Comment on: Exercise responses and psychiatric disorder in chronic fatigue syndrome. [BMJ. 1995]
EDITOR,-In their study of exercise responses and psychiatric disorder in the chronic fatigue syndrome Russell J M Lane and colleagues claim to have detected abnormal lactate responses to subanaerobic threshold exercise in 31 of 96 patients. As no data are offered to support this statement, however, objective assessment of the validity of their findings is difficult.
The authors’ definition of an abnormal response is “lactate concentrations exceeding the upper 99% reference limit for normal control subjects at two or more time points.” However, only three samples were taken (before, immediately after, and 30 minutes after exercise), and a raised lactate concentration in the sample obtained before exercise began cannot be described as an abnormal response to exercise. Neither the method used to measure lactate nor its precision is given; assessment of the importance of the “abnormal” lactate concentrations could not be guessed at without this information, even if the authors had given details of the patients’ concentrations.
You can read the full comment along with the authors’ reply here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2551191/pdf/bmj00618-0070a.pdf
Source: Hutchison AS. Exercise responses in the chronic fatigue syndrome. Objective assessment of study is difficult without knowledge of data. BMJ. 1995 Nov 11;311(7015):1304. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2551191/pdf/bmj00618-0070a.pdf