I´m starting to incorporate some intervals into my training and I just wondering whether it made a difference doing the "sprints" , whether I´m on the bike or running, on the flats or uphill. Obviously when I "sprint" uphill its much easier to get my heart rate/work rate close to the maximum, but is it better to sprint on a flat so that I get used to the speed? Not so bad running, but definitely on the bike my heart rate stays higher climbing hard for 3 minutes or whatever than going as fast as I can on a flat.
I have some fairly big climbs here so it would be easy for me to sprint solely uphill for a few minutes at a time.
As always all advice appreciated.