How many muscle groups are tested in the MRC-SS, and how are the scores combined?

• A. Six muscle groups are tested bilaterally; each side is scored separately and the results are summed for a total score.
• B. Six muscle groups are tested bilaterally; scores are averaged between sides.
• C. Twelve muscle groups are tested on a single side.
• D. Three muscle groups are tested unilaterally and the scores are summed.

Answer: (A)

In the MRC Sum Score, strength is assessed for six key muscle groups on each side of the body. You test and score six muscles bilaterally—shoulder abduction, elbow flexion, wrist extension, hip flexion, knee extension, and ankle dorsiflexion on both the right and left sides. Each muscle group on each side is graded from 0 to 5, and the twelve individual scores are added together to yield a total score, with a maximum of 60. This means the score reflects bilateral strength across all key muscle groups, not an average or unilateral total.