With a lot of trial and error I have come to the conclusion that bolus manipulation pre and post workout is a major player in avoiding those pesky hypos. I will try to explain how I work things out. All examples are based in comparison to my resting carb / insulin ratio which is 1 unit of Humalog to 12 grams of carbohydrate.
When deciding on bolus for my pre workout I ask myself the following questions…
- How long before the workout will I be eating?
If I am eating 2 hours + before the workout then it is very unlikely that I will reduce my bolus. However, if I eat less than two hours before the workout I will reduce the bolus from 1 / 12 to 1/ 20. The reason for this is that insulin works more efficiently when it hits the 2 hour mark. This means that increased insulin sensitivity from exercise would be combined with the insulin at its most effective point and therefore would likely cause a hypo. Are you with me?
- What is the length of the workout?
Having considered the time of eating you must also look at the length of time you will be working out. If it is a short workout like a 20 minute hiit routine I would only reduce slightly. Maybe 1 / 15. However, if it is 60 minutes + I would reduce it maximum 1 / 22.
- What is the nature of the exercise? (e.g. cardio, resistance, high intensity or low intensity)
If the exercise is resistance training / weight lifting I will NOT reduce the bolus. It will stay the same and it will be met with an increased basal of 20%. Cardio is as mentioned above.
- Time of day?
The time of day is also very important. If it is before 9am I keep my bolus 1 / 12 because of dawn phenomenon. This is where your body is releases hormons that cause brief insuling resistance and therefore naturally raises blood glucose levels with or without food. After 9am I will manipulate bolus / basal as above.
Aside from the “before 9am rule” where nothing changes, the post workout carb insulin ratio has to be reduced. For example, as mentioned earlier my resting carb / insulin ratio is 1 / 12, but in order to avoid a hypo with the bolus for my post workout food I have to do a ratio of 1 / 15. The reduction is not as big as the pre workout because we are not as sensitive to the insulin after the exercise as we are during the exercise. The only time I would reduce it further than 1 / 15 is if I am going to workout again within 2 hours of the previous workout (that happens a lot).
I know it all sounds a bit complex but you will definitely get used to it the more you practice. I do all of the above manipulations without a second thought now as I am so used to it from training around 15 – 20 hours per week. Be it choreography, dance, pole dance, weight training, hiit training, yoga, cycling and walking.