You are about to perform a manual muscle test on the flexor pollicis brevis. In which direction should you apply the force?
1. Along the anterior aspect of the proximal phalanx of the thumb
2. Along the anterior aspect of the distal phalanx of the thumb
3. Along the posterior aspect of the proximal phalanx of the thumb
4. Along the posterior aspect of the distal phalanx of the thumb
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