Aerobic exercise best for reducing delayed hypoglycemia risk in type 1 diabetes
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Exercise modalities have varying effects in long-term glycemic response for adults with type 1 diabetes, and aerobic exercise may be the best approach to reduce the risk for delayed hypoglycemic events, according to study data.
“The result was quite unexpected as the evidence presented by studies with a shorter follow-up — up to 3 to 6 hours — identified aerobic exercise as the worst approach in terms of glycemic control in the immediate post-exercise,” Giacomo Valli, a PhD student in the neuromuscular physiology laboratory, department of biomedical sciences at the University of Padova, Italy, told Healio. “Here, however, we have shown that in the long term — 24 hours post-exercise — aerobic exercise is the best approach.”
Valli and colleagues conducted a systemic review and meta-analysis of studies evaluating the delayed effect exercise had on glycemic control in adults with type 1 diabetes. The quantitative studies were found through a literature search of studies published on PubMed, SPORTDiscus and Embase from January 2000 to September 2019. Only studies with a follow-up period of up to 6 hours were included. The study population had to be free of any complications, disease, pregnancy or health condition other than type 1 diabetes. All participants were physically active and had good glycemic control.
Researchers analyzed 12 studies with a total of 145 participants. In studies comparing participants who performed endurance exercise and those who did intermittent exercise, the intermittent group had a lower interstitial glucose level after exercise compared with endurance exercisers (mean difference, –0.77 mmol/L; 95% CI, –1.19 to –0.36). Intermittent exercisers also spent a longer time in hypoglycemia. There was no significant difference in time spent in hyperglycemia or the proportion of participants experiencing hypoglycemic events.
One of the studies included in the intermittent exercise group was based on a circuit training protocol and resulted in less time spent in hypoglycemia than other intermittent exercise groups in other studies.
“Preliminary results suggest that circuit training protocols may provide a better outcome than endurance,” the researchers wrote.
One study in the systemic review reported those who took part in endurance exercise in the morning had half the hypoglycemic events compared with those who exercised in the afternoon. Morning exercisers also had better glycemic control the following day.
“In light of this, exercise in the morning is encouraged while more attention will be necessary if endurance is performed in the afternoon,” the researchers wrote. “This conclusion has double utility as if people with diabetes know that a certain behavior will increase the risk of experiencing hypoglycemia, together with the timeframe in which it is more likely to happen, they could adopt strategies to prevent it.”
Another study showed rapid-acting insulin reduction protected exercisers against hypoglycemia for up to 8 hours after endurance exercise, but not later in recovery. Based on literature from other studies adopting different magnitudes of rapid-acting insulin reduction, the researchers wrote that a reduction of 50% of the usual insulin dose may result in better glycemic control.
Valli said new research with a good study design that compares different exercise types is needed to provide stronger findings. The researchers proposed new studies should include a common threshold for defining hypoglycemia, a sedentary control cohort, the time of day of exercise, and data on the number of participants experiencing hypoglycemia and the duration of hypoglycemic episodes.
“The identification of the safest approach to exercise is fundamental to prevent or reduce the occurrence of delayed hypoglycemia during the nighttime, a period during which people are not aware of their glucose level and are therefore exposed to greater risks,” Valli said.
For more information:
Giacomo Valli can be reached at giacomo.valli@phd.unipd.it.
Perspective
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A regular exercise regimen has been understood to assist people with diabetes in maintaining a more steady blood glucose level. Valli and colleagues identify another benefit of exercise — reducing delayed hypoglycemia risk in type 1 diabetes through aerobic exercise. The researchers also touched on the need to reduce rapid-acting insulin in the subjects prior to their exercise bout. During exercise, up to 80% of glucose uptake by the contracting muscles is independent of insulin, via increase in muscle GLUT4 expression. Therefore, reducing the amount of insulin prior to exercise is vital to reduce risk for hypoglycemia during and after exercise.
Glycogen depletion is a major contributor to the cause of post-exercise hypoglycemia. In aerobic exercise, the prolonged steady, repetitive muscle contraction demands a consistent supply of energy, glucose from the circulation and from glycogen. Through endurance training, that is, aerobic exercise, adaptation, the body increases the storage capacity of glucose as glycogen in the muscles and effectively uses and reuses its energy sources through gluconeogenesis and glycolysis. In resistance exercise, the main source of energy comes from the glycogen for quick bursts of energy required to perform powerful, few seconds of repetitive movements followed by rest in between sets. This repeated routine of perform and rest tends to cause release of stress hormones, leading to rising blood glucose. In resistance training, muscle fatigue with strength loss comes on much quicker than in aerobic training.
Exercise or staying physically active has a major role in diabetes management. These metabolic reactions to provide energy for exercise lead to steadier blood glucose level, reduce insulin resistance and better body composition.
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