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Permalink Reply by Dr. Krishna Kumari Challa on August 20, 2026 at 9:03am

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Why you move—not just how often—could affect dementia risk

For years, scientists have known that regular physical activity can help lower the risk of dementia. But new  research suggests that it's not only the amount but also the activity's context—for work or for leisure—that makes a difference.

A meta-analysis of more than 4.2 million people has found that leisure-time exercise—activities such as walking, cycling, running, swimming or playing sports—is associated with a substantially lower risk of dementia. In contrast, physical activity performed as part of a job appears to be linked with a higher risk of developing the condition.

The findings, published in The Lancet Public Health, are the first to systematically examine whether the so-called "physical activity paradox" extends to dementia. This paradox, well documented in cardiovascular research, describes the surprising observation that physically demanding jobs do not provide the same health benefits as voluntary exercise—and may even increase disease risk.

Researchers  analyzed data from 74 cohort and case-control studies involving more than 4.2 million participants ages 45 to 93 across 30 countries. Participants were followed for a median of 10 years, during which investigators tracked diagnoses of all-cause dementia, Alzheimer's disease and vascular dementia.

Overall, people who engaged in higher levels of leisure-time physical activity had a 24% lower risk of dementia than those who were least active. Household physical activity also appeared beneficial, although evidence came from only a single study. By contrast, occupational physical activity was associated with a 20% higher risk of dementia, while active commuting showed a modest increase in risk, though those findings were based on just two studies.

The findings challenge the long-held assumption that 'every move counts' for brain health. 

"Physical activity" often combines exercise, manual labor, housework and commuting into a single measure. But according to the researchers, these different forms of activity occur under very different circumstances and may have distinct effects on long-term health.

Leisure-time exercise is typically self-directed, can be performed at an enjoyable intensity and is often accompanied by social interaction or stress reduction. Physically demanding jobs, on the other hand, may involve repetitive tasks, prolonged standing, heavy lifting, limited recovery time and exposure to workplace hazards.

The authors argue that the apparent harms associated with occupational activity are unlikely to be caused by movement itself. Instead, they may reflect the broader social and environmental conditions that often accompany physically demanding work.

Manual occupations are more likely to involve psychosocial stress, lower job control, hazardous working conditions and greater exposure to air and noise pollution, all factors that have independently been linked to dementia risk. Workers in these jobs may also have fewer opportunities for recreational exercise because of time constraints, fatigue or limited access to safe places for physical activity.

Leisure-time exercise and occupational physical activity exhibited contrasting nonlinear associations with dementia risk. Higher levels of leisure-time exercise were associated with progressively lower dementia risk until the association plateaued, whereas higher levels of occupational physical activity were associated with progressively greater dementia risk before also plateauing.

The authors note that evidence remains sparse for household and commuting activity, preventing firm conclusions about those domains. Likewise, most of the available research came from high-income countries, even though low- and middle-income countries are expected to experience the largest increases in dementia cases over coming decades.

Researchers caution that the results do not mean people should avoid physically active jobs. Because the analysis is based on observational studies, it cannot prove that occupational activity causes dementia. Instead, the findings highlight the importance of considering the context in which physical activity occurs. Leisure-time activity remained protective, while occupational activity remained associated with elevated dementia risk even after accounting for age, education and chronic diseases.

Domain-specific physical activity and the risk of dementia: a systematic review and meta-analysis with 4 million participants, The Lancet Public Health (2026).

Permalink Reply by Dr. Krishna Kumari Challa on September 4, 2026 at 11:30am

What is post‑workout fatigue, and can you prevent it?

You finish a workout feeling pleased with yourself. But an hour later, your legs feel heavy, climbing the stairs seems impossible and all you want to do is sit down.

The feeling of being drained after a tough workout is often described as "post-workout fatigue". You might feel low on energy, while your muscles may feel heavy, weak or less able to perform.

While some tiredness after exercise is normal, how much you experience can depend on the type of workout you've done, how hard you've worked and how accustomed your body is to it. Fortunately, there are things you can do to help your body recover.

What is post-workout fatigue?

There are two sides to fatigue. The first is perceived fatigue, which is your own feeling of tiredness and effort. The second is performance fatigability, which refers to a measurable drop in what your body can do—such as a muscle being unable to produce as much force.

The two don't always match perfectly, which is why fatigue is now understood as a complicated process involving both the body and our perception of tiredness.

Fatigue is also different from delayed-onset muscle soreness (DOMS)—the aching and stiffness that can develop after working out. DOMS typically happens if we've done an unfamiliar exercise or if it's been a while since we last exercised.

DOMS is also particularly associated with eccentric exercise (when a muscle works while getting longer)—such as when lowering a dumbbell.

Why does post-workout fatigue happen?

There isn't one single cause. Different processes contribute depending on what exercise you've done, how hard you've worked and for how long.

Some of this fatigue may be caused by changes that happen inside the muscles, for example.

For our muscles to move during exercise, they rely on electrically charged particles called ions, which trigger muscle contractions. But exercise also causes changes to these ions, which can affect the muscles' ability to contract and produce force later in a workout. This may explain why people feel like their muscles are depleted and fatigued after a workout.

The nervous system plays a part, too. The brain and spinal cord send signals telling our muscles to contract. Strenuous exercise can temporarily reduce the nervous system's ability to fully activate the muscles, contributing to what is sometimes called central fatigue.

Fuel is another factor, particularly during longer or demanding exercise. Our muscles store carbohydrates from the foods we eat to use later for energy. But exercise reduces these stores, which can contribute to fatigue.

Sweating also causes us to lose water and electrolytes, such as sodium, which are important for keeping our muscles and nerves working normally. If enough fluid is lost without being replaced, dehydration can reduce performance and make physical activity feel harder.

Is it worse if you're new to exercise?

People new to exercise may experience more soreness and muscle weakness because their bodies aren't accustomed to the activity. However, even experienced exercisers can experience it—particularly when they try something unfamiliar. For example, a regular runner who rarely lifts weights may feel very sore after their first challenging weight-training session.

Fortunately for us, the body adapts. Repeating similar exercises generally causes less muscle damage and soreness—something scientists call the repeated-bout effect. A 2023 review found less muscle soreness and better preservation of physical performance after a second bout of muscle-damaging exercise compared with the first.

So, post-workout fatigue isn't just a beginner's problem.

How can you recover?

Some of the most useful recovery strategies are also the simplest: food, fluids, sleep and time.

After a long or demanding workout, eating carbohydrates helps replace the energy stores our muscles have used.

Protein is also important. Protein provides amino acids, which the body needs to adapt and recover from the exercise we've just done. However, protein supplements certainly aren't an instant cure for tired or aching muscles—and research into their effects on soreness and immediate recovery has produced mixed results.

Replacing the fluid we've sweated out is also important. For most shorter workouts, water is enough. But if you've done a long run, an intense workout session or have sweated a lot (such as during hot weather), you may want to consume some electrolytes as well.

Sleep is important because it gives the body further opportunity to recover. Research in athletes suggests that increasing sleep, either by sleeping longer at night or taking naps, may benefit aspects of physical and mental performance.

There's also some evidence for alternative recovery techniques, including gentle exercise (such as a slow walk or yoga), massages and water immersion. A review of 99 studies found several of these techniques could reduce muscle soreness, with massage showing one of the strongest effects on people's feelings of fatigue.

Can you prevent it?

You can't. But if you want to reduce how bad your post-workout fatigue is, try to avoid suddenly doing much more than your body is prepared for.

Starting a new activity at a manageable level and gradually building up gives your body time to adapt.

Making sure you're well hydrated before workouts is also sensible—particularly for longer workouts or when exercising in hot conditions.

Eating enough to support your activity and allowing time to recover between demanding workouts helps as well.

Most importantly, feeling completely exhausted doesn't necessarily mean you've had a better workout. Some fatigue is expected, but it should generally be in proportion to the exercise you've done and improve with recovery.

If the amount of fatigue you experience after a workout seems disproportionate to the workout you've done, doesn't improve with recovery or comes with symptoms such as chest pain, fainting or unusual breathlessness, speak to a doctor.

This article is republished from THE CONVERSATION under a Creative Commons license. Read the original article.

Author: Athalie Redwood-Brown

Permalink Reply by Dr. Krishna Kumari Challa 1 hour ago

Why 'accidents' can happen during intense exercise
Intense, prolonged exercise can trigger diarrhea and other gastrointestinal symptoms by diverting blood from the gut to muscles, reducing intestinal oxygen delivery and impairing water absorption. Repetitive impact and increased abdominal pressure can further injure the gut lining and promote urgency; severe or recurrent symptoms may involve bleeding or exercise-induced gastrointestinal syndrome.
There are very few downsides to exercise. But a recent viral story highlighted one of the more embarrassing—and potentially dangerous—issues that can occur when your body reaches its limit during exercise.

Joanna Wietrzyk, the winner of the recent women's pro Hyrox race in Beijing (a challenging fitness race that blends running and strength), found herself in the spotlight not for her performance—but because she soiled herself during the event.

While there has been plenty of commentary about what happened—and discussions over whether she should have been allowed to continue competing—such occurrences are not uncommon among athletes.

Those who watched the 2005 London Marathon will remember Paula Radcliffe stopping at the 22-mile (35-kilometer) mark to "do her business" on the side of the road. Triathlete Taylor Knibb also suffered a similar incident during the 2024 Dubai T100.

Gastrointestinal problems, including diarrhea, are up to three times more common in professional athletes than in recreational athletes. The impact on runners is so common that it even has its own term: runner's diarrhea. It's estimated that up to 90% of runners experience this issue at some point.

But diarrhea isn't the only symptom people undertaking strenuous exercise for a prolonged period may experience. Abdominal pain, heartburn, nausea, vomiting and even gastrointestinal bleeding may all occur.

There are a few key reasons why intense exercise can have such a detrimental effect on our gastrointestinal system.

The first has to do with the digestive tract itself. The human digestive tract is approximately three times our height. This means it contains a lot of material. It also means our digestive tracts are rarely empty. This is particularly true when people are doing long or intense forms of exercise, when they may need to consume pre-workout snacks or drinks to give them energy, alongside fluids or gels during exercise to keep going.

If any problems occur with food when it's in the stomach, it usually goes back out the way it came in. But if any issues occur with food once it leaves the stomach, it's a one-way ticket "downward."

The small and large intestines hold approximately 300 mL and 600 mL of liquid content at a time—although this varies from person to person. So you can perhaps see why it can be difficult to stop problems when they arise during exercise.

The second factor relates to blood flow. Our bodies have a limited amount of blood—around five liters on average—which is circulated around the body. Whatever activity we're doing changes the distribution of blood around the body. When we exercise, nervous and hormonal signals tell the blood vessels in the muscles and lungs to dilate, increasing the amount of blood flowing to them.

The same signals that cause those vessels to dilate also tell vessels leading to the gastrointestinal system to constrict. This temporarily reduces blood flow to these organs.

A reduction in blood flow to the intestines during endurance exercise can cause bowel ischemia. This is where the blood supply to the organ is reduced so much that it can no longer function properly due to insufficient oxygen and nutrients. Standard exercise doesn't usually cause this, but prolonged and intense exercise increases the risk.

This reduction in blood flow has been shown to cause symptoms such as diarrhea in athletes. In rare cases, it can also result in bowel blockages.

A prolonged reduction in blood flow, oxygen and nutrients to the intestines can also damage the cells that line the gut. These cells are responsible for absorbing nutrients and water into the bloodstream, meaning performance is impaired and dehydration may occur.

The physical effects of intense exercise also cause problems. Our gastrointestinal contents are repeatedly sloshing around with the impact of every step, jump or lunge. This not only places additional force on our gastrointestinal system but also causes physical microtrauma to the tract's lining, which can sometimes result in intestinal bleeding.

Thankfully, the lining of the intestines has a good capacity for regeneration, so long-term issues are rare. But if microtrauma and intestinal bleeding occur frequently, they can lead to a "leaky gut", where the contents of the gastrointestinal tract (including partially digested food, pathogens and bacterial toxins) can leak into the bloodstream.

This can lead to a systemic immune response, resulting in pain, cramping and diarrhea—a condition referred to as exercise-induced gastrointestinal syndrome (EIGS).

Once the body decides that it doesn't want the contents in the intestines anymore, it has limited power to stop what comes next. This is despite the fact that the body has two anal sphincters—an internal one and an external one—which work in tandem to stop the gastrointestinal tract from emptying when we're not ready.

Once enough pressure has built in the gastrointestinal tract, you will experience an urge to "go." And in the context of Hyrox, the running, pushing, lunging and lifting competitors perform exacerbate the pressure that may already naturally be happening in the gastrointestinal tract.

Wietrzyk's "accident" isn't as uncommon as people may think. As four-time Boston and New York marathon winner Bill Rodgers put it: "More marathons are won or lost in the porta-toilets than at the dinner table." Wietrzyk's story is just the latest example of the toll competing at an elite level can have on your body.

This article is republished from THE CONVERSATION under a Creative Commons license. Read the original article.

Author: Adam Taylor