Maximal oxygen uptake and lactate metabolism are normal in chronic fatigue syndrome

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Previous studies in chronic fatigue syndrome (CFS) have reported reductions in maximal oxygen uptake (V̇O2max), yet often the testing procedures have not followed accepted guidelines, and gender data have been pooled. The present study was undertaken to reevaluate exercise capacity in CFS patients by using “gold standard” maximal exercise testing methodology and stratifying results on a gender basis.


Sixteen male and 17 female CFS patients and their gender-, age-, and mass-matched sedentary controls performed incremental exercise to volitional exhaustion on a stationary cycle ergometer while selected cardiorespiratory and metabolic variables were measured.


V̇O2max in male CFS patients was not different from control values (CFS: 40.5 ± 6.7; controls: 43.3 ± 8.6; mL·kg−1·min−1) and was 96.3 ± 17.9% of the age-predicted value, indicating no functional aerobic impairment (3.7 ± 17.9%). In female CFS patients, V̇O2max was lower than control values (CFS: 30.0 ± 4.7; controls: 34.2 ± 5.6; mL·kg−1·min−1, P = 0.002), but controls were higher than the age-predicted value (112.6 ± 15.4%, P = 0.008) whereas the CFS patients were 101.2 ± 20.4%, indicating no functional aerobic impairment (−1.2 ± 20.4%). Maximal heart rate (HRmax) in male CFS patients was lower than their matched controls (CFS: 184 ± 10; controls: 192 ± 12; beats·min−1;P = 0.016) but was 99.1 ± 5.5% of their age-predicted value. In female CFS patients, HRmax was not different from controls (CFS: 183 ± 11; controls: 186 ± 10; beats·min−1) and was 98.9 ± 5.1% of the age-predicted value. The V̇O2 at the lactate threshold (LT) in each gender group, whether expressed in mL·kg−1·min−1 or as a percentage of V̇O2max, was not different between CFS patients and controls.


In contrast to most previous reports, the present study found that V̇O2max, HRmax, and the LT in CFS patients of both genders were not different from the values expected in healthy sedentary individuals of a similar age.

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