It makes a huge difference. Here is a great article that covers a lot of the basics in a very accessible / narrative way: http://archive.mensjournal.com/every

It makes a huge difference. Here is a great article that covers a lot of the basics in a very accessible / narrative way: http://archive.mensjournal.com/everything-you-know-about-fitness-is-a-lie http://archive.mensjournal.com/everything-you-know-about-fit... Basically: - Low Reps / Set = Strength / Power - Med Reps / Set = Mass - High Reps / Set = Endurance / "tone" See these two charts for a little more detail: - http://i.imgur.com/vZ7pU.jpg http://i.imgur.com/vZ7pU.jpg - http://i.imgur.com/4NVGh.jpg http://i.imgur.com/4NVGh.jpg FTA: "...it all starts with understanding the four basic muscular aptitudes: strength, power, muscle mass, and muscular endurance. Strength means how much you can lift once, and it’s the backbone of every sport on Earth, from the crouch-holding power of a skier to the one-finger pull-up of a climber. Power is a more slippery term that means “speed strength,” or how much you can lift very, very quickly, and it gives you the explosive paddling speed to catch a big wave or the pedaling burst to fire your mountain bike up a grade. Muscle mass can be a liability in sports like climbing, where it’s all about strength-to-weight ratio, but mass helps enormously with games like rugby and football, and it can support strength and power — not to mention make you look better in a T-shirt. Muscular endurance means how many times you can lift a given weight in a row without stopping, and it’s the essence of running, swimming, and even a kayaker’s long-haul paddling. As for your training sessions themselves, the number one thing to remember is that each of the Fundamental Four responds to a different number of repetitions per set. Lift a weight so heavy you can lift it only once, you’re building strength (and, oddly, not much mass); lift a weight you can move six to 12 times, you’re building mass (and, oddly, a little less pure strength); ease up to a weight you can lift 50 times, and you’re working muscular endurance (which is great for endurance sports but tends to undermine the first three, shrinking your strength, power, and muscle size)."