There are chair yoga versions of most postures to increase mobility, vitality and flexibility: sun salutation, forward bends, back bends, spinal twists, sitting mountain pose, eye exercises (helps computer strain) and breathing exercises (calms or energizes and increases concentration). If there aren't modifications for poses you enjoy, you can create your own. Some movement is almost always better than no movement.
The Achilles is a tendon that connects your two major calf muscles to the heel bone. When it is placed under too much stress, which is a common occurrence for runners and other athletes, it can become less flexible and even inflamed. An inflamed Achilles tendon can eventually tear, which is why any runner should take steps to protect their Achilles and recognize the symptoms of inflammation before they get to be too much.
As we move from one season into another, extreme temperatures can sneak up on you. It can be quite pleasant one day, then abnormally hot or cold the next. During this time of transition, it's particularly important to guard against temperature-related illnesses.