On a warm and uncomfortably humid afternoon in Washington DC's sprawling Rock Creek Park, 53-year old Dutchman and former World Bank executive Gregory Maassen is swiftly biking up an exceptionally sharp incline - barely breaking a sweat as he pedals.
"The hills are pretty steep here," he says. "Despite the fact that I like to bicycle - as most Dutch people do - it was not practical. That's how I got into e-biking. I got one in 2019 and the rest is history."
Mr Maassen, the founder of a 250-person strong E-bike Lovers club in the US capital, is one of hundreds of thousands who have turned to electric bicycles for fun or to get around their cities and towns.
Put simply, an e-bike is any bicycle that uses an integrated electric motor to assist in propulsion. While some come equipped with a throttle and can be used like a moped, they can all be pedalled - a distinction that legally separates them from electric motorcycles.
In the US, the industry, rather than the government, broadly puts e-bikes into one of three categories.
Class 1 e-bikes are equipped with a motor that provides assistance only when pedalling, with the assistance stopping when the bike reaches 20mph (32km/h) while Class 2 e-bikes come equipped with a throttle that can be used to propel the e-bike to that same speed.
Class 3 bikes come equipped with a motor that provides assistance only when the rider is pedalling, stopping when the e-bike reaches 28mph (45km/h).