The insert is a massive change to the structure of the tire. The tire also has less room for deflection to absorb any rocks or roots which may cause losses of energy pushing you upward rather than forming better with the terrain and keeping you rolling forward. You're assuming the weight is the sole reason it might be draining your energy without taking into account the other variables.
Trails with lots of accelerations will always be more draining. If you add some stick on weights like I mentioned above and did back to back tests with a power meter and heart rate monitor I'd be very curious to see the results.
Translation:
I, "Fajita Dave", believe that a tire insert makes massive changes. I also believe it reduces the tire's susp travel and ability to deform around rocks and roots, resulting in suspension losses. You're not accounting these suspension losses with your focus on elastic hysteresis.
Stop-and-go style riding will always be less efficient, especially with additional mass. If you want to prove that you're so smart, please entertain me by taking on the burden of proving this, and go do this experiment with consumer-grade measurement tools.
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Sounds like a parroting of
Jan Heine's findings. I don't argue it. A tire that doesn't deform around a bump, and rides up it, is essentially riding up a tiny hill. It all adds up. Riding through sand feels as hard as it does cause there's a hill directly in front of the tire that you're virtually climbing. A fat tire reduces the size of that "hill" since it doesn't sink as much.
On the other hand, jeremy3220 is putting this into more hardcore MTB context. A FS mtb's suspension works properly at a higher speed to do the same for bigger bumps, preventing suspension losses. Tires that fold too easily hold the rider back from properly utilizing the more advanced susp that was specifically tasked for the job.
Regarding how weight fits into the context, you can argue that the weight merely acts like a flywheel and isn't inefficient. I'd argue that all that weight requires a lot more physical effort from the body to carry it up the hill, gaining a lot more potential energy per unit of elevation. A lot of energy is wasted going into the brake pads when you descend that elevation though. The extra aero drag you face on the descent also wastes it.
