Not everyone can sleep through rumbling traffic or a spouse’s incessant snoring. If you do, you may pride yourself on being a “deep” or “heavy” sleeper.

If you struggle to fall or stay asleep, you may consider yourself a “light” sleeper.

But is there such thing as being a light or deep sleeper? And can you change how deeply you sleep?

Sleep is a cycle

Sleep is not a single, static state. Rather, it’s a cycle that unfolds and repeats across the night, in two main stages.

Stage 1: Non-REM sleep

Sleep begins with non-rapid eye movement sleep, also known as non-REM sleep. This is made up of three phases, ranging from a first phase of very light sleep, to the deepest and slowest form of sleep in the third phase.

Stage 2: REM sleep

Rapid eye movement or REM sleep comes next, usually between 80 to 100 minutes after you fall asleep. To distinguish between the two stages, scientists measure the size and speed of electrical activity in the brain, commonly known as brain waves. During this second stage, these brain waves become more active. This may be why you may have more dreams during REM sleep.

After your body completes its first round of non-REM and REM sleep, this process repeats in cycles, each lasting roughly 90 minutes.

The myth of the ‘deep sleeper’

When you’re sleeping, you may appear to be unresponsive. But your brain doesn’t fully switch off. Instead, your sleeping brain shifts into a “standby mode”, allowing it to monitor your environment while letting certain information through. This process is known as sensory gating. This is why you may wake up after hearing your own name, a familiar voice or a baby’s cries. All these sounds trigger a stronger response from your brain, compared to other ordinary noises.

During the second stage of non-REM sleep, your brain maintains this standby mode through two types of brain waves. The first type is known as sleep spindles. These are brief bursts of electrical activity that help reduce how much external information your brain processes at any given time. K-complexes are the second type of brain wave that, like sleep spindles, also help you sleep more soundly.

Research suggests you get the deepest sleep during the third stage of non-REM sleep. This is when your brain is the least responsive to the outside world. However arousability, which is how likely you are to wake from sleep, changes as you go through the sleep cycle. This means it’s not scientifically possible to be a “deep sleeper” for the whole night.

What other factors affect sleep?

Here are four other factors that can impact sleep quality.

Genetics

Certain genes may influence how you sleep. An example is a common variant of the adenosine deaminase gene. This gene affects how efficiently the brain clears adenosine. Adenosine is a chemical that, over the course of the day, accumulates in your brain and makes you more sleepy. People who carry this gene variant typically experience longer periods of deep sleep, particularly of the non-REM kind. This means they generally wake less during the night.

Research also suggests people with more sleep spindles may have better sleep. One 2010 study measured how many sleep spindles each participant produced while sleeping on a quiet night. Researchers found participants with a higher number of sleep spindles were more likely to stay asleep the next night, even when noise was introduced. Emerging evidence from studies of twins shows sleep spindles are highly heritable, suggesting genetics may play a role in how many sleep spindles a person produces.

Stress

For some people, stress can significantly impact their sleep. This trait is known as sleep reactivity. For these people, a stressful day can cause them to have racing thoughts and difficulty both falling and staying asleep. They may also experience night-time spikes of the hormone cortisol, which your body releases when you feel stressed. Current research suggests sleep reactivity is one of the strongest predictors of insomnia, a sleep condition where you consistently struggle to fall and stay asleep.

Light

Exposure to light may also affect sleep quality. One 2013 study compared the sleep patterns of healthy young adults who slept either with or without a bedside light. It found the former group had less deep sleep and more periods of being awake. These participants also produced fewer sleep spindles over the course of the night. Other research suggests night-time exposure to light may also delay the body’s internal clock, making it harder to fall asleep at bedtime.

Other medical conditions

People with certain medical conditions may struggle to sleep. One example is sleep apnoea, a common condition where your airway is partly or completely blocked during sleep. Research suggests people with untreated sleep apnoea wake up more often and experience more light non-REM sleep. But certain treatments can help to stabilise their breathing, improving sleep quality. Pain from other conditions, such as endometriosis and irritable bowel syndrome, can also impact a person’s sleep. People with these conditions often experience painful flare-ups at night, which research shows can limit deep sleep.

The bottom line

Many factors shape how much shut-eye you get each night. This means no one is truly a “deep sleeper”. But if you’re in need of a better night’s sleep, creating a dark, quiet and stress-free environment is a good place to start.

Kelly Sansom, Research Associate, College of Medicine and Public Health, Flinders University; Research Associate, Centre for Healthy Ageing, Murdoch University and Peter Eastwood, Deputy Vice Chancellor, Research and Innovation, Murdoch University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

If you’re feeling sore from a run or gym session, you might wonder whether it’s better to push through or give your body a rest.

This achy or stiff feeling in your muscles after exercise is known as “delayed onset muscle soreness” (DOMS). Soreness usually sets in within the first 12–24 hours after your exercise session, and often peaks 24–72 hours after.

In most instances, DOMS will disappear completely in three to five days. But what should you do in the meantime? Is it OK to exercise if you’re still sore? Here’s what the evidence says.

Why do muscles get sore after a workout?

When you exercise, tiny tears (also called “microtears”) occur in your muscles. Then, as your body floods the area with fluids and nutrients to repair them, it causes inflammation. This is part of the normal recovery process, and helps stimulate increases in muscle strength and size.

But inflammation also stimulates pain receptors, which makes you feel sore in the days after your workout.

How sore you feel will depend on the exercise you do. DOMS is more likely when you haven’t exercised for a while, you do a new type of exercise, or it puts a large load on your muscles (for example, weight training or running).

Basically, it’s your muscles’ response to doing something more demanding or challenging than usual.

The more often you do the same type of exercise, the less likely you are to feel sore.

Should you be sore after every workout?

Muscle soreness is completely normal, especially if you are new to exercise. But it’s not necessarily a good indicator of progress.

All it really tells us is that our body is adapting to a new form of exercise or a sudden increase in load.

It doesn’t tell us whether or not that exercise was effective at building muscle and improving fitness – especially if you’ve been exercising consistently and gradually increasing your load or frequency.

For example, someone who runs regularly is unlikely to feel sore after a single running session, but it will still improve their fitness.

Similarly, if you lift weights regularly, using heavier weights than usual will at most give you only mild DOMS. Yet each training session will still be helping you improve strength and build muscle.

So, should I exercise if I am still sore?

It depends if you’re concerned about injury or performance.

Exercising while recovering from DOMS won’t hurt you. But some evidence suggests your strength and performance may decline when you’re sore. This means you probably won’t be able to lift as much or run as fast while you have DOMS.

Some research has also shown that muscle damage can negatively affect balance. This might increase your risk of falling or even getting an injury such as a sprained ankle.

Another study found soreness can also reduce your skill performance (in this case basketball shooting accuracy). So you might notice an impact if you’re exercising with certain performance goals in mind.

What about rest days?

Taking days off for recovery in between exercise sessions doesn’t seem to make much difference for long-term progress building strength or fitness.

Research has compared training on consecutive days – for example, Monday, Tuesday and Wednesday – with non-consecutive days – Monday, Wednesday, Friday.

And it doesn’t seem to make a difference.

For example, one study had two groups perform the same full-body weight training routine for seven weeks, either on three consecutive or three non-consecutive days. Both groups saw similar improvements in building muscle strength and size.

Similarly, another study compared two groups of cyclists doing the same high-intensity interval training program routine on three consecutive or three non-consecutive days. After three weeks both groups showed the same overall improvements in aerobic fitness and time trial performance.

These were relatively short-term studies. So it’s also possible that over the course of a training year, taking a rest day here and there will help maintain motivation and avoid injury.

Bottom line

While you’ll probably feel slower or stiffer, exercising with sore muscles won’t hurt you and is unlikely to hinder your training progress.

However, you might want to avoid exercises that rely on balance – such as intense jumping and landing movements – as your risk of injury could be slightly greater.

If you are really sore, there is some evidence massage or even an ice bath might help you recover, although the effect is small.

And while muscle soreness is normal, it’s still important to listen to your body. Never push through intense discomfort or pain, as this could be the sign of an injury.

You should talk to a doctor if:

• your muscles feel extremely sore and it lasts for more than seven days
• you have visible muscle bruising where the muscle is sore
• you have sharp pain.

Hunter Bennett, Lecturer in Exercise Science, University of South Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.