Muscular Muscular PerformancePerformance

• 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?

TWITCHTWITCH

A single stimulus-contraction-relaxation sequence in a

muscle fiber.

LATENT PERIODLATENT PERIOD

Between stimulus & response (contractile mechanism is not yet activated but calcium is beginning to spread)

0.001 sec.

STIMULUSSTIMULUS

•Nerve muscle arrives

CONTRACTIONCONTRACTION

• Sarcomeres shorter (active sites and cross bridges are interacting)

• .o4 sec.

RELAXATIONRELAXATION

• Cross bridges detach

• 0.05 sec

SUMMATIONSUMMATION

• Sending an impulse before muscle is relaxed

• Incomplete versus Complete Tetanus

TETANUSTETANUS

• Sustained contraction due to continued stimulus

MUSCLE TONEMUSCLE TONE

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

Question: If your muscle has little muscle tone will it appear solid or limp?

MUSCLE SPINDLESMUSCLE SPINDLES

• Specialized sensory cells responding to stretch-increases muscle awareness

Energy for ContractionEnergy for Contraction

1- stored ATP: 3-6 seconds of energy

2- Creatine Phosphate (cp): 6-10 seconds of energy ADP+CPATP+creatine

3- Aerobic 36 ATP out of 1 glucose

4- Anaerobic- 2 ATP out of 1 glucosea. 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!

CrampCramp

• Lactic acid causes contraction without impulse