Most athletes have heard some version of "no pain, no gain," and most have also learned to tell the difference between a leg that feels worked and a leg that feels wrong. The trouble is that memory is unreliable. By Tuesday, a sore calf can feel better or worse than it did on Sunday, depending on what you are thinking about. A short written note fixes that problem, and it does not require any medical training.
Delayed soreness, often called DOMS in training circles, usually shows up a day or two after unfamiliar or hard work. It tends to feel dull and spread across a muscle group, and it often eases as you warm up. That pattern is worth recording, but it is not the same as an injury signal. Injury-type pain is more often sharp or pinpoint, sits over one spot, gets worse with the activity itself, or hangs around when you rest.
Four questions for each entry
Start each training day with a simple line. Answer four things in plain words: where exactly it feels tight or sore, whether it feels the same on both sides, what happens when you move, and what it does after you rest. Write the answers before you warm up, not after the session, because that is when your memory is most likely to tidy things up. The goal is consistency, not length. A three-line note written the same way each day is more useful than a long essay written once a week.
Use the same words every time. If you call something "tight" on Monday and "pulling" on Thursday, you have two different descriptions, and you cannot tell whether anything changed. Pick a short vocabulary such as sore, tight, sharp, burning, numb, or unstable. Add one line for the activity and the surface you played or trained on, since a hard cut on a wet field and a long run on pavement can produce very different reactions.
Signs that should move you up the list
Some patterns in a log are reason to stop guessing. Write them down with the date and time, then treat them as a reason to plan an exam rather than wait for the next session. Look for pain that is sharp at one point and does not ease with warm-up, swelling that appears or grows over several days, a limb that feels weaker or less steady than the other side, numbness or tingling, pain that changes how you walk or stand, or soreness that keeps you awake at night.
Also note what you did about it. If you stopped training, wrapped the area, took a medication, or pushed through the first ten minutes to see whether it would settle, write that down. A log that shows you tried three things over four days is far more useful to someone examining you than one that says "it has been bugging me."
What this log is not
A training note is not a diagnosis. It cannot tell you whether a tendon is irritated, a muscle is strained, or a bone is under stress. Only an in-person exam, and sometimes imaging, can separate those possibilities. Your job is to record what you noticed clearly enough that an examiner has something real to work from.
If you are in the St. Louis metro and the pattern in your log matches any of the warning signs above, make the call this week rather than at the end of the season. Bring the log with you. Ask whether the examiner wants to see the entries from the days before the first symptom, not only the most recent one. If you have symptoms that are severe or sudden, or that involve chest pain, trouble breathing, or loss of function, do not wait for a scheduled visit. Contact emergency services right away.