Strength, Size and Endurance Are Different Goals

Quick Intro

Strength is how much force you can produce. Size is how much muscle you have. Endurance is how long you can keep working. They overlap, but each is built a little differently: strength needs practice with heavy loads, size needs plenty of hard sets in almost any weight range, and endurance needs time and repetition. Knowing which one you are after helps you train for it.

This article explains each goal, how it is trained and where the common rules of thumb go wrong.

Three Different Goals

Strength is the ability to produce force: lifting a heavy box, pushing a stuck car, getting up from a deep chair. It depends on muscle size but also heavily on the nervous system’s skill at using that muscle.

Size means muscle growth, called hypertrophy. Larger muscles can produce more force, but size is not the same as strength. Two people with similar muscles can differ a lot in how strong they are.

Muscular endurance is the ability to keep a muscle working for a long time or for many repetitions: carrying shopping a long way, holding a position, doing many squats in a row. Overall stamina, the heart and lungs’ side of endurance, is a separate quality trained by aerobic exercise.

The Old Rule and What Is Wrong With It

A common rule says: heavy weights and few repetitions for strength, moderate weights for size and light weights with many repetitions for endurance. This rule is only partly right.

For size, load matters less than effort. Research has found that muscle grows across a wide range of loads, from light to heavy, as long as each set is taken close to the point where another good repetition is not possible. Light weights for many repetitions and heavier weights for fewer can build similar muscle.
For strength, heavy loads do have an edge. Heavier loads work best for maximal strength, because lifting heavy is itself a skill that improves with practice.
For endurance, repetition and time matter. Doing more repetitions and longer efforts builds the ability to keep going.

So the rule gets strength and endurance broadly right, but it is wrong to say only moderate weights build size.

How to Train for Each

For strength

Practise the movements you want to be strong in, such as a squat, deadlift, press or row.
Use heavier loads for fewer repetitions, with full rest between sets so each set is done well.
Increase the load gradually over weeks.
Exercises such as the Barbell Back Squat, Barbell Deadlift and Dumbbell Bench Press suit this, but bodyweight versions such as single-leg squats also build strength.

For size

Do enough hard sets for each muscle across the week. More weekly sets bring more growth, up to a point.
Use any load you like, as long as sets are hard. Many people find moderate loads most practical.
Train each muscle at least twice a week.
Give muscles time and food to recover. Nutrition is outside the scope of this article.

For muscular endurance

Do higher repetitions or longer holds, such as a long Plank or many Bodyweight Squats.
Use shorter rests between sets.
Circuits that move from one exercise to another work well.

How the Goals Overlap

These goals are not entirely separate. Strength training builds some size, size training builds some strength and both improve endurance for beginners. Most people training for general fitness get a useful mix of all three from a sensible routine.

The differences matter more as you get more experienced and want to push one goal further. A powerlifter, a bodybuilder and a rower all train very differently because their goals differ.

Choosing Your Focus

Ask what you want your training to do:

Lift heavy things more easily? Focus on strength.
Change how your muscles look? Focus on size. If you want to avoid size, will lifting weights make me bulky? explains how to limit it.
Keep going longer in daily tasks or sport? Focus on endurance.
General fitness and health? A mix, with moderate loads, some heavier work and some higher-repetition work, covers all three.

FAQ

Can I train for strength and size at the same time?

Yes. Most programmes combine both, with some heavier sets and plenty of hard sets overall.

Do light weights build muscle?

Yes, if sets are taken close to the point where another good repetition is not possible.

Does endurance training make you lose strength?

For most people doing moderate amounts, no. Very large amounts of endurance training can slightly blunt strength gains, mostly in athletes.

How many repetitions should I do?

It depends on your goal, but for general fitness a range of about 6 to 15 repetitions per set, with the last few hard, works well.