People with type 1 diabetes have to be cautious when they exercise or do any kind of physical activity to avoid setting their blood glucose levels out of sorts. While exercise is a major factor in managing diabetes, people with type 1 diabetes are at risk for hypoglycemia during and after exercise.
In a recent study, Dr. Jane Yardley, as part of her PhD studies at the University of Ottawa, looked at how the order of resistant and aerobic exercises might affect blood glucose control in people with type 1 diabetes. The findings suggest that type 1 diabetes patients may be able to prevent the risk of hypoglycemia by strength training before doing aerobic exercises.
The study involved 12 physically active men and women (average age 32) with type 1 diabetes. Each participant completed two exercise sessions conducted at least five days apart. In one session, each individual ran on a treadmill for 45 minutes and then lifted weights for 45 minutes. In the other session, the exercise sequence was reversed.
Yardley found that patients who did aerobic exercise first had larger drops in blood glucose evels during their exercise, compared to patients who lifted weights first. Although the order of exercise did not increase the risk of hypoglycemia, the length and severity of hypoglycemia was slightly greater when aerobic exercise was done before weightlifting.
These findings suggest that the order of exercise has a significant effect on controlling blood glucose with exercise.
Yardley explained that, “Strength training increases blood glucose by encouraging the liver to release glucose into the blood stream which stabilizes glucose levels. With aerobic exercise, however, there is an increase in glucose [uptake] from the blood stream and since there isn’t enough glucose being produced there the blood glucose levels drop.”
She suggests that people with type 1 diabetes who tend to have to interrupt their exercise all the time to take in more glucose because they’re dropping low should consider doing resistance/strength training first.
Yardley and her colleagues also recently studied the effects of aerobic exercise and resistance exercise on blood sugar levels in people with type 1 diabetes.
The study examined how aerobic and resistance exercise affected blood glucose levels before and after workouts. Yardley found that blood glucose levels dropped more during aerobic exercise than during resistance exercise. However, after resistance exercises, type 1 diabetes patients had better blood glucose levels than after aerobic exercises.
“When resistance exercise happens first, growth hormone is higher during the entire exercise session which encourages fat to be burned as a fuel rather than glucose,” she said. “Also, at the end of resistance exercises, patients will most likely have a buildup of lactate in their system which can be recycled and turned back into glucose to be used in the form of energy. This can then prevent low blood glucose levels for hours after the physical activity.”
Yardley and colleagues concluded from these findings that resistance exercise causes fewer initial drops in blood sugar during exercise, but is linked with more prolonged decreases in post-exercise blood sugar levels compared to aerobic exercise.
One point Yardley really wanted to stress is that both studies had very small sample sizes with fit individuals who knew how to adjust their insulin and carbohydrate intake levels for the physical activities that they were doing.
“Anyone with type 1 diabetes who is going to undertake an exercise program should always be very careful and check their glucose frequently, as well as check in with their endocrinologist and their diabetes educator,” she explained. “It is important that people with type 1 diabetes look at the patterns of their blood glucose levels before, during, and after exercise because the combination of factors that affect glucose is very complex with a lot of variability.”