ExRx.net > Kinesiology > Articulations > Joint
Bending the joint resulting in a decrease of angle; bringing forearm toward upper arm.
Straightening the joint resulting in an increase of angle; bringing forearm away from upper arm.
Also see Forearm. Mentioned articulations occur during concentric phase of exercise video examples.
The Surprising Reason our Muscles Get Tired
Weight Training Applied Research Findings
Westside Barbell Program
Workout Creation Instructions