I've taken two of the toughest things we like to do at Train Out Pain Chiropractic for metabolic conditioning and combined them. The result was awesome. Firehose conditioning then 1/2 way up the stairs. The rest interval was the walk down. Repeat for 5-8x depending on how your feeling. This was the last set of 6. It took about 8 or 9 minutes, but you could feel your metabolism on fire for hours after.