Why are the first workouts of C25K are much harder than those in C10K?

Question

Inspired by Nathan Wheeler's If I can run, so can you!, I started the C25K program today. Things went well, but I realized one thing: the first workouts of the C25K program consist of much more running than the first workouts of the C10K. In his post, Nathan shows a screenshot of the very first workout of the C10K program:

5-minute warmup, then run 30 seconds and walk 4:30 seven times.

The first workout of the C25K goes like this:

5-minute warmup, then alternate 60 seconds of running with 90 seconds of walking for 20 minutes (8 times).

That's 4.5 more minutes of running, in half the time (40 vs 20 minutes)! Why is that, considering the fact that the goal running time/distance is double in C10K than in C25K?

Answer 1

The authors of the popular C25K program have written the "Bridge to 10k" program which is intended for people who have successfully completed C25K and starts with "Run 10 min/walk 1 min Repeat x 4" and there is a program "Ease into 10K" by the same authors which starts with "Run 3 min/walk 1 min Repeat x 5". The latter program is intended for somebody who already has some level of fitness and now really wants to get into running.

Programs called C10K are probably from different authors. A quick search on the net resulted in several different programs called C10K all with different run/walk ratios.