Leg Power and Brain Power – How Stronger Legs Protect Against Cognitive Decline
As the global population ages, one of the greatest health challenges we face is maintaining cognitive function and preventing dementia. While countless studies have suggested that physical activity protects the brain, the results from intervention trials have often been inconsistent. Some programs show short-term gains in memory or attention, but very few have demonstrated lasting changes in the trajectory of cognitive ageing (Steves, Mehta, Jackson, & Spector, 2016).
A landmark 10-year study of over 300 older female twins sought to answer a more precise question: does muscular fitness—specifically, leg power—predict long-term brain health? Unlike self-reported activity levels, which can be unreliable, leg power provides an objective measure of both muscular strength and functional ability. By combining twin comparisons with brain imaging, this study offered one of the most rigorous tests yet of how lower-body strength relates to cognitive ageing (Steves et al., 2016).
The results were striking: women with greater leg power at baseline showed less cognitive decline, larger total grey matter, and healthier brain structure a decade later—even after accounting for shared genetics, early life environment, and lifestyle. These findings suggest that maintaining strong legs may be one of the most powerful, and overlooked, ways to protect brain health as we age.
To test whether muscular fitness predicts cognitive ageing, researchers conducted a longitudinal observational study using data from the TwinsUK registry. The study followed 324 healthy female twins, aged 43 to 73 at baseline (average age 55), over a 10-year period (Steves, Mehta, Jackson, & Spector, 2016).
Cognitive performance was assessed in 1999 and again in 2009 using the Cambridge Neuropsychological Test Automated Battery (CANTAB). This computer-based test battery focused on memory and processing speed — two domains known to be sensitive to age-related decline. To capture overall cognitive ageing, researchers calculated a combined measure called Age-Related Cognitive Change (ARC) (Steves et al., 2016).
The key predictor was leg extensor power (LEP), measured at baseline using the Nottingham Power Rig. This validated tool assesses both the force and velocity of leg extension and has been shown to be a reliable measure of lower-limb power in older adults. Each participant performed three maximal-effort leg presses, and the best result was recorded (Steves et al., 2016).
To strengthen their findings, the researchers also included:
Self-reported physical activity levels over the past year, categorized from inactive to heavy.
Covariates such as cardiovascular health, diabetes, diet, socioeconomic status, and early-life factors like birthweight.
A discordant twin design, comparing twins with differing leg power to account for shared genetics and early environment.
A neuroimaging sub-study, where a subset of identical twins underwent MRI scans 12 years later to examine differences in brain structure and activation.
This multi-layered approach made the study uniquely robust, allowing the authors to test not just whether leg power predicts cognitive ageing, but also whether those associations could be explained away by genetics, lifestyle, or other health factors
Key Findings
The study produced several important insights into the link between muscular fitness and brain health:
1. Leg Power Predicts Cognitive Ageing
Women with higher leg extensor power (LEP) at baseline experienced significantly less cognitive decline over 10 years compared to those with lower leg power. Even after adjusting for a wide range of health, lifestyle, and developmental factors, LEP remained one of the strongest predictors of age-related cognitive change (Steves, Mehta, Jackson, & Spector, 2016). Specifically, an increase in LEP of 40 watts corresponded to the equivalent of being 3.3 years “younger” cognitively.
2. Brain Structure Benefits
In the neuroimaging sub-study, women with greater baseline leg power showed larger total grey matter volumes 12 years later (standardized β = 0.362, p = 0.005). Weaker twins also had 26% larger ventricles, a sign of greater brain atrophy, compared to their stronger sisters (Steves et al., 2016). These results suggest that leg power not only slows cognitive decline but also supports healthier brain structures associated with memory and executive function.
3. Twin Comparisons Strengthen the Case
One of the most compelling aspects of this research was the twin design. Within twin pairs, the sister with stronger leg power at baseline consistently showed better cognitive outcomes a decade later. This effect held even in dizygotic (fraternal) twins, indicating that the relationship is unlikely to be explained solely by shared genetics or family background (Steves et al., 2016).
4. Physical Activity vs. Leg Power
Although self-reported physical activity showed a weak association with cognitive ageing, the effects were far less consistent than those of leg power. This suggests that objective measures of muscular fitness may be more reliable predictors of long-term brain health than activity questionnaires (Steves et al., 2016).
Taken together, these findings highlight leg power as a unique and powerful biomarker of healthy cognitive ageing, above and beyond genetics, lifestyle, or cardiovascular health.
Why Legs Matter More Than Other Measures
One of the most striking aspects of this study was that leg power outperformed other common measures of physical fitness when it came to predicting cognitive ageing.
When researchers compared leg extensor power (LEP) to grip strength, lung function, and leg lean mass, none of these alternative markers showed a significant relationship with long-term cognitive outcomes once LEP was included in the model (Steves, Mehta, Jackson, & Spector, 2016). For example, grip strength — often used as a quick clinical measure of muscular fitness — was not associated with age-related cognitive change (β = –0.031, p = 0.588). Similarly, lung function and lean mass provided no predictive value for brain ageing once leg power was accounted for.
Why might this be the case? Leg power is unique because it captures both force and velocity, reflecting not just muscular strength but also the speed of neuromuscular activation. Importantly, LEP declines earlier and more sharply with age compared to strength alone, making it a sensitive marker of functional ageing (Steves et al., 2016).
The researchers also noted that LEP may represent a more direct measure of daily physical function. Unlike grip strength, which is less tied to mobility, or lung function, which reflects cardiopulmonary health, leg power is directly linked to independence, balance, walking ability, and reaction speed — all of which are critical to maintaining brain health and preventing decline.
In fact, the study showed that the protective effects of LEP on cognition were equivalent to a difference of several years in biological ageing. This reinforces the idea that maintaining lower-limb explosive power is not just about physical mobility, but may also be one of the most effective ways to protect long-term cognitive function (Steves et al., 2016).
Mechanisms Behind the Link
Why would stronger legs translate into a healthier brain? The study highlights several possible mechanisms, pointing to a shared biological pathway between muscle function and brain ageing (Steves, Mehta, Jackson, & Spector, 2016).
1. Vascular Health
Physical activity and muscular power improve cardiovascular health, lowering the risk of conditions such as ischemic heart disease and hypertension. Both of these have been linked to cognitive decline and brain atrophy in older adults. Stronger legs may therefore help maintain blood flow and reduce vascular damage in the brain, slowing cognitive ageing (Steves et al., 2016).
2. Neurotrophic and Growth Factors
Exercise stimulates the release of neurotrophic molecules, such as brain-derived neurotrophic factor (BDNF), insulin-like growth factor-1 (IGF-1), and vascular endothelial growth factor (VEGF). These chemicals promote the growth of new neurons, strengthen synaptic connections, and increase angiogenesis — processes that are essential for preserving grey matter and cognitive performance (Steves et al., 2016).
3. Inflammation and Immune Function
Age-related inflammation contributes to both physical frailty and neurodegeneration. Individuals with higher lifelong activity levels show reduced markers of inflammation and better immune regulation. This suggests that maintaining muscular fitness, particularly in the lower limbs, may dampen systemic inflammation that accelerates brain ageing (Steves et al., 2016).
4. Neuromuscular and Cognitive Coupling
Leg power is not just about strength — it reflects neuromuscular speed and coordination, both of which rely on rapid signaling between the brain and muscles. Declines in this system may parallel declines in cognitive processing, meaning that training the legs also helps preserve the neural circuits responsible for attention, memory, and reaction time (Steves et al., 2016).
Together, these mechanisms suggest that leg power is not merely a marker of general health but may play a direct role in preserving brain structure and function throughout ageing.
Implications for Healthy Ageing
The findings from this twin study carry important lessons for how we think about ageing and brain health. Unlike genetic factors or early-life influences, leg power is modifiable — and this makes it a promising target for interventions aimed at preserving cognition.
First, the results show that muscular power matters more than activity levels alone. While self-reported physical activity was weakly associated with better outcomes, leg extensor power (LEP) remained the strongest and most consistent predictor of cognitive ageing (Steves, Mehta, Jackson, & Spector, 2016). This suggests that structured exercise programs focusing on power-based training for the lower body could have long-term cognitive benefits.
Second, the study demonstrated that even relatively simple, low-intensity interventions can significantly improve leg power in older adults. For example, progressive walking or resistance-based exercises have been shown to increase muscle power within 12 weeks, even when aerobic capacity or muscle size do not change (Steves et al., 2016). This means that interventions do not necessarily need to be high-intensity or complex to be effective.
Third, the evidence highlights the need for a public health shift. Much of the current messaging around exercise in ageing populations emphasizes aerobic fitness. While cardiovascular health remains important, this study shows that maintaining lower-limb power may be equally, if not more, essential for healthy cognitive ageing.
In practice, this means encouraging midlife and older adults to incorporate exercises such as squats, step-ups, sit-to-stands, and resistance band work — movements that not only maintain mobility and independence but may also protect the brain from decline.
As the authors note, interventions designed to improve leg power “may help reach a universal goal of healthy cognitive ageing” (Steves et al., 2016, p. 138).
Limitations and Future Research
While this study provides strong evidence linking leg power to healthier cognitive ageing, several limitations should be acknowledged.
First, the cohort consisted exclusively of midlife and older women (ages 43–73 at baseline). The findings may not generalize to men, other ethnic groups, or individuals in later stages of life where additional ageing processes may play a stronger role (Steves, Mehta, Jackson, & Spector, 2016). Future studies should test whether these effects hold in more diverse populations.
Second, although the study included an impressive 10-year follow-up, the assessments of cognition were limited to two time points, restricting analysis to linear trends. More frequent testing would help clarify whether changes in leg power and cognition occur in parallel or whether one consistently precedes the other.
Third, while the study carefully controlled for genetics, early-life environment, and a wide range of health variables, the sample was composed of relatively educated women with above-average health status. This means results may not fully reflect the general population, particularly more vulnerable groups (Steves et al., 2016).
Fourth, the study did not directly compare leg power with aerobic fitness measures such as VO₂max, which have also been linked to brain health. While leg power may capture aspects of aerobic performance, future research should disentangle how muscular and aerobic fitness independently or jointly influence cognitive ageing.
Finally, the MRI sub-study was limited by small numbers (20 twin pairs). Although the results supported the main findings, larger neuroimaging studies are needed to confirm whether the observed differences in grey matter and brain activation are robust and replicable (Steves et al., 2016).
Looking forward, the authors suggest that interventional trials targeting leg power should be a priority. If long-term training designed to increase leg power can slow or even reverse cognitive decline, it would provide a practical and scalable strategy to promote healthy brain ageing in older adults.
Final Takeaway
This 10-year twin study delivers a powerful message: stronger legs mean a stronger brain. Among a wide range of health, lifestyle, and genetic factors, leg extensor power consistently emerged as the strongest predictor of healthy cognitive ageing. Women with greater leg power not only experienced less cognitive decline but also preserved more grey matter and healthier brain structures a decade later (Steves, Mehta, Jackson, & Spector, 2016).
Unlike genetics or early-life environment, leg power is something we can train and improve throughout life. This makes it a critical and modifiable target for both individuals and public health strategies. Exercises that build lower-limb power — from resistance training and sit-to-stands to brisk walking and step-ups — may do more than maintain mobility. They could also help safeguard memory, attention, and brain health well into older age.
As the researchers concluded, interventions aimed at improving leg power “may help reach a universal goal of healthy cognitive ageing” (Steves et al., 2016, p. 138). The message is simple but profound: if you want to protect your mind, don’t forget to train your legs.
Want to protect your body and your brain? Start building leg power today. If you’d like expert guidance, contact us at Prepare for Performance — we’ll help you train smarter for lifelong strength and cognitive health.
