Fasted High-Intensity Interval and Moderate-Intensity Exercise Do Not Lead to Detrimental 24-Hour Blood Glucose Profiles

Sam N. Scott; Matt Cocks; Rob C. Andrews; Parth Narendran; Tejpal S. Purewal; Daniel J. Cuthbertson; Anton J. M. Wagenmakers; Sam O. Shepherd


J Clin Endocrinol Metab. 2019;104(1):111-117. 

In This Article


24-hour Glycemic Control

Glucose data from the CGMS are presented in Table 1, and mean continuous glucose monitor traces over the 24-hour period in each condition are shown in Figure 2. The CGMS data revealed no differences in the time spent in level 1 hypoglycemia (≤3.9 mmol/L) over the 24-hour period (P = 0.446) or nocturnal period (P = 0.944) between the CON, HIT, and MICT conditions. Similarly, there were no differences in the time spent in level 2 hypoglycemia (≤2.9 mmol/L) between the three conditions over the 24-hour period (P = 0.518) or nocturnal period (P = 0.969). There were also no differences in the time spent in the target range or hyperglycemia between the three conditions in the 24-hour or nocturnal periods (P > 0.05).

Figure 2.

Continuous glucose monitor traces. Mean 6 SEM continuous glucose monitor traces over the 24-h period (8:00 AM to 8:00 AM) on the day of no exercise (Control), HIT, and MICT. The thick lines represent the mean of all the participants' glucose traces. Exercise was performed at approximately 8:30 AM. The shaded gray area represents the nocturnal period (12:00 AM to 6:00 AM).

The incidence of level 1 hypoglycemia over the 24-hour period (P = 0.266) and the nocturnal period (P = 0.522) was no different between CON, HIT, and MICT. There were no differences in the incidence of level 2 hypoglycemia over the 24-hour (P = 0.837) or nocturnal (P = 0.703) periods between conditions.

There was no report of different levels of snacking between the conditions during the CGMS period. Three participants arrived at the laboratory with a blood glucose concentration of <7 mmol/L on one trial, so they consumed ~200 mL of Lucozade Sport Orange (20 g carbohydrate). No participants arrived with a blood glucose concentration >14 mmol/L.

Acute Change in Blood Glucose Concentration

Blood glucose concentrations did not drop during HIT (+0.39 ± 0.42 mmol/L) or MICT (−0.39 ± 0.66 mmol/L) undertaken in the fasted state (P = 0.493), with no difference between groups (P = 1.00) (Figure 3).

Figure 3.

Blood glucose concentrations during HIT and MICT. Mean (6 SEM) blood glucose concentrations. (A) Before and after exercise. (B) Individual responses to HIT and MICT sessions where the participants fasted overnight and had omitted their fast-acting insulin.