This is great if you want a subjective measure of how fast weights are moving for you during a workout. Once you have enough total sets (I think 3 or so different sets and different weights for each lift), it should give you an estimated 1 rep max. That's great as a starting point (especially if you have a good idea of what your true 1 rep max is), but I think it falls a little short in the long run. I say that because the estimated 1 rep max appears to only be an average to date, or over set periods like a month, 3 months, or a year, that the app offers. So, for example, it wouldn't give you an estimated 1 rep max for that exact training day. That may be a bit much to ask, but that's what I was really hoping for, so I could back into my approx RPE 8 weight that makes sense for that day (or better yet, have the app tell me the recommended weight based on the desired RPE and how the weight is moving in my warm-up sets).
You can still use the app and the velocity measurements to help you manage the stress based on how the weight is moving, but it requires you to do more manual calcs or logging. And even that works best if you often do the exact same warm-up wights for each lift. So if the app shows my career best velocity is 0.6 meters per second on my last warmup set at 225, and I'm moving it at 0.5 meters per second today, I should probably take some weight off the bar from my planned sets that day. I think why that falls short is it lists your career best in the app. I go through periods where I'm near that range, but life happens, you detrain, and you're nowhere near your max. So you end up having to take a lot of notes on your average speeds "lately" at certain weights, or go digging through the app, and it takes too much time for me.
That's a very long-winded way of saying I think the app could use some work. The unit itself is great though, and it's a fun way to compete with friends in sandbox mode.
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