It’s 2009, and I’m sitting in a lecture theatre at RMIT University in Melbourne, Australia.

The subject is resistance training, and Dr Tony Shield is walking us through the gold standard evidence for how to prescribe it to get people stronger, more powerful, or to grow muscle.

And much of this came from ACSM’s 2009 Progression Models for Resistance Training.

Since way back then (when I was a 21-year old 3rd-year undergrad student), this has been the best summary of the “how to” with resistance training.

Which is why I was so excited when the ACSM finally updated their guidelines just this month.

So after 17 long years, the key questions are:

What exactly has changed about what we know about resistance training?

And, how does it impact how you should approach it?

Read on to find out.

The 2026 update is pretty substantial

First of all, these new guidelines aren’t a minor revision by any stretch.

They summarise 15+ years of new research, including 137 systematic reviews and data from more than 30,000 people.

I’m sure you’ll agree that’s a pretty decent evidence base.

And while you might expect this to overhaul what we “thought” we knew, the more interesting findings weren’t what was re-confirmed...

But actually what didn’t seem to matter so much anymore.

What didn’t change is the fundamentals still hold

If your goal is to get stronger, the key elements haven’t changed.

Strength still improves most when you train with relatively heavy loads (such as 80% or more of your 1-rep max), do 1–3 hard sets per exercise, train at least twice per week, and use a full range of motion.

The 2009 guidelines said something similar, and 130+ systematic reviews didn’t disagree.

For growing muscle though, one key factor stands out:

The amount (or volume) of training you do matters more than exactly how it’s structured.

Specifically, the evidence points to at least 10 sets per muscle group (across multiple exercises) per week as the threshold for meaningful muscle hypertrophy.

Mind you, other recent evidence suggests as little as 4 sets (per muscle) per week can be enough.

But things like load (how heavy), frequency (how often), and whether you take your sets to failure didn’t consistently change muscle growth outcomes when total volume was taken into account.

For gaining muscle in particular, many roads to the same destination.

What the evidence has finally let go

This is where it gets interesting.

Several factors often intensely debated in fitness circles - including periodisation, time under tension, machines versus free weights - didn’t consistently produce different outcomes with resistance training.

That means for most people, these things probably don’t matter much at all.

So why did they attract so much attention in the first place?

Partly because the 2009 guidelines treated them as meaningful levers, and periodisation (or the planned variation in training over time) in particular was presented as providing a clear advantage over non-periodised training.

But this updated evidence paint a different picture:

With appropriate progressive overload, periodised programs are probably not superior to non-periodised ones for improving strength or muscle growth.

The story is similar with training to “failure” too

Despite being long debated as either essential or dangerous, it didn’t consistently enhance strength, hypertrophy, or power versus stopping sets short of failure.

The guidelines now say stopping 2–3 reps short of failure is enough, and may actually be preferable for some individuals given the elevated injury risk at true failure.

This fits with our research showing basically the same thing (for muscle gain specifically).

Now this doesn’t mean none of these variables matter at all. In some cases, the limitations of the existing evidence mean we can’t really draw firm conclusions.

For example, most studies use multiple sets per exercise or muscle group, so it’s possible getting close(r) to failure might be more important with single-set programs.

But overall, these factors probably matter less than showing up, training with effort, doing enough total work, and progressing over time.

The biggest shift is from optimisation to participation

One of the most important aspects of the 2026 guidelines was a shift in messaging.

These new guidelines push the conversation away from optimisation (or finding the “ideal” program) towards better participation.

Because the evidence shows most resistance training programs can work.

Strength, muscle mass, power, and physical function improved across a wide range of approaches, including circuit training, elastic band training, and home-based training.

Which means the main barrier to people getting the benefits of resistance training isn’t program design, but whether they actually do it at all.

Current estimates suggest only around 20-30% of adults meet muscle-strengthening guidelines, and among older adults the figure is likely closer to 10–15%.

So instead of asking “what’s the optimal program?”, we really should be asking - “what’s the smallest amount of training someone can do consistently?”

As you’ll know from being an avid reader of the The Weekly Exerciser - even 1-2 sets per exercise, twice a week can deliver meaningful improvements in strength, function, and muscle mass.

No one argues this is “optimal”.

But for beginners, busy people, older adults, and those returning after a break, it’s enough.

Because the program doesn’t need to be ideal, it just needs to be done.

What’s changed for older adults?

The 2026 guidelines apply to healthy adults across all ages, and the evidence base includes a large number of older adult studies.

A few things are worth highlighting for this group specifically.

Resistance training is safe for older adults, despite this being a common concern keeping people away.

An analysis of >38,000 participants (including >11,000 older adults) found resistance training did not increase the risk of serious adverse events, with injury rates no higher than with aerobic exercise.

So-called “power training” - where you deliberately perform the lifting phase as fast as possible - shows particular promise for older adults.

Power training consistently improved multicomponent physical function (things like getting up from a chair, walking speed, and balance) compared to standard resistance training.

Given power declines faster than strength with age, and is closely linked to falls risk and functional independence, this finding matters.

What this means in practice

The shift in the 2026 ACSM resistance training guidelines is pretty powerful.

My read is it reflects what the research has been building toward for years:

The dose needed for meaningful benefits is lower than most assume, and the range of approaches that can deliver that benefit is wider than you'll often hear.

So if you’ve been waiting for the perfect program before starting, it simply doesn’t exist.

And you don’t need it either.

Because as these new guidelines show, the best program is the one YOU can actually stick with.

Once again, thanks for being here!

Until next week,

Jackson

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IMPORTANT:

The information contained herein is of general nature only and does not constitute personal advice. You should not act on any information without considering your personal needs, circumstances, and objectives. Any exercise program may result in injury. We recommend you obtain advice specific to your circumstances from an appropriate health professional before starting any exercise program.