Fatigue – Either physical or mental, an extreme feeling of tiredness due to build up of lactic acid
To remember what fatigue means, use the following mnemonic:
The hog was too fat and wasn't eager (fatigue) to continue the marathon. He felt an extreme feeling of tiredness after just a short time. They lacked any tactic (lactic acid) to get the hog going again.
Note: During sustained physical activity, the primary cause of fatigue is the build up of lactic acid in the muscles. This build up causes the muscles to become less able to contract effectively, leading to a decrease in performance, and if left unchecked, can result in muscle failure.