Ideal Percentage of Weight for a Seated Chest Press

Remove the pin from the chest press machine's weight plates, so that no weight is on the cables or levers.

Sit on the seat of the chest press machine and test its height. Whether you're using the lever chest press machine, which has long straight handles stretching up from near your thighs, or the cable chest press machine with cables and handles coming from behind you, the handles should be about chest-high when held in the starting position. Grab the handles and press them forward far enough so that your hands are to the sides of your chest. If your hands are lower or higher than about nipple height, stand up, remove the pin from the seat of the machine, raise or lower it to the correct height and then replace the pin.

Place the pin under the first weight plate on the machine, which will start you out with the lightest weight possible on the machine. Depending on the machine, this may be about 10 pounds.

Sit on the seat of the machine, grab the handles and sit up straight to engage the muscles of your core.

Press the handles forward as far as you can go. If the action feels extremely easy, it's probably too light a weight to make your muscles work to fatigue. When that's the case, remove the pin and place it under the second or third weight plate, which may represent 20 and 30 pounds, respectively. If the original weight seemed fairly tough to press forward, continue with that 10-pound weight.

Press the handles forward and then allow them to slowly move back to the starting position. Repeat this motion 12 to 15 times. If you've chosen the right amount of weight, the last few repetitions will be very difficult. According to Dr. Laskowski, a single set to fatigue is sufficient for most exercisers.

Write "Seated Chest Press" in your workout notebook and then note the date and the amount of weight you lifted. A record of your performance can give you a clear view of your progress and keep you motivated. According to the U.S. Department of Health & Human Services' 2008 Physical Activity Guidelines for Americans, performing all-over strength training two days a week, using all major muscle groups, is recommended for fitness.

Continue lifting that same amount of weight -- provided it was enough to push your muscles to fatigue -- for about two weeks. Every two to three weeks, add about 5 to 10 percent to the amount you're lifting to continue working your muscles to fatigue as you get stronger. For some chest press machines, this might require using smaller supplemental weight plates, such as a 2- or 5-pound plate, that you can stack on top of the existing weight plates.