[quote]Diana Bolann wrote:
Well beta blockers (as Pris mentioned) place an artificial upper limit on your HR. This limits performance…
Is this the mechanism of action or a side effect?[/quote]
Beta blockers work by blocking adrenergic receptor sites. These sites are stimulated by the sympathetic nervous system (fight or flight) - i.e. the adrenals Some of the causes are peripheral vasoconstriction and increase heart rate, amoung many more things. - For example your adrenergic system causes bronchial dilation via the beta 2 receptors, and we all know about clenbutoral on this site. - This is a prime reason why such drugs as metoprolol cannot be prescribed to asthmatics, or those with Chronic obstructed pulmonary disorders who are dependant on their salbutemol to keep their airways open. As Metoprolol can block this action!
Basically metoprolol retards your cardiovascular system from responding to adrenilin which in turn promotes both reduce cardiac work load, pre load and afterload. This is very benificial to those with heart disease who cannot ‘overstress’ their heart for fear of causing ischemia/ angina, which could lead no only to further infarction but other changes such as cardiomeggally. Anyway complicated topic with lots of to discuss, but the above is basically the mechanisms of action.