The underneath portions of your arms are your tricep muscles. It is called the tricep muscle because there are three "heads" to the muscle. This muscle involves the extension of your elbow, so pushing yourself up and away from the arms of the chair you're sitting on will work your tricep muscles. There are many exercises to perform to strengthen your tricep muscles, but start with the basics.
Tricep Push-Down
A tricep push-down is an exercise that is on a cable-pulley system that can be found at most gyms. There will be a small bar or a rope that you can attach to the cable-pulley. Raise the cable so the attachment of the bar/rope and the cable are at about eye level, and the starting position of your hands will be at about the top of your chest. Face the cable and pull the bar/rope downward, while keeping your elbows close to the side of your torso, to full elbow extension. Return upward until the attachment point is about eye level once more.
Push-Ups
Push-ups work your triceps as well as your chest, and the same goes for the bench press too. To perform a push-up, place your hands on the ground by the side of your body so that your elbows are pointing behind you at roughly a 45-degree angle. Keep your back, shoulders and hips in line as you drop your chest between your hands. The goal is to touch the chest to, or close to, the ground, then return to the starting position. Always have your fingers facing forward.
If your strength doesn't support your weight yet, place your knees on the ground and slightly back so your chest can drop comfortably between your hands still. To modify the intensity placed on the triceps, simply bring your hands closer together underneath your chest.
Dips
A dip is primarily targeting the tricep muscles, and somewhat your pectoral muscles. You will need two parallel bars of the same height for this exercise. Many gyms have a place for dip bars, and some supply assisted dip machines. Grip around the bars so that your knuckles are facing out, and extend the elbows. Then take your feet off the ground. You are now in a structural lockout supporting your body weight if using an unassisted machine. Begin to bend your elbows--without flaring them outward--to lower yourself. Lower yourself until the elbow joint is at a 90-degree angle, then press upward. Try to keep your elbows close to your body throughout.
Sets, Repetitions and Rest Optimal for Strength Training
According to the National Strength and Conditioning Association, there are several sets of reps you should complete to achieve optimal strength results. There is also a recommended rest period in between sets that will benefit strength training. You should attempt to complete 2 to 6 sets, of 6 to 10 reps, for strength training. There is a drop-off of significant gains made after completing three sets of an exercise, so 2 to 3 sets is best. The rest period for strength training should be ideally 2 to 5 minutes in between sets.
References
- "ACSM's Guidelines for Exercise Testing and Prescription (eighth edition)"; American College of Sports Medicine; 2009
- "Essentials of Strength Training and Conditioning"; Thomas Baechle and Roger W. Earle; 2008



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