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

Abstract

PurposeTo investigate the effects of an oral glucose tolerance test (OGTT) on baroreflex sensitivity (BRS) in a sample of healthy adolescents, and how acute exercise bouts of different intensities alter the effects of the OGTT on BRS.MethodsThirteen male adolescents (14.0 ± 0.5 years) completed three conditions on separate days in a counterbalanced order: (1) high-intensity interval exercise (HIIE); (2) moderate-intensity interval exercise (MIIE); and (3) resting control (CON). At ~ 90 min following the conditions, participants performed an OGTT. Supine heart rate and blood pressure were monitored continuously at baseline, 60 min following the conditions, and 60 min following the OGTT. A cross-spectral method (LFgain) was used to determine BRS gain. Arterial compliance (AC) was assessed as the BRS vascular component. LFgain divided by AC (LFgain/AC) was used as the autonomic component.ResultsAlthough non-significant, LFgain moderately decreased post-OGTT when no exercise was performed (pre-OGTT = 24.4 ± 8.2 ms mmHg− 1; post-OGTT = 19.9 ± 5.6 ms mmHg− 1; ES = 0.64, P > 0.05). This was attributed to the decrease in LFgain/AC (pre-OGTT = 1.19 ± 0.5 ms µm− 1; post-OGTT = 0.92 ± 0.24 ms µm− 1; ES = 0.69, P > 0.05). Compared to CON (Δ = − 4.4 ± 8.7 ms mmHg− 1), there were no differences for the pre–post-OGTT delta changes in LF/gain for HIIE (Δ = − 3.5 ± 8.2 ms mmHg− 1) and MIIE (Δ = 1.3 ± 9.9 ms mmHg− 1) had no effects on BRS following the OGTT (all ES < 0.5). Similarly, compared to CON (Δ = − 0.23 ± 0.40 ms µm− 1) there were no differences for the pre–post-OGTT delta changes in LF/gain for HIIE (Δ = − 0.22 ± 0.49 ms µm− 1) and MIIE (Δ = 0.13 ± 0.36 ms µm− 1).ConclusionA moderate non-significant decrease in BRS was observed in adolescents following a glucose challenge with no apparent effects of exercise.

Effects of High-Intensity Interval Training on the Vascular and Autonomic Components of the Baroreflex at Rest in Adolescents

“…Indeed, LFgain in the present investigation (CON = 23.1 ± 10.7; HIIE = 21.8 ± 6.12 ms•mmHg -1 at PRE) is higher compared to data in 12-years old adolescents (e.g. ~ 8 ms•mmHg -1 ) (18) but comparable to adolescents of similar age (3) and previous work from our group (27)(28)(29). These studies and the present investigation indicate that in contrast to our hypothesis, BRS does not improve with HIIE training in healthy adolescents.…”

“…The BRS protocol consisted of the following: 1) two automatic measurements of brachial blood pressure were conducted using the returnto-flow method with a Finometer to obtain a brachial reconstructed blood pressure assessment (8); this device has been validated to monitor blood pressure in children (32); 2) after calibration, images of the common carotid artery (CCA) were recorded for 15 cardiac cycles; and 3) participants were instructed to pace their breathing frequency at cycles per min for five minutes (38)(39)(40). This breathing frequency was chosen because it increases autonomic modulation in adolescents (40), and we have recently shown using phase and coherence that the feedback nature of BRS is measured using this protocol (28). The procedures were completed in the described order and lasted ~20 min (including the 10-min rest preceding the protocol).…”

“…The BRS analysis procedures for the present study were performed according to previous paediatric work by our group (27)(28)(29) and others (3,18) using validated (31), and reliable (29) methods. ECG and BP were recorded simultaneously at 1000 Hz (PowerLab, ADInstruments) and RR intervals and systolic blood pressure (SBP) data extracted and saved for later analysis.…”

“…shown that the autonomic compared to the vascular determinant of BRS is more responsive to acute HIIE and hyperglycaemia in healthy adolescents (27,28). Therefore, it can be reasoned that resting cardiac BRS may be improved, thus reflecting increases in its autonomic determinant following HIIE training.…”

High‐intensity interval exercise versus moderate‐intensity continuous exercise on postprandial glucose and insulin responses: A systematic review and meta‐analysis

“…Of the HIIE protocols, a majority of included studies used a cycling modality, while others used walking, running, and rowing. 31,35,37,53,54,56,58,59,61 The most widely used HIIE protocols comprised 8-10 sets of 1-min exercise at near maximal intensity, or four sets of 30-s exercise at all-out effort. Other protocols used longer interval durations at high intensities.…”