Why is increasing strength relative to muscle size ideal for athletes?

Chris Beardsley
Sep 6, 2017 · 5 min read

Many athletes today are strong, fast, and very muscular.

So it sounds strange to suggest that the single *best* way to improve athletic performance is to improve strength relative to size. And yet, it is almost certainly true.

Let me start by giving a simple example.

Consider a team sports athlete weighing 192lbs at 12% body fat percentage (169lbs of fat-free mass) who undertakes a strength training routine in the off-season, geared towards gaining muscle. They hope that this increase in muscle size will cause strength gains that transfer to athletic movements like jumping and sprinting.

If they do increase fat-free mass by 5lbs (and do so without increasing fat mass) then bodyweight would similarly increase by 5lbs. By doing this, the athlete will actually *reduce* their body fat percentage slightly.

In contrast, if they increase fat-free mass along with a small increase in fat mass such that they remain at approximately the same body fat percentage, bodyweight would increase by 6lbs.

Whether fat gain occurs or not, there is an increase in bodyweight.

For the athlete to remain the same bodyweight while increasing fat-free mass, body fat must reduce, and this causes a large reduction in body fat percentage.

This is possible but *not* typical for athletes.

If our team sports athlete did achieve this, they would reduce body fat percentage from 12.0% down to 9.4%, which would be a rough ride for any athlete who is also doing a lot of high-intensity running, drills, and other activities.

After a more typical result, in which bodyweight is increased after strength training aimed at increasing muscle size, sprinting and jumping ability may not always improve by as much as you might hope, because of Newton’s laws.

So if we can get the *same* strength gains without the increase in bodyweight, then we will not have this problem.


What is the alternative?

An alternative approach for athletes is to improve strength in ways that do not involve increasing muscle size.

This is called increasing strength relative to muscle size, or increasing strength relative to bodyweight. Some strength coaches do actually call it increasing *relative* strength.

Yet, the ways in which relative strength increases depend on the context in which force is being expressed. And some contexts are very relevant to sports performance, while others are not.

Two good examples of contexts in which strength is expressed in ways that are very relevant to sport are (1) high-velocity strength, and (2) strength in certain ranges of motion.

Let’s look at each of those.


High-velocity strength improves after training with light loads and maximal bar speeds.

This type of training is most commonly performed by athletes as either ballistic strength training (jump squats and kettlebell swings) or plyometrics (jumping and bounding). These training methods increase high-velocity strength not through gains in muscle size, but by other mechanisms.

In fact, high-velocity strength improves after training with light loads and maximal bar speeds primarily through changes in the central nervous system. Such changes include increases in early phase neural drive, reductions in the force being produced by an opposing (antagonist) muscle, and improvements in velocity-specific coordination.

In addition to changes in the central nervous system, there are also changes after training with light loads and maximal bar speeds that happen inside the muscle. Such changes include a greater retention of type IIX muscle fibers, and an increase in single fiber contraction velocity.

These adaptations are all very important, because high-velocity strength is very transferable to almost all sporting movements, including sprinting and jumping.


Strength in certain ranges of motion also improves after certain types of strength training, by a range of mechanisms. Sometimes, those mechanisms can increase strength without increasing muscle size.

Partial ranges of motion of the lower body are very applicable to sporting movement. Athletes rarely squat all the way down before jumping, and sprinting involves force being produced while being nearly upright.

Although partial range of motion strength can be improved by an increase in muscle size, this is actually *not* how it is happens in anyone with a few years of strength training experience.

Indeed, partial range of motion strength improves after training primarily through increases in neural drive that are specific to the joint angles that correspond to short muscle lengths, and not because of any substantial increase in muscle size.

We can develop partial range of motion strength for the lower body very simply by using what are called “partial” strength training exercises (half squats and quarter squats). Although it is not well-known, partial squats do seem to be better than full squats for improving jumping and sprinting performance in athletes.


Why not have both?

There is no reason that we cannot build training programs that provide *some* stimulus for increasing muscle size, while also developing the types of strength that transfer effectively to sport.

Yet, it makes sense to prioritize certain specific gains in strength that can be achieved without increasing muscle size, as these can produce far larger gains in *relative* strength. For the same increase in strength, athletic performance increases to a greater extent, because bodyweight does not change.

This is particularly important, when we consider that the types of strength training that are *optimal* for increasing specific types of strength that transfer to athletic performance are not the same as the types of strength training that are *best* for increasing muscle size. Indeed, neither high-velocity strength training nor partial range of motion strength training are useful for building muscle mass.

Ultimately, this means that when training athletes, we do need to make a hard choice about whether to prioritize specific strength gains *or* muscle size in our programming.

But I think it is fairly clear which option we need to choose.


What is the takeaway?

It sounds strange, but the most effective way to improve athletic ability is to increase strength relative to size, without adding muscle mass and therefore bodyweight.

Some types of strength, such as force at high velocities and force in partial ranges of motion, transfer *very well* to athletic movements, and can also be increased without gains in muscle size. Prioritizing these (and other) specific types of strength can enable athletes to achieve larger gains in *relative* strength, and thereby also larger improvements in athletic performance.

Chris Beardsley

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