A Kenyan Out-Back

Well, kind of. The Kenyans run 15K out and then return much faster, finishing at world class pace. I waddled "out" and "jogged" back. Translated, I ran 8K on the treadmill, and ran the 2nd 4K faster than I ran the 1st 4K. Specifically, I ran the first 4K in 22:50 and the second 4K in 20:22. My unique to treadmill running hip pain didn't flare up until I'd run 7.5K. My time and HR splits were kind of interesting (but only to me):

1st K 6:13 HR Ave = 132 (my tachychardia was evident for the first 3-4 minutes)
2nd K 5:42 101
3rd K 5:28 105
4th K 5:27 108

5th K 5:18 111
6th K 5:10 118
7th K 5:03 121
8th K 4:50 128

So, at my current running and rowing fitness, based on HR data (exertion), running at 5:10-5:15 per kilometer is equal to rowing at 4:00 per kilometer, give or take.