Muscle Structure and What it Means!

There are several different types of muscle structure. Ever wonder what it all means? Why are there such differences and what does it mean for those that strength train? At it's basic level there is the tendon-muscle belly-tendon complex. From there it gets a bit more complicated. It starts with the angle the muscle fibers makes with the tendon. From there it can become even more complex with the number and length of the muscle fibers.

So with all these differences you can guess that not all muscles are designed to do the same function and work. Let us start with the four types of structure.
1. Parallel-fibered
2. Unipennate
3. Fusiform
4. Multipennate.

1. Parallel fibered muscles the fibers run parallel to the line of action.
2. Pennate fibers run at an angle to the line of action. They can be slightly pennate and strongly pennate. Strongly pennate has a larger angle to the line of action.
3. Fusiform is a type of pennate.

Parallel fibers can be short and thick or long and thin. Short and thick fibers will pull harder (greater force) but produce less speed and work over a short range. Long and thin will shorten rapidly (thus speed), can have force over a large range, but slight force. These muscles are more suited for concentric/eccentric work.

Pennate muscle can develop a large cross sectional area. Larger cross section equals larger force. These will not be very fast and work over small range. These are more suited to concentric work.

Later I'll cover what muscles are parallel and which are pennate. But for now, hope that gets you thinking along the lines of muscle structure and function.