Wednesday - recovery?

Run type: lower aerobic
Distance 18.35
Average pace: 4:40/km
Heart rate: 140
Weather: 19 degrees & cloudy (5:30 am)

I intended to just go out and run an easy pace, kind of like a recovery, in anticipation of doing cruise intervals tomorrow. So not pushing at all in the first 3 to 4 km and my heart rate was having trouble getting above 130. Once in the park I decided to at least get it up to 135. This was soon yielding 4:20/km on the downhills and 4:30/km or better on the uphills. That's probably a bit faster than genuine recovery pace, but it was by no means a hard run. It was fast enough to leave my legs, especially quads and hammies, feeling a little tired. I'm sure there is some cumulative fatigue involved. Makes me wonder it is OK to do a hard session tomorrow, but I guess I will have to suck it and see.