The new rules of lifting: What ACSM actually changed about strength, hypertrophy, power, and longevity

The science didn’t flip upside down. But the way we apply it just got a lot smarter.

For a long time, strength training followed a fairly predictable structure. You trained a few times per week, followed a set number of exercises, worked within specific rep ranges, and if you really wanted results, you pushed yourself to the limit—sometimes all the way to failure.

That system worked. It built strength, built muscle, and gave people a clear plan to follow. But like most structured systems, it also came with limitations. It didn’t leave much room for adjustment. It didn’t account for differences in recovery, experience, or lifestyle. And for many people, it created the belief that there was only one “right” way to train.

What’s important to understand is that this is the first major update to these guidelines since 2009. That’s over 15 years of new research.

And the amount of new information is massive.

As the updated paper points out, a simple PubMed search for “resistance training” yields over 30,000 new results since 2009, highlighting just how much the field has evolved and why an updated, more evidence-based framework was needed.

The updated ACSM guidelines don’t replace the old system. They expand it.

The old model gave you structure.
The new model gives you options.

TL;DR

Strength: what actually builds it—and why it matters in real life

If there’s one place the updated guidelines are the most clear, it’s strength—not just that it matters, but how it’s best developed. And interestingly, the answer isn’t complicated. It’s focused.

Strength is built by consistently producing force—under control, through a full range of motion.

For years, people have chased strength through variation, intensity techniques, or constantly changing workouts. But the updated guidelines reinforce something more foundational: strength responds best to load, repetition, and position.

To build strength, you need to challenge your ability to produce force. That typically means working with heavier loads—around 80% of your one-rep max or higher. Not every set needs to live there, but consistently exposing your body to that level of demand is what drives adaptation.

If you want to get stronger, your body has to feel what “heavy” actually is.

Just as important as load is where that strength is developed. Strength isn’t just about lifting the weight—it’s about where you’re strong. In real life, strength rarely shows up in perfect positions.

You need strength in the bottom positions—the deeper part of a squat, the stretched position of a chest press, the lengthened position of a hinge. That’s where your body is most vulnerable, and where strength matters most.

If you avoid the bottom range, you avoid building strength where you need it most.

Training through a full range of motion builds not just strength, but mobility, control, and stability under load. Think about squatting down to pick up a child or a heavy box off the floor. If you do not have strength in that deeper position, your body will usually find another way—rounding the back, shifting weight, or compensating through another joint. That is often where problems begin.

The same idea applies to upper-body training. Building strength through the bottom of a chest press trains you to control the weight in the stretched position while also helping maintain length through the chest and shoulders. Over time, that can support better posture and reduce the tendency toward the rounded-shoulder position so many people drift into.

Full range of motion isn’t just about performance.
It’s about moving well for the rest of your life.

The guidelines also reinforce that you don’t need extreme volume to get stronger. Strength improves with about 2–3 sets per exercise, at least 2 sessions per week, and placing your most important strength work earlier in the workout.

Failure vs. reps in reserve: where science meets coaching

For years, people believed that if you weren’t training to failure, you weren’t training hard enough. But the updated evidence tells a different story.

You don’t need to take every set to absolute failure to get stronger.

Pushing every set to the point where you have zero reps left doesn’t consistently improve strength or muscle growth. Instead, training close to failure—while maintaining control and good mechanics—appears to be just as effective.

From a coaching perspective, the difference comes down to how the set ends. There’s a point where effort is high, but movement is still controlled. And then there’s a point where the body starts compensating—shifting load, breaking position, and recruiting muscles that weren’t meant to do the work.

That second point doesn’t just build bad habits. It reinforces muscular imbalances, alters movement patterns, and over time can lead to postural breakdown and increased risk of injury.

That’s why most effective programs aim for “near failure,” not absolute failure.

In practical terms, that usually means finishing a set with about 1–3 reps still in reserve—challenging enough to stimulate progress, but controlled enough to maintain quality.

You don’t need to empty the tank to make progress.
You need to get close enough—consistently.

Hypertrophy: building muscle without overcomplicating it

Muscle growth is often where training becomes the most confusing. Different rep ranges, different methods, different opinions. But the updated guidelines simplify the picture.

For hypertrophy, what matters most is doing enough quality work over time.

To understand that, you first have to understand what “volume” actually means. Volume is simply the total number of challenging sets performed for a muscle group across a week.

The updated guidelines suggest that muscle growth is best supported when you accumulate around 10 or more challenging sets per muscle group per week. That work doesn’t need to happen in a single session. In fact, it’s often more effective when it’s spread across multiple workouts, allowing you to train with better quality and recover more effectively.

Another important piece is the eccentric phase—the lowering portion of a movement. Controlling that phase increases tension on the muscle and can contribute to growth.

At the same time, muscle growth isn’t limited to a single rep range, and it doesn’t require pushing every set to failure. There are multiple ways to create the stimulus needed for growth, as long as the work is challenging and repeated consistently.

Muscle doesn’t grow because you found the perfect method.
It grows because you gave it a reason to adapt.

Power: the missing link between strength and real movement

Power is often overlooked, but it may be one of the most important qualities to train. It’s not just about how much force you can produce—it’s about how quickly you can produce it.

Power is how strength shows up in real life.

The updated guidelines highlight that power is best developed using moderate loads—typically around 30–70% of your one-rep max—performed with intentional speed and explosive effort. This usually falls within lower-to-moderate rep ranges, where the goal isn’t fatigue, but quality and speed of movement.

You’re not trying to grind through reps—you’re trying to move the weight quickly and efficiently.

If strength is your foundation, power is how you use it.

Muscular endurance: more flexible than we thought

Resistance training still improves muscular endurance, but the research doesn’t point to one exact formula.

There isn’t one perfect way to train—there are many effective ones.

You can build endurance through higher reps, shorter rest, or circuit-style training. What matters most is consistency.

What this really comes back to: longevity

When you zoom out, this isn’t just about strength or muscle. It’s about how your body holds up over time.

The updated guidelines place even greater emphasis on resistance training as a cornerstone of long-term health. That shift reflects just how much more evidence we now have. Compared to the earlier guidelines, the newer position is more forceful in emphasizing resistance training because research has continued to show overwhelming support for its role in positive health outcomes.

Resistance training has been shown to improve cardiovascular function, enhance quality of life, support better mood and cognitive function, and help maintain independence as you age.

It’s not just about living longer. It’s about extending your healthspan—not just your lifespan.

The goal isn’t just to get stronger.
It’s to stay capable.

How this fits into your training—and MaxWell

If you prefer structure, nothing has been taken away from you. Programs still work.

Lean & Hard was the original structured program. Strong & Lean is its successor—built more in line with these updated guidelines and how we now understand strength and hypertrophy development.

The Fat Burning Bible takes a different approach, using dumbbell-based circuit training to build strength, endurance, and conditioning together.

But if your life isn’t predictable—or you want more flexibility—that’s where the newer model fits. That’s what MaxWell Nutrition’s Functional & Lean (F&L) is built around. Instead of forcing you into long, rigid sessions, F&L focuses on building functional strength, injury prevention, and performance through shorter, more adaptable workouts. Each session can stand on its own or be combined into longer workouts depending on your time and energy.

There is also Ranger Ready, a program developed while working with members of the U.S. Army Special Operations Command. Built by Spencer and Mackie Shilstone, it was designed to help extend the careers of some of our nation’s most elite Special Forces members by improving durability, performance, and recovery. If you want to train using the same principles that support that level of readiness, Ranger Ready is that program.

And if you want something even more personalized, custom programming is also available. If you want a program built around your specific performance and life goals, email Spencer Shilstone directly at spencer@maxwellnutrition.com to join the waiting list for one-on-one coaching. Reach out quickly—spots fill up fast each quarter.

The new model isn’t less disciplined.
It’s more adaptable.

Final takeaway

The updated guidelines didn’t rewrite training—they clarified it. You still need effort, progression, and consistency. But you don’t need perfection.

The best program isn’t the most optimized one.
It’s the one you can keep showing up to.

Source:
American College of Sports Medicine (ACSM) Position Stand — Resistance Training Guidelines