I'm 77 years old and recently completed C25k for the third time, after recovering first from chemotherapy and then from a strained/torn Achilles tendon, but having been doing Parkruns during the fitter intervals in between. I knew from experience that the C25k program would get me there, so I extended my running times during the later weeks until I managed to cover 5km on W9R2. The only problem was that this took almost 44 minutes!
For the next 2 weeks I kept doing repeats of my W9 (not always managing 5km non-stop) but my 5km times did not improve, and I started to believe that getting to do 10km was beyond me. However, I became aware that I was landing on my heels, and as I got tired I was more and more more likely to find my leading foot sliding onto the ground. I knew a little about the Japanese slow jogging concept, which emphasises the need to land on the ball of the foot, so I changed my training to intervals of slow jogging interspersed with short intervals of brisk walking (which were necessary because my calf muscles were noticing the difference!)
To my amazement, the first time I did this yielded a better 5km time (including the time spent walking) than all of my non-stop runs. Not only that, but my times have subsequently improved steadily (but only to just over 40 minutes! - so far) and I feel much less exhausted than I had done on C25k. Clearly, I had been running very inefficiently before. I have often seen people of a similar age to me running (gamely) in a very flat-footed way, and I had obviously been doing the same.
I have yet to get anywhere close to running 5km landing on the balls of my feet, but I'm going to give it a try. Meantime I thought I would share this for the benefit of any other (probably senior) runners who feel their performance has plateau'd. Does anyone out there have any personal experience like this? Or any related comments, suggestions or advice?