Guess the centre of gravity

Yes, it's gravity again, as I am still working through the importance of the centre of gravity and how the weight of the human body is supported. Knowing the centre of gravity turns out, is just very useful, for balancing, trying to decrease muscle strain, prevent injuries e.g. through lifting or excessive forces on joints, predicting how a body moves through space ....

So I searched the internet for a source of an approximate weight of the individual body parts of a human body to help me demonstrate where the centre of gravity is.

In general, the centre of gravity, is the point, where there is the same amount of weight above and below, on either side and front and back, i.e. if you draw lines through the centre of gravity, you will cut the body in equal halfs of weight left and right, front and back, up and down. Also if you were to suspend a body from the ceiling, attaching the rope at the centre of gravity, the body will stay just as it is, no rotation occurs, as the weight of the body is equally balanced.

So here is an example body with each of the body parts drawn according to its weight. Larger areas = more weight, smaller areas = less weight. Different densities of the body materials, bone, muscle, water and fat have been considered in this example.

 

Weight per body part:

Head and Neck:           8 %

1 Arm:                          5 %

Torso and Pelvis:         50 %

1 Thigh:                       10 %

1 Lower leg and foot:    6 %

Head/Neck/Arms/Torso

=

Feet/Lower leg/Thighs/Pelvis

Toezeren, Aydin (2000) Human Body Dynamics: Classical Mechanics and Human Movement. Springer: New York. (pg. 302)

I used percentages rather than actual numbers, as it then can applied to different body weights. For a 60 kg person the head and neck weighs 8% of 60 kg = 4.8 kg. So you can calculate your own approximate body part weights.

The percentages are rounded to nice whole numbers from a range of values given in Toezeren's book. These values are an example only. Everyone will differ according to their measurements. Men tend to be more top heavy with a slightly higher centre of gravity and women bottom heavy.

So having an idea on how the body weight is distributed throughout the body, where would you guess the point of gravity of the human body is, in the following pictures? You can compare your guesses with mine later.  Remember, at the centre of gravity the weight below and above is the same and the weight left and right, i.e. from a side view of the body, the body is cut into four equal-weight quaters. 

I     I

I     I

I     I

I     I

I     I

I     I

I     I

I     I

I     I

I     I

I     I

I     I

V    V

HERE ARE MY ANSWERS (the CoG is where the lines cross):

How did you do? Surprising, how little the point of gravity changes with different postures, even extreme postures. I suppose it shouldn't be, as most of the weight is carried in the trunk/pelvis. Useful though, as the point of gravity always has to be vertical above the body support (contact point with the floor or space between contact points to the floor) for us to be able to balance. 

This means, the centre of gravity has to be above our feet/foot or in the space between our feet, when we are standing, for us not to fall over. As we have only little feet compared to the length of our body and tend to keep the feet close together, it's a good thing that the point of gravity doesn't change noticably with the movement of limbs for example. A lot easier to balance like this.

I have a couple of blogs lined up on squatting and lower back pain and knowing the point of gravity of a human body gives greater insight into the issues in the upcoming blogs. 

Why am I writing this blog?

I started this blog a year ago now to help collect information that may be useful for my clients - Mums to be and New Mums. Whenever there was a question that popped up in class that needed a little more illustration, I have tried to answer it on here, very ad hoc and with no particular thread.

Since I started the Wholebody Alignment Course with Katy Bowman, I have been sucked into thinking about the more general topic of alignment and optimal alignment at that and health. Still very important for Mums to be and New Mums but not specific to them.

I have also been reading or are reading lots of books, see booklist at the bottom of this page.

On top of that I enjoy researching on the internet (pubmed) and discussion with fellow RES students to be able to catch up on the world of my body. So much to know.

Most recently, I have found the amazing COURSERA  website, that offers free (yes FREE) courses run by university all over the world on so many exciting topics. I have had a quick look at a Bioelectricity course as this course had already finished but was still open to listen to the lectures. Very interesting. The human physiology course is the next one I have signed up for.

If you are a stay at home mum, who needs some stimulation for the brain other than baby, I can highly recommend those. The lectures come in 5 - 10 min chunks and are easy to fit in. You will get a certificate if you finish the course but you don't have to.

So now the blog has turned into anything I have just learnt and find really interesting, mostly because it was:

-  revolutionary to me because it was the opposite to my previous knowledge,
-  stuff I would have liked to have known 20 years ago to safe myself physical and mental       pain
- or just a record of my thought process to help me understand a topic.

Our body is absolutely fascinating. So with this rebranding blog, may I present the new title of this blog:

THE MUSINGS OF A BIOMECHANICS AND PHYSIOLOGY STUDENT

All information is to the best of my knowledge but since I have only started to engross myself in this topic in 2011, there are still major gaps in my knowledge and I shall try and reference my sources, so it's easy to check this info for yourself. I shall keep the name of the blog MumsKeepFit but the topic will include information for everyone.

I hope you enjoy this blog and find some really useful info and references.

My background:

I grew up in the Austrian mountains and moved to England when I was 19. I studied at Oxford Brookes Univeristy, taking Environmental Sciences and Geography. For my final project - a comparison of cloud water and rain water chemistry at different altitudes - I was running up and down moutains in the rain to collect cloud and rain water sample. For this project I received two awards: the George Irvine award to best project in Geography and the Unipart prize for best undergraduate project in biological and molecular sciences. 

I went on to study for a Masters in Research in Atmospheric and Earth Sciences at Reading university. I specialised in Meteorology and for my research project compared different methods of forecasting dekadal rainfall in Zambia with the TAMSAT group at Reading university and the Zambian meteorological office. Dekadal rainfall (10 day accumlated rainfall) is a good indicator for the start of the rainy season. If farmers think the rainy season has started but it was a false start the plants will not grow or die from draught. If they wait to long to make sure the rainy season has started, then the rains may be too strong in the beginning and flood little plants. For the comparison I used heavy duty statistics and geospatial imaging methods.

After univeristy, I worked at the Met Office (weather not police) for six years and was invovled in generating products for site specific forecasts for commercial, government and defence clients. I then went on to some statistical weather forecasting and very involved database programming and testing. Such fun. No it really was pretty interesting.

In the end, my two lovely children came along and I was ready to change from sitting on my backside to moving about. I trained as a fitness instructor for ante- and post-natal ladies and started running classes at the local fitness centre, village halls and private swimming pool. Pregnant and post-natal ladies absolutely rock. From there my interest in the human body grew.

My book list (Dec 2012):

Biomechanics degree level course books:

Hall, Susan (2012) Basic Biomechanics. 6th Edition. International Edition. McGraw-Hill. New York.

Sherrill , Claudine (2004) Adapted Physical Activity, Recreation, and Sport. Sixth Edition. McGraw-Hill. New York.

General interest books:

Voijta, Vaclav and Edith Schweizer (2009) Die Entdeckung der idealen Motorik. Pflaum Verlag. Muenchen.

And exercise and pregnancy books:

Baines, Susan and Susie Murphy (2010) Aquatic Exercise for pregnancy. M & K. Keswick.

Baker, Cherry (2006) Pregnancy and Fitness. A&C Black, London.

Balaskas, Janet (2004) The Waterbirth Book. HarperThorson. London

Barbira Freedman, Francoise (2004) Yoga for pregnancy, birth and beyond. DK, London.

Barbira Freedman, Francoise (2003) Aqua Yoga for pregnancy. Southwater. London.

Bowman, Katy (2011) Every Woman's Guide to Foot Pain Relief. BenBella Books. Texas.

Clapp III, James F. (2002) Exercising through your pregnancy. Addicus Books. Omaha.

Coad, Jane (2005) Anatomy and Physiology for Midwives. 2nd ed. Elsevier. London

DiFiore, Judy (2006) Pregnancy exercise. Carroll and Brown, London.

DiFiori, Judy (2003) The complete guide to postnatal fitness. 2nd ed. A & C Black. London

Halksworth, Gillian (1994) Aquanatal Exercises. Books for Midwives Press. Hale.

Hibbitts, Mark and Martin Beckley (2008) The Essential Exercise and Birthball Handbook for Pregnancy and Beyond. Miracle  Products. Chippenham.

LeVay, David (1988) Human Anatomy and Physiology. Hodder & Stoughton. London.

Laurence, Matt (2007) The complete guide to core stability. 2nd ed. A & C Black, London.

Lawrence, Debbie (2005) The complete guide to exercising away stress. A & C Black. London

Norris, Christopher M. (2007) The complete guide to stretching. 3rd ed. A & C Black. London.

Patel, Kesh (2008) The complete guide to postural training. A&C Black, London.

Robinson, Lynne et al. (2000) The official body control pilates manual. Macmillan. London.

Schwarz, Kerstin (2010) Rueckbildungsgymnastik. GU, Muenchen.

White, Martha (1995) Water Exercise. Human Kinetics. Houston.