Tag: muscle fatigue

Deconstructing post-exertional malaise: An exploratory factor analysis

Abstract:

Post-exertional malaise is a cardinal symptom of myalgic encephalomyelitis and chronic fatigue syndrome. There are two differing focuses when defining post-exertional malaise: a generalized, full-body fatigue and a muscle-specific fatigue. This study aimed to discern whether post-exertional malaise is a unified construct or whether it is composed of two smaller constructs, muscle fatigue and generalized fatigue. An exploratory factor analysis was conducted on several symptoms that assess post-exertional malaise. The results suggest that post-exertional malaise is composed of two empirically different experiences, one for generalized fatigue and one for muscle-specific fatigue.

© The Author(s) 2016.

 

Source: McManimen SL, Sunnquist ML, Jason LA. Deconstructing post-exertional malaise: An exploratory factor analysis. J Health Psychol. 2016 Aug 24. pii: 1359105316664139. [Epub ahead of print] https://www.ncbi.nlm.nih.gov/pubmed/27557649

 

Genetic evaluation of AMPD1, CPT2, and PGYM metabolic enzymes in patients with chronic fatigue syndrome

Abstract:

Chronic fatigue syndrome (CFS) is a disease that can seriously impair one’s quality of life; patients complain of excessive fatigue and myalgia following physical exertion. This disease may be associated with abnormalities in genes affecting exercise tolerance and physical performance. Adenosine monophosphate deaminase (AMPD1), carnitine palmitoyltransferase II (CPT2), and the muscle isoform of glycogen phosphorylase (PYGM) genes provide instructions for producing enzymes that play major roles in energy production during work.

The aim of this study was to look for evidence of genotype-associated excessive muscle fatigue. Three metabolic genes (AMPD1, CPT2, and PYGM) were therefore fully sequenced in 17 Italian patients with CFS. We examined polymorphisms known to alter the function of these metabolic genes, and compared their genotypic distributions in CFS patients and 50 healthy controls using chi-square tests and odds ratios. One-way analysis of variance with F-ratio was carried out to determine the associations between genotypes and disease severity using CF scores.

No major genetic variations between patients and controls were found in the three genes studied, and we did not find any association between these genes and CFS. In conclusion, variations in AMPD1, CPT2, and PGYM genes are not associated with the onset, susceptibility, or severity of CFS.

 

Source: Maltese PE, Venturini L, Poplavskaya E, Bertelli M, Cecchin S, Granato M, Nikulina SY, Salmina A, Aksyutina N, Capelli E, Ricevuti G, Lorusso L. Genetic evaluation of AMPD1, CPT2, and PGYM metabolic enzymes in patients with chronic fatigue syndrome. Genet Mol Res. 2016 Jul 29;15(3). doi: 10.4238/gmr.15038717. https://www.ncbi.nlm.nih.gov/pubmed/27525900

 

Impaired oxygen delivery to muscle in chronic fatigue syndrome

Abstract:

The purpose of this study was to determine if chronic fatigue syndrome (CFS) is associated with reduced oxygen delivery to muscles. Patients with CFS according to CDC (Center for Disease Control) criteria (n=20) were compared with normal sedentary subjects (n=12).

Muscle oxygen delivery was measured as the rate of post-exercise and post-ischaemia oxygen-haem resaturation. Oxygen-haem resaturation was measured in the medial gastrocnemius muscle using continuous-wavelength near-IR spectroscopy. Phosphocreatine resynthesis was measured simultaneously using (31)P magnetic resonance spectroscopy.

The time constant of oxygen delivery was significantly reduced in CFS patients after exercise (46.5+/-16 s; mean+/-S.D.) compared with that in controls (29.4+/-6.9 s). The time constant of oxygen delivery was also reduced (20.0+/-12 s) compared with controls (12.0+/-2.8 s) after cuff ischaemia. Oxidative metabolism was also reduced by 20% in CFS patients, and a significant correlation was found between oxidative metabolism and recovery of oxygen delivery.

In conclusion, oxygen delivery was reduced in CFS patients compared with that in sedentary controls. This result is consistent with previous studies showing abnormal autonomic control of blood flow. Reduced oxidative delivery in CFS patients could be specifically related to CFS, or could be a non-specific effect of reduced activity levels in these patients. While these results suggest that reduced oxygen delivery could result in reduced oxidative metabolism and muscle fatigue, further studies will be needed to address this issue.

Comment in: Chronic fatigue syndrome: the physiology of people on the low end of the spectrum of physical activity? [Clin Sci (Lond). 1999]

 

Source: McCully KK, Natelson BH. Impaired oxygen delivery to muscle in chronic fatigue syndrome. Clin Sci (Lond). 1999 Nov;97(5):603-8; discussion 611-3. http://www.ncbi.nlm.nih.gov/pubmed/10545311

 

Demonstration of delayed recovery from fatiguing exercise in chronic fatigue syndrome

Abstract:

Patients with the chronic fatigue syndrome (CFS) complain consistently of delay in recovery of peripheral muscle function after exercise. The purpose of this study was to try to confirm this observation.

A fatiguing exercise test was carried out on the quadriceps muscle group of ten patients and ten control subjects. The test consisted of 18 maximum voluntary contractions (MVCs) with a 50% duty cycle (10 s contraction, 10 s rest), and the force generated by each contraction was recorded using a KinCom dynamometer. This was followed by a recovery phase lasting 200 min in which quadriceps strength was evaluated at increasing intervals, and a follow-up session at 24 h post-exercise involving three 10 s MVCs.

Throughout the exercise period, the MVCs obtained from the control group were significantly higher than those of the patient group (P = 0.006), but both groups showed a parallel decline in force over the 18 contractions, in keeping with a similar endurance capacity.

Recovery was prolonged in the patient group, however, with a significant difference compared to initial MVCs being evident during the recovery phase after exercise (P = 0.001) and also at 24 h (P < 0.001). In contrast, the control group achieved MVCs which were not significantly different from initial values during the recovery phase, and maintained these at 24 h.

These findings support the clinical complaint of delayed recovery after exercise in patients with CFS.

Copyright 1999 Lippincott Williams & Wilkins

 

Source: Paul L, Wood L, Behan WM, Maclaren WM. Demonstration of delayed recovery from fatiguing exercise in chronic fatigue syndrome. Eur J Neurol. 1999 Jan;6(1):63-9. http://www.ncbi.nlm.nih.gov/pubmed/10209352

 

Central basis of muscle fatigue in chronic fatigue syndrome

Abstract:

We studied whether muscle fatigue, metabolism, or activation are abnormal in the chronic fatigue syndrome (CFS). Subjects performed both an intermittent submaximal and a sustained maximal voluntary isometric exercise protocol of the tibialis anterior muscle.

The extent of fatigue, metabolic response, and changes in both M-wave amplitude and twitch tension during exercise were similar in patients and controls. The response to systemic exercise was also normal in the patients. However, voluntary activation of the tibialis was significantly lower in the patients during maximal sustained exercise.

The results indicate that patients with CFS have (1) normal fatigability and metabolism at both the intracellular and systemic levels, (2) normal muscle membrane function and excitation-contraction coupling, and (3) an inability to fully activate skeletal muscle during intense, sustained exercise. This failure of activation was well in excess of that found in controls, suggesting an important central component of muscle fatigue in CFS.

Comment in: Chronic fatigue syndrome. [Neurology. 1993]

 

Source: Kent-Braun JA, Sharma KR, Weiner MW, Massie B, Miller RG. Central basis of muscle fatigue in chronic fatigue syndrome. Neurology. 1993 Jan;43(1):125-31. http://www.ncbi.nlm.nih.gov/pubmed/8423875

 

Cardiac function at rest and with exercise in the chronic fatigue syndrome

Abstract:

To evaluate a possible cardiac pathophysiology of the chronic fatigue syndrome, we compared the resting cardiac function and exercise performance of 41 patients to those of an age-matched and sex-matched normal control group.

Persistent fatigue following an acute apparently viral illness was the major complaint of all patients; none had specific cardiac symptoms nor abnormal physical findings. Electrocardiographic spatial patterns were normal in the patients, and there were no differences in the body surface sum of positive T-wave integrals between the patients (240 microV.x 10(2) +/- 107 microV.s x10(2)) and control (244 microV.x 10(2) +/- 108 microV.s x 10(2) subjects. Twenty-four hour ambulatory ECGs revealed no differences in sinus rates and incidences of ventricular dysrhythmias in the two populations. Left ventricular dimensions and systolic fractional shortening values were also similar in both groups; moreover none of the patients had segmental wall motion abnormalities.

On graded exercise testing, 20 of 32 normal subjects achieved target (85 percent of age-maximum) heart rates, compared to four of 31 patients (p less than 0.001). The duration of exercise averaged 12 +/- 4 minutes for the normal subjects and 9+/- 4 minutes for the patients (p less than 0.01). The temporal profile of exercise heart rates was dissimilar in the two groups, with patients’ rates consistently and progressively less than those of normal subjects. Peak heart rate averaged 152 +/- 16 beats per minute for the normal group vs 124 +/- 19 beats per minute for the patients (p less than 0.0001); in age-related terms, respectively, 82 +/- 6 percent of the maximum heart rate vs 66 +/- 10 percent (p less than 0.0001).

Thus, patients with chronic fatigue syndrome have normal resting cardiac function but a markedly abbreviated exercise capacity characterized by slow acceleration of heart rate and fatigue of exercising muscles long before peak heart rate is achieved.

(ABSTRACT TRUNCATED AT 250 WORDS)

 

Source: Montague TJ, Marrie TJ, Klassen GA, Bewick DJ, Horacek BM. Cardiac function at rest and with exercise in the chronic fatigue syndrome. Chest. 1989 Apr;95(4):779-84. http://www.ncbi.nlm.nih.gov/pubmed/2924607