There are lots of bad things about "tight" muscles, and you should be concerned about them. The most important thing is that muscles work together with bones and joints to give us mobility. If your muscles are especially tight they wil affect your posture and gait and cause joint pain and "muscle imbalance". Also, each muscle has an opposite that releases when it's partner contracts. For example, you quads are opposite muscles to your hamstrings. Runners traditionally have tight hamstrings. In addition to stretching the hams, most experts recommend you also make sure to work the quads through additional exercises. For example, run one day and bike the next or mix sqats and lunges to your leg days. Your IT Band is causing knee problems and may very well be the underlying cause of your issue. The foam rollers are a great place to start identifying where you are tight and can help to release the tightness. Be sure to do them slow and relax into the pain. I promise it will get better. Also do the stretches she recommends to warm muscles on a regular basis. So, pay attention to yur trainer and ask the tough questions. If you do not get a satisfactory answer, keep asking or find a new trainer. This doesn't mean she doesn't know what she is doing, but that you may have different communication styles, which is just as important in finding the right trainer for you. good luck.
I refuse to give up control for convenience
230/180/TBD (size 10?)