# Reactive Force and Why Women Over 40 Lose It
There is one physical property that is surprisingly rarely discussed in the context of aging – even though its decline affects everyday life far more than it might seem. It is not strength as such, not endurance, nor flexibility. It is reactive strength – the ability of muscles to quickly respond to sudden loading, absorb impact, and immediately spring back. And this is precisely the quality that women over forty lose first, quietly and without much warning.
This may sound abstract, but it helps to imagine a concrete situation: you are crossing the street and at the last moment you realise a car is not slowing down. You need to jump out of the way quickly. Or you are going down stairs and your foot slips – you reflexively grab hold, tense your muscles and stabilise your body before you are even consciously aware of it. These are exactly the moments when reactive strength is decisive. And these are precisely the moments when it first becomes apparent that we have less of it than we thought.
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What reactive strength actually is and why it matters
Reactive strength – technically referred to as reactive strength or as a component of so-called elastic strength – describes the ability of the neuromuscular system to manage the rapid transition between the braking phase and the propulsion phase. It is a combination of speed, strength and neural coordination all at once. Athletes train it through jumps, sprints or changes of direction. But in everyday life we use it when walking on uneven terrain, when getting up quickly from a chair, when catching a falling object, or precisely when regaining balance.
What makes reactive strength so specific is its dependence on the so-called stretch reflex – a neurological mechanism capable of activating muscles within milliseconds. This reflex is controlled by spinal circuits and operates faster than the conscious brain can make any decision. The problem is that with age – and especially after the onset of perimenopause – this mechanism slows down and weakens. Research published in the Journal of Applied Physiology, for example, repeatedly shows that the speed of neural transmission declines with age significantly faster in women than in men, particularly around the age of forty.
Why forty specifically? The answer lies largely in the hormonal environment. Oestrogen does not only play a role in the reproductive system – it also influences bone density, the elasticity of tendons and ligaments, and especially the function of so-called type II muscle fibres, i.e. fast-twitch muscle fibres. These are directly responsible for explosive, reactive movements. When oestrogen levels begin to fluctuate and decline, these fibres are the first to lose both volume and functionality. The result is not just reduced strength in the conventional sense, but above all a slowed response to sudden stimuli.
Add to this the natural loss of muscle mass – sarcopenia – which begins in most people around the age of thirty-five and accelerates significantly after forty. A 2021 study published in the American Journal of Clinical Nutrition estimates that women may lose up to 1–2% of muscle mass per year after forty, with fast-twitch muscle fibres declining proportionally faster than slow-twitch ones. The result is paradoxical: a woman may subjectively feel that she is "in good shape" because she walks, practises yoga or swims – and yet her reactive strength is declining without these activities compensating for it.
Why women do not notice this for so long
This is where an interesting paradox arises. Reactive strength does not manifest during slow, controlled movements. If you practise yoga, Pilates or even conventional weight training with slow repetitions, the neuromuscular system is barely utilised for reactivity. It is only tested when an unexpected, rapid stimulus arrives – and that is precisely the situation we consciously try to avoid in everyday life, because we have learned to move "more carefully".
Yet this caution is itself a symptom. As physiotherapist and researcher Stuart McGill noted: "The body will adapt to whatever movement pattern you give it – if you only give it slow and controlled movements, it will excel at those and get progressively worse at everything else." This adaptability is on one hand a great strength of the human body, but on the other hand it can quietly deepen a deficit in areas where we fail to notice it.
Women over forty typically only become aware of changes in reactive strength retrospectively – after experiencing a fall or a near-fall in which they failed to catch themselves in time. Or they notice that they instinctively slow down when walking on cobblestones because they "don't trust themselves". Or they find that during quick movements – such as chasing a child or catching a ball – they feel uncoordinated and uncertain. These are not manifestations of "ageing in general". They are specific manifestations of declining reactive strength.
The risks, moreover, are not merely athletic. Falls are one of the most common causes of serious injury in middle-aged and older women. According to data from the World Health Organization, falls are the second leading cause of unintentional injury deaths worldwide, and their frequency increases markedly after the age of fifty. A key factor is not only bone density, but precisely the speed at which the neuromuscular system can respond to destabilisation – that is, reactive strength.
How to train reactive strength and what actually works
The good news is that reactive strength is trainable at any age. The neuromuscular system retains its plasticity even after forty, fifty and sixty – it simply needs the right stimuli. And those are different from what most women of this age are accustomed to.
The foundation consists of so-called plyometric exercises – movements that deliberately work with the rapid transition between the eccentric (braking) and concentric (propulsive) phase. This does not have to mean demanding jumps like those performed by athletes. Simple variations are suitable for beginners:
- High knees on the spot – rapid alternating knee lifts, emphasis on speed rather than height
- Step-up with a quick push-off – stepping onto a step or box with emphasis on an explosive push-off
- Hopping over a line – lateral jumping over an imaginary or real line, both feet together
- Light jumps from a squat – not necessarily high, but fast and with an immediate landing back into a squat
- Catching a ball or other activities requiring a quick response from the hands and the whole body
The key principle is speed of execution, not load intensity. Reactive strength is not trained through slow repetitions with a heavy barbell. It is trained through short, explosive movements in which the nervous system must respond quickly. The frequency need not be high – two to three times per week with ten to fifteen minutes focused on reactivity is significantly better than no such training at all.
Balance and proprioception also play an important role – the body's ability to perceive its position in space. Standing on one leg, walking on uneven surfaces, exercising on a balance board, or even simply closing your eyes while standing – all of these activities train the neural pathways that underlie reactive strength. Physiotherapists and sports trainers agree that combining proprioceptive training with plyometric elements yields the best results.
The role of protein in the diet is also not to be underestimated. Type II muscle fibres are more metabolically demanding and their regeneration requires an adequate intake of amino acids. Research shows that women over forty tend to undervalue protein – yet recommendations for active individuals are around 1.2 to 1.6 grams per kilogram of body weight per day. Without this foundation, reactive strength training yields significantly poorer results.
Consider the example of Markéta, a forty-four-year-old teacher who regularly practised yoga and occasionally went swimming. She felt fit and healthy. Then, while descending stairs quickly, she twisted her ankle – her foot slipped and her body did not react in time. After consulting a physiotherapist, she began incorporating short blocks of plyometric and balance exercises twice a week. After four months, she herself described feeling "more confident in her movement" and said she had begun moving naturally again, without the unconscious caution that had been holding her back.
This story is not exceptional. On the contrary, it is very typical – and it illustrates how easily reactive strength can be restored when we address it intentionally.
Reactive strength is not merely a sporting category for athletes. It is a fundamental component of movement safety and quality of life – a capacity that determines whether the body handles unexpected situations gracefully and without injury, or whether it fails at precisely the moment we least expect it. And because women over forty lose it quietly and quickly, consciously maintaining this capacity is one of the smartest investments in one's own health that can be made. Not so that women look different or outperform others – but so that they can move freely, confidently and without fear for many decades to come.
