It is perfectly safe to shave those areas, assuming you can somehow see your lower back and reach around to shave it (or have someone do it for you.) Shaving will not cause the hair to grow in thicker, it is a myth. I started shaving my back using a full-length mirror and learned to do it by touch eventually. (Shaving above the shoulder blades is very difficult and not everyone is flexible enough to do it.)
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Treatment details: genetic male heavy facial/body hair no hrt, type III skin
Laser: Cutera Coolglide 10 treatments/14 months full face 33J 10cm spot size
Pro Electro: 22.75 hours Apilus Jr + Platinum flash + picoflash thermo upper/lower lip + chin
DIY Electro: 144.50 hours Apilus SM-500 microflash arms/legs/hands