Muscular Performance

Isotonic: the muscle contracts and shortens (muscle length changes), giving movement. Nearly all training you do is isotonic.

Isometric: muscle contracts but does not shorten, giving no movement. Muscle length doesn’t change, tension does. Ex. Pushing against a wall

Which one is A? B?

A single stimulus-contraction-relaxation sequence in a TWITCH A single stimulus-contraction-relaxation sequence in a muscle fiber.

LATENT PERIOD Between stimulus & response (contractile mechanism is not yet activated but calcium is beginning to spread) 0.001 sec.

STIMULUS Nerve message arrives

Sarcomeres shorten (active sites and cross bridges are interacting) CONTRACTION Sarcomeres shorten (active sites and cross bridges are interacting) .o4 sec.

RELAXATION Cross bridges detach 0.05 sec

Sending an impulse before muscle is relaxed SUMMATION Sending an impulse before muscle is relaxed Incomplete versus Complete Tetanus

TETANUS Sustained contraction due to continued stimulus

MUSCLE TONE Some fibers are always contracting to help maintain posture, balance, and firmness of muscles.

MUSCLE SPINDLES Specialized sensory cells responding to stretch-increases muscle awareness

Energy for Contraction 1- stored ATP: 3-6 seconds of energy 2- Creatine Phosphate (cp): 6-10 seconds of energy ADP+CPATP+creatine 3- Aerobic 36 ATP out of 1 glucose 4- Anaerobic- 2 ATP out of 1 glucose a. Lactic acid builds up and muscles fatigue b. Oxygen debt

Rigor Mortis: Muscle stiffness after death when you die, calcium seeps out of SR (In the absence of ATP the cross-bridges are not able to detach from the active sites and the muscle locks in the contracted position)

Enzymes eventually break down the myofilaments 15-25 hours later!

Cramp Lactic acid causes contraction without impulse