CPET – Cardiopulmonary Exercise Test

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Pacing with a heart rate monitor to minimize post-exertional malaise (PEM) in ME/CFS and long COVID

By Caroline Christian

Suppose you have been diagnosed with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). In that case, you may already know that the cardinal symptom is post-exertional malaise (PEM), also called post-exertional symptom exacerbation (PESE). Approximately 50% of people with long COVID also experience PEM/PESE and meet the diagnostic criteria for ME/CFS. 

Post-exertional malaise, or PEM, is a worsening of symptoms after physical, mental, or emotional stress that would not have caused a problem before the illness. During PEM, any number of ME/CFS symptoms may worsen. PEM “crashes” can last days, weeks, or even longer. For some, worsening symptoms may become persistent and mark an overall decline in function that is not recoverable.

At the core of PEM is abnormal energy production and delayed recovery after activity. Even light everyday tasks can exacerbate fatigue, cause dizziness, and prolong recovery. 

There are currently no FDA-approved treatments for ME/CFS or long COVID. Although treating symptoms can help with these conditions, pacing/energy conservation techniques can be effective tools for managing day-to-day life. 

This blog discusses an approach to minimize PEM by pacing activities with a heart rate monitor (HRM). When appropriately executed, pacing with an HRM will interrupt the boom-bust energy cycle and minimize PEM. 

ME/CFS and pacing with a heart rate monitor (HRM) 

Heart rate monitoring (HRM) provides direct and instant biofeedback that increases symptom awareness. If a person with ME/CFS can learn to link heart rate with symptoms during and after exertion, the results can significantly improve quality of life.  

Let’s look at three simple steps to get you started.

Step 1: Identify your ventilatory or anaerobic threshold (V/AT)

In ME/CFS and long COVID, energy made with oxygen (i.e., aerobic) is insufficient to meet the required demand. Instead, people with these conditions must rely more on a less efficient form of energy made without oxygen (anaerobic).

People with ME/CFS are more likely to switch from aerobic to anaerobic metabolism at lower activity levels than their healthier counterparts. This change occurs because aerobic metabolism cannot provide enough energy in people with ME/CFS. 

In a finding unique to ME/CFS (and many with long COVID), even mild physical activity can further decrease the threshold at which energy production switches from aerobic to anaerobic, creating a vicious push-crash cycle. This threshold is called the ventilatory/anaerobic threshold, or V/AT for short. We are interested in the heart rate corresponding to the V/AT for pacing. 

There are two ways to determine the V/AT: 

  1. 2-day CPET: 

The most accurate way to determine an individual’s V/AT is with a 2-day cardiopulmonary exercise test (CPET), a test Workwell pioneered for ME/CFS. For more about 2-day CPET, click here. A second day of testing is needed to capture the abnormal physiological changes that occur in response to exertion. If you have had a 2-day CPET, Workwell recommends using the V/AT heart rate measured on day two of testing.

What if you do not have a 2-day CPET? That’s no problem! Workwell offers a simple rule of thumb that only requires knowing your resting heart rate. 

  1. Resting heart rate (RHR) method

Record your resting heart rate after waking but before getting out of bed. After a week, calculate a 7-day average RHR. This value can be used as a baseline to determine the V/AT. The average RHR is also used to evaluate recovery from daily activities – either an increase or decrease in RHR may indicate overexertion and signal the need for additional rest and recovery. 

To estimate the V/AT, add 15 beats per minute (bpm) to the 7-day average RHR. For example, if RHR is 60 bpm, your estimated heart rate at the V/AT is 75 bpm. 

Workwell recommends RHR + 15 beats as a starting point for estimating the V/AT.  This conservative estimate takes into account the fact that over 85% of people with ME/CFS have a blunted heart rate response to exercise, a condition called chronotropic incompetence (CI). With CI, the heart rate does not increase appropriately during exercise to meet the increased demand for oxygen. CI can lower AT, indicating that applying formulas to estimate AT will lead to exceeding the energy envelope in ME/CFS. For this reason, Workwell advocates against using the standard age-based formula based on maximum heart rate. 

Not everyone with ME/CFS has CI, but there is no way to determine this without a CPET. 

Step 2: Tie activities to perceived exertion

The goal with pacing is simple: try to stay below the heart rate at the V/AT. Avoid spending time above the V/AT for more than two minutes if possible. Setting alarms on an HRM (most have this functionality) can help people avoid exceeding their energy envelope. When the alarm goes off, it’s time to stop activities and rest until the heart rate returns to within ten beats of RHR. 

Remember that cognitive activities and tasks use aerobic energy production and may need modification to avoid crashes.

Activities above the V/AT should feel “hard,” whereas activities below this threshold should feel “light and easy.” If an activity feels hard, stop and rest. If an activity feels light and easy with no symptoms of PEM, it can be continued safely. 

Workwell created a simple infographic on the PEM time course to help identify PEM, including the immediate and short-term symptoms and the more familiar longer-term impacts. Understanding the time course of PEM, paired with HRM, can help people with ME/CFS and long COVID avoid the push-crash cycle.

The next step is to tie symptoms to heart rate. The first symptoms of PEM often include increased breathing or breathlessness, brain fog, dizziness, nausea, and fatigue. Notice the heart rate at which these symptoms occur. 

If you are experiencing these symptoms in response to exertion, you have likely exceeded your V/AT and need to set an HRM alarm corresponding to a lower heart rate. 

  1. Keep an activity and symptom log

The next step in pacing with an HRM is to put it to the test. Implementing a pacing/energy conservation program should reduce symptoms of PEM. If not, pay attention to time spent above the V/AT and activity levels, including cognitive tasks. If you are still experiencing a push-crash cycle with PEM, the V/AT you are using may be too high, or your crashes are related to cognitive exertion or orthostatic stress (e.g., stress from being upright, even if the heart rate is under V/AT). 

Over time, people may realize they can tolerate a higher V/AT. Still, Workwell recommends starting with RHR + 15 beats and waiting to explore a bigger energy envelope, especially if immediate symptoms of PEM occur at a higher heart rate threshold. 

While pacing with an HRM is not a treatment for ME/CFS, activity management is a helpful tool for avoiding symptom exacerbation and minimizing PEM. 

Need help finding a heart rate monitor? There are many sports watches on the market that range in price. Some trusted brands include Garman, Fitbit, Apple, and Polar; however, the optic sensors on sports watches are less accurate than a chest strap for heart rate tracking. For this reason, Workwell recommends using a chest strap, such as a Polar H10. Both chest straps and sports watches can pair with apps with alarms when approaching V/AT. Another benefit of chest straps is they also allow for monitoring heart rate variability (HRV).

For more help with pacing with a heart rate monitor, Workwell Health coaches are available.