Effect of muscular fatigue on the cumulative lumbar damage during repetitive lifting task: a comparative study of damage calculation methods.

Several methods have been put forward to quantify cumulative loads; however, limited evidence exists as to the subsequent damages and the role of muscular fatigue. The present study assessed whether muscular fatigue could affect cumulative damage imposed on the L5-S1 joint. Trunk muscle electromyographic (EMG) activities and kinematics/kinetics of 18 healthy male individuals were evaluated during a simulated repetitive lifting task. A traditional EMG-assisted model of the lumbar spine was modified to account for the effect of erector spinae fatigue. L5-S1 compressive loads for each lifting cycle were estimated based on varying (i.e. actual), fatigue-modified, and constant Gain factors. The corresponding damages were integrated to calculate the cumulative damage. Moreover, the damage calculated for one lifting cycle was multiplied by the lifting frequency, as the traditional approach. Compressive loads and the damages obtained through the fatigue-modified model were predicted in close agreement with the actual values. Similarly, the difference between actual damages and those driven by the traditional approach was not statistically significant (p = 0.219). However, damages based on a constant Gain factor were significantly greater than those based on the actual (p = 0.012), fatigue-modified (p = 0.017), and traditional (p = 0.007) approaches.Practitioner summary: In this study, we managed to include the effect of muscular fatigue on cumulative lumbar damage calculations. Including the effect of muscular fatigue leads to an accurate estimation of cumulative damages while eliminating computational complexity. However, using the traditional approach also appears to provide acceptable estimates for ergonomic assessments.

The Effect of Mental and Muscular Fatigue on the Accuracy and Kinematics of Dart Throwing.

In this study, we analyzed the effect of mental and muscular fatigue on the accuracy and kinematics of dart throwing. For this purpose, 28 young adults (19 females and 9 males) aged 25-35 years, without any regular experience in dart throwing, participated in this study. We evaluated their dart throwing skills in mental fatigue, muscular fatigue, and non-fatigue conditions. To induce mental fatigue, we used the Stroop task for 70 minutes and a simulated dart throwing exercise with an elastic band. In all three conditions, we collected accuracy data, based on the score of the dart on the board and the kinematic properties with a motion capture device. For analyzing the data and testing the research hypotheses, we employed ANOVA analyses with repeated measures after examining the normality of data distributions using skewness and kurtosis. We observed a significant decrease in the accuracy of dart throwing following mental fatigue (p = 0.027) and muscular fatigue (p = 0.001) compared to non-fatigue and following muscular fatigue compared to mental fatigue (p = 0.001). In the kinematic results, we observed a significant difference in the mean velocity of the elbow between different experimental conditions (p = 0.001). This variable decreased due to muscular fatigue, compared to the other two conditions. On the other hand, there was no significant difference among the three experimental conditions for the variables of elbow range of motion, shoulder range of motion, and mean velocity of the shoulder joint. These findings affirm mental and muscular fatigue effects on dart throwing and provide further detail regarding the specific aspects of these effects on dart throwing skills or other fine motor activities.

Can Data-Driven Supervised Machine Learning Approaches Applied to Infrared Thermal Imaging Data Estimate Muscular Activity and Fatigue?

Surface electromyography (sEMG) is the acquisition, from the skin, of the electrical signal produced by muscle activation. Usually, sEMG is measured through electrodes with electrolytic gel, which often causes skin irritation. Capacitive contactless electrodes have been developed to overcome this limitation. However, contactless EMG devices are still sensitive to motion artifacts and often not comfortable for long monitoring. In this study, a non-invasive contactless method to estimate parameters indicative of muscular activity and fatigue, as they are assessed by EMG, through infrared thermal imaging (IRI) and cross-validated machine learning (ML) approaches is described. Particularly, 10 healthy participants underwent five series of bodyweight squats until exhaustion interspersed by 1 min of rest. During exercising, the vastus medialis activity and its temperature were measured through sEMG and IRI, respectively. The EMG average rectified value (ARV) and the median frequency of the power spectral density (MDF) of each series were estimated through several ML approaches applied to IRI features, obtaining good estimation performances (r = 0.886, p < 0.001 for ARV, and r = 0.661, p < 0.001 for MDF). Although EMG and IRI measure physiological processes of a different nature and are not interchangeable, these results suggest a potential link between skin temperature and muscle activity and fatigue, fostering the employment of contactless methods to deliver metrics of muscular activity in a non-invasive and comfortable manner in sports and clinical applications.

Projection of fatigue and neuromuscular changes caused by different excises / Projeção da fadiga e as alterações neuromusculares provocadas em distintas atividades físicas / Proyección de la fatiga y los cambios neuromusculares provocados en diferentes actividades físicas

ABSTRACT Introduction: Athletes' muscles can be weakened by fatigue caused by excessive activity. This limitation compromises their functional capacity and professional performance. The competition's performance correlates positively with muscular quality of function. The changes analysis caused by different athletic activities in muscle contraction by noninvasive tensiomyography reflects the functional state of the muscles. Still, no experiments are adapted to verify the fatigue risk level. Objective: Verify the possible relationship between exercise and neuromuscular fatigue using noninvasive tensiomyography. Methods: 90 athletes were randomly selected in weightlifting, badminton, and athletics sports. Maximum radial displacement, contraction, delay, duration, and relaxation time indices were collected. Muscle fatigue detection was based on the empirical mode decomposition modeling method with the Rogers sensitivity fluctuation rate. All values were collected in the rectus femoris muscle before and after the exercises. They were statistically treated and compared (P<0.05). Results: All athletes showed a decline in maximum radial displacement values after exercise. It reveals that their muscles are in a considerable state of tension, especially in the track and field group (from 8.57±3.42mm to 5.43±2.14mm). However, the slightest change in delay time was observed in the weightlifting group (16.21±4.15ms initial versus 18.34±3.27ms final). Conclusion: Through tensiomyography technology, it is possible to obtain a relationship between exercise and neuromuscular fatigue, analyzing the physical activity effects in a noninvasive way. Evidence Level II; Therapeutic Studies - Investigating the result.

RESUMO Introdução: A musculatura do atleta pode ser debilitada com a fadiga ocasionada pelo excesso de atividade. Essa limitação compromete sua capacidade funcional e desempenho profissional. O desempenho nas competições correlaciona-se positivamente com a qualidade da função muscular. A análise das alterações provocadas por distintas atividades atléticas na contração muscular pela tensiomiografia não invasiva reflete o estado funcional dos músculos, porém não há experimentos adaptados para verificar o grau de risco de fadiga. Objetivo: Verificar a possível relação entre exercício e fadiga neuromuscular utilizando tensiomiografia não invasiva. Métodos: 90 atletas foram selecionados aleatoriamente nos esportes de halterofilismo, badminton e atletismo. Foram coletados os índices de deslocamento radial máximo, tempo de contração, tempo de atraso, duração e tempo de relaxamento. A detecção de fadiga muscular foi baseada no método de modelagem da decomposição do modo empírico com o conceito de taxa de flutuação de sensibilidade de Rogers. Os valores dos três grupos foram coletados no músculo reto femoral antes e depois dos exercícios. Foram tratados estatisticamente e comparados(P<0,05). Resultados: Todos os grupos de atletas apresentaram um declínio nos valores de deslocamento radial máximo após o exercício. Isso revela que seus músculos estão em grande estado de tensão, especialmente no grupo de atletismo (de 8.57±3.42mm para 5.43±2.14mm). A menor alteração no tempo de atraso, porém, foi observada no grupo de halterofilismo (16.21±4.15ms iniciais contra 18.34±3.27ms finais). Conclusão: Através da tecnologia de tensiomiografia foi possível obter a relação entre exercício e fadiga neuromuscular analisando os efeitos da atividade física de forma não invasiva. Nível de evidência II; Estudos Terapêuticos - Investigação de Resultados.

RESUMEN Introducción: La musculatura del deportista puede estar debilitada por la fatiga causada por una actividad excesiva. Esta limitación compromete su capacidad funcional y su rendimiento profesional. El rendimiento en las competiciones se correlaciona positivamente con la calidad de la función muscular. El análisis de los cambios provocados por las diferentes actividades deportivas en la contracción muscular mediante la tensiomiografía no invasiva refleja el estado funcional de los músculos, pero no existen experimentos adaptados para verificar el grado de riesgo de fatiga. Objetivo: Verificar la posible relación entre el ejercicio y la fatiga neuromuscular mediante una tensiomografía no invasiva. Métodos: Se seleccionaron al azar 90 atletas de los deportes de halterofilia, bádminton y atletismo. Se recogieron los índices de desplazamiento radial máximo, tiempo de contracción, tiempo de retardo, duración y tiempo de relajación. La detección de la fatiga muscular se basó en el método de modelado de descomposición modal empírica con el concepto de tasa de fluctuación de la sensibilidad propuesto por Rogers. Se recogieron los valores de los tres grupos en el músculo recto femoral antes y después de los ejercicios. Se trataron y compararon estadísticamente (P<0,05). Resultados: Todos los grupos de atletas mostraron un descenso en los valores del desplazamiento radial máximo después del ejercicio. Esto revela que sus músculos están en un gran estado de tensión, especialmente en el grupo de atletismo (de 8,57±3,42mm a 5,43±2,14mm). Sin embargo, el menor cambio en el tiempo de retraso se observó en el grupo de levantamiento de pesas (16,21±4,15ms iniciales frente a 18,34±3,27ms finales). Conclusión: A través de la tecnología de la tensiomografía fue posible obtener la relación entre el ejercicio y la fatiga neuromuscular analizando los efectos de la actividad física de forma no invasiva. Nivel de evidencia II; Estudios terapéuticos - Investigación de resultados.

Effects of Physical and Mental Fatigue on Postural Sway and Cortical Activity in Healthy Young Adults.

Physical fatigue (PF) negatively affects postural control, resulting in impaired balance performance in young and older adults. Similar effects on postural control can be observed for mental fatigue (MF) mainly in older adults. Controversial results exist for young adults. There is a void in the literature on the effects of fatigue on balance and cortical activity. Therefore, this study aimed to examine the acute effects of PF and MF on postural sway and cortical activity. Fifteen healthy young adults aged 28 ± 3 years participated in this study. MF and PF protocols comprising of an all-out repeated sit-to-stand task and a computer-based attention network test, respectively, were applied in random order. Pre and post fatigue, cortical activity and postural sway (i.e., center of pressure displacements [CoPd], velocity [CoPv], and CoP variability [CV CoPd, CV CoPv]) were tested during a challenging bipedal balance board task. Absolute spectral power was calculated for theta (4-7.5 Hz), alpha-2 (10.5-12.5 Hz), beta-1 (13-18 Hz), and beta-2 (18.5-25 Hz) in frontal, central, and parietal regions of interest (ROI) and baseline-normalized. Inference statistics revealed a significant time-by-fatigue interaction for CoPd (p = 0.009, d = 0.39, Δ 9.2%) and CoPv (p = 0.009, d = 0.36, Δ 9.2%), and a significant main effect of time for CoP variability (CV CoPd: p = 0.001, d = 0.84; CV CoPv: p = 0.05, d = 0.62). Post hoc analyses showed a significant increase in CoPd (p = 0.002, d = 1.03) and CoPv (p = 0.003, d = 1.03) following PF but not MF. For cortical activity, a significant time-by-fatigue interaction was found for relative alpha-2 power in parietal (p < 0.001, d = 0.06) areas. Post hoc tests indicated larger alpha-2 power increases after PF (p < 0.001, d = 1.69, Δ 3.9%) compared to MF (p = 0.001, d = 1.03, Δ 2.5%). In addition, changes in parietal alpha-2 power and measures of postural sway did not correlate significantly, irrespective of the applied fatigue protocol. No significant changes were found for the other frequency bands, irrespective of the fatigue protocol and ROI under investigation. Thus, the applied PF protocol resulted in increased postural sway (CoPd and CoPv) and CoP variability accompanied by enhanced alpha-2 power in the parietal ROI while MF led to increased CoP variability and alpha-2 power in our sample of young adults. Potential underlying cortical mechanisms responsible for the greater increase in parietal alpha-2 power after PF were discussed but could not be clearly identified as cause. Therefore, further future research is needed to decipher alternative interpretations.

Repeated Simulated Match-Induced Changes in Finger Flexor Force and Blood Acid-Base Balance in World-Class Female Judokas.

PURPOSE: The aim of this study was to investigate the time course of maximal isometric finger flexor force and blood acid-base balance during repeated simulated matches in world-class judokas. METHODS: Seven 21- to 28-year-old world-class female judokas (including Olympic and World Championship medalists) repeated four 4-minute judo combats interspersed by 15 minutes of passive recovery. Maximal voluntary isometric finger flexor contraction (MVIC) force was measured in both hands after warm-up and immediately after each combat using a handgrip dynamometer. MVIC force was classified as MVIC hikite force (pulling hand) and MVIC tsurite force (lifting hand). RESULTS: Blood lactate concentration, pH, bicarbonate concentration, partial pressure of oxygen, and oxygen saturation were measured between 3 and 5 minutes after each match. At completion of the fourth combat, mean MVIC hikite and tsurite force decreased by 18% and 12%, respectively (g = 0.23 and 0.29, respectively; P < .05), demonstrating that force production was substantial throughout repeated matches. Blood lactate concentration increased ∼5-fold from 2.69 (1.37) mmol·L-1 after warm-up to 13.10 (2.61) mmol·L-1 after the last match (g = 4.13, P = .018). Concurrently, blood pH decreased slightly from 7.44 (0.03) to 7.26 (0.05) (g = 2.34, P = .018), that is, by only 0.18 units. The decreased blood pH was significantly correlated with a decrease in bicarbonate concentration (R2 = .94, P < .001). Finally, partial pressure of oxygen and oxygen saturation remained unchanged during the judo contest. CONCLUSIONS: Female world-class judokas were able to maintain a high level of grip strength in both hands and efficiently regulate blood acid-base balance during repeated simulated high-intensity matches.

Cognitive tasks elicit mental fatigue and impair subsequent physical task endurance: Effects of task duration and type.

Although mentally fatiguing cognitive tasks can impair subsequent physical endurance, the importance of cognitive task duration and the role of response inhibition remain unclear. This study compared the effects of a serial incongruent Stroop color-classification task (i.e., with response inhibition) and N-back memory updating task (i.e., without response inhibition) on mental fatigue and subsequent rhythmic handgrip exercise. Participants (N = 90) were randomly assigned to one of three cognitive task groups (Stroop, 2-back, control) and completed four 10-min blocks of one cognitive task followed by a 5-min physical endurance task (self-paced rhythmic handgrip exercise). Heart rate, heart rate variability, electromyographic forearm activity, and force were recorded throughout along with self-reported measures of fatigue, exertion, and motivation. From the start, the Stroop and 2-back tasks elicited higher heart rate and lower heart rate variability as well as greater fatigue, effort, and interest/enjoyment than the control task. From the second block onwards, the Stroop and 2-back groups produced less force than the control group. There were no group differences in forearm muscle activity. In sum, mental fatigue was induced after performing a cognitive task for 10 mins, whereas muscular endurance was impaired after performing a cognitive task for 20 mins. That these effects were observed for both types of cognitive task indicates that response inhibition is not a necessary condition. The cognitive task duration required to induce mental fatigue and impair rhythmic handgrip endurance performance lay between the durations reported previously for isometric (a few minutes) and whole-body (half an hour) endurance exercise.

Clinical application of gene medicine in preventing sports injuries / Aplicação clínica da medicina genética na prevenção de lesões esportivas / Aplicación clínica de la medicina genética en la prevención de lesiones deportivas

ABSTRACT Introduction: Using gene therapy to transfer specific genes to implant therapeutic proteins into damaged tissues is a more promising way to treat sports injuries. The combination of tissue engineering and gene therapy will potentially promote the regeneration and repair of various damaged tissues. Objective: This article explores the adaptive relationship between gene selection therapy and athletes in sports. Methods: We selected students of related majors in sports schools to conduct specific genetic testing and measure the muscle area, fatigue level, muscle damage, and other related indicators before and after exercise. Results: After a series of physical fitness assessments, an increase in the gene sequence, as well as changes in the biochemical indices, were confirmed Conclusions: The muscle gain of the test subject during training is better than other genotypes. Level of evidence II; Therapeutic studies - investigation of treatment results.

RESUMO Introdução: A terapia gênica para transferir genes específicos para codificar proteínas terapêuticas para tecidos danificados é uma forma bastante promissora de tratar lesões esportivas. A combinação de engenharia de tecidos e terapia gênica possivelmente promoverá regeneração e reparo de vários tecidos danificados. Objetivo: Este artigo explora a relação adaptativa entre a terapia de seleção gênica e atletas no esporte. Métodos: Selecionamos alunos universitários nas escolas de esportes para realizar testes genéticos específicos e medir a área muscular, nível de fadiga, lesões musculares e outros indicadores relacionados antes e depois do exercício. Resultados: Depois de uma série de avaliações da aptidão física, verificou-se aumento da sequência gênica, assim como índices bioquímicos também apresentaram alterações. Conclusões: O ganho muscular dos indivíduos testados durante o treinamento é melhor do que outros genótipos. Nível de Evidência II; Estudos terapêuticos - Investigação dos resultados do tratamento.

RESUMEN Introducción: La terapia génica para transferir genes específicos que codifiquen proteínas terapéuticas a los tejidos dañados es una forma muy prometedora de tratar las lesiones deportivas. La combinación de ingeniería tisular y terapia génica posiblemente favorecerá la regeneración y reparación de diversos tejidos dañados. Objetivo: Este artículo explora la relación adaptativa entre la terapia de selección génica y los atletas en el deporte. Métodos: Se seleccionaron estudiantes universitarios de escuelas deportivas para realizar pruebas genéticas específicas y medir el área muscular, el nivel de fatiga, las lesiones musculares y otros indicadores relacionados antes y después del ejercicio. Resultados: Tras una serie de evaluaciones de acondicionamiento físico, se comprobó un aumento de la secuencia génica, y los índices bioquímicos también presentaron cambios. Conclusiones: El aumento de la masa muscular de los individuos analizados durante el entrenamiento es mejor que el de otros genotipos. Nivel de Evidencia II; Estudios terapéuticos - Investigación de los resultados del tratamiento.

Traces of muscular fatigue in the rectus femoris identified with surface electromyography and wavelets on normal gait.

Background: Although the median frequency is used as a basis to assess the presence of muscular fatigue, some studies have found that it is not a good estimator for this purpose. Physiotherapists often deal with patients with movement issues related to fatigue. A new objective estimator that is easy to obtain and interpret can help with the management of such patients.Objective and Purpose: The aim of this study was to identify the frequency bands most affected by fatigue and propose a protocol to obtain such information.Methods: Thirty healthy subjects (age 22.05 ± 2.42 years, height 1.71 ± 0.08 m, and weight 68.75 ± 11.42 kg) were recruited to measure the rectus femoris electromyography (EMG) of both legs during gait, before and after a fatiguing protocol. Four frequency bands were studied: high frequency (107-250 Hz), midfrequency (65-94 Hz), 40 Hz (34-53 Hz), and low frequency (< 25 Hz). Each frequency band is related to different aspects of the muscular contraction.Results: The main finding is that the ratios of the 40-Hz frequency and low-frequency bands showed significant differences in both legs between pre-fatigue and post-fatigue recordings. Critical thresholds F* 4.86 and 4.93 were exceeded at 4.5-8.7%, 30.64-46%.38, 63.75-66.8%, and 83.69-90.79% and at 0-2.53%, 4.7-15.21%, 18.15-54.65%, and 55.81-99.95% of the gait cycle, respectively, with p values < .05.Conclusions: The low-frequency band constitutes the best indicator to assess fatigue in gait.

Central and Peripheral Fatigue in Recreational Trail Runners: A Pilot Study.

BACKGROUND: Understanding fatigue mechanisms is crucial for exercise performance. However, scientific evidence on non-invasive methods for assessing fatigue in trail running competitions is scarce, especially when vertical kilometer trail running races (VK) are considered. The main purpose of this study was to assess the autonomic nervous system (ANS) activity (i.e., central fatigue) and the state of muscle activation (i.e., peripheral fatigue) before and after a VK competition. METHODS: A cross-sectional pilot study was performed. After applying inclusion/exclusion criteria, 8 recreational male trail runners (31.63 ± 7.21 yrs, 1.75 m ± 0.05 m, 70.38 ± 5.41 kg, BMI: 22.88 ± 0.48, running experience: 8.0 ± 3.63 yrs, weekly training volume: 58.75 ± 10.35 km) volunteered to participate and were assessed for both central (i.e., via heart rate variability, HRV) and peripheral (via tensiomyography, TMG) fatigue before and after a VK race. RESULTS: After the VK, resting heart rate, RMSSD (p = 0.01 for both) and SDNN significantly decreased (p = 0.02), while the stress score and the sympathetic-parasympathetic ratio increased (p = 0.01 and p = 0.02, respectively). The TMG analyses suggest that runners already suffered peripheral fatigue before the VK and that 20-30 min are enough for muscular recovery after the race. In summary, our data suggest that participants experienced a pre-competition fatigue status. Further longitudinal studies are necessary to investigate the mechanisms underlying fatigue during trail running races, while training periodization and tapering strategies could play a key role for minimizing pre-competition fatigue status.

Cardiovascular, Metabolic and Perceptual Responses to Preferred Walking Speed at Different Inclines and Post Exercise Postural Control in Healthy College Age Adults.

Although several studies investigated heart rate (HR) and metabolic responses to preferred walking speed (PWS), there is a limited amount of data on PWS responses during varying inclines. Further, there is no data pertaining to the impact of PWS at various inclines on postural control. The purpose of the study was to measure cardiovascular, metabolic, perceptual, and postural impacts of walking at PWS at various inclines. Twenty-one participants completed two lab sessions, seven days apart. On day one, PWS on the treadmill and maximal oxygen consumption (V̇O2max) were established for each participant. On day two, using a counter balanced design, participants completed three, 15-minute walking sessions at their PWS at 0, 4, and 8% inclines. During the sessions, HR, V̇O2, rating of perceived exertion (RPE), V̇O2 reserve (V̇O2R) and HR reserve (HRR) were measured and recorded. Center of Pressure (COP) motion was recorded while standing upon a force plate immediately following each walking bout with eyes closed (EC) and eyes open (EO). The results of the study demonstrated a significant difference (p < .05) in the independent variables across the different inclines excluding HR, RPE and HRR at 4% incline. While there were no significant differences in sway amplitude between the different walking bouts, there was a significant increase in sway with EC compared to EO vision condition (p < .05). Still, Approximate Entropy values decreased (increased regularity) from baseline measures (p < .05). These findings suggest that PWS at different inclines impact measures of exertion and signal regularity but not sway amplitude or velocity.

The Effect of Lower-Body Blood Flow Restriction on Static and Perturbated Stable Stand in Young, Healthy Adults.

Muscular fatigue can affect postural control processes by impacting on the neuromuscular and somatosensory system. It is assumed that this leads to an increased risk of injury, especially in sports such as alpine skiing that expose the body to strong and rapidly changing external forces. In this context, posture constraints and contraction-related muscular pressure may lead to muscular deoxygenation. This study investigates whether these constraints and pressure affect static and dynamic postural control. To simulate impaired blood flow in sports within a laboratory task, oxygen saturation was manipulated locally by using an inflatable cuff to induce blood flow restriction (BFR). Twenty-three subjects were asked to stand on a perturbatable platform used to assess postural-related movements. Using a 2 × 2 within-subject design, each participant performed postural control tasks both with and without BFR. BFR resulted in lower oxygenation of the m. quadriceps femoris (p = 0.024) and was associated with a significantly lower time to exhaustion (TTE) compared to the non-restricted condition [F (1,19) = 16.22, p < 0.001, η p 2 = 0.46]. Perturbation resulted in a significantly increased TTE [F (1,19) = 7.28, p = 0.014, η p 2 = 0.277]. There were no significant effects on static and dynamic postural control within the saturation conditions. The present data indicate that BFR conditions leads to deoxygenation and a reduced TTE. Postural control and the ability to regain stability after perturbation were not affected within this investigation.

Effects of handle height and load on the endurance time for simulated demolition tasks.

BACKGROUND: Manual demolition tasks are heavy physical demanding tasks which involve forceful exertion of sustained pushing. They result in muscle fatigue which could lead to musculoskeletal disorders. Assessments of maximum endurance time (MET) are essential in understanding the developing of muscle fatigue for these tasks. OBJECTIVE: The objectives of this study were to determine the effects of handle height and load conditions on the MET, and to establish MET models for the simulated demolition tasks. METHODS: Twenty three male participants performed simulated demolition tasks under three loads and three handle heights conditions until they could not do so any longer. Their METs and ratings of perceived exertion were recorded and analyzed. RESULTS: The results showed that both load and handle height were significant (p < 0.0001) factors affecting the MET. Regression models to predict the MET under handle height and load conditions were established. The mean absolute deviations of these models were between 1.91 and 4.84 min. CONCLUSION: The MET models established may be used to estimate the MET which may be adopted in work/rest arrangement for demolition tasks using a handheld demolition hammer.

Muscle Recovery after a Single Bout of Functional Fitness Training.

BACKGROUND: Functional fitness training (FFT) is a new exercise modality that targets functional multi-joint actions via both muscle-strengthening exercises and aerobic training intervals. The aim of the study was to examine muscle recovery over a 20 min period after an FFT workout in trained adults. MATERIALS AND METHODS: Participants were 28 healthy trained subjects. In a single session, a countermovement jump (CMJ) was performed to determine several mechanical variables (jump height, maximum velocity, power) before (preFFT) and 4, 10, and 20 min after the FFT workout (postFFT). In parallel, capillary blood lactate concentrations were measured pre- and 3 min postFFT. Heart rate was also measured before and after the workout, and perceived exertion was measured postFFT. RESULTS: Significant differences between the time points preFFT and 4 min and 10 min postFFT, respectively, were produced in jump height (p = 0.022, p = 0.034), maximum velocity (p = 0.016, p = 0.005), average power relative (p = 0.018, p = 0.049), and average power total (p = 0.025, p = 0.049). No differences were observed in any of the variables recorded preFFT and 20 min postFFT. CONCLUSIONS: While mechanical variables indicating muscle fatigue were reduced 4 and 10 min postFFT, pre-exercise jump ability only really started to recover 20 min after FFT although not reaching pre-exercise levels. This means that ideally intervals of around 20 min of rest should be implemented between training bouts.

Hand grip strength and fatigability: correlation with clinical parameters and diagnostic suitability in ME/CFS.

BACKGROUND: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a complex and debilitating disease accompanied by muscular fatigue and pain. A functional measure to assess muscle fatigability of ME/CFS patients is, however, not established in clinical routine. The aim of this study is to evaluate by assessing repeat maximum handgrip strength (HGS), muscle fatigability as a diagnostic tool and its correlation with clinical parameters. METHODS: We assessed the HGS of 105 patients with ME/CFS, 18 patients with Cancer related fatigue (CRF) and 66 healthy controls (HC) using an electric dynamometer assessing maximal (Fmax) and mean force (Fmean) of ten repetitive measurements. Results were correlated with clinical parameters, creatinine kinase (CK) and lactate dehydrogenase (LDH). Further, maximum isometric quadriceps strength measurement was conducted in eight ME/CFS patients and eight HC. RESULTS: ME/CFS patients have a significantly lower Fmax and Fmean HGS compared to HC (p < 0.0001). Further, Fatigue Ratio assessing decline in strength during repeat maximal HGS measurement (Fmax/Fmean) was higher (p ≤ 0.0012). The Recovery Ratio after an identical second testing 60 min later was significantly lower in ME/CFS compared to HC (Fmean2/Fmean1; p ≤ 0.0020). Lower HGS parameters correlated with severity of disease, post-exertional malaise and muscle pain and with higher CK and LDH levels after exertion. CONCLUSION: Repeat HGS assessment is a sensitive diagnostic test to assess muscular fatigue and fatigability and an objective measure to assess disease severity in ME/CFS.

Quantification of the effect of compression garments on fatigue behavior in cycling.

Effectiveness of compression garments to enhance athletic performance is the subject of numerous qualitative studies. This study aims at quantification of the effect of compression garments using nonlinear dynamics approach. Kinematic data of fifteen healthy male athletes was obtained and the state space was reconstructed. The trajectory drifts caused by fatigue in the state space were quantified using local flow variation technique. The study illustrates that compression garments (CGs) decrease rate of fatigue development and the body exhibits a more restricted complexity (more predictable and smaller fluctuations) when CGs are worn.

How to assess the recovery of muscular function following nerve injury: A view from surgeons and patients.

Patient experience of motor recovery from denervation paralysis is complex and textured. The Medical Research Council (MRC) system of grading muscle peak volitional force is widely used as a single measure of assessment. However, it is becoming clear that current motor function assessments are not reflecting the patient lived experience of muscle reinnervation. Therefore, this study aimed to engage international expert nerve surgeons in a classical Delphi process to achieve a consensus of opinion on the ideal clinical assessment of motor function. This was compared with patient-reported impairments of reinnervated muscle. Invitations to engage in the Delphi process were extended to expert peripheral nerve surgeons across two international specialist meetings. For comparison, patients who attended a "Nerve Injury Community Day" were invited to complete a questionnaire on patient-reported impairments of reinnervated muscle. Questions were designed on the basis of a literature review and the clinical experiences of a specialist nerve injury unit. A combination of direct yes/no, multiple choice, open-ended and Likert questions were employed throughout the questionnaires. Eighteen surgeons engaged with the Delphi process; 18 and 11 responded to the first and second rounds respectively. Thirty-one patients responded to the questionnaire. It was found that clinicians were strongly biased towards efferent assessments of muscular function, while patients strongly favoured muscular fatigue, co-contraction and pain when monitoring their own recovery. The findings suggest that current clinical assessments of muscular function are inadequate and should embody measurements of afferent muscular function to better reflect the lived experience of muscle reinnervation.

Effects of a lower limb muscular fatigue on posture-movement interaction during a lower limb pointing task.

PURPOSE: The aim of the present study was to investigate the effects of muscular fatigue on the interaction between posture and movement during a lower limb pointing task. METHODS: Participants (n = 16), aged 18-30 years, kicked a ball toward a target in four conditions of fatigue: No muscular fatigue (NF), fatigue in the kicking (FM) or postural limb (FP) alone, and fatigue in both limbs (FMP). The mean amplitude and speed of the centre of foot pressure (CoP) and centre of mass (CoM) displacements were estimated through a force platform and an optoelectronic system, respectively. In addition, surface electromyography (EMG) of the biceps femoris, rectus femoris, medial gastrocnemius, and peroneus longus was recorded to investigate the anticipatory postural adjustments (APAs). RESULTS: Muscular fatigue yielded a decreased kicking accuracy (p < 0.001) and an increased time to perform the movement (p < 0.001), mainly during the backswing motion. In addition, significant increases in the mean amplitude and speed of the CoP and CoM displacement were found in the anteroposterior (AP) and mediolateral (ML) axes (ps < 0.001), especially when both limbs were fatigued. The EMG analysis confirmed that fatigue modified the way APAs were generated. During fatigue, postural muscle activity increased, but was delayed with respect to movement onset (ps < 0.001). This pattern of response was more consistent when both limbs were fatigued (p < 0.001). CONCLUSION: The present results suggested an additive effect of fatigue and a functional adaptation and subsequent decrease in the overall variability of APAs, indicating that postural and motor processes are interdependent.

Maytenus ilicifolia Extract Increases Oxygen Uptake without Changes in Neuromuscular Fatigue Development during a High-Intensity Interval Exercise.

OBJECTIVE: We investigated the effects of acute ingestion of Maytenus ilicifolia extract on metabolic and cardiopulmonary responses during a high-intensity interval exercise (HIIE), and its consequence on neuromuscular fatigue. METHODS: Ten healthy men underwent a HIIE (4 x 4 min, 3 min recovery) one hour after ingesting 400 mg of Maytenus ilicifolia extract (MIE) or placebo. Oxygen uptake (V̇O2), dioxide carbon production (V̇CO2), ventilation (V̇E) and heart rate (HR) were measured throughout the HIIE. Maximal voluntary contraction (MVC), voluntary activation (VA), and evoked 1, 10 and 100 Hz force twitch were measured before supplementation (baseline), and before (pre-HIIE) and after the HIIE (post-HIIE). RESULTS: The V̇O2, V̇E, V̇E/V̇O2 ratio and HR increased progressively throughout the HIIE under both conditions (p < 0.05). MIE increased HR, however, at bouts 1 and 2 and mean V̇O2 during HIIE. The mean respiratory exchange ratio during recovery was also reduced with MIE (p < 0.05). MVC and evoked force at 1, 10 and 100 Hz declined similarly after HIIE, regardless of the condition (MIE: -18 ± 17%, -50 ± 15%, -61 ± 13% and -34 ± 10% vs. placebo: -19 ± 15%, -48 ± 16%, -58 ± 12 and -29 ± 11%, respectively, p < 0.05). There was no effect of exercise or MIE on VA (p > 0.05). CONCLUSION: MIE increases heart rate in the first bouts and mean oxygen uptake during HIIE without changes in neuromuscular fatigue development.

Photobiomodulation Before Eccentric Fatigue Protocol in the Control of Pain and Muscle Damage Markers: A Double-Blind, Randomized Controlled Study.

Background: Several strategies are used in the management of delayed-onset muscle soreness (DOMS), but there is not always evidence to justify its use. Photobiomodulation (PBM) is a noninvasive means, with promising previous results of its use in this outcome. Objective: This study aimed to identify the effects of PBM in the femoral quadriceps region to reduce DOMS in men undergoing a fatigue protocol. Methods: This is a double-blind, randomized controlled study. The sample consisted of 35 physically active men. The volunteers were divided into two groups: pre-fatigue PBM [Group 1 (G1)] and post-fatigue PMB [Group 2 (G2)]. The fatigue test was conducted at the same time of day. Given this was a crossover study of volunteers, we used at least a 1-week washout to avoid any residual interference from the previous intervention. PBM (active/placebo) was performed 5 min before the start of the fatigue protocol in G1 and immediately after the fatigue protocol in G2. PBM was applied at six points on the femoral quadriceps muscle (cluster laser/light emitting diodes 13, 415 mW, 30.2 J per point, 73 sec per application, and total dose of 181.2 J). In the data analysis, the primary endpoint was DOMS measured using a Numerical Pain Scale, and the secondary outcome was examined on the effects of PMB muscle damage, muscle contraction, and isometric horizontal jump. Results: There were significant differences to PBM compared with the placebo group for DOMS, with no differences between the times of application. For muscle damage, there was significant difference (p > 0.05) when PBM was applied in pre-fatigue. G1 led to an increase of 14.9% in the creatine kinase level when active since the application of placebo PBM increased by 65% (p = 0.04). Conclusions: The PBM applied before eccentric fatigue protocol showed no significant results on DOMS, although there was a positive effect to control muscle damage. Brazilian Registry of Clinical Trials (RBR-7qhddz).