Do I need strong arms before trying yoga?

No. You come to yoga with the strength you have, and the practice can help you build from there. Weight-bearing postures can be changed by using a wall, placing the knees down, reducing the lever length, using blocks or spending less time in the position.

A good teacher does not use Chaturanga, arm balances or long downward-facing dogs as an entrance examination. Technique should develop before fatigue destroys alignment. Over time, repeated intelligent loading can build shoulder, arm and trunk strength.

Yoga asks for progressive effort, not performance. The posture should serve the practitioner; the practitioner is not there to serve the posture.