Riding a bike on trails is how I want to spend my fitness and recreational time. I don't like road cycling it's too boring. An arguably even better fitness tool than road cycling is the turbo trainer - but it's ULTRA boring. Riding an MTB (or eMTB) on trails is how I want fitness to happen for me. It just is so, I've learnt this with a lot of experimentation (and wasted cash on both road and stationary bikes).
I'm a bit too unfit or too heavy to ride an analog bike on hilly trails as my sole form of exercise while still making much progress with my fitness (or weightloss). My average heart rate is too high to get decent fitness gains - there simply needs to be a lot more easier efforts in the schedule to get those gains. This is because the recovery is too much after such full on high heart rate efforts, and because hard efforts like these do not build aerobic fitness - they are anaerobic. It just becomes all damage repair so not enough adaptation, and not enough aerobic stimulus. I know this from experience because I've done it for literally years. There were times in those years I did steady state intervals on a trainer and I immediately got some actual improvements. Or I started road cycling (longer, slower rides) and immediately started to make some more progress. But these things are just too boring to sustain long term.
More recently I struggled with pretty bad headaches and I went to the doc thinking I needed scans because I must have a tumor or something. Long story short, it was exertion headaches from sustaining a high heart rate too much. He told me to stop doing that, I'm not in my 20s anymore, and condition myself instead.
The eMTB is a good answer (the only answer) for me to still be riding exclusively on those hilly trails I enjoy and do it while sustaining a lower heart rate. Since I've been doing that with fitness in mind (not just going hard) I have most definitely and obviously gained aerobic fitness because I spend many more hours a week pedaling, and lots of it at ~145 bpm. This is probably still above the perfect long-slow aerobic base training zone for me, but it's still very aerobic, and I'm not interested in the huge amount of time required to make any lower do much for me. So it's spot on. That is going to make decent improvements in aerobic fitness versus what I was doing before - it's a no-brainer. I can feel it. I can recover from it and ride every day. Riding every day!? Unheard of before (when I did that, it was punishing). Now I'm taking it in my stride.
Is there a loss in strength vs analog MTB? Absolutely. Just like single speed vs XC bike, right? More pressure on the pedals means more strength. It will take some time to dial that back later, most definitely. I could do squats - I have a rack in my garage - and it is my intention to bring in a little strength work once I've adapted to this suddenly-much-higher cardio load. But right now I'm exclusively on an eMtb and it really doesn't matter. Weight loss and aerobic improvements are the current goal for me. I'm focused on time out pedaling, my diet and sleeping well. I'd also add I spend a LOT more time descending, and that means a lot more time working the bike in the attack position. This has definitely brought improvements in lower back strength - because it doesn't really ache now, where it did before when I started eMtbing after being exclusively on an analog bike.
I fully intend to bring an analog MTB back into the mix next year when I can afford an amazing one, and when I've lost a good amount more weight. I've been dropping weight very effectively just riding eMtb lots and not eating garbage. When I do get that analog MTB again - my intention is to mix it up. Do some hard rides on the analog, do some lighter rides on the eMtb, but importantly - keep the frequency up. Maybe over time I can start to veer into more and more analog rides. We'll see. That kind of fitness - to ride all the time on an analog and for recovery to simply not be an issue - is the goal for me. I dream of long MTB holidays in NZ with that kind of fitness. I'm going to try to get there. Maybe I won't, I don't know. The eMtb will be there to help. But I know for sure I need to lose the weight and up the aerobic engine before it's even a possibility.
The eMtb is a completely valid training tool, when understood and used in the context of well rounded training. It allows for lighter efforts ON TRAIL and it's the ONLY way to do that (for those of us who aren't the right combination of lightweight & fit). Lighter efforts are a necessity for real pedaling fitness gains (though certainly not the full story). Yes, you can go road bike or turbo trainer and get the same or better results - but I'd much rather be riding on my local trails in the forest.
If i'm riding with reasonably unfit or slower people then i'll try to run with the motor off as much as possible as i want to encourage them to keep going out and improving.
