We all know resistance training does wonders for older adults. Improved strength, better balance, greater independence. It’s a no-brainer, right? But while we often focus on what we can see, the extra reps, the heavier lifts, the steadier gait, there’s a whole lot happening on a cellular level that we don’t always talk about.
What if gaining strength didn’t always mean better muscle health overall? What if some changes that happen inside the muscle during training could actually make it more fatigued in the long run?
Sounds odd, but that’s exactly what one recent study uncovered. And it might just get you thinking differently about how we train older clients.
As An Example, Meet Colin
Colin’s 67, retired, and started resistance training at the local gym three months ago. He’s been consistent, hitting the weights three times a week, working with a PT, and steadily increasing the load. His balance has improved, stairs feel easier, and he’s genuinely proud of how strong he’s getting.
But last weekend, something strange happened. Halfway through a walk with his grandkids, he felt wiped out. Legs heavy, energy gone, and not a hill in sight. “I’m lifting more than ever,” he told his trainer, “so why do I feel more tired than I used to?”
Ageing Muscles: What’s Really Going On?
As we age, our muscles naturally lose mass, strength and power. That much most people already know. But it’s not just the size of the muscle that changes. Inside those muscle fibres, the mitochondria, often called the powerhouses of the cell, start to decline in both number and function. These are the structures that help convert fuel into energy. When they’re not working as well, it means more fatigue, slower recovery and just feeling generally knackered after physical activity.
That’s where resistance training usually comes in. It’s known to help maintain or rebuild muscle mass and strength, which is brilliant. But this particular study looked beyond the surface and asked, “what happens to mitochondrial health during resistance training in older men?”
The Study That Raised a Few Eyebrows
A team of researchers got 16 healthy but untrained older men (average age 66) to take part in a 12-week resistance training programme. Standard stuff including full-body workouts three times a week.
At the end of the programme, they tested the usual strength markers and, as expected, saw solid improvements. Isometric and dynamic strength went up, no surprises there. But then they looked at something a bit different, fatigue resistance. The results were the opposite of what they expected.
The men were actually more fatigued post-training than they were at the start. Even more surprising, muscle biopsies showed that two key proteins, SIRT1 and PGC-1α, had dropped in expression. These aren’t obscure molecular details, they’re critical for mitochondrial function and energy production in muscle.
So What Are SIRT1 and PGC-1α?
Let’s not get too tangled in biochemistry, but it’s worth knowing what these two proteins do.
SIRT1 is like a cellular repairman – it helps regulate inflammation, ageing, and energy use, and is heavily involved in keeping mitochondria ticking over properly. It’s often talked about in ageing and longevity research.
PGC-1α (short for peroxisome proliferator-activated receptor gamma coactivator 1-alpha, is basically the master controller of mitochondrial creation and function. When you do aerobic or endurance training, it’s the guy pulling the strings behind improved stamina and energy efficiency.
So when both of these go down after 12 weeks of resistance training, it raises a pretty important question, “are we improving one aspect of fitness (strength) at the cost of another (fatigue resistance and mitochondrial health)?”
Gains With a Catch?
This study suggests there might be a trade-off, at least when it comes to resistance training alone. Strength goes up, which is great. But fatigue resistance might take a hit and the cellular machinery that supports energy production seems to back off a bit.
Now, it’s worth pointing out this doesn’t mean resistance training is bad, far from it. But it does highlight that training creates very specific adaptations. If you train for strength, you get stronger. But if you want better stamina and muscle energy resilience, you might need to stimulate the body in a different way, with aerobic work, longer time-under-tension or hybrid training methods.
What This Means in Practice
So how do we use this information with our clients? It’s not about abandoning resistance training, far from it. But this study is a great reminder that strength is just one piece of the puzzle, especially for older adults who want more energy for everyday life.
Here’s how you can adjust your programming to support not only strength but also fatigue resistance, energy, and overall muscle health:
Blend Resistance and Aerobic Training: Try to include 1–2 aerobic sessions per week, even if it’s light. Brisk walking, cycling, swimming or rowing can stimulate the mitochondria in ways resistance training doesn’t. You don’t need to turn clients into marathon runners, just get the heart rate up and keep it there for a while.
Use Hybrid Sessions: Think about combining strength and stamina in a single workout. Circuits with minimal rest, resistance intervals or bodyweight complexes e.g. squats, push-ups, rows, lunges done back-to-back, can help maintain both strength and endurance. These workouts challenge the muscles and the energy systems that support fatigue resistance.
Prioritise Movement Quality and Recovery: Fatigue in older clients isn’t just about fitness, it’s also about recovery. Encourage clients to get good sleep, eat well, especially enough protein and nutrients that support mitochondrial health, and manage stress. The better they recover, the better their muscles will function at a cellular level.
Monitor Perceived Fatigue Over Time: Don’t just track reps and weights. Ask how they’re feeling a few hours after a session or the next day. Are they recovering well? Are they feeling drained more often? Keeping tabs on this will help you catch early signs that the training might be skewing too heavily toward one end of the spectrum.
Educate Your Clients: Sometimes older clients worry that feeling tired means they’re unfit or that the programme isn’t working. Helping them understand the difference between strength and fatigue resistance will be enlightening. It builds trust and opens the door to smarter, more balanced training choices.
Final Thoughts
This study doesn’t flip the script on resistance training, it just adds a new layer to think about. Muscles aren’t just meat and motion, they’re full of complex systems that respond in different ways to different types of training. Strength gains are brilliant, but they’re not the whole story. Especially as we get older.
So next time you’re building a programme for an older client, consider what’s happening on the inside as well as what you’re seeing in the gym. A well-rounded approach might just keep their mitochondria and their motivation going strong.
References
Parise, G., Phillips, S. M., Kaczor, J. J., Tarnopolsky, M. A. (2005). Resistance exercise training in older men reduces fatigue resistance and protein expression of SIRT1 and PGC-1α in skeletal muscle. Mechanisms of Ageing and Development, 126(5), 517–522. Click here to review the full research study.
Designing Smarter Programmes for Older Adults Starts Here
As we age, muscle strength becomes vital, but it’s not the whole story. A recent study found that after just 12 weeks of resistance training, older men saw significant strength gains yet experienced a drop in fatigue resistance, alongside a reduction in key proteins (SIRT1 and PGC-1α) that support energy production in muscle. It’s a powerful reminder that effective training for older adults needs to go beyond just lifting heavier. On the Exercise for Older Adults course, you’ll learn how to design balanced programmes that build strength and support energy, stamina and independence. Whether you’re helping clients stay active into their 60s, 70s or beyond, this course will give you the knowledge and tools to make a real difference.
Exercise for Older Adults Course – Distance Study
Train Every Client with Confidence, Including Older Adults
Every client has different needs and when it comes to older adults, the right training can make all the difference. In a recent study, older men saw significant strength gains after just 12 weeks of resistance training but also experienced a drop in fatigue resistance and a decrease in key proteins (SIRT1 and PGC-1α) linked to energy production and healthy ageing. That’s why our Gym Instructor & Personal Trainer Practitioner, Specialist and Master Diplomas™ include an introduction to training special populations, so you can tailor your approach and deliver better outcomes. Whether you’re supporting older clients, those with health conditions, or anyone with unique needs, these diplomas give you the tools to coach with confidence right from day one.
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