Effects of physical training on blood pressure in hypertension.

Although initial studies did not allow conclusions on the effects of physical training on blood pressure in hypertension because the groups studied were too small, and because of a mixture of hypertension types, body weight changes and lack of controls, recent studies are not rendered difficult to interpret by such deficiencies. Such studies seem now to allow the conclusion that physical training lowers blood pressure in borderline hypertension by decreasing heart rate and cardiac output, but not peripheral resistance. It is noteworthy that increases of heart rate and cardiac output, as well as a number of other symptoms of increased activity of the central sympathetic nervous system, are characteristic of a large group of subjects with borderline hypertension, and it seems that these subjects are particularly good responders to physical training. Recent studies suggest that physical activity, as well as electric nerve stimulation and acupuncture, sends specific afferent nerve signals to the central nervous system resulting afterwards in increased pain threshold, and lower activity in the central sympathetic nervous system, resulting in lower heart rate and blood pressure. These effects seem to be mediated via endorphin release in the central nervous system because they can be mimicked by local administration of these substances and inhibited by naloxone. It seems an interesting possibility that physical training lowers blood pressure and other expressions of increased sympathetic nervous system activity via such a mechanism. Further studies along this line may be rewarding from different aspects.