Introduction:  Research suggests that the combination of increased body temperature and dehydration leads to decreased cardiac functionality during exercise.  The main factor leading to this is a decline in cardiac stroke volume (SV), that is the volume of blood pumped through the left ventricle of the heart during one beat.  Exercises physiology 101 tells us stroke volume is the difference between the end diastolic volume (EDV) (period when the ventricle relaxes and fills) and the end systolic volume (ESV) (period when the ventricle contracts and pushes blood throughout the entire body).  Therefore, the researchers wished to elucidate the effect of dehydration on left ventricular volume and mechanics at rest and during exercise (bouts of cycling in the heat)

Hypothesis:  dehydration would reduce left ventricular mechanics at rest and during exercise.

Results:  Dehydration caused a reduction in EDV, ESV, and SV during exercise.

Conclusion:  The decline in SV is clearly due to a decrease in left ventricular filling of approximately 20ml.  The factor attributed to this is a lower venous return which adds to the EDV in the stroke volume equation (SV = EDV - ESV) as well as a reduced time for the ventricle to fill with blood.

My input:  The take home message is simple here, runners and cyclists, drink your water!

Stohr et al. J Appl Physiol June 23, 2011

1. tharidra reblogged this from exercisescience and added:

   Drink your water while exercising! Your heart will thank you!

2. vandiverok3-blog liked this
3. runslikeapenguin liked this
4. plaintshirt liked this
5. exercisescience posted this