During the course of your chiropractic treatment, your Chiropractor may need to address the muscles and other soft tissues in order to help you get to where you want to be. Over time, particularly with chronic back pain, and sciatica for example, the muscles and tissues will become tighter and tighter in order to limit movement. Unfortunately, unless the issue that caused the muscles to become tight is resolved, they will usually remain in this state.
To get the most out of chiropractic care sometimes a chiropractor will add in, or recommend, a few ancillary treatments. Many a chiropractor will make use of acupuncture needles to help release the muscle tension. Chiropractors are not qualified acupuncturists of course, but are able, through extensive knowledge and training of anatomy to place needles into muscles in order to help reduce the tension and relax the muscle.
Other soft tissue techniques may involve using hand held tools which can apply a "massaging" function to your body. Stretching against resistance is another example of how to loosen tight muscles, for example with a tight hamstring (the muscles at the back of your thigh.) A chiropractor may try to get you to push your leg down against resistance to try and loosen the muscles.
Soft tissues, like muscles and tendons "learn" to become tight and tense, so to restore their natural functions will take time and a little bit of daily homework to maximise results. Sometimes stretching will need to become as routine as brushing your teeth.