Genetics

The angle of Muscle-bone attachment or muscle insertions and origins

The further away from that a tendon inserts from a fulcrum, the greater the biomechanical advantage and strength potential.

Lifter, A Tendon insert 1.2 inches away from the elbow

Lifter B Tendon insert 1.0 inches away from the elbow

Both lifters have to hold 40lbs at a distance of 12 inches from their elbows, keeping the lower arm parallel to the ground 

The force (efforts) necessary to maintain the weight in a static position F X FA = R X RA 

Lifter A must produce 400 lbs of force to hold 40 lbs

Lifter B must produce 480 lbs of force to hold 40 lbs.

Disadvantage When The Tendon inserts further from the joint.

If the Tendon Is inserted farther from the joint center, the muscle has to contract more in distance to make the joint move through a given range of motion, this translates into less speed. (Jason Cholewa)

• A person whose tendons are inserted on the bone closer to the joint center should be able to move the body part faster through the ROM.
• Aperson whose tendons are inserted on the bone further from the joint center should be able to lift heavier weights.

Muscles vs. Tendon Ratio

The shape of a muscle is determined by genetics, not by training.

You can’t change the points where the muscle inserts to make the muscle longer.

Muscles always work in pull, not push movement. The point of origin generally doesn’t move when you contract a muscle. Movement occurs at the point of insertion.

Long Muscle belly + Short Tendon = More Muscle Mass (Larger cross-sectional area contains a higher number of protein filaments and cross bridges, increasing the capacity to produce force)

Short Muscle belly + Long Tendon = Less Muscle Mass (Need to work hard to define Muscle, good for running or jumping in the case of the calf muscle)