It's evident that cycling puts the leg muscles to work - but that doesn't necessarily mean you'll gain tree trunk pins from pedalling alone.
"It’s a leg dominant sport, so you can expect to see your legs gain definition, but training doesn't necessarily attribute itself to size in a huge magnitude. It depends on how you’re training," says Girling, who runs a coaching and nutrition company.
"Look at track cyclists, compared to road cyclists, the leg size is completely different. Top level Tour de France and WorldTour level cyclists are all very lean, typically have slimmer appendages, whereas track cyclists are stacked. That is obviously related to the kind of training that they do."
Track cyclists get their bulging muscles mostly from gym work, something some road riders still do, but usually favouring a focus on stability as opposed to lifting heavy weights for raw strength and power.
On the bike training plays a role, too: "Track cyclists will be doing hard efforts that will be sub one to four minutes, the energy system they're using and fibre type they require is one that is going to acquire more size. A bigger muscle can put out more power. But a more aerobic based muscle doesn't need power in the same sense, it needs more aerobic cells to be able to fuel the muscles for longer efforts."
If your goal is strength and power (and, yes, big legs) you'll need to hit the gym, and train like a sprinter. On the bike, things like hill sprints, where you find a hill and smash it up, or standing starts that involve sprinting from a slow speed, are great options for recruiting maximal muscle and adaptation.
If you seek a physique suited to endurance, you'll need to build up an aerobic base with plenty of long rides at relatively low intensity, to promote production of those aerobic cells and develop your cardiovascular fitness.
Regardless of your goal, a bit of gym work is a good idea for cyclists of any level.