Tag: lower work rates

Exercise responses and psychiatric disorder in chronic fatigue syndrome

Comment in: Exercise responses in the chronic fatigue syndrome. Objective assessment of study is difficult without knowledge of data. [BMJ. 1995]

 

Fatigue, exercise intolerance, and myalgia are cardinal symptoms of the chronic fatigue syndrome, but whether they reflect neuromuscular dysfunction or are a manifestation of depression or other psychiatric or psychological disorders diagnosed in a high proportion of fatigued patients in the community is unclear.’ In previous studies patients with the chronic fatigue syndrome showed exercise intolerance in incremental exercise tests, which seemed to be related to an increased perception of effort; also, blood lactate concentrations in some patients tended to increase more rapidly than normal at low work rates, implying inefficient aerobic muscle metabolism.2 We examined venous blood lactate responses to exercise at a work rate below the anaerobic threshold in relation to psychiatric disorder.

You can read the rest of this article here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2550606/pdf/bmj00607-0028.pdf

 

Source: Lane RJ, Burgess AP, Flint J, Riccio M, Archard LC. Exercise responses and psychiatric disorder in chronic fatigue syndrome. BMJ. 1995 Aug 26;311(7004):544-5. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2550606/pdf/bmj00607-0028.pdf

 

Lactate responses to exercise in chronic fatigue syndrome

Comment on: Exercise performance and fatiguability in patients with chronic fatigue syndrome. [J Neurol Neurosurg Psychiatry. 1993]

 

We were interested to read the recent account of exercise characteristics in patients with chronic fatigue syndrome by Gibson et al,’ which concluded that there was no abnormality of neuromuscular function in this condition. Patients reached the limits of exercise tolerance at lower heart rates than controls during incremental exercise to exhaustion but their peak work rates and duration of exercise did not differ significantly from the control group, although the total work done (the product of these variables) would appear to have been less; the authors had previously reported that patients with this condition showed a reduction in maximal work rate achieved in such tests.2 Despite this, plasma lactate levels at the end of exercise were as high in the patients as the controls.

In an earlier study using incremental exercise on a treadmill, Riley et a13 had found higher heart rates and increased lactate levels compared with normal controls at submaximal work rates but similarly noted no differences at peak exercise.

We have found that a proportion of patients with chronic fatigue syndrome exhibit abnormally raised lactate levels following steady state exercise at work rates below the anerobic threshold, corresponding to roughly half the peak work rates achieved in the incremental test paradigm.4 It is thus possible that lactate levels in some patients increase more rapidly than normal at lower work rates.

The cause of this apparent ‘left shift’ of the anaerobic threshold is unclear. Neither we nor Gibson et al 2 found evidence of “deconditioning” in terms of cardiac responses to exercise in our patients, and phosphorus spectroscopy of muscle in the syndrome has shown no consistent disturbance of muscle energy metabolism.5 The phenomenon may be of significance in the pathogenesis of “fatigue” in some patients, and it may be premature to conclude that neuromuscular function in all patients is normal, or that the “fatigue” is exclusively “central” in origin. Indeed, it may be presumptuous to consider chronic fatigue syndrome as a unitary entity.

You can read the rest of this comment here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1072952/pdf/jnnpsyc00035-0134b.pdf

 

Source: Lane RJ, Woodrow D, Archard LC. Lactate responses to exercise in chronic fatigue syndrome. J Neurol Neurosurg Psychiatry. 1994 May;57(5):662-3. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1072952/