The sprints themselves are TOUGH but I make it harder by pretty much exhausting myself with my warm up and then doing the sprints UPHILL. It's only a 5-10 minute run for the warm up, but bear in mind I am super unfit! I run between .4 of and a full mile, have a couple of minutes break and then get straight into the sprints.
Because I have been doing this early in the morning mainly, and therefore need to shower and get ready for work afterwards, I opted for a shorter burst but a shorter rest than I started with a couple of weeks ago. Just to get it out of the way, rather than it taking over half an hour total. I decided on 20 second bursts but only a 1 minute rest (I did 30/2 last time before I hurt my back and gave up!). This is extremely tiring but it's only 8 times, so I just grin and bear it and get in with it!
The best invention ever has got to be the arm wallet that I picked up from Amazon for only a few quid, so I can carry my keys, Vaseline (my lips get SO dry when running, not sure why!) and phone without holding them, leaving my hands free for a water bottle. This has been a godsend!
So far so good, early days as I said but I'm impressed so far, mainly with the fact that I have been getting up at sub 7am and going running ;) but also what seems to be some pretty good results so far!
Next week, I am going to up the sprints to 30 seconds and have a 1.5 minute rest, and the following week 30/1. Will see how it goes!!