Having flown the 139 for over two years offshore with an average of 6 to 8 sectors a day I cannot complain of having back pain just to set the parking brake.
There are other factors to consider:
If you are completing several fairly short range sectors, why are you releasing the brake at all, is it not holding pressure as listed in the RFM?
Perhaps you ought to check on that.
We, as helicopter pilots have ingrained in our genetics to whine and complain about things that disrupt our standard routine, no matter how small and insignificant those things may be.
Oh, and yes, just standing on your feet against a wall and lifting yourself on your toes ten or twelve times produces enough exercise to overcome the need for a back brace just for setting the parking brake in the 139.
In my opinion is a far more strenuous adventure trying to reach for those "well thought of" side steps to climb on top of the aircraft during your pre-flight inspection.