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C Purcell

Publications and source records attributed to C Purcell.

23 records · Page 2Linked to original sources
PubMedDate not supplied

The human force:velocity relationship; activity in the knee flexor and extensor muscles before and after eccentric practice.

The human voluntary force:velocity relationship frequently fails to demonstrate the expected high eccentric forces. Possible explanations include unique activation strategies which might be affected by neural learning mechanisms. We investigated the effect of practicing eccentric contractions on (1) the force:velocity relationship of the human knee extensor muscles and (2) the extent of agonist and antagonist muscle activity. Eight healthy adults [seven women, group mean age 31 (SEM 5) years +/-] practiced twice a week for 4 weeks using their non-dominant legs. Each session comprised three isokinetic concentric and eccentric maximal voluntary contractions (MVC) at randomised angular velocities of 100, 200 and 300 degrees.s-1. Before and after, the force:velocity relationship was determined bilaterally (angular velocities 0-300 degrees.s-1). There were no significant differences in the forces generated or relative electromyogram (EMG) activity after practice, although there was a trend for dynamic forces to increase. Beforehand, the bilateral eccentric MVC forces were lower than isometric (P < 0.0025); afterwards they were broadly similar. The agonist EMG was similar during isometric and eccentric contractions, but lower during concentric (P < 0.03). Antagonist EMG activity showed considerable individual variation, was similar during all contraction types and tended to be greater during dynamic contractions. These data indicate that neither central learning mechanisms nor total muscle activation strategies underlie the human failure to produce the expected high eccentric voluntary forces in humans.

Adult↗
PubMedDate not supplied

The effect of intraabdominal pressure and saline infusion on abdominal aortic hemorrhage.

Blood loss, survival, and hemodynamics were monitored for 1 hour or until death in 30 anesthetized pigs with a 0.5 cm abdominal aortic laceration. Eight animals (Group I) had no treatment; 7 animals (Group IA) had saline infusion at a maximum rate of 200 mls/min to maintain carotid artery pressure (CP); 8 animals (Group II) had intraabdominal pressure increased to 60 torr by pneumatic antishock garment (PASG) inflation; and 7 animals (Group IIA) had PASG inflation with saline infusion to maintain CP. Groups I and IA survived 9.5 +/- 4.2 minutes and 28.0 +/- 5.5 minutes, respectively (p less than 0.05). Groups II and IIA survived the 1 hour. Saline infusion (5400 +/- 120 mls in Group IA and 535 +/- 180 mls in Group IIA, p less than 0.05) increased blood loss without PASG inflation (1289 +/- 49 mls in Group I vs. 4840 +/- 1350 mls in Group IA, p less than 0.05) as well as with PASG inflation (438 +/- 64 mls in Group II vs. 1235 +/- 68 mls in Group IIA, p less than 0.05). CP could not be maintained in spite of saline infusion in Group IA but in Group IIA CP was maintained with saline infusion. In an otherwise fatal abdominal aortic laceration, increasing intraabdominal pressure improves survival and decreases hemorrhage. While saline infusion may prolong survival it increases hemorrhage both in the presence and absence of increased intraabdominal pressure.

Animals↗