Effects of exercise training on adolescent cardiometabolic health and performance

Dring, K.J. ORCID: 0000-0002-9647-3579, 2020. Effects of exercise training on adolescent cardiometabolic health and performance. PhD, Nottingham Trent University.

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Abstract

The studies described in this thesis were undertaken to examine the effect of physical fitness, adiposity and acute bouts of ecologically valid exercise on risk factors for cardiometabolic diseases in adolescents. Specifically, the relationship between physical fitness (measured as performance on the multi-stage fitness test (MSFT), the blood lactate response to submaximal exercise and V̇ O2 peak) and adiposity with traditional (insulin sensitivity and blood pressure) and novel (pro- and anti-inflammatory cytokine concentration) risk factors for cardiometabolic diseases during adolescence was examined. In addition, a series of studies was undertaken to examine the inflammatory, glycaemic and insulinaemic responses to acute bouts of games-based activity (60 min of basketball) and high intensity intermittent exercise in adolescents. The effect of differing exercise durations (30 vs. 60 min) on the glycaemic and insulinaemic responses to intermittent activity was also examined (Chapter VI). Finally, the effect of continuous training versus remaining inactive on performance on physical capacity tests, V̇ O2 peak, adiposity and risk factors for cardiometabolic diseases was examined in adolescents across a 2-year follow-up.

Throughout the present thesis a comprehensive panel of inflammatory cytokines (including IL1β, IL-6, IL-10, TNF-α) and C-reactive protein was measured alongside blood glucose and plasma insulin concentration. For the epidemiological studies presented in Chapters Ⅳ and ⅤII the inflammatory cytokines measured were an indication of low-grade chronic inflammation in the adolescents, whilst the blood glucose and plasma insulin concentrations were used to calculate the homeostatic model assessment of insulin resistance (HOMA-IR). In contrast, in Chapters V and Ⅵ, the measurement of pro-inflammatory (IL-1β, TNF-α and CRP) and antiinflammatory (IL-6 and IL-10) cytokines, blood glucose and plasma insulin concentrations were used to examine the inflammatory, glycaemic and insulinaemic responses to acute bouts of games-based and high intensity intermittent activity.

The first experimental study (Chapter Ⅳ) examined the effect of performance on the MSFT, V̇ O2 peak and adiposity on risk factors for cardiometabolic diseases in adolescents. Following ethical approval, 121 adolescents (10 - 12 years) were recruited from local secondary schools and sports clubs. Risk factors for cardiometabolic disease (inflammatory cytokines, blood glucose and plasma insulin concentrations) were determined from a fasted capillary blood sample. Participants were separated into quartiles based upon distance run during the MSFT, the blood lactate response to submaximal exercise, V̇ O2 peak, and sum of four skinfolds. Data were analysed using two-way between-subjects ANCOVA and multiple linear regression. Participants with the lowest performance on the MSFT had higher blood concentrations of IL6 (3.25 ± 0.25 pg.mL-1 ) and IL-1β (4.78 ± 0.54 pg.mL-1) and lower concentrations of IL-10 (1.80 ± 0.27 pg.mL-1) when compared with all other quartiles (all p < 0.05). Yet, when categorised into V̇ O2 peak quartiles no differences existed for any of the inflammatory mediators (all p > 0.05). Adiposity was the only predictor of plasma insulin concentration (β = 0.515; p < 0.001) and blood pressure (diastolic β = 0.259; p = 0.042; mean arterial pressure β = 0.322; p = 0.011). In conclusion, performance on the MSFT, but not V̇ O2 peak, was associated with a favourable inflammatory profile in adolescents; whilst adiposity was adversely associated plasma insulin, diastolic and mean arterial blood pressure. These findings demonstrate that enhanced performance on the MSFT and maintenance of a healthy body composition attenuate the presence of risk factors for cardiometabolic diseases in adolescents.

The second experimental chapter (Ⅴ) aimed to investigate the inflammatory, glycaemic and insulinaemic responses to an acute bout of ecologically valid games-based activity in adolescents. Thirty-nine school children aged 11 - 13 years were recruited to the present study and completed exercise (E) and rested (R) trial in a counterbalanced, randomised crossover design. Following a standardised breakfast, participants completed 1 h games‐based activity (basketball). Capillary blood samples were taken at baseline, immediately and 1 h post‐exercise and 30, 60 and 120 min following a standardised lunch. A final fasted capillary blood sample was taken the next morning. Data were analysed using repeated measures ANOVA. IL‐6 concentration was higher on day one of the exercise trial (E 3.4 ± 0.4: R 2.7 ± 0.4 pg.mL−1; p = 0.006), as was the anti‐inflammatory IL‐6: TNF‐α ratio (E 5.53 ± 0.93: R 3.75 ± 0.45; p = 0.027). Anti‐inflammatory cytokine IL‐10 increased on day two of the exercise trial (E 2.11 ± 0.23: R 1.66 ± 0.16 pg.mL−1; p = 0.032). Insulin sensitivity was also enhanced on the exercise trial with a reduction in postprandial plasma insulin iAUC (E 2310 ± 834: R 3122 ± 1443 mU.L −1 x120 min; p < 0.001). Such findings suggest that games‐based activity is an ecologically valid mode of exercise to elicit beneficial effects on risk factors for cardiometabolic diseases in adolescents.

The third experimental chapter (Ⅵ) examined the effects of differing durations (30 min vs. 60 min) of high intensity intermittent activity on postprandial glycaemic and insulinaemic responses in adolescents. Thirty-one participants (13.6 ± 0.49 years) were recruited and completed a 30 min exercise trial, 60 min exercise trial and rested control trial in a randomised, counter-balanced order. The Loughborough Intermittent Shuttle Test was the chosen mode of high intensity intermittent exercise. Capillary blood samples were taken at baseline, immediately and 1 h post‐exercise and 30, 60 and 120 min following a standardised lunch. On day two of the study following the consumption of a standardised breakfast further blood samples were taken at 30 min, 60 min and 120 min to observe the postprandial glycaemic and insulinaemic responses. Data were analysed using a three-way repeated measures ANOVA (trial*time*sex). The pattern of change in blood glucose concentration differed across trials (p = 0.001) as postprandial blood glucose concentration was lower 1 h post-exercise during the 30 min (3.8 ± 0.6 mmol.L -1; p = 0.022) and 60 min trials (3.8 ± 0.6 mmol.L -1; p = 0.017) compared to the rested control trial (4.2 ± 0.9 mmol.L -1 ). Furthermore, postprandial plasma insulin concentration was lower 1 h following the standardised lunch during the 60 min LIST trial when compared with the rested control trial (60 min LIST: 199.1 ± 125.9 pmol.L -1: rested trial 259.4 ± 193.7 pmol.L -1; p = 0.015). There was no difference in blood glucose concentration, plasma insulin concentration and HOMA-IR across trials on day two of the study. The present study suggests that 60 min high intensity intermittent running is an ecologically valid mode of exercise that enhances the regulation of blood glucose and insulin sensitivity in adolescents. Furthermore, a shorter bout of high intensity intermittent exercise (30 min) was also as effective in improving the regulation of blood glucose concentration as 60 min of exercise in adolescents. Such findings support the government physical activity guidelines that suggest young people should participate in 60 min of moderate-to-vigorous physical activity per day.

The final experimental study (Chapter Ⅶ) longitudinally examined (during a 2-year followup) the effect of continued training in comparison to remaining recreationally active during childhood and adolescence on traditional and novel risk factors for cardiometabolic diseases and performance on physical capacity tests. In addition, change in performance and V̇ O2 peak and change in risk factors for cardiometabolic diseases were examined to identify whether a relationship existed between training and adolescent health during puberty. From the original cross-sectional sample, 61 adolescents (12 – 14 years) agreed to complete the study. In conjunction with the methods employed in Chapter Ⅳ, low-grade chronic inflammation, blood glucose and plasma insulin concentrations were determined from a fasted capillary blood sample. Participants completed a MSFT and a V̇ O2 peak test, whilst body composition was assessed as the sum of four skinfolds and waist circumference. Data were analysed via a mixed methods ANOVA (training group*time*sex). Overall, the trained group had lower concentrations of pro-inflammatory cytokines IL-6 (trained 3.52 ± 1.54 pg.mL-1: untrained 4.49 ± 1.81 pg.mL-1 ; p = 0.005) and IL-1β (trained 3.52 ± 2.11 pg.mL-1: untrained 5.46 ± 3.95 pg.mL1; p = 0.007) than the untrained group, yet had higher concentrations of anti-inflammatory cytokine IL-10 (trained 3.31 ± 2.81 pg.mL-1: untrained 2.37 ± 1.36 pg.mL-1; p = 0.008). Overall, the trained group had a lower HOMA-IR than the untrained group (trained 1.4 ± 1.6: untrained 2.7 ± 3.5; p = 0.019). Finally, change in distance run on the MSFT was inversely associated with change in plasma insulin concentration (r (46) = -0.28; p = 0.062) and change in blood lactate concentration during submaximal exercise was negatively correlated with change in HOMA-IR (r (21) = -0.42; p = 0.055); whereas, V̇ O2 peak was not related to any of the risk factors for cardiometabolic diseases. The findings of the present study suggest that continued training from childhood into adolescence improves cardiometabolic health, as evidenced by a favourable inflammatory profile and enhanced insulin sensitivity. Furthermore, as the change in performance on distance run on the MSFT and the blood lactate response to submaximal exercise (which are both indicators of training status) was inversely associated with change in risk factors for metabolic health there is further support of a causal relationship between physical fitness and cardiometabolic health in adolescents.

Overall, the findings from the present thesis suggest that regular participation in exercise (of sufficient intensity to enhance performance on the MSFT or to reduce the blood lactate response to submaximal exercise) reduces the presence of both traditional and novel risk factors for cardiometabolic diseases in healthy, normal weight adolescents. Furthermore, intermittent activity (performed as games-based activity and high intensity intermittent running) is an ecologically valid mode of exercise that stimulated an inflammatory, glycaemic and insulinaemic response in adolescents that elicited protective effects for cardiometabolic health, including an anti-inflammatory cascade and enhanced insulin sensitivity. If repeated regularly such exercise has the potential to reduce cardiometabolic risk factors in young people, thus preventing the early development of chronic diseases such as cardiovascular disease and type 2 diabetes. Taken together, the findings of this thesis have important practical implications, emphasising that regular exercise optimises cardiometabolic health during adolescence, which should be considered by Government health policy makers when developing recommendations for lifelong health. In particular, the findings of this thesis suggest that adolescents should participate in intermittent activity on a daily basis, to enhance their cardiometabolic health.

Item Type: Thesis
Creators: Dring, K.J.
Date: June 2020
Divisions: Schools > School of Science and Technology
Record created by: Linda Sullivan
Date Added: 24 Jun 2020 08:21
Last Modified: 24 Jun 2020 08:21
URI: http://irep.ntu.ac.uk/id/eprint/40092

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