I have started doing interval training. For cardio to build my endurance. 10 Min warmup. 3 min run 3 min break repeat 4x 10 min cooldown. Started with minor lower back soreness. Minor soreness last night. This morning I could barely get out of bed I had to twist and kind of prop myself up.. I'm on motrin and using icy hot patches. Should I do an upper body routine tonight and walk instead of intervals until it goes away. Or take time off entirely until I am better? I'm working my way to the fitness standards for a police test in april so I need to be back in the game asap.