Prediction of peak oxygen uptake in Chronic Fatigue Syndrome (CFS)
October 6, 1999
OBJECTIVES: To establish a simple, valid, and acceptable
method of predicting peak oxygen uptake (VO2peak) in patients
with chronic fatigue syndrome (CFS), which could provide a
basis for subsequent exercise prescription at an appropriate
intensity as part of a clinical rehabilitation programme.
METHODS: A total of 130 patients who met UK research criteria
for CFS were taken from consecutive referrals for chronic
fatigue to the University Department of Medicine at Withington
Hospital, Manchester. VO2peak was determined using an
incremental graded exercise test to exhaustion. Respiratory
gas exchange, work rate, and heart rate were monitored
RESULTS: In all patients, VO2peak was found to
correlate strongly and significantly with peak work rate
(WRpeak) during testing (r2 = 0.88, p<0.001). In patients who
exercised for longer than two minutes (n = 119), regression
analysis established the relation as Vo2peak = 13.1 x WRPpeak
+ 284, where VO2 is given in ml/min and WR in W. The mean
error between the measured VO2peak and the predicted value was
10.7%. The relation between increase in work rate and oxygen
uptake across the group was highly significant (r2 = 0.87,
p<0.001), and given as VO2increase = 12.0 x WRincrease, this
value being similar to that expected for healthy individuals.
Almost all (97%) subjects reported no exacerbation of symptoms
after maximal exercise testing.
CONCLUSIONS: Using a simple to
administer maximal exercise test on a cycle ergometer, it is
possible to predict accurately the VO2peak of a patient with
CFS from peak work rate alone. This value can then be used as
an aid to setting appropriate exercise intensity for a
rehabilitation programme. The increase in VO2 per unit
increase in workload was consistent with that expected in
healthy individuals, suggesting that the physiological
response of the patients measured here was not abnormal.
Contrary to the belief of many patients, maximal exercise
testing to the point of subjective exhaustion proved to be
harmless, with no subjects suffering any lasting deterioration
in their condition after assessment.
Mullis R, Campbell IT, Wearden AJ, Morriss RK, Pearson DJ
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