Yeah, loads of things, my bg drop after exercise can vary a lot after the few rides I've done since diagnosis. Also, if I'm on normal levemir levels and do a 30min cardio + weights at the gym can result in massive drops in BG . As I can't always predict when I exercise I can't lower my basal every time.
What I will say is that it seems possible for me to get a reasonable level of control for aerobic exercise, and you can be cautious and take a lot of carbs with you.
I feel liberated to be back out on the bike again, after 18 months being diagnosed T1 I finally feel like I'm getting my life back.
Great advice from
@ElyDave there.
To reiterate some things - getting your basal right will really help. Also obviously exercise as far between meals as you can.
Some find that eating a lower carb diet also helps (generally because you have less insulin on board)
Specifically addressing your issues - your varying BG drops?
Depending on the intensity you are working at, you will be burning up glucose at various rates. Higher intensity means that your muscles will prefer to use glucose over free fatty acids and other sources of fuel.
What can often happen however is that with added energy demand (and higher heart rate) your liver will fuel some of those energy needs - releasing its on-board stores of glycogen/glucose, and in order not to end up with high blood glucose levels, you can have a mismatch between how much fuel your body is burning vs how much you are carbing. What you will do however is effectively build up a glucose 'deficit', which will need replacing in the hours after your ride. (This fuel will basically be needed to re-stock the liver and muscle 'bank')
The drop that you mentioned - 11 to 6? Firstly, the initial reading 11 was possibly skewed by the fact that you had not long finished your ride, and your liver was playing 'catch-up' (that is, the liver doesn't stop producing glucose as soon as you finish exercise, and this can be the cause of quite a significant BG rise after you finish exercising)
Secondly, the drop will just be some of that glucose 'deficit' being filled up - it's just your liver and muscles re-stocking.
Really it sounds as though you're doing a great job - just keep doing what you're doing, and record everything. It's useful to build up data from a training route that you can repeat and vary in intensity just to help learn more and fine-tune your regime.
Sometimes when I'm out riding with some of the more experienced T1 cyclists, if they are only a few miles from home and don't want to take another gel when their bloods drop, they will suddenly sprint off up a hill just to take advantage of the liver glucose release that they know this will cause.
Also, to counter any potential BG fall after a ride they will take on board a recovery drink with bolus reduced by 50-75%.
As to the BG rapid drops when you haven't had time to reduce insulin? - you know that it's the insulin doing that to you.
I would suggest you try to get yourself a pump as soon as you can - you will then have the flexibility of being able to reduce your background insulin at any point when you choose to exercise.
You should consider signing up for a stage of the mHealth tour - if you take part in the health study you will get to use a Dexcom CGM. That way you can track bloods constantly and get to grips with exactly how your bloods behave both day and overnight with exercise.
Failing that, just keep an eye out for the next TeamBG ride to see if you can come along.
Keep up the great work! Join the Sporty Diabetic Type 1's facebook group and you'll find there are plenty of cyclists there who can offer support over specific queries too.
http://www.teambloodglucose.com/TeamBG/Home.html