Muscle Lengths: The Basics

First of all, why is it important to train muscles in different lengths and establish Active Range of Motion?

It's important to train the different muscle lengths because we are able to train more range of motion for that specific muscle, establishing strength and control in both active end ranges of the motion where most injuries occur (especially the lengthened end range).  

Before we discuss terms that describe the muscle being trained as "shortened" or "lengthened", we must understand Active Range of Motion. Active Range of Motion plays a large role when it comes to mastering and executing your movements, specifically the "lengthened" movements and positions. Let's briefly discuss Active Range of Motion before we get into the muscle lengths.

Every muscle in the body has a range of motion (ROM) that it can actively go through. This is called the Active Range of Motion. The Active ROM refers to the ability of the individual to move a joint through a range of motion without any assistance, while in complete control. Each individual will have different Active ROM due to structure, mobility, or other limitations.

It's important to be aware of the Active ROM that you have access to because Active ROM dictates the end ranges of your exercises that you can achieve safely. This is different for everyone. Depending on where the movement is overloaded, it could be easier to go outside of that Active ROM because there is resistance that could be forcing the movement outside of what the individual has control over.

Now that we have established the importance of Active Range of Motion, we can dive into some examples of muscle lengths and the application of the above. 

Terms like "shortened" and "lengthened" are becoming the norms for discussing exercises. You might have heard people say, "training the biceps in the lengthened position" or "training the quadriceps in the shortened position". What does this all mean? Just referring the muscle lengths itself, we can place tension on the muscles in more "contracted" or more "stretched" positions. To familiarize yourself with the following sensations, try the following for the biceps.

Since the biceps cross the elbow joint as well as the shoulder joint, we can find the end ranges for the biceps by knowing Active ROM for the shoulder joint. We can find Active ROM for the shoulder joint for shoulder flexion (arm going overhead) and shoulder extension (arm going behind torso). To find the short position of the biceps, place upper arm above shoulder joint by going into active ROM for shoulder flexion, but stabilize the shoulder and contract the biceps hard. You can feel a hard contraction and might even get the sensation of a "cramp", as this is a shorter muscle position (the goal is never to get the "crampy" sensation during a movement). If we want to find the lengthened position for the biceps, we must first establish Active ROM at the shoulder joint for shoulder extension. Once we find the Active ROM for shoulder extension, we can set the bench up to mimic the Active range for shoulder extension. 

Refer to the images below applying physics to the biceps curl. We will elaborate on torque in another blog, but I just wanted to show the example that just because we are training a "lengthened" movement does not mean the movement is always overloaded in the lengthened position. The Incline Dumbbell Curl is a Lengthened Biceps movement but overloads the movement in the mid-range. The blue dot represents the axis of rotation, the red arrow indicates the resistance from the dumbbell, and the green line represents the distance between the two. As you can see in the second photo, the green line is the greatest distance, indicating that the movement is the most difficult at the mid-range due to increased torque needed.

The resistance is nearly in line with the axis, not generating a whole lot of force at the elbow joint.

As the resistance gets further away from the axis, the biceps have to generate more force (overloaded in the mid-range).

Finishing the movement, the resistance gets closer to the axis, which results in less torque needed. This movement gets slightly easier at the top.

Lets's take a look at another "lengthened" movement. When performing the Romanian Deadlift, we are lengthening the hamstrings while the load is pulling straight down. The Romanian Deadlift is lengthening the hamstrings, but also due to the nature of the movement, we're overloading the lengthened position of the lengthened range. This is why establishing individual Active ROM is extremely important for lengthened movements. Everyone's depth on the Romanian Deadlift will vary. Since the resistance is most difficult at the bottom of the movement, staying within the Active ROM established is extremely important or else we could be loading tendons, joints, compensatory muscles, and most importantly, risking injury. 

Even though we are training the Biceps and the Hamstrings both in a lengthened muscle position, we must look at the movement itself to establish where in that movement is the most overload. Training a lengthened movement doesn't always means it's a lengthened overload.

Now, let's look at the Hamstring Curl. We're going to use the Lying Hamstring Curl for our example for the shortened hamstring movement. Let's assume this machine is set up so that the weight gets heavier in the shortest position. In the Lying Hamstring Curl, we are driving the heel towards the glutes shortening the hamstrings. If the load is too heavy, we won't achieve a fully shortened hamstring. This is why we must be aware of the Active ROM we established in the beginning. If we are not training to the full Active ROM of the muscle, then we are missing out on hypertrophy, as well as strengthening the end range.

Hopefully this article helps you understand the jargon of shortened and lengthened, the relationship between Active Range of Motion, and how levers play a large role in overloading positions.

What are the implications that go along with lengthened and shortened movements? Stay tuned for the next article.

Share this post