Is there a function in humans analogous to flying in birds?
In: Biology
It’s all just muscle use. Contracting a muscle requires the expenditure of energy. This in turn requires oxygen. You get tired when you’re using more energy than you have oxygen supplies. This causes cells to produce energy by less efficient pathways that don’t require oxygen, but a byproduct of this is lactic acid. Too much acid can cause all sorts of problems, so when your body detects a buildup of acid in a muscle, it sends a signal to your brain that your brain interprets as pain and getting tired. If a bird uses energy fast enough for this lactic acid to build up, it’ll get tired just like a human does. However, it’s worth noting that much of a bird’s flight is simply gliding on air currents. Most of the energy expenditure in this is just small adjustments in tip feathers to do things like make turns. That doesn’t cost much, so while gliding there won’t be a great deal of tiredness.
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