People lift weights for a variety of reasons, most commonly to improve their body composition, develop lean body mass and lose body fat. Working your muscles against resistance can help you reach all of these goals. Some people also use weight training as a vehicle to preserve bone density and lower their risk for osteoporosis. Lifting heavy weights places enough stress on your bones to stimulate the production of new bone. Another common goal of weight training is to become stronger. Stronger muscles increase your ability to do things like lift heavy objects, move furniture and do other everyday activities without injury. In that way, it improves your functional strength.
The Importance of Overload
To develop greater strength, you have to subject your muscles to more stress than they’re accustomed to. This stress comes in the form of overload. When you first begin to weight train, your muscle strength will increase initially even if you use a relatively light load, as low as 50-60% of your one-rep max. One-rep max is the amount of weight you can lift one-time using good form. Fitness trainers use the percentage of one-rep max to determine how much weight a client should lift to achieve their goals.
As you progress in your training, you need to lift at a greater percentage of your one-rep max to further increase muscle strength. Research shows an experienced lifter must lift a minimum of 80% of their one-rep max to make improvements in muscle strength. You know you’ve selected the right weight if you can lift it no more than 3 to 5 times using good form. When strength building is your primary goal, longer rest periods of 2 to 3 minutes give your muscles enough time to recover between sets so you can lift heavy again. Shorter recovery times limit the amount of weight you can lift on the next set. With strength building, lifting heavy (80 to 90% of one-rep max) is optimal.
Strength versus Hypertrophy Protocols: How Do They Differ?
If your goal is to maximize muscle growth or hypertrophy, moderate resistance (70 to 80% of one-rep max) and higher reps (8 to 12) increases time under tension and maximizes metabolic stress. Both of these factors are important for muscle growth. Shorter rest periods (1 to 2 minutes between sets) also create more metabolic stress than longer periods of rest to maximize muscle growth.
What about the number of sets? Although one study showed similar strength gains with a single set versus multiple sets, most research shows 3 or more sets are best for maximizing strength once you’re no longer a weight training novice. If you’re just starting out, one set of each exercise will likely result in an increase in strength but as you advance, you’ll need multiple sets to continue to improve muscle strength.
In one study involving post-menopausal women, those who did multiple sets had strength gains of between 3.5 and 5%. The group who did a single set actually showed a minor decline in strength of 1 to 2% in strength.
There is some overlap between strength and muscle growth. Your muscles will become stronger as you gain lean muscle tissue through hypertrophy training, but the lighter load and greater number of reps that are best for muscle hypertrophy won’t MAXIMIZE strength development. When you’re training primarily for strength and not hypertrophy, lift heavy for a shorter number of reps (3 to 5) and give your muscles time to fully recover between sets.
You might think the only way your muscles become stronger is to become bigger. It’s true that with overload muscle fibers produce more contractile proteins (actin and myosin) so they can lift against greater force but this takes time. Here’s the surprising part. You can actually develop an increase in muscle strength during the first week or two of training. Most of this “early response” to training comes from neural adaptations, not muscle fiber changes. Neural adaptation means your brain gets better at recruiting motor units and synchronizing them to work together as a unit. This allows you to lift a heavier load without a change in muscle size. You’ll notice a slight gain in strength before you’ll see a change in the size of your muscles.
Should You Vary the Load To Get Stronger?
It might seem that lifting as heavy as possible and using fewer reps on a consistent basis would maximize strength gains. Not necessarily. Research shows varying the volume and load of your weight training workouts maximizes muscle strength. Lifting at 80 to 90% of your one-rep max every time you work out may lead to overtraining, injury and a reduction in performance. That’s why periodizing your workouts by manipulating the volume and intensity of your training sessions can help maximize gains while still letting your muscles recover adequately. It also reduces boredom and helps you avoid a plateau.
How Much Strength Can You Gain?
The amount of strength you can develop from a strength-training program varies with age, sex, and genetics. Nutrition is a factor too. You’ll be limited in how much progress you can make if you don’t consume enough protein or restrict calories too much. The same goes for muscle growth. You need to take in more calories than you burn off to optimally build strength and size. If you choose foods high in protein, healthy fats and fiber-rich carbs from whole food sources, it creates a metabolic environment ripe for building lean body mass rather than fat.
The Bottom Line?
If your primary objective is to build strength, not mass, stick with low reps, 3 to 5, so you can maximize the amount of weight you lift. A portion of your strength gains will come from increased neurological efficiency not an increase in muscle size. To build muscle size, 8 to 12 reps and three or more sets of each exercise is best. The greater volume maximizes metabolic stress and release of growth hormone and testosterone for muscle growth and enlargement.
Medscape.com. “Progression Models in Resistance Training for Healthy Adults” (2010)
J Strength Cond Res.15(3):284-9. (2001)
The University of New Mexico. “The Mystery of Skeletal Muscle Hypertrophy”
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