Each joint action, with the role and emphasis the graph assigns each muscle. These are qualitative anatomical labels, not measured muscle activation.
Knee extensionprimary action
Vastus lateralis (prime mover, high emphasis); Vastus medialis (prime mover, high emphasis); Vastus intermedius (prime mover, high emphasis); Rectus femoris (synergist, moderate emphasis)
Hip extensionprimary action
Gluteus maximus (prime mover, high emphasis); Adductor magnus (prime mover, high emphasis); Biceps femoris long head (synergist, low emphasis); Semimembranosus (synergist, low emphasis); Semitendinosus (synergist, low emphasis)
Spine extensionsecondary action
Erector spinae (stabilizer, high emphasis); Rectus abdominis (stabilizer, high emphasis); Transverse abdominis (stabilizer, moderate emphasis); External oblique (stabilizer, moderate emphasis)