I like to do my interval training on a treadmill as the speed and distance is easily controlled. Am currently doing 800m interval at 6min/mile pace, followed by 400m @ 10min/mile. Repeating 6 times.
Trouble is, 6 min/mile is top speed of our machine. As I get better should I:
a/ Increase the length of each interval e.g. 1200m?
b/ Go for more intervals: 10 x 800m??
c/ Keep the same speed and distance but run uphill?
d/ Buy a decent treadmill? Other than this issue however treadmill works well.
Intervals are mainly aimed at improving 10k times.
I presume most treadmills go much faster than this? i.e 4 min/mile