How do I activate my multifidus muscle?

[physiobob]

Don't be so pedantic! The multifidus works to support the spine during flexion rotation movements, Interestingly I remember doing some EMG studies in the early 90's that showed myoelectric silence after 90 degrees forward bend. (sorry no RCT I can cite on that one). Maybe it was due to a contraction in that position might be dangerous for the lumbar discs.

Anyway why would anyone want to work multifidus in isolation? It is not used in isolation and therefore that would be training a non-functional movement pattern which would not carryover necessarily to functional activity. It would want to train it go play some tennis and hit a few hundred backhands.

A simple active exercise would be 4 point kneeling. Then opposite arm flexion and leg extension. You can progress it to then take the extended elbow to the opposite knee (slowly) and then faster while maintaining balance. Sorry no RCT on that either. To be honest there are dosens of exercises that can recruit this in synergy with general movement. A few images attached non of which are my fav's but give a starting point for ideas