LENGGRIES, GERMANY - Robert Werner and his wife Ursula usually make time to say a friendly hello to hikers as they ride their gently whirring e-bikes up trails in the Bavarian Alps.

But more often than not, their greetings are met with frowns.

"The first thing they look at when they see us are our bikes," says hotelier Robert, 46, of his electric-powered bicycle.

"If we have an engine, they respect us less."

While the Werners are convinced of the virtues of e-bikes which have pedals but also an electric motor that can assist the rider's pedal power, others are less enthusiastic about the new revolution in cycling.

On their e-bikes, the couple powers up the 800-metre ascent to the summit of Herzogstand mountain in half an hour -- without breaking a sweat.

Many purists believe exploits into nature should be powered by muesli bars, not the electricity grid, and regard the assisted cycling boom as another hi-tech intrusion into the great outdoors.

The presence of e-bikes on Alpine trails and mountain paths has become a subject of controversy.

Complaints by hikers have appeared in the German media often accusing e-bike enthusiasts of whizzing up and down the paths, posing a risk of collision, while others point to environmental concerns.

"Electric bicycles allow more people to access the paths," including those that previously saw little use, said Friedl Kroenauer, 59, of environmental group BUND Naturschutz.

"This causes soil erosion, for example."

For Kroenauer, who has a breathtaking view of Germany's highest peaks from his office, those who scale the region's mountains on e-bikes are cheating themselves.

"Getting to the top of a mountain is something you have to earn," he insisted. "You have to feel that you have worked your muscles, you have to be exhausted.

"Electric mountain bikes make this notion of effort disappear," added the hobby sportsman, a fan of walking and traditional cycling.

Despite similar criticisms from other outdoor purists, more and more people in Germany and elsewhere are using electric mountain bikes to reach summits.

In 2018, Germans bought nearly one million e-bikes, a quarter of them mountain bikes, according to a report by Germany's bicycle industry association, ZIV.

German bike manufacturers such as Haibike, Cube or Prophete, as well as motor and battery producer Bosch, have enjoyed the boom.

"The bicycle industry, and in particular the electric bicycle industry, is extremely important for Germany," said David Eisenberger, communications manager for the ZIV association.

"It creates thousands of jobs -- directly and indirectly, in tourism for example."

In Lenggries, a town of 9,000 residents, an hour's drive south of the city of Munich, the Werners opened a bicycle rental shop a few months ago next door to the hotel that they run -- offering, of course, e-bikes.

"The demand is huge and the customers very diverse," says Robert. "Everyone wants to try."

Lenggries now offers three charging stations for e-bike batteries.

In a bid to reduce conflict with hikers, some Bavarian municipalities are considering setting up areas reserved for cyclists -- both e-bikes and normal mountain bikes.

But Robert voices doubts: "How would that be regulated? It would be impossible."

"It's just a matter of sharing the mountain better by following a few rules for living together," he says, suggesting that hikers always be given priority over cyclists.

A similar debate emerged decades ago when conventional mountain bikes first appeared in the Alps, he recalls, adding, with a shrug: "Today no one complains anymore." -AFP