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PubMed1979

Electromyogram pattern of diaphragmatic fatigue.

We studied the effect of breathing at various levels of transdiaphragmatic pressure (Pdi) on the EMG power spectrum of the diaphragm. The diaphragmatic EMG was measured simultaneously with a bipolar esophageal electrode (EE) and surface electrode (SE) placed on the ventral portion of the sixth and seventh intercostal spaces in five normal subjects breathing at functional residual capacity (FRC) against an inspiratory resistance. During each fatigue run the subjects generated a Pdi, with each inspiration, that was 25, 50, or 75% of maximum Pdi (Pdimax) for a period up to 15 min. During runs at 50 and 75% of the Pdimax, which are known to produce fatigue, we found for both EE and SE a progressive increase in the amplitude of the low-frequency (L = 20-46.7 Hz) and a decrease in the high-frequency (H = 150-350 Hz) component of the EMG. These changes were not seen at 25% of Pdimax. The diaphragmatic H/L ratio was independent of Pdi when the diaphragm was not fatigued. H/L fell while the diaphragm performed fatiguing work and this was more rapid at higher Pdi's. It was thus concluded that frequency spectrum analysis of the EMG can detect diaphragmatic fatigue reliably, prior to the time when the diaphragm fails as a pressure generator.

Diaphragm↗

PubMed2026

Effects of intradialytic nutrition on dialysis adequacy and fatigue in hemodialysis patients: a randomized crossover study.

OBJECTIVE: To assess intradialytic nutrition's effects on dialysis adequacy and fatigue in maintenance hemodialysis patients. METHODS: A randomized, two-period, two-sequence, self-controlled crossover trial was conducted in two outpatient hemodialysis centers in Türkiye. Thirty-six patients were randomized; 32 completed both periods. The participants received standardized intradialytic nutrition in one period and no food intake during the control period. Dialysis adequacy was evaluated using the urea reduction ratio and single-pool Kt/V. Intradialytic blood pressure was recorded during dialysis sessions, and fatigue severity was measured using the Piper Fatigue Scale at the end of each period. RESULTS: No significant differences were observed in dialysis adequacy or fatigue scores between the two periods. Intradialytic nutrition was associated with greater reductions in systolic and diastolic blood pressure, particularly during the second hour of dialysis. No clinically relevant adverse events occurred. CONCLUSION: Intradialytic nutrition did not compromise dialysis adequacy or worsen fatigue severity but was associated with increased intradialytic blood pressure reductions. Individualized clinical decisions and careful hemodynamic monitoring are warranted when implementing intradialytic nutritional interventions. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT07687498.

Humans↗

PubMed1976

Alteration of the maximal activity of the gluconeogenetic enzyme fructose-1,6-diphosphatase of skeletal muscle by cross-reinnervation. A histochemical and biochemical investigation of fatiguability-related aspects.

Fatiguability is a determining characteristic of different muscle fibre types. An important aspect, indirectly related to fatiguability, gluconeogenesis, was investigated by observing fructose-1,6-diphosphatase (FDP) activity in experimental models prepared in rabbits by cross-reinnervation of the fatigue-resistant m.soleus (postural muscle) and the highly fatiguable m.flexor digitorum longus (fast muscle -- m.fdl). The resultant reprogramming of the m. soleus was associated with greatly intensified FDP activity. Changes in the m.fdl 6-9 months after cross-reinnervation indicated a shift in the opposite direction. The study adds some data on the much neglected state of fatiguability to the otherwise much explored field of alien reinnervation.

Animals↗

PubMed1979

Transmission and contraction fatigue of rat motor units in relation to succinate dehydrogenase activity of motor unit fibres.

1. The fatigue in rat anterior tibial (a.t.) motor units was studied and related to microphotometric determinations of succinate dehydrogenase (SDH) activity of the motor unit muscle fibres. 2. Anterior tibial contains fast-twitch type II fibre units with an average contraction time of 11 msec and about 5% slow-twitch type I fibre units with an average contraction time of 20 msec. 3. In type II fibres stained for SDH, absorbance varied continuously from 0.046 to 0.569 and inversely to fibre size, except for the largest fibres. 4. Resistance to fatigue of fast motor units to 100 Hz intermittent stimulation varied continuously within a wide range in near linear relations to absorbance for SDH of unit fibres and inversely to tetanic tension, except for motor units with the largest fibres and the largest tetanic tension. 5. Neither resistance to fatigue nor SDH activity lent itself to any categorization of motor units or fibres into well demarcated functional or histochemical types, since both parameters varied continuously in the unit and fibre population of the muscle. 6. The direct relation between resistance to fatigue of fast-twitch motor units and SDH activity of unit fibres appeared valid for fatigue resistance of: (a) neuromuscular transmission, tested with 100 Hz intermittent stimulation which gave concomitant failure of electrical and mechanical response, (b) excitation--contraction coupling, demonstrated by post-stimulatory depression of twitch tension with preserved maximum tetanus tension and action potential, and (c) contractile mechanism; excitation--contraction coupling?, tested with low frequency stimulation which gave decline of twitch and maximum tetanus tension with preserved action potential. 7. It is suggested that the endurance of each link in the chain of events leading to contraction, including neuromuscular junction and the excitation--contraction coupling system, is under aerobic conditions matched to the contractile capacity of the fibre expressed by its oxidative enzyme activity.

Action Potentials↗

PubMed1978

Fatigue-induced damage in glutaraldehyde-preserved heart valve tissue.

Glutaraldehyde-preserved porcine mitral leaflet tissue has been subjected to extended accelerated fatigue loading in Ringer's solution containing 0.15% glutaraldehyde. Five tissue test pieces were subjected to cyclic tensile stresses of 50 and 200 Gm. per square millimeter and to 300 million to 800 million accumulated fatigue cycles. Tissue disruption occurred in each of the fatigued test pieces. Tensile loading, apart from reducing the acuteness of the collagen waveform and thereby decreasing tissue compliance, does not contribute significantly to the disruption process nor its rate of occurrence. Compressive flexure occurring during the unloading half of the fatigue cycle, however, does induce damage in the tissue. Mechanisms involved in the disruptive processes have been identified by conducting simultaneous morphologic and stress/strain observations on both the fatigued and unfatigued tissues in their wet functional condition. This vulnerability of the preserved tissue to compressive flexure could well affect the long-term durability of the glutaraldehyde-preserved heterograft valve, and this possibility is discussed in relation to the clinical use of these valves.

Animals↗

PubMed2026

Associations of Illness Perception, Resignation Coping, and Social Support With Self-Regulatory Fatigue in Patients With Type 2 Diabetes: A Cross-Sectional Study.

AIMS: To examine the associations among illness perception, resignation coping, social support, and self-regulatory fatigue (SRF) in patients with Type 2 diabetes mellitus. The study specifically explores whether resignation coping and social support exhibit indirect associations with SRF in the context of illness perception. DESIGN: A cross-sectional study. METHODS: From November 2024 to October 2025, a convenience sample of 302 adult patients with T2DM was recruited from a tertiary general hospital in China. Participants completed validated instruments with established psychometric properties, namely the Brief Illness Perception Questionnaire, the Medical Coping Modes Questionnaire, the Perceived Social Support Scale, and the Self-Regulatory Fatigue Scale. Statistical analyses included Spearman correlation and serial mediation analysis using the PROCESS Macro (Model 6) with bias-corrected bootstrapping. RESULTS: SRF was positively correlated with negative illness perception (r = 0.579, p < 0.01) and resignation coping (r = 0.612, p < 0.01), and negatively correlated with social support (r = -0.598, p < 0.01). Serial mediation analysis revealed that illness perception was associated with SRF through indirect pathways involving resignation coping and social support. Resignation coping and social support mediated the association between illness perception and self-regulatory fatigue, both individually and sequentially. CONCLUSIONS: Negative illness perception correlates with higher SRF. This observed correlation is additionally linked to indirect pathways involving resignation coping and lower social support. Collectively, these findings highlight a pattern of interrelated cognitive (illness perception), behavioural (resignation coping), and resource (social support) factors that are associated with self-regulatory fatigue in this cross-sectional study. IMPLICATIONS FOR THE PROFESSION: The findings offer a clear, evidence-based framework for nursing practice. They highlight the potential value of integrated assessment and intervention that simultaneously addresses patients' illness beliefs, maladaptive coping strategies, and social support systems, which are associated with lower SRF and better diabetes self-management. REPORTING METHOD: This study adheres to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines for cross-sectional studies. PATIENT OR PUBLIC CONTRIBUTION: Patients participated solely as research participants by providing survey data. They were not involved in the study design, implementation, data analysis, interpretation, or manuscript preparation. All patients provided written informed consent prior to questionnaire completion.

Humans↗

PubMed1979

Fatigue in ice skating: biomechanical considerations.

This paper attempts to describe how the mechanical patterns in ice skating are affected by muscular fatigue. It reviews several investigations dealing with the effects of muscular fatigue on standing broad jump performance and running. It concludes that fatigue studies dealing with ice skating can be expected to show that the mechanical patterns in ice skating deteriorate as a result of muscular fatigue.

Biomechanical Phenomena↗

PubMed1979

Fatigue - corrosion of endoprosthesis titanium alloys.

Commercial total hip prostheses often show certain metallurgical faults (porosities, coarse grains, growth dendrites, carbide networks). In order to investigate more accurately the role played by these different parameters in prostheses failure we performed a large number of systematic corrosion, fatigue and fatigue - corrosion tests on these materials and on commercial total hip prostheses. Ultimate strengthes seem to be reached for cast cobalt alloys, whereas titanium alloys, such as Ta 6 V, present very high fatigue limit under corrosion. Thus, rotative bending fatigue - corrosion tests in biological environment provide values about 50 DaN/mm2. This value, is nevertheless appreciably higher than those obtained with stellites and stainless steel. Titanium alloys, because of their mechanical performances, their weak Young's modulus (11000 DaN/mm2) and their relative lightness (4.5. g/cm3), which are associated with a good biocompatibility, seem very promising for permanent implants realisation.

Alloys↗

PubMed1978

Ergonomics. Reducing mental and physical fatigue in the dental operatory.

The work output and the mental and physical fatigue generated by a dental procedure is affected by the length and type of operation, physical facilities, the amount of cooperation given by the patient, operating techniques, and the effective teamwork and rapport of the operatory dental team. Fatigue is also generated by stresses that arise outside of the office and which, when superimposed over the normal operating stresses of the office, can have a cumulative effect of decreasing output and increasing mental and physical fatigue for the dentist, the assistant, and the patient. Probably the three most important means to compensate for both routine and nonroutine physical and mental stresses of any type or origin are: (1) learn to cope with or resolve the origin of the stress; (2) develop a pattern of healthy living; (3) cultivate job satisfaction.

Dental Assistants↗

PubMed1975

[Physical and mental fatigue of probable hyperuricemia origin].

A blood uric acid analysis has been effected on 193 Iranians of the intellectual group aged from 25 to 60, of which the normal average rate for 99 women and 94 men of a normal state are (47.5 +/- 2.73) and (53.62 +/- 2.73) respectively. After having controlled the uricemia of these subjects during a period of three years in the three states of healthiness, fatigue or physical strains and sickness, we have been able to note that during physical fatigue and intellectual strains the uricemia presents an augmentation notable as in the case of the sicknesses. Taking into consideration the hyperuricemia resulting from fatigue and strains, it may be noteworthy to be taken into consideration by the clinical laboratories and the physicians as well.

Adult↗

PubMed1979

EMG frequency spectrum, muscle structure, and fatigue during dynamic contractions in man.

Fatigue of the vastus lateralis muscle was studied in healthy well-conditioned students, who differed considerable regarding their muscle fibre type distribution. Muscle force decline during repeated maximum voluntary knee extensions at a constant angular velocity (180 degree X s-1 or rad X s-1), using isokinetic equipment, was taken as the criterion for the degree of fatigue. In an attempt to study quantitative as well as qualitative changes in the EMG pattern, integrated EMG (IEMG) and the frequency of the mean power (MPF), computed from the power spectral density function (PSDF), were analysed. It was found that individuals with muscles made up of a high proportion of fast twitch (FT) muscle fibres demonstrated higher peak knee extension torque, and a greater susceptibility to fatigue than did individuals with muscles mainly composed of slow twitch (ST) muscle fibres. An IEMG decline (p less than 0.01) was demonstrated during 100 contractions in individuals rich in FT fibres. Only a slight, but not significant, reduction in IEMG occurred in individuals with high percentage of ST fibres. Concomitantly, MPF decreased (p less than 0.001) in individuals with a high percentage of FT fibres, while their opposites demonstrated only a slight decrease (non-significant). It is suggested that muscle conctraction failure might also be related to qualitative changes in the motor unit recruitment pattern, and that these changes occur more rapidly in muscles composed of a high proportion of FT muscle fibres than in muscles composed to a high proportion of ST fibres.

Action Potentials↗

PubMed1979

The consequences of diaphragmatic muscle fatigue in the newborn infant.

We have previously demonstrated that diaphragmatic muscle fatigue can be diagnosed in infants from spectral frequency analysis of the surface diaphragmatic electromyogram. This requires a digital computer, but the analysis takes several days. Spectral frequency changes, however, can be accurately reflected by band pass filtering and expressing the ratio of high-frequency power to low-frequency power. A fall in this ratio of greater than 20% indicates muscle fatigue. Using a simple analog device to obtain this ratio permits the results to be immediately available; we have used this method to study weaning from mechanical ventilators in ten infants. With a successful weaning step there is no significant change in the ratio, whereas an unsuccessful weaning step invariably leads to a decrease in the ratio of greater than 20%, which precedes CO2 retention and clinical deterioration. These data indicate that diaphragmatic muscle fatigue plays an important role in the infant's response to lung disease. Monitoring of the high/low frequency ratio may be helpful in weaning infants from assisted ventilation.

Computers, Analog↗

PubMed1978

Composition of vacuoles and sarcoplasmic reticulum in fatigued muscle: electron probe analysis.

Electron probe analysis, cryo-ultramicrotomy, and freeze-substitution were used to determine the nature of vacuolation and the subcellular composition in fatigued frog skeletal muscle fibers. The vacuoles caused by fatigue were part of the T-tubule system and contained high concentrations of NaCl. The calcium concentration in the terminal cisternae was higher than previously measured normal resting values. Mitochondrial calcium content was relatively low (mean +/- SEM, 2 +/- 2 mmol/kg dry weight). Fiber NaCl was increased. It is concluded that fatigue is not due to the depletion of calcium stores from the terminal cisternae or to uncoupling of mitochondria due to calcium loading but may be caused by multiple mechanisms including failure of the T-tubule action potential.

Animals↗

PubMed1978

Effect of fatigue and alcohol on observer perception.

A test series of chest radiographs containing pseudonodules was used to establish baseline sensitivity, specificity, and accuracy rates for individual observers. This experiment studies the effect of fatigue (as subjectively measured) and alcohol (as measured by blood alcohol levels) on observer perception and performance. The results indicate that the fatigue encountered in the course of ordinary professional activities has no significant effect on diagnostic accuracy. Modest quantities of alcohol may adversely influence diagnostic sensitivity, but the effect is unpredictable. Subjective estimates of the influence of fatigue or alcohol on performance by individual observers are frequently erroneous.

Ethanol↗

PubMed1979

[Fatigue fracture of the patella in cerebral palsy (author's transl)].

Amongst approximately 1 500 spastic children under treatment, the authors have seen three cases of fatigue fracture of the patella. One patient was spastic and two others were athetotic. The fatigue fractures can be explained by a flexed knee gait aggravated by a contracture of the hamstring tendons. No fracture was seen in patients treated by Egger's operation. It is concluded that this procedure both prevents and cures fatigue fracture of the patella.

Adolescent↗

PubMed1977

Fatigue characteristics of posterior elements of vertebrae.

The fatigue strength of vertebral posterior elements was determined by applying repetitive forces to the inferior joints between the articular processes of human rhesus-monkey vertebrae. The results indicate that in vivo stresses resulting from unusual activities for sustained periods can induce fatigue fracture of the lumbar vertebrae. Comparison of these data with those of other investigators suggests the use of ultimate strength as a normalizing factor to correlate fatigue-strength data obtained under different test conditions.

Animals↗

PubMed1979

[Stress and fatigue].

Investigations into fatigue are very important for development of labour and sports physiology. Many occupations in modern industry do not often show apparent fatigue. This is the reason for the interest shown for occupational strain sgudies. Occupational strain has proved to have laws of optimum. In some occupational situations work is performed at a different than the optimum, level. It is important to take into consideration general and local strain as well as specific and unspecific components of strain. The fatigue level is a significant sign characterizing the occupational strain.

Fatigue↗

PubMed1979

The influence of grain size on the fatigue behavior of annealed 316 LVM stainless steel.

Experimental tests demonstrate that there is a sharp drop in resistance to fatigue fracture when the grain size is increased from 75 to 150 micrometers. This is at least a partial explanation for fatigue fractures of the stems of total hip-joint prostheses reported in the literature. It is also shown that plastic strains associated with fatigue stressing increase with increasing grain size so that loosening of the bone cement embedment may also be part of the premature failure process.

Hip Joint↗