Brrrt...fartlek to and from Komazawa Park

I have to catch up on posts for two runs. This is by far the more interesting of the two:

Saturday morning I woke up at five and couldn't sleep so got up and headed out for my run at 6:00 (after checking email of course). I wanted to do a speed workout of some sort, but it is 4 km to run to the park, and then 4 km back, so that's quite a few km that are not well-suited to intervals or tempo running. So I decided to do a fartlek (Finnish for "speed play") whereby I would make up the speed bits as I went along.

The first 2 km I just ran easy to warm up, then said, OK, run hard to Kannana Dori. That turned out to be a bit over 600 m (measured by footpod). Then I ran easy for a while and knew I could fit in one more hard bit before the park. Started at a foot bridge and ran until I hit a red light: only 300 m. It was then only a couple of hundred meters to the park whereupon I immediately started another hard bit (fart; brrrrt!) for the 1 km pull up the hill (only about 2% gradient I suppose). The next hard bit was 500 m down hill (3%?) in which I concentrated on shortening my stride and getting faster leg speed. Kind of fun. That brought me back to the park entrance point, so I did one more lap of approximately the same, except the fart (brrt) was only 800 m uphill and then 600 m downhill). Then on the way home I managed two approximately 1 km brrts with the last kilometer easy.

All up, just under 12.5 km with around 6 km of it being in speed sections of well under 4:00/km. A few of the reps were quite a blast, like the 500 and 600 m downhill sections at 3:21/km pace! surprisingly I finished feeling fairly fresh. A very nice run. It was a cool morning and I think the same run with a bit more heat and humidity could be a bit tough. Here are the data in excruciating detail:

Section	Effort	Distance (m)	Pace	Hrmax	Hravg
Warm-up	easy	1,904	0:05:19	76%	70%
Corner-Kannana	fart	625	0:03:55	87%	80%
Float	easy	712	0:05:32	87%	74%
Footbridge-corner	fart	308	0:03:44	84%	80%
To park float	easy	192	0:05:59	87%	80%
1100 to 2100 (uphill)	fart	1,000	0:03:40	91%	84%
2100 to start	easy	58	0:05:47	89%	88%
start to 500 m	easy	490	0:05:41	85%	72%
500 m to 1000 m (downhill)	fart	490	0:03:20	92%	83%
1000 to 1300	easy	317	0:06:12	92%	80%
1300 to 2100 (uphill)	fart	808	0:03:42	90%	85%
2100 to 400 float	easy	442	0:06:36	92%	74%
400 to 1000 (downhill)	fart	606	0:03:21	91%	84%
Leaving the park	easy	385	0:05:51	91%	73%
To Kannana	fart	952	0:03:51	90%	83%
Kannana-corner	easy	663	0:05:32	90%	75%
corner-Post Office	fart	1,010	0:03:37	89%	85%
Post Office-home	easy	981	0:05:48	89%	72%