Tag: subanaerobic threshold

Heterogeneity in chronic fatigue syndrome: evidence from magnetic resonance spectroscopy of muscle

Abstract:

It has been shown previously that some patients with chronic fatigue syndrome show an abnormal increase in plasma lactate following a short period of moderate exercise, in the sub-anaerobic threshold exercise test (SATET).

This cannot be explained satisfactorily by the effects of ‘inactivity’ or ‘deconditioning’, and patients with abnormal lactate responses to exercise (SATET +ve) have been found to have significantly fewer Type 1 muscle fibres in quadriceps biopsies than SATET -ve patients. We performed phosphorus magnetic resonance spectroscopy on forearm muscles of 10 SATET +ve patients, 9 SATET -ve patients and 13 sedentary volunteers.

There were no differences in resting spectra between these groups but at the end of exercise, intracellular pH in the SATET +ve patients was significantly lower than in both the SATET -ve cases and controls (P < 0.03), and the SATET +ve patients also showed a significantly lower ATP synthesis rate during recovery (P < 0.01), indicating impaired mitochondrial oxidative phosphorylation.

These observations support other evidence which indicates that chronic fatigue syndrome is a heterogeneous disorder, and confirms the view that some chronic fatigue syndrome patients have a peripheral component to their fatigue.

 

Source: Lane RJ, Barrett MC, Taylor DJ, Kemp GJ, Lodi R. Heterogeneity in chronic fatigue syndrome: evidence from magnetic resonance spectroscopy of muscle. Neuromuscul Disord. 1998 May;8(3-4):204-9. http://www.ncbi.nlm.nih.gov/pubmed/9631403

 

Muscle fibre characteristics and lactate responses to exercise in chronic fatigue syndrome

Abstract:

OBJECTIVES: To examine the proportions of type 1 and type 2 muscle fibres and the degree of muscle fibre atrophy and hypertrophy in patients with chronic fatigue syndrome in relation to lactate responses to exercise, and to determine to what extent any abnormalities found might be due to inactivity.

METHODS: Quadriceps needle muscle biopsies were obtained from 105 patients with chronic fatigue syndrome and the proportions of type 1 and 2 fibres and fibre atrophy and hypertrophy factors were determined from histochemical preparations, using a semiautomated image analysis system. Forty one randomly selected biopsies were also examined by electron microscopy. Lactate responses to exercise were measured in the subanaerobic threshold exercise test (SATET).

RESULTS: Inactivity would be expected to result in a shift to type 2 fibre predominance and fibre atrophy, but type 1 predominance (23%) was more common than type 2 predominance (3%), and fibre atrophy was found in only 10.4% of cases. Patients with increased lactate responses to exercise did have significantly fewer type 1 muscle fibres (p<0.043 males, p<0.0003 females), but there was no evidence that this group was less active than the patients with normal lactate responses. No significant ultrastructural abnormalities were found.

CONCLUSION: Muscle histometry in patients with chronic fatigue syndrome generally did not show the changes expected as a result of inactivity. However, patients with abnormal lactate responses to exercise had a significantly lower proportion of mitochondria rich type 1 muscle fibres.

 

Source: Lane RJ, Barrett MC, Woodrow D, Moss J, Fletcher R, Archard LC. Muscle fibre characteristics and lactate responses to exercise in chronic fatigue syndrome. J Neurol Neurosurg Psychiatry. 1998 Mar;64(3):362-7. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2169994/ (Full article)

 

Exercise responses in the chronic fatigue syndrome. Objective assessment of study is difficult without knowledge of data

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