MyMT™ Blog

How your muscles age and why you lose your ‘power’ fibres after menopause.

I can’t go down that slope with all those moguls (bumps). My muscles aren’t what they used to be,” I yelled to hubbie. We were on the piste in beautiful Switzerland and hubbie took a different way down than my usual way down the slope. He’s a way more competent skier than I am and with his decades of skiing behind him, can go anywhere and everywhere. My son is the same. We are over in Switzerland supporting him as he is on the New Zealand Freeride ski team. From the top of the mountain to the bottom, competitors in Freeride head to the top of the mountain and find a line down jumping off natural features along the way. Serious stuff that requires quadriceps full of power and strength.

But here’s the thing – the men in my life can ski powerfully because they still have their Type 2 muscle fibres – the fibres that enable power, speed and jumping. But I’ve lost many of these fibres. You see, along with the loss of oestrogen in menopause, my Type 2 power and speed muscle fibres are diminishing fast. So, when hubbie wants to go one way down the slope powering through the powder and the bumps (mogels), I take a different turn and head out onto the groomed piste to work my legs a different way.

It took me a long time to figure out why I wasn’t able to do the harder, more powerful skiing that I used to be able to do. But as soon as I looked at menopause through the lens of our biological ageing, I knew I would find the answer when I better understood what happens to our muscles as we age.

Ageing has become an important topic for scientific research, including muscular and strength research because life expectancy and the number of men and women in older age groups have increased dramatically in the last century. Muscle strength and function is an increasingly important topic in exercise science, because by 2050, the world’s population over 60 years will double from about 11% to 22%. This means that there will be 2 billion people aged 60 or older living on this planet. Approximately 400 million will be 80 years or older, over half of them women. Our strength and function as we age matters.

With another 20-30 years of living ahead of us, it’s why I’m passionate about telling women in mid-life that it’s not too late to start building strength and getting fitter in preparation for our healthy ageing!  For all of us as we go through menopause and into post-menopause, one of the most important issues to address and prevent is the progressive decline in our muscle function, balance and strength.

Whilst a muscle wasting condition called Sarcopenia is partly responsible for the decline in strength as we age  it’s not the only thing we need to be aware of.   There are other changes to muscles too and as I have discovered with my skiing, these changes relate to the progressive loss of muscle mass and force-generating capacity of Type II skeletal muscle.

How this happens is better understood when we look more deeply at the cellular and molecular levels of muscles. Women’s muscle fibres comprise different ratios of fibres compared to males. There are two general types of fibres – slow twitch and fast twitch. Slow twitch fibres are our endurance fibres and are known in muscle physiology terminology as ‘Type 1’ fibres. Fast twitch fibres are our power and speed fibres and these are known as ‘Type II’ fibres.

Losing oestrogen means that we lose Type II muscle fibres faster than Type 1 fibres.

It’s why many of us lose our ability to jump and turn as quickly as we used to. Especially those of you who are skiers or who enjoy your sports which involve faster movements, jumping, turning or sprint-like movements.

As we transition through menopause and we biologically age and go into our next life-stage, our ageing, there is a 30-40% decline in muscle fibre number and size. For women used to being active, this is important to note because this reduction in muscle fibre number and size is fibre type specific. We can lose anywhere between 10%–40% of our smaller Type II fibres and as I said earlier, this loss in our Type II fibres, means that we also lose our power and speed fibres more than the Type 1 fibres that help us with our stamina and endurance. It’s possibly the reason that physical activity research in older women reports that walking (not running, jumping or sprinting) is the most popular activity as they age. Women in their 50’s are also the highest cohort to drop out of activity as they age. [Women’s Midlife Health, 2015]

But there’s more to understand about our muscle function as we go through menopause too. And it’s to do with our beautiful mitochondria.

I talk a lot about mitochondria in the 12 week Re-Build My Fitness programme. Mitochondria are so important to preserve as we get older. These are the small organelles that sit within muscle fibres where oxygen is stored. They are the site where fats are burned and our energy (ATP) is made. So, for those of you who are wanting to return to levels of fitness or physical activity that enable you to enjoy an enhanced and functional ageing, then you need to boost your mitochondrial cells.

Looking after our mighty Mitochondria matters so much as we go through menopause, especially if you want to manage your weight – and it’s why in my 12 week weight loss programme, I have a module called ‘Fitness Foundations‘ – this teaches women how to improve their aerobic exercise as they are going through menopause, so that they improve energy, weight loss and set up a great foundation for their cardiovascular health as they age. As I discovered myself, the type of exercise you do during and after menopause is crucial to get right – and too many women may well be trying to do the wrong type of exercise which, when they aren’t sleeping, is leaving them exhausted and preventing them from losing belly fat. This increases our stress hormone called Cortisol, which can actually lead to worsening muscle loss (sarcopenia). Hence, it’s important to be sleeping before you do too much exercise.

But there’s more to the mitochondrial story too. Researchers are finding that when it comes to energy production, repair and regeneration, mitochondria matter. Mitochondrial mediated apoptosis (natural cellular death) has been postulated as one of the mechanisms associated with muscle fibre loss with ageing.*  In other words, we need to retain our mitochondria in muscle cells to help to prevent muscular weakness and loss of function as we get older. For those of you, like me, who also want to retain your ability to enjoy physical recreational activities such as skiing, then you need exercise regimes that help you to retain mitochondria and rebuild them as they naturally die off.

The way to help your mitochondria to turn-over in a healthy way is to get back into the right physical activity as you go through menopause. A lack of exercise decreases the efficiency and number of mitochondria in skeletal muscle, while exercise promotes mitochondrial health. So, if you want to retain some of your power and strength fibres (Type II fibres) as well as improve your Type 1 endurance fibres, then a combination of aerobic endurance and strength/ resistance exercises matter.

Mixing up the variety of exercise that you do is important as we get older. This is because different types of exercise can trigger variable but specific responses in the muscle. For example, whereas strength training is efficient at building or retaining the muscle that you do have, doing a little bit of high intensity interval training [HIIT] within aerobic exercises such as cycling and walking has a positive effect at the cellular level at combating age-related loss and weakness. I love this photo that Ginni shared to women on the programme and now shares here with you. Like me, she’s been an avid exerciser all her life, but sore joints, muscles and exhaustion meant that she couldn’t do the exercise she loved to do as she came through menopause.  That’s why I was so pleased that she came into the Re-Build My Fitness programme after doing the Transform Me programme, because now she understands how much our muscles, tendons and joints change as we come through this stage of life. So, it’s a different plan that we need for our fitness as we age, including getting back to doing lower intensity aerobic exercise – not all the high intensity exercise that we have been used to doing for years. Ginni’s now back doing the cycling she loves to do and running and promoting her business, ‘Women on Wheels’. But as I said to Ginni as I do to all the hundreds of women in my programmes – “if you  aren’t sleeping and your joints are sore, or you are overweight, then before doing any High Intensity Interval Training, we need to deal with these other issues first”. This is what I progress women towards in the MyMT programmes. 

When we get back into exercise as we go through menopause, this has an incredible influence on muscle health as we get older. Not only does exercise improve the number and size of mitochondria in skeletal muscle, but exercise improves nerve transmission as well as the exchange of calcium between nerves and muscles. Not many women understand that this is why calcium is a really important mineral as we get older. Calcium helps nerves to ‘jump’ their messages across into muscles and this helps to improve our muscle speed, strength, balance and reaction time. All important functions of muscles as we get older and it’s also why I have a specific emphasis on calcium in my nutritional information for women on the MyMT programmes – it matters not only for bone health, but optimal calcium levels are crucial for our muscles to contract effectively.

 Age-related muscle loss and weakness is a combination of all of these factors, but more and more research is showing that muscle and mitochondria can be re-trained and retained through exercise. Active elderly people have more of these mitochondrial cells than more-sedentary individuals do. This is also the reason why exercise prior to hip and knee surgery can speed up recovery in the elderly.

The good news for women is that exercise can stave off and even reverse muscle loss and weakness with age. Physical activity can promote mitochondrial health, increase protein turnover in muscles, thus aiding repair, and staying active restores nerve signaling involved in muscle contraction and function. And for many of you who don’t have the time to exercise, you don’t need to do as much as what was once thought – 30-60 minutes around 4 times a week is enough to help you age healthily.

When I felt too exhausted to do the exercise that I loved to do and it was no longer helping my weight management, I was so pleased that I had undertaken my doctoral studies on women’s healthy ageing. It lead me down the path towards better understanding about how our body changes when we don’t have the production of oestrogen and progesterone any more. The effect of losing these two hormones on our muscles, tendons and joints as well as our heart is more important that we’ve known in the past. But as the first generation of women to be enjoying exercise and sports right into our menopause years, I also began to understand that everything that is being taught to exercise professionals in many exercise and sports courses has to date, been targeted towards younger populations, athletes and males. Very little is taught about exercise that is specifically aimed at women’s hormonal health, especially in menopause. As I did my doctoral studies on women’s health and exercise, I realised that this is because women in their 50’s today, are the first generation to have aged alongside the modern fitness industry, so exercise prescription messages (and research) are lacking.

This is why I designed and developed the 12 week online Re-Build My Fitness Programme. It’s unique to women in their menopause transition and it’s ON SALE for you now. With savings of $50 for you, this makes it only $199NZ ($66 a month for 3 months). I explain all about it in the video below. If you are keen to come on board (offer ends March 30th), then please enter the PROMO code, FITNESS19 into the Buy Now button here. 


Wendy Sweet, PhD/ REPs NZ Exercise Professional/ Member Australasian Society of Lifestyle Medicine.


Brunner, F., Schmidt (2007).  Effects of aging on Type II muscle fibers: a systematic review of the literature.  Journal of Ageing & Physical Activity, July;15(3):336-48.

Butler-Browne, G.,  Mouly V., et al, (2018). How Muscles Age, and How Exercise Can Slow It. The Scientist Online Edition. 

Pierre, T. & Pizzo, P. (2018).  The Ageing Mitochondria, Genes, 9, 22; doi:10.3390/genes9010022


“If you have ever wondered if there was a clear easy plan to follow to sleep all night, reduce hot flushes and prevent or reduce your weight gain during menopause, then ‘welcome’ – you’re in the right place now.”

Discover how either of my two Menopause Transformation programmes might help you too or take my Symptoms Quiz below… 

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