Question Regarding net moment generating at shoulder joint of arm26 model

[Rajnish kumar]

I am running ID for arm26 model for arm26_elbow_flex.trc.
I am getting net moment at shoulder joint also.
It seems like it is reaction moment generating to balance the net moment at elbow joint.
The plots of elbow flexion and shoulder elevation coordinates(figure-1) and the corresponding moment(figure-2) are attached.
Am i thinking correct? please help.Thank you.

[Thomas Uchida]

There must be a torque at the shoulder to keep the humerus stationary as the elbow flexes.