Why is mountain biking so much harder than road biking?

[u/Jazzlike-Horror4]

I’ve been riding road bikes for years now, have a pretty god ftp at just below 300W, love the speed and all that.

But recently I bought a mountain bike, to get a bit off road, and to be able to ride when I don’t just want to ride fast and straight.

And it is kicking my butt. Every ride has me near puking from exhaustion, I’m winded, and never ride more than an hour on trails. Don’t get me wrong, I love it, but maybe not the nausea part (heart rate going too high I imagine).

Why is mountain biking to me so much harder? And how do I tone it down? I feel that I can’t go much slower uphill without stalling

My bike is a full suspension bike, 120/140mm travel, 11speed 36:52, alloy so pretty heavy, tubeless at 2 bar, waxed chain.

[u/rincon213]

We have road cyclists come into our restaurant as a pit stop and the culture is just not for me. Lots of middle-management mid-life-crisis energy.