300s in pool

I am writing this not because it is anything interesting but I need to record my swim times somewhere. If I do not do it now and here it will never get done.

Can you believe that I was the only person in an 8-lane 50m outdoor pool today? And it was not even raining and the temperature was agreeable! I want to move to this little town. Aparently Hannover is German Florida (you know, where all granparents live), so you don't have to deal with senior citizens anywhere else.

Onto the swim. 400m w/up, 2x50 strides, 5x300 @ 6:30, pit stop break (took me around 6min, long walk from the pool), 5x300 @ 6:30, 300m c/d.
300s went like this:
5:54, 5:51, 5:49, 5:44, 5;49
5:51, 5:59, 6:01, 6:02, 6:04

I had to idea what the reasonable send-off for this could be so I randomly chose 6:30. It was probably little too much but it is ok. Next time I will decrease the send-off.
It felt pretty good, definitelly not all out. Nice and controlled and it felt like I could be going this pace the whole day. Of course, as you can see I could not in reality since I slowed down quite a lot after the 6th one, but I honestly do not understand why the last 4 were so slow. I felt good and was always surprised when I saw my time. I tried to go faster but I had only one gear and could not go faster. So here we go again, it is like when I started swimming last year, I was not able to push myself in pool. In the last 3 motnhs I have completely forgotten how it is done. The real swimmers probably do not understand this but I swear it is true. Just ask any non-swimmers.
For the first 5 I was able to pull nicely, strokes all the way to my thights. Then my arms (or back or whatever you are supposed to use when swimming) got too tired and I could not pull/push past my waist and I felt water slipping through in catch/pull phase and I could not do anything about although I tried. So that's probably why I slowed down by so much. I need to keep working on developing more durable swimmer's muscles because mine are too weak.
Wanted to do 4k but that would be a pure junk "metrage" so I stopped at 3.8k.  

A friend of mine is in Rio for work and she sent me an email saying that I would like Rio because...there are a lot of good looking men running along the Copacabana beach. Geez. Nice to know what people think about me:) But it is my fault because our conversations with her are mostly about training and hot guys. Or rather I talk and she rolls her eyes at me.