What disappears first after 50? Your power, and how to keep it
The first physical quality to fade with age is not endurance but power: the ability to produce force quickly. It depends on your fast-twitch (type II) muscle fibres, which shrink the most with age, but they still respond well to training. Lifting heavy enough, or moving a lighter weight fast, is how you keep them.
What is the first thing to disappear when you hit 50? Is it your fitness? Endurance? Strength? Speed?
The answer lies in a very specific type of muscle fibre. It is the first to decline with age, unless you remember to train it. And most fitness programmes for women ignore it completely.
The answer: your fast-twitch muscle fibres
Your muscles contain slow-twitch (type I) fibres, built for endurance, and fast-twitch (type II) fibres, built to produce a lot of force quickly. It is the fast-twitch fibres that shrink the most with age.
A study by Rachel Nilwik and colleagues in Experimental Gerontology (2013) found that the type II fibres in the thigh muscles of men around 70 were about 29% smaller than in young men, and that this difference alone explained why their thigh muscles were smaller. The study was in men, but it shows an important principle: much of the muscle we lose with age is fast-twitch muscle.
The good news from the same study: after six months of strength training, the older men's type II fibres grew by about 24%. They had not disappeared. They had shrunk from lack of use.
Power fades before strength
Power is force multiplied by speed. In a review in Exercise and Sport Sciences Reviews (2012), Kieran Reid and Roger Fielding describe how muscle power declines earlier and faster than muscle strength with age, and how it is an important predictor of how well older adults manage everyday life.
You feel it as a reduced ability to:
- hurry across the road when the light turns red halfway
- brake quickly on your bike when a driver hasn't seen you
- react fast enough to catch yourself when you stumble on the stairs
- get up from the floor or out of a low chair without pushing off with your hands
First speed goes, then strength, then stamina.
Why most women's training misses it
With this in mind, it may surprise you that most training aimed at women focuses on cardio and endurance: aerobics, circuit training, long planks and light weights for many repetitions. All of it trains the slow-twitch fibres well. Very little of it reaches the fast-twitch fibres.
And they matter for more than speed:
- Muscle mass. Since fast-twitch fibres account for much of the muscle lost with age, training them is central to keeping your muscle.
- Blood sugar. Muscle is one of the main places your body stores and uses glucose, so more active muscle supports a healthy metabolism.
- Signalling. Working muscles release signalling molecules called myokines, which affect metabolism and inflammation elsewhere in the body, as Bente Klarlund Pedersen and Mark Febbraio describe in Nature Reviews Endocrinology (2012).
- Bone. Bone responds to heavy, fast loading. In the LIFTMOR trial (Watson and colleagues, Journal of Bone and Mineral Research, 2018), postmenopausal women with low bone mass who did supervised high-intensity strength and impact training twice a week for eight months improved their bone density in the spine and hip, while the control group lost bone.
How to wake up your fast-twitch fibres
There is one small "but". Slow-twitch fibres have a low activation threshold. Fast-twitch fibres have a much higher one. Simply put: it takes more to get them working. Your body almost always uses the slow-twitch fibres first, and only recruits the fast ones when the task demands it. The brain prefers not to.
"Demanding" does not have to mean lifting the heaviest weight possible. There are three ways in:
- Heavy enough. A load you can lift with good technique for around 5-8 repetitions, not 25.
- Fast enough. Accelerating a lighter weight explosively, as in a kettlebell swing, recruits fast-twitch fibres too.
- Tense enough. Creating a lot of tension in the muscle, for example by squeezing hard at the top of a movement.
Before all three comes contact. Many women find it hard to activate their muscles fully, so the first step is strengthening the signal between brain and muscle. When that connection is in place, you get access to much more of the strength you already have.
Start where you are. Short, focused sessions a few times a week, or a little every day, are enough to make a difference. If you have osteoporosis, a heart condition or another health issue, get guidance before you start lifting heavy or explosively.
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Frequently asked questions
What is the first thing we lose with age?
Muscle power, the ability to produce force quickly, tends to decline earlier and faster than strength or endurance. This is largely because fast-twitch (type II) muscle fibres shrink the most with age. Power matters for everyday tasks such as catching yourself when you stumble.
Can women over 50 still build fast-twitch muscle?
Yes. Fast-twitch fibres shrink from lack of use, but they respond to training. In a study in Experimental Gerontology, six months of strength training increased the size of type II fibres in older adults by about 24%. Lifting heavy enough or moving a weight fast is the key stimulus.
How do I train power after 50?
To train power after 50, combine strength exercises with a load heavy enough for around 5-8 good repetitions and explosive movements with a lighter weight, such as kettlebell swings. Focus on quality, rest between sets, and get guidance first if you have osteoporosis or a heart condition.