How long have you been training? During my first 16-wk plan, my mile time over 60 minutes was cut almost in half. But it took a few weeks to see gains, and months to see it really drop.

A comment on technique changes:

In my experience, it’s normal for HR to increase when you change your technique. My guess is that this happens because we’re not efficient when first trying new movement patterns. Our brains likely over-recruit the muscle required which would increase the load, and therefore increase HR.

It’s tempting to think that–after reading about the “best” way to do something–that we can just plug it in and see benefits. I think it’s more realistic to expect that those benefits will only come when a new movement pattern is old. With older movement patterns, our brains know exactly what’s required, and it’ll let go of what’s not, making the movement pattern less stressful overall.

As an example, I changed my running form from being a heel striker to landing midfoot. It took two years for it to fully feel normal. Now, funnily enough, if I try to heel strike, it feels horrible and foreign, even though that used to be my normal movement pattern. Now that I land midfoot, I have far fewer joint issues than I used to, but it took a long time to change the pattern.