I have an exercise regimen for muscle building which works fairly well. However, my cardio is not exactly the best and I'd like to burn as many calories as possible with my time alotted.

I have a FitDesk which I use at my desk. At low speeds, I can bike for around an hour while maintaining focus on my work. At higher speeds, I can bike for around 20 minutes while maintaining focus, though it's more difficult.

I know that the ultimate solution would be to bike in a situation at which I don't need to focus on my work, but this is what I have to work with.

Is it better for general fitness and cardio workouts to have higher intensity workouts for shorter amounts of time or lower intensity workouts for longer amounts of time?

  • 1
    I really think your question is good, but that placed in the context of that fitdesk thing it looses its interest. You won't be able to reach anything worth being named 'intense' while working, therefore physiologically speaking although you'll feel a little difference there won't be much if we're talking about profund impacts between 2 different cardio programs.
    – Sebas
    Commented Apr 18, 2013 at 19:32
  • 1
    Is your goal of cardio for cardios sake or with fat loss in mind? Commented Apr 18, 2013 at 21:07
  • Both would be awesome, but fat loss would come first. Commented Apr 18, 2013 at 21:15
  • 1
    Why not just reduce your calorie intake instead of increasing the calorie consumption? High intensity cardio workouts require more rest therefore might interfere more with your body building program. Commented Apr 23, 2013 at 5:26
  • See this answer: fitness.stackexchange.com/questions/3291/…
    – JohnP
    Commented May 29, 2013 at 21:06

2 Answers 2


When I hear cardio - I assume that you are getting your heart beat up to at least 70% max for 20 mins. With around 30 mins being a good time. I actually told my clients 30-40 mins because I know they would normally pick the lesser.

I can cover this for 5 different possibilites-

  1. You want to do cardio because you want your endurance to be better or to have a healthy heart. Then it would be better to start slow for long periods 30-40 mins a few times a week. And work up to a more moderate pace for the same time.

  2. You want to do cardio to lose weight. XXX Nope. Cardio will only aid in short-term weight loss. It actually can (will) have an overall negative affect on weight loss in the long-term. If you are doing a lot of cardio you will hinder the growth of muscles and break down muscle fiber. That will slow your metabolism. You will be able to eat less calories a day. I have worked with marathoners - they are skinny and generally have little muscle tone. You can do cardio in short spurts (a month or two) without a lot of negative effects but then you must adjust your calorie intake after. Also from years of experience my clients have told me that when they start hard cardio training they are really hungry so they eat more.

  3. Your goal is to become big (bodybuilding or at least bodybuilding on small scale). Then I would suggest doing a speed walk 3-4 times a week at a half hour or a light jog (8 min mile or slower). This would work your heart and have little affect on your weight routine. It would also bring blood to your muscles and help with lactic acid build up. This would be the norm for most body building plans.

  4. Your goal is to become toned (boxer/basketball player physique). Then I would suggest shorter, more intense runs twice a week (15-25 mins) and two longer low pace runs (30-40 mins). When you are running fast, you are striding. Your long stride stretches your legs and abs and puts a lot of stress on your core. You will strengthen your core muscles and tone that region more with high intensity runs. Based on fitness levels I have suggested anything from interval training (200 meters at 80% then walk 200 meters and so on) for beginners, to a routine of sprints, to routines of "fast" miles (3 miles in 17-20 mins). Also running at high intensity does promote muscle growth in core and legs.

  5. You just want a cardio/weight routine balance. Then I suggest that when you start a routine that you spend 80% of your intensity and at least 40-50% of your time lifting and work in the cardio after at less intensity. When you are looking at overall balance you do not want to start high intensity cardio - think of the big guy hitting the gym twice a week drenched in sweat from a hard hour on the stair stepper. This thinking is for the misinformed. They are cycling between working out hard and eating. They are making little to no progress because their body is so deprived and shocked after a workout that they overcompensate by eating more.

  • "If you are doing a lot of cardio you will hinder the growth of muscles and break down muscle fiber." Can you back this claim with credible sources? Just because Marathoners, who don't do strength training, are skinny, does not mean that everyone who runs marathons will get skinny.
    – Baarn
    Commented Jul 29, 2013 at 6:40
  • Every time you workout you are breaking down muscle fiber - whether it be cardio or weights or sports or whatever. If the workout wasn't designed to build muscle you are going to lose muscle or hinder muscle growth. Do you really need a source for this? I am completely aware of how stackexchange works - and your comments to me seem that you want this to be a google copy/paste site. I have trained athletes for 20 years. If you DISAGREE with me then simply state your sources that oppose what I have said.
    – DMoore
    Commented Jul 29, 2013 at 16:27
  • On the marathoner point, what you commented on "does not mean that everyone who runs marathons will get skinny" is the exact point I was making. Some marathoners and almost all "great" marathoners are extremely skinny because of calorie deficit and the continuous break down of muscle - also their bodies eventually form to the most efficient type for that sport. I was pointing out that running (marathons) would only be a short-term weight-loss plan and that in the long-term could have a negative impact due to your change in metabolism.
    – DMoore
    Commented Jul 29, 2013 at 16:29
  • All the answers to Why does cardio/aerobic exercise lead to muscle loss? seem to disagree with you.
    – Baarn
    Commented Jul 29, 2013 at 19:21
  • Let's use the show the Biggest Loser as an extreme case. nih.gov/news/health/oct2012/niddk-15.htm Through diet and exercise they lose 35% of their weight through lean muscle. They have huge drops in metabolism. Done in moderation cardio will not cause muscle loss but it will definitely hinder muscle growth. Also these are people hopelessly out of shape. Cardio should be building muscle on them but when losing weight you are not able to replenish your body and it consumes muscle - see my point #2.
    – DMoore
    Commented Jul 29, 2013 at 21:20

If fat loss is your goal, then longer cardio lengths with lower heartrate are the best way to go, think marathon runners - endurance is key. However, as with any fat loss goal, you will lose some muscle along the way. If preserving muscle is relatively important to you, then try High Intensity Interval Training for your cardio: think sprints, run walk combinations, in your case maybe go all out for 20-30 seconds on the bike, then a slow pedal for about 10 seconds, and repeat.

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