Our collaborators at the Workwell Foundation, working with physical therapists and exercise physiologists, have published a case report in the Cardiopulmonary Physical Therapy Journal on measurement reproducibility over the two days of a two-day cardiopulmonary exercise test (CPET). The report looked at the variability of CPET results from six people with and without medical diagnoses of fatiguing illnesses. All of the participants were women and matched by age and BMI. Although the authors point out that generalizations are not possible due to the low number of included subjects, the response to exercise by both individuals with ME/CFS is important to highlight. 

Notable findings:

• Measurements at ventilatory anaerobic threshold (VAT), the level at which a person can generally work for an extended amount of time, were considerably decreased on CPET day two. Therefore, time spent above VAT will cause fatigue and require rest—demonstrating the importance of activity pacing strategies to manage physical demands.
• Early onset of VAT in both individuals with ME/CFS may indicate a diminished metabolic capacity to perform usual tasks.
• CPET day two measurements at VAT for the low-functioning participant with ME/CFS suggests activities more intense than slow walking or standing while washing dishes could trigger activation of an impaired oxidative metabolic pathway that could prompt postexertional symptoms.
• Day-to-day variability in VAT could lead to difficulty in estimating the metabolic costs of activities. However, variations in functional capacity could be used to form the basis for scheduling activities as part of a pacing self-management program.
• A two-day CPET could be a useful diagnostic tool in identifying postexertional malaise.