Posture vs. Phasic Muscles: Understanding the Key Differences

Posture muscles

* Also known as tonic muscles

* Maintain body posture and skeletal positions

* Slow to contract and relax

* Generate relatively low force

* Active for long periods of time without fatiguing

* Examples: soleus, gastrocnemius, erector spinae

Phasic muscles

* Also known as twitch muscles

* Produce rapid, powerful movements

* Contract and relax quickly

* Generate high force

* Fatigue quickly if held in a contracted state for too long

* Examples: biceps brachii, quadriceps, deltoids