Are you one of those people who choose to improve your immunity?  Do you have one of those immune diseases like Chronic Fatigue?  Even though nutrition is very important at building your immune system (remember what you eat today is your immune system for the next 3 months), isometrics also assist your body to improve the body's ability to keep your immune system working.   According to Charlotte Watts, 20 to 30 minutes of exercise a day keeps your liver working properly.  Especially the calves and thighs and keeping good posture and good abdominal muscles.   You can do this with isometrics.  Reading such books as Natural Flexibility by Charles Kenny, The Supple Body by Sara Black or Stretch & Relax by Maxine Tobias and Mary Stewart will give you simple exercise routines you can work into your schedule.  The result is better health!