Let's start with disuse. Your body is an extremely efficient machine. The phrase "if you don't use it you lose it" applies to the majority of physiological processes. The common example most of us are familiar with is the affect exercise has on muscle. Various training methodologies can result in vast increases in strength, hypertrophy (increased size), power, and endurance just to name a few. If your goal is to gain muscle mass but you decide to no longer maintain your current conditioning, your body will see this extra muscle as no longer being necessary. This is due to its lack of use and the fact that carrying this extra muscle mass means additional energy is required to maintain your current state - energy that could potentially be saved and put to use elsewhere. This training adaption theory and practice reaches far beyond just affecting muscles. Bones respond to the stress put on them, and when done in a favorable manner, it can help prevent osteoporosis - a decrease in bone density and strength that plagues older individuals. Studies have consistently shown that completing activities such as crosswords and sudoku - essentially conditioning your brain - helps decrease the likelihood of cognitive decline that is so commonly seen in the aging population. Similarly, the nervous system adapts to the stresses we put on it. "Nerves that fire together, wire together" is a common saying that emphasizes this point. By limiting the types of movements we perform on a daily basis, our "movement vocabulary" becomes limited. When we then ask our body to perform a movement that is uncharacteristic of our daily activities, we may stumble through it with varying degrees of compensation. This is a huge contributor to injury. Challenging yourself both physically and cognitively in a controlled manner on a regular basis is the best way to avoid disuse induced dysfunctions. Find activities you enjoy, and run with it - it shouldn't feel like homework.
In part one, I briefly discussed how improper breathing technique can lead to a host of problems including but not limited to neck pain and low back pain. This type of dysfunction - in my opinion - falls under the misuse category. As mentioned earlier, the process of breathing is still carried out for obvious reasons, but some muscles are working overtime (scalenes, SCM, etc.) while others extend their coffee break ("deep core musculature such as the diaphragm, TA, pelvic floor). Now I don't prescribe to any one intervention in particular for a "misuse" dysfunction such as this. There are numerous techniques that can help address breathing dysfunction in a clinic and home setting and I believe that addressing the dysfunction through several practices/techniques is best. Yoga and meditative practice can be extremely beneficial. Dynamic Muscular Stabilization (DNS) and various physiotherapy, chiropractic, osteopathic and cognitive techniques can help address breathing dysfunctions. Other more "fringe" therapies such as R.E.S.T/float therapy have proven (anecdotally at least) to be very beneficial for such issues. The best way to avoid a misuse dysfunction such as the one mentioned above is to take initiative. If you feel like you may have some form of breathing dysfunction, ask your local health care provider to either assess you or refer you to someone who may have more experience in treating those dysfunctions. If you don't currently have a breathing dysfunction, then keep it that way by maintaining your current practices that may be helping to keep you dysfunction-free. Or, try some new practices/therapies like yoga, meditative practice, or R.E.S.T/float therapy if you haven't already.