# Why is it harder for women to do push ups then men?

1. Apr 12, 2005

### gillgill

Why is it harder for women to do push ups then men?..is it something about their center of mass?

2. Apr 12, 2005

### UrbanXrisis

yeah, it's lower on the body than the average male

3. Apr 12, 2005

### rocketboy

They have heavier upper bodies.......:D

4. Apr 12, 2005

### gillgill

Woman have a lower center of mass than men. Why does this help them to do sit-ups but make it harder to do push-ups?

5. Apr 12, 2005

### UrbanXrisis

if the center of mass is lower, then they need a larger force to lift their body from a pushup (since the radius is larger) to generate the same amount of torque as males.

6. Apr 12, 2005

### whozum

Maybe some of you hae heard this:

In high school my physics professor had a guy and a girl of average size take a chair and put it between them and a wall (standing distance). They then bowed their heads against the wall so their backs were parallel to the floor, and the chair was between them. He asked each student to pick up the chair. Only the girl could do it. none of the guys in the class could.

i'm still not sure why

7. Apr 12, 2005

### gillgill

what about situps?

8. Apr 12, 2005

### whozum

Set up a model where your butt is the axis of rotation, and a line coming outwards representing your body. if the CM is closer to the axis of rotation for girls, what is true about the amount of torque needed when compared to boys? Why is this?

9. Apr 12, 2005

### gillgill

small amount of torque is needed for girls because it is exerted at a much greater distance?

10. Apr 12, 2005

### whozum

What is the equation for torque, in terms of force and distance?
Given the formula, tell me what conditions make torque small, and which make it big.

11. Apr 12, 2005

### gillgill

T=Fxd.....small force can exert greater torque than a larger force if the small force is exerted at a greater distance of at angle close to 90 degrees from the pivot...

12. Apr 12, 2005

### whozum

When were talking about how 'easy' it is to do something, does that mean we want to apply a great amount of force or small amount?

Its easy to pick up a 1lb dumbbell, but a 100lb dumbbell may not be the case, why?
Apply this concept to the torque.

T=f x d. If F is the same, and d is really small, then the torque is _______ . If d is really big, then the torque is _______ .

13. Apr 12, 2005

### gillgill

T=f x d. If F is the same, and d is really small, then the torque is small. If d is really big, then the torque is large.

14. Apr 12, 2005

### whozum

So is it 'easier' to exert a small torque, or a large one? How will this apply to girls' ability to do situps? Remember, their 'd' is smaller.

15. Apr 13, 2005

### gillgill

will the girls' d be larger because their cm is lower?

16. Apr 13, 2005

### FredGarvin

No it is not due to the CM. Think about a man and a woman who have the same exact distance from their feet (pivot point) to their shoulders. On the man, the center of mass is closer to the arms which results in a larger moment created by the CM which thus requires a greater force from the arms. That also means that the male has to do more work to lift (rotate) the load $$W_{NET} = \tau \theta$$.

Now consider the woman. Her CM is closer to her hips and thus closer to the pivot point (feet). This means the CM is exerting a smaller moment and thus requires a smaller force to do the movement. So, theoretically, if there were an equivilent male and female in terms of muscle development and proportions, it should be easier for the woman to do a push up.

The main reason it is tougher for women is because of the muscle groups required to do the push up. The three big ones involved are the pecs, the deltoids and the triceps. ON AVERAGE, these are larger, better developed in males. That being said, I have seen many women that kick my butt in push ups. There are a lot of factors to consider.

As far as the sit ups are concerned, the CM definitely plays a part. The female's CM is almost directly on top of the pivot point, let's say the hips. In a male, the CM is located closer to the torso, so it produces a larger opposing moment. Ab muscle development on men and women tends to be much more even between the sexes, so it is a fair assumption to make that the two could exert the same force.

17. Apr 13, 2005

### whozum

Reread and think about my last post.

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