4.91 miles in 40:01

connect.garmin.com/activity/110784383

i got up this morning and looked at hal's advanced half marathon training plan to see what i needed to do. today's workout: a 40-minute tempo run. i wondered, "tempo run? what's that?" hello, google! on the running times website, i found this definition:

"also known as an anaerobic threshold (AT) run or lactate-threshold run, the tempo run was popularized by jack daniels, ph.d., about a decade ago. here’s his definition, taken from daniels’ running formula (human kinetics): 'a tempo run is nothing more than 20 minutes of steady running at threshold pace.' (he goes on to say that 20 minutes is ideal, but may be varied to suit the needs of a particular course.) without getting too technical, threshold pace is the effort level just below which the body’s ability to clear lactate, a by-product of carbohydrate metabolism, can no longer keep up with lactate production. daniels states that this pace is, for most people, about 25 to 30 seconds per mile slower than current 5K race pace."

a little while later, the post said this of the pace: "a tempo run should be 'comfortably hard' - one that could be maintained for an hour in a race."

got it. run as hard as you comfortably can. no heaving breaths or puking. i can do that.

i strapped on my heartrate monitor strap, put my garmin on my wrist and headed out the door. i walked a short distance and then started running. i ran at what i judged to be a comfortably hard pace. i kept an eye on my heartrate, trying to keep it in the 160-170bpm range. looking back over that data, i did fairly well at that.
my kinvaras, a.k.a. the flash, performed beautifully. they protected my feet when i ran down a graveled alleyway. i'd wondered about that since my racing flats are awful on rock roads. i felt a rock or two, but no pain with the flash! sweet! i can use these on trail runs if i ever get near a trail.

i'm not sure if i did a perfect tempo run. you can look at my splits and decide that i guess. expert opinions are welcome.