Another treadmill thread: is everybody wrong?

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In summary, My roommate and physics professor disagree about how to measure horizontal force when running. The professor believes you need to exert a horizontal force at a 45 degree angle to the ground with each stride, while my roommate believes that when you're running at constant velocity with ideal form, you don't exert any horizontal force on the ground. However, assuming that the two of you are both on the same page, Newton and Einstein would also be interested in my findings that there is nothing to the argument.
  • #36
luigidorf said:
Also, the running graphs that you found (thank you by the way) are from a runner with poor form: the spike that occurs around 0.1 s on the vertical force graph is representative of a heel-strike, which results in a significant breaking force and thus requires more propulsive force. For a runner with good form, there would probably still have to be a slight horizontal force to prevent torque, but I think it would be significantly less than 200 N.
200N seems consistent with this:

http://jeb.biologists.org/content/203/2/229.full.pdf
Where they tested 8 "experienced treadmill runners" (control without modifications).
Peak breaking force : 221±5N
Peak propelling force :169±4N

And this:
http://www.mlmixrunning.com.br/artigos/subida_descida.pdf [Broken]
Level TM control:
Peak breaking force : 195±21N
Peak propelling force :169±12N

But maybe you mean forefoot strikes? They have no heel strike peak:

https://www.youtube.com/watch?v=TjrEyfQC5NQ

Compared to heel striker:

https://www.youtube.com/watch?v=wuBLkKnNKm4

I assume the horizontal peak is smaller as well for forefoot strikers. But the horizontal impulse might be the same, just distributed over a longer time span.

But regardless what the horizontal forces are, there is no mechanical reason for a difference between a treadmill at constant speed and running on ground with zero relative wind and constant net running speed. And the measurements with the instrumented TM show the same forces as on ground.
 
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  • #37


A.T. said:
But regardless what the horizontal forces are, there is no mechanical reason for a difference between a treadmill at constant speed and running on ground with zero relative wind and constant net running speed. And the measurements with the instrumented TM show the same forces as on ground.
He has acknowledged this (actually, it was his stance all along, it was his friend that thought there'd be a difference.)

He's since moved on to this idea of horizontal force.

See Post 6.
 
  • #38
russ_watters said:
Note that once you are moving, Newton's 1st law demands that all horizontal forces sum to zero. So the only net/external forward force you provide is against wind resistance.

The vast majority of the energy expended while walking or running is in supporting (or bouncing!) yourself against gravity. And the longer your stride, the lower the angle and therefore the greater the force.

If you are not accelerating, the mean horizontal force is zero BUT - When you put your leg forward, when you are running at constant speed, and it hits the ground, I think there is an initial force / impulse 'against' your motion. You don't land on your front foot with the foot stationary relative to the ground immediately before contact. This will involve losing some energy as you absorb this impulse (a loss mechanism) and you need to make up for this by pushing forwards during the subsequent pace. In addition to this, there is energy lost as you sink down and lift up during each pace. There is a certain amount of 'energy return' in the resilience of the tendons but when muscles are under load they are actually expending energy ( they are not just like springs). This implies that running forward at constant speed takes more energy than running on the spot.
 
  • #39


A.T. said:
But regardless what the horizontal forces are, there is no mechanical reason for a difference between a treadmill at constant speed and running on ground with zero relative wind and constant net running speed. And the measurements with the instrumented TM show the same forces as on ground.
DaveC426913 said:
it was his stance all along
I know. And I agreed with him on this. See post #34.
 
  • #40
A.T. said:
200N seems consistent with this:

http://jeb.biologists.org/content/203/2/229.full.pdf
Where they tested 8 "experienced treadmill runners" (control without modifications).
Peak breaking force : 221±5N
Peak propelling force :169±4N

And this:
http://www.mlmixrunning.com.br/artigos/subida_descida.pdf [Broken]
Level TM control:
Peak breaking force : 195±21N
Peak propelling force :169±12N

But maybe you mean forefoot strikes? They have no heel strike peak:

I assume the horizontal peak is smaller as well for forefoot strikers. But the horizontal impulse might be the same, just distributed over a longer time span.

I was indeed referring to forefoot (and some mid foot) strikes. I was careful to refer to runners with "good form." Heel striking is bad form, and even if the runners in that study were "experienced," they likely still heel strike due to growing up wearing shoes. This discussion actually sheds quite a bit of light on why forefoot striking is more efficient: the spike in vertical force also suggests a spike in horizontal force, which means more propulsive force must be exerted each stride.
 
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  • #41


A.T. said:
But the horizontal impulse might be the same, just distributed over a longer time span.
luigidorf said:
This discussion actually sheds quite a bit of light on why forefoot striking is more efficient: the spike in vertical force also suggests a spike in horizontal force, which means more propulsive force must be exerted each stride.
See above. Smaller horizontal peak force doesn't imply "more efficient". The total horizontal momentum transfer (impulse) could still be the same.

You would have to compare the horizontal impulses for forefoot and heel strikers. Maybe these guys have already done so:
http://barefootrunning.fas.harvard.edu/
 
<h2>1. Why is there so much debate about treadmills?</h2><p>There is debate about treadmills because they are a popular form of exercise equipment and there are differing opinions on their effectiveness and safety. Some people believe that treadmills are a great way to get a cardiovascular workout, while others argue that they can cause joint and muscle injuries.</p><h2>2. Are treadmills bad for your joints?</h2><p>There is no definitive answer to this question as it depends on individual factors such as weight, running form, and frequency of use. However, some studies suggest that running on a treadmill may put more stress on the joints compared to running outdoors on a softer surface. It is important to listen to your body and make adjustments as needed to prevent injury.</p><h2>3. Can you lose weight by using a treadmill?</h2><p>Yes, using a treadmill can help with weight loss as it is a form of cardiovascular exercise that burns calories. However, weight loss also depends on other factors such as diet and overall activity level. It is important to have a balanced approach to weight loss and not rely solely on using a treadmill.</p><h2>4. Is it better to run on a treadmill or outside?</h2><p>It ultimately depends on personal preference and individual goals. Running on a treadmill can be more convenient and controlled, while running outside can provide a more varied terrain and fresh air. Both have their benefits and it is important to choose the option that works best for you.</p><h2>5. How long should I use a treadmill for?</h2><p>The recommended amount of time for using a treadmill varies for each person depending on their fitness level and goals. As a general guideline, the American Heart Association recommends at least 150 minutes of moderate-intensity exercise or 75 minutes of vigorous exercise per week. It is important to listen to your body and gradually increase the duration and intensity of your treadmill workouts.</p>

1. Why is there so much debate about treadmills?

There is debate about treadmills because they are a popular form of exercise equipment and there are differing opinions on their effectiveness and safety. Some people believe that treadmills are a great way to get a cardiovascular workout, while others argue that they can cause joint and muscle injuries.

2. Are treadmills bad for your joints?

There is no definitive answer to this question as it depends on individual factors such as weight, running form, and frequency of use. However, some studies suggest that running on a treadmill may put more stress on the joints compared to running outdoors on a softer surface. It is important to listen to your body and make adjustments as needed to prevent injury.

3. Can you lose weight by using a treadmill?

Yes, using a treadmill can help with weight loss as it is a form of cardiovascular exercise that burns calories. However, weight loss also depends on other factors such as diet and overall activity level. It is important to have a balanced approach to weight loss and not rely solely on using a treadmill.

4. Is it better to run on a treadmill or outside?

It ultimately depends on personal preference and individual goals. Running on a treadmill can be more convenient and controlled, while running outside can provide a more varied terrain and fresh air. Both have their benefits and it is important to choose the option that works best for you.

5. How long should I use a treadmill for?

The recommended amount of time for using a treadmill varies for each person depending on their fitness level and goals. As a general guideline, the American Heart Association recommends at least 150 minutes of moderate-intensity exercise or 75 minutes of vigorous exercise per week. It is important to listen to your body and gradually increase the duration and intensity of your treadmill workouts.

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