Duration is dependent on the intensity of the exercise. Resistance training is equally as important as aerobic activity and should be an integral component of your fitness program. Resistance training is important for enhancing muscular strength, muscular endurance, maintaining fat-free mass, and for maintaining bone mineral density, to prevent the onset of osteoporosis. A minimum of 2 days per week, up to 3 or 4, with at least 1 day in between each workout. Similar to aerobic exercise, resistance training needs to start out at a low intensity when beginning the program and can gradually increase as your body adapts to the new work load.
Technique is very important to prevent injuries and ensure efficient movements.
After a period of about three weeks to a month, you should be performing at an intensity high enough to stimulate the muscles to grow stronger. This intensity is extremely variable for each person. However, most people are able to perform at a relatively high intensity without fear of injury, as long as they have progressed gradually. When beginning a resistance training program, be sure to have a certified strength and conditioning specialist or a certified personal trainer go through the machines or exercises with you and help you set the proper weights. Be patient and do not increase your weights too quickly, for this may lead to injury.