What makes your legs heavy?
It has a lot to do with glucose, the fuel your muscles use at higher intensities. Here is what you need to know to understand how it works.
When you’re cycling at a medium to high intensity, your muscles use up a lot of glucose. This glucose needs to be rapidly supplied either by drinking and eating or by your own glycogen stores. When you stop for a while, your metabolic rate decreases and you gradually transition into a recovery state. Here, your body focuses on replenishing energy stores, which results in lowering your glucose levels. Instead of your muscles using up the glucose from the bloodstream, your body releases insulin that takes care of the glucose and keeps your blood sugar normal.
When you settle into your café break and start indulging in some carb-rich pastry, this triggers your body to release insulin to deal with the rising blood sugar, jumpstarting your recovery. This is not a bad thing but you have to keep in mind that it takes your body a while to switch your metabolism back into carb burning.
So, when you get back on your bicycle and begin to pedal hard, you might get in trouble. The insulin that was released is still working to lower blood sugar levels, and now your muscles are also consuming glucose as a result of the exercise. This often leads to a sudden drop in blood sugar known as “rebound hypoglycaemia,” which is exactly what makes your legs feel so heavy even though you just refuelled.
How to prevent the feeling of fatigue after a coffee stop?
Fortunately, there are ways to reduce this effect or even completely avoid it. You can try making your coffee stop shorter, this would not allow your metabolism to fully switch to recovery. The problem is that this kind of defeats the purpose of an enjoyable stop at a café for many cyclists.
Another thing you can do is to enjoy your coffee first while you talk and rest and only have your cake right before getting back on the bike. This would also prevent your body from going fully into recovery. But it’s also not that practical.
Probably the best thing you can do is to re-warm up after your coffee break. No climbing, racing your friends or doing intervals right after! Give your body time to adjust with a few minutes of very easy spinning. That will help you avoid any dips in blood sugar and it will also warm up your legs and increase blood flow so that you are actually ready to push hard when the re-warm up is done.