Another Good Tempo Run

Whew! Just got done with another good tempo run. Something must be wrong if I'm having so many good runs without a downer in between. So today (see details here), I again did a 10 minute (~1 mile) warm-up, followed by 2.25 miles at 8:45ish pace, 2 minute walk break, 1 more mile at 8:45, and a 10 minute cool-down. This was even more fantastic than last week. Pretty much the same workout/route, but this time my HR didn't go above 176 (I aim for 167-175 for the majority of a tempo run).

Greg asked me why I care about what my HR is. Well, there's a couple reasons. The first, more obvious reason, is that if I run the same route at the same pace twice, once with an average HR of 160 and once with an average HR of 150, my fitness/rest/preparedness has improved dramatically between the runs. If it was a very short time between runs, it might be caused by cooler temperatures, being more hydrated, or being more rested. But if it decreases consistently, you can tell your fitness is improving.

Since today was a tempo run, I will explain why I want my HR in the 167-175 range. Keep in mind, I'm no physician, so not everything may be accurate, but I have read much on the subject, and this is what I've taken away.

A tempo run is designed to be run at your anaerobic threshold; that is, just before the point where your body has to switch from aerobic activity (oxygen is delivered to the muscles via the bloodstream) to anaerobic (using a different process to produce energy without oxygen; produces lactic acid [technically lactate] as a byproduct and is far less efficient). Once you're in anaerobic territory, lactic acid starts to accumulate in the bloodstream. Exercising at the anaerobic threshold means you're at the point where lactate levels are constant; if you exceed this threshold, lactate begins to accumulate. Generally speaking, this threshold is obtained in running by having your HR at between 88% and 92% of your maximum HR. I don't know exactly what my max HR is, but I'm estimating it to be around 190, so this pace for me would have a HR of 167-175.

So, a tempo run is designed to stress your aerobic system to its maximum, without going overboard and switching to anaerobic activity. This also lessens recovery time as you do not deplete the muscle stores as heavily as if you surpassed the anaerobic threshold.

The end result is that this improves endurance, and makes it possible to run faster at a similar effort over time. While now I run about a 10:15-10:45 pace (on flat ground) to keep my HR in the low effort range of 135-150, I hope by the time my half marathon rolls around to be able to run about 9:30-9:45 at the same effort.

I hope this made sense!