During a session with a client whom I am helping with, strengthening her weak back and knee, she complained her hamstring was tight.
We did some squats and side lunges and before that she walked on the treadmill for 20 mins. Nothing sounded too strenuous even by her assessment. We wondered why her hamstring was so tight. She tried massaging her calf and it was tight, and her lower back was also aching and was in slight spasm. Massaging her calf and stretching out her back seemed to help.
The reality is that my client has never question why her calf is tighter than normal people, even athletes who work out a lot more. This is inference kind of pain and issue; indirectly caused by some other part of the body that caused this part to be weak and tight, no different from people who hunched because their back muscle is not strong enough to pull the back the slumped shoulders and thus their neck and shoulder area gets tight. Neck pain is likely to come from slumped back.
She also lamented that the school PE classes don’t teach practical stuff like and she would think about doing something about it years ago instead of knowing it at almost 50!