Acute Exercise and Insulin Sensitivity in Boys: A Time-Course Study

Abstract

This study examined the time course of adaptions in insulin sensitivity (IS) in adolescent boys after acute high-intensity interval exercise (HIIE) and moderate-intensity exercise (MIE). Eight boys (15.1±0.4 y) completed three 3-day experimental trials in a randomised order: 1) 8×1 min cycling at 90% peak power with 75 s recovery (HIIE); 2) cycling at 90% of gas exchange threshold for a duration to match work during HIIE (MIE); and 3) rest (CON). Plasma [glucose] and [insulin] were measured before (PRE-Ex), 24 and 48 h post (24 h-POST, 48 h-POST) in a fasted state, and 40 min (POST-Ex) and 24 h (24 h-POST) post in response to an oral glucose tolerance test (OGTT). IS was estimated using the Cederholm (OGTT) and HOMA (fasted) indices. There was no change to HOMA at 24 h or 48 h-POST (all 0.05). IS from the OGTT was higher POST-EX for HIIE compared to CON (17.4%,=0.010, ES=1.06), and a non-significant increase in IS after MIE compared to CON (9.0%, =0.14, ES=0.59). At 24 h-POST, IS was higher following both HIIE and MIE compared to CON (HIIE:=0.019, 13.2%, ES=0.88; MIE: 9.7%, =0.024, ES=0.65). In conclusion, improvements to IS after a single bout of HIIE and MIE persist up to 24 h after exercise when assessed by OGTT.

Effects of exercise intensity on vascular and autonomic components of the baroreflex following glucose ingestion in adolescents

“…3). These results are different to recent investigations, where moderate to large effects were observed for the reduction in iAUC and tAUC for [GLU] following cycling HIIE and continuous moderate exercise in healthy adolescents (Cockcroft et al 2015, 2017b). A direct comparison between the studies is complex due to the different modes of exercise (i.e., interval running vs interval and continuous cycling), and participants’ maturity characteristics.…”

“…Alternatively, because in the 60 min following the exercise, there is an increase in peripheral insulin sensitivity but not hepatic (Malin et al 2016a), the 90-min recovery in the present study may have facilitated endogenous glucose uptake by the muscle, and when the OGTT started the exogenous source was cleared slowly by the liver and muscle. Perhaps a longer follow-up after the exercise conditions (i.e., 24 h), would provide experimental data on the clearance of blood [GLU], due to a slow phase of glycogen repletion (Cockcroft et al 2017b). Although insulin was not measured, it is likely that the exercise bouts increased insulin sensitivity, as recently reported in healthy adolescents (Cockcroft et al 2015).…”

“…While in adults temporally decreasing physical activity levels does not exacerbate the deleterious effects of an OGTT on BRS (Holwerda et al 2015), the possible effect of increasing physical activity via prior exercise on the subsequent BRS responses to an OGTT is currently unknown. In healthy adolescents, a single bout of high- and moderate-intensity exercise has been shown to reduce the increase in blood [GLU] during an OGTT (Cockcroft et al 2015, 2017b), suggesting that acute exercise may alter the BRS responses to an OGTT by lowering blood [GLU]. Additionally, in the hours following high- but not moderate-intensity exercise, improvements in arterial function are observed in healthy adolescents (Bond et al 2015), showing that exercise may preserve the vascular component of BRS.…”

A single exercise session increases insulin sensitivity in normal weight and overweight/obese adolescents

“…The current study extends the results from a subset of participants that we previously reported . There is now general agreement that a single exercise session completed up to 24 hours before a carbohydrate‐containing meal results in reduced glycemic and/or insulin excursion in adolescents . Cockcroft et al reported that this effect was independent of exercise intensity.…”

“…There is now general agreement that a single exercise session completed up to 24 hours before a carbohydrate‐containing meal results in reduced glycemic and/or insulin excursion in adolescents . Cockcroft et al reported that this effect was independent of exercise intensity. In their studies, NW boys, 14 to 15 years old, had similar reduction in glucose AUC and improvement in insulin sensitivity following either moderate‐ or higher‐intensity exercise bouts.…”