The last 4 months or so I’ve been occasionally experiencing bouts of lightheadedness and profuse sweating about 1 hour after morning rides. I recently confirmed that is is reactive hypoglycemia - confirmed with readings of 20(!!) and 31(!!) on an old school prick style glucose meter.
The typical pattern goes something like this: Wake up and slam a gu and try to get out for a ride as soon as possible (<30 min after waking). Go for a ~1.5 hr MTB ride at ~85 IF consuming about 60g of carbs in the form of Skratch and gu. Lots of caffeine is involved. I feel great during the ride. Blood sugar readings are usually in the 120-130 range immediately after the ride. However, the hypoglycemia sets in about 1 hour post ride.
I’ve experimented with different post-ride eating strategies - high protein, high carb, immediately after the ride, 45-60 minutes after the ride, etc. I can’t find anything that will reliably prevent this. I don’t want to give up the Skratch during the ride because I feel so much better on that than when I’m just drinking water, but I’m worried my body can’t handle that sugar deluge long term.
Has anybody else experienced this? Or have any advice in general?
Talk to a medical professional. This isn’t something to fool around with, especially if as it sounds this is a recurring issue. This could be a symptom of a serious medical issue.
Look up Metabolic Efficiency - you are lacking this.
Salt - 1000mg after the ride has helped me prevent this kind of thing
Unless its a planned hard day - ride easier
Calm down - don’t slam things, be nice to your body.
Don’t start eating until you are nicely warmed up, slamming a gu before your muscles are pumping is just spiking your blood sugar and releasing insulin.
Yes. This happens to me when I get overtrained or too far overreached. It’s actually super apparent on my CGM, and a big sign that I’m due for some recovery time. It has nothing to do with clinical diabetes or glucose intolerance, just being overstressed / overtrained. Have you noticed any sleep issues or training issues?
Thanks for the concern. It is my doctor who diagnosed this. His recommendations were mainly around managing symptoms (15/15 rule) and not prevention.
I’d love to figure out a way to keep doing these rides as it’s one of the only ways to fit rides into my schedule. I did these rides fasted for years, but I perform much better and seem to get more training benefits out of doing them with all of these simple carbs.
Dude get up and eat some toast or a bowl of oatmeal. No wonder you feel awful and you have the data from a glucose meter to confirm it. You basically ate nothing, ingested something like 450 cal of straight sugar (100 for gu, 90g on the 1.5hr ride), rode pretty darn hard, then feel awful like you’ll pass out. Insane and unsurprising. Don’t abuse your body, you’ll surely regret it later in life!
Replying as a T1 diabetic, but a lot of people the liver dumps a load of sugar into the blood ,in diabetes world it’s know as the dawn phenomenon , but it happens in none diabetics as well, and will cause a increase in insulin in the blood flow
You are then eating a sugary snack, which will increase blood sugar and insulin in the blood flow (again) and then doing something that will make you more insulin sensitive, which will probably cause a low after the exercise has finished
My post is from the eyes on diabetic (but the same rules apply, just I have to manually put the insulin there) but it looks to me like eating something with a bit more fiber before and/or during the ride would help
My morning routine before going out on a ride is a commercial shake (I daren’t name it) it’s 400kcals 40g CH0 & 35g PRO with a glycaemic index of 19 so relatively slow release of. CHO into the bloodstream . Out on the bike within 30 mins like yourself but generally not such an intense ride. I then start eating after about 300/400 kJ’s. Wearing a CGM confirmed that blood sugar rises as you would expect but drops gradually after ride to base levels.
Thanks for the diabetic perspective. My mental model is that my body is dumping insulin into my bloodstream to deal with the straight sugar and then doesn’t stop with the insulin even when the sugar stops.
I have tried GrapeNuts before the ride for more slow-release carbs, and unfortunately I still experienced the post ride hypoglycemia. Do you have any recommendations for something with fiber that you eat during the ride?
I’ve seen some sources say that eating vegetables or protein before eating the carbs (like during the meal, eat your chicken before eating the candied sweet potatoes) will reduce the spike. Not sure what that does to your levels after the ride, but it would seem a less volatile spike would result in less rebound effect.
It’s not that your body continues to dump insulin when the sugar stops. It’s that you have increased sensitivity to the insulin while exercising. So you don’t need as much insulin to deal with the sugar you’ve eaten but your body has already been told to dump a bunch since you slammed the gu right after waking up. Now, once the exercise stops, you still have an excess of insulin on board that will consume whatever sugar it can find and that’s what sends you low.
You could try other forms of buffering. I don’t think Grape Nuts would be much of a buffer. Personally, I buffer with a salad and plenty of veggies before carbs but I doubt you want to be eating a big salad right after waking up. You could try buffering with regular peanut butter. Fat is another good buffer (for me at least) if I don’t want to eat a lot before a ride.
You could also wait until your into your ride before taking in carbs. Your body might be likely to dump less insulin once you’re on your ride.
Take these suggestions for what they are worth. I’m coming from a T1D perspective also and have gone low like this a number of times and have spent a good amount of time tuning my pre, during, and post ride nutrition.
I think you have got the wrong end of the stick, it’s not that the insulin hasn’t stopped, it that with your high carb breakfast and snakes (and maybe the dawn phenomenon ) you have encouraged a large amount of insulin into the system, I don’t know how long insulin lasts in a none diabetic, but in a T1 , fast acting insulin last for about 4 hours, you are then doing exercise, making you more insulin sensitive (because the receptors in your muscles open up) and then you hypo
I live in the UK so have no idea what GrapeNuts is but a quick search and it doesn’t like that great to me, especially if you are having milk and sugar with, and it’s still going to be a lot of carbs, I’d be looking for slice of toast (not white() with egg / peanut butter (protein slows down the digestion), something like a banana on the trails, and maybe a little snack afterwards, again something like peanut butter on toast
Rememmber though I am coming at from a T1 diabetic point of view, mornings are a nightmare for me if I want to race, group ride in the morning, for all of the ^^^^^^^
I’ve had bouts dealing with hypoglycemia in the past. I originally thought it was anxiety (also an issue with some overlap of symptoms). I found that ultimately having simple sugars or artificial sweeteners on an empty stomach could often contribute.
While I’m not diabetic, I have worn a continuous blood glucose monitor on a few occasions as an experiment. I found that the absolute best carbohydrate I had in regards to a long slow rise and slow fall of blood sugar levels was steel cut oatmeal. Old fashioned and instant oatmeal were not even remotely close and I’d almost have a hard time considering them complex carbs.
Now for breakfast I have 2 serving steel cut oatmeal with 1 scoop protein every day. Occasionally add in something for flavor. I batch make 3 days worth at a time.
I’d highly suggest doing the same/similar before rides if you are experiencing those issues. It will help control the blood sugar spike/crash from the simple carbs.
I am generally ok to fast for 60-90 min zone 2 rides, but higher intensity I’ll have a little something, and anything longer than 90-120 mins. Before all my big rides (3-4 + hrs) I’ll add in a banana, salt, and cinnamon sugar. Before a race I’ll eat it 90-120 mins before, with another banana about 15-30 minutes before race time.
During my long rides I have the same simple carbs as most everyone else, but the exercise keeps the blood sugar very stable. If I am still consuming close to the end it can spike and crash upon completion if I don’t eat right away.
this is all just my experience, not medical advice.
Hey, I’m sorry to hear about this. It doesn’t sound pleseant at all .
I too want you to continue with your morning rides without suffering like this!
I’m currently looking into the research on this so I’ll share my findings once I have gathered my thoughts but I wanted to reach out before the weekend.
I think this is very interesting, and I too have had a similar experience. Thansk for sharing, @lee82.
You mentioned this has been happening over the last 4 months. I looked at your Calendar and it looks like you really ramped up training mid- April. Perhaps you are overdoing things? I see that you aren’t following a TrainerRoad Training Plan. When we aren’t following a structured Training Plan, it’s easy to fall into the mindset of “I’m not going that hard so it can’t be too much stress on my body” and so becomes VERY easy to overdo things. It is still essential that you balance stress and rest carefuly, even when you aren’t following a structured Training Plan.
As I’ve been reflecting on your questions and the mechanisms involved in blood sugar regulation, Electrolytes came to mind. Are you a heavy sweater? Do you have a hydration strategy? Have you ever had a sweat test done?
I’m going to continue looking into the research on this, and I’ll share what I find. I’m hopeful we can find a strategy moving forward that will improve things for you .
Thanks everybody for the help! Here are some answers for Sarah:
Unfortunately, I was using another indoor training program (where suffering is a feature) until I signed up for Trainerroad a month ago. Only my outdoor rides got imported through Strava into the Trainerroad calendar. So, that’s not painting a full picture. I was ramping up throughout the year until my A event in the summer, but it was gradual enough - at least by measures such as the intervals.icu fitness graph.
Yes, a reasonably heavy and salty sweater. About 1200 mg/L according to a Gatorade patch test. Skratch (regular, not high carb) seems to treat me well for both hydration and energy during these rides. I drink about 1 L with 3 scoops - more on rides that happen later in the day or if it’s hotter.
Let me know what you find! In the meantime, I’m going to experiment with different pre-ride eating strategies that don’t force me to get up too much earlier before the ride.
It’s the caffeine, abstain before and during your morning workouts. I find it ok to do 45 minutes intense sessions fasted, if you can’t then you are going to bed without having eaten enough carbs. By all means start fuelling with sugar once you are warmed up and your metabolism is primed to deal with the sugar.
If you can’t function without caffeine in the morning that’s a pretty good sign you have a caffeine addiction problem.
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