Experts Shared Their Top Amazon Fitness Gear — Under $150! — to Upgrade Every Workout

"Sandbags provide full-body, fat-blasting workouts," said ACE-certified personal trainer Lynn Montoya. You can even use water to fill this Ultimate Body Press Exercise Sandbag With Filler Bags ($60), which Lynn recommended for convenience and because the shifting water recruits even more muscles as you work out. Try them out with moves like farmer's carries and front- or back-loaded squats and lunges.