It likely is rebound hypoglycemia. Bunch of info below on the matter of hypoglycemia. Read the how-to-fix section. Ironically, another way to fix (not listed) is "push through" with a slight reduction in pace, and your body may stabilize blood sugar levels.... I just don't list that in my "how-to-fix" section for my clients because it feels terrible to do so and there might be better ways. Fun fact: hypoglycemia doesn't affect actual performance as much as it FEELS like it should. It feels terrible for sure. But if you have the grit to push through it, performance is surprisingly minimally affected.

Common symptoms of mild/moderate hypoglycemia:
1. Fatigue/exhaustion
2. Inability to complete routine exercises/tasks
3. Intense Hunger
4. Nausea or stomach discomfort/pain
5. Shakiness
6. Lightheadedness
7. Weakness
8. Sweating
9. Irritability
10. Tingling sensation around mouth, feet, or hands.
11. Generally feeling like you’re dying (maybe that’s just me??)

Common causes of hypoglycemia:
1. Rebound hypoglycemia, ie. blood sugar crash. Most commonly recognized in children after they eat candy, run around like crazy and then start wailing. Ironically, the same thing happens in adults, we just (usually) don’t cry about it. The surest way to induce rebound hypoglycemia would be to consume a high glycemic index meal 40-70 minutes prior to exercise, and NOT consume any high glycemic index foods during exercise. Even in cases of more moderate or low glycemic index food consumption in that time window before exercise, rebound hypoglycemia is remarkably common. Another common way to create rebound hypoglycemia is to either consume too little intra-workout carbs during a portion of training, or to delay post-workout carbohydrate consumption by more than 10-15 minutes especially if intra-workout carbohydrate consumption was on the lower end of the spectrum for the work output or duration of exercise.

2. Intense exercise in the absence of carbohydrate or minimal carbohydrate. Work out for long enough or hard enough, without sufficient carbs, and you’ll surely begin to experience mild hypoglycemia.

3. Prolonged period of no food consumption. Don’t eat for 12 hours, and you’re likely to experience some level of hypoglycemia as your body works hard to run in a low carb environment.

How to prevent it:
1. Don’t eat 31-75 minutes prior to exercise.

2. If you must eat in that dreaded window, be sure it’s a balanced meal, low in fat, AND ensure that you have intra-workout carbs during your workout and are actively drinking them IMMEDIATELY from the onset of exercise or even just before you start, and throughout the entire workout.

3. If you need to eat closer than 90 minutes to your training, try to do it 10-20 minutes before training, and make it something very easily digestible (like intra-workout carbs) so that it’s not sitting in your gut doing nothing while you train.

4. Ideally, eat ~2 hours prior to training. The more complex the meal is, with more fat and more fiber, the longer before training is advisable.

5. In cases of workouts lasting 75 minutes or more, you MUST have intra-workout carbohydrates, or you’ll surely risk the onset of at least mild hypoglycemia by the end of your training session.

How to FIX it, if it happens:
1. If you’re in middle of workout, drink 10-50g of carbs depending on how much you have left, and how far behind you are on your “scheduled consumption” assuming the target was to drink steadily until the end of the workout, at which point, you’d be out of intra-workout carbs.

2. If you’re not training, reduce activity level (sit) if possible. Drink 4-12oz water, depending on thirst, and consider moving all or part of the next meal’s healthy carbs to right now. Wait 20 minutes. If it persists intensely, consider adding 20g more healthy carbs, or moderate-moderately high GI carbs like banana, melon, mango, white rice, skim milk, most breads.

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Dr. Alex Harrison | Founder & CEO | Sport Physiology & Performance PhD
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