Four Muscles that Decide How Well You Age

Forget the vanity muscles. These are the life-or-death muscles — and modern life is quietly destroying them.

Nobody is going to write a fitness magazine cover story about your soleus.

You will not find a social media influencer filming their tibialis anterior workout in slow motion. Nobody has ever flexed their spinal extensors for a selfie. And the gluteus maximus, while technically famous, is celebrated for entirely the wrong reasons — it is praised for how it looks in a pair of jeans rather than for what it does, which is keep you upright, mobile, and alive.

These four muscles — the gluteus maximus, the soleus, the spinal extensors, and the tibialis anterior — are the most functionally important muscles in the human body for anyone who wants to remain independent into their eighties and nineties. If they do not get the attention they deserve, they are the muscles that matter.

And modern life is dismantling them, hour by hour, of sitting at a time.

—

Here is an uncomfortable thought experiment.

Imagine your great-great-great-great-grandmother at 75. If she made it to 75 — which was far from guaranteed, given that the leading causes of death for most of human history were infection, childbirth, violence, and starvation rather than the chronic diseases that eventually get most of us now — she was almost certainly more functionally capable than the average 75-year-old sitting in a doctor’s waiting room today. Not because she had better genes, but because she had never stopped moving.

The Hadza people of Tanzania are among the last remaining hunter-gatherer populations on Earth. Research by anthropologist David Raichlen at the University of Southern California found that the Hadza spend about 75 minutes per day in moderate-to-vigorous physical activity. By comparison, US adults average about 64 minutes per week, not per day.

The Hadza also have exceptionally low rates of cardiovascular disease, obesity, and metabolic dysfunction. Notably, they do not appear to experience sarcopenia — the progressive muscle loss that affects an estimated 10 to 45 percent of older adults in industrialized nations — at rates comparable to those seen in modern populations.

The difference is not a supplement. It is not a protein shake. It is not a gym membership. It is the simple, brutal fact that their bodies must perform physical work every day to survive. Their muscles are used because not using them is not an option.

Ours is becoming more so each day.

—

The average adult in an industrialized country now spends between 9 and 12 hours a day sitting. Research tracking adults aged 65 and older found that an additional hour of daily sitting was associated with a six percent higher risk of sarcopenia. that each addit

Adults who sit more than eleven hours a day face more than double the risk of sarcopenia compared with those who sit fewer than four hours. The researchers also noted that recommended physical activity guidelines — 150 minutes of moderate exercise per week — did not fully offset the damage caused by sitting more than four hours a day. This is the part most wellness content overlooks.

You cannot exercise your way out of a sedentary lifestyle if your exercise is an hour every other morning, followed by eight hours in a chair. The body does not work that way. It keeps an honest account of what it is asked to do — and what is important: even meeting the rec is no longer required.

The muscles you stop asking for are the ones it stops maintaining. And the four it stops asking for first, in a modern sitting-dominant life, are exactly the four we need to pay attention to.

—

1. The gluteus maximus — the engine of everything

The gluteus maximus is the largest muscle in the human body. The headliner in the show. It is also, for today’s adults who sit for up to half the day, one of the most comprehensively underused. Sitting shortens the hip flexors at the front and simultaneously switches off the glutes at the back — a phenomenon physical therapists call, with admirable precision, gluteal amnesia. The muscle literally forgets what it is supposed to do.

What it is supposed to do is substantial. The gluteus maximus drives hip extension — the movement that propels you forward when you walk, powers you up a staircase, lifts you out of a chair, and stabilizes your pelvis and lower spine when you pick up your granddaughter.

When it doesn't work properly, the body compensates. The lower back takes on work it was not designed to handle. The knees track incorrectly and cry out for a rest. The hips lose range of motion. Falls become more likely. Recovery from them becomes harder, if possible at all.

The anthropological record makes clear that the pronounced enlargement of the gluteus maximus is a defining feature of human lower-limb anatomy — a structural adaptation to the demands of upright walking, running, and climbing that took millions of years to develop. We have spent roughly the last 100 years designing it out of the picture with office chairs, car seats, and sofas.

But it can be restored. Hip thrusts, glute bridges, deadlifts, step-ups, and — most simply — standing up and walking frequently throughout the day are the prescription. The glutes respond quickly when you give them a reason to exist.

—

2. The soleus — the second heart you didn’t know you had

The soleus is a broad, flat muscle in the lower leg, lying beneath the more visible gastrocnemius. It is not glamorous. It does not photograph well. It won’t make a potential romantic partner swoon. However, it does something extraordinary every time you stand upright: pumping blood back up from your legs to your heart against gravity, functioning as what some researchers call the peripheral heart.

The soleus is almost entirely made up of slow-twitch muscle fibres, which makes it highly resistant to fatigue and designed for sustained postural work. It is also, research has found, among the most metabolically active muscles in the body relative to its size — playing a significant role in blood glucose regulation.

A 2022 study from the University of Houston found that isolated soleus contractions performed while seated produced marked improvements in metabolic function — reducing blood glucose by 52 percent and insulin by 60 percent during the study period. The researchers described it as unlocking the muscle’s potential to improve metabolic health.

When you sit for hours, the soleus goes almost completely dormant. In older adults, when it goes dormant, circulation in the lower limbs suffers, sensory feedback diminishes, balance degrades, and the risk of a fall increases. The soleus is also, for reasons that are not yet fully understood, one of the muscles in which motor neuron excitability declines most significantly with age — meaning the neural connection between the brain and the muscle weakens, making coordination progressively less reliable.

Calf raises — particularly slow, controlled, full-range-of-motion calf raises performed on a step — are the most direct training stimulus for the soleus. Standing rather than sitting whenever possible is the most accessible intervention. Walking on inclined surfaces also trains the soleus well. This is one muscle where the investment-to-return ratio is extraordinary.

—

3. The tibialis anterior — the one that stops you falling

The tibialis anterior runs along the front of the shin and is responsible for dorsiflexion — the movement that lifts the front of your foot off the ground as you walk. Every step you take requires the tibialis anterior to fire: it clears your foot from the ground during the swing phase of gait and controls how quickly your heel contacts the floor during landing. Without it doing its job properly, the foot drops. The toe catches. You fall.

Falls are not a trivial concern. They are the leading cause of injury-related death among adults over 65 in both Canada and the United States. Hip fractures following falls carry a one-year mortality rate of approximately 20 to 30 percent in older adults. The tibialis anterior is one of the primary muscles involved in falls — and one of the primary muscles to target for prevention.

Research measuring electrical muscle activity found that the tibialis anterior shows among the most significant reductions in motor function with age of any lower limb muscle — including a 19 to 31 percent decrease in muscle activity during functional tasks in older adults. And yet it is almost never mentioned in mainstream fitness content. You are far more likely to hear about your biceps than about the muscle that is literally stopping you from tripping over a threshold and breaking your hip.

Training the tibialis anterior is simple and unfashionable: toe raises (lifting the front of the foot while the heel stays on the ground), walking on your heels, and single-leg balance work. None of these will go viral. All of them will quietly extend the period of your life during which you can walk without falling.

—

4. The spinal extensors — the reason you can look up

The spinal extensors are a group of muscles running along either side of the spine, responsible for keeping you upright, extending the back, and maintaining the posture that allows you to face the world rather than the floor. They work constantly whenever you are standing or moving, and they are under sustained, asymmetric load whenever you are sitting — which, if you are a modern adult, is most of the time.

Sitting, particularly in the slumped or forward-flexed position that most of us default to after the first twenty minutes in a chair, places the spinal extensors in a chronically lengthened and weakened position. Over years and decades, this produces the kyphotic posture — the forward rounding of the upper back — that is so common in older adults it has become culturally accepted as an inevitable consequence of aging. It is not inevitable. It is a consequence of what we do with our spines for eight to twelve hours a day. Add a laptop or cell phone to the equation, and we can see this condition showing up in much younger adults.

The postural consequences of weak spinal extensors extend well beyond appearance. Thoracic kyphosis compresses the chest cavity, reducing lung capacity. It shifts the centre of gravity forward, increasing the risk of falls. It places chronic load on the cervical spine. And it progressively limits the ability to look straight ahead — which, if you are navigating stairs, traffic, or uneven ground, is a meaningful safety concern.

Deadlifts, rows, Superman holds, and — most simply — the discipline of standing rather than sitting are the interventions. The spinal extensors are also among the muscles most directly trained by resistance exercise, since maintaining a neutral spine under load is their primary function. Every time you lift properly, you are training them.

—

The good news — and there is genuine good news here — is that all four of these muscles respond to training at any age. The research is consistent on this point: sarcopenia is not inevitable, and the muscles most at risk from modern sedentary life are also the most responsive to relatively modest, accessible interventions.

A 2025 systematic review of exercise interventions for adults with sarcopenia found significant improvements in neuromuscular function, physical performance, postural control, gait speed, stair-climbing ability, and grip strength across multiple resistance and multi-component training programmes. The minimum effective dose appears to be eight weeks. Most people will not believe that. The research does not care.

None of the exercises required to maintain these four muscles requires a gym. They do not require expensive equipment or a personal trainer. They require the decision — made repeatedly and consistently over time — to give these muscles a reason to remain.

Here is the simple programme to get you started:

Stand more. Sit less.

This is not a metaphor. It is the single most accessible intervention for anyone reading this. Break up sitting every 30 to 45 minutes. Stand while you read. Walk while you take phone calls. The soleus, the tibialis anterior, and the spinal extensors are postural muscles that do their best work when you are upright. Give them the opportunity.

Walk on varied terrain.

Flat, smooth surfaces are a modern invention and a functional disaster. Inclines train the soleus and gluteus maximus. Uneven ground trains the tibialis anterior and the ankle’s stabilizing muscles. Stairs train all four simultaneously. Find hills. Use them. Go for a hike outside to fire them all up, with the added bonus of brain health.

Train the posterior chain deliberately.

Hip thrusts and glute bridges target the gluteus maximus. Slow calf raises target the soleus. Toe raises and heel walks target the tibialis anterior. Deadlifts, rows, and back extensions target the spinal extensors. Two to three sessions per week. This does not need to take more than thirty minutes. It does need to happen.

Make getting off the floor a daily practice.

The ability to get up from the floor without using your hands is one of the strongest predictors of longevity in older adults. It requires all four of these muscles to work in coordination. Practise it. If you cannot do it, that is precisely why you should start.

—

Our ancient ancestors did not have a gym. They did not have protein powder, a recovery drink, or a foam roller. They had the daily, unavoidable requirement to use their bodies as the functional instruments they were designed to be.

Their gluteus maximus worked because walking across uneven terrain to find food was not optional. Their soleus worked because sitting in a chair for ten hours a day was not a concept - it was death. Their tibialis anterior worked because dropping a foot on a rock in the dark had consequences that did not include a hospital visit.

We have engineered necessity out of movement. We have replaced it with comfort, convenience, and respite. And we are experiencing, at the population level, the precise biological consequences of having done so for a very long time.

The wellness industrial complex has noticed. Unfortunately, it has responded by selling you products and programmes, and by promoting people with exceptionally low body fat percentages, demonstrating exercises that bear no relationship to the actual problem. Apart from the glute muscles, which appear to be trending on social media today for some of the wrong reasons.

The actual problem is simple. The actual solution is simpler. Use the muscles that keep you upright, stable, and mobile — deliberately, consistently, and starting now. Not because they will look good. Because they will help keep you independent and mobile well into your nineties.

As always, consult your physician or a qualified health professional before beginning a resistance training programme, particularly if you are managing existing conditions or returning to exercise after a period of inactivity. If you are currently working with a personal trainer or physiotherapist, ask them specifically about these four muscles. If they look confused, find a different one.

---

Research & sources referenced in this piece

Raichlen, D.A. et al. (2017). Physical activity patterns and biomarkers of cardiovascular disease risk in hunter-gatherers. American Journal of Human Biology. Hadza physical activity data: 135 min/day MVPA vs. 64 min/week for US adults.

Frail-LESS RCT (2024). Bailey, D.P. et al. The frail-LESS remote intervention to improve sarcopenia via reductions in sedentary behaviour. BMC Geriatrics, September 2024. Older adults in general population engage in sedentary behaviour for an average of 9.5 hours per day.

Ku, P.W. et al. (2025). Association of daily sitting time and leisure-time physical activity with sarcopenia among Chinese older adults. Nutrients / PMC11816827. Each additional hour of sitting associated with increased odds of sarcopenia; 4+ hours not fully offset by meeting activity guidelines.

Ponce-Bravo, H. et al. (2025). The Effects of Exercise Intervention in Older Adults With and Without Sarcopenia: A Systematic Review. PMC12115393. 11 RCTs, 792 participants, mean age 75.13. Significant improvements in neuromuscular function, gait speed, grip strength, and fall risk.

Hamilton, M.T., Hamilton, D.G. & Zderic, T.W. (2022). A potent physiological method to magnify and sustain soleus oxidative metabolism improves glucose and lipid regulation. iScience, 25(9), 104869. PMC9404652. DOI: 10.1016/j.isci.2022.104869. Full text: ncbi.nlm.nih.gov/pmc/articles/PMC9404652

Piasecki, M. et al. (2021). Intrinsic motor neurone excitability is reduced in soleus and tibialis anterior of older adults. Bioarxiv preprint. Reduction in motor unit excitability in soleus and tibialis anterior in older adults.

Abramowitz, M.K. et al. (2024). Sit-to-stand task and tibialis anterior. Cureus. 19.2% decrease in left TA and 31.2% decrease in right TA muscle activity in older adults performing functional tasks.

Raichlen, D.A. & Alexander, G.E. (2020). A hunter-gatherer exercise prescription to optimize health and well-being in the modern world. PMC7590991. Hunter-gatherers exercised out of necessity; modern lifestyle is systematically sedentary.

Shepherd, R.J. Health and fitness in prehistory. Springer Nature. Homo sapiens genetically adapted to prolonged endurance activity; energy expenditure sometimes exceeding 15 MJ/day in hunter-gatherers.