Muscle Length vs. Point of Overload in Exercise Selection

Training a muscle at a longer length and overloading the lengthened portion of an exercise are not the same thing.

Muscle length is influenced by joint position. The point of overload is determined by the resistance curve. These factors can overlap, but they do not always create the same training stimulus.

When coaches fail to separate muscle length from point of overload, they can misinterpret what an exercise is actually providing.

Muscle Length and Point of Overload Represent Different Ideas

One of the most common misunderstandings in exercise selection is assuming that training a muscle at a longer length and overloading the lengthened position are the same thing.

They overlap conceptually, but they represent different ideas.

A muscle can be placed at a longer length because of joint position, while the exercise itself may overload the muscle relatively evenly throughout the range of motion.

In contrast, a muscle can be placed at a shorter overall length but still experience the greatest overload in the lengthened portion of the exercise because of the resistance curve.

This distinction is important because exercise selection is not only about which muscle is being trained. It is also about:

• Where the muscle is being trained
• Which joint positions are being emphasized
• Where tension is highest
• Which region of the range of motion receives the greatest mechanical demand

What Determines Muscle Length?

Muscle length refers to the position of a muscle based on the joints it crosses.

For biarticular muscles, this becomes especially important because changing the position of one joint can lengthen or shorten the muscle before the repetition begins.

The hamstrings are a good example. Because they cross both the hip and the knee, hip flexion and knee extension both influence hamstring length.

A seated leg curl places the hip in flexion, which lengthens the hamstrings proximally before knee flexion occurs. This means the hamstrings are trained at a relatively longer overall muscle length compared to a prone or standing leg curl variation.

The biceps provide another example.

Because the long head of the biceps crosses the shoulder and elbow, humeral position changes the starting length of the muscle.

An incline curl places the humerus behind the torso, which lengthens the biceps before elbow flexion begins. A preacher curl places the humerus in front of the torso, which shortens the biceps at the shoulder before the repetition starts.

These joint positions influence muscle length.

However, they do not automatically tell us where the exercise is hardest.

What Determines the Point of Overload?

The point of overload is determined by the resistance curve.

The resistance curve describes where in the range of motion the exercise provides the greatest external demand.

This is influenced by:

• The implement being used
• The line of force
• The moment arm
• The CAM profile
• The relationship between the load and the working joint

This is why two exercises can train the same muscle but produce very different loading experiences.

One exercise may place the muscle at a longer length while providing relatively even overload throughout the movement.

Another may place the muscle at a shorter overall length while concentrating most of the overload in the lengthened portion of the range.

This is the distinction coaches need to understand.

The Hamstrings: Seated Leg Curl vs. Nordic Curl

The seated leg curl is commonly discussed as a lengthened-position hamstring exercise, and for good reason.

Because the hip is flexed, the hamstrings are placed under greater length before the knee flexion action begins. Compared to lying or standing leg curl variations, the seated leg curl generally exposes the hamstrings to greater muscle lengths.

However, the seated leg curl is also usually performed on a machine with a CAM.

The purpose of the CAM is to manipulate the external resistance profile so the exercise can provide a more appropriate challenge throughout the range of motion.

Rather than the exercise becoming extremely overloaded in one region and underloaded in another, the CAM helps distribute demand more evenly across the movement.

This means the seated leg curl trains the hamstrings at longer muscle lengths, but it does not necessarily overload only the lengthened position.

The muscle may be lengthened because of hip position, while the exercise provides more evenly distributed overload because of the machine’s resistance profile.

How the Nordic Curl Differs

The Nordic curl creates a different scenario.

It does not place the hamstrings in the same degree of proximal length as a seated leg curl because the hip is not flexed.

From a muscle-length perspective, the hamstrings are not being trained in the same long-length position created by hip flexion during the seated leg curl.

However, the resistance curve of the Nordic curl places a very large demand on the hamstrings near the lengthened portion of knee extension.

As the athlete lowers toward the floor and the knee extends, the external moment arm increases dramatically.

The exercise becomes hardest when the hamstrings are being challenged near the distal portion of the muscle-tendon unit and at longer knee-flexor lengths.

This is why the Nordic curl is often associated with high levels of distal hamstring stress.

It is not because the entire hamstring complex is placed at the greatest possible muscle length from the start of the exercise. It is because the resistance curve heavily overloads the hamstrings near the lengthened portion of the knee-flexion range.

The seated leg curl is a longer-muscle-length exercise with a more evenly distributed machine-based resistance profile.

The Nordic curl is not necessarily a longer-muscle-length exercise in the same way, but it provides a very large overload in the lengthened portion of the knee-flexion range.

Both exercises are valuable.

They are not valuable for the exact same reason.

The Biceps: Incline Curl vs. Scott Curl

The same concept can be seen when comparing the incline curl and Scott curl.

The incline curl places the humerus behind the torso.

Because the long head of the biceps crosses the shoulder, this shoulder position places the biceps under greater stretch before elbow flexion begins.

From a muscle-length perspective, the incline curl trains the biceps at longer lengths than a curl variation performed with the humerus beside or in front of the torso.

However, the point of greatest overload in the incline curl is not necessarily in the most lengthened position.

Because the exercise is performed with a dumbbell and the line of force is gravity, the resistance profile changes throughout the range of motion.

The external moment arm is relatively small near the bottom of the movement and increases as the forearm approaches a more horizontal position.

The greatest overload typically occurs higher in the range, often just after approximately 90 degrees of elbow flexion.

This means the incline curl places the biceps at a longer muscle length, but the greatest point of overload occurs in a more shortened range of motion.

How the Scott Curl Differs

The Scott curl creates the opposite scenario.

In a Scott curl, or preacher curl, the humerus is positioned in front of the torso.

This shoulder flexion shortens the biceps at the shoulder compared to an incline curl.

From a muscle-length perspective, the biceps are not being trained at the same long length created by the incline bench position.

However, the resistance curve of the Scott curl places the greatest demand near the bottom of the movement.

Most of the tension occurs within the bottom third of elbow flexion. This places significantly more stress on the elbow flexors in the lengthened portion of the elbow-flexion range, especially around the distal portion of the elbow flexors.

The distinction becomes clear.

The incline curl trains the biceps at longer muscle lengths because of the position of the humerus, but the greatest overload occurs higher in the range of motion.

The Scott curl trains the biceps at shorter muscle lengths because the humerus is in front of the torso, but the greatest overload occurs in the lengthened portion of the elbow-flexion range.

One exercise emphasizes muscle length.

The other emphasizes lengthened-range overload.

Those are not the same thing.

Why This Distinction Affects Exercise Selection

This distinction has major implications for program design.

If the goal is to expose a muscle to longer lengths, joint position becomes a primary consideration.

For the hamstrings, hip flexion becomes relevant. For the biceps, humeral position becomes relevant. For the triceps, shoulder position becomes relevant. For the rectus femoris, hip position becomes relevant.

However, if the goal is to overload a specific portion of the range of motion, the resistance curve becomes the primary consideration.

This is where many programming mistakes occur.

A coach may select an exercise because it places a muscle at a longer length and assume it also overloads the lengthened position.

In some cases, that may be true.

In other cases, the exercise may place the muscle in a longer position while still providing the greatest challenge elsewhere in the range.

Similarly, a coach may select an exercise that does not appear to train the muscle at the longest possible length, but the resistance curve may still overload the lengthened portion of the movement very aggressively.

The adaptation produced by an exercise is influenced by both factors.

Muscle length determines the position from which the tissue is being trained. The resistance curve determines where the highest external demand occurs.

The combination of these variables determines the actual stimulus profile of the exercise.

This is why exercise selection needs to be more specific than simply labeling movements as lengthened, shortened, or mid-range.

Those labels can be useful, but they are incomplete unless the resistance curve is also considered.

Applying the Distinction in Program Design

When selecting exercises, it can be helpful to separate two considerations.

The first is the muscle length created by joint position.

The second is where the exercise places the greatest mechanical demand.

These factors can overlap, but they do not always point to the same conclusion.

A seated leg curl places the hamstrings at longer muscle lengths because of hip flexion, while the CAM may create more even overload throughout the range.

A Nordic curl does not place the hamstrings in the same long-length hip position, but the resistance curve creates a large overload near the lengthened portion of knee extension.

An incline curl places the biceps at longer muscle lengths because the humerus is behind the torso, but the dumbbell resistance curve often creates the greatest challenge higher in the range.

A Scott curl places the humerus in front of the torso, shortening the biceps at the shoulder, but the resistance curve creates the greatest overload near the bottom portion of the movement.

Understanding these differences allows coaches to build more complete exercise rotations.

If the goal is hypertrophy, exposing a muscle to different lengths and different points of overload may be valuable across a training phase.

If the goal is strength through a specific range, the resistance curve may need to be matched more closely to the limiting portion of the movement.

If the goal is injury risk reduction or tissue preparation, the coach may intentionally select exercises that expose the tissue to high tension in specific ranges.

This is not about choosing one category as superior.

It is about understanding what each exercise provides.

The seated leg curl and Nordic curl are both hamstring exercises, but they do not create the same stimulus.

The incline curl and Scott curl are both biceps exercises, but they do not overload the same region in the same way.

A more complete program can use both concepts.

It can include exercises that train muscles at longer lengths, and it can include exercises that overload specific points in the resistance curve.

Sometimes the same exercise will do both. Sometimes it will not.

More Precise Exercise Selection

Training a muscle at a longer length and overloading the lengthened position are not the same thing.

Muscle length is determined by joint position. The point of overload is determined by the resistance curve.

Confusing the two can lead coaches to misunderstand the stimulus an exercise provides.

An exercise may place a muscle in a lengthened position without maximally overloading that position. Another exercise may place the muscle in a shorter overall position while still creating the greatest demand in the lengthened portion of the range.

This is why exercise selection needs to consider both anatomy and mechanics.

The question is not only, “What muscle does this train?”

The better question is, “At what length is this muscle being trained, and where is this exercise actually hardest?”

That distinction is where exercise selection becomes more precise.