Question Details	Asked By	Asked On
this is a big problem for me (biology)	izwan	09/28/07
A person carrying a heavy bag normally finds the impact of the weight differently if he carries it in different ways. For example if he carries it by the handle or by a strap on the shoulder or putting the whole bag on top of his shoulder. Why is this so (as the weight of the bag is the same in all the cases)?
Answered By		Answered On
Jim.McGinness		09/28/07
Different ways of carrying the bag distribute the stress and strain to different parts of the body. The body's muscles must do work (continuously) to keep the bag from toppling one over. Carrying the bag in the hand, by the handle, causes all of the weight to be considerably offset from the axis of the spine. Carrying it on the shoulder is almost as bad but closer to being on-axis. A strap going around the shoulder may be arranged so as to minimize the amount of off-axis strain on the spine. Carrying a load on the head (or with a tumpline) aligns the load with the spine. This can be overdone, but is the best way for humans to carry heavy loads over distance.

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