Glycemic response to acute high-intensity interval versus moderate-intensity continuous exercise during pregnancy

The present study investigated the glycemic response to an acute high--intensity interval training (HIIT) session (10 one-minute intervals >= 90% HRmax interspersed with one--minute of active recovery) versus a moderate--intensity continuous training (MICT) session (30 min at 64%-76% HRmax) during pregnancy. Twenty--four normoglycemic females with a singleton pregnancy (27.8 +/- 4.7 weeks of gestation, 31.5 +/- 4.1 years of age, body mass index: 25.2 +/- 11.3) participated in a randomized crossover design study. A flash glucose monitor and accelerometer were worn continuously for 7 days recording glycemic response, physical activity, and sleep. Nutritional intake and enjoyment of the exercise were self-reported. Average heart rate during exercise was higher for HIIT (82 +/- 4% HRmax) compared with MICT (74 +/- 4% HRmax; p < 0.001) and participants achieved a peak heart rate of 92 +/- 3% during HIIT (range 85%-97% HRmax) compared with 81 +/- 4% during MICT (p < 0.001). The change in glucose values from pre-to-postexercise were not different between conditions (HIIT: -0.62 +/- 1.00 mmol/L; MICT: -0.81 +/- 1.05 mmol/L; p = 0.300) with the exception that fewer individuals experienced postexercise hypoglycemia immediately following HIIT compared with MICT (8% versus 33% respectively; p = 0.041). Other glucose variables was not different between exercise protocols. Physical activity (p = 0.07) and caloric intake did not differ (p = 0.10). The majority of participants preferred HIIT (87.5%) and had greater perceived enjoyment compared to MICT (HIIT: 7.8 +/- 1.5; MICT: 6.6 +/- 2.0; p = 0.015). Sleep duration was 52 +/- 73 min longer after participating in HIIT compared with the night prior (main effect for time p = 0.017); no significant changes for MICT. Overall, an acute session of HIIT appears to be well tolerated and demonstrates no adverse effects on maternal glycemic response.