Hi Luca

I envy you for this pace and HR. ;-) This said, and knowing age and HRmax, I think your values are pretty correct then. But as you know after a few years of training: we are no machines - one day the values are correct, on others they aren't. 
I'm not sure how precise the "new" performance checker works, but there are a few more triggers that change the settings if you don't want to relay on it. Especially races of second and highest priority trigger a new planning. And after all: you can easily adjust them by overruling the settings, if you feel the plan is too hard. If you lower to lets say 5:45, that might be a big difference. 

BTW: your max HR might be a bit higher. In a 10 km race you might reach 90% or more percent I you race against your sporting archrival... But when you reach 100% you stopp. When I tested on a threadmill in a lab, it was harder than any 10 or 5 km race... in the end I could not run on for even 5 seconds, was a the brink of fading away...  

Hansruedi

 

Hi Luca

First question - as usual: are your settings correct? Your pace is pretty fast for a longrun. Longruns are runs, where you can talk with your buddy in normal sentences. No gasping. If you can run 5:26 easily while chatting - that's good, would be a Marathon of approx. 3:30.

Longruns are usully at arround 70 - 75% of your max.Heartrate. So: bpm 135-145 means, that your max.heartrate should be set correctly to more or less 185 bpm. If I write correctly, I mean "mesured", not estimated or calculated from your age. So the first thing is to know your max.heartrate AND your possible speed. A 10.5 km - all-out run is what you need. And the last 500 m uphill until you cant anymore. Then you set these 10 km at #3 in your settings and your bpmmax at #9. (of course, 5.5 km might do as well...)

Now your settings should be OK. But be aware: there still is the possibility, that your heartrate does not fit the avarage RC-values. My friend has a considerably lower bdm at the same pace.  

Of course the values are just a frame: depending on very different factors, your bpm might be a bit higher or lower, your pace depending on ground, weather, hills etc. might differ. But if you run at 5:26 and you can't talk anymore, then your pace is to high - ore your heartbeat is.

For beginners I would focus an the bpm. In the quick runs (MT / INT) you could try the given pace and neglect bpm. After a few training sessions (of after a test-run, a competition etc.) RC would adjust your values. But most runners tend to run to fast. 
My Longruns I usually try to run as long as RC tells me to, at a heartrate that is in the beginning lower and later often higher than the given values but usually within the range. The distance might be correct or not. I usually just use it to know, which of my routes I am going to take. (18 km is around the lake, 12 km to the airport etc.). When I read 18 km and 2 hours I start to the lake, try after a few minutes to reach the indicated pace. If my bpm is to high, I slow down a little or accelerate and then try to keep my pace.

Hope, this helps?
Hansruedi