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We all know stretching’s good for mobility and flexibility. But did you know a recent study has shown it can actually help build muscle? More specifically, it supports muscle growth in people who can’t lift, press or squat their way through a traditional programme. And for personal trainers working with older adults, post-op clients or anyone in rehab, this might be a very effective tool at getting these clients better results.
Stretch-mediated hypertrophy (SMH) is one of those sciencey terms that’s quietly reshaping how we think about recovery and strength. It doesn’t mean stretching should replace lifting weights, we’re definitely not saying that. But it’s worth understanding how it works and when it might help your clients.
If you’re currently studying or thinking about expanding your skills through one of our pt courses, this is exactly the sort of evidence-based insight that sets you apart. And if you’re already qualified and delivering personal trainer courses, it’s something worth passing on to learners navigating the world of rehab programming.
Stretch-mediated hypertrophy isn’t about your average five-minute post-workout cool-down. We’re talking long-duration static stretching, held for 15 minutes or more, several times a week. In these sessions, the muscle is placed under passive tension for extended periods. Think of it more like mechanical loading, without the reps and dumbbells.
The idea’s not brand new. Animal studies dating back to the 1970s found that sustained stretching could trigger serious muscle growth of up to 300% increases in muscle mass in some cases (Antonio & Gonyea, 1993). For years it was brushed off as something that worked in birds, but not humans.
Fast forward to now, and the human research is finally catching up. A number of recent studies, including Warneke et al. (2025), have shown that daily static stretching, when done at high enough volumes, can indeed lead to measurable gains in muscle size and strength. For example, one study found that stretching the gastrocnemius for 60 minutes per day over six weeks increased strength by up to 18% and muscle thickness by 5–8% (Warneke et al., 2025).
Just to be clear, this isn’t about swapping deadlifts for downward dog. Resistance training is still the gold standard for hypertrophy. But when a client can’t train that way, stretching may offer a viable route to preserve or even build strength.
Not every client can walk into a gym and load up a barbell. And that’s where stretch-mediated hypertrophy gets interesting.
Take post-injury recovery. After ACL surgery or an ankle fracture, for instance, many clients face weeks of limited mobility. Even with access to rehab facilities, they’re often left with strength imbalances between limbs and re-injury fears can hold them back from engaging in traditional strength work (Stevens et al., 2004; Hsu et al., 2017). Adding long-duration stretching in a passive and safe way, may slow down muscle loss or even stimulate some growth.
There’s also solid reasoning for using stretching with older clients. Many struggle with the confidence, time or physical capacity needed for progressive resistance training. The American Geriatrics Society lists muscle weakness and functional impairments as key fall risk factors in older adults (AGS, 2001). If a client won’t, or can’t do traditional strength work, stretching could be a useful alternative. Not a miracle solution, but something is definitely better than nothing.
And then there’s type 2 diabetes. A growing body of research shows that muscle mass is key for glucose metabolism. Stretching has been shown to improve blood glucose and HbA1c levels in people with type 2 diabetes. It’s believed SMH may increase insulin-independent glucose uptake via GLUT-4 transporters (Thomas et al., 2024). If stretching can improve glycaemic control and support muscle health in this population, that’s worth paying attention to.
Now that we know what’s possible, let’s get practical. What does stretch training look like in the real world?
The studies that show muscle gains from stretching typically use protocols of 15 to 60 minutes per muscle group, daily or near-daily, for six to eight weeks. That’s not something most clients will naturally commit to. It has to be doable and preferably passive.
Orthotic devices or stretch braces can be useful in clinical settings, especially for lower limbs. But for everyday clients, you might suggest seated or floor-based stretches they can do while watching TV or working at a desk. Think passive calf stretches with a wedge or strap, long seated hamstring holds or supported pec stretches using a doorframe or foam roller.
Intensity matters too, but not in the same way as lifting. Here, it’s about discomfort, not pain. Some studies suggest moderate pain thresholds may help increase ROM and trigger adaptations (Hatano et al., 2022), but we’re still in murky waters when it comes to standardising stretch “intensity.”
What’s most important? Consistency and duration. Sporadic short stretches won’t cut it.
If you’re thinking “hang on, doesn’t yoga do all this already?”, you’re on the right track.
Styles like yin yoga or restorative yoga often involve long-held static postures that resemble the stretching protocols studied in SMH research. So yes, yoga might be a great entry point for clients who need a gentle, structured way to include stretch-based strength support. Yoga may be ideal for those with limited mobility or chronic conditions.
The bonus with yoga is that it ticks other boxes too. It has breath control, helps with stress management and can improve focus. These are all helpful for recovery and adherence.
Just remember, not all yoga styles will deliver the kind of mechanical tension needed for hypertrophy. A few chilled-out cat-cows won’t do the job. But a well-structured yin class, held for 3–5 minutes per pose, just might.
While stretch-mediated hypertrophy is fascinating, we don’t want to oversell it. For healthy, active clients, resistance training is still far more efficient in building muscle. But there is value in combining the two.
Some trainers are now experimenting with inter-set stretching. That is, holding light static stretches for the target muscle group between sets of strength work. This could help increase time under tension and possibly improve hypertrophy outcomes (Schoenfeld et al., 2022). It’s still early days, but it’s an interesting area to watch.
For athletes and bodybuilders, stretch training may also act as a volume booster. Give it a try on those stubborn muscle groups. One case study on a drug-free competitive bodybuilder showed a whopping 23.4% increase in calf size after combining resistance training with high-volume static stretching over 12 weeks (Homer et al., 2025). That’s a lot of growth, even in someone already highly trained.
Stretching won’t replace strength training but it can support it. And in the right context, it might even spark growth when other options aren’t available.
For clients in recovery, those managing chronic conditions or anyone too injured or anxious to lift, stretching may offer a lifeline for muscle health. For PTs, it’s another tool in the kit and one that’s backed by emerging science, not just tradition.
If you’re training or mentoring others in this space, keeping up with this research adds real value to your work. After all, helping clients feel stronger, move better and recover safely is what this job is all about.
If you’re a qualified fitness professional looking to deepen your knowledge of stretching beyond the usual warm-up and cool-down routines, the Advanced Stretching course from TRAINFITNESS is exactly what you need. Recent research has shown that long-duration static stretching can lead to muscle strength increases of up to 18% and muscle thickness gains of 5–8%, even in the absence of resistance training (Warneke et al., 2025). This opens up exciting opportunities to support clients recovering from injury, managing chronic conditions like type 2 diabetes or struggling with mobility. The course covers a wide range of techniques and applications, including how to tailor stretching programmes to individual needs, making it an ideal next step for PTs and coaches who want to expand their toolbox and deliver smarter, more effective programmes.
Advanced Stretching course – In-Person & Live-Virtual
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Take your career further with the Yoga Instructor Course from TRAINFITNESS. Designed for fitness professionals who want to bring the proven benefits of yoga into their sessions. Yoga isn’t just about relaxation or flexibility; research shows that regular yoga practice can improve muscular strength by up to 24%, balance by up to 30%, and even reduce the risk of falls in older adults by nearly 40%. If you’re working with clients recovering from injury, managing stress or simply wanting more functional movement, this course gives you the skills to deliver structured, safe and effective yoga classes. Gain a recognised qualification and open the door to new opportunities in health, fitness, and wellbeing.
Yoga Instructor Diploma – In-Person & Live-Virtual
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