top of page


How does the physiological response to intermittent high-intensity exercise differ from constant endurance exercise?

It is known that in type 1 diabetics, blood sugar is less severe during intermittent high-intensity exercise (IHT) than during moderate, constant exercise. This is despite the fact that the overall performance of the IHT is much higher.

Any type of training basically increases the risk of developing hypoglycemia, a low blood sugar level. This was already confirmed by MJ MacDonald in a study in 1987. The study was able to show that there is an increased risk of hypoglycaemia up to 31 hours after physical activity. For many diabetics, being informed about possible hypoglycaemia often leads to fear and reluctance to exercise. However, diabetics can safely exercise by consuming carbohydrates and adjusting their insulin intake. This requires knowledge about the physical reaction.

It has been well researched and confirmed that moderate, constant training reduces blood sugar. On the other hand, continuous, high-intensity training (15min at over 80% VO2max) stimulates a continuous increase in blood sugar during and also in the first recovery phase after sport. A combination of moderate exercise and IHT is far less well researched. This combination is very similar to most team sports and also simulates the spontaneous play behavior of a child, for example.

IHT needs more glucose in late recovery

In an experiment by KJ Guelfi in 2006, exactly this combination was examined. The blood sugar levels were kept stable at 5.5mmol/L by a “euglycaemic clamp”. It was found that during the early recovery period, the glucose infusion rate in IHT and moderate exercise alone remained higher than the norm, but after 5 minutes of recovery, that of the moderately exercised group remained significantly higher than that of the IHT group. Thus, the moderately active group required even more glucose during early recovery than the IHT group. Later in recovery, the IHT group needed slightly more glucose than the moderately active, but the two groups were almost equal.

The endogenous glucose production of the liver was also examined. It became clear that IHT is associated with an earlier and greater increase in glucose production. After exercise, glucose production fell rapidly in both groups, but remained slightly above normal levels during the first hour of recovery. The moderately active reached the normal range after about 90 minutes, while the IHT group was still slightly above the normal range even after 2 hours.

Glucose consumption looked similar. However, in the IHT group, this value increased again after an hour of rest and remained significantly higher than the value of the moderately trained group.

Influence on hormones behaves similarly in moderate as IHT

What was striking in the experiment was that neither the moderate nor the IHT increased the hormone adrenaline (opponent of insulin). However, there was an increase in norepinephrine in both groups. Glucagon, also insulin's No. 1 antagonist, did not increase during training. After an hour of rest, however, the glucagon level in the IHT group was significantly lower than that of the moderately trained group.

In summary, high-intensity exercise as part of moderate exercise results in a faster and greater increase in endogenous glucose production during exercise than moderate exercise alone. During early recovery, glucose utilization decreases rapidly after IHT, while remaining slightly elevated after moderate exercise. This is despite the fact that the overall burden at IHT is considerably greater. Glucose requirements are therefore much lower immediately after IHT than after moderate exercise.


  • Guelfi KJ, Ratnam N, Smythe GA, Jones TW, Fournier PA. Effect of intermittent high-intensity compared with continuous moderate exercise on glucose production and utilization in individuals with type 1 diabetes. Am J Physiol Endocrinol Metab. 2007 Mar;292(3):E865-70. doi: 10.1152/ajpendo.00533.2006. PMID: 17339500.

  • MacDonald MJ. Post-exercise late-onset hypoglycemia in insulin-dependent diabetic patients. Diabetes Care. 1987 Sep-Oct;10(5):584-8. doi: 10.2337/diacare.10.5.584. PMID: 3677976.

  • Tuominen JA, Karonen SL, Melamies L, Bolli G, Koivisto VA. Exercise-induced hypoglycaemia in IDDM patients treated with a short-acting insulin analogue. diabetology. 1995 Jan;38(1):106-11. doi: 10.1007/BF02369359. PMID: 7744214.

bottom of page