I used to have a very long gravel driveway that needed to be weeded. These weeds were not so much in semi-soft dirt as they were growing in between the rocks. It took a long time to weed as the weeds were very far apart and my scooter couldn't travel smoothly over the gravel driveway which meant I had to pick the scooter up and walk with it to the next weed. Once started I had to get done and that was when I experienced the worse back spasms in my life.
Forward 15 years later, no more gravel driveway and much smaller garden, I have learned that I can weed only for a set amount of time before my back would start to fatigue. I set a timer on my wristwatch for 15 minutes and carry a 2.5 gallon bucket. Whichever gets filled first, the bucket or the alarm on the allotted time dictates when I stop. And then, it's inside the house for an ice pack on my lower back. We aren't getting new backs or bodies at any milestone birthdays so I have to take care of mine now!