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1.
PLoS One ; 17(4): e0266370, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35363812

RESUMO

BACKGROUND: Altered movement patterns have been proposed as an etiological factor for the development of musculoskeletal pain. Fatigue influences upper limb kinematics and movement performance which could extend to the contralateral limb and potentially increasing risk of injury. The aim of this study was to investigate the impact of fatigue at the dominant arm on the contralateral upper limb movement. METHODS: Forty participants were randomly assigned to one of two groups: Control or Fatigue Group. All participants completed a reaching task at the baseline and post-experimental phase, during which they reached four targets with their non-dominant arm in a virtual reality environment. Following the baseline phase, the Fatigue Group completed a shoulder fatigue protocol with their dominant arm only, while the Control Group took a 10-minute break. Thereafter, the reaching task was repeated. Upper limb and trunk kinematics (joint angles and excursions), spatiotemporal (speed and accuracy) and surface electromyographic (sEMG) activity (sEMG signal mean epoch amplitude and median frequency of the EMG power spectrum) were collected. Two-way repeated-measures ANOVA were performed to determine the effects of Time, Group and of the interaction between these factors. RESULTS: There was a significant Time x Group interaction for sternoclavicular elevation range of motion (p = 0.040), movement speed (p = 0.043) and accuracy (p = 0.033). The Fatigue group showed higher contralateral sternoclavicular elevation and increased movement error while experiencing fatigue in the dominant arm. Moreover, the Control group increased their speed during the Post-experimental phase compared to baseline (p = 0.043), while the Fatigue group did not show any speed improvement. There was no EMG sign of fatigue in any of the muscles evaluated. CONCLUSION: This study showed that fatigue at the dominant shoulder impacts movement at the contralateral upper limb. Such changes may be a risk factor for the development of shoulder pain in both the fatigued and non-fatigued limbs.


Assuntos
Fadiga , Ombro , Fenômenos Biomecânicos , Humanos , Movimento/fisiologia , Fadiga Muscular/fisiologia , Ombro/fisiologia
2.
PLoS One ; 17(4): e0266390, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35363820

RESUMO

Work-related upper extremity disorders are costly to society due to resulting medical costs, presenteeism and absenteeism. Although their aetiology is likely multifactorial, physical workplace factors are known to play an important role in their development. Promising options for preventing work-related upper extremity disorders include assistive technologies such as dynamic arm supports designed to follow the movement of the arm while compensating for its weight. The objective of this study was to assess the effects of a dynamic arm support on perceived exertion, muscle activity and movement patterns of the upper limb during repetitive manual tasks in healthy individuals. Thirty healthy right-handed individuals were allocated either a static or a dynamic task to perform with and without a dynamic arm support. During the task, surface electromyographic activity (anterior and middle deltoid, upper trapezius) and upper limb kinematics (elbow, shoulder, sternoclavicular) were measured using surface EMG and inertial sensors. Results showed that the dynamic arm support significantly reduced perceived exertion during the tasks and limited the development of muscular fatigue of the anterior and middle deltoid as demonstrated by EMG signal mean epoch amplitudes and median frequency of the EMG power spectrum. The dynamic arm support also prevented a decrease in shoulder elevation and an increase in total shoulder joint excursion during static and dynamic task, respectively. These results denote the potential benefits of dynamic arm supports in work environments. Further studies should focus on their efficacy, acceptability and implementability in work settings.


Assuntos
Braço , Fadiga Muscular , Braço/fisiologia , Fenômenos Biomecânicos , Eletromiografia/métodos , Humanos , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia , Ombro/fisiologia , Extremidade Superior/fisiologia
3.
Sensors (Basel) ; 22(7)2022 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-35408403

RESUMO

The reliable assessment of muscle states, such as contracted muscles vs. non-contracted muscles or relaxed muscles vs. fatigue muscles, is crucial in many sports and rehabilitation scenarios, such as the assessment of therapeutic measures. The goal of this work was to deploy machine learning (ML) models based on one-dimensional (1-D) sonomyography (SMG) signals to facilitate low-cost and wearable ultrasound devices. One-dimensional SMG is a non-invasive technique using 1-D ultrasound radio-frequency signals to measure muscle states and has the advantage of being able to acquire information from deep soft tissue layers. To mimic real-life scenarios, we did not emphasize the acquisition of particularly distinct signals. The ML models exploited muscle contraction signals of eight volunteers and muscle fatigue signals of 21 volunteers. We evaluated them with different schemes on a variety of data types, such as unprocessed or processed raw signals and found that comparatively simple ML models, such as Support Vector Machines or Logistic Regression, yielded the best performance w.r.t. accuracy and evaluation time. We conclude that our framework for muscle contraction and muscle fatigue classifications is very well-suited to facilitate low-cost and wearable devices based on ML models using 1-D SMG.


Assuntos
Contração Muscular , Músculo Esquelético , Eletromiografia/métodos , Humanos , Contração Muscular/fisiologia , Fadiga Muscular/fisiologia , Músculo Esquelético/diagnóstico por imagem , Músculo Esquelético/fisiologia , Transdutores , Ultrassonografia/métodos
4.
Artigo em Inglês | MEDLINE | ID: mdl-35427223

RESUMO

OBJECTIVE: A critical limitation in clinical applications using functional electrical stimulation (FES) for rehabilitation exercises is the rapid onset of muscle fatigue. Spatially distributed sequential stimulation (SDSS) has been demonstrated to reduce muscle fatigue during FES compared to conventional single electrode stimulation (SES) in single joint movements. Here we investigated the fatigue reducing ability of SDSS in a clinical application, i.e., FES-rowing, in able-bodied (AB) participants. METHODS: FES was delivered to the quadriceps and hamstring of 15 AB participants (five female, ten male) for fatiguing FES-rowing trials using SES and SDSS, participants rowed with voluntary arm effort while endeavoring to keep their legs relaxed. Fatigue was characterized by the time elapsed until a percent decrease occurred in power output (TTF), as well as the trial length indicating the time elapsed until the complete stop of rowing. RESULT: Trial length was significantly longer in SDSS rowing than in SES (t-test, , d=0.71 ), with an average SDSS:SES trial length ratio of 1.31 ± 0.47. TTF SDSS was significantly longer than TTF SES with a median TTF SDSS :TTF SES ratio of 1.34 ranging from 1.03 to 5.41 (Wilcoxon Ranked Sum, , r=0.62 ). No rower experienced a decrease in TTF with SDSS. CONCLUSION: SDSS reduced fatigue during FES-rowing when compared to SES in AB individuals, resulting in a lengthened FES-rowing period by approximately 30%. Application of SDSS would increase the effectiveness of FES-rowing as rehabilitative exercise for individuals with paralyses.


Assuntos
Terapia por Estimulação Elétrica , Traumatismos da Medula Espinal , Esportes Aquáticos , Estimulação Elétrica , Terapia por Estimulação Elétrica/métodos , Feminino , Humanos , Perna (Membro) , Masculino , Fadiga Muscular/fisiologia , Traumatismos da Medula Espinal/reabilitação
5.
J Neuromuscul Dis ; 9(3): 397-409, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35466947

RESUMO

BACKGROUND: Exercise intolerance is an important impairment in patients with SMA, but little is known about the mechanisms underlying this symptom. OBJECTIVE: To investigate if reduced motor unit and capillary recruitment capacity in patients with SMA contribute to exercise intolerance. METHODS: Adolescent and adult patients with SMA types 3 and 4 (n = 15) and age- and gender matched controls (n = 15) performed a maximal upper body exercise test. We applied respiratory gas analyses, non-invasive surface electromyography (sEMG) and continuous wave near-infrared spectroscopy (CW-NIRS) to study oxygen consumption, arm muscle motor unit- and capillary recruitment, respectively. RESULTS: Maximal exercise duration was twofold lower (p < 0.001) and work of breathing and ventilation was 1.6- and 1.8-fold higher (p < 0.05) in patients compared to controls, respectively. Regarding motor unit recruitment, we found higher normalized RMS amplitude onset values of sEMG signals from all muscles and the increase in normalized RMS amplitudes was similar in the m. triceps brachii, m. brachioradialis and m. flexor digitorum in SMA compared to controls. Median frequency, onset values were similar in patients and controls. We found a similar decrease in median frequencies of sEMG recordings from the m. biceps brachii, a diminished decrease from the m. brachioradialis and m. flexor digitorum, but a larger decrease from the m. triceps brachii. With respect to capillary recruitment, CW-NIRS recordings in m. biceps brachii revealed dynamics that were both qualitatively and quantitatively similar in patients and controls. CONCLUSION: We found no evidence for the contribution of motor unit and capillary recruitment capacity of the upper arm muscles in adolescent and adult patients with SMA types 3 and 4 as primary limiting factors to premature fatigue during execution of a maximal arm-cycling task.


Assuntos
Fadiga Muscular , Atrofia Muscular Espinal , Adolescente , Adulto , Braço , Eletromiografia/métodos , Fadiga , Humanos , Fadiga Muscular/fisiologia
6.
J Exp Biol ; 225(9)2022 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-35413119

RESUMO

This study examined the effect of stimulation frequency (140, 200, 230 and 260 Hz) on isometric force, work loop (WL) power and the fatigue resistance of extensor digitorum longus (EDL) muscle (n=32), isolated from 8- to 10-week-old CD-1 female mice. Stimulation frequency had significant effects on isometric properties of isolated mouse EDL, whereby increasing stimulation frequency evoked increased isometric force, quicker activation and prolonged relaxation (P<0.047) up to 230 Hz and above; thereafter, force and activation did not differ (P>0.137). Increasing stimulation frequency increased maximal WL power output (P<0.001; 140 Hz, 71.3±3.5; 200 Hz, 105.4±4.1; 230 Hz, 115.5±4.1; 260 Hz, 121.1±4.1 W kg-1), but resulted in significantly quicker rates of fatigue during consecutive WLs (P<0.004). WL shapes indicate impaired muscle relaxation at the end of shortening and subsequent increased negative work appeared to contribute to fatigue at 230 and 260 Hz, but not at lower stimulation frequencies. Cumulative work was unaffected by stimulation frequency, except at the start of the fatigue protocol, where 230 and 260 Hz produced more work than 140 Hz (P<0.039). We demonstrate that stimulation frequency affects force, power and fatigue, but these effects are not uniform between different assessments of contractile performance. Therefore, future work examining the contractile properties of isolated skeletal muscle should consider increasing the stimulation frequency beyond that needed for maximal force when examining maximal power but should utilise a sub-maximal stimulation frequency for fatigue assessments to avoid a high degree of negative work atypical of in vivo function.


Assuntos
Fadiga Muscular , Músculo Esquelético , Animais , Estimulação Elétrica , Feminino , Masculino , Fenômenos Mecânicos , Camundongos , Contração Muscular/fisiologia , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia
7.
Exp Brain Res ; 240(5): 1423-1434, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35288782

RESUMO

Non-local muscle pain may impair endurance performance through neurophysiological mechanisms, but these are relatively unknown. This study examined the effects of muscle pain on neuromuscular and neurophysiological responses in the contralateral limb. On separate visits, nine participants completed an isometric time to task failure (TTF) using the right knee extensors after intramuscular injection of isotonic saline (CTRL) or hypertonic saline (HYP) into the left vastus lateralis. Measures of neuromuscular fatigue were taken before, during and after the TTF using transcranial magnetic stimulation (TMS) and peripheral nerve stimulation. Mean pain intensity was greater in the left leg in HYP (3.3 ± 1.9) compared to CTRL (0.4 ± 0.7; P < 0.001) which was combined with a reduced TTF by 9.8% in HYP (4.54 ± 0.56 min) compared to CTRL (5.07 ± 0.77 min; P = 0.005). Maximum voluntary force was not different between conditions (all P > 0.05). Voluntary activation was lower in HYP compared to CTRL (P = 0.022). No difference was identified between conditions for doublet amplitude (P > 0.05). Furthermore, no difference in MEP·Mmax-1 or the TMS silent period between conditions was observed (all P > 0.05). Non-local pain impairs endurance performance of the contralateral limb. This impairment in performance is likely due to the faster attainment of the sensory tolerance limit from a greater amount of sensory feedback originating from the non-exercising, but painful, left leg.


Assuntos
Fadiga Muscular , Mialgia , Eletromiografia , Potencial Evocado Motor/fisiologia , Humanos , Joelho/fisiologia , Fadiga Muscular/fisiologia , Músculo Esquelético , Mialgia/induzido quimicamente , Músculo Quadríceps/fisiologia , Solução Salina Hipertônica , Estimulação Magnética Transcraniana
8.
Med Pr ; 73(2): 95-107, 2022 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-35349556

RESUMO

BACKGROUND: The cabin of the manned submersible is a narrow and sealed space. The long-time work of oceanauts is easy to cause muscle fatigue and stiffness, which reduces efficiency. This paper explored the relative more effective way to relieve leg muscle fatigue of the oceanauts in the manned submersible. MATERIAL AND METHODS: Twenty healthy young people with an average age of 24 years were selected as the participants, while the usual natural relaxation and the stretching method proposed by the surveys were selected as the relieve method for muscle fatigue. This study compared the effects of the 2 recovery ways using the electromyography data from the quadriceps femoris and biceps femoris, and the subjective scales. RESULTS: With the support of data of integral electromyogram (iEMG), root-mean-square (RMS), subjective scales, authors finally found that the 2 muscles of the leg are fatigued significantly, and biceps femoris has more accumulation of fatigue. Although the 2 recovery ways have a significant relief effect on muscle fatigue, the stretching method can reduce more muscle fatigue in a short period of time, especially for biceps femoris. The stretching method is advocated for the oceanauts. CONCLUSIONS: The findings suggested that the stretching method was optimal for relieving the muscle fatigue of the oceanauts during the operation. Med Pr. 2022;73(2):95-107.


Assuntos
Perna (Membro) , Fadiga Muscular , Adolescente , Adulto , Eletromiografia/métodos , Humanos , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia , Músculo Quadríceps/fisiologia , Adulto Jovem
9.
Clinics (Sao Paulo) ; 77: 100011, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35231777

RESUMO

OBJECTIVE: Fatigue of the ankle's stabilizing muscles may influence the performance of functional activities and postural control. The purpose of this study was to evaluate the performance of healthy young adults using functional jump tests and static posturography control under pre- and post-fatigue conditions of the ankle invertor and evertor muscles. METHODS: Thirty physically active healthy male and female (15 male and 15 female) volunteers (24.3 years) were enrolled in this prospective cross-sectional study. Participants performed tests on one day under a non-fatigued state of invertor and evertor muscles and on the second day in a fatigued state. Tests included static posturography on a force platform in a bipedal stance with eyes open and closed and in one-legged support with eyes open and functional jump tests (figure-of-8, side hop, 6-m crossover hop, and square hop). Fatigue of the ankle invertor and evertor muscles was induced using isokinetic dynamometry with 30 repetitions at 120°/s. RESULTS: Participants had an average age of 24.3 years (SD ± 2.08), the height of 1.73 m (SD ± 0.08), and a weight of 68.63 kg (SD ± 10.29). The average Body Mass Index (BMI) was 22.88 (SD ± 2.46). A decrease in performance was observed in functional activities and postural control under all conditions after the induction of muscle fatigue, except for the speed at a bipedal stance with eyes open. CONCLUSIONS: Functional jump tests are low cost and useful for clinical practice and evaluation of the effects of muscle fatigue and could be used in clinical practice.


Assuntos
Fadiga Muscular , Músculo Esquelético , Adulto , Articulação do Tornozelo/fisiologia , Estudos Transversais , Feminino , Humanos , Masculino , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia , Equilíbrio Postural/fisiologia , Estudos Prospectivos , Adulto Jovem
10.
J Appl Physiol (1985) ; 132(4): 1041-1053, 2022 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-35238653

RESUMO

One of the most important cytosolic Ca2+ buffers present in mouse fast-twitch myofibers, but not in human myofibers, is parvalbumin (PV). Previous work using conventional PV gene (PV) knockout (PV-KO) mice suggests that lifelong PV ablation increases fatigue resistance, possibly due to compensations in mitochondrial volume. In this work, PV ablation was induced only in adult mice (PV-KO), and contractile and cytosolic Ca2+ responses during fatigue were studied in isolated muscle and intact single myofibers. Results were compared with control littermates (PV-Ctr). We hypothesized that the reduced myofiber cytosolic Ca2+ buffering developed only in adult PV-KO mice leads to a larger cytosolic free Ca2+ concentration ([Ca2+]c) during repetitive contractions, increasing myofiber fatigue resistance. Extensor digitorum longus (EDL) muscles from PV-KO mice had higher force in unfused stimulations (∼50%, P < 0.05) and slowed relaxation (∼46% higher relaxation time, P < 0.05) versus PV-Ctr, but muscle fatigue resistance or fatigue-induced changes in relaxation were not different between genotypes (P > 0.05). In intact single myofibers from flexor digitorum brevis (FDB) muscles, basal and tetanic [Ca2+]c during fatiguing contractions were higher in PV-KO (P < 0.05), accompanied by a greater slowing in estimated sarcoplasmic reticulum (SR) Ca2+-pumping versus PV-Ctr myofibers (∼84% reduction, P < 0.05), but myofiber fatigue resistance was not different between genotypes (P > 0.05). Our results demonstrate that although the estimated SR Ca2+ uptake was accelerated in PV-KO, the total energy demand by the major energy consumers in myofibers, the cross-bridges, and SR Ca2+ ATPase were not altered enough to affect the energy supply for contractions, and therefore fatigue resistance remained unaffected.NEW & NOTEWORTHY Parvalbumin (PV) is a cytosolic Ca2+ buffer that is present in mouse myofibers but not in human muscle. We show that inducible knockout of PV leads to increases in myofiber cytosolic free Ca2+ concentrations and slowing of Ca2+ pumping during fatigue versus control mice. However, PV ablation does not interfere with fatigue-induced slowing in relaxation or fatigue resistance. These data support the use of mouse muscle as a suitable model to investigate human muscle fatigue.


Assuntos
Cálcio , Fadiga Muscular , Animais , Cálcio/metabolismo , Camundongos , Contração Muscular/fisiologia , Fadiga Muscular/fisiologia , Músculo Esquelético/metabolismo , Parvalbuminas/genética , Parvalbuminas/metabolismo , Retículo Sarcoplasmático/metabolismo , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismo
11.
Sensors (Basel) ; 22(5)2022 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-35271046

RESUMO

The objective detection of muscle fatigue reports the moment at which a muscle fails to sustain the required force. Such a detection prevents any further injury to the muscle following fatigue. However, the objective detection of muscle fatigue still requires further investigation. This paper presents an algorithm that employs a new fatigue index for the objective detection of muscle fatigue using a double-step binary classifier. The proposed algorithm involves analyzing the acquired sEMG signals in both the time and frequency domains in a double-step investigation. The first step involves calculating the value of the integrated EMG (IEMG) to determine the continuous contraction of the muscle being investigated. It was found that the IEMG value continued to increase with prolonged muscle contraction and progressive fatigue. The second step involves differentiating between the high-frequency components (HFC) and low-frequency components (LFC) of the EMG, and calculating the fatigue index. Basically, the segmented EMG signal was filtered by two band-pass filters separately to produce two sub-signals, namely, a high-frequency sub-signal (HFSS) and a low-frequency sub-signal (LFSS). Then, the instantaneous mean amplitude (IMA) was calculated for the two sub-signals. The proposed algorithm indicates that the IMA of the HFSS tends to decrease during muscle fatigue, while the IMA of the LFSS tends to increase. The fatigue index represents the difference between the IMA values of the LFSS and HFSS, respectively. Muscle fatigue was found to be present and was objectively detected when the value of the proposed fatigue index was equal to or greater than zero. The proposed algorithm was tested on 75 EMG signals that were extracted from 75 middle deltoid muscles. The results show that the proposed algorithm had an accuracy of 94.66% in distinguishing between conditions of muscle fatigue and non-fatigue.


Assuntos
Fadiga Muscular , Músculo Esquelético , Algoritmos , Eletromiografia/métodos , Contração Muscular , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia
12.
Med Probl Perform Art ; 37(1): 1-12, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-35234800

RESUMO

BACKGROUND: Repetitive piano play may overload neck and shoulder muscles and tendons, leading to playing-related musculoskeletal disorders (PRMDs). METHODS: In this pilot study (EMG data of the extensor carpi radialis have been published separately), surface electromyography (sEMG) activity of the upper trapezius (UT) was captured in 10 conservatory piano students while playing a fast and a slow music score selected from the individual's repertoire, each 3 minutes long. Measurements were made at baseline and again after 2 hrs and 4 hrs of rehearsal time of the piano études. The amplitude of the sEMG signal was processed by a smoothing algorithm, and the frequency component with a non-orthogonal wavelets procedure. Amplitude of the sEMG was expressed in percent of maximal voluntary contraction (%MVC) at baseline, and the frequency component using median frequency based on the frequency band powers. Statistical analysis encompassed repeated measures ANOVAs for the amplitude and frequency components of the sEMG signal (set at 5%). The students also rated the intensity of rehearsals using a visual analog scale (VAS). RESULTS: The median values for the %MVC presented a global mean for the left trapezius of 5.86 (CI90% 4.71, 6.97) and 5.83 for the right trapezius (CI90% 4.64, 7.05). The rehearsals at moderate intensity increased the amplitude of %MVC of the upper trapezius by around 50% and decreased the median frequency. CONCLUSIONS: Playing faster presented higher magnitudes of activity of the upper trapezius. The decrease in the median frequency in response to long rehearsals may be a sign of muscle fatigue.


Assuntos
Músculos Superficiais do Dorso , Eletromiografia/métodos , Humanos , Contração Muscular/fisiologia , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia , Projetos Piloto , Ombro/fisiologia , Estudantes
13.
Sensors (Basel) ; 22(6)2022 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-35336519

RESUMO

The purpose of this study was to determine the effect of fatigue on impact shock wave attenuation and assess how human biomechanics relate to shock attenuation during running. In this paper, we propose a new methodology for the analysis of shock events occurring during the proposed experimental procedure. Our approach is based on the Shock Response Spectrum (SRS), which is a frequency-based function that is used to indicate the magnitude of vibration due to a shock or a transient event. Five high level CrossFit athletes who ran at least three times per week and who were free from musculoskeletal injury volunteered to take part in this study. Two Micromachined Microelectromechanical Systems (MEMS) accelerometers (RunScribe®, San Francisco, CA, USA) were used for this experiment. The two RunScribe pods were mounted on top of the foot in the shoelaces. All five athletes performed three maximum intensity runs: the 1st run was performed after a brief warmup with no prior exercise, then the 2nd and the 3rd run were performed in a fatigued state. Prior to the 2nd and the 3rd run, the athletes were asked to perform at maximum intensity for two minutes on an Assault AirBike to tire them. For all five athletes, there was a direct correlation between fatigue and an increase in the aggressiveness of the SRS. We noticed that for all five athletes for the 3rd run the average SRS peaks were significantly higher than for the 1st run and 2nd run (p < 0.01) at the same natural frequency of the athlete. This confirms our hypothesis that fatigue causes a decrease in the shock attenuation capacity of the musculoskeletal system thus potentially involving a higher risk of overuse injury.


Assuntos
Corrida , Fenômenos Biomecânicos , Fadiga , Humanos , Fadiga Muscular/fisiologia , Corrida/fisiologia , Análise Espectral
14.
Exp Physiol ; 107(4): 312-325, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-35137992

RESUMO

NEW FINDINGS: What is the central question of this study? Does the work done above critical power (W') or muscle activation determine the degree of peripheral fatigue induced by cycling time trials performed in the severe-intensity domain? What is the main finding and its importance? Peripheral fatigue increased when power output and muscle activation increased, whereas W' did not change between the time trials. Therefore, no relationship was found between W' and exercise-induced peripheral fatigue such as previously postulated in the literature. In contrast, we found a significant association between EMG amplitude during exercise and exercise-induced reduction in the potentiated quadriceps twitch, suggesting that muscle activation plays a key role in determining peripheral fatigue during severe-intensity exercise. ABSTRACT: In order to determine the relationship between peripheral fatigue, muscle activation and the total work done above critical power (W'), 10 men and four women performed, on separated days, self-paced cycling time trials of 3, 6, 10 and 15 min. Exercise-induced quadriceps fatigue was quantified using pre- to postexercise (15 s to 15 min recovery) changes in maximal voluntary contraction (MVC) peak force, voluntary activation and potentiated twitch force (QT). Voluntary activation was measured using the interpolated twitch technique, and QT was evoked by electrical stimulations of the femoral nerve. Quadriceps muscle activation was determined using the root mean square of surface EMG of vastus lateralis (VLRMS ), vastus medialis (VMRMS ) and rectus femoris (RFRMS ). Critical power and W' were calculated from the power-duration relationship from the four time trials. Mean power output and mean VLRMS , VMRMS and RFRMS were greater during shorter compared with longer exercise periods (P < 0.05), whereas no significant between-trial change in W' was found. The magnitude of exercise-induced reductions in QT increased with the increase in power output (P < 0.001) and was associated with mean VLRMS, VMRMS and RFRMS (P < 0.001, r2  > 0.369) but not W' (P > 0.150, r2  < 0.044). Reduction in voluntary activation tended (P = 0.067) to be more pronounced with the lengthening in time trial duration, whereas no significant between-trial changes in MVC peak force were found. Our data suggest that peripheral fatigue is not related to the amount of work done above the critical power but rather to the level of muscle activation during exercise in the severe-intensity domain.


Assuntos
Exercício Físico , Fadiga Muscular , Eletromiografia , Exercício Físico/fisiologia , Tolerância ao Exercício/fisiologia , Feminino , Humanos , Masculino , Contração Muscular/fisiologia , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia , Músculo Quadríceps/fisiologia
15.
Biomed Res Int ; 2022: 6450844, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35187168

RESUMO

AIMS: Type 2 diabetes (T2D) is associated with sarcopenia and decreased muscle strength. Explosive and isometric voluntary handgrip strengths (EHGS and HGS) are frequently utilized methods to ascertain health status and a marker of overall muscle strength. We have previously shown that a portable, motorized device, which produces effortless, rapid stepping in place (passive simulated jogging device (JD)), improves glucose homeostasis. This study quantitatively evaluated the effects of JD in modifying parameters of the modified EHGS curve in T2D and nondiabetic (ND) subjects. METHODS: Twenty-one adult participants (11 ND and 10 T2D) (mean age: 41.3 ± 13.5 yr) performed a modified explosive handgrip strength (EHGS) test on study day 1 followed by daily use of JD (90 min per day) for 7 days. The EHGS was repeated after 3 and 7 days' use of JD (JD3 and JD7) and 3 days after completion of JD (Carryover). EHGS curves were analyzed for the following: maximal peak force value (MAX); rate of force development at 25%,75%, and 90% of maximum force; and maximum force (RFD25%, RFD75%, RFD90%, and RFDmax); time to 90%, 75%, and 25% of maximal force (t 90, t 75, t 25) and time to maximal force (t max); and the integrated area under the curve for force vs. time until task failure (iAUCTF); and fatigue resistance times at 50% and 25% of maximal force (FR50 and FR25) and fatigue resistance time to task failure (FRTF). RESULTS: At baseline, T2D had lower MAX compared to ND. There were no differences at baseline for force development time or fatigue resistance time between T2D and ND. In both T2D and ND, 7 days of JD increased FR25 and FRTF and iAUCTF compared to baseline. CONCLUSION: JD for at least 7 days prior to EHGS increased time to task failure (fatigue resistance) and iAUCTF of the force-time curve. JD is a reasonable intervention to decrease sedentary behavior and improve muscle fatigue resistance under various clinical and nonclinical scenarios. This trial is registered with NCT03550105 (08-06-2018).


Assuntos
Diabetes Mellitus Tipo 2/fisiopatologia , Força da Mão/fisiologia , Corrida Moderada , Fadiga Muscular/fisiologia , Adulto , Feminino , Humanos , Masculino
16.
Eur J Appl Physiol ; 122(5): 1189-1204, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35212845

RESUMO

PURPOSE: Repeated sprint ability is an integral component of team sports. This study aimed to evaluate fatigability development and its aetiology during and immediately after a cycle repeated sprint exercise performed until a given fatigability threshold. METHODS: On an innovative cycle ergometer, 16 healthy males completed an RSE (10-s sprint/28-s recovery) until task failure (TF): a 30% decrease in sprint mean power (Pmean). Isometric maximum voluntary contraction of the quadriceps (IMVC), central alterations [voluntary activation (VA)], and peripheral alterations [twitch (Pt)] were evaluated before (pre), immediately after each sprint (post), at TF and 3 min after. Sprints were expressed as a percentage of the total number of sprints to TF (TSTF). Individual data were extrapolated at 20, 40, 60, and 80% TSTF. RESULTS: Participants completed 9.7 ± 4.2 sprints before reaching a 30% decrease in Pmean. Post-sprint IMVCs were decreased from pre to 60% TSTF and then plateaued (pre: 345 ± 56 N, 60% 247 ± 55 N, TF: 233 ± 57 N, p < 0.001). Pt decreased from 20% and plateaued after 40% TSTF (p < 0.001, pre-TF = - 45 ± 13%). VA was not significantly affected by repeated sprints until 60% TSTF (pre-TF = - 6.5 ± 8.2%, p = 0.036). Unlike peripheral parameters, VA recovered within 3 min (p = 0.042). CONCLUSION: During an RSE, Pmean and IMVC decreases were first concomitant to peripheral alterations up to 40% TSTF and central alterations was only observed in the second part of the test, while peripheral alterations plateaued. The distinct recovery kinetics in central versus peripheral components of fatigability further confirm the necessity to reduce traditional delays in neuromuscular fatigue assessment post-exercise.


Assuntos
Ergometria , Fadiga Muscular , Eletromiografia , Exercício Físico/fisiologia , Humanos , Contração Isométrica , Masculino , Fadiga Muscular/fisiologia
18.
Exp Gerontol ; 161: 111732, 2022 05.
Artigo em Inglês | MEDLINE | ID: mdl-35139406

RESUMO

The present study aimed to investigate age-related differences in fatigability induced by an isometric quadriceps intermittent fatiguing test in 30 young (<35 years old, 15 females), 19 old (>60 years old, 9 females) and 30 very old (>80 years old, 15 females) adults. Maximal force loss, contractile function and voluntary activation of the knee extensors were evaluated throughout an isometric fatiguing test using femoral nerve magnetic stimulations. Older adults performed more contractions (index of relative performance) than young (P = 0.046) and very old adults (P = 0.007), without differences between young and very old adults (P = 1.000). Force-time integral (absolute performance) was greater for young and old adults compared to very old adults (P < 0.001), without differences between young and old adults (P = 0.124). At exhaustion, force loss was greater for young (-28 ± 9%) compared to old adults (-19 ± 8%; P = 0.002), but not very old adults (-23 ± 8%; P = 0.106), and no difference between old and very old adults (P = 0.414). Data from the interpolated twitch technique suggested similar alteration in contractile function with age, with no impairments in voluntary activation. Impairments were similar across sexes. This study showed that older adults were less fatigable than young adults during an isometric intermittent fatiguing task of the knee extensors. This greater fatigue resistance was not maintained in very old adults independent of sex. Fatigability at exhaustion was likely due to impairments in contractile function for the three age groups.


Assuntos
Contração Isométrica , Fadiga Muscular , Idoso , Idoso de 80 Anos ou mais , Eletromiografia/métodos , Feminino , Humanos , Contração Isométrica/fisiologia , Joelho/fisiologia , Contração Muscular/fisiologia , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia
19.
J Biomech ; 133: 110890, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-35121381

RESUMO

This study aimed to investigate if the impairing in postural control, induced by ankle fatiguing exercise, remains after 24/48 h in young adults. Center of Pressure (CoP) was assessed in 16 participants (23 ± 3 years old) before, immediately after an ankle fatigability induction protocol (FI) and after 24 or 48 h of recovery using two 60-s trials with eyes open (EO) and closed (EC). The FI consisted of performing the ankle plantar flexion and dorsiflexion movement repeatedly (0.5 Hz). Ankle muscle fatigability increased CoP anterior-posterior (AP - p < 0.02) and medial-lateral (ML - p < 0.009) root mean square (RMS), and AP (p < 0.01) mean velocity immediately after compared to before FI. These effects remained after 24/48 h of recovery: higher CoP AP (p < 0.03) and ML (p < 0.009) RMS. No significant effects for detrend fluctuation analysis and entropy analysis among periods of postural evaluations was found. Fatigue*visual condition interaction revealed an increased AP median frequency (p < 0.001) during EC compared to EO only immediately after FI. Young adults' body sway remains impaired until 48 h, but not the postural control adaptability and complexity. Visual information may not attenuate the late deleterious ankle muscle fatigability effects. Individuals should be cautious during balance tasks and exercise after fatiguing exercise in the next 24/48 h, therefore avoiding unbalances and falls.


Assuntos
Articulação do Tornozelo , Tornozelo , Adulto , Articulação do Tornozelo/fisiologia , Humanos , Fadiga Muscular/fisiologia , Músculos , Equilíbrio Postural/fisiologia , Adulto Jovem
20.
Gait Posture ; 93: 7-13, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-35042058

RESUMO

BACKGROUND: Muscle fatigue of the lower limbs is considered a main contributor to the perceived fatigue in children with cerebral palsy (CP) and is expected to occur during prolonged walking. In adults without disabilities, muscle fatigue has been proposed to be associated with adaptations in complexity of neuromuscular control. RESEARCH QUESTION: What are the effects of prolonged walking on signs of muscle fatigue and complexity of neuromuscular control in children with CP? METHODS: Ten children with CP and fifteen typically developing (TD) children performed a standardised protocol on an instrumented treadmill consisting of three stages: six-minutes walking at preferred speed (6 MW), moderate-intensity walking (MIW, with two minutes at heart rate > 70% of predicted maximal heart rate) and four-minutes walking at preferred speed (post-MIW). Electromyography (EMG) data were analysed for eight muscles of one leg during three time periods: 6 MW-start, 6 MW-end and post-MIW. Signs of muscle fatigue were quantified as changes in EMG median frequency and EMG root mean square (RMS). Complexity of neuromuscular control was quantified by total variance accounted for by one synergy (tVAF1). Muscle coactivation was assessed for antagonistic muscle pairs. RESULTS: EMG median frequency was decreased at 6 MW-end and post-MIW compared to 6 MW-start in children with CP (p < 0.05), but not in TD children. In both groups, EMG-RMS (p < 0.01) and muscle coactivation (p < 0.01) were decreased at 6 MW-end and post-MIW compared to 6 MW-start. tVAF1 decreased slightly at 6 MW-end and post-MIW compared to 6 MW-start in both groups (p < 0.05). Changes were most pronounced from 6 MW-start to 6 MW-end. SIGNIFICANCE: Children with CP presented signs of muscle fatigue after prolonged walking, while no effects were found for TD. Both groups showed minimal changes in tVAF1, suggesting signs of muscle fatigue are not associated with changes in complexity of neuromuscular control.


Assuntos
Paralisia Cerebral , Fadiga Muscular , Adulto , Paralisia Cerebral/complicações , Criança , Eletromiografia/métodos , Marcha/fisiologia , Humanos , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia , Caminhada/fisiologia
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