When I want to go for a Z1/Z2 ride is normalised power a good metric to try and stick to or is there something else I should be looking at for a more accurate metric?
NP is a retrospective metric. You review the ride and time spent in zone dictates the NP. So a 1hr Z1 ride with 8x15sec in Z7 will have a very different NP to average.
So whilst riding/training it is not really a useful metric.
3sec / 5sec / 10sec power or average may be better.
Hopefully a steady Z1/2 ride, all of the power metrics would be very similar. As JulesC wrote, 3/5/10 sec would be fine. Afterwards, compare NP and average power to see how variable your ride was.
Agreed with the above. Using NP may be more useful if you’re doing outdoor intervals and want to compare lap average power to lap NP, if you’re looking to see if you’re able to maintain relatively “smooth” output at your interval target. For easy riding, I’d just use the average.
I would definitely not use NP for a Z1 ride. Example - If you ride 5 minutes and pedal for :15 and then coast for 4:45 your NP is going to be useless from what your intended goal is for the ride.
3s Average is what I stick to.
I’m not convinced that 8 brief sprints would really have much of an effect on NP.
…but it will give a significantly different result to average power.
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I use NP for my 70.3 races where I want the effort to stay as smooth as possible and where there are very few stops or hard accelerations.
When I’m targeting an outdoor Z1/Z2 ride I only look at 3sec power as all of the stops and coasting will drag down AP and NP.
Just to put some data to it since I was curious.
Here’s a 1h ride at 70% (207W for me) with 8x15s @ 200% (590W)
It brought the NP up to 235W and the Avg to 220W. So a pretty good increase in both. But I would argue that 8x15s sprints is a relatively intense workout. 3-4 sprints is probably more realistic
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I recently did a 90-minute zone2 ride with 6 short sprints, each about 6-10 seconds. Pulling out the 60 minute work interval, and doing a rough analysis to remove the sprints, that took VI from 1.04 to 1.12. So depending on your definition of much, it means that for a lower z2 (using round numbers) at say 150W with 900-1000W sprints that would bump NP from 156 to 168.
If you had my Z2 power and MVDP’s sprint power, it definitely would 
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Thanks, that’s a bit more than I expected. Still, I wouldn’t call 7% “very different” (as @JulesC did).
Yeah, I think alot of it has to do with how high the power is on your sprints. For example, if those sprints are at 250% vs 200% then the NP jumps to 255. For some people 15s at 200% is a sprint while for others it’s just a surge and they might hit 250-300% which would really inflate that NP.
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NP wouldn’t really be representative/come into play for at least 20 minutes so it’ll be kind of awkward. I would use a rolling average or just AP.
I wouldn’t call holding 250% to 300% of FTP for 15 seconds a sprint, it is more like a surge. At ~400%, my 15s MMP is crap and considered by WKO, “recreational” (I need to work on my VO2, the whole region is crap).
It depends when in your program and why you are doing the ride. Some would say it’ll be better to anchor to HR for these type of rides.
The other factor is that the OP said Z1/Z2 ride so whilst the calculation that MWGlow15 did was at 70% FTP the calculation was based was therefore ALL in Z2, with absolutely no time in Z1; which clarifying was part of the OP’s information given.
So in these workouts I used midway through each zone and split the total w/o to 10 min in Z1 10 min in Z2 (midway through each zone) with 8x15sec at only 1% above the Z7 Threshold so there is more head room and in reality if you can hit Z7 you are not that close to 1% and most people are clear through the threshold especially for only 15 seconds (20 seconds is the typical time Z7 is able to be held) but I wouldn’t want to be accused of over egging the pudding.
If these were put into MWGlow15’s NP calculator app it would be greater than 7% as the lower zone is significantly lower than the one s/he used. And this is consistent with my answer to the OPs request.
EDIT realised it was an Intervals.ICU facility
I think this is based on an under reading PM FTP but the difference between NP and ave is clear.
Normalised power is ok over a sufficiently long duration (seen suggestions of 20 mins +). One strategy is to build a workout where you have 20 min laps. Then over the the full ride you might complete 6 -15 laps. You can have normalised power for the lap on display. This way you are not trying to hold power precisely at any point in time but keep it in a given range over a longer interval. It is a strategy I have used. First 10 mins just easy, then into the laps, using the first one as a guide, and then trying to match that consistently throughout the ride. Clearly common sense needs to be used if a lap contains a substantial or steep climb.