No offence meant but as one old f@rt to another were you using a loop handle whipper? - I put my back out in a place I haven't had trouble with before about 10 days ago - the smoking gun is my new toy - the Ego whipper - loop handle - slight stooped posture - crab walk - crooked arms with weight on shoulders, elbows, hands - no shoulder strap
so I went back to my bull horn handle Honda with shoulder strap for a bit while the chiropractor works his magic - chalk and cheese - whipping for almost any length of time is effortless - I remembered why I've used nothing else all the time I've mowed.
I'll go back to the Ego soon because it's so damn good but I'll keep the Honda for anything other than a quick edge on a suburban block
Can't do much about the summer tho - we're in a dream patch here crisp in the mornings and ~26-27.