September 17th, 2008
10:17 AM ET

Making gravity work for you

By Dr. Sanjay Gupta
CNN Chief Medical Correspondent

This week, I did a series of pieces about how astronauts stay fit in space. Sure, it was fascinating to be strapped into a system of pulleys and harnesses that effectively simulate weightlessness. It was interesting to be pulled up to a vertical treadmill or eZLS – the enhanced zero gravity locomotion system. And, yes, I got to be an astronaut for a day, experiencing firsthand what it may feel like to exercise in space. (watch video)
I learned that exercise in space, especially for those long missions, is essential for astronauts, not something you might do occasionally. It has to be comfortable to do and it cannot interfere with the function of the spacecraft. (read more)  More than that, though, I learned how beneficial gravity is for us on Earth. Doctors call it axial load. You can think of it as a slight tension on our bodies, more importantly our ligaments, tendons and bones. Turns out, this slight pulling of gravity slows down the loss of bone mass, which in space accelerates 10 times faster than a post-menopausal woman.

The message for the rest of us is to embrace gravity. In addition to your aerobic exercise, which you should do most days of the week, add some axial load to your routine. And, this is a message for everyone, especially women in their 40s and 50s who will have to deal with menopause. Pick up some dumbbells, park yourself under a bench press or learn how to use a cable system. It’s good for your health and for your bones.

Are you doing something to make gravity benefit your body?  

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soundoff (10 Responses)
  1. Sharon from Indy

    Dear Dr. Gupta:

    Does aqua-aerobics count as axial load exercise? Because of arthritis, the use of dumbbells and and bench press can be very painful. I do use small floatation dumbbells and water weights during my aqua-aerobic routine though.

    I think humans were to flourish on earth. But outer-space does sound like a fascinating place....maybe on a short-term basis.

    September 17, 2008 at 14:51 | Report abuse | Reply
  2. Andrea DeBalko RN

    I agree with the Doctor on this topic.Gravity....After a discussion with my primary physician on the benefits of an inversion table to be used as directed per manufacturer
    . Myself as well as my husband have extreme total body relaxation while using this product. The vertebrae are actually felt pulling back into their correct alignment.
    I have never felt the weightlessness of an astronaut, but I believe this is pretty close to that experience.
    Thank You for a great topic.
    Andrea DeBalko RN

    September 17, 2008 at 15:11 | Report abuse | Reply
  3. Melissa, Los Angeles

    I had no idea gravity was a part of preventing the majority of bone loss. I've always done weight bearing exercises with dumbbells and weight machines since I heard it's good for the bones along with keeping the metabolism rate going.

    September 17, 2008 at 18:51 | Report abuse | Reply
  4. Dr Gravity

    As always, be sure to consult your personal doctor prior to starting any new exercise regine. And also...be sure to utilize gravity in moderation. A friend of mine just had a freak encounter with too much gravity which overstressed his knee ligaments...

    The type of gravity best used for exercise is usually found closer to the ground.

    Do not assume that increasing your axial load by overeating is beneficial.

    September 18, 2008 at 07:01 | Report abuse | Reply
  5. Gill in San Diego

    Let me see if I have this straight:

    In everyday life, if I gain more weight then I will experience more of the effects of gravity on my skeletal frame, and this can actually be good for me?


    September 18, 2008 at 07:31 | Report abuse | Reply
  6. Gita

    An axial load is a load that is applied normal to the long axis of the bone(in the context of what Dr Sanjay was writing). Water-based exercise can't replace the weight bearing exercises. But you should be able to do smooth transition from water to land based exercise. Suppose I place a weight on my spine(that's an example of axial load). Do you do like that when you are doing aqua exercise? When a person lifts a weight, he/she should experience some discomfort/stress but not too much(one may brake bones or rip muscle). That means he/she is working the bone/muscle.

    Water is an excellent medium. Has interesting properties(from Chemistry point) unlike any other compund. Let's not forget our body's 2/3rd content is water only.

    SPA stands for Salus per Aquam. Water relaxes the body as well as the mind. But it will not build bone mass or bone strength. Water buoyancy will facilitate a person in trying a range of stretching motions in water.

    Some exercise is better than no exercise at all. Don't give arthritis as an excuse not to do some light weights. Depending on your condition, start with 1 lb dumbbell. My cousin sister suffers from RA. Her condtion is worse. I tell her the samething. Initially it will be painful. There is always the "inertia". The reason I am telling you this is I used to do lot of really "flexible exercise" when I was in my teens and early twenties. My back would be very flexible. But for a decade I stopped some of those exercises but continued with my regular push-ups,walking/running, some crunches. Again I have started pushing myself doing some stretching exercises. I think "oh my god, how my body is used to bend but not anymore". But I'm improving. It's not easy for even a person who has been athletic.

    I would prescribe "40-50 mnt exercise daily" for women(applies to men too) especially past 35 yrs. As we grow older, our metabolism slows down and the only way to keep ourselves healthy and fit is by doing exercise daily. There is no other short cut.

    My cousin, has Juvenile RA, while talking to us, all of a sudden her shoulder joint got dislocated and her right arm was hanging loose. Everybody was panicking but not me. Because my father knows a lot about medicine and has taught us some emergency tricks. I immediately got some oil and started giving her a massage and the arm, after couple of circulatory motions, got clicked at the right spot and my cousin sis, screams "stop". Before even my other relatives tried calling the ambulance this oil massage worked out!

    Finally, don't stop the water exercise. It will relax your muscles. But wrt bones, start thinking about walking(choose a path that has some elevation,that way you put slight stress on your knee) atleast 20mnts daily, give some oil massage for the joints. If there is no blood circulation, the joints become stiff. Oil massage(any oil will do as oil is a lubricant, makes the flow smooth) works great. Try it. Hot packs(water), cold packs(ice) also improve the flow in and around the joints.

    With small kids, you can do this exercise. This is good for the lower half. I do this with kids under 8-9 yrs(depends on their weight). I sit on a chair and stretch my legs and tell the kid to stand on my feet. I will hold the kid's hands(so that the kid doesn't fall) when I lift my legs up and down.

    September 18, 2008 at 12:53 | Report abuse | Reply
  7. Trying to get Gravity

    The strenth of Gravity is defined by the mass of the object so said Einstein, but is gravity a pulling force from below or a pressing down from space.

    Gravity can be replecated in the kitchen sink when things that are floating in dirty water are attracted to a glass sitting in the soapy dirty pot.

    I believe gravity is created by the displacement of space.

    September 28, 2008 at 16:04 | Report abuse | Reply
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Get a behind-the-scenes look at the latest stories from CNN Chief Medical Correspondent, Dr. Sanjay Gupta, Senior Medical Correspondent Elizabeth Cohen and the CNN Medical Unit producers. They'll share news and views on health and medical trends - info that will help you take better care of yourself and the people you love.