Most discussions on resistance training focus on why more muscle or strength matters for what you can do now.

What’s often ignored is why building a reserve of muscle and strength matters for when you can’t actually use your muscles much at all.

The reality is, we’ll all experience times when our ability to exercise is compromised, or worse - just not possible. And if our activity levels drop subtantially even for short periods, like is typical with recovery from injury or surgery, both muscle mass and strength can decline quite rapidly.

So the question is - could building more muscle and strength now preserve muscle and strength when you can’t be active?

A new study has elegantly shown why building up your muscle and strength reserves now is so critical - not because it protects against inactivity per se, but because it raises your starting point.

Does strength training protect against inactivity?

The study was the PRE-EX randomised controlled trial (Sodenbroe et al., 2026), current in pre-print (meaning it hasn’t yet been peer reviewed).

In the study, both younger and older women, aged 20–35 or 60–85 years were randomly allocated to either four weeks of prehabilitation, which involved 10 sessions of supervised resistance training, or no training.

Following this initial period of training or no training, participants then had one leg immobilised in a knee brace for eight days, followed by four weeks of resistance training rehabilitation.

Before and after the prehabilitation or no training period, the eight days of inactivity, and the four weeks of rehabilitation, the following measures were obtained:

• Muscle size of the quadriceps (measured via gold-standard MRI scans)
• Strength of the knee extensor (quadricep) muscles

The key question was whether the resistance training prior to inacivity (or prehabilitation) reduced the amount of muscle and strength lost, or did it just provide a better starting point?

A bigger reserve, not greater resistance to decline

The first major finding was just four weeks of resistance training twice per week produced some impressive gains:

• Quadriceps size improved by +6.7%
• Knee extension strength improved by 15.2%

During immobilisation participants lost on average -3.2% of their quadriceps muscle size (over five days), and -20% of their knee extension strength (over eight days).

One question was whether these losses were any different in those who did the prehabilitation versus those that didn’t. They weren’t - suggesting resistance training did not make the participants less susceptible to the detrimental effects of inactivity on muscle mass and function.

But there was an important advantage for those who resistance-trained before undergoing a period of disuse:

Because the trained participants started with more muscle, they retained that advantage after both the inactivity and rehabilitation periods. The strength advantage was statistically significant after rehabilitation, but not immediately after inactivity. However, this may partly reflect greater variability in strength measurements immediately following a period of disuse.

Importantly, older women benefited just as much as younger women, with no clear age-related differences in the response to training or subsequent inactivity.

Together, this led the authors to conclude:

“These findings suggest the principal value of prehabilitation lies in raising the functional starting point before predictable disuse, rather than rendering skeletal muscle resistant to the disuse process itself.”

Strength is something you build before you need it

Strength matters for many reasons beyond looking strong or lifting heavier weights.

It’s a way to improve physical performance in daily life, and make your day-to-day activities feel easier.

But beyond that, your strength is like a physical reserve that becomes particularly useful when your ability to exercise or be physically active is temporarily reduced.

It’s really like a savings account. Having more in the bank doesn’t stop unexpected expenses popping up, but it sure means you can deal with them better.

This study is an elegant example that having more muscle or strength in the bank might not lessen the “expense” associated with periods of unexpected inactivity, but you’re better able to pay the debt and keep moving forward.

While it doesn’t show that stronger people recover faster or have better outcomes after something like surgery (though other evidence suggests exercise-based prehabilitation can improve postoperative outcomes), it does highlight the benefits of entering an unavoidable period or inactivity with more muscle and strength.

My question is - why wait for planned disuse periods when you can start preparing for the unexpected now?

So, how much training does it take to build that reserve?

One of the impressive things about this study was how quickly the participants improved.

It took just four weeks of training - twice per week for 45-75 min per session - to boost their muscle and strength by ~7% and ~15%, respectively.

The program they did was relatively simple, but it was reasibly high in volume. There were just five exercises:

• Leg press
• Knee extension
• Leg curl
• Lat pulldown
• Shoulder press

Each progressed from 3 sets per exercise to 4-5 sets per exercise, and from 12-15 reps (at about 60% 1-RM) to 6-8 reps (79% 1-RM) for the leg press and knee extension.

Participants were encouraged to take their sets pretty close to muscular failure from the third session onwards too, so effort levels were quite high.

It’s important to remember these participants hadn’t been regularly resistance training before the study, and the training was fully supervised, so we might not see the same relative gains in experienced lifters or those training unsupervised.

But - you don't need to follow this exact program to build a useful strength reserve.

What you should do to build your reserve now

This study doesn’t tell us the minimum amount of training you need to build a strength reserve.

But we do know from broader research that you can gain meaningful strength without a complex or time-consuming program.

If you’re not currently doing any strength training, just twice per week is a useful starting point, which aligns with our current guidelines.

Focusing on a few exercises covering major muscle groups such as:

• A squat or leg press
• A hip hinge or leg curl
• An upper-body push
• An upper-body pull

And doing each with a load that allows you to do 5-20 reps per set, taking each set within around 3 reps shy of muscular failure, and making things slightly more challenging over time (such as by increasing the weight or adding reps) - will get you most of the way there.

The point is you don’t even have to replicate this 45-75 min routine to make progress - the most important thing is establishing a regular routine you can sustain over time.

Prepare now for the unexpected later...

As much as we’d like to, we can’t predict when we’ll succumb to illness, injury, or other life circumstances that might disrupt our ability to move.

Nor can we prevent any loss of muscle or strength that will likely occur during these dips in our physical activity levels.

But what we can control is how much muscle and strength we take into these periods. Strength training is amazing for what it can do for our ability to move today, but equally - it’s an investment in what we might be able to keep doing tomorrow.

This study shows what can be achieved leading into a predictable period of inactivity.

The more powerful realisation is you don’t actually have to wait until you need strength to start building it.

Thanks for reading!

Until next week,

Jackson

PS: Have you ever had a period of inactivity due to injury, illness, or surgery? I’d love to hear whether you felt your strength (or lack of it!) made a difference. Just hit reply and let me know!

​​​

If you've got a moment, I'd love to hear your thoughts on this edition of The Weekly Exerciser.

Send me a quick message or email - I'll reply to every one!

PS: Did someone forward you this email? You can sign up to The Weekly Exerciser here.

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.