After I realized my aquathon runs were hurting because of my lack of swimming, I got back into the pool this morning to crank out some yards.
I decided that I would measure my fitness by swimming 3 x 300s at a strong effort with lots of rest. Each 300 is to be just hard enough that you're spent at the end, but you maintain even splits for each swim. If the final one is much slower than the first (>5-7 secs.) you went out too hard. Lots of coaches use this to establish a base pace from which to set efforts/pace from for other sets. With consistent swimming and regular efforts, you should see improvements when you repeat this every month.
I hadn't tested myself like this in a wicked long time. After warming-up (which didn't go well, BTW) I was mentally set to be about 15 sec per 300 (or 5 sec per 100) slower than off peak pace. However, I finished the first one only 10 sec off my peak. I instantly knew the last one is going to be painful. Surprisingly I finished the second at the same pace and had hopeful thoughts for the third. But alas, after 75 of my first 100, I decided to break the swim up at the 100s and take 5 sec rest between each one. Just enough to catch my breath, but not enough to recover. The extra 5 seconds may not seem like much, but it makes a big difference. I was able to keep the same pace across all three 100s and again finish at the same total time for the 300 (taking out the extra 10 seconds of rest) as the other two.
It hurt, but I might not be as out of shape as initially thought. Usually, my swim fitness is the first to bounce back after a lay off (furlough?), so hopefully we'll see some improvement by the next aquathon. Also, I can't recall how I found this, but I'm going to use Swimplan.com to help provide some sets and get me out of my rut of the four or five that I regularly do. Seems like a spiffy, free(!) service.