Usually when I run intervals on the treadmill I warm up for a few minutes and then set the machine to my desired speed and begin training. Between intervals I stop completely jumping off to the sides to rest while the machine is still running and then after my desired rest period I jump back on.

The other week while I was doing this, someone in the gym came over to tell me that what I was doing is very dangerous, because making sudden stop while your heart rate is up is unhealthy. Now I understand that what he is saying is mostly true as I know that at the end of a cardio workout, cooling down is advisable in order to bring the heart rate down slowly.

Why doesn't the same rule apply to football players? They only run for a few seconds at a time at full intensity bringing their heart rates very high only to come to a sudden stop at the end of the play. That was my logic when I was stopping suddenly for a few seconds to catch my breath in preparation for my next sprint. Is what I'm doing really dangerous or is it ok for me to continue running intervals in this manner?

  • How long is your rest period between each sprint? I'd worry more about falling when jumping back on a treadmill that's still running.
    – user240
    May 17, 2012 at 3:55
  • Falling when jumping back is easy to avoid. What you do is jump back while still holding on then after about 2 seconds when you got the pace you let go and run it out. As for my rest period it varys, but the last time I ran intervals was when I had this encounter with that guy in the gym, and I was running for 30 seconds and resting for 45 seconds. May 17, 2012 at 5:18
  • 1
    Kind of sounds like a tabata workout. I do this on a stationary bike: 20 seconds sprint, 10 seconds rest. repeat May 17, 2012 at 15:42
  • 10 seconds rest meaning a full stop? May 17, 2012 at 17:54
  • Safety of falling off aside, this sounds like a typical sprinters workout. When you run 200m repeats, they take abotu 30 seconds, and you get 30-45 seconds rest. Additionally, when you finish each 200 meters your goal is to stop as soon as possible (without jamming the breaks on to your knees). Given the fact that in your case the ground is moving, not you, coming to a full stop is rather equivalent, and it's not a big deal.
    – VISQL
    May 21, 2012 at 21:13

6 Answers 6

  • HIIT (High Intensity Interval Training) as you describe is a very acceptable, if not a prefered method of training. According to the Tabata study:

    .. adequate high-intensity intermittent training may improve both anaerobic and aerobic energy supplying systems significantly, probably through imposing intensive stimuli on both systems.

    Can HIIT be dangerous? Yes, it is a more advanced exercise technique in that it is not for the beginner who is in poor shape. Nor is it for someone with heart problems without proper supervision.

    Can intervals be safe? Yes, provided that you exercise within your tolerance. HIIT requires that you exercise intensely for short intervals followed by short rest intervals as you described. You must rest during the rest periods so that you can muster the ability to hit another intense interval.

    The rest period can be active or passive. In an active rest period you would continue a low intensity exercise like walking. In a passive rest period you would just try to recuperate and reduce your heart rate. (Personally, an active rest interval works best for me.)

    I don't have access to the original Tabata study, but in the abstract it simply mentions "rest" periods without specifying whether it was active or passive. If you have any concerns, just walk during the rest period. Other studies show that active rests are superior to passive rest intervals in that they provide a better quality of work interval and produce lower lactate levels.

    The ideal for safety and effectiveness when doing interval training is to wear a heart rate monitor and exercise into your target range during your exercise interval (but avoid exceeding your maximum heart rate), and then reduce your heart rate to your target recovery range during your rest period.

  • Cool Down - As you stated, the reason that a cool down period is recommended after exercise is so that the fast beating heart and respiratory systems can gradually return to normal as you cool down. The gradual cool down keeps blood circulating, rather than pooling in the muscles. Cool down after HIIT just as you would any other exercise.

  • What would be an indicator that I can use myself to judge weather its ok for me to come to a full stop after a sprint? As of now I gauge by the fact that when I come to a full stop I don't get dizzy which I think I would if i was not fit enough to come to a full stop. I am not sure tho if that's a correct way to gauge? May 20, 2012 at 18:26
  • I don't know of a specific indicator other than monitoring your heart rate. I think most interval training regimes recommend some active form of recovery. I edited my answer to provide a reference to other studies reporting that active rests are superior to passive rests. May 21, 2012 at 12:32

You can stop suddenly at any stage of your workout. No safety issues here. But why jump on and off a moving treadmill when you can easily stop the treadmill gradually.


Stopping suddenly also distrupts the flow of blood to the brain and working muscles. When you stop suddenly the blood pools in the joints and dangerously interupts the flow of blod to the brain...where 70% of our blood flows. This cuold result in a stoke or hemmorage in the brain. THE ONLY tim etis is acceptable is "sports specific training". Like football etc. It does not help distance running enough to offset the dangers.

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    Do you have any data to support that? Every runner who stops quickly is at risk for a stroke or brain hemorrhage?
    – Eric
    Dec 2, 2014 at 15:12

Stopping suddenly CAN be very dangerous in a FEW cases. People who inherited Brugada's syndrome, which has no other symptoms (but should show up on an electrocardiogram), can drop dead in these circumstances.

  • Can you explain how this occurs? From reading, it appears that Brugada's occurs mostly at rest (Sleep) or following heavy meals. There is only one mention that "some people with this syndrome exhibit symptoms during hard exercise". I don't think a small portion of the population of a very rare condition being susceptible warrants such an alarmist response.
    – JohnP
    Feb 13, 2019 at 18:19

If you stop suddenly it will be dangerous for your body. Instead you should try walking around instead which will help your heart rate more than stopping suddenly.

Football players run for a few seconds to bring their heart rate way up and will come to a sudden stop? If you notice most of them will be walking around and not stopping at a spot.

  • Dangerous how? Can you provide some references to back up both of your statements?
    – user240
    May 17, 2012 at 2:38
  • have no reference. but have experience it. When i was young i was a long distance runner but do not watch up for all those. so now there is alot of problem with my heart, like uneven heart beat and low heart rate. Recently just started to run again but could not run as much as the past due to the limitation of my heart. Just want to share so that u all wont make the same mistake as i did.
    – Jie Liang
    May 17, 2012 at 2:42
  • That sounds more like a specific condition with your circulatory system, which I strongly recommend you consult with a doctor. I've never seen anyone or heard about anyone suffering in any serious way from stopping a run abruptly--unless other health factors played a role.
    – user240
    May 17, 2012 at 2:52
  • Ok have consulted a doctor. Anyway a sudden stop after a sprint will cause the heart unable to stop with it. As it is still pumping blood all over ur body quickly. A sudden stop will cause excess blood to go to ur brain which may cause some headache. It is told by some profesionnal trainer. So a slow walk will help to adjust ur blood circulation.
    – Jie Liang
    May 17, 2012 at 2:56
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    The question under debate here is whether it is dangerous to stop abruptly between sprints. All I'm asking is a reference to support your statement, as it would have a large impact on many people. Does it matter how fast you run, or for how long, or how old you are, or how much you weigh? If stopping abruptly is indeed proven to be dangerous for the average human being, then answers to those questions would be essential to know to take the necessary precautions. And what are the dangerous consequences of exceeding those conditions?
    – user240
    May 17, 2012 at 3:45

End your treadmill workout by gradually reducing your incline and pace until your heart rate returns to a calmer level.

Some treadmills are equipped with heart-rate and cool-down features that will notify you of your current heart-rate and gradually reduce your pace and incline until the treadmill stops completely.

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