Update:
This concept remains mostly true for generating active tension, but not for passive tension that develops at long muscle lengths. This passive forms leads to a unique form of growth by adding sarcomeres in-series to contract harder at weaker lengths. Therefore, using exercises that deeply stretch the target muscle, yet with a strength curve that still overloads close to the midpoint of a joint’s range of motion, is best.
Understanding joint ranges of motion reveals a huge insight.
The following are joint ranges of motion for the average person. Genetics, age, and activity affect the properties of connective tissues so these can differ slightly for each trainee. Various sources provide different values but having precise numbers is unnecessary. The starting values at 0° come from anatomical position.
Average Joint Ranges
Shoulder:
Flexion: 0° – 180°
Extension: 0°
Hyperextension: 0° – 45°
Abduction: 0° – 180°
Internal Rotation: 0° – 90°
External Rotation: 0° – 90°
Elbow:
Flexion: 0° – 145°
Extension: 0°
Forearm:
Supination (from neutral): 0° – 90°
Pronation (from neutral): 0° – 80°
Wrist:
Flexion: 0° – 90°
Extension: 0° – 70°
Radial Abduction: 0° – 20°
Ulnar Abduction: 0° – 30°
Hip:
Flexion: 0° – 120°
Hyperextension: 0° – 10°
Abduction: 0° – 45°
Adduction: 0°, though 30° – 45° across midline when unobstructed
Internal Rotation: 0° – 35°
External Rotation: 0° – 45°
Knee:
Flexion: 0° – 120°
Extension: 0°
Ankle (knee flexed and foot perpendicular to the leg):
Plantar Flexion: 0° – 45°
Dorsiflexion: 0° – 35°
Conclusions
The unexamined life is not worth living.
– Socrates
This may look like a simple and dull set of data that has no bearing on training but it reveals something important.
The length-tension relationship establishes that muscles generate the most tension in the middle range of the motion. The sites overlap best here. When stretched, they form less connections since the sites spread too far apart. When shortened, they bunch up like a ball of yarn. This is important because tension is the main stimulus of size and strength. Positions away from this also risk harming the joints due to less muscular support and other reasons.
You will find your muscle strongest at resting length, with the most force exerting occurs at the halfway point of the possible joint motion for many muscles.
The bench press places you at a horizontal position, forming a 90° shoulder flexion since you are perpendicular to the ground. This is halfway for the possible joint motion. The ideal grip for the bench press positions your arms 45° relative to the torso, halfway between internal and external rotation.
60° at the knees and the hips on the squat creates the most force, the midpoints between 0° and 120°, even the 90° works best for active tension. This means your hips furthest away from your knees, or the maximum moment arm. This calls into doubt that you need to squat ultra low. You may have some benefits to going slightly lower for the stretch reflex but this is not required.
Many muscles have multiple attachments. The biceps attach to the scapula and not just the elbow. This can mislead you because taking half of elbow flexion (72.5°) does not take into account shoulder position as well. With the shoulder leaning toward extension, you’ll find the ideal position is 90°, which gets hit perfectly on a row. (But take the halfway position between both joints and you would have the optimal length for tension, one position of the range of motion for the row.)
Our bodies seek out medium positions. This uses all the involved muscles and distributes stress across the joints. It avoids shearing forces that occur when one joint overpowers a movement. This also reveals bad exercises. Any heavy exercise that takes you far away from the middle angle can harm your joints and reduce tension. This includes, as an example, the overhead press that allows way too much shoulder flexion. Joint ranges of motion reveal that the ideal position for tension exists at the halfway for these ranges. The basic three therefore will allow you to get strong and stay safe.