Friday, January 18, 2008

Fitness: Trying Jenny's interval running program

Jenny's personal trainer has her doing a run/sprint/walk cycle - 2min run, 1min sprint, 2 min walk.

Here are my results:

(click to expand)

The horizontal axis are laps. The watch only records one reading per lap so I counted each run/sprint/walk section as if it were a lap. It would be better if the horizontal axis were scaled by time, but Polar doesn't give that option. Oh well. What they do provide is already pretty freakin' cool.

The red line shows my heartrate (as a percent of max) at the end of each "lap". So, for example, at the end of lap 15, my heartrate was around 75% of max. The actual average for that two minute walk section would've been higher than 75% (because the entire time my heartrate was descending from the 90% peak achieved in the previous sprint section).

The yellow bar graphs show my average speed per lap. You can clearly see the run/sprint/walk cycles.

The idea of this interval training is to force your body to constantly switch between aerobic and anaerobic levels of exertion. But as you can see my heartrate was remaining above the aerobic level the entire time (it never drops to the 60-65% range).

Do I need to walk longer? Is it still worthwhile to do this sort of interval training even if I never really dip down into aerobic levels? Am I running or sprinting too hard?