A disease that makes climbing stairs feel like climbing a mountain
Imagine your muscles running out of fuel halfway through brushing your teeth.
That's daily life for many people with mitochondrial myopathy (an inherited muscle weakness caused by defects in the cell's energy factories).
For years, the advice was to take it easy. Save your energy. Don't push.
But that guidance is shifting.
Mitochondria are the tiny engines inside every muscle cell. They turn food and oxygen into usable energy. In mitochondrial myopathy, those engines are faulty from birth because of mutations in the DNA.
The result: tired muscles, cramps, and poor exercise tolerance. There's no cure. Medications barely move the needle.
So researchers have been asking a bold question: what if carefully dosed exercise could actually make the broken engines work better?
The old thinking was simple. If muscles can't make energy, don't ask them to. Rest protects them.
The new view flips that. Gentle, repeated exercise might train the surviving healthy mitochondria to multiply and work harder. It could even wake up muscle stem cells that have been sitting idle.
Here's the twist: the effect seems to depend on which gene is broken.
Picture a factory where 7 out of 10 machines are broken. Resting won't fix the broken ones — but it also won't help the 3 working ones.
Exercise is like putting those 3 good machines on a training schedule. Over weeks, they get more efficient. The body even builds new ones alongside them.
Resistance training (lifting weights) does something slightly different. It recruits satellite cells — muscle stem cells that can patch in fresh, healthier tissue over time.
Combining the two, aerobic plus resistance, appears to layer the benefits.
Researchers reviewed 15 clinical studies published between 1990 and September 2025. Together they included 157 people with mitochondrial myopathy.
Only one study was a full randomized controlled trial. The other 14 were smaller, non-randomized trials. Most programs ran 8 to 14 weeks, with 3 to 5 sessions per week at moderate intensity.
Outcomes measured included peak oxygen use (VO2 max), maximum workload, muscle strength, and markers of how well mitochondria recovered energy.
Moderate aerobic training improved peak oxygen use and helped muscles refill their energy stores (phosphocreatine) faster after effort. Antioxidant defenses also went up.
Resistance training added raw strength and reduced the number of energy-starved fibers in muscle samples.
Importantly, creatine kinase — a blood marker that rises when muscles are damaged — did not consistently climb. That matters, because it suggests exercise wasn't secretly hurting the muscles.
But response varied a lot depending on which genetic mutation a patient had.
People with large DNA deletions or the common m.3243A>G mutation tended to adapt well. Those with certain other point mutations showed mixed or even worse results.
The bigger picture
For decades, mitochondrial disease clinics have lacked tools. Exercise isn't flashy, but if it works, it's cheap, available, and side-effect light.
The bigger shift is philosophical. We used to treat tired muscles by protecting them. Now we may be able to train them — but the prescription has to be personalized by genetic subtype, not one-size-fits-all.
If you or a loved one has mitochondrial myopathy, don't start a program on your own. This is a condition where the wrong kind or amount of exercise could cause harm.
Talk with a neuromuscular specialist and, ideally, a physical therapist who has worked with mitochondrial disease. Ask what's known about your specific mutation.
Most programs in these studies were moderate in intensity, supervised, and built up slowly over weeks.
Where it falls short
This was a review of mostly small studies — some with as few as 4 patients. Only one was a proper randomized trial. That means we're seeing promising signals, not ironclad proof.
Sample sizes were too small to know whether rare adverse effects occurred. Long-term outcomes beyond a few months are mostly unknown.
Larger, longer, randomized trials are needed — ones that group people by mutation type so the right dose can be matched to the right person. Researchers also want clearer guidance on when resistance training helps versus when it strains.
For now, the message is cautiously hopeful: these muscles can, in many cases, be trained. Just not casually.
