Here’s something you might not know: Not all muscle fibres are created equal.

We have two types - slow-twitch and fast-twitch fibres.

• Slow-twitch muscle fibres are built for endurance, allowing them to sustain activity for longer periods with less fatigue. That’s why your calves can handle long, repetitive actions without burning out quickly.

• In contrast, fast-twitch fibres, more prevalent in the upper legs and chest for example, are designed for explosive strength and short bursts of power. They are quicker to fatigue and create a more intense burning sensation during high-intensity efforts.

Here’s why understanding this matters:

Muscles aren't exclusively one fibre type, each muscle has a mix of both. But, as we age, the fast-twitch fibres can start to transition into slow-twitch. This process begins as early as our 30s and accelerates in midlife and beyond, meaning that without targeted training, we lose strength and power at a frightening rate.

After 30, we can lose 3–8% of our muscle mass every decade.

We lose strength at a rate of about 1–2% per year.

We can lose power at a rate of 3-4% per year.

These numbers may seem small, but even by simply halving this rate of decline, it could mean the difference between walking your dog at 80 vs. not, breaking a bone from a fall vs. only getting bruises, or skiing into retirement vs. not. It could be the difference between having metabolic disease at 60 vs. living disease-free.

How will this impact your life now?

Maintaining fast-twitch fibres isn’t just about avoiding frailty in old age. It’s also key to staying energetic, coordinated, balanced, and strong through your 40s, 50s, and beyond - keeping you active, resilient, and drastically lowering your chances of arthritis, osteoporosis, and metabolic disease.

Here are 3 ways stay on top of it:

• Lift heavy sometimes (safely): Incorporate heavier weights for low-rep sets every so often. One to three sets, two to four times per month, will be enough for most. Try to focus on big compound exercises that use lots of muscle at once, like deadlifts, squats, lunges, or chest presses. I often recommend machines for this too, as they provide more external stability and reduce the risk of injury.

• Include explosive movements: Exercises like jumps, short sprints, powerful kettlebell swings, and ball slams are great for fast-twitch retention. One explosive exercise for the upper body and one for the lower body each week is ideal.

• Integrate these into your weight training: Do some explosive jumps as part of your warmup and include one heavy 3-5 rep set during one of your bigger exercises. Simply integrate these into your current weight training plan; don't overthink it.

I hope you've found this insightful and has given you some actionable steps.

Remember - a little bit of effort now makes a huge difference in how strong and capable you feel later.

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