Parents: How Heavy Should Your Child Lift?

(And Why It Matters for ACL Injury Prevention at Stadium Performance)

Supertraining Bible

Years ago, when I first read Supertraining by Siff and Verkhoshansky, I remember thinking two things:

1. This book is old as dirt.

2. It explains more about force production than most modern “high-performance” manuals combined.

Not all new shiny books are the best books. Sometimes the old ones were written before marketing departments got involved. That book is what got me thinking differently about how weight actually influences force output — and why that matters for your child’s ACL.

Because here’s the uncomfortable truth:

Strong doesn’t automatically mean protected.

But underprepared definitely means exposed.

Here’s your Joe-ism to get you warmed up:

If your child isn’t trained to produce force, they’ll be forced to absorb it.

Weight and Force: What the Research Actually Shows

One of the tables in Supertraining looks at how different percentages of maximal strength influence peak force production.

Here’s the simplified version:

When resistance increased:

• 80% of max strength produced ~94% of peak force

• 60% produced ~83%

• 40% produced ~64%

• 20% produced less than half

  
  

Translation for parents:

When your child lifts moderately heavy loads (around 80%), they are producing nearly all of their available force potential. That is not ego lifting. That is physiology. And force production is directly tied to tissue tolerance — which is directly tied to ACL injury risk.

Why This Matters for ACL Injuries

Most ACL injuries in youth sports are non-contact.

They happen when your child:

• Decelerates

• Cuts

• Lands from a jump

• Changes direction at speed

Those movements require high force production in a very short time. If your child has never been exposed to producing high levels of force under controlled conditions, competition becomes the first exposure. That is not a training strategy.

At Stadium Performance, our ACL injury prevention training is built around preparing your child’s body to tolerate force before asking them to express speed. Because speed without force capacity is just instability in motion.

The Problem With “Just Go Light”

Some parents hear that heavy lifting is dangerous. Others think their child just needs “movement training.” Let’s clarify something.

Light loads (20–40% of max strength) absolutely have a place. They help with:

• Coordination

• Speed development

• Motor learning

• Power expression

But lighter loads produce significantly less peak force. And when peak force stimulus drops, so does structural adaptation. That means tendons don’t stiffen as effectively.

That means muscles don’t recruit maximally. That means joints aren’t exposed to the levels of force they will experience during sport.

Then everyone is surprised when an ACL injury happens during a routine cut.

It shouldn’t be surprising. It’s math.

The Strength Deficit Problem

One of the more important ideas from Supertraining is something called the strength deficit. As load decreases, the relationship between maximal strength and force output weakens.

In simple terms:

If your child lacks overall strength, they cannot produce sufficient force even at moderate loads.

This shows up as:

• Knees collapsing inward

• Poor deceleration mechanics

• Fatigue-related instability

• Sloppy landings

Parents often assume this is a “coordination issue.” More often, it is a force capacity issue. And cone drills will not fix a force deficit.

So How Heavy Should Your Child Lift?

For most middle school and high school athletes:

Training consistently in the 70–85% range of their maximal strength is extremely effective.

That range:

• Produces high levels of peak force

• Builds tissue resilience

• Improves neuromuscular recruitment

• Supports ACL injury prevention

• Avoids excessive joint stress from constant maximal testing

Notice what I did not say.

I did not say your child should max out every week. There is a difference between training heavy and testing maximal strength constantly. One builds durability.

The other builds unnecessary risk.

What We Do at Stadium Performance

Our injury prevention training at Stadium Performance is not about chasing big numbers for bragging rights. It is about building usable force.

We monitor:

• Relative strength

• Eccentric control

• Deceleration mechanics

• Force production across different loads

  
  

Because ACL injury prevention is not a warm-up program.

It is a force capacity program.

If your child can tolerate high levels of force in the weight room, they are far less likely to exceed their limits during a game.

That’s not hype.

That’s adaptation.

Parents, Here’s the Real Question

Would you rather your child experience high force under supervision…

Or for the first time during a playoff game? The body adapts to what it experiences.

If it never experiences sufficient load, it never builds sufficient resilience. Avoiding force does not prevent ACL injuries. Preparing for force does.

Glossary: Words I Probably Shouldn’t Assume You Know

1. Peak Force: The highest amount of force your child can produce during a movement.

2. Maximal Strength: The greatest amount of force your child can produce in one effort.

3. Relative Strength: Strength in relation to bodyweight.

4. Tissue Tolerance: How much stress muscles, tendons, and ligaments can handle before injury risk increases.

5. Neuromuscular Recruitment: How effectively the nervous system activates muscle fibers.

6. Tendon Stiffness: A tendon’s ability to resist excessive stretch and transmit force efficiently.

7. Strength Deficit: The gap between your child’s maximal strength and the force they produce at lighter loads.

8. Deceleration: The ability to slow down safely and under control.

9. Eccentric Control: Muscle control while lengthening under load (like lowering into a squat).

10. Force Capacity: The maximum force your child can produce and tolerate safely.

You don’t reduce ACL injury risk by avoiding heavy training.

You reduce ACL injury risk by preparing your child for the forces their sport demands.