An elbow pulled both ways.

Can two pulling muscles hold one elbow still?

Setting up the mechanism…

Biceps torque: 2.00Nm
Triceps torque: 3.00Nm

Net elbow torque: -4.00Nm

Fit the specimen and set conditions before running.

Can two pulling muscles hold one elbow still?

A tendon transmits a pull. Biceps and triceps turn the elbow in opposite directions, and their moment arms differ. The hand load contributes its own torque.

τ = 0.04 Fbiceps − 0.03 Ftriceps − 0.30 Fload

What this model simplifies

Quasi-static elbow at 90°. Fixed moment arms and ideal tendons; no muscle recruitment, strength or exercise prescription.

Read the source · openstax.org ↗

Put it to work.

Hold the elbow with both muscles pulling and less than 0.1 Nm net torque.

Make it work.

Balance muscle torque against the hand load.

Run

Fine adjustments 3

Biceps pullN

Triceps pullN

Hand loadN

An elbow pulled both ways.

Can two pulling muscles hold one elbow still?

Loading the experiment…

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Human anatomy and physiology

An elbow pulled both ways.

Can two pulling muscles hold one elbow still?

Setting up the mechanism…

Biceps torque: 2.00Nm
Triceps torque: 3.00Nm

Net elbow torque: -4.00Nm

Fit the specimen and set conditions before running.

Can two pulling muscles hold one elbow still?

A tendon transmits a pull. Biceps and triceps turn the elbow in opposite directions, and their moment arms differ. The hand load contributes its own torque.

τ = 0.04 Fbiceps − 0.03 Ftriceps − 0.30 Fload

What this model simplifies

Quasi-static elbow at 90°. Fixed moment arms and ideal tendons; no muscle recruitment, strength or exercise prescription.

Read the source · openstax.org ↗

Put it to work.

Hold the elbow with both muscles pulling and less than 0.1 Nm net torque.

Make it work.

Balance muscle torque against the hand load.

Run

Fine adjustments 3

Biceps pullN

Triceps pullN

Hand loadN