The most basic workout is Steady State that is keeping stroke rate between about 18 strokes a minute and maybe the high end will be 24 strokes a minute and just going continuously. A workout like that can be anywhere from 10 minutes to 60 minutes or longer. You are just going at a nice comfortable easy pace that you are able to maintain, trying to hold the same spits or the same power output for the entire time working more on endurance.
When you do Interval Training maybe 1 or 2 minutes at a higher intensity then take a break for a minute or 3, then another a couple of minutes on, then another couple of minutes off. So you’re kind of an off/on type switch.
Higher intensity for short duration. For example an elite rower might do 6k all out, as hard as i can go, as fast as possible, or a 2km all out as fast he/she go. those are different types of rowing workouts.
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You can play around with the amount of times that you’re doing particular workouts. you might start off with 4 minutes, then go to 3 minutes, then 2 minutes, then 1 minute, then you work your way back up. 2 minutes, 3 minutes, 4 minutes. At each of those changes, you choose a different stroke rate. 4 minutes at 18, 3 minutes at 20, 2 minutes at 22, 1 minute at 24, and the same thing in reverse 22, 20,18, There are so many of workouts you can choose. you can start makeup your own once you get comfortable.