— Green Thumb, Bad Back
I feel your pain, literally. Gardening is hard work and can really do a doozy on your spine. I recently did an entire Pilates session with a gardener dealing with back pain and will share my tips with you when you continue reading.
Three things can really help in preventing back pain: using proper bio mechanics, strengthening your arms and legs, and really working your core.
The ligaments that line the back of the spine overstretch a bit when we round forward for long periods of time, like when weeding. This means you want to work in a flat or neutral back as much as possible, which means sticking out your butt. Every time you bend forward, whether you're on your knees or feet, hinge at your hip joint and do not round your back. It helps to think of your torso as a solid unit rather than an articulating spine. Remember to lift with your legs, not your back.
I think it is great that you're already going to the gym, but be sure to use your proper bio mechanics when you strength train. Skip the machines and go for free weights, since these moves are much more similar to activities you do while gardening. Strengthen your legs with all kinds of squats. Emphasize keeping your back neutral and slowly increase the weights you use, and vary the types of weight you use too. Try holding a weighted medicine ball or a plate weight to your chest while you squat and lunge. Another, more subtle trick is using your pelvic floor muscles to go from kneeling or squatting to standing. These small muscles at the base of the pelvis are part of your core and can help keep your pelvis and lower back more stable. Having stronger arms and a stronger upper back will help your gardening too. The bent over row is a great exercise to add to your routine.
Having a strong and stable core helps keep stress off your spine when lifting and carrying heavy objects, not to mention shoveling. Start with planks and elbow planks and work your way up to these more challenging core exercises. When strength training other parts of your body, remember to work your core to stabilize your spine — think of the abs and the spinal muscles sandwiching your vertebrae to keep them in place.
If your back starts to bother you while you're working, take a moment to relax your spine with a little cat and cow — it feels great. When you're done with your day, stretch your legs, arms, and chest. After a day of gardening, I like to do a nice relaxing spinal twist.
Good luck and have fun helping things grow!