Purpose: To establish an inexpensive, simple method of predicting peak oxygen uptake (VO2peak) in patients fulfilling the 1994 Centers for Disease Control and Prevention (CDC) criteria for chronic fatigue syndrome (CFS).
Design: A retrospective observational study.
Setting: An outpatient tertiary care chronic fatigue clinic.
Subjects: Two hundred and forty consecutive patients fulfilling the 1994 CDC criteria for CFS.
Interventions: Heart rate, metabolic and ventilatory parameters were measured continuously during a maximal exercise stress test on a bicycle ergometer. Using the equation peak oxygen uptake = 13.1 x peak workload +284 (used by Mullis et al., Br J Sports Med 1999; 33: 352-56), VO2peak was predicted from the peak workload of a maximal exercise capacity test. Pearson correlation coefficient and linear regression analysis were used to establish the most accurate way to predict VO2peak.
Results: Percentage error encountered when comparing actual measured VO2peak with predicted value was 17.3% (+/-10.0). A strong correlation between VO2peak and peak workload was observed (r= 0.89, p < 0.001). A regression analysis established the relation as VO2peak = 10.47 x peak workload +284.1, where VO2peak is given in ml/min and peak workload in W (error in prediction = 11.0+/-9.5%).
Conclusions: Monitoring of the peak workload during a maximal, graded bicycle ergometric test suffices to predict the VO2peak. When predicting VO2peak the used operational definition for the diagnosis of CFS could be taken into account. Compared with the equation used by Mullis et al., peak workload is multiplied by 10.47 in order to predict peak oxygen uptake in CDC-defined CFS patients.