Here’s the short answer: You should always lift the maximum amount of weight that will allow you to complete all of your reps in all of your sets of a given exercise while maintaining proper form. If you aren’t doing this — by lifting too light or too heavy of a load — you’re shortchanging your potential results and possibly setting yourself up for injury.
Strength Training 101: What Exactly Does Lifting Weights Do For Your Body?
The goal of strength training is, of course, to grow stronger. (If you’re looking to lose weight, it helps, too.)
To grow stronger, you need to challenge your muscles. For simplicity’s sake, we’ll define “challenge” as repeatedly contracting and lengthening them under load until they cry for mercy.
When you do this, you cause microscopic tears in your muscle fibers that must be repaired. And during the repair process, your body not only fixes the damage, but the muscle grows stronger and is able to withstand a greater load.
The result is muscle growth — your muscles literally take on a new and greater dimension, and as they become larger, they have the means to contract with greater force and intensity.
And the more you challenge your muscles, the better your nervous system becomes at recruiting and activating them. Since neural adaptations occur faster than muscular ones, they are what account for the rapid increases in strength that typically occur at the beginning of a workout program.
In other words, first you become better at activating the muscle you already have, and as you build more of it, you become increasingly adept at activating that as well.
Strength vs Endurance: How Many Reps Should I Do?
Most weight training exercises target a certain number of repetitions for each set. (When you hear a trainer say “Give me three sets of ten reps,” this means one movement performed ten times — that’s one set — then ten times again, then ten times again.)
As a general rule, strength gains are achieved when you program fewer reps (six or less) with higher loads, while muscular endurance improvements are achieved via higher reps (15 or more) with lighter loads.
Around six to 12 reps per set is the sweet spot for hypertrophy, also known as muscle growth.
Targeting Hypertrophy: How to Train the “Sweet Spot” to Grow Muscle
Start with a weight that will allow you to barely finish six reps per set. As you become stronger, you’ll progress to the higher end of that range — 12 reps per set.
When that happens, increase your weight just enough that you can only execute six reps per set with this higher weight, while maintaining proper form. As you become stronger, you’ll progress toward 12 reps again. See what’s happening here?
Repeat this process for as long as this specific exercise is part of your workout.
Why Targeting Hypertrophy Should Be Your Goal, Even If You Want to Lose Weight
Whether your goal is to lose weight or to gain weight, focusing on hypertrophy at the beginning of your workout program will change your metabolism, which is the main objective in body transformation.
Once your metabolism gets moving, how you structure your diet and exercise will determine whether you gain or lose weight, and how quickly that change occurs.
So even if your goal is to lose weight, you should push hypertrophy workouts as hard as you can. Never take it easy, and never fall back on that silly rationale you’ll hear people say at the gym: “I don’t want to gain too much muscle, I just want to lose fat.”
Adding muscle accelerates fat loss, which is where the saying “muscle burns fat” comes from.
Furthermore, gaining bulk is a very difficult thing to do. Most professional bodybuilders would sell their souls for a few additional inches of muscle mass, and would quickly correct anyone who thought bulking could happen by accident.
(Women especially don’t have to worry about accidentally turning into Lou Ferrigno — generally speaking, most women won’t bulk up as much as men, and for anyone to gain muscle mass, you have to plan your eating and training accordingly.)
Why Targeting Hypertrophy Shouldn’t Be Your Only Goal
Focusing on hypertrophy will target your type II muscle fibers, which are the larger and stronger of the two kinds found in your body. Type II fibers also have the greatest growth potential.
You also have type I fibers, which aren’t as powerful as type II fibers but have a higher resistance to fatigue. If you’re a distance runner or a cyclist, these are the fibers upon which you rely — and if you’re a weightlifter, these are the fibers you probably ignore, and you likely do so for several reasons.
First and foremost, you probably believe targeting them is a waste of time. Your focus is strength, after all, so why would you nurture the same endurance-oriented fibers as a marathoner? More importantly, you’ve probably also been told that type I fibers have no growth potential — a belief that research is proving false.
Although not as great as type II fibers, type I fibers still have “a substantial propensity for hypertrophy,” according to a study in the Strength and Conditioning Journal.
And if you want to maximize muscle growth, you can’t ignore them.
While the most effective body transformation programs focus on hypertrophy, they don’t ignore endurance. In practice, that means rather than focusing on one “sweet spot” program to solely target hypertrophy, you should program a range of repetitions (low, medium, and high) to target those type I fibers as well.
A Word about Lifting to Failure, and Why You Shouldn’t Do That
You might hear some trainers say, “Failure is not an option, it’s the only option.” What they mean is that if you aren’t lifting enough to totally break you down on the last rep of your last set of a given exercise, you’re not lifting enough.
Ignore that advice. Lifting to absolute failure almost guarantees that your form will fall apart during the last couple of reps, which increases your risk of injury.
(And there’s little evidence that struggling through one or two sloppy final reps will produce any additional growth stimulus anyway.)
Here’s a better plan: Lift to technical failure — the point at which your form falters — and no further. Not only will you reduce your risk of injury, but you’ll recover faster. And the faster you can recover, the faster you can keep progressing toward your goal.