The Force-Velocity Relationship of the Soleus Muscles of Mice During After-Loaded Isotonic Contractions and After-Loaded Isotonic Releases
Ward, Christine E.
MetadataShow full item record
Hypotheses were tested that a muscle stimulated at a frequency that elicited a maximal rate of force development (dP/dto) was fully activated during after-loaded isotonic contractions by the time the muscle developed the force necessary to displace the after-load and consequently the shortening velocity was maximum. whereas a muscle stimulated at a rate that elicited maximum tetanic force (Po) was not fully activated and under similar circumstances could not displace after-loads at maximum velocities. As controls for fully activated muscle, the same muscles were stimulated to develop Po and were then released to each after-load. Soleus muscles from 14 mice were stimulated directly in vitro at 25º C. Shortening velocities of each muscle were measured at 13 different after-loads using 4 different protocols: stimulation at a frequency that produced Po (approximately 90 Hz) with an after-loaded isotonic contraction: stimulation at 90 Hz to Po with a quick-release to each after-load; stimulation at a frequency that produced dP/dto (approximately 250 Hz) with an after-loaded isotonic contraction; or stimulation at 250 Hz to Po with a quick-release to each after-load. The maximum velocity of unloaded shortening (V max) was extrapolated from the force-velocity relationship. A significant difference was observed between the V max of isotonic contractions at 90 Hz (V max=4.17±0.l4 Lf/s) and that at 250 Hz (V max=4.82±O.l4 Lf/s). Based on a repeated measures analysis of variance of the velocities at 13 after-loads, I concluded that soleus muscles were not fully activated when stimulated at a frequency that produced Po unless stimulated to Po and subsequently quick-released to the after-loads. whereas muscles stimulated at a frequency that produced dP/dto were fully activated in all cases except during isotonic contractions at after-loads above 0.40. Furthermore, the extrapolation of measured velocities of a whole muscle to V max is not valid and the practice should be discontinued.
Showing items related by title, author, creator and subject.
A review of swim bladder ventilation of physoclistousfish species: short and long-term survivorship after venting and comparison to alternate recompression methods Voss, Christine (Kalamazoo College, 2010)Pressures on marine resources continue to increase, including the decline of fish populations. The fishing industry has acknowledged the importance of maintaining these fish populations and in response has increased ...
Hemodynamic Response and Support After Deep Hypothermic Circulatory Arrest in Neonatal Patients Undergoing Surgical Repair of Congenital Heart Defects Howe, Michael (Kalamazoo College, 2003)Corrective surgery is a common and often necessary treatment for children born with congenital heart defects. These are defects in the gross anatomy of the heart and often affect the circulation of oxygenated blood through ...
A Quantitative Study on the Uptake and Retrograde Transport of Horseradish Peroxidase by Adult Rat Phrenic Motorneurons after Axonal Crush Lesions Furicchia, James Vincent (Kalamazoo College, 1983)The effect of both a double and single lesion crush on the uptake and retrograde transport of horseradish peroxidase (HRP) in phrenic neurons was studied quantitatively. The extent of HRP uptake and transport gives an ...