A quick Google search of 'does cycling make your thighs bigger?' confirms what we already knew - there are a lot of women who want to cycle but are worried they're going to take on Hulk-esque qualities.
The short answer to the question is 'no'. Cycling, alongside a healthy diet, will result in a lean physique for most people.
If Robert Forstemann's quads popped up as soon as your average Joe jumped on a bike and rode around the block, we'd all be World Sprint Champions and riding at the Olympics. So if you're worried about developing tree-trunk legs, here are some things you need to know...
Massive quads aren't just the result of bike riding
You think the guys and gals on the velodrome just ride their bikes all day? Track cyclists (and indeed many riders who specialise in shorter distances, where top end power presides over power to weight ratio) spend a lot of time in the gym.
Aerobic exercise, such as cycling, works your endurance muscle fibres - these become more resistant to fatigue with training, but don't bulk up. You'd need to lift heavy weights on a regular basis to get a reaction from the muscles responsible for power.
It takes A LOT of refuelling to build muscle
Athletes trying to bulk up need a lot of calories, and we're not just talking "I totally had a three-egg omelette".
If you're looking to build lean muscle, just try to consume enough calories to replace what you're burning, and if you want to lose weight, consume a little less to create a calorie deficit. To build powerful muscle, you need to consume lots of high-quality protein.
Women build muscle differently to men
Women have much lower levels of testosterone than men (around 15% less), and higher levels of body fat (around 10% more). The body fat is necessary for a healthy menstrual cycle and it's just the way we are.
Testosterone aids the creation of bulging muscles, and it's the reason sedentary men naturally have more muscle than sedentary women. If a woman takes to strength training or resistance exercise, she'll gain muscle, but not as much as a man.
Body type plays a huge role
The way your body will change when you exercise depends a lot on your body type. There are three loose categories:
Endomorphs find it hard to lose body fat and are less likely to build muscle mass. Short, hard interval bike rides will help them shed extra fat if they want to, though evolutionarily speaking, the fat stores would have helped them when food was short.
Mesomorphs are the people likely to develop muscle. These are the kind of people that might become sprinters or track riders since their body is naturally predisposed to being good at producing power. If this is your body type, don't "fear" the muscle, embrace it and use it to your advantage on the bike.
Endomorphs are tall and lean, they will gain muscle mass with strength training, but at a much slower rate. These people are usually good climbers and benefit on endurance rides as they have less body weight to carry over undulations.
Muscle is leaner than fat
Sorry if the image is a bit gross - but it makes a good point: muscle weighs a lot more than fat. If you lost 5lb of fat and gained 5lb of muscle, you'd weight the same - but would look leaner:
So yes, cycling will change the shape of your legs, but unless you're doing a LOT of squats, and maintaining the same levels of fat (by eating A LOT), you're not likely to get "bigger".
Muscle burns more calories
Gaining muscle will make it harder to store fat, since muscle burns more calories, even when you're not doing anything. When you're at rest, ten pounds of muscle burns 50 calories a day, whilst the same weight in fat burns just 20. So effectively extra muscle will act like a furnace for calories, so you're not likely to be gaining more fat if you're packing on the muscle.
Your body is more than what you see in the mirror
So - we've explained that you're not likely to turn into the incredible hulk without an awful lot of effort. But what if you're putting that effort in? Well, muscly women look totally amazing!
Even if a hard-earned muscle didn't look amazing, we'd still reckon the feeling of achieving something new, pushing a boundary, getting to the top of that long lusted over the climb, or simply just enjoying time on your bike, matters more.
Happy riders are a lot more attractive than anyone stuck indoors, dreaming of skinny legs and cucumber. So go ride your bike!