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You guys probably know by now that I am an advocate of cardio, which is unlike most other trainers that focus mostly on heavy lifting (Nothing wrong with that! It’s just not for me).

I’m always asked a lot of questions about cardio, but more specifically, the best type of cardio to lean out your legs and avoid making them bigger and musclier. So thought I would answer all your questions here! If I haven’t answered your question, please feel free to ask below in a comment and I’ll add it to the blog post! xx

Do I need to walk on an empty stomach?

Not necessarily. Any walking is great and the more steps you can accumulate during the day, the better! But it is possible that you might burn a higher percentage of fat if you do your walking fasted (i.e. before breakfast).

Walking burns stored carbohydrates (stored in your muscles as glycogen) and fat. If you don’t have as much stored carbs, your body might burn more fat. Also, it will be more effective if you have eaten a low carb meal for dinner the night before.

It can be beneficial to do your walking on an empty stomach, but it’s not necessary. Walking any time of the day is good!cardio q&A

What speed should I walk and run?

These speeds should be used as a guide only. Speeds will also vary depending on your height (obviously taller people will be able to walk / run faster).

  • I would suggest aiming for a walking speed of 6-7km/hr or 3.7-4.3mph.
  • I would suggest aiming for a running speed of 10-12km/hr or 6.2-7.5mph.

What incline should I walk / run at?

I suggest zero. Walking and running is best done on a flat surface if you don’t want to bulk up your quads. Any uphill walking and running will use your quads more and can make your legs bulkier.

If you are on the treadmill, you can set your incline to 0.1% to replicate walking outside. But if you have trouble with shin splints (like me), I would keep it to 0%.

Is there a difference walking / running on the treadmill compared to outside?

No, they will both have the same results. It’s just more of a personal preference.

Sometimes I prefer doing my cardio on a treadmill because I can track my speed and see if I’m improving (especially for running). But it just feels good running outside!

And I also don’t mind walking on the treadmill because I can watch a TV show on my phone as I walk ;) Another great benefit of having access to a treadmill is that you can do your cardio regardless of the weather conditions.cardio Q&A

Is it better to run slow or fast?

A lot of women tell me that run slowly for 45 minutes and are confused as to why this isn’t better than walking for 45 minutes, or running faster for 20 minutes. I’ll try to explain.

When you are jogging slowly, the action of your legs means that it is the same as running. Running does build muscle. The action of walking actually really helps to get rid of fat on your legs, not running or jogging. So slow jogging for 45 minutes means you will build muscle, without really getting rid of the excess fat that walking will. So you’re probably better off better walking.

When you are running faster, your body is burning lots of calories and you’re pushing yourself so your fitness is increasing, which is great. But jogging slowly isn’t really that challenging, and you’ll burn less calories. It may even bulk up your legs because you are overdoing the running. You’re not getting the full benefits of running if you’re just slowly jogging.

I think it’s better and more effective to either run faster or just walk. That is my preference. Slow jogging is still better than nothing though so you can do it – it’s up to you. But I don’t think it’s as effective as the other two.

I feel like running bulks up my thighs. Is this possible?

Yes this is possible. Running does build muscle (but not as much as other forms of cardio or strength training). Usually only people who are shorter or are the endomorph body type (or both) have issues with building too much muscle with running. If running is a problem for you, I would avoid it.cardio q&A

HIIT cardio – should I do it?

I wrote another blog post on the best type of HIIT cardio to do to avoid bulking up your legs. As I mentioned, running builds muscle and HIIT running will build even more. If you’re interested in doing HIIT cardio, please have a read of this blog post!

Whether or not you do HIIT cardio depends on your body type and to a certain extent, your fitness level.

If you are short or an endomorph body type (or both), HIIT cardio may not be the best exercise for you. It will build some muscle and with a shorter frame, more muscle may not be your goal. It could make your legs look bigger. If you know that running makes your legs bigger, then I would avoid HIIT cardio.

I mention fitness level because HIIT cardio is hard, and you need to have a good base cardio fitness first to do this exercise effectively and get the benefits. Being able to run at a medium fast pace for at least 20 minutes would be a great start. After that, I think you would be fit enough to add in some HIIT cardio.

As I mentioned above, if you have any cardio related questions, please feel free to ask and I’ll add them to the blog post :) xx

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17 comments on “Cardio Q&A”

  • Farnaz says:

    So if we are endomorphs and do walking for cardio, what do we do for resistence traininng or muscle training?! Should we avoid it alltogether or is there any exercise that works on muscles for endomorphs but not make it bulky?

    • Rachael Attard says:

      Hi! No you don’t need to avoid it altogether, but just need to be careful with the type of workouts you do. I recommend lighter resistance training and the style of workouts on my blog and in my eBook :) xx

  • Victoria Frantchuk says:

    When I go walking I push my double stroller, does it couse me to build muscle on my legs cuz it definitely feels like a workout!

    • Rachael Attard says:

      Hi lovely, I don’t think this would build more muscle in your legs unless your stroller is REALLY heavy or you are walking on an uphill with the stroller xx

  • Emily says:

    Hi Rachael! Do you do all your workouts at home or at a gym? Also, so if I run relatively fast, 20 minutes before a resistance session is sufficient? I’ve been thinking at least 30 minutes, but if running faster is better for cardio, 20 should be good?

    Whats your exact workout weekly routine right now anyway? I’d love to know :)


    • Rachael Attard says:

      Hi lovely! I usually do them at home unless I have access to a gym. I just joined a gym for a month though so going there at the moment! I just started my eBook this week so that’s what I’m doing at the moment :) And yes I’d say 20 minutes is enough, but 30 is fine too! xx

  • Farnaz says:

    Hi. Do i have to sweat like crazy for my workout to be effective?
    I don’t sweat easily unless i run for 60 mins. When i walk on the treadmill, i don’t sweat much even when i walk for 60 mins. My speed is also not too slow based on my heigh. I’m 5.2 and on average i walk 3.5 mph. Sometime 4 but i can’t do 4 consistently for 60 mins.

  • Mack says:

    Hi! I have been running a lot recently (around 3-5 miles per day, and usually in the morning before eating). However, it still feels as though my legs are not slimming down as much as I would have thought. Is it possible that I have water retention due to increase in running after not for a bit of time or should I be doing something else? ( I am shorter and have had problems with bulking up muscle very easily)

    • Rachael Attard says:

      Hi Mack, it could be due to water retention… But running isn’t necessarily the best exercise for slimming legs. Walking is. Have a read of this blog post xx

  • Jackie Glassman says:

    Hi Rachael,

    I’m a long time runner and run long distances. It’s never been effective in slimming my legs and after reading your blog posts I’m understanding why! I’ve also take Body Pump classes (weighted bar, tons of squats) and Barre. Seems like all of these have added to my legs getting thicker. I will start power walking on treadmill b/c that seems like the best solution. This may be silly, but I’m curious HOW to power walk. I’ve never done it! Do i squeeze leg or butt muscles as I stride?

    Thank you!

    • Rachael Attard says:

      Hi lovely! There are never any silly questions :) You just walk normally, no need to try and squeeze certain muscles, just walk and enjoy! xx

  • Jackie says:

    Thank you for all this amazing advice. I’ve struggled with my legs gaining too much muscle from exercise for years. I’ve run distance — 1 marathon and many half marathons. But even with that, I still build muscle too quickly. After reading all of your posts, I’ve decided to take a break from my running to try the power walking. I started today — walked the suggested 10k on an empty stomach. My question is about pace. You make suggestions above, but those felt slow to me (probably b/c i’m a runner!). So I sped it up. My concern was if I walk faster, is that not as slimming? Should I stick to the suggested pace?

    • Rachael Attard says:

      Hi Jackie, wow good for you! 10km is a very decent walk. Walking faster is OK and if you’re a bit taller or have longer legs, you may be able to walk slightly faster. If you could maintain the same pace for 10km and weren’t out of breath, then I think this is fine :) xx

  • Kate says:

    If I’m doing brisk walking to slim legs, and i do it every day in once session, how long must I walk for?

    • Rachael Attard says:

      I would aim for 45-60 minutes xx

  • Andrea Marie says:

    Hi <33
    I have a mesomorphic body type, and therefore gain muscle easily. I've done track and field for 6 years (mostly sprinting), so my legs are pretty muscular. I usually run 2 times a week and power walk 4-5 times a week, in an attempt to slim down my legs. Because I've trained track for so many years, I need to run at least 13.5 km/h (for 4-5km or so) in order to challenge myself – but will it bulk up my body (particularly my legs) to run at this pace? is it too fast?

    Thank you for all your amazing blog posts – and thank you in advance <333

    • Rachael Attard says:

      Hi lovely, wow if you can run at that speed for that length of time, that’s amazing! This speed should not bulk you up so keep doing what you’re doing. Good luck! xx

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