MMT-8

MMT-8 (Manual Muscle Testing–8) is a standardized bedside strength assessment used in idiopathic inflammatory myopathies (including dermatomyositis) and endorsed in the IMACS outcome core set. It focuses on 8 representative muscle groups to quantify global, proximal-predominant weakness and track change over time.

What muscles are tested (the “8”)

The MMT-8 subset tests these muscle groups:

1. Neck flexors
2. Deltoids (shoulder abduction)
3. Biceps (elbow flexion)
4. Wrist extensors
5. Gluteus maximus (hip extension)
6. Gluteus medius (hip abduction)
7. Quadriceps (knee extension)
8. Ankle dorsiflexors

How it’s scored

• Each muscle group is graded on a 0–10 modified Kendall scale (0 = no contraction, 10 = normal strength).
• The classic trial convention is unilateral testing (typically the right side unless not testable), giving a total score 0–80.
• Some forms also report a bilateral total, yielding a 0–150 maximum (because of how neck flexors are handled plus bilateral limb testing in that format).

How to interpret directionally:

• Higher MMT-8 = stronger (less weakness).
• In many active myositis cohorts, baseline values can be “high” (e.g., 70s) even when patients are clinically symptomatic—because MMT has ceiling effects and is less sensitive to fatigue/endurance deficits than functional measures.

Why clinicians/trials use it

• Fast, bedside, repeatable way to follow treatment response or deterioration.
• It correlates with other myositis activity and function measures (imperfectly) and is widely used in outcome sets for trials.