This is probably the most frequently asked question I heard when I was a gym rat. The answer depends on your objective. If you want to gain bulk, lift weight at your absolute strength limit and perform eight to ten reps. If you want to tone the muscles you already have, lift a lighter weight but perform 12 to 16 reps.The important question isn't really "How much weight should I lift?" It's how much can I lift with control and good form.
The worst mistake you can make is lifting an amount of weight that forces you to contort your body. If your neck, shoulders, arms, back -- especially the back -- or legs are out of alignment when you lift, the odds are you are going to suffer a catastrophic injury that could put you out of lifting for months, or worse forever, which kind of defeats the purpose of lifting.
Pick a weight that challenges your muscles when you're exercising with proper form. It will ALWAYS be less than the amount that you can jerk up in a contorted shape, but it will contribute more to your overall strength, tone and fitness in the long-run than attacking a pile of weights like a maniac.
We all know people who took the maniac approach, and not many of them are still fit in their thirties and forties, nor can they participate in the full range of sports they used to enjoy. The people I know who went the maniac route usually suffer chronic neck, shoulder and back pain. What a reward for all their hard work.
When you approach dumbbells or load a bar, increase the weight in the smallest increments possible until you reach the maximum load you can handle with good form. If later in the workout, you're starting to lose good form, lighten the load a little. As Tony Horton says in the P90X workout series: "Don't be a hero." He's right.
P90x is a great way to learn the proper way to perform a wide range of exercises. My review of P90x on RuggedReviews.com covers the DVD set and includes links to reviews of equipment you'll need to take on the challenge.
Most of all, when you're engaging in any fitness regimen, focus on your ultimate objective, which should be a healthy, vibrant and fully mobile body.
Consult your physician before you undertake any exercise program.
