TITLE:
Heart Rate Thresholds to Limit Activity in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients (Pacing): Comparison of Heart Rate Formulae and Measurements of the Heart Rate at the Lactic Acidosis Threshold during Cardiopulmonary Exercise Testing
AUTHORS:
C. (Linda) M. C. van Campen, Peter C. Rowe, Frans C. Visser
KEYWORDS:
Chronic Fatigue Syndrome, Myalgic Encephalomyelitis, Cardiopulmonary Ex-ercise Testing, Peak Oxygen Consumption, Lactic Acidosis Threshold, Oxygen Consumption at the Anaerobic Threshold, Workload, Pacing, Heart Rate For-mulae
JOURNAL NAME:
Advances in Physical Education,
Vol.10 No.2,
May
20,
2020
ABSTRACT: Introduction: Based on the hypothesis that oxidative metabolism is impaired in ME/CFS,
a previous study recommended a pacing self-management strategy to prevent
post-exertional malaise. This strategy involved a prescription to maintain a
heart rate below the anaerobic threshold during physical activities. In the
absence of lactate sampling or a cardiopulmonary exercise test (CPET), the
pacing self-management formula defines 55% of the age-specific predicted
maximal heart rate as the heart rate at the anaerobic threshold. Thus far there
has been no empiric evidence to test this self-pacing method of predicting
heart rate at anaerobic threshold. The aim of this study was to compare
published formula-derived heart rates at the anaerobic threshold with the
actual heart rate at the lactic acidosis threshold as determined by CPET. Methods
and Results: Adults with ME/CFS who had undergone a symptom-limited CPET
were eligible for this study (30 males, 60 females). We analysed males and
females separately because of sex-based differences in peak oxygen consumption.
From a review paper, formulae to calculate maximal predicted heart rate were
used for healthy subjects. We compared the actual heart rate at the lactic acid
threshold during CPET to the predicted heart rates determined by formulae.
Using Bland-Altman plots, calculated bias: the mean difference between the
actual CPET heart rate at the anaerobic threshold and the formula predicted
heart rate across several formulae varied between -28 and
19 bpm in male ME/CFS patients. Even in formulae with a clinically acceptable
bias, the limits of agreement (mean bias ± 2SD) were unacceptably high for all formulae. For female ME/CFS
patients, bias varied between 6 and 23 bpm, but the limits of agreement were
also unacceptably high for all formulae. Conclusion: Formulae generated
in an attempt to help those with ME/CFS exercise below the anaerobic threshold
do not reliably predict actual heart rates at the lactic acidosis threshold as
measured by a cardiopulmonary exercise test. Formulae based on age-dependent
predicted peak heart rate multiplied by 55% have a wide age-specific
variability and therefore have a limited application in clinical practice.