The impact of endurance exercise intensity on local and systemic hormonal and cytokine responses in the recreationally active young and old

Moss, Andrew David (2015) The impact of endurance exercise intensity on local and systemic hormonal and cytokine responses in the recreationally active young and old. Doctoral thesis (PhD), Manchester Metropolitan University.

Preview

Available under License Creative Commons Attribution Non-commercial No Derivatives. Download (4MB) | Preview

Abstract

Propelled by the significant socio-economic issues presented by obesity and an ageing population, research has identified links between physical activity, metabolism and disease, and quality of life. Our overall aim was to implement an empirically informed, palatable acute endurance exercise intervention that elicits beneficial hormonal responses with the potential for improved health/quality of life across the lifespan. Two groups of similar male participants (Study 1: n = 6; age, 28 ± 5 yrs.; BMI, 25 ± 4 kg/m2 - Study 2: n = 7; age, 26 ± 7 yrs.; BMI, 25 ± 4 kg/m2) performed equal work (varying duration) moderate (80 % GET) (M) and heavy (30 % ) (H) (Study 1), and H and very heavy (60 % ) (VH) (Study 2) acute constant work-load cycle ergometer exercise trials, respectively (Chapter 3). Analysis of bioptic material indicated increased mRNA (GAPDH normalised) in skeletal muscle for IL-6: baseline (B) vs. M (P = 0.006), H (P < 0.001) and VH (P < 0.001), and M vs. VH (P = 0.02); TNFα: B vs. VH (P = 0.04) and SOCS3 B vs. M (P = 0.02) and VH (P = 0.04). Exercise was without effect in subcutaneous adipose tissue (Chapter 4). The systemic concentrations of IL-6 increased and remained elevated for 24 hrs. in response to exercise. The increase was greatest following M (P = 0.001). IGF-I and cortisol concentrations declined by 60 min post-exercise (P = 0.001 and P = 0.04, respectively) (M, H and VH). GH increased to peak at the end of exercise (P < 0.001) (M, H and VH) (Chapter 5). To investigate the effect of age, groups of male participants (Study 3: 20 - 30 yrs., n = 8; 30 - 40 yrs., n = 10; 40 - 50 yrs., n = 8; 50 - 60 yrs., n = 8) performed a similar 30 min bout of heavy (30 % ) domain exercise (Chapter 6). The systemic concentrations of IL-6 displayed a bi-phasic profile in all groups. IL-6 increased during exercise at 10 min and then 60 min post-exercise (P < 0.001). Insulin and leptin declined during exercise in all groups (P < 0.001 and P = 0.002, respectively). Adiponectin was unchanged. GH increased similarly in all groups to peak again at the end of exercise (P < 0.001). IGF-I was unchanged. Concentrations were consistently higher in the 20 – 30 group however (P = 0.001). Cortisol declined similarly post-exercise in all groups (P < 0.001). We suggest that the oxygen uptake dynamics approach used here should be used when investigating physiological phenomenon potentially sensitive to skeletal muscle metabolic threshold events. We conclude that the exercise-induced hormone and cytokine responses studied in recreationally active health males between 20 and 60 yrs. age most likely reflects the requirements of metabolism. Further work should assess the effectiveness of this modified approach against resistance exercise in a training study format.