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martin b asked in SportsRunning · 3 months ago

Why do my legs feel heavy when i sprint?

I used to be really athletic, and fast (4.4 in 40-yd dash). But i cant seem to sprint more than 25-30 yards before my legs feel heavy and i actually trip over them. Never had this issue before. I can easily jog for a long period of time. The problem is when i sprint.

7 Answers

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  • Anonymous
    3 months ago

    Because your unfit. Try other hobbies  like cards  and watching TV its not cut out for you

  • 3 months ago

    Perhaps you should slow down the pace of your run, if you have a watch with GPS, you can calculate the pace on this calculator https://calcrun.net/pace-time/

  • Anonymous
    3 months ago

    I have the same issue at times. My doctor, my cardiologist have not been able to determine was causing it. I have skinny legs, and a slim upper body, so it's not weight or fat that's causing it for me. Good luck in finding out, hopefully it will help me as well.

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    Lv 7
    3 months ago

    You say you "used to be" really athletic, which implies you are not anymore. It's not odd that if you are much less fit than you used to be, that intense activity would be more difficult now than it once was. You can work on improving that by training to be "really athletic" again. 

  • 3 months ago

    Do you often experience this? Do you also have leg cramps or Charley horses? This is a common condition associated with athletes and people overexerting their muscles.

  • 3 months ago

    You didn't give us much information about your history. How much did you exercise in the time between when you were fast in the 40 yard dash, and now?

    I'll assume you had some sort of period where you were not sprinting. If that's the case, it's likely your leg muscles are no longer conditioned (trained) for sprinting. 

    The short answer is this:  It's likely because you are out of shape, with respect to sprinting.  

    If you want more information, here it is:

    Jogging is an aerobic exercise: It raises your heart rate and breathing rate, but the effort is kept below the "anaerobic threshold", also known as the  "lactate threshold." Sprinting, on the other hand, is above the anaerobic threshold. This means your muscles are demanding more energy than your cardio/vascular/pulmonary system can deliver for use by aerobic metabolic pathways. Your muscles try to make up the difference by metabolizing blood sugar via a pathway that doesn't require oxygen. 

    This "anaerobic glycolysis" pathway is less efficient. It produces metabolic waste faster than your system can remove the waste. The accumulation of this waste inhibits muscle action. If you sprint as far as  you can, your muscles will accumulate enough waste so you will be forced to stop. Your muscles' reaction to accumulation of metabolic waste is what makes your legs feel heavy. 

    If you include sprint training in your workouts, you will train your muscles and your system to tolerate a higher level of the metabolic waste at the same time you train your body to remove the waste in less time.

    But, don't overdo it. Avoid burnout.

    Comment: Lactic acid is generally regarded as the major metabolic waste when working above the anaerobic threshold. But, I read an article in which the author claimed that hasn't actually been scientifically verified. The author intended it as an example of science hastily coming to a conclusion when discovering a correlation. The author suggested the major metabolic waste is actually lactate, which is a base, and lactic acid is produced in order to help remove the lactate. 

  • 3 months ago

    because like me, u might be FAT? or skiny

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