My right hip was getting sore and I didn't know why so I focused on when it was hurting the most and realized it was from doing vertical edges walking backwards.. I have worked out that the human body is not meant to walk backwards every day
35 years of bricklaying taught me that doing the same movements over and over again every day will eventually take its toll on the body.
I decided about 3 months ago to re train myself in the art of edging, I started holding the shaft of the whippy in my right hand and walking forwards instead of backwards when doing vertical edges. At first I felt like a newbie, it felt really weird, so I only did it for about 1/3 of every lawn I did because I was so slow at it.
3 months later and I can honestly say I am just as fast at edging (doing a good job) walking forward as I was walking backward and the real benefit is I no longer have pain in my hip