Category: Exercise

Post-viral fatigue syndrome. A longitudinal assessment in varsity athletes

Abstract:

Maximal oxygen uptake, anaerobic threshold (AT), isometric strength of the elbow flexor and knee extensor muscles, isometric strength endurance exhaustion time (prolonged contraction at 66% of maximal isometric strength), uphill sprinting exhaustion time were longitudinally studied in eight varsity endurance runners with post-viral fatigue syndrome (PVFS).

Prolonged impairment of exercise performance is evident during the course of PVFS. Although maximal oxygen uptake (VO2max) had returned to pre-infection values 13 months after the viral illness (4.160 vs 4.0 L.min-1), AT was still significantly reduced [52 ml.kg-1.min-1, 18.6 km.hr-1, 176 bpm, and 82% of VO2max vs. 49.1 ml.kg-1.min-1 (p < 0.05), 175 bpm (NS), 17.2 km.hr-1 (p < 0.01) and 79% of VO2max (NS)].

Maximal isometric contraction strength of the upper limb remained constant (282 N vs. 274 N), while knee extensor muscles strength decreased significantly (730 N vs. 701 N, p < 0.05). Strength endurance was still significantly reduced by the end of the study (arm average pre-infection: 46.2 sec; end of study: 29.3 sec, p < 0.001; leg average pre-infection: 66.4 sec; end of study: 49.1 sec, p < 0.01). Up hill sprinting time was similarly reduced by the end of the study period (29.3 sec vs. 16.2 sec, p < 0.01).

Both aerobic and anaerobic exercise variables are seriously affected by post-viral fatigue syndrome, and one year may not be sufficient to fully recover.

 

Source: Maffulli N, Testa V, Capasso G. Post-viral fatigue syndrome. A longitudinal assessment in varsity athletes. J Sports Med Phys Fitness. 1993 Dec;33(4):392-9. http://www.ncbi.nlm.nih.gov/pubmed/8035588

 

The grey area of effort syndrome and hyperventilation: from Thomas Lewis to today

Abstract:

Lewis used the diagnosis ‘effort syndrome’ for subjects whose ability to make and sustain effort had been reduced by homeostatic failure. A major element was depletion of the body’s capacity for buffering the acids produced by exercise.

In his view this systems disorder was not to be regarded as a specific organ disease, and losing sight of the metabolic element would foster the invention of fanciful, unphysiological diagnoses. His views were dismissed because normal resting plasma bicarbonate levels were considered by others in that era to exclude serious depletion of the body’s total capacity for buffering the effects of exertion.

Today, effort syndrome is still a useful diagnosis for a condition of exhaustion and failure of performance associated with depletion of the body’s buffering systems. Other elements associated with homeostatic failure are now recognised, principally emotional hyperarousal and hyperventilation. Their physiological interrelationships are described. Effort syndrome is amenable to recovery through rehabilitation, and it may be a mistake to treat chronic fatigue syndrome and unspecific illness without including it in the differential diagnosis.

 

Source: Nixon PG. The grey area of effort syndrome and hyperventilation: from Thomas Lewis to today. J R Coll Physicians Lond. 1993 Oct;27(4):377-83. http://www.ncbi.nlm.nih.gov/pubmed/8289156

 

Exercise performance and fatiguability in patients with chronic fatigue syndrome

Abstract:

To examine the role of delay in recovery of peripheral muscle function following exercise in the fatigue experienced by patients with the chronic fatigue syndrome (CFS) and to examine the influence of effort perception in limiting exercise performance in these patients, a study was carried out on a group of twelve patients with chronic fatigue syndrome and 12 sex and age-matched sedentary control subjects.

Symptom limited incremental cycle exercise tests including measurements of perceived exertion were performed followed by examination of the contractile properties of the quadriceps muscle group for up to 48 hours. Muscle function was assessed by percutaneous electrical stimulation and maximum voluntary contractions.

Muscle function at rest and during recovery was normal in CFS patients as assessed by maximum isometric voluntary contraction, 20:50 Hz tetanic force ratio and maximum relaxation rate. Exercise duration and the relationship between heart rate and work rate during exercise were similar in both groups.

CFS patients had higher perceived exertion scores in relation to heart rate during exercise representing a reduced effort sensation threshold of 3.2 units on an unmodified Borg scale in CFS patients. Patients with chronic fatigue syndrome show normal muscle physiology before and after exercise. Raised perceived exertion scores during exercise suggest that central factors are limiting exercise capacity in these patients.

Comment in: Lactate responses to exercise in chronic fatigue syndrome. [J Neurol Neurosurg Psychiatry. 1994]

 

Source: Gibson H, Carroll N, Clague JE, Edwards RH. Exercise performance and fatiguability in patients with chronic fatigue syndrome. J Neurol Neurosurg Psychiatry. 1993 Sep;56(9):993-8. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC489735/ (Full article)

 

Muscle histopathology and physiology in chronic fatigue syndrome

Abstract:

Chronic fatigue syndrome (CFS) is characterized by fatigue at rest which is made worse by exercise. Previous biopsy studies on small numbers of CFS patients have shown a range of morphological changes to which have been attributed fatigue and myalgia.

We have now studied 108 patients with CFS or muscle pain and 22 normal volunteers by light and electron microscopy. There was no consistent correlation between symptoms and changes in fibre type prevalence, fibre size, degenerative or regenerative features, glycogen depletion, or mitochondrial abnormalities. Physiological contractile properties of quadriceps (maximal isometric force generation, frequency: force characteristics and relaxation rate) were also examined before and for up to 48 hours after a symptom-limited incremental cycle ergometer exercise test in 12 CFS patients and 12 normal volunteers.

Voluntary and stimulated force characteristics were normal at rest and during recovery. Exercise duration was similar in the two groups although CFS patients had higher perceived exertion scores in relation to heart rate during exercise, indicating a reduced effort sensation threshold. On physiological and pathological grounds it is clear that CFS is not a myopathy. Psychological/psychiatric factors appear to be of greater importance in this condition.

 

Source: Edwards RH1, Gibson H, Clague JE, Helliwell T. Muscle histopathology and physiology in chronic fatigue syndrome. Ciba Found Symp. 1993;173:102-17; discussion 117-31. http://www.ncbi.nlm.nih.gov/pubmed/8491096

 

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

 

Skeletal muscle metabolism in the chronic fatigue syndrome. In vivo assessment by 31P nuclear magnetic resonance spectroscopy

Abstract:

BACKGROUND: Previous study of patients with chronic fatigue syndrome (CFS) has demonstrated a markedly reduced dynamic exercise capacity, not limited by cardiac performance and in the absence of clinical neuromuscular dysfunction, suggesting the possibility of a subclinical defect of skeletal muscle.

METHODS: The in vivo metabolism of the gastrocnemius muscles of 22 CFS patients and 21 normal control subjects was compared during rest, graded dynamic exercise to exhaustion and recovery, using 31P nuclear magnetic resonance (NMR) spectroscopy to reflect minute-to-minute intracellular high-energy phosphate metabolism.

RESULTS: Duration of exercise was markedly shorter in the CFS patients (8.1 +/- 2.8 min) compared with the normal subjects (11.3 +/- 4.3 min) (p = 0.005). There were large changes in phosphocreatine (PCr), inorganic phosphate (Pi), and pH from rest to clinical fatigue in all subjects, reflecting the high intensity of the exercise. The temporal metabolic patterns were qualitatively similar in the CFS patients and normal subjects. There were early and continuous changes in PCr and Pi that peaked at the point of fatigue and rapidly reversed after exercise. In contrast, pH was relatively static in early exercise, not declining noticeably until 50 percent of total exercise duration was achieved, and reaching a nadir at 2 min postexercise, before rapidly reversing. There were no differences in pH at rest (7.08 +/- 0.04 vs 7.10 +/- 0.04), exhaustion (6.85 +/- 0.17 vs 6.76 +/- 0.17) or early (6.64 +/- 0.25 vs 6.56 +/- 0.24) or late recovery (7.09 +/- 0.04 vs 7.10 +/- 0.05), CFS patients vs normal subjects, respectively (NS). Neither were there intergroup differences (NS) in PCr or Pi. Although, quantitatively, the changes in PCr, Pi, and pH were marked and similar in both groups from rest to exhaustion, the changes all occurred much more rapidly in the CFS patients. Moreover, adenosine triphosphate (ATP) was significantly (p = 0.007) less at exhaustion in the CFS group.

CONCLUSIONS: Patients with CFS and normal control subjects have similar skeletal muscle metabolic patterns during dynamic exercise and reach similar clinical and metabolic end points. However, CFS patients reach exhaustion much more rapidly than normal subjects, at which point they also have relatively reduced intracellular concentrations of ATP. These data suggest a defect of oxidative metabolism with a resultant acceleration of glycolysis in the working skeletal muscles of CFS patients. This metabolic defect may contribute to the reduced physical endurance of CFS patients. Its etiology is unknown. Whether CFS patients’ overwhelming tiredness at rest has a similar metabolic pathophysiology or etiology also remains unknown.

 

Source: Wong R1, Lopaschuk G, Zhu G, Walker D, Catellier D, Burton D, Teo K, Collins-Nakai R, Montague T. Skeletal muscle metabolism in the chronic fatigue syndrome. In vivo assessment by 31P nuclear magnetic resonance spectroscopy. Chest. 1992 Dec;102(6):1716-22. http://www.ncbi.nlm.nih.gov/pubmed/1446478

 

Chronic fatigue syndrome: a joint paediatric-psychiatric approach

Comment in: Chronic fatigue syndrome: a joint paediatric-psychiatric approach. [Arch Dis Child. 1992]

 

Prolonged fatigue after an apparent viral infection, occurring sporadically or as an epidemic, has been described over the past 50 years. It has been given various names including Royal Free disease (1) and myalgic encephalomyelitis, but the preferred terms in the medical literature have been postviral fatigue syndrome (2) or chronic fatigue syndrome (CFS). (3)

However, the validity of this syndrome as a nosological entity has created a good deal of controversy and remains in doubt. (4) A constellation of symptoms make up the syndrome. There is fatigue of defined onset that is generally reported to follow a viral illness, often an influenza-like illness or an infection of the upper respiratory tract. The patient experiences profound fatigue with the initial illness and then fails to make the expected recovery, with fatigue that can persist over months or years. Fatigue is defined as a subjective sensation, which the patient often describes as tiredness or weariness and that occurs at rest. These patients also report a clear relationship of fatigue to activity. The term fatiguability has been used to describe the greater than normal fatigue that occurs after physical and sometimes after mental exertion in these patients. A great variety of associated symptoms have been described that include increased sleepiness, dizziness, vertigo, headache, difficulty in concentrating, sore throat, muscle weakness, and myalgia. The majority of patients have some emotional symptoms. There can be irritability and anxiety, tearfulness and depression. The fatigue and associated symptoms are of such severity as to impair significantly normal daily activities. There is a remarkable absence of physical signs and physical investigations fail to detect any organic pathology or current infection to account for the symptoms.

You can read the rest of this article here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1793327/pdf/archdisch00639-0088.pdf

 

Source: Vereker MI. Chronic fatigue syndrome: a joint paediatric-psychiatric approach. Arch Dis Child. 1992 Apr;67(4):550-5. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1793327/

 

Human quadriceps strength and fatiguability in patients with post viral fatigue

Abstract:

Quadriceps isometric strength, activation and fatiguability were measured in 11 patients with symptoms of fatigue three months after glandular fever or a glandular fever-like illness.

Predicted normal and lower limits of normal muscle strength were calculated from height and age. These measures and the fatigue index were compared with a group of healthy students of similar age.

Two of the patients were unable to activate fully their muscles. After allowing for this inhibition the group mean (SD) strength was 104 (22%) of predicted. Although there was no significant difference in the fatigue index between the patients and the control group, there was a trend for the patients to show less fatigue than controls.

There was no difference in the muscle results for those patients who were found to have Epstein-Barr virus infections and those who did not. The feelings of weakness and fatigue experienced by the patients could not be explained by either physiological muscle fatigue or lack of effort.

 

Source: Rutherford OM, White PD. Human quadriceps strength and fatiguability in patients with post viral fatigue. J Neurol Neurosurg Psychiatry. 1991 Nov;54(11):961-4. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1014616/ (Full article)

 

Muscle performance, voluntary activation, twitch properties and perceived effort in normal subjects and patients with the chronic fatigue syndrome

Abstract:

The decrease in maximal force-generating capacity, the degree of central activation of the muscle, and the subjective perception of effort were measured during prolonged submaximal isometric exercise in 12 male patients suffering from the ‘chronic fatigue syndrome’ and 13 naive, healthy male subjects.

Maximal voluntary isometric torque generated by the elbow flexors was measured before, and at 5 min intervals during an endurance sequence of 45 min of repetitive isometric contractions (6 s duration, 4 s rest interval) producing 30% of the initial maximal voluntary torque. Electrical stimuli were also delivered to the elbow flexors to measure the contractile force in the intervals between voluntary contractions. The degree of central motor activation during maximal voluntary contractions was assessed using a sensitive method of twitch interpolation.

In addition, the perceived effort required to achieve the target submaximal contractions was recorded using a standardized self-report scale. A high degree of central activation was achieved in maximal contractions during the endurance sequence both in the patients (mean of maximal force 93.6%; SD 7.8%), and in the control subjects (mean 90.9%; SD 9.5%).

The relative torque produced by either voluntary or electrically stimulated contractions was not significantly different between patients and control subjects throughout the test. There was no significant difference in the perceived exertion between the patients and control subjects.

These findings support the concept that neither poor motivation, nor muscle contractile failure is important in the pathogenesis of ‘fatigue’ in patients with the chronic fatigue syndrome.

 

Source: Lloyd AR, Gandevia SC, Hales JP. Muscle performance, voluntary activation, twitch properties and perceived effort in normal subjects and patients with the chronic fatigue syndrome. Brain. 1991 Feb;114 ( Pt 1A):85-98. http://www.ncbi.nlm.nih.gov/pubmed/1998892

 

Physiologic measurement of exercise and fatigue with special reference to chronic fatigue syndrome

Abstract:

Oxidative metabolism is the major source of energy for muscle activity, and maximal oxygen uptake (VO2max), the product of maximal cardiac output and maximal arteriovenous oxygen difference, indicates individual capacity for oxidative metabolism and performance of exercise by the large muscles.

Strength, a function of muscle cross-sectional area, motor-unit recruitment, and neuromuscular coordination, is the ability to develop force in a single, brief, maximal-effort voluntary contraction of rested muscle. Weakness is a diminished ability of rested muscle to exert maximal force. Fatigue is a loss of maximal force-generating capacity that develops during muscular activity, likely originates within muscle itself, and persists until muscle is fully recovered. Individual perception of motor effort can be determined with standardized rating scales.

These concepts are discussed in detail, their relevance to the pathophysiology of exercise in chronic fatigue syndrome is analyzed, and a general strategy of exercise evaluation pertinent to chronic fatigue syndrome is presented.

 

Source: Lewis SF, Haller RG. Physiologic measurement of exercise and fatigue with special reference to chronic fatigue syndrome. Rev Infect Dis. 1991 Jan-Feb;13 Suppl 1:S98-108. http://www.ncbi.nlm.nih.gov/pubmed/2020810