Jurgen Freund / naturepl.com
How do crocodiles maintain their explosive power despite being motionless for long periods, while if I am sedentary, my muscles weaken?
Stephen Johnson Eugene, Oregon, US
Reptiles, such as crocodiles, and mammals, such as humans, have two basic types of muscle fibre. Slow-twitch muscle fibres support continual exercise and respond to endurance training. Fast-twitch muscle fibres support explosive power and respond to short, intense activity.
When humans are sedentary, their slow-twitch fibres will, over time, convert to become fast-twitch. As an extreme example, a person who is paralysed as a result of spinal cord injury will eventually convert their paralysed…
