Start slowly, and add intensity and increase workout time gradually. Seniors benefit from low impact aerobic activities which eases the wear and tear of older joints. Good options include swimming, aqua aero-bics, walking, and stationary bicycling. Although any aerobic activity will improve muscle tone, strength training is one of the best exercise choices for older individuals. Purge your mind of images of overdeveloped body builders.
Weight training is for everyone.
Research is showing more and more evidence that resistance training is extremely beneficial to older individuals in terms of injury prevention, reduction in body fat, increased metabolism, stronger bones and lowered risk of developing osteoporosis, improved confidence and independence, and improved self esteem and appearance. Few activities provide such visible positive reinforcement as strength training. Be sure to warm up before and cool down after your workout. Your warm-up can be 10 to 15 minutes at a slower pace of the activity you've chosen. And a cool down should always include a well-planned stretching routine.