spinning makes thighs bulky

The Claim: Want to lean out your legs? Steer clear of the spin room. Indoor cycling, or spinning, makes your thighs bulky.

The Fiction: Just like the age-old saying “No pain, no gain,” we cringe at the fact that this fit myth is still making the rounds. Indoor cycling is still topping the fitness trend charts and doesn’t seem to be going away any time soon. Blame it on the branded boutique studios popping up across the globe or the line of gear making its way into our wardrobe, but indoor cycling is still the It Girl at the fitness table. Main reason? It’s accessible. It’s a form of exercise that anyone can do, since indoor cycling is a low-impact activity that allows you to determine your own intensity level. That’s the pro. The con? We tend to get confused with what exactly “intensity” is – and how it affects our body. Sorry spin-o-phobes, but your claims of bulkiness are about to get debunked.

The Facts: First things first: what exactly is “bulk?” Basically, it’s adding a lot of muscle mass to your bod. Bulking up is something that needs to be trained for – you must have the goal of major muscle growth in mind. To get technical, bulking up requires very heavy strength training that engages what’s called fast twitch muscle fiber. Fast twitch muscle fiber is what allows you to have short bursts of significant force – think Olympic sprinters. Fast twitch fiber can grow in size with enough training, but you’ve got to have that specific goal in mind.

Proper indoor cycling, just like any other form of cardio (we know, we know, even though sometimes pushing that resistance feels more like anaerobic strength training than cardio!), uses your slow twitch muscle fibers, which are designed for long stretches of endurance that can accommodate short bursts of high intensity without completely fatiguing. Slow twitch muscles can’t increases in size like those fast twitch fibers can. If they did, your spin instructor’s legs would be so huge she would barely be able to hobble over to her bike (keep in mind your teacher probably instructs multiple classes a week in addition to fitting in her own workout – if she can spin that many times a week without “bulking,” your 2-4xs/week spin schedg is just fine)

So if your jeans are feeling tight after a spin sesh, does that mean you’re imagining things? Well, not quite. Spinning is not meant to be easy, and especially when your body is not used to it, your muscles can get temporarily inflammed as they try to figure out what the heck is going on and rush blood cells in to aid recovery. This slight inflammation can last for an hour or two, but will in fact go away. In addition – and this is a big one – if you are cycling for long, super-fast stretches (115-120 RPMs or higher, the pace of Kanye West’s “Stronger”), there is no way you are doing anything but taxing your joints and blowing off steam instead of calories. Sweating buckets after your last super-fast cycle sesh? Sweat doesn’t indicate how hard you’re working, as we’ve already discussed here. If you find your clothes fitting significantly tighter after starting up your cycle routine, you might want to take a peek at your post-spin diet and see if you’re overcompensating for the intensity at which you actually were working.

The Verdict: Just like any new activity, your body can take some time getting used to indoor cycling – and your muscles might get a little inflammed right after a good sweat. Be sure to gauge your intensity on how hard you are working, not how fast you are going. It’s not what it looks like that counts, it’s what it feels like. Verdict? The claim that indoor cycling makes your legs bulky is definitely a fit myth that needs to take a hike…or rather, ride.

From our friends


  1. Hi Katie,

    Thanks for the info – I’m a keen indoor cyclist and I did have a few reservations about gaining too much muscle mass but this has really nipped that fallcy in the bud!

    Besma (www.curiouslyconscious.com)

    Besma | 02.26.2015 | Reply
    • I am so glad to hear that, Besma! It’s such a fun (yet challenging-in-all-the-right-ways!) form of exercise, we’d hate for someone to miss out on its benefits based on a rumor-mill myth. Happy cycling! xo

      Katie Horwitch | 02.26.2015 | Reply
  2. I was a long time runner & wanted to try spinning to switch things up. I did 45 min classes 3-5 days a week for 7 months. Results? I have not lost any weight. I am bigger. My shorts do not fit. My boot iris bigger. My hips are wider. My thighs are bigger. I am 5’2 so I do not want all of that. I’m going back to running. Everyone has different body types. This is how my body responded. Try it, if you don’t get the results you want…. Try something else. Experience is the best education. Once you experience something you will know if it’s right for you.

    April | 05.17.2016 | Reply
  3. *autocorrect wanted me to say boot iris- what I meant to say- My booty is bigger. ✌️

    April | 05.17.2016 | Reply
  4. My two cents: It depends on your body type. If you are an ectomorph you’ll be fine. If you are endomorph or mesomorph, you will bulk up your quads for sure from heavy resistance or hills. I was a spinner (for speed training and cold season training) and long-distance (100k +up) road cyclist for 5 years. . I quit cycling as sport because my quads really bulked up in the most unattractive way despite the techniques to use the hamstrings, etc. (I am an endomorph) I switched to long-distance running and my legs are now lean and cut – Running gives you that lean, cut look for your legs. Indoor cycling melts away your butt fat and waistline way faster than running, however..
    I do avoid these classes at all cost, unless it’s speed/sprint focus class with very little hills. I still do road cycling casually as it is fun!

    carjeaux | 11.20.2016 | Reply
  5. Spinning equals bigger thighs..period. Look around class fools. Big thighs and ass.

    Mike Squirtintits | 12.06.2016 | Reply
  6. I used to teach spin classes for years. I also taught Pilates HIIT classes and did some running. When I stopped teaching the spinning classes and replaced those hours with running/ walking , I noticed my thighs got smaller. Yay!!!! I’m a mesomorph with a bit of Endo if I’m not careful with diet. However, I know some women who spin a lot and are stick thin so I agree, definitely depends on your body type. No one can say absolutely that
    ” spin makes thighs bigger” or
    “Spin doesn’t make thughs bigger”
    It depends on your genetics, type of class,
    And other factors. More resistance , as stated above , will build bulk in those easy gainers like myself.

    Surfdancer | 11.26.2017 | Reply

    TALIA | 01.31.2018 | Reply
  8. I have been actively spinning for about a year now 3-5 times a week for 60 minutes (20 miles) consistently. I have lost about 20 lbs…however, I have not slimmed down in my legs nearly as much as I would like. I actually think this has helped bulk up my quad muscles more than I like. I gain leg muscle really easily and I sort of wish I had checked out loght resistance running instead. I know I can’t spot tone, and I still have about 15 more lbs to lose…but my friend who started a running program about a year ago has really slimmed down her legs and has lost about 15 lbs also. She does distance running, and I think hard on her results vs mine, along with our similar
    body types, the spinning has definitely been a barrier to slimming down my legs. Everyone is different, this is just what I noticed about myself. Also, I would do some workout classes that used squats here and there, but I was never doing so many squats that it would explain the bulking up of my legs. I do think the cycling, while it was great for the weight loss, just made me a smaller pear shaped version of my larger self. My friend on the other hand has basically transformed her larger thighs into slim stems! It’s pretty amazing actually. We both follow similar diets too..FYI I am 5’3 currently 140lbs, and curvy but proportionate (pear shape: fat concentratedpremon hips and thighs, overall proportionate though). Hope this helps!

    Sherri | 07.13.2018 | Reply
  9. I used to lead a spin class, and I’m a guy.
    Back in my 20s, when I was still a competitive cross country mountain bike racer. I will say it depends on ALOT of factors weather or not you bulk up your legs spinning or cycling in general. But, based on my experience with my own body – and observing my students back in the day – If you push tall gears (or on a spin bike increase the tension) at a slower cadence (resistance exercise) the answer is YES the muscles you use to drive the bike are going to bulk up some.
    THIS IS A GOOD THING. Muscular,defined,legs on a woman are a treat to behold.
    Genetics plays a part, but because I have a tendency to push tall gears, I have pretty over developed leg muscles ie: if I wear a waist size that fits me properly… I usually won’t fit in the legs… in relaxed fit pants. I need a waist about 2” -4” larger for my legs and butt to fit into the pants. And “skinny jeans?!” No way… can’t even get them up over my calves. I don’t do any legwork in the gym. Every day is skip leg day for me. I get my leg work on the bike.
    Of course, I may be a freak. And I really wish my upper body responded as well to resistance training…
    but If you “mash” tough gears you’ll build some muscle.
    If you “spin” lighter gears at a faster cadence you won’t
    I say: do both and maximize whatever potential your body has to get defined, and get strong. Who cares if you can’t fit in whatever pants are the new thing? You are a hot monster that can destroy all who oppose you on a bike, and can crush lesser beings with your thighs like a grape! That’s better than having fashion model legs anyway.
    Besides, skirts don’t care if you have tree trunks for legs… and women with powerful legs look GREAT in a skirt.

    Quadzilla | 05.14.2019 | Reply
  10. I have noticed over the years when i sorry spun for cardio I bulk up in my lower body . Running skimming

    Mickakene bersansku | 08.01.2019 | Reply
  11. Hey So I ride a couple times a week and am trying to get back into biking on alternate days as it has helped me in the past. I know that a slow steady state ride helps with slimming down legs with no resistance added. Is there any advice you would give so I can see results getting back into this

    Valerie | 11.21.2020 | Reply
  12. Spinning made my thighs bigger… without a doubt. Not a myth. Body type plays a big role. I am stronger, but my jeans are tighter (around my legs). I’m, also, not eating anymore than I normally do. For me, exclusively spinning, is not a great idea.

    Erin | 04.12.2021 | Reply

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