Knees hyperextend during hold
Back of knees lock out aggressively, compressing the posterior knee structures.
Overactive muscles
QuadricepsGastrocnemius
Corrective work
Foam RollQuads / calves↗StretchWall soleus stretch↗Back of knees lock out aggressively, compressing the posterior knee structures.
Center of mass shifts posterior instead of stacking over mid-foot, reducing hamstring tension.
All the forward movement comes from the lumbar spine rather than hip flexion.