Hello! I am a new user of intervals.icu and I’m a huge number/data nerd, so this platform is absolutely amazing for me.
Unfortunately I do not possess a power meter at the moment, so most of my training is based solely on HR. Today I did 500m hill repeats, each taking about 1 minute and 30-40 seconds. Because of the lag in HR, those efforts are seeming very low, compared to what I would expect. It’s coming out to a total load of 95. It was a 1 hour and 26 minute ride, with the decents as break and the rest of the workout spent around high Z2. Is there any way to somewhat calculate this using RPE or something else? Or am I just kinda stuck with what I have here, until I can afford a power meter?
Any tips are very welcome! Thanks!
@MadsGuldberg welcome to intervals.icu ! Yea, it’s really fantastic, and the forums are great. Someone will be able to help you get it dialed in / customized just perfect for you. That’s the beauty of it! 
When you say “…to somewhat calculate this…” , what do you mean? What is it you’re trying to calculate ?
The load is for reference purposes. As long as the basis for the load is consistent you’ll be fine. For me, I have a power meter on my trainer but can only use heart rate outside. That’s not best, but the HR and power load numbers are close enough for my purposes. The power meter does allow me to hit my HIIT numbers, but it’s the time the heart rate itself is hitting and inside those zones that gives the vo2max benefits, not the power. So, there’s that.
The load number and its graphs are for you to manage your weekly efforts so that you can plan and avoid over or under training. So, for example, if you find a weekly load of 500 is wearing you out, you can dial that back. In the end it doesn’t matter what the number is except in relation to itself over time. Simply a way to knowledgeably manage the stress of your efforts.
Thank you @CHRISTOPHER_INNS !
What I mean is properly calculate the load of my training. So, as it stands when doing intervals that are not very long, like those 1.5m hill repeats, the output effort in terms of watts is way above my FTP for sure. However, the Avg HR for each interval is quite a bit below my LTHR, so the load that Intervals.icu is calculating will be quite a bit lower than reality, I imagine? Does that make sense? 
Thank you for the detailed reply @Jcmiii ! Isn’t load also used to calculate fatigue, and by that then also calculate fitness gains? I like using this to see if I am actually making progress over the long term, but if the load calculation isn’t accurate, then the rest won’t be accurate as well, no?
@MadsGuldberg ahhh, gotcha. Yea, read you loud and clear.
Yes, and that does make sense. BC of the lag in HR, your power output is way above, but your HR never gets too hot, bc of how short the ints are…
I certainly don’t mean to come at you sideways; meant in a helpful way, but do you think it may help your training / simple power improvement if you did ints that were long enough to get your HR up into Thresh or VO2, for 30s - 4 mins ?
If this is what you can currently do, it’s awesome that you’re doing it, and you shouldn’t feel pressure to do more. But if you would be comfortable trying 30s - 4 mins in Threshold or VO2, that may both help you improve more, and also solve your issue w metrics… it would then make HR totally reliable, repeatable, and usable metric for you ?
@Chris1982 Hmmm… these were around 1.5m intervals, and I wouldn’t say my heart rate didn’t get up there, it certainly ended close to max, but it also started in low Z1 on each interval. So it probably drifted from 140 to 192-194-ish (max is 196). But that also “only” gives me an average in the high 170s to low 180s for each “lap”, which is just around LTHR for me
I’ve done it with 5 min intervals before and those looked way more accurate on intervals.icu, as in each block actually showed Z5-Z6, where as these only show as high Z4, even though the power output was likely Z6+ 
Ahhhh!! Gotcha!!
Hey man, I might have exactly what you want, actually! For real.
I made a chart that shows I think exactly what you’re looking for. It’s prev. day’s time in HR zones, colour coded and stacked, so just by looking at it, gives me a snapshot of “how hard that day was”, vs the prev. weeks, etc. Take a look, pic below. Chart is public, so you can just search and add it w one button click, see if you like it, delete if not! Someone smarter than me could probably make it come up w a number, and somehow track this…TBH, that number probably already exists in the sys somewhere!! 
Chart for searching is called HR TiZ PREV D, STACKED
I’m mostly looking at the size of the red bar: Like the 3rd from last bar was def a lot tougher ride than the last bar, even though they are same total, red zone is almost double. And 2nd to last ride was a monster. Needed an extra reco day after that beast.
EDIT TO ADD: For tracking fitness gains over time:
Two ideas:
1 - You could add numbers; total TiZ in Z7 and 6, and if over time, you’re able to pull more seconds in those zones, you’re definitely getting fitter.
2 - You could have one fixed “test route” / ride that will be your benchmark. Instead of smashing it as hard as you can, do it in exactly the same fixed time, every time, once every 2 - 4 wks, and if your TiZ in Z7 and 6 is decreasing to do the same work, you’re def getting fitter. [This would be best on a low-speed, hillier route, like your climb repeater, where variation in wind speed is a minimal factor for your efforts].
The Load and Fitness numbers don’t reflect Fitness gains. The term Fitness is a misnomer when taken literally. Fitness is actually the adjusted 42 day average of Load. The Fatigue is the excess over that average derived from current activity. (7 days? Or something?)
I wouldn’t get too concerned about not having power numbers. Nor, about the Fatigue line for that matter. If the fatigue line you see correlates to your actual fatigue that’s great, but you don’t need it. Whatever the Form and Fitness numbers are that match your limits, those are the numbers you want to keep in mind. You can use those to plan your week so that your overall efforts relative to past efforts are within your capabilities and goals. If you want to increase your efforts from one week to the next to see your Fitness average rise, use the Form you received for your past efforts to guide you in how much to increase those.
Long before power meters, athletes were training to top form. Our modern technology gives lots of data, but it can’t drive training. hmmm
And yes, RPE is a great way to manage your short term efforts in those situations where your heart rate can’t catch up. You are building strength doing HIITs the way you are. But, vo2max HIITs are a different animal and designed to keep the heart rate up.