Acute Effects of Daily Life Spontaneous and Structured Physical Activity on Glycemia in Children with Type 1 Diabetes

In type 1 diabetes, glycemia management is rendered complex through the confounding influence of spontaneous physical activity (PA), particularly frequent in children. We aim to understand the glycemic effects of self-reported PA and cumulative spontaneous PA in their everyday life, controlling for carbohydrate intake and insulin.

In this 7-d observational study, 45 children/adolescents (21 females, 11.7 ± 3.4 yr) wore a continuous glucose monitoring system and accelerometer, completing diaries about PA, diet, and insulin. Types of PA included (i) self-reported PA and its characteristics (duration, subjective intensity) and conditions (previous sessions, timing and pre-exercise carbohydrate intake, insulin-on-board, glycemia), and (ii) spontaneous cumulative PA (accelerometry) adjusted for sedentary time. Linear mixed models were used with results expressed as the estimated coefficient " e ." In cases of skewed continuous dependent outcomes containing a preponderance of zero % values, random-intercept binary logistic regressions were used with results expressed as odds ratios (OR).

Accumulating moderate-to-vigorous PA during the late afternoon ( e = -0.32, P = 0.039) was associated with decreased concomitant time spent >13.9 mmol·L -1 . Time spent >10.0 mmol·L -1 during self-reported PA was lower when children consumed less high-glycemic-index carbohydrates the previous hour ( e = +0.49, P = 0.034; albeit found only in one model out of two) or were physically active before the session (tendency: e = -11.58, P < 0.07). PA conditions were not significantly associated with hypoglycemia. Risk of spending some time <3.9 mmol·L -1 during sessions was higher in the case of longer PA duration (OR = 1.02, P = 0.008). Risk of nocturnal time <3.0 mmol·L -1 was greater when children performed longer duration structured PA (OR = 1.02, P = 0.054) or accumulated more afternoon vigorous-intensity PA (OR = 1.06, P = 0.04).

Increasing spontaneous active behavior during the late afternoon could help reduce daytime spent >13.9 mmol·L -1 . There is a possibility that hyperglycemia during exercise could be limited by multiplying daily PA sessions or avoiding excessive pre-exercise carbohydrate intake. However, as only sessions characteristics, especially duration, predicted time <3.9 mmol·L -1 during PA and <3.0 mmol·L -1 the following night, simplified guidelines (not considering PA conditions) on hypoglycemic risk could be developed.