An international survey of experiences and attitudes towards pacing using a heart rate monitor for people with myalgic encephalomyelitis/chronic fatigue syndrome

1 Introduction

Myalgic encephalomyelitis (ME) is a “complex, acquired multi-systemic disease with a profound dysfunction/dysregulation of the neurological control system resulting in faulty communication and interaction between the central nervous system and major body systems” [1]. The defining feature of ME is post-exertional malaise (PEM), the worsening of symptoms following physical, cognitive, emotional and social activity with a prolonged recovery period. There are over 30 symptoms of PEM [2] including cognitive impairment, muscle pain, fatigue, flu-like symptoms, difficulty sleeping etc. There is a delay between a triggering activity and the onset of PEM usually 2-7 days after but this may vary [2]. Symptoms usually last days to weeks, but again can vary [2]. The variability in onset delay and duration of PEM makes planning daily activities difficult, raising the importance of interventions to improve the predictability of symptoms as a strategy to enhance health-related quality of life in people with ME (PwME).

It is unclear what causes PEM. One area of research using cardiopulmonary exercise testing (CPET) has shown that PwME have a reduced ventilatory anaerobic threshold (VAT) especially when the test is repeated on a second consecutive day [3]. The VAT or lactate threshold is the point at which a person switches from aerobic to anaerobic metabolism, and there is an increased production of lactate as a by-product [4]. PwME have been shown to reach this threshold more quickly than healthy people, and it is theorised that this could be due to inefficient and damaged aerobic metabolic processes causing the symptoms of PEM. The early production of lactate [5] during activity or inefficient production of adenosine triphosphate (ATP) [6] could explain the symptoms of PEM such as muscle and joint pain, cognitive dysfunction and fatigue in PwME. In addition, decreased oxygen extraction in a subset of PwME [7] suggests ME involves a problem of oxygen utilization rather than bioavailability. This phenomenon may be responsible for observed maladaptation in autonomic function, including orthostatic [8] and chronotropic intolerances [9].

It follows from findings of physiological studies that pacing activity intensities and durations may help PwME to stabilize symptoms and functioning. General frameworks for pacing are available, such as energy envelope theory [10, 11] and ‘spoon theory’ [12]. However, these general frameworks lack the specificity necessary for PwME to make moment-to-moment and day-to-day decisions about energy expenditure and corresponding future potential to do daily activities. Physiological findings suggest that maintaining activity intensities and durations below the VAT may provide the potential for useful real-time feedback. Heart rate is a common cardiovascular parameter measured by commercially available biometric devices, so they may be useful tools to help PwME maintain activities at intensities below VAT.

An energy management strategy incorporating heart rate monitoring (HRM), first developed by the Workwell Foundation in 2010, has been incorporated into a number of consensus and guidance documents [13–17], and is considered a reliably effective intervention among PwME. This energy management strategy suggests identifying the average resting heart rate over seven days and then setting a limit of 15 beats above that resting heart rate (HR) using HRM to reduce activity above that limit. However, there is only one piece of scholarship about the effectiveness of this intervention. Stevens et al. [18] conducted a case study using HRM and a pragmatic flexibility and strengthening programme. After one year the participant was able to complete daily activities without symptoms with improvements in maximum oxygen consumption (VO₂) and maximum minute ventilation (VE) on a cardiopulmonary exercise test (CPET).

Despite the popularity of pacing strategies among PwME, preliminary evidence of effectiveness and integration of pacing recommendations into clinical consensus and guidance documents, little is known about the specific current practices of PwME. Elucidation of current practices would allow for the identification of potential patient-derived best practices that would be the subject of future study, in addition to establishing potential learning needs among PwME who do and do not use heart rate monitoring. The present study, therefore, aimed to identify the experiences and attitudes of PwME towards HRM.

2 Methods

Ethical approval was obtained from the University of Leicester (#31983). This survey was conducted in accord with the ethical standards of the Committee on Human Experimentation of the University of Liverpool and in accord with the Declaration of Helsinki of 1964 and its later amendments. An online survey was developed by members of ME/CFS Pacing with a Heart Rate Monitor #2 Facebook group and Physios for ME. 40 questions were devised (Table 1) with tick boxes to reduce the energy requirement needed to answer, and open questions to allow expansion if required. The survey was advertised on the Physios for ME website (www.physiosforme.com) with a participant information sheet that was read before the participants clicked on a link for the survey. The link to the Physios for ME website was provided on various sites on Facebook and Twitter. The inclusion criteria were PwME (self-reported) who had used or were using HRM. The survey was open for three weeks and all data collected was anonymous. Consent was assumed if the participant clicked on the link after reading the information sheet.

Descriptive and inferential statistics were used for the quantitative data. The data were coded and entered into IBM SPSS (version 25.0). Participants were separated into mild, moderate, severe and very severe ME (self-reported) before and after using HRM, the data were then analysed to see if there were any differences between the groups after HRM. Differences were calculated between these groups in the severity of their PEM and recovery time and the type of HRM device using Wilcoxon Signed-Ranks test. Finally, the qualitative responses were analysed with content analysis [19], however, a more detailed analysis of the qualitative results will be presented in a separate article with results from follow-up interviews.

4 Discussion

This study aimed to identify the experiences and attitudes of PwME towards HRM. As the survey participants were mainly female between the ages of 30 – 50 this reflects the larger ME population [1]. Approximately 40% of the survey participants described themselves as having severe or very severe ME indicating that the survey results provide experiences of more people with this higher level of severity of ME. As it is thought that approximately 25% of the ME population have severe or very severe ME [21] this survey therefore over represents the experiences of severe and very severe PwME. Over 50% of the participants were from the UK so it is not clear if more people in the UK are using HRM or that the survey did not reach many of the ME populations in the USA, Canada and Australia. In future surveys, the survey link would need to be shared with more ME organisations in these countries. The results of this survey therefore reflect the experiences of people mainly in the UK and Europe.

Although the use of HRM has been encouraged since 2010 [18] for people with ME, the majority of the survey participants had only been using it for the last three years despite most of the participants having ME for over five years. There appears to be a lack of knowledge related to the use of HRM and certainly a lack of research exploring the efficacy of its use in people with ME. The variety of methods used to calculate the estimated VAT demonstrates the lack of knowledge and understanding of how to calculate it. The use of the CPET test to calculate an individual’s VAT is seen as the gold standard, however, Moore et al. [22] identified that up to 7% of people with ME who undertook CPET took up to 10 weeks to recover and 1% did not recover after one year. Outside of the USA there is also a lack of CPET testing. So an alternative, valid and reliable way of calculating the VAT needs to be found as many countries will not have access to CPET testing.

The concerning aspect of the use of the HRM was that some participants were using too high a level of estimated VAT or were attempting to use zones when working with the heart rate monitor. There is a clear need for PwME and healthcare professionals advising them to know how to use these devices specifically for ME. Healthcare professionals are perhaps familiar with the use of heart rate monitors for cardiac rehabilitation where people with cardiac conditions are encouraged to work at 60% of their maximum heart rate [23] and maintain that level of aerobic activity for 20 minutes in order to improve cardiovascular fitness. Unfortunately for PwME, their anaerobic threshold is lower [24] so if they were to work at 60% of their maximum heart rate this is likely to exceed their VAT and cause significant PEM. The survey showed not just the lack of knowledge but also the lack of support that PwME have received from healthcare professionals, and this reflects two meta-syntheses that highlighted that PwME are not taken seriously by physicians and that “there is general scepticism and minimization of ME” [25, 26]. HRM has the potential to show carers, family members and healthcare professionals that the person with ME has a physiological problem that requires recognition and validation.

The survey identified that over 100 devices were used for HRM with the most popular being the Apple watch, followed by Garmin, Fitbit and Polar devices. The results show that all the devices have the potential to improve the level of severity of ME, the severity of PEM and rate of recovery from PEM, independent of whether a chest strap is used. However, a number of people highlighted that all the devices on the market are designed for people without a chronic condition. There is a need for a more bespoke device that is easy to use with functions designed for PwME, for example rather than setting zones and targets to exceed [27] there would be the option to set an alert to stay below a target. It was also clear that heart rate devices do not have the capacity to monitor the energy used during cognitive, social and emotional activities. A device that could do that would be very beneficial for PwME.

The survey also highlighted that some PwME were using heart rate variability to enhance HRM although this was not without its challenges. HRV is the fluctuation in the time intervals between consecutive heartbeats [20] and can be used to estimate autonomic nervous system health. It can potentially suggest whether there is imbalance in the sympathetic and parasympathetic drives that may produce symptoms of dysautonomia and PEM. This may be an area for future research.

A number of negatives were identified with HRM, the main ones being lack of support, financial cost and too restrictive. Lack of support has already been discussed, however as well as educating healthcare professionals perhaps financial support to provide these devices would be beneficial for PwME to manage their condition, considering people with diabetes are provided with blood sugar monitors by the NHS in the UK [28] and insurance companies in the USA and Canada. In relation to the negative responses about HRM causing restrictions to activity and potentially leading to deconditioning, this highlights the need for individualised care and the importance of support for PwME while trying these devices. Assistance would be beneficial in relation to: setting up the device, learning to pace with the device, and social support so that they can rest and reduce their activity while still managing their everyday commitments. Ultimately by finding their baseline and allowing their body to rest there maybe the potential to improve their activity levels [29].

Nearly all the participants found benefits with HRM but less than a third found that these benefits translated into increased functional activity. In fact, HRM often resulted in reduced functional activity to stay under their VAT. However, it is encouraging to see the potential for HRM to increase capacity to work or to increase the time at work. As many as 1 : 250 of the working population have ME [29] and as ME affects mainly working age adults [1, 30] any approach that has the potential to help people continue in work is beneficial. It is important to recognise that HRM is a management tool that needs to be used in conjunction with many other management strategies such as rest, prioritising, and planning [31, 32]. HRM is not a cure for ME, but it can be used as a management tool with the potential to help most PwME.

5 Conclusion

This survey aimed to identify the experiences and attitudes of PwME towards HRM. Although there are limitations due to the range of the sample, it has highlighted that HRM has many benefits including helping PwME to understand and manage their PEM and support them to increase their activities, including work. It is recognised that one of the negatives is the potential to reduce physical function although this may only be in the initial stages of HRM. It has also highlighted the need for more research and education of healthcare professionals in the safe use of HRM.

Ethical approval

Ethical approval was obtained from the University of Leicester (31983).

Informed consent

Consent was assumed if the participant clicked on the survey link after reading the information sheet.