I have a Suunto Ambit2. Just showing a stopwatch in big numbers. Swim for *about* 2.5 minutes. If I get to the wall a few seconds early or later, It doesn't really matter in the big scheme of things. Then swim the main set until there's *about* 2.5 minutes left in the hour and then swim the rest of the hour as cool down.
I grew up on swim teams and was a sprint freestyler specialist, so I've done a bazillion intervals. Had an epiphany after learning to train to bike and run for triathlons that we could swim by time and effort instead of the crazy keeping up with lap counts. Like warm up 10 minutes, easy freestyle for 8, race pace for 4, recovery for 6, tempo for 20... Just like running or biking. Makes training WAY easier. You can even change from one thing to another mid-lap if you want. Just look at the clock on your wrist every few laps to get an idea of where you are.
My Ironman swim is just under 1 hour and cadence about 63. I want to get that IM time to 55, so I'm adding in the paddles to increase strength. Used to use them all the time when I was faster. Ankle strap is new to me, but I'm loving it. Got the idea from Clayton Fatell's interview here at about 1:05 in. -
https://www.youtube.com/watch?v=qjBX_W6YjRw
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Zen and the Art of Triathlon.
Strava Workout Log Interviews with Chris McCormack, Helle Frederikson, Angela Naeth, and many more.
http://www.zentriathlon.com