All morning it rained cats and hound dogs.

Still, this trio of Vanderbilt biology researchers kept pedaling.

From west Nashville to east, up and down street after street, they plotted out guitar strings and bell bottoms and one rockin' hairdo.

They rode with one goal in mind: create an image of Elvis.

To draw him, they had to travel just more than 100 miles of Nashville streets with just two things — their bicycles and a GPS tracking device.

The Music City-themed bike route is part of a global trend some call GPS doodling, or "Strava art." Runners, cyclists, skateboarders and other athletes trek around towns, and even across countries, with GPS devices strapped to their wrists or handlebars to create pictures with their activity routes.

When they are done, they post them to networks like Strava, which is essentially social media for athletes. It's meant as a training tool, where people can compare their performances and friends and followers can like and comment on them.

What's just as cool about it is that each route forms a thin red line on a map. And that line can unclip an athlete's imagination.

Stephen Lund is one of the most prolific GPS artists out there. The cyclist from Victoria, British Columbia, has ridden thousands of miles and designed routes that look like a giant giraffe, a T-Rex, an anteater and a Ninja Turtle.

For him, what began as just exercise has become an exercise in creativity — and it's ignited a passion that has grown to become a world phenomenon. Even in Nashville.

On Saturday morning, a trio of Vanderbilt professors — Nick Adams, Dale Edgerton and Bryan Shepherd — cycled through Music City to create a bike route that looks like Elvis Presley playing the guitar.

Wearing gold glasses and fake sideburns, they rode.

It started with Honest Abe and a birthday surprise

It didn't start with Elvis, actually. In fact, it was someone much older — a forefather of our country — that was the original Strava art inspiration for the group.

At 4:14 a.m. on Presidents Day in February, Edgerton and Shepherd wanted to surprise Adams for his birthday. They set up an early morning ride, but they didn't tell him where they were going.

The three had become friends and cycling buddies, because they all commute to and from work by bike. One comes 11 miles to Vanderbilt from his home near the airport; the other two travel 11 to 17 miles from Williamson County.

In their day jobs, the biologists work to solve important global issues. Right now, Adams is focused on creating devices that can diagnose infectious diseases to improve health care in rural clinics and countries such as Africa and India.

But, Adams said, "I like being creative for the sake of being creative and not necessarily to solve a big problem." GPS doodling is the perfect hobby. It helps give rides a purpose, said Adams, who has never loved the idea of "cycling for no reason and grinding it out."

It is a way to make exercise fun, dissolving the delirium of riding the same roads and routes on each daily commute.

It was actually Shepherd's commute that became their first inspiration. When uploaded to Strava, it looked a little like the features of a face, he realized. So he started to use his bike like a red marker, expanding the image with Edgerton's help to create a doodle.

When it was complete, they took Adams on an unusual ride. Adams knew they were drawing something that overcast 33-degree February morning, "but I was so confused with all the rerouting," he said.

The 126-mile route stretched almost up to Hendersonville, through Mt. Juliet and down to Brentwood. And when they were done, it looked like a president. Abraham Lincoln, to be exact.

Adams knew almost immediately he wanted to make one of his own.

Elvis was kind of an accident

He didn't set out to make Elvis.

In fact, Adams didn't have any ideas in mind when he first sat down to create his Strava art. Without a plan, he downloaded Strava's heat map — which shows all the most-ridden streets and trails and pathways in the city — and began to sketch.

In North Nashville, he saw some roads that looked like the shape of a head, which seemed like the right way to start.

He couldn't figure out how to make a neck, but he found a collar.

Downtown, he saw potential for guitar strings, and, he thought, that seemed appropriate for Music City.

As he moved south on the map, he wanted to create legs, but every route was super wide. Then, he thought, "Oh, these could be bell bottoms."

It didn't take long to realize he had all the makings for the King of Rock 'n' Roll.

"I couldn’t have drawn Elvis if I was given a blank sheet of paper," Adams said with a laugh. "It's almost like a city map was supposed to reveal Elvis. I just had to find the right roads."

Cyclists' message: 'Don't be cruel'

Starting at 5 a.m. on a dreary Saturday, Adams hit play on Elvis Presley's greatest hits and the three men hit the road to make Music City cycling magic.

They wore Elvis socks on their feet and gold glasses with sideburns below their helmets.

"We've been fans since we were knee high to a hound dog," Edgerton joked.

Watch: The "relive" video to see how the route unfolded

One thing people always wonder is how Strava artists ride the routes without getting lost. Garmin and Strava have their own route-building software. When downloaded to a bike computer, it will tell a cyclist where to make every turn — just like in a car.

There is one major difference. When you are riding to make a shape, there are a lot of U-turns and doubling back.

So you have to ride carefully because, as Lund pointed out in his 2015 TEDxVictoria talk, "a GPS device doesn't come with an eraser."

It took 10 hours and 36 minutes, with 66,760 pedal strokes and two flat tires for Adams, Edgerton and Shepherd, but they made it.

It was a somewhat ridiculous venture, the biologists admit, but what better way for three avid cyclists to celebrate the culture of Music City and have some fun on a Saturday?

For them, it's about fitness and creative expression. Adams hopes this will show people how much fun riding can be.

But there's a greater message in it, too.

In what can sometimes be a battle for the roads between drivers and cyclists, the three men hope through projects like these people behind the wheel of a car will start to recognize riders as something other than a nuisance.

"We hope there's a connection between the cycling community and the average driver," Adams said. "A greater awareness of cyclists, making them more human to other people."

So, even if traffic has got you "All Shook Up," see the cyclists and "Don't Be Cruel."

Reach Jessica Bliss at jbliss@tennessean.com or 615-259-8253 and on Twitter @jlbliss, and please subscribe to support local journalism.

Fun facts about the Elvis ride

Total contiguous miles: 100.3 miles

Overall height of Elvis: 8.2 miles

Overall width of Elvis: 6.2 miles

Number of navigation cues from GPS mapping: 320

Number of left turns: 149

Number of right turns: 140

Number of U-turns: 40

Total time to complete: 10 hours, 36 minutes

Total riding time: 6 hours, 57 minutes

Estimated calories burned: 3,600

Number of pedal strokes: 66,760

Number of flat tires: 2