Our whole body works together to keep us alive, but it’s our bones and muscles working together that allow us to move. Bones, being comparatively rigid structures, are connected to each other in certain places, called joints, in such a way that the bony structure can move. Muscles are what cause and control movement.
Almost any exercise you can think of involves a muscle or muscles manipulating (bending or straightening) a joint or joints to achieve a goal involving movement. How we work, our muscles affect how healthy our joints are. It boils down to knowing what we’re doing. This means knowing not only our muscles but also every place they attach to. To affect a joint, a muscle has to cross it.
The muscles in our bodies that are involved with movement across one joint or two. Examples of one-joint muscles include, but are not limited to the soleus (in the lower leg, crossing the ankle joint), the short head of the biceps (front of the upper arm), and the short head of the triceps (back of the upper arm). Examples of muscles that cross two joints are: the quadriceps (front of the upper leg, crossing both knee and hip), the hamstrings (back of the upper leg, crossing both knee and hip) Gastrocnemius (back of the lower leg, crossing both knee and ankle), the long head of the biceps (crossing both elbow and shoulder), and the long head of the triceps (crossing both elbow and shoulder).
With all resistance exercise, stabilizing the whole body in alignment is critical. For one-joint muscles, it’s simply a matter of making sure the body is where it needs to be, and not moving, except for the one joint the muscle we are exercising crosses. Pretty straightforward, all things considered.
Two-joint muscles are another story. So many aspects of working the chosen muscle (usually a muscle group) have to be taken into account. We’re not just talking about doing the exercise efficiently; we’re also talking about safety. If you injure joint(s) or muscle(s), or both, when exercising, it puts a big crimp in your fitness goals.
Here are the two major points in working two-joint muscles:
Stabilization of One of the Joints
One joint has to be stationary while the other joint moves. If both joints move, the muscle just slides back and forth and never gets a decent contraction. The time, movement, and effort are all thrown into the “inefficient” if not the “waste” column.
Amount of Resistance You Use
At first, the amount of resistance, usually weight, you can use when effectively stabilized will be less than you can handle without stabilizing. Most often, this is because you no longer have other muscles helping the muscle you want to work. The muscles are stabilizing that other joint also have a bigger job to do than they are used to. Don’t worry, though. All the muscles involved strengthen quickly. You’ll soon be able to increase the amount of resistance you use.
Knowing how to work one-joint and two-joint muscle groups is a big part of an efficient workout, and achieving your fitness goals. Enlisting the help of a fitness professional to help learn and apply these concepts is well worth the time and money.