if you have a sore stiff lower back try and follow along with Gentle Bac...

Regular strengthening (core strengthening and resistance or weight training), flexibility (stretching) and aerobic exercise will improve your overall fitness and decrease the likelihood of back injury.  Factors that may contribute to low back pain at work include poor posture while sitting or standing, sitting or standing for long periods of time, driving long distances, improper lifting techniques, frequent lifting, or lifting excessively heavy loads. Low back pain is as common among clerical workers who sit for prolonged periods as in people whose jobs require heavy lifting