Muscle & Bone

Backbones
The backbone is made up of 32 little bones, and helps us bend and twist. Between each bone is cartilage that allows the bones to move around. As an example, we made a model backbone.

We tried bending a straw without letting it break, but we could hardly move it. A bone that can't bend is good for your arm or leg, but not your back.

We cut the straw into little pieces, and strung them onto a string. It was much easier to move this way. This is more like our backbones.















Muscle Fatigue

Muscle fatigue can happen when you do the same thing over and over without stopping, such as working in a factory. We found out about muscle fatigue with an experiment. I opened and closed a clothespin as many times as I could for 30 seconds, and recorded the results. We tried this four times, and the results are below:

1. 76 times
   


2. 73 times


3. 62 times


4. 61 times

This shows that if you do the same thing over and over again, you get worse at it because your muscles get tired. This is called muscle fatigue.