Talk:Stroke volume
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I'm not sure that slower rate -> larger stroke volume -> decreased strain on heart. I'm not a doctor, but AFAIK, slower rate is a result of a stronger muscle with somewhat larger chambers that beats slower when at rest, and is capable of much higher performance than the untrained heart. Strain is further reduced by a decrease in the viscosity of blood. Anyone, anyone?... Wake 04:54, 14 Dec 2003 (UTC)
- I realize this question is more than two years old, but I thought I'd quickly address a simple point here. A slower heart rate allows more time for diastole (ventricular relaxation), giving the ventricles more time to fill with blood, thereby increasing stroke volume. This allows cardiac output to remain high without straining the heart (eg, by making it beat more rapidly). I'm not aware of any changes that exercise has on blood viscosity, though. Cheers, David Iberri (talk) 00:44, 18 February 2006 (UTC)
[edit] what happens to haemoglobin after several weeks of excersice?
Re:What happens to haemoglobin after several weeks of exercise? --210.54.53.12 01:06, 27 Jun 2005 (UTC)
As far as I know there are three different effects
- The most well known and the one endurance athletes are looking for is an up regulation of EPO hormone inducing a higher production of haemoglobin (which means your blood can carry more oxygen to your muscles). Though that does not mean your hematocrit will be higher because endurance training also involves a higher plasma volume and hematocrit is defined as the percentage "haemoglobin/plasma volume"
- The second effect is as follows: during exercise you maintain a high cardiac output which means a higher blood pressure in vessels and a higher speed of circulation. This breaks some haemoglobin molecules. However this is not significant compared to the increase of red cells number obtained thanks to several weeks of training.
- The third effect is a short time effect which is a higher blood haemoglobin concentration at the end of a given exercise compared to the beginning. This is because of a decrease of plasma volume due to sudation.
