There's a storm brewing on the mountain bike horizon, and it's electrically charged.

The Bomber by Stealth Electric Bikes has 4500 watts - or six horsepower - of peak power

Imagine climbing your favorite single track trail all alone deep in the wilderness; heart beat pounding in your ears, legs churning out a steady, powerful cadence and sweat rolling down your face in buckets. As you approach the final rocky, root-filled ascent that demands every last thread of energy, someone from behind casually calls out in a conversational tone, "excuse me", and effortlessly zips up the brutal section of trail on a 50-pound big-hit downhill mountain bike while snacking on an energy bar.

It might sound completely absurd, but this exact scenario may soon start playing out on trails worldwide thanks to the increasing use of electric mountain bikes. And a lot of hard advocacy work could be for naught.

Watch the Stealth Electric Bikes Bomber in action:httpv://

After decades of being lumped together with dirt bikes as motorized vehicles, mountain bikes finally emerged from shadow of dirt bikes, gaining expanded trail access thanks to the tireless efforts of the International Mountain Bicycling Association (IMBA), local clubs and trail access advocates worldwide. A terrific example of this progress was the recent announcement by the National Park Service, dramatically expanding mountain bike access in more than 40 properties nationwide; something that was completely forbidden until only a few years ago.

IMBA president Mike Van Abel talking with NPS Director Jonathan Jarvis - Photo courtesy of IMBA

But after a 25-year struggle to gain a voice with land managers and policy makers in Washington, D.C. for trail access rights, the growing popularity of electric bicycles could put mountain bikers back in the same precarious situation they've worked so hard to emerge from.

"We recognize the benefits of e-bikes, yet also recognize that this type bike creates many added challenges for land managers and for IMBA's approach to mitigating the impacts of bicycling in natural environments," wrote Mike Van Abel, president of IMBA, on his blog. IMBA has also formally said they do not believe electric mountain bikes should be treated the same as human-powered mountain bikes, and have published a Motorized/Non-motorized Position Statement.

"We vetted our draft position through many other mountain bike advocacy leaders and groups from throughout the world," added Van Abel. "Most agreed, as did IMBA's board, that mountain biking should remain a non-motorized activity. Therefore, we conclude that riding e-bikes on natural-surface trails is not mountain biking. Further, we state that e-bike regulation for off-road travel should fall under motorized land management policies and rules."

The Outlaw SS by Prodeco has peak power of 1200 watts and a 28 mph top speed

Simply looking at the advertisements for some of these powerful electric mountain bikes is cause for concern. Take the Outlaw SS by Prodeco Technologies. The Prodeco website says the Outlaw is "the first muscle e-bike", encouraging you to "dispose of your motorcycle and climb aboard an Outlaw SS today", adding that the Outlaw is "created to break the rules." And break the rules it does. With a 28 mph top speed and 1200-watt peak power, the Outlaw SS exceeds current Federal e-bike regulations of 20 mph top speed and 750-watt peak power.

The HPC XC-3 has a 4500 watt output good for 52 mph

Far more subtle in its advertising but far more obscene its power output, the HPC XC-3 by Hi-Power Cycles puts out a whopping 4,500 watts of peak power, equivalent to six horsepower. And of course, because the 52mph top speed HPC XC-3 exceeds Federal limitations for e-bikes, the Hi-Power Cycles website advertises "THESE BIKES ARE MADE FOR OFFROAD USE ONLY!" as if there are no rules to abide by when asphalt is taken out of the picture.

The Hi-Power Cycles 10,000W, 55 MPH, HPC Tornado Electric Offroad Mountain Bike in action:httpv://

Since there is no simple way to distinguish between a bike that is within Federal limitations and a bike that puts down more horsepower than a go-kart, selective enforcement of e-bikes on trails becomes a futile endeavor.

Powerful bikes like the Outlaw SS and the HPC XC-3 on narrow, sensitive single track trails that see heavy pedestrian and bicycle use is a disaster waiting to happen for park rangers and land managers like David Hekel, senior ranger at the San Dieguito River Park in North County San Diego.

Senior Ranger David Hekel of the San Dieguito River Park "on patrol"

As a die-hard mountain biker, Hekel works every day to preserve natural habitat while improving trail access for mountain bikes and all users in his park that stretches 55 miles from the coast in Del Mar all the way to Volcan Mountain, a 5,000-foot high peak above the Anza Borrego desert. In the last five years alone, trail usage at the river park has nearly tripled. Every weekend hundreds of hikers, mountain bikers and equestrians use the trails that Hekel patrols and maintains. To Hekel, e-bikes on his trails is a new concept that hasn't become an issue yet.

"We have a strict no motor vehicle policy, so if an e-bike falls within Federal speed and power limitations, at least as of right now anyone can use an e-bike on our trails," said Hekel. "If we begin to see user conflicts or see e-bikes that blatantly exceed speed limitations, then we will probably ban them all together. We can't stand at the trailhead and inspect everyone's e-bike."

From the perspective of a mountain biker and park ranger, Hekel isn't sold on electric mountain bikes sharing trails with human-powered mountain bikes.

"Personally, I wouldn't want to see them on the trail," he said. "Even though they're electric, they still make noise and they have the potential to go faster than what some people can handle, especially on crowded multi-use trails. Sure, e-bikes can enable less physically fit riders to explore more miles than what they could normally do, but what happens in a situation when the bike breaks down? Will they call us to help rescue them, and if so, who ends up paying for our time and resources? I wouldn't want to see that scenario happening on our trails."

Will Schellenger, co-owner of El Camino Bike Shop sells Pedego e-bikes

Proponents of electric mountain bikes maintain that they are not a threat to trail access and enable elderly, less athletic and disabled people to visit the same places people on traditional mountain bikes get to enjoy. But there are bike shop owners selling both e-bikes and traditional bikes who are divided on how they feel about the topic. Will Schellenger, co-owner of El Camino Bike Shop in Encinitas, California, is an avid mountain biker who also sells road e-bikes.

"We just started selling Pedego a few months ago and people are really happy with them," said Schellenger. "I think they're great. We're getting people out there on bikes who otherwise wouldn't be riding, which is always a good thing."

But Schellenger isn't as enthusiastic about electric mountain bikes.

"As a mountain biker, I'm really concerned. In no way do I want to limit a person's ability to ride, but I also don't want to see trails getting closed down," said Schellenger. "Just the other day my friend was on a popular single track trail and saw someone on a big hit bike absolutely flying uphill. Turns out it was an electric mountain bike. I don't think that's right. But it got me thinking, maybe all this training I've been doing is a waste. I could just strap one of those motors on and bag myself some Strava glory."

Clearly we are still in the formative stages of trail access rules regarding electric mountain bikes. As the popularity of e-bikes continues to grow, inevitably we all will see more electric mountain bikes on trails, forcing land managers to address the issue. Can we trust that users will ride electric mountain bikes in a socially responsible manner that won't put mountain bikes back in the same motorized vehicle generalization it spend decades clawing itself out of? Time will tell.