The plank exercise has become the gold standard for core workouts (abdominal muscle and muscles that surround the spine and the back). ACE (American Council on Exercise) conducted a study in which, of the 10 best abdominal exercises, the plank ranked number 10. You don't need any equipment, so it fits right into your budget.
Most of my clients and boot-camp enthusiasts incorporate planks in their workout. I realized that everyone can do a plank, from seniors to women who are expecting.
You just have to find the best plank position for your fitness level. Planks strengthen your abdominal wall; thus, providing support for your back. Anyone experiencing back pain due to weak abdominal muscle should definitely consider planks as an exercise for your rehab program.
If you never performed a plank, start withholding the static plank position for 5 to 10 seconds and gradually build up to 45 seconds to a full minute. After you have conquered basic planks, move up to the next level or to a different plank for advanced exercisers. If your lower back aches while doing the plank, you are pushing yourself too hard; drop down to a lower level.
Find your plank level below:
Beginner -- upright position 1: This is designed for those who have bad knees or can't get on the floor. Standing-up, make sure your elbows are aligned with your shoulders, and keep your body straight from head to heel. Concentrate and press your abdominals towards your spine; don't hold your breath. You should be able to hold this for a minute or longer. Once you conquer this level, move to intermediate upright position 2.
*This is a great starting position for seniors.