Platelet number and platelet volume in healthy young men during exercise and changes in posture

In ten healthy young men, alterations in platelet number (B-Thro) and mean platelet volume (MPV) during 15 min of moderate exercise on a bicycle ergometer and 30 min of rest in supine position were determined. During exercise B-Thro increased 10.9% and MPV increased 1.5%. During rest in supine position B-Thro decreased 8.7% whereas MPV was unchanged. From concomitant alterations in leucocyte number, erythrocyte number and concentration of albumin it is concluded that part of the alterations in B-Thro is caused by transfer of water between the vascular system and the interstitial compartment and part is the result of a release of platelets from reservoirs during exercise and a sequestration of platelets in reservoirs during rest in supine position. The alteration in MPV during exercise is explained by a larger average volume of platelets being released from reservoirs when compared with the average volume of platelets already circulating.