We’re all time-poor, so multi-tasking is seen as a necessity of modern living. We answer work emails while watching TV, make shopping lists in meetings and listen to podcasts when doing the dishes. We attempt to split our attention countless times a day when juggling both mundane and important tasks.

But doing two things at the same time isn’t always as productive or safe as focusing on one thing at a time.

The dilemma with multi-tasking is that when tasks become complex or energy-demanding, like driving a car while talking on the phone, our performance often drops on one or both.

Here’s why – and how our ability to multi-task changes as we age.

Doing more things, but less effectively

The issue with multi-tasking at a brain level, is that two tasks performed at the same time often compete for common neural pathways – like two intersecting streams of traffic on a road.

In particular, the brain’s planning centres in the frontal cortex (and connections to parieto-cerebellar system, among others) are needed for both motor and cognitive tasks. The more tasks rely on the same sensory system, like vision, the greater the interference.

This is why multi-tasking, such as talking on the phone, while driving can be risky. It takes longer to react to critical events, such as a car braking suddenly, and you have a higher risk of missing critical signals, such as a red light.

The more involved the phone conversation, the higher the accident risk, even when talking “hands-free”.

Generally, the more skilled you are on a primary motor task, the better able you are to juggle another task at the same time. Skilled surgeons, for example, can multitask more effectively than residents, which is reassuring in a busy operating suite.

Highly automated skills and efficient brain processes mean greater flexibility when multi-tasking.

Adults are better at multi-tasking than kids

Both brain capacity and experience endow adults with a greater capacity for multi-tasking compared with children.

You may have noticed that when you start thinking about a problem, you walk more slowly, and sometimes to a standstill if deep in thought. The ability to walk and think at the same time gets better over childhood and adolescence, as do other types of multi-tasking.

When children do these two things at once, their walking speed and smoothness both wane, particularly when also doing a memory task (like recalling a sequence of numbers), verbal fluency task (like naming animals) or a fine-motor task (like buttoning up a shirt). Alternately, outside the lab, the cognitive task might fall by wayside as the motor goal takes precedence.

Brain maturation has a lot to do with these age differences. A larger prefrontal cortex helps share cognitive resources between tasks, thereby reducing the costs. This means better capacity to maintain performance at or near single-task levels.

The white matter tract that connects our two hemispheres (the corpus callosum) also takes a long time to fully mature, placing limits on how well children can walk around and do manual tasks (like texting on a phone) together.

For a child or adult with motor skill difficulties, or developmental coordination disorder, multi-tastking errors are more common. Simply standing still while solving a visual task (like judging which of two lines is longer) is hard. When walking, it takes much longer to complete a path if it also involves cognitive effort along the way. So you can imagine how difficult walking to school could be.

What about as we approach older age?

Older adults are more prone to multi-tasking errors. When walking, for example, adding another task generally means older adults walk much slower and with less fluid movement than younger adults.

These age differences are even more pronounced when obstacles must be avoided or the path is winding or uneven.

Older adults tend to enlist more of their prefrontal cortex when walking and, especially, when multi-tasking. This creates more interference when the same brain networks are also enlisted to perform a cognitive task.

These age differences in performance of multi-tasking might be more “compensatory” than anything else, allowing older adults more time and safety when negotiating events around them.

Older people can practise and improve

Testing multi-tasking capabilities can tell clinicians about an older patient’s risk of future falls better than an assessment of walking alone, even for healthy people living in the community.

Testing can be as simple as asking someone to walk a path while either mentally subtracting by sevens, carrying a cup and saucer, or balancing a ball on a tray.

Patients can then practise and improve these abilities by, for example, pedalling an exercise bike or walking on a treadmill while composing a poem, making a shopping list, or playing a word game.

The goal is for patients to be able to divide their attention more efficiently across two tasks and to ignore distractions, improving speed and balance.

There are times when we do think better when moving

Let’s not forget that a good walk can help unclutter our mind and promote creative thought. And, some research shows walking can improve our ability to search and respond to visual events in the environment.

But often, it’s better to focus on one thing at a time

We often overlook the emotional and energy costs of multi-tasking when time-pressured. In many areas of life – home, work and school – we think it will save us time and energy. But the reality can be different.

Multi-tasking can sometimes sap our reserves and create stress, raising our cortisol levels, especially when we’re time-pressured. If such performance is sustained over long periods, it can leave you feeling fatigued or just plain empty.

Deep thinking is energy demanding by itself and so caution is sometimes warranted when acting at the same time – such as being immersed in deep thought while crossing a busy road, descending steep stairs, using power tools, or climbing a ladder.

So, pick a good time to ask someone a vexed question – perhaps not while they’re cutting vegetables with a sharp knife. Sometimes, it’s better to focus on one thing at a time.

Peter Wilson, Professor of Developmental Psychology, Australian Catholic University

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

You’ve had a cold or the flu and your symptoms have begun to subside. Your nose has stopped dripping, your cough is clearing and your head and muscles no longer ache.

You’re ready to get off the couch. But is it too early to go for a run? Here’s what to consider when getting back to exercising after illness.

Exercise can boost your immune system – but not always

Exercise reduces the chance of getting respiratory infections by increasing your immune function and the ability to fight off viruses.

However, an acute bout of endurance exercise may temporarily increase your susceptibility to upper respiratory infections, such as colds and the flu, via the short-term suppression of your immune system. This is known as the “open window” theory.

A study from 2010 examined changes in trained cyclists’ immune systems up to eight hours after two-hour high-intensity cycling. It found important immune functions were suppressed, resulting in an increased rate of upper respiratory infections after the intense endurance exercise.

So, we have to be more careful after performing harder exercises than normal.

Can you exercise when you’re sick?

This depends on the severity of your symptoms and the intensity of exercise.

Mild to moderate exercise (reducing the intensity and length of workout) may be OK if your symptoms are a runny nose, nasal congestion, sneezing and minor sore throat, without a fever.

Exercise may help you feel better by opening your nasal passages and temporarily relieving nasal congestion.

However, if you try to exercise at your normal intensity when you are sick, you risk injury or more serious illness. So it’s important to listen to your body.

If your symptoms include chest congestion, a cough, upset stomach, fever, fatigue or widespread muscle aches, avoid exercising. Exercising when you have these symptoms may worsen the symptoms and prolong the recovery time.

If you’ve had the flu or another respiratory illness that caused a high fever, make sure your temperature is back to normal before getting back to exercise. Exercising raises your body temperature, so if you already have a fever, your temperature will become high quicker, which makes you sicker.

If you have COVID or other contagious illnesses, stay at home, rest and isolate yourself from others.

When you’re sick and feel weak, don’t force yourself to exercise. Focus instead on getting plenty of rest. This may actually shorten the time it takes to recover and resume your normal workout routine.

I’ve been sick for a few weeks. What has happened to my strength and fitness?

You may think taking two weeks off from training is disastrous, and worry you’ll lose the gains you’ve made in your previous workouts. But it could be just what the body needs.

It’s true that almost all training benefits are reversible to some degree. This means the physical fitness that you have built up over time can be lost without regular exercise.

To study the effects of de-training on our body functions, researchers have undertaken “bed rest” studies, where healthy volunteers spend up to 70 days in bed. They found that V̇O₂max (the maximum amount of oxygen a person can use during maximal exercise, which is a measure of aerobic fitness) declines 0.3–0.4% a day. And the higher pre-bed-rest V̇O₂max levels, the larger the declines.

In terms of skeletal muscles, upper thigh muscles become smaller by 2% after five days of bed rest, 5% at 14 days, and 12% at 35 days of bed rest.

Muscle strength declines more than muscle mass: knee extensor muscle strength gets weaker by 8% at five days, 12% at 14 days and more than 20% after around 35 days of bed rest.

This is why it feels harder to do the same exercises after resting for even five days.

But in bed rest studies, physical activities are strictly limited, and even standing up from a bed is prohibited during the whole length of a study. When we’re sick in bed, we have some physical activities such as sitting on a bed, standing up and walking to the toilet. These activities could reduce the rate of decreases in our physical functions compared with study participants.

How to ease back into exercise

Start with a lower-intensity workout initially, such as going for a walk instead of a run. Your first workout back should be light so you don’t get out of breath. Go low (intensity) and go slow.

Gradually increase the volume and intensity to the previous level. It may take the same number of days or weeks you rested to get back to where you were. If you were absent from an exercise routine for two weeks, for example, it may require two weeks for your fitness to return to the same level.

If you feel exhausted after exercising, take an extra day off before working out again. A day or two off from exercising shouldn’t affect your performance very much.

Ken Nosaka, Professor of Exercise and Sports Science, Edith Cowan University

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