16.423J/HST515J Aerospace Biomedical Engineering and Life Support Prof. Newman
Prof. Newman
Summary
Muscle Performance Facts [McMahon, Muscles, Reflexes and Locomotion, 1984]
1. In shortening, the relationship between the Force and Velocity is (Hill's Curve - know
this!!):
(T+a)(v+b) = (T
0
+a)b Hyperbolic Form
? muscles shorten more rapidly against light loads than they do against heavy ones
? muscles which are actively shortening can produce less force than those which
contract isometrically.
2. There is a discontinuity in the slope of F-V curve at zero velocity.
3. Active muscle yields when the load exceeds about 1.8 T
0
(T
0
- Tetanus tension).
4. Hill's observations of the Fenn effect give a linear relation between total rate of energy
liberation and tension.
Fenn = muscle produces a certain extra heat when it shortens a given distance,
whether shortening velocity is fast or slow.
5. Muscle shortening should be based on the relative motion of sliding filaments because:
A. A-band width stays constant during stretch and shortening
B. A-band disappears when myosin is dissolved away
C. Actin filaments begin at Z-line, run through I-bands into A-band, but stop
before reaching H-zone (muscle at rest length)
I-band is entirely actin filaments
H-zone is myosin filaments
6. Muscular energy liberation should be based on the splitting of a high-energy phosphate
as actomyosin attachments separate.