The majority of the muscle fibers in the skeletal muscles of the leg of a long distance runner is expected to have:
1. adaptation for sudden outburst of activity
2. primarily anaerobic source of energy
3. numerous mitochondria
4. large deposits of glycogen

Identify the incorrect statement:
1. A muscle fiber contracts in an all-or-none fashion.
2. A slight delay occurs between the reaching of impulse at the neuromuscular junction and muscle contraction.
3. Using more motor units will increase the overall force of contraction.
4. When a person is fully at rest, none of her muscles are contracting.