|WikiProject Physiology||(Rated C-class, Mid-importance)|
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)
- I don't know where to write this, but in response to the above, we were told by a Hubs (Human Body Systems) Lecturer that the time spent in diastole doesn't really affect the amount flowed into the heart, as this speeds up to compensate when heart rate increases, vica versa. Summary: SV independant of time in diastole --Africantearoa (talk) 09:52, 9 September 2008 (UTC)
- Well as you said endurance trained athletes have higher max stroke volume et lower max heart rate which allows higher max cardiac output at severe exercise. Thus their blood velocity is heigher, which may cause oxygen diffusion impairement in human lungs. Blood transit time through capillaries in the lungs is reduced which does not allow oxygen to diffuse totally from the alveoli to the capillary. This phenomenon is called Exercise Induced Hypoxemia and may result in a slight decrease in arterial oxygen saturation. This desaturation may be dramatically increased if your are exercising at altitude, where inspired oxygen pressure (PiO2) is reduced. The_FD Paris 08 March 2007
- Oh yes, and as for blood viscosity, endurance training is known to increase plasma volume and thus decrease blood viscosity. This improves blood outflow in the smallest muscle blood capillaries and may reduce oxygen diffusion distance. However if training takes place at altitude blood viscosity may be increased since it brings erythrocytes production up.
what happens to haemoglobin after several weeks of excersice?
Re:What happens to haemoglobin after several weeks of exercise? --220.127.116.11 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.
Stroke volume describes half the work of the myocardium and is readily extrapolated to ejection fraction (EF), end systolic volume (ESV) and minimum Volume (minV). Seen as multiple variables seeking the same answer, they all readily elaborate systole. Systole is the sum of many parts, first and foremost being electrical and mechanical components. The inverse half of myocardial work happens in diastole. Diastole readily implies ESV plus EDV or injection fraction (blood pumped into each heart chamber in one cycle), end diastolic volume (EDV)and maximum Volume (maxV). Inexpensive. noninvasive echocardiography readily renders these variables today. One might argue a compendium is required to keep track of the determinants of myocardial work as they are technologically revealed. —Preceding unsigned comment added by 18.104.22.168 (talk) 00:20, 15 October 2007 (UTC)
Right ventricle or no?
The article reads: "Stroke volume (SV) is the volume of blood pumped by the right/left ventricle of the heart in one contraction.
The stroke volume is not all of the blood contained in the left ventricle. The heart does not pump all the blood out of the ventricle.". So does it include the right ventricle output or not? I believe not, but this is unclear. Thanks --Irrevenant [ talk ] 04:39, 12 April 2008 (UTC)