"Biomarkers of peripheral muscle fatigue during exercise" (Finsterer, 2012) (free full text)

[Dolphin]

Free full text at: http://www.biomedcentral.com/content/pdf/1471-2474-13-218.pdf

This looks like it could be an interesting paper. 4 CFS studies are referenced.

Biomarkers of peripheral muscle fatigue during exercise

BMC Musculoskeletal Disorders 2012, 13:218 doi:10.1186/1471-2474-13-218

Josef Finsterer (fipaps@yahoo.de)

Abstract* (provisional)

Background

Biomarkers of peripheral muscle fatigue (BPMFs) are used to offer insights into mechanisms of exhaustion during exercise in order to detect abnormal fatigue or to detect defective metabolic pathways.

This review aims at describing recent advances and future perspectives concerning the most important biomarkers of muscle fatigue during exercise.

Results

BPMFs are classified according to the mechanism of fatigue related to adenosine-triphosphate-metabolism, acidosis, or oxidative-metabolism.

Muscle fatigue is also related to an immunological response. impaired calcium handling, disturbances in bioenergetic pathways, and genetic responses.

The immunological and genetic response may make the muscle susceptible to fatigue but may not directly cause muscle fatigue.

Production of BPMFs is predominantly dependent on the type of exercise.

BPMFs need to change as a function of the process being monitored, be stable without appreciable diurnal variations, correlate well with exercise intensity, and be present in detectable amounts in easily accessible biological fluids.

The most well-known BPMFs are serum lactate and interleukin-6.

The most widely applied clinical application is screening for defective oxidative metabolism in mitochondrial disorders by means of the lactate stress test.

The clinical relevance of most other BPMFs, however, is under debate, since they often depend on age, gender, physical fitness, the energy supply during exercise, the type of exercise needed to produce the BPMF, and whether healthy or diseased subjects are investigated.

Conclusions

Though the role of BPMFs during fatigue is poorly understood, measuring BPMFs under specific, standardised conditions appears to be helpful for assessing biological states or processes during exercise and fatigue.

I gave each sentence its own paragraph

 

[Firestormm]

Thanks Dolphin. I like these reviews. So much easier to read and understand. Useful for reference too.

Little controversial perhaps but I can handle it for the bio-information it contains:

Fatigue in response to exercise (exercise (-induced) fatigue) can be caused by mental disorders, organic central nervous system (CNS) abnormalities (central fatigue), or by peripheral nervous system (PNS) dysfunction or skeletal muscle disease (peripheral, muscle, contractile, or mechanical fatigue, contractile impairment, loss of force generating capacity)

[1,2]. Factors that contribute to feeling tired include neurological and non-neurological
causes [3].

Neurological causes include:
Central fatigue
Mental disorders
Organic CNS abnormalities
Peripheral fatigue
PNS (neural adaptations)
Skeletal muscle diseases (contractile fatigue, contractile impairment)

Non-neurological causes include:
Cardiac disorders
Pulmonary disorders (e.g. chronic obstructive pulmonary disease (COPD)
Hematologic disorders
Metabolic diseases
Renal problems
Malignancies
Overtraining syndrome
Chronic fatigue syndrome (CFS)

Exercise-induced muscle fatigue has to be clearly delineated from fatigability in the resting stage (fatigue prior to exercise), which may be caused by similar or other factors than exercise-induced muscle fatigue.

Exercise-induced muscle fatigue is defined as a reversible loss of muscle force (muscle contractility) during work over time (peripheral muscle fatigue during exercise) [4,5].

Clinically useful biomarkers are available to quantify the degree and course of muscle fatigue during exercise and disease.

This review is directed towards researchers and clinicians and aims to describe recent advances and future perspectives concerning the most important biomarkers of muscle fatigue during exercise.

Exercise-induced muscle fatigue, fatigability, tiredness, and recovery

Muscle fatigue is defined as decreased ability to generate appropriate amounts of muscle force or power during on-going contractile activity. Muscle fatigue may vary according to the cause or underlying mechanisms, with variable rates of recovery.

For example, fatigue brought on by a marathon is different from fatigue that prevents a 10th bench press repetition at a given resistance.

Exercise-induced muscle fatigue can occur shortly after onset of exercise (acute muscle fatigue) or after a constant, high-intensity exercise had been carried out for a prolonged period of time (delayed exercise-induced fatigue), which is characterized by tiredness only after a longer duration of constant exercise.

Acute muscle fatigue is usually maximal immediately post-exercise. Exercise-induced muscle fatigue can develop under a sub-maximal as well as maximal intensity exercise.

Exercise-induced fatigue can occur in healthy or diseased subjects, and depends on age, gender, physical fitness, mode and duration of exercise, and the underlying disease.

Contrary to fatigue, the term fatigability is defined as rate of loss of muscle force over time.

Fatigability is an interactive determinant of the state of fatigue versus rested. Only few studies have addressed the relation between fatigability and biomarkers of muscle fatigue.

Muscle fatigue has to be delineated from the sensation of tiredness. Muscle fatigue that develops during sub-maximal aerobic exercise is not necessarily reflected by a sensation of tiredness, but a reduced ability to develop force and power.

Recovery from fatigue is defined as the rate at which muscle function returns to baseline after becoming fatigued.

Recovery represents an important marker of fatigue severity and biomarker responsiveness. Like
fatigability, recovery represents an interactive determinant of the state of fatigue versus rested.

Both, fatigue severity and recovery are influenced by fatigability and the degree to which muscle dysfunction is provoked.

Will continue reading later.