The favourable effects of community-based, mixed-intensity aerobic interval training on arterial stiffness and structure
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Background: Literature suggests that arterial disorders account for up to 80% of cardiovascular disease (CVD)-related deaths and that approximately 40% of the cardioprotective effects of aerobic exercise (AE) are due to the benefits it confers on vascular haemodynamics. Longitudinal laboratory-based studies have demonstrated that AE and interval training can improve numerous indices of arterial health, thereby combating early vascular ageing and reducing CVD risk. However, no study has investigated the arterial health benefits conferred by concurrent aerobic interval exercise carried out in the ‘real-world’, that is, in pre-existing community settings whereby individuals are required to self-regulate the exercise intensity. Objective: To determine the effects of a community-based, self-paced mixed-intensity cycling intervention on arterial health indices in healthy, sedentary men. Method: An 8 week repeated-measures intervention design was adopted. Fifteen apparently healthy, sedentary, young to middle-aged adult males (31.8±6.1 years) participated and were split into intervention (n=10) and control groups (n=5). The intervention group undertook 45 minutes of self-paced aerobic interval training 3 times a week for 8 weeks. The gymnasium-based indoor cycling intervention was based on principles of AE interspersed with both high-intensity interval training (HIIT) and sprint interval training (SIT) within a single session. Control participants maintained their routine lifestyles for 8 weeks. A range of measures were determined at baseline (PRE), after 4 weeks (MID) and post-intervention (POST). Resting arterial health indices assessed pertained to target organ damage-related tissue biomarkers of early vascular ageing and included bilateral operative arterial stiffness (carotid-femoral pulse wave velocity, cfPWV), wave reflections (augmentation index, AIx@75), central haemodynamics (central pulse pressure, cPP), wall thickness (carotid intima-media thickness, cIMT; femoral intima-media thickness, fIMT) and arterial geometry (carotid end-diastolic diameter, cEDD and carotid wall:lumen ratio, cWLR). The AIx@75 and cPP were measured using a specialised oscillometric device whilst all other indices were assessed by ultrasonography. Results: The average heart rate during the self-regulated sessions was 81±7%HRpeak. Significant improvements in VO2peak, arterial health, BMI, waist circumference, resting heart rate and resting blood pressure were observed in the intervention group only. The VO2peak increased by 15.1±8.3% (p<0.001, pEta2=0.74) from PRE (33.4±5.4ml/kg/min) to POST (38.3±5.8ml/kg/min), right cfPWV decreased by 10.7% (CI 8.07-12.07) from PRE (8.65±0.36m/s) to POST (7.72±0.43m/s) (p<0.001, pEta2=0.97), AIx@75 improved by 23.8% (CI 8.7-38.8, p=0.006, pEta2=0.59), cIMT and fIMT showed 12.2% and 13.1% decreases respectively (p<0.05), cEDD increased by 7.2% (p<0.05) and cWLR decreased by 18.5% (p<0.05). At POST, there were significant between-group differences in VO2peak (p=0.034, pEta2=0.03), cfPWV (p<0.001, pEta2=0.66), cPP (p=0.015, pEta2=0.38), fIMT (p=0.046, pEta2=0.74), cEDD (p=0.022 pEta2=0.034) and cWLR (p=0.048, pEta2=0.48). VO2peak and cfPWV were negatively related at POST (r=-0.54, p<0.05). Conclusions and perspectives: In healthy, previously sedentary, young to middle-aged male adults, self-paced cycling incorporating different modalities of interval training significantly improves cardiorespiratory fitness and tissue biomarkers of early vascular ageing in addition to causing systemic outward arterial remodelling. The adaptations observed are associated with an improved CV risk profile, indicating the high responsiveness of this population to concurrent aerobic interval training. The present results are consistent with those of previous controlled laboratory-based studies and demonstrate the feasibility and effectiveness of a ‘real-world’ community-based exercise approach to enhance arterial health.