The impact of an 8-week green-exercise programme on systemic health, and on markers associated with cardiovascular disease risk

The current PhD project aimed to carry out an investigation into the effect of green-exercise programmes on markers of health related to cardiovascular risk. These markers derived from three diverse areas; blood-borne markers of CV risk; vascular haemodynamics and arterial stiffness; and mental health. Exercise is a well-regarded treatment and preventive tool for markers of health related to these three areas and green-exercise has previously been seen to acutely improve markers of mental health and blood pressure, with access to green space being seen to correlate with better health and lower rates of morbidity and mortality. However, the specific impact upon health of regular participation in green-exercise had not before been investigated.

A cross-sectional study was first performed to determine whether there was any effect of regular participation in aerobic exercise upon the measures of health and CV risk that were then to be employed in an intervention study. This study determined that regular participation was associated with reduced expression of the elastin-degrading enzyme, MMP-9, increased levels of HDL, and reduced diastolic blood pressures. With regards to mental health; self-esteem and cognitive function were improved in the regularly active participants compared to those who were sedentary.

For the intervention study, previously sedentary participants in community-based green-exercise walking groups and workplace-based green-exercise walking challenges were recruited. Following the intervention, it was observed that approximately half of participants had not adhered to the green-exercise programme, and the cohort was therefore split in to a non-adherent group and an adherent group. The data suggest that regular attendance (an average of two 45-min sessions per week/8-weeks) of low/moderate-intensity green-exercise programmes is associated with significant reductions in MMP-9, and also increases in CD36 and ABCA1; two genes involved in reverse cholesterol transport. Central and peripheral SBP, DBP and MAP were also reduced, as was AIx (an indirect measure of arterial stiffness). Measures of anxiety, depression, self-esteem, stress and mood were also improved. Correlative associations were identified between AIx and MMP-9 expression, suggesting that exercise-associated MMP-9 down-regulation may be a mechanism contributing towards exercise-associated reductions in arterial stiffness, and hence CV risk.

In conclusion, these findings suggest that CV risk may be combated using free and easily accessible green-exercise programmes.