The effect of physical exercise and resting heart rate on cardiovascular risk

The number of people conducting exercise in a natural environment, such as walking parts of an ancient pilgrimage, is increasing, justifying scientific research to its health effects. Walking part of the pilgrimage route to Santiago de Compostela in Spain, consisting of 280 km in 12 days, resulted in a sustained weight loss of around 2 kg, but no other beneficial metabolic of vascular effects persisting for at least 2 months after the pilgrimage. However, during the pilgrimage, there was a large, steady decrease in LDL-cholesterol (LDL-c), reaching a maximal decrease on day 10 of 1.1±0.7 mmol/l (-29%) compared to study baseline. Furthermore, male and female participants walking this pilgrimage with higher speed showed a larger increase in HDL-cholesterol (HDL-c), but a smaller decrease in LDL-c and total cholesterol than the participants walking with lower speed, and a higher walking speed was independently related to a higher increase in HDL-c and a lesser decrease in LDL-c. The underlying mechanisms of these changes in serum lipids were not investigated, but consumption of cholesterol for cellular metabolism and repair due to muscle damage seems the most likely explanation. Patients with the metabolic syndrome, participating in a nurse-led lifestyle modification program aiming at increasing physical activity and changing dietary habits, reached a average body weight loss of 2,5% (-2.3 kg. 95%CI -3.8--0.8) after 1 year. Both the amount of baseline physical activity and the change in physical activity during the study, were independently related to beneficial changes in parameters of body weight and insulin resistance. The effects of changes in physical activity on measures of body weight and insulin resistance are small, but increasing physical activity remains a cornerstone in the first step treatment of the metabolic syndrome. In the present thesis we present arguments for obesity and insulin resistance as both causes and consequences of sympathetic nerve activation. We show that typically ultrasonographically measured visceral adipose tissue thickness is independently related to increased resting heart rate in men and, to a smaller extent, in women, even after adjustment for body mass index. Furthermore we show that there is an independent relation between resting heart rate and incident type 2 diabetes mellitus (DM) during follow-up in patients with clinically manifest vascular disease. Resting heart rate has been accepted as a risk factor for premature mortality in patients with heart disease, and heart rate reduction is important in the treatment of these patients. In the present thesis we show that an increase in resting heart rate of 10 beats/minute is independently related to an increase in all-cause mortality of 14% (95%CI 7-21%), in vascular mortality of 15% (95%CI 6-25%) and in incident type 2 diabetes of 10% (95%CI 0-21%), in patients with clinically manifest vascular diseases, irrespective of the location. Therefore, we suggest that measurement and evaluation of resting heart rate should become routine practice in the management of patients with clinically manifest vascular diseases and the effect of heart rate reduction therapy in these patients should be investigated.