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Why does running fast stress your body more than easy runs? (Read 345 times)

Philliefan33


    I ran without my iPod last night, and my mind really wanders without music.  I pondered this for a while:

     

    Why does “speed work” – whether it’s fartleks, tempo runs, intervals, whatever – put more stress on your legs/body than just regular easy running?  I think we can agree that the premise is true; if you haven’t felt it for yourself just recall how many times runners have posted on the forums about sore legs / injuries and have been advised to slow down, run easy, don’t try to do too much too soon.

     

    Five miles of walking feels easier than five miles at “easy” pace, which in turn is easier than five miles at “tempo” pace.  But in each case I’ve done the same amount of work – moved my 140 lb body over a distance of 5 miles.  The amount of time spent doing the work goes down as the intensity goes up.

     

    So what is different when you run faster?  Is it physics -- Does your stride lengthen, changing the range of motion of your legs and thus making little tears in your muscles?  Do you hit the ground harder, jarring your joints more?   Is it biochemistry – as in  lactic acid build-up?

     

    Theories?

    Future Races:

    5/4/14:  Bucks County Ten Miler


    Fat butt on couch

      You said it yourself -- the amount of work is done in less time.

       

      Your heart must pump more blood, your muscles must exert more force, per unit time.  Working harder = more stressful.

       

      And yes, you are also increasing force put to the ground so the forces exerted on bones/joints/tendons is going to be higher.  If they are liable to injury, it seems intuitive that risk will increase somewhat as forces increase.

      "If you want to be a bad a$s, then do what a bad a$s does.  There's your pep talk for today.  Go Run." -- Slo_Hand

       

        Physics.

        Runners run.

        xor


          biochemistry

           

            Science.

            "When a person trains once, nothing happens. When a person forces himself to do a thing a hundred or a thousand times, then he certainly has developed in more ways than physical. Is it raining? That doesn't matter. Am I tired? That doesn't matter, either. Then willpower will be no problem." 
            Emil Zatopek

              I think mainly because faster would tire legs/lung quicker. The tiredness affects the running form and the feet-ground impact absorption.

              5k - 20:56 (Sept 30, 2012)

              7k - 28:40 (Nov 18, 2012)

              10k trial - 43:08 (Mar 29, 2013), 42:05 (May 05, 2013)

              FM - 3:09:28 (May 19, 2013)

              spinach


                I don't totally agree with you here

                 

                Five miles of walking feels easier than five miles at “easy” pace, which in turn is easier than five miles at “tempo” pace. 

                 

                Five miles is a long walk to me and  is quite tiring.  However a five mile run is short and easy and gives me pep and energy afterwards.

                 

                I think running faster leads more to sore legs and injuries because of the increased force put on the legs that will stress the joints and tendons and muscles and whatever else is in there that gets sore.

                  Same as a car and gas mileage. Go 80MPH to your destination and you'll get there faster, but you'll use less fuel if you drive 55....even if it takes longer.

                   

                  So using that analogy I guess, there would be a "top gas mileage" speed (personal running speed) that would allow for the least at amount of strain on the body for a set distance.

                    I don't totally agree with you here

                     

                     

                    Five miles is a long walk to me and  is quite tiring.  However a five mile run is short and easy and gives me pep and energy afterwards.

                     

                    I think running faster leads more to sore legs and injuries because of the increased force put on the legs that will stress the joints and tendons and muscles and whatever else is in there that gets sore.

                     

                    I always find walking, and running really slow, to be more tiring than a jog or easy run. That's why when we on vacations and walk around all day, I'm more exhausted at the end of the day than if I had just did a normal run. Maybe though, it's because I'm not used to being on my feet for hours and hours.

                      Same as a car and gas mileage. Go 80MPH to your destination and you'll get there faster, but you'll use less fuel if you drive 55....even if it takes longer.

                      And relevant to the original question ... a race car has significantly more stress applied to its structural components as a result of race-speed operation, as compared to the plodding family wagon.

                       

                      There's work, and then there's power.

                      “Everything you need is already inside.” -- Bill Bowerman

                      mab411


                      Proboscis Colossus

                        Agreed with everything that's been said so far, but wouldn't fast-twitch muscle fibers vs. slow-twitch also have something to do with it?

                        "God guides us on our journey, but careful with those feet." - David Lee Roth, of all people

                          I remember in my college physics class when our professor (who happened to be a dad of a girl I was going out with!! ;o)) said that, in physics, moving an object from ground zero to a certain hight would all be the same; it's a matter of the altitude gain and the weight.  I argued him, by using an example of a near-by hill of about 400m in length and quite steep; "Don't tell me it's the same workload to run up that hill vs. run this other hill, same altitude gain but much more gradual and stretches out over 10-miles..."  I can't remember what his answer was but I do remember he didn't object to it.

                           

                          There are in fact number of reasons.  Number one and the one that you should understand most is physiological reason.  Whatever you do, your body requires oxygen.  And, depending on the intensity of the work, the demand of oxygen goes up.  Take checking your heart rate for example.  I've seen a thread about "how to take HR" somewhere--I didn't check it but just took a quick glance at it and saw some interesting question and answers...  I remember in my physiology class at college, we did a quick test of HR; we hooked a person with all the wires and what-not and have him sit, lay down, stand...and walk around.  All these "activities" affected the HR.  Standing is an activity.  Your muscles are constantly working to keep balance and that affects the amount of oxygen required, hence HR goes up however slight it may be.  In terms of running (speed), the faster you go, the more oxygen your body would require--in fact, a lot more.  It would be interesting to check out the oxygen requirement at various speed.  It's not linear at all.  One coach one time explained that the oxygen requirement would "doubles, squares and cubes..."  In other words, the faster you go, even the slight speed increase would call for a huge increase in oxygen requirement.  The more oxygen your body (muscles mainly) requires, the harder your heart would have to work to pump all those oxygen rich red blood cells.  Remember all the talk about Lance Armstrong and this thing called EPO or "blood transfusion"?  They try to get more red blood cells in the system (artificially unfortunately, of course).  This is to gain unfair advantage because, with extra red blood cells in the system, more oxygen can be delivered to the working muscles; hence, increased endurance.  All this is not so bad as long as your system is working WITHIN your body's ability to assimilate, transport and utilize in the working muscles; maybe just a wee bit harder (I'll get there a bit later).  But once it crosses that border line (your maximum ability to deliver oxygen)--some people call this Deflection Point--, then you'll get all sorts of new problems.  Now your body's ability to use oxygen had maxed out.  Now your body would have to work on a debt (called, appropriately, Oxygen Debt).  This will be paid back once you stop exercising in a form of "huffing and puffing".  During this process, your body is basically cheating by bypassing some process and this short-cutting process create lactate.  Without getting too deeply into this (cuz I'm not quite sure how it all work out either!!), this causes lowering of blood pH that upsets our metabolic actions and reactions.  Some people use the term "clogging up" but that's actually not quite accurate physiologically; but it actually sort of explains (visually) how it feels--you tighten up and muscles sabotage to work.  You jog around a track nice and easily and you feel like you can go on forever.  But if you try to run a lap as fast as you can go, then coming around the last turn, your legs don't come up at all.  That's what's happening in your body; your muscles are screaming "ENOUGH!!"  In other words, if you're working within your ability to use oxygen, you shouldn't be creating lactate and, theoretically, you can go forever (as long as your tank has the energy).

                           

                          This reminds me--I was going to comment on this a while back but things had been quite busy on this end and I sort of lost track...--; someone mentioned something about "When I started out, I can race a half mile no problem but no way I could have raced 5k...  Now I can race a half marathon..."  This whole view is all wrong.  It's as if to say, "Oh, David Rudisha had it easy; he only had to race 800m..."  When he ran 1:41 in London, he was probably even more beat than Rupp or Mo in 10000m (but then again, as superbly tuned athlete as he is, he may not have been...).  It always bugged me (not so much any more because I sort of accepted the fact that most majority of "runners" today just don't get it...); I love 5k and I train day in and day out so I can run 5k fast.  So I'd go to some local races and they have 5k, 10k and a half marathon.  People ask  me which one I'd run.  When I say 5k, majority would say, "Is that all?  C'mon, you can do better than that..."  And those are people who "plod along" a half in 2+ hours...  This also reminds me; I was going to chip in...  There was also another thread about how many half marathon we can do...  Well, it all depends.  I'm sorry but, if you're plodding along, you can probably do it every weekend without much damage...  I used to, and I'm sure a lot of guys here at RA still do, run 18-22 miles every weekend.  Would that count?  The point is; IT'S NOT DISTANCE THAT STOPS YOU, IT'S SPEED.  You start to flirt around with this Deflection Point, the damage to your body is a lot more because it's physiological and metabolic damages.  Here's another example of "amateurish" thinking.  You go to a party and tell people you run; you run 10-miles everyday or run a half or full marathon, and people would go, "Man, I don't know how you guys can do it.  If I run a couple of blocks, I'll be huffing and puffing...!"  Again (though I wouldn't blame their lack of knowledge in human physiology), they have no clue what's going on in their body.  You take the best conditioned athlete, fittest man on earth, and have him/her "run a couple of blocks" as fast as he/she can, there'd be lots of huffing and puffing!!  You slow down so you wouldn't huff and puff so you can go far.  It actually wouldn't take that much; the elite runner would run 800m in 1:45 and they could probably run 400m in 46 or 47 seconds; some even faster.  It's not like you have to slow down twice as much in order to go twice as far.  You slow down just a bit and you can go much further than you ever imagined.

                           

                          Of course, it's not all physiology either.  This is where so many young aspiring kids nowadays fall in a trap.  They only look at physiology and, well, I guess physics and mathematics.  The act of running is actually a lot more PRACTICAL than that.  So now we should realize that, even the physical distance of 400m and 800m (or 5k and 10k or a half marathon vs. full marathon...whatever) is 1:2, energy expenditure is not quite 1:2.  We know that.  But we also know there's at least one thing that IS 1:2 (or almost) and that is # of foot steps.  So it IS true that the further you go, obviously the more steps, a lot more, steps you'd be taking.  That is a quite simple physical equation of damage--pounding.  Of course, the entire "force" is not quite so because the faster you run, the more shock you'll take in each step.  So, if you're comparing the same distance, the faster you run, the more force from the ground your body will be taking in each step.

                           

                          There's another factor associated with running faster and "more aches and pains"; that is extra stretch in tendons and ligaments.  Running faster involves longer strides.  Speed = stride length X stride frequency.  So you'll be taking longer strides.  In most cases, this means sharper angle on various joints.  Take Achilles tendon for example.  Aside from taking more force upon landing, it will be stretched out further at the take-off.  This would stretch out Achilles tendon further, causing some level of discomfort in your calves.  I know some people love Alter-G treadmill.  It gives you a sense of "false" elevated fitness level.  You can run faster and further without equal distress on a regular treadmill or outdoor.  But here are several traps; one is this joint angle.  So you can run faster without the effort of equal speed; but, because of the increase speed, your joints are working extra hard.  This mean, if you're not careful, you'll get tendon and ligament problems.  Another one is to use too much of this to prepare for a marathon.  Because it gives false sense of "working out hard", you think doing a long run of, say, 2-hours (can you imagine running on treadmill for 2 hours?  I've only done it a few times in my life-time...), thinking you've done your required long run.  Long run yes; but not pounding.  Your legs are not trained to take same amount of poundings as with 100% of your body weight.  A big part of conquering a marathon is handling poundings in your legs.  Unfortunately, you can't run a marathon with 75% of your body weight.

                           

                          Most of whom know me would be thinking, there he goes, going on and on and on...  But the point is; running actually involves a LOT of factors than many people realize.  Most people just look at it numbers; how many miles you run and how fast...  That's fine; keep it simple.  But it seems that some people start to think too deeply while just skimming through the surface.  Those are the people most likely to jump to a conclusion that, if you want to run fast, train fast.  "I need to do some speed work in order to improve my 5k time..."  Well, it ain't that simple.  To me, that's the fun part.  I had fun trying to sort things in my head, trying to explain.  "Just Do It" may sound cool and "zen" like.  But, just as many of you have so many questions, the answers may not be that simple as "just run".

                           

                          I ran without my iPod last night, and my mind really wanders without music.  I pondered this for a while:

                           

                          Why does “speed work” – whether it’s fartleks, tempo runs, intervals, whatever – put more stress on your legs/body than just regular easy running?  I think we can agree that the premise is true; if you haven’t felt it for yourself just recall how many times runners have posted on the forums about sore legs / injuries and have been advised to slow down, run easy, don’t try to do too much too soon.

                           

                          Five miles of walking feels easier than five miles at “easy” pace, which in turn is easier than five miles at “tempo” pace.  But in each case I’ve done the same amount of work – moved my 140 lb body over a distance of 5 miles.  The amount of time spent doing the work goes down as the intensity goes up.

                           

                          So what is different when you run faster?  Is it physics -- Does your stride lengthen, changing the range of motion of your legs and thus making little tears in your muscles?  Do you hit the ground harder, jarring your joints more?   Is it biochemistry – as in  lactic acid build-up?

                           

                          Theories?

                            Forgot this; yes and no.  I actually agree with you--I'd prefer going for an easy hour's jog cuz it feels easier than walking around all day.  Again, there are several factors to that.  One is posture.  If your body is not correctly aligned and balanced, walking, or even standing (!), would tire you out.  I've seen this study on military marching; some people did mention that marching feels more tiring than, say, easy jogging.  Another factor here is oxygen consumption.  Because your heart is working harder during running/jogging, you are actually getting more oxygen in your system--this actually seems more so with well-conditioned people.  Walking is way too easy for them to wake up their heart to do more work; thus at such an easy workload, their body is not getting enough oxygen.  Another thing I've found out is that walking is such a low level workload that you can almost "cheat" in body position.  I've found myself standing a bit "off" balanced while walking or waiting for my wife or daughter to check out clothes in some women's store...and that's quite a bit more tiring...and specifically hurts my lower back.  This is most probably because I walk, or stand, slightly slouched and it won't bother me much because it's such an easy level of "effort" but that bothers me in the isolated area.

                             

                            All in all, though, walking is MUCH LESS effort level.  Running, in a way, is quite unique in a sense that you project your ENTIRE body weight, against gravity, into the airborne position.  It is a lot of work.  You don't do that in walking, you don't do that in cycling or swimming.  That takes a lot more energy and effort.  We did a calculation, in terms of VO2Max and actual performance in running, not simple caloric amount.  We figured that it takes a lot more walking, cycling, swimming and any other form of exercises to equate "running".  We figured about 2-hours of all these exercise equals about 20-minutes of running.  We were flipping channels the other night and we came across "Biggest Losers" again!!  It was the episode when all these guys were running 5k.  Oh, I couldn't help but cheering everyone of them though!!  But they were struggling!!!  But, just think about it.  It's only 3 miles.  And they were stopping, bending over...  It's a lot of work!!  But I'll bet they won't have as much trouble joining Komen cancer walk 60-miles in 3 days!!  Yes, it's a lot of work; no doubt about that.  But I'll bet they started doing that and promoting it a lot more because it's easier than running 5k.  And most majority of people look at simple number (5k vs. 60-miles) and go, "Wow!!  60-miles is a greater feat...!"  I'm not so sure.

                             

                            I always find walking, and running really slow, to be more tiring than a jog or easy run. That's why when we on vacations and walk around all day, I'm more exhausted at the end of the day than if I had just did a normal run. Maybe though, it's because I'm not used to being on my feet for hours and hours.

                               

                              There's another factor associated with running faster and "more aches and pains"; that is extra stretch in tendons and ligaments.  Running faster involves longer strides.  Speed = stride length X stride frequency.  So you'll be taking longer strides.  In most cases, this means sharper angle on various joints.  Take Achilles tendon for example.  Aside from taking more force upon landing, it will be stretched out further at the take-off.  This would stretch out Achilles tendon further, causing some level of discomfort in your calves.  I know some people love Alter-G treadmill.  It gives you a sense of "false" elevated fitness level.  You can run faster and further without equal distress on a regular treadmill or outdoor.  But here are several traps; one is this joint angle.  So you can run faster without the effort of equal speed; but, because of the increase speed, your joints are working extra hard.  This mean, if you're not careful, you'll get tendon and ligament problems.  Another one is to use too much of this to prepare for a marathon.  Because it gives false sense of "working out hard", you think doing a long run of, say, 2-hours (can you imagine running on treadmill for 2 hours?  I've only done it a few times in my life-time...), thinking you've done your required long run.  Long run yes; but not pounding.  Your legs are not trained to take same amount of poundings as with 100% of your body weight.  A big part of conquering a marathon is handling poundings in your legs.  Unfortunately, you can't run a marathon with 75% of your body weight.

                               

                               

                              No wonder I got injured when running 13 miles outdoors with some elevation after 2-week treadmill runs including a 18 miles long run. I was surprised my legs didn't feel a thing next day after 18 miles on the foot hill treadmill program and was shocked that my Achilles got injured on the step-down week. Thank you.

                              5k - 20:56 (Sept 30, 2012)

                              7k - 28:40 (Nov 18, 2012)

                              10k trial - 43:08 (Mar 29, 2013), 42:05 (May 05, 2013)

                              FM - 3:09:28 (May 19, 2013)

                              Philliefan33


                                Thank you -- there's some good replies here that I will think about next time my mind wanders.

                                 

                                The act of running is very simple....left, right, left, right, repeat.  It's all the theory behind "training" that can get complicated!

                                Future Races:

                                5/4/14:  Bucks County Ten Miler

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