium Bonk
Many endurance athletes and some weekend warriors experience muscle cramping while exercising. This can be quite severe, and can lead you to be doubled over on the side of the road trying desperately to stretch out the affected body part. Cramping is often the result of calcium depletion. Calcium is required for normal muscle contraction and relaxation, and it is yet another nutrient which is lost when you sweat. If you experience cramps, try eating some yogurt before starting your workout. If cramping happens during a workout and you are not in a place to easily grab a yogurt or ice cream, taking a multi-mineral capsule with calcium and magnesium is usually helpful. Magnesium helps in the absorption of calcium, so it is a good idea to take them together.
The Protein Bonk
Sometimes during a long workout, you just get hungry. No cramping, no sleepiness, no headache, no confusion, you just want to eat everything in sight. The cow on the side of the road looks tasty in its fur. Every plant you pass suddenly looks like it will be the best salad you’ve ever had. Typically this type of hunger means you are running out of protein and fat stores. The answer is to EAT. Try to avoid hitting the nearest fast-food establishment and loading up on empty calories. If you are feeling this way, your body desperately needs good quality nutrition including protein and fat. When this happens to me, I often find myself craving a big serving of fish or a platter of chicken tamales. The protein powder in my bike bag typically seems singularly unappealing at this point, and the bars I carry often look as tasty as cardboard. When you experience this bonk, it is time to stop for a real meal.
Stay tuned…in an upcoming post I’ll share my personal nutrition secrets for avoiding the dreaded bonk!