Long Covid and Post-Exertional Malaise: what is it and how to manage it?

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Mounting evidence suggests that large numbers of people recovering from Covid-19 go on to suffer from Long Covid. The most commonly reported symptoms of Long Covid are fatigue, cognitive impairment, and post-exertional malaise (PEM).

What is PEM?

Post-exertional malaise (PEM) is described as the worsening of symptoms following minor physical or mental exertion. These symptoms typically develop 12 to 48 hours after activity and can last for days, or in some cases, weeks.

In aerobic or “with oxygen” exercise, your muscles have enough oxygen to produce the energy needed to perform the activity. When you don’t have enough oxygen, your body naturally switches over to anaerobic exercise, where it draws on your energy levels to continue. When your energy levels are insufficient, this leads to an out-of-proportion intensification of symptoms known as PEM. This means even simple daily tasks like climbing the stairs can leave you feeling like you’ve run a marathon!

Recognising PEM symptoms

When approaching the point at which PEM is triggered, you may notice a range of symptoms:

  • Immediate – difficulty breathing, dizziness, nausea

  • Short term – joint/muscle pain, headache, brain fog, disturbed sleep

  • Long term – general decrease in function, weakness, cardiopulmonary and flu-like symptoms

People with PEM and Long Covid can also enter into a cycle of ‘push and crash’. When their symptoms are low, there’s a push to get as much done as possible. But the overexertion in completing these tasks leads to an increase in symptoms, resulting in a forced rest - or crash.

A helpful analogy to explain PEM is to think of yourself as a mobile phone battery. Every day, you put your phone on charge and as soon as you unplug it, all the apps, calls and texts will start to drain the battery. Your body is the same: everything you do – not just your physical activity but cognitive and emotional activity too – will drain your energy reserves. The call you make to a family member, the book you read or the housework you do will all use up energy, meaning that it will take much longer for you to recharge. As a result, you might feel more drained and tired over the next few days.

How to manage PEM?

Patients recovering from Covid and experiencing PEM hit their anaerobic threshold much sooner than they previously would have. This means that even the mildest activity causes fatigue.

So, the focus needs to be on managing your heart rate throughout the day to keep it below the anaerobic threshold.

The key is to ensure that whenever you undertake an activity, your heart rate remains below the level at which your body will draw on energy reserves it doesn’t have (which triggers PEM). This includes cognitive and emotional activities too. For example, some people find noisy environments or stress can significantly raise their heart rates.

Heart rate monitors can help

Heart rate monitors are personal monitoring devices that allow you to measure or display your heart rate in real time. They can be worn on your wrist or across your chest. The advantage of wearing them as you recover from Long Covid is that most of them have the ability to set a heart rate zone. Because they continuously track and record your heart rate, you can ensure that you remain within the right heart rate zone to prevent post-exertional malaise. This can help take away the anxiety of checking your heart rate manually, and is much less time consuming.

There are also a number of fatigue management strategies you can use to help manage your recovery. 

  • Activity planning: including pacing, prioritisation, planning.

  • Analysing your activity: using symptom diaries to establish your baseline activity level.

  • Rest and Relaxation: incorporating time to pause into your daily routine.

Everyone’s limits are different, so identifying your own personal limitations is vital. Doing so will support your Long Covid recovery and mean you can slowly achieve an increase in your activity levels without the worry of PEM.

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