At the S1 level, which muscle is 3/5?

• A. Hip abductors
• B. Hip extensors
• C. Plantar flexors
• D. Abdominals

Answer: (A)

In manual muscle testing, a 3/5 strength means the muscle can move the joint through the full range against gravity but cannot withstand external resistance. At the S1 motor level, the hip abductors (gluteus medius/minimus) are the muscle group tied to that level because their nerve supply includes fibers from S1. These muscles are often borderline at this level: they can abduct the hip against gravity, but they’re not strong enough to hold up against added resistance, which fits a 3/5 grade.

Plantar flexors are also S1, but they tend to be stronger in many people, so they’re more likely to score higher than 3/5. The abdominals are innervated by nerves higher up, not S1, so they aren’t used to gauge the S1 motor level. Hip extensors involve S1-S2 and can vary as well, but the hip abductors best fit the described strength at S1, making them the best choice for a 3/5.