Heigh Weight vs. Low Weight
The million dollar question when it comes to weight training is "how much do I lift and how many reps should I do?" Without going into a full lesson on training program design, we've put together some general information to help answer these questions.
The reason we exercise is to change our bodies. From cosmetic changes like losing fat and building muscle to health-related changes like lower cholesterol, the amount of weight a person lifts will be different. Additionally, ones exercise history and how he/she responds to exercise are other factors to keep in mind.
What we're trying to say is... there is no cut and dry answer that applies to everyone.
Typically, higher weights have been associated with building muscle and lower weights have been associated with fat loss. There are drawbacks to this type of generalization such as plateaus and over training. Be sure to keep your program fresh so your body doesn't get bored. Also make sure your starting weight is well within your control, you can always add more later.
Remember that the term “fatigue” is different from “failure.” In this context, “fatigue” means a slight loss of form and control. The term “failure” means a complete exhaustion of the muscles and/or brain and a breakdown of form and control. You should only push to “failure” in certain circumstances of training which won’t be discussed here. Remember to play safe!
General Fitness Improvement
(includes muscular endurance, slight muscle gain, health related goals and body fat loss) Lift enough weight to reach fatigue at between 12-25 reps
Lift enough weight to reach fatigue between 6-15 reps
Lift enough weight to reach fatigue between 1-5 reps (for experienced lifters)
Here’s where it gets crazy. Because personal training program design is an art and a science all on its own, you could use the right strategy and still not get the goals you're striving for. It's important to keep changing your program every couple weeks to avoid plateaus and prevent over training. The bottom line... you've got to keep your body guessing to keep moving forward.
For more information on what weight/reps/exercises/etc to select and how it all works for your goal, seek out a qualified fitness professional.