We have all seen movies where right before the hero starts fighting, he cracks his knuckles and makes it look like the coolest thing in the world! But then our parents told us that you should not crack your knuckles because that weakens your grip and hand strength. But is that true? While many people do say that they experience a small loss in strength immediately after they crack their knuckles, but are their long-term effects to it? And what is the sound actually coming from?

The reason why people crack their fingers is because the evident and sharp crack noise causes a sense of relief. Many people also do it when they have done an activity that required them to work with their hands a lot like typing or sewing, giving themselves a sense of satisfaction, similar to stretching after doing hard work. That "crack" sound can make some people cringe, while others find it strangely satisfying. Cracking your knuckles is a pretty common habit, but there are a lot of misunderstandings about it. Some people do it without even thinking, others can't stand the noise, and some can't crack their knuckles at all. You might have been told as a kid that it causes arthritis or makes your fingers swell up. But those are just old wives' tales. There's a real science behind this habit, and it's more interesting than you may think.

Why Do Knuckles Make That Popping Sound?

The "crack" isn't actually bones breaking or anything bad happening to your joints. It's a normal thing called "crepitus." This just means harmless popping, snapping, or grinding sounds that come from your joints. The main reason you hear this sound is because of gas bubbles in the fluid that cushions your joints. This fluid is called synovial fluid. When you move or stretch, these tiny bubbles form and then pop, making the sound. It's totally normal and doesn't hurt you. Sometimes, especially in bigger joints like your knees, shoulders, or ankles, the sound can also happen when the stretchy tissues that connect your bones (ligaments and tendons) move slightly and then snap back into place.

After you crack your knuckles, you can't usually do it again right away. You have to wait a bit. That's because the gas bubbles in your joint fluid have already popped, and it takes a little while for them to build up again. While cracking your knuckles doesn't give you arthritis, doing it too much might cause some problems. Doctors say that cracking them too often could make your joints a little wobbly and might even make your grip weaker. Also, if the stretchy tissues in your joints keep snapping over your bones, they can get irritated and sore.

When Joint Popping Might Mean Something More

Sometimes, a pop in your joint is just like cracking your knuckles, nothing to worry about. But other times, it can be a sign of something else. As we get older, the cushiony stuff in our joints, called cartilage, can start to wear down. This cartilage helps your bones move smoothly. When it gets thin or uneven, the bones can rub together, and that can make a grinding or popping sound. This is different from the pop you get from gas bubbles. If this grinding sound happens along with pain, it could be a sign of osteoarthritis. This is a type of joint problem that's more common in older people, but younger people can get it too, especially after a joint injury. If your joints hurt, especially in the morning or after you've been sitting still for a while, feel wobbly, or are hard to move, it's a good idea to see a doctor.

Cardiac arrest is considered one of the most urgent medical situations. It can occur unpredictably, at home, at work, while traveling, or anywhere. It is characterized by a blockage in the heart's arteries, and it differs from a heart attack, which is a situation when the heart stops pumping blood into the body. After a few minutes, oxygen deficiency happens and affects the brain and other organs. Therefore, it is important to know how to perform cardiopulmonary resuscitation (CPR).

CPR is an emergency lifesaving technique that uses chest compressions and, in some situations, blowing mouth-to-mouth air into the person who has suffered a cardiac arrest, to help maintain blood circulation and oxygen delivery to vital organs when a person's heart has stopped beating effectively. It does not restart the heart by itself, but it can keep blood flowing until an automated external defibrillator (AED) is available or emergency medical professionals arrive.

Importantly, CPR is not a skill limited to doctors or healthcare professionals. It can be administered by ordinary people for whom learning the basic CPR techniques is easy.

The Importance of Rapid and Efficient Actions in Case of Cardiac Arrest

If someone faces cardiac arrest, rapid actions may save this person's life. If CPR is performed directly and immediately after a cardiac arrest, it will be possible to keep the flow of blood to the brain and other organs before the arrival of medical experts. The use of CPR can improve the chances of survival for patients who have experienced cardiac arrest.

Besides, in combination with early defibrillation through an AED, it can be even more effective. AED is a portable medical device that checks the heart rhythm of the person experiencing cardiac arrest and delivers an electric shock to restart a normal heartbeat.

However, sometimes people prefer to do nothing for fear of mistakes. But it is much more dangerous not to act at all.

Recognizing Cardiac Arrest

It begins with identifying the presence of a possible cardiac arrest in the patient. The patient will generally fall, become unconscious, and will not breathe properly. They can occasionally breathe abnormally with strange sounds, which should not be considered breathing properly.

If you see anyone fall and become unresponsive, check whether they respond to your questions and breathe normally. Tell any passerby to call the emergency services and bring an AED device, if one is present. If the patient is not breathing normally, initiate CPR on them.

What To Do?

If the patient is an adult, hands-only CPR can be done easily by everyone. For this, you need to keep the heel of one of your hands in the center of the person’s chest, keep your other hand over it, and press down with a rapid rhythm. The compression must be continued at a pace of around 100-120 beats per minute.

Also, you can use the AED device if one is available. Turn on the AED and follow the steps according to the voice prompts from it. The AED device will analyze the rhythm of the heart and give a shock.

CPR is a Practical Skill, not Just Medical Knowledge

Another reason for reluctance to administer CPR is the notion that it should be administered only by doctors, nurses, and other professionals. However, even basic CPR can be taught to regular citizens using special courses. It takes only a couple of hours of practice for someone to gain enough confidence to use CPR in emergencies.

CPR training should be more accessible in schools, offices, and residential communities, as it would help people know what to do in those critical first few minutes.

Cardiac arrest will not wait for doctors to show up. When cardiac arrest occurs, the first person on the scene might be either a relative, co-worker, friend, or a total stranger. Knowing CPR will prepare you for these moments of life or death. A simple skill learned today may help save someone’s life tomorrow.

(Dr. Lalit Kapoor, Senior Consultant - Cardiac Surgery and Robotic Surgery – Narayana RN Tagore Hospital, Mukundapur, Kolkata)

Worried about your graying hair? It may reflect a natural cellular response to DNA damage, according to a study by Japanese researchers.

Hair color comes from melanocyte stem cells (McSCs), which live inside hair follicles and produce melanin, the pigment responsible for hair and skin color. These cells are especially sensitive to DNA damage from environmental and internal factors.

While DNA damage is linked to both aging and cancer, researchers at the University of Tokyo found that McSCs can take different paths after being damaged — including one that leads to hair graying and another associated with melanoma, a type of skin cancer.

How Does Gray Hair Act As A Defense?

When McSCs suffer certain types of DNA damage, they can undergo a process called senescence-coupled differentiation, or seno-differentiation. The damaged stem cells permanently differentiate and are eventually lost, leading to hair graying.

This response is driven by the p53–p21 pathway and may help eliminate damaged cells before they can become cancerous.

Also read: Unusually High Cancer-Fighting Immune Cells Could Explain Why Some People Live Beyond 100: Study

What Did The Study Find?

Published in Nature Cell Biology, the study examined how McSCs respond to different types of DNA damage.

Professor Emi Nishimura and Assistant Professor Yasuaki Mohri used long-term in vivo lineage tracing and gene-expression profiling in mice to study the fate of these stem cells.

The researchers found that DNA double-strand breaks triggered seno-differentiation. In this process, damaged McSCs irreversibly differentiate and are lost, resulting in hair graying.

However, the response was different when the cells were exposed to certain carcinogens, including 7,12-dimethylbenz(a)anthracene, or ultraviolet B. In these situations, McSCs could bypass the protective differentiation process, retain their ability to self-renew and expand clonally.

This process was supported by KIT ligand signals from the surrounding tissue and epidermis, which suppressed seno-differentiation and pushed the cells toward a tumor-prone state.

“These findings reveal that the same stem cell population can follow antagonistic fates—exhaustion or expansion—depending on the type of stress and microenvironmental signals,” Nishimura said.

“It reframes hair graying and melanoma not as unrelated events, but as divergent outcomes of stem cell stress responses,” she added.

Does Gray Hair Prevent Cancer?

Read More: Ferritin Face: Can Pale Skin Signal Iron Deficiency?

Not necessarily. The study does not show that people with gray hair have a lower risk of cancer.

Instead, the findings suggest that hair graying can be the result of a protective cellular response in which damaged stem cells are eliminated. When that response is bypassed, damaged McSCs may persist and contribute to melanoma development.

The researchers say the findings offer a framework for understanding how the same stem-cell population can contribute to either tissue aging or cancer depending on the type of damage and signals from the surrounding environment.

Can You Prevent Premature Graying?

Genetics plays a major role in when hair turns gray. There are also some lifestyle changes that can prevent graying, support hair and overall health. These include:

• Managing stress
• Eating a nutrient-rich diet
• Protecting your hair and scalp from excessive UV exposure
• Avoiding excessive heat and harsh chemical treatments
• Avoiding smoking.

An Alzheimer’s patient may vividly remember their wedding day from 40 years ago, remember the house they grew up in or sing a song they learned in childhood, but still struggle to remember what they ate for breakfast or a question they were asked just an hour ago.

So if Alzheimer’s is a memory loss disease, why do some old memories appear to remain intact while recent ones disappear so quickly?

According to leading experts, the answer lies in the way different memories are formed, stored and retrieved in the brain. It is also in the fact that Alzheimer’s does not damage every memory system at the same speed. This means that the ability to form and retain new memories can become impaired before older memories are affected.

“In Alzheimer’s, memory loss does not always happen evenly. The brain regions responsible for forming and storing new memories, particularly the hippocampus and surrounding areas, are often affected early,” Dr K K Jindal, Director, Neurology, CK Birla Hospital, Delhi, told HealthandMe.

Recent Memories Disappear First

A person with Alzheimer's disease may remember a marriage, childhood home or an event from 40 years ago, but not remember a meal or conversation from an hour earlier. To understand this, it helps to look at what happens when a new memory is formed.

Dr Praveen Gupta, Chairman, Marengo Asia International Institute for Neuro and Spine, Marengo Asia Hospitals, Gurugram, told HealthandMe, “The memories that Alzheimer’s erodes do not deteriorate at equal rates. One of the first brain functions to be compromised is the creation of new memories. This is because the older memories have enough time to spread their representations in the brain while the newer memories rely on memory circuitry that is very vulnerable.”

Dr Saurav Aggarwal, Consultant, Neurology, Fortis Hospital, Ludhiana, explained the process to HealthandMe through the concept of memory consolidation. He said when a person experiences something new, the memory initially depends heavily on the hippocampal network.

Dr Aggarwal said, “Old memories go through consolidation, where the brain spreads a memory across the cortex, its outer layer, including the temporal and frontal lobes. Years of retelling strengthen those links.”

By contrast, new memories remain heavily dependent on the hippocampal network. “Alzheimer's damages the hippocampus first, so the brain fails to consolidate new information, such as a memory from the morning or a few hours ago, causing it to fade” Dr Aggarwal says.

Older memories have therefore had years, sometimes decades, to become more represented and strengthened through repetition and recall. New memories do not have that advantage.

Also read: Donald Trump Wants Childhood Vaccines Split Into 5 Shots To Prevent Autism: But Is There Evidence?

The Hippocampus Is More Than The Brain's Memory Bank

The hippocampus is not just a storage box for memories. It plays a crucial role in organising and absorbing new experiences. Dr Aggarwal describes it as a “sorting desk”.

He says, “The hippocampus works like a sorting desk. It takes in new experiences, a step called encoding, and passes them to the cortex for storage, meaning that proper memories cannot be formed if the hippocampus is damaged.”

The hippocampus is particularly vulnerable in Alzheimer’s disease. According to Dr Aggarwal, two abnormal proteins are central to the disease process.

“Two abnormal proteins drive this damage. Amyloid forms plaques between neurons, and tau twists into tangles inside them,” Dr Aggarwal says. “Tangles appear first in the entorhinal cortex, the hippocampus's gateway. They spread inward and, with amyloid plaques, damage the connections between neurons (synapses).”

Dr Steve Paul Manjaly, Geriatric Medicine, Apollo Hospitals, Bangalore, told HealthandMe that the hippocampus has a high level of synaptic transmission, which makes it particularly vulnerable to toxic processes linked with Alzheimer’s disease.

He explains, “The hippocampus is the seat of memory and has high synaptic transmissions, making it prone to toxicity,” he says. “Also the pathology is such that the affect the networking pathways that affect the hippocampus majorly.”

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All Memories Are Different

One important misconception about Alzheimer’s is that there is one single type of memory that simply gets weaker over time. In reality, the brain uses several memory systems, and they can be affected at different stages.

“There is no single memory system; the three different types of memory systems are episodic memory, semantic memory, and procedural memory,” says Dr Gupta.

Episodic memory refers to personal experiences. For example, what happened yesterday, where a person went, or what they discussed during a particular conversation. This is affected earlier.

Semantic memory involves facts, information, words and their meanings. “Semantic memory is about names. E.g Delhi is the capital of India. This is affected much later in Alz,” Dr Manjaly explains.

Procedural memory is the memory of how to perform learned skills. “Procedural memory is about how something was learned. E. G driving a cycle etc. This is affected later in the disease,” he says. This is why someone with Alzheimer’s may forget what they had for lunch but still be able to tie their shoelaces or perform a familiar skill.

Also read: Scientists Grow Human Brain Tissue Inside Mice: Could This Help Cerebral Palsy, Epilepsy & Autism Research?

Why Can A Patient Sing An Old Song But Forget A Person's Name?

One of the most striking and fascinating examples of preserved memory in Alzheimer’s is music. Families of people with dementia often notice that a loved one who struggles to remember names or recent conversations may still be able to sing an old song almost perfectly.

Songs are encoded through more than their words. Rhythm, melody, repetition, emotion and long-established associations all contribute to how they are represented in the brain.

“The various types of memories involve different neural networks,” says Dr Gupta. “Songs we know are not just about words; songs have associations with rhythm, emotions, repetition, and neural links that have been created since ages.”

Dr Aggarwal notes that procedural skills involve structures such as the basal ganglia and cerebellum, which tend to be affected later in Alzheimer’s disease.

Musical processing also involves several networks beyond the hippocampus, some of which may remain relatively preserved. This helps explain why familiar routines, songs and well-practised skills can sometimes survive long after the ability to form new memories has deteriorated.

Also read: 1 In 4 Doctors Near Retirement Age By 2036: WHO Warns Of Global Health Workforce Crisis

When Is Forgetfulness More Than Normal Ageing?

Forgetting sometimes is not, by itself, evidence of Alzheimer’s disease. With normal ageing, people may take longer to retrieve a name, need more time to learn something new or occasionally forget something, and remember it later. The more important warning signs are progression, frequency and impact on everyday functioning.

Dr. Gupta explains, “What matters most is not that they are forgetting but the frequency with which it occurs, that it is becoming progressively more problematic, and that it starts to interfere with daily functioning.”

According to the experts, warning signs may include:

• Repeatedly asking the same question within a short period
• Forgetting conversations or events that happened recently
• Getting disoriented in familiar places
• Misplacing objects and not being able to retrace one's steps
• Struggling with familiar recipes
• Having difficulty managing finances or medications
• Developing problems with words or understanding conversations
• Showing poorer judgement or decision-making
• Becoming increasingly dependent on family members for tasks previously handled independently

How Do Doctors Determine Whether Memory Loss Is Due To Alzheimer’s?

According to the doctors, Alzheimer’s diagnosis begins with a detailed history, including when the symptoms started, how they have progressed and how they affect daily functioning.

Information from family members can be particularly important because a person experiencing memory impairment may not recognise the extent of the changes.

“Now, the diagnosis of Alzheimer's is not just about memory tests,” says Dr Gupta. “We utilize a comprehensive assessment along with high-tech investigation methods like serum markers and PET scanning to find out the presence of biological markers of Alzheimer's disease.”

Besides memory loss, several medical conditions can produce symptoms that resemble dementia. Vitamin B12 deficiency and thyroid disorders can contribute to cognitive problems and need to be considered.

Experts say that blood tests can help identify such reversible contributors, while an MRI can look for strokes and patterns of brain shrinkage.

“MRI scans and pet scans can help narrow it down further and help sometimes in ruling out other causes of cognitive impairment,” Dr Manjaly says. “Thyroid and vitamin b12 deficiencies are also conditions that may mimic dementia.”

Modern diagnosis can also go beyond symptoms and structural imaging. Dr Aggarwal says amyloid PET imaging and cerebrospinal fluid testing can provide additional evidence of Alzheimer’s pathology by detecting abnormal protein changes associated with the disease. The exact combination of tests depends on the individual patient and overall clinical situation.