Search

This study aimed to determine the intra-day reliability, individuals performance expectancy, and biomechanical response of nine stretching instructions in assessing the maximal range of motion (mROM) during the passive ankle dorsiflexion test. Twenty healthy young participants were tested in two sessions within the same day. Nine stretching instructions composed by intensity-domain (i.e. minimum, point, and maximum) and sensation-domain (i.e. tolerance, discomfort, and pain) words were used to impose plantar flexors stretching. In the first session, individuals were requested to order the nine stretching instructions in ascending order. The ankle joint torque-angle and medial gastrocnemius, soleus and tibialis anterior electric activity were assessed in both sessions. A moderate to high reliability was observed across instructions (ICC = 0.65-0.87). Most stretching instructions showed high intra-day reliability outcomes, where discomfort and tolerance showed moderate reliability. 70% of individuals performed the stretching maneuvers consistently to stretching instructions performance expectancy. A greater torque-angle response was observed for the instructions involving the word pain (ROM = 40.5 ± 1.6°), compared to discomfort (29.5 ± 1.8°), and tolerance (30.5 ± 2.0°) that produced similar stretching intensities. Instructions involving the terms minimum (29.6 ± 2.0°), point (33.3 ± 7.6°), and maximum (37.6 ± 7.2°) were more discriminative of stretching intensities than sensation-domain terms. In conclusion, stretching instructions targeting the joint maximal range of motion produce different joint torque-angle responses and they may not be understandable by all individuals, although (in general) they can be used reliably.

Background: In football (ie, soccer), the effectiveness of recovery practices is critical to maintain high levels of performance, prevent residual fatigue, and reduce injury risk. However, the recovery methods that professional football teams put in place up to 72 hours postmatch are widely unknown. Purpose: This study aimed to characterize the postmatch recovery practices in Portuguese football teams in different postmatch periods and match locations. Methods: Portuguese football teams (total, N = 56; male: first league [n = 17], second league [n = 16], under-23 league [n = 12]; female: first league, n = 11) participated in the study. The practitioners in charge of recovery strategies in each team filled out the online questionnaire in the middle of the 2019–20 season. The questions focused on the type of recovery methods to be used at different times after home and away matches. Results: After home matches, stretching, electrostimulation, active recovery, and massage were used with higher frequency (P P r = .19), active recovery (r = .39), cold-water immersion (r = .46), and massage (r = .29) showed a higher frequency of use immediately after home matches. Conversely, the use of compression garments (r = .27) was higher immediately after away matches. Conclusions: It was concluded that in professional football, recovery methods are not applied uniformly along postmatch periods and differ depending on the match location.

Trunk modification is associated with knee abduction moment reduction in both healthy groups and individuals with knee osteoarthritis. Ambulatory-related changes in trunk kinematics have been implicated in increased trunk moment. The purpose of this study was to investigate the effect of dose-specific lateral trunk lean on trunk kinetics during ipsilateral and contralateral stance phases. Nineteen healthy participants completed 10 baseline walking trials, followed by 10 trials employing lateral trunk lean. Trunk modification magnitudes were determined based on the average baseline trunk angle. Five trials of both small and large trunk modification magnitudes were completed. Visual real-time biofeedback was projected as a line graph displaying the trunk angle during stance, and a highlighted bandwidth was designated the target range. A 1-factor repeated-measures analysis of variance or Friedman test was used to assess differences between the conditions (P

Background: The effect of 10 × 30 m repeated sprints on passive and active stiffness of semitendinosus (ST) and biceps femoris long head (BFlh), and knee flexor maximal voluntary isometric contraction (MVIC) and rate of force development (RFD), and whether athletes with previous hamstring injury have a different response, is unknown. Hypothesis: Repeated sprints would (1) increase BFlh stiffness and decrease ST stiffness and knee flexors MVIC and RFD in healthy participants; and (2) greater magnitude of response would be seen in athletes with previous hamstring injury. Study Design: Case series (experiment I) and case control (experiment II) study designs. Level of Evidence: Level 3. Methods: Healthy nonathletes attended 2 replicated sessions (experiment I, n = 18), while soccer players with (n = 38) and without (n = 67) previous hamstring injury attended 1 testing session (experiment II). Results: In both experiments, the knee flexors MVIC and RFD decreased after the sprints ( P < 0.05). In experiment I, the ST and BFlh passive stiffness reduced after the sprints ( P < 0.02), while a small BFlh active stiffness increase was noted ( P = 0.02); however, no correlation was observed between the 2 testing sessions for the postsprint muscle stiffness responses ( r = -0.07-0.44; P > 0.07). In experiment II, only an ST passive stiffness reduction was observed after the sprints ( P < 0.01). No differences were noted between injured and noninjured lower limbs for any variable ( P > 0.10). Conclusion: Repeated sprints are likely to decrease the knee flexor’s maximal and rapid strength, and to alter the hamstring stiffness in the nonathlete population. Previous hamstring injury does not apparently affect the footballer’s hamstring functional and mechanical responses to repeated sprints. Clinical Relevance: The responses of hamstring stiffness and knee flexor strength to repeated sprints are unlikely to be associated with hamstring injury.

This study examined whether professional footballers with previous biceps femoris long head (BFLH) injury in the last 3-years present a smaller proximal aponeurosis (Apo-BFLH) size compared to footballers with no previous injury. We examined the Apo-BFLH and BFLH size using magnetic resonance imaging and tested the knee flexor maximal isometric strength in 80 thighs of 40 footballers. Apo-BFLH size parameters were processed using a semi-automated procedure. Outcomes were compared between thighs with (n=9) vs. without (n=71) previous BFLH injury. No differences were observed between injured and non-injured thighs for the Apo-BFLH and BFLH size parameters (p>0.05) except for Apo-BFLH volume, which was higher in the non-injured thighs of athletes with previous injury (3692.1±2638.4 mm3, p

Dancers frequently perform jump-landing activities, with the foot-ankle complex playing an essential role to attenuate the landing forces. However, scarce research has been conducted in professional dancers multi-segmented foot in landings. The aim of this study was to compare the multi-segmented foot kinematics between professional dancers and non-dancers, during forward and lateral single-leg jump-landings.Descriptive group comparison.Marker trajectories and synchronized ground reaction forces of 15 professional dancers and 15 non-dancers were collected using motion capture and a force plate, during multidirectional single-leg jump-landings. Sagittal and frontal hindfoot-tibia, forefoot-hindfoot, and hallux-forefoot kinematics of the multi-segmented foot model were computed at initial contact, peak vertical ground reaction force and peak knee flexion. Repeated measures ANOVAs were conducted (p 0.05).Professional dancers landed with higher hindfoot-tibia and forefoot-hindfoot plantarflexion angles at initial contact (p 0.001), and hindfoot-tibia dorsiflexion angles at peak vertical ground reaction force and peak knee flexion (p 0.001) than non-dancers. Also, dancers exhibited higher sagittal hindfoot-tibia and forefoot-hindfoot excursions than non-dancers (p 0.001). No statistically significant differences were found in the frontal plane.The multi-segmented foot allows a comprehensive kinematic analysis of the different foot joints. In jump-landings, professional dancers higher hindfoot-tibia, and forefoot-hindfoot plantarflexion at initial contact, compared to non-dancers, contributed to a subsequent higher foot joints excursion. This pattern is commonly linked to a better shock absorption mechanism in landings.

espanolObjetivo: cuantificar y comparar la actividad electromiografica de 10 musculos en tres diferentes ejercicios de pullover. Metodo: 15 hombres sanos, con al menos 2 anos de experiencia en entrenamiento de resistencia, realizaron seis repeticiones al 60% de 1 Repeticion Maxima en orden aleatorio para tres ejercicios de pullover diferentes: acostados en una tabla con mancuernas y agarre 100% biacromial (E1), acostados en una tabla con mancuernas, agarre 150% biacromial (E2) y acostado en una pelota suiza con mancuernas, agarre 100% biacromial (E3). Se registro la senal electromiografica de superficie de Deltoides (anterior y posterior), Pectoral Mayor (clavicular y esternocostal), Serrato Anterior, Triceps Braquial (porcion externa), Dorsal Grande, Infraespinoso, Recto Abdominal, Oblicuo Interno y Transverso del Abdominal. Se calculo la Repeticion Maxima normalizada para cada musculo y para cada ejercicio. Resultados: los musculos mas involucrados fueron el Infraespinoso (51-53%) y el Deltoides Posterior (49-51%). La actividad electromiografica de superficie fue similar entre los ejercicios E1, E2 y E3. Conclusiones: este estudio cuantifico las demandas musculares durante los ejercicios pullover realizados con un 60% de la Repeticion Maxima. Los musculos con mayor nivel de activacion fueron el Deltoides Posterior e Infraespinoso, lo que sugiere que el pullover puede ser una opcion valida para fortalecer los musculos estabilizadores dinamicos de la articulacion del hombro en individuos entrenados. No se observaron diferencias significativas en el nivel de la activacion muscular cuando se modifico la distancia del agarre y la estabilizacion del tronco, lo que demuestra que estas condiciones no influyen en los niveles de activacion muscular. Sin embargo, 1 Repeticion Maxima fue menor cuando el pullover se realizo en una pelota suiza, lo que sugiere que es posible obtener un mayor nivel de reclutamiento muscular con pesos menores en ejercicios inestables. EnglishObjective: To quantify and compare the electromyographic activity of 10 muscles in three pullover exercises. Methods: 15 healthy men, with at least two years of experience in resistance training, executed in random order six repetitions with 60% of 1 Maximum Repetition for three different pullover exercises: lying on a step with a barbell, grip 100% biacromial (E1); lying on a step with a barbell, grip 150% (E2); lying on a Swiss ball with a barbell, grip 100% (E3). Surface electromyography was recorded from the Deltoideus (Clavicular and Spinalis Pars), Pectoralis Major (Clavicular and Sternocostalis Pars), Serratus Anterior, Triceps Brachii (Long Head), Latissimus Dorsi, Infraspinatus, Rectus Abdominis, Obliquus Internus Abdominis and Transversus Abdominis. The normalized Maximum Repetition electromyographyc of each muscle was calculated for each exercise. Results: The most engaged muscles were Infraspinatus (51-53%) and Posterior Deltoid (49-51%). Surface electromyography activity was similar between the E1, E2 and E3 exercises. Conclusions: This study quantified muscular solicitation during pullover exercises performed with 60% Maximum Repetition. The muscles with higher level of activation were the Posterior Deltoid and the Infraspinatus, suggesting that pullover may be a valid option for strengthening the dynamic stabilizing muscles of shoulder joint in trained individuals. No significant differences in muscle electromyography intensity were observed when grip distance and trunk stabilization were altered, showing that these conditions do not influence muscle activation levels. However, the 1 Maximum Repetition was lower when the pullover was performed on a Swiss ball, suggesting that it is possible to obtain higher level of muscle recruitment with lower weights in unstable exercises. portuguesObjetivo: Quantificar e comparar a atividade eletromiografica de 10 musculos em tres exercicios pullover. Metodo: 15 homens saudaveis, com pelo menos dois anos de experiencia em treinamento resistido, executaram em ordem aleatoria seis repeticoes com 60% de 1 Repeticao Maxima para tres exercicios pullover diferentes: deitado em um step com barra e pegada 100% biacromial (E1), deitado no steep com barra e pegada 150% biacromial (E2) e deitado em uma bola suica (fitball) e pegada 100% biacromial (E3). A atividade eletromiografica de superficie foi registrada dos musculos Deltoide (Clavicular e Spinalis Porcao), Peitoral Maior (Porcao Clavicular e Esternocostal), Serratil Anterior, Triceps Braquial (Cabeca Longa), Grande Dorsal, Infraespinhal, Reto Abdominal, Obliquo Interno Abdominal e Transverso Abdominal. A atividade eletromiografica de uma Repeticao Maxima normalizada de cada musculo foi calculada para cada exercicio. Resultados: Os musculos mais envolvidos foram o infraespinal (51-53%) e o Deltoide Posterior deltoide (49-51%). A atividade eletromiografica foi semelhante entre os exercicios E1, E2 e E3. Conclusoes: Este estudo quantificou a solicitacao muscular durante exercicios pullover realizados com 60% de Repeticao Maxima. Os musculos com maior nivel de ativacao foram o Deltoide Posterior e o Infraspinatus, sugerindo que o pullover pode ser uma opcao valida para o fortalecimento dos musculos estabilizadores dinâmicos da articulacao do ombro em individuos treinados. Nao foram observadas diferencas significativas na intensidade da atividade eletromiografica muscular quando a distância da pegada e a estabilizacao do tronco foram alteradas, mostrando que essas condicoes nao influenciam os niveis de ativacao muscular. No entanto, a 1 Repeticao Maxima foi menor quando o pullover foi realizado em uma bola suica (fitball), sugerindo que e possivel obter maior nivel de recrutamento muscular com pesos menores em exercicios instaveis.

Torque outputs exhibit non-random fluctuations in their temporal structure, i.e., complexity. Fatigue has been shown to alter this structure. The torque outputs typically become more regular, resulting in decreased adaptability. Importantly, torque complexity was shown a different recovery pattern after fatigue compared to maximal torque. However, it remains to be understood if these uncoupled patterns of recovery are muscle dependent. In addition, it also remains to be investigated if changes in maximal torque and complexity are correlated. This study investigated (i) the effects of a fatiguing protocol on the complexity and maximal torque from plantar flexors and (ii) the relationship between changes in these two outputs. Ten participants visited the laboratory, and measures were taken at baseline, immediately after, 1 h after and 24 h after the fatiguing protocol. Maximum voluntary contraction, isometric contractions at 30% of maximum and pain pressure threshold were collected. Both legs were assessed, but only one was given the fatiguing protocol. Two-way ANOVAs and correlations were conducted. The fatiguing protocol decreased torque complexity (~35%) and maximal torque (~20%), and they exhibited uncoupled patterns of recovery. Moreover, the correlation analysis showed no correlation between changes in these parameters. These findings support that these parameters are independent of each other.

Background: Each year, 1 in 4 people over the age of 65 years of age will experience a fall. It is important to identify and address modifiable risk factors that are associated with falls in adults at high and low risk for falls. Hypothesis: Falls risk improves in both high-risk and low-risk participants with the implementation of Stay Active and Independent for Life (SAIL). Study Design: Cohort study Level of Evidence: Level 3. Methods: Seventy-eight older adults (age, 70.9 ± 5.1 years) were included in this study and categorized into high risk and low risk for falling based on the falls risk score from the Physiological Profile Assessment. High risk was defined as having a preintervention falls risk score >1, whereas low risk was defined as having a preintervention falls risk score Results: Results showed that regardless of preintervention falls risk, participants showed significant improvements in right and left knee extensor strength and sit-to-stand after participation in the 10-week SAIL program. Also, noteworthy is that 15 participants who were considered at high risk for falling preintervention were considered low risk for falling postintervention. Conclusion: The positive outcomes noted on modifiable risk factors suggest SAIL can be beneficial for decreasing falls risk in older adults, regardless of risk of falling, using a multifactorial exercise intervention. Our results also showed that it was possible for participants not only to improve falls risk but to improve to such a degree that they change from high risk to low risk of falling. Clinical Relevance: Our results demonstrated that SAIL was effective in improving overall fall risk after a 10-week intervention. Targeted community-based interventions for the aging population can bring physical health benefits that can decrease falls risk.

Background: Sleep, nutrition, active recovery, cold-water immersion, and massage were recently reported as the most used postmatch recovery methods in professional football. However, the recommendations concerning the effect of these methods remain unclear. Purpose: To systematically review the literature regarding the effectiveness of the most common recovery methods applied to male and female football players (or other team sports) 72 hours postmatches and to provide graded recommendations for their use. Methods: A systematic search of the literature was performed, and the level of evidence of randomized and nonrandomized studies was classified as 1 or 2, respectively, with additional ++, +, and − classification according to the quality of the study and risk of bias. Graded recommendations were provided regarding the effectiveness of recovery methods for physical, physiological, and perceptive variables. Results: From the 3472 articles identified, 39 met the inclusion criteria for analysis. The studies’ levels of evidence varied among methods (sleep: 2+ to 1++; nutrition: 2− to 1+; cold-water immersion: 2− to 1++; active recovery: 2− to 1+; and massage: 1− to 1+). Different graded recommendations were attributed, and none of them favored the effective use of recovery methods for physiological and physical parameters, whereas massage and cold-water immersion were recommended as beneficial for perceptive variables. Conclusions: Cold-water immersion and massage can be recommended to recover up to 72 hours postmatch at a perceptive level. However, there is a current need for high-quality research that identifies effective recovery strategies that enhance recovery at the physical and physiological levels.

The ability to produce high movement speeds is a crucial factor in human motor performance, from the skilled athlete to someone avoiding a fall. Despite this relevance, there remains a lack of both an integrative brain-to-behavior analysis of these movements and applied studies linking the known dependence on open-loop, central control mechanisms of these movements to their real-world implications, whether in the sports, performance arts, or occupational setting. In this review, we cover factors associated with the planning and performance of fast limb movements, from the generation of the motor command in the brain to the observed motor output. At each level (supraspinal, peripheral, and motor output), the influencing factors are presented and the changes brought by training and fatigue are discussed. The existing evidence of more applied studies relevant to practical aspects of human performance is also discussed. Inconsistencies in the existing literature both in the definitions and findings are highlighted, along with suggestions for further studies on the topic of fast limb movement control. The current heterogeneity in what is considered a fast movement and in experimental protocols makes it difficult to compare findings in the existing literature. We identified the role of the cerebellum in movement prediction and of surround inhibition in motor slowing, as well as the effects of fatigue and training on central motor control, as possible avenues for further research, especially in performance-driven populations.

Maintaining the range of motion in repetitive movement tasks is a crucial point since it directly influences the movement rate. Ensuring the movement amplitude can be reliably maintained when motor function is assessed by measuring the maximum movement rate is therefore a key consideration. However, the performed range of motion during such tasks is often not reported. This study aimed to determine whether individuals are able to maintain an intended range of motion during a knee flexion/extension maximum movement rate task in the absence of tactile and visual feedback. Twelve healthy male individuals performed knee flexion/extension at maximum speed for eight 10-s blocks in a 45° arc between 45° and 90°. The range of motion was monitored using a marker system and the movement rate was measured. The performed range of motion was not significantly different from the 45° arc during the task despite a 13.47% decrease in movement rate from the start to the end of the task. Nevertheless, there was only anecdotal evidence of no difference from 45° in most blocks, while on the second and seventh blocks, there was anecdotal evidence of differences in the Bayesian one-sample test. There was also no significant shift in the maximum flexion/extension angles throughout the task. Healthy male individuals were thus able to perform a consistent average predefined knee range of motion in a maximum movement rate task despite decreases in movement rate. This was achieved without constraint-inducing devices during the task, using only basic equipment and verbal feedback.

Walking with different types of cueing/stimulus (i.e. auditory, visual) has shown to alter gait variability, thus emerging as an innovative therapeutical tool to restore abnormal gait variability in clinical populations. However, the majority of the research in this area has focused on auditory stimulus, while visual stimulus is an understudied alternative that needs more attention, particularly due to the natural dependence on vision during walking. Furthermore, the time differences between the occurrences of the walking steps and the sensory cues, also known as asynchronies, have also received minimal attention even though how well will synchronize with different stimuli is of great importance. This study investigated how synchronizing to visual stimulus that is presented with different temporal structures could affect gait variability and their respected asynchronies. Participants performed four 15-minute walking trials around an indoor track while wearing insole footswitches for the following conditions: a) self-paced walking, and b) walking with glasses that instructed the subjects to step in sync with a virtual moving bar. The stepping occurences of the moving bar were presented in three different ways b1) non-variable, b2) variable and b3) random. Stride times and asynchronies were determined, and the mean values along with the fractal scaling (an indicator of the complexity) in their time series, were calculated. The fractal scaling of the stride times was unaltered when participants walked with the variable stimulus as compared to the self-paced walking condition; while significantly decreased during the non-variable and random conditions indicating a loss of complexity for these two conditions. Regarding the asynchronies, no differences were observed in the means or the fractal scaling of the asynchronies. The correlation analysis between stride times and asynchronies revealed a strong relationship for the non-variable condition but a weak one for both variable and random conditions. Taken together, the present study results supports the idea of an existing internal timekeeper that exhibits complexity. We have shown that this complex pattern is similar regardless of the stimulus condition, suggesting that the system’s complexity is likely to be expressed at the task performance level – asyncrhonies – when walking to a stimulus. Thus, future research in sensoriomotor gait synchronization should focus and further explore the role of the asynchronies as it may be of clinical significance.

Introduction: The use of oral appliances to enhance sports performance has been advocated by some authors, however, studies addressing the effectiveness of these strategies are inconclusive. Methods: Here we investigate the effects of dental occlusions on shoulder strength. Fourteen healthy male subjects (age = 21.67 ± 0.86 years) without temporomandibular joint (TMJ) disorder participated in this study. Isokinetic strength was evaluated in shoulder abduction/adduction and arm external/internal rotation tests. Three randomised conditions were assessed: (1) occlusal splint (OS), which repositioned the TMJ in centric relation; (2) placebo splint (PS); and (3) no-splint (N). The strength tests were performed at a speed of 60°/sec in concentric mode. Muscle activity was measured by surface electromyography (EMG) in the main muscles engaged in the movements. Results: Significant differences in peak torque between OS and both of the other experimental conditions were found in some of the analyzed variables. Moreover, there was significantly higher muscular EMG activation in the OS condition when compared to the other conditions for some of the tested muscles. These data suggest that splints may have a positive ergogenic effect on shoulder muscular strength in healthy male subjects. Conclusion: KEY MESSAGES: Occlusal splints in centric relation position have an ergogenic effect, by increasing strength and muscle activation on shoulder in healthy subjects. These results could have implications for sports or other physical activities were arm and shoulder strength are important.

PURPOSE This study aimed to compare lower extremity (LE) biomechanics between professional dancers (PD) and nondancers (ND) during multidirectional single-leg landings. METHODS Fifteen PD (27 ± 7 yr, 1.69 ± 0.1 m, 57.8 ± 9.3 kg) and 15 ND (25 ± 5 yr, 1.69 ± 0.1 m, 66 ± 10.2 kg) performed single-leg jumps in three directions: 1) lateral, 2) diagonal, and 3) forward. Dominant LE biomechanical data were collected using a motion capture system. Data were processed in Visual3D. LE kinematic (hip, knee, and ankle joint angles in sagittal and frontal planes, and range of motion [ROM]) and kinetics (hip and knee internal joint moments and vertical ground reaction force) variables were analyzed at initial contact (IC), peak vertical ground reaction force (PvGRF), and peak knee flexion (PKF). Repeated-measures ANOVA was conducted (P < 0.05). RESULTS At IC, statistically significant interactions were found for ankle frontal and hip sagittal angles (P < 0.05). The main effects for groups and jump directions were attained (P < 0.05). PD at IC had lower hip and knee flexion and higher ankle plantarflexion than ND. PD had significantly higher knee (PD, 41 ± 6.1; ND, 33.8 ± 8.4) and ankle (PD, 53.7 ± 3.4; ND, 38.9 ± 8.9) ROM than ND. At IC, the lateral jump had higher hip abduction moment, hip abduction, and ankle inversion and lower hip flexion and ankle plantarflexion than the forward and diagonal jumps. The lateral jump (15.5 ± 7.7) had higher hip excursion than the forward jump (12.7 ± 5.4). CONCLUSION The higher extended posture of PD at IC promoted an efficient use of the knee and ankle ROM to dissipate the landing forces. Regardless of the group, jump directions also solicited different biomechanical responses, particularly between lateral and forward directions. These strategies should be considered for implementation in prevention programs, as it can foster adequate LE neuromuscular control.

This study sought to examine the active stiffness of semitendinosus (ST) and biceps femoris long head (BFlh) during a knee flexor isometric contraction at 20% of maximal voluntary isometric contraction until failure in elite footballers (n=50, age: 22.3±5.3 years; height: 1.82±0.08 m; body mass: 74.7±9.0 kg). Active stiffness was assessed using ultrasound-based shear wave elastography by means of shear modulus quantification. Comparisons were performed between limbs with (n=11) vs. without (n=89) previous hamstring injury. Similar time until failure in the knee flexor fatigue task was observed between groups (p=0.401). At the start of the task, lower limbs with previous hamstring injury showed a lower BFlh active stiffness (31.0.1±10.4 kPa, p=0.023) and BFlh/ST active stiffness ratio (0.50±0.29), and no differences for ST (72.8±26.8 kPa, p=0.221) compared to lower limbs without previous hamstring injuries (BFlh: 38.0±9.6 kPa; ST: 64.0±18.4 kPa; BFlh/ST: 0.65±0.27). During the task, the ST active stiffness in both groups decreased from 80% of task time (p=0.032), in the absence of changes in BFlh active stiffness (p=0.534), resulting in an increase in BFlh/ST active stiffness from 80% of task time (p=0.029). No differences between limbs were observed during the fatigue task for all parameters (p>0.099). Future research is warranted to verify if the differences found represent an increased risk of hamstring injury.

Muscle coordination in human movement has been assessed through muscle synergy analysis. In sports science, this procedure has been mainly applied to the comparison between highly trained and unexperienced participants. However, the lack of knowledge regarding strength training exercises led us to study the differences in neural strategies to perform the power clean between weightlifters and untrained individuals. Synergies were extracted from electromyograms of 16 muscles of ten unexperienced participants and seven weightlifters. To evaluate differences, we determined the pairwise correlations for the synergy components and electromyographic profiles. While the shape of activation patterns presented strong correlations across participants of each group, the weightings of each muscle were more variable. The three extracted synergies were shifted in time with the unexperienced group anticipating synergy #1 (−2.46 ± 18.7%, p &lt, 0.001) and #2 (−4.60 ± 5.71%, 0.001) and delaying synergy #3 (1.86 ± 17.39%, p = 0.01). Moreover, muscle vectors presented more inter-group variability, changing the composition of synergy #1 and #3. These results may indicate an adaptation in intermuscular coordination with training, and athletes in an initial phase of training should attempt to delay the hip extension (synergy #1), as well as the upper-limb flexion (synergy #2).

This study examined whether a knee flexor isometric contraction at 20% of maximal voluntary isometric contraction until exhaustion would alter the biceps femoris long head (BFlh) and semitendinosus (ST) active stiffness, assessed using ultrasound-based shear wave elastography. Twelve healthy individuals participated in 2 sessions separated by 7 days. Time to exhaustion was similar in both sessions (day 1: 443.8 ± 192.5 s; day 2: 474.6 ± 131.7 s; p = 0.323). At the start of the fatigue task, the ST showed greater active stiffness than the BFlh (p

Knee valgus motion observed during landing tasks has been proposed as a predictor of future knee injury. It mainly involves excess motion in the frontal plane and is known to be greater in individuals with excessive medial knee displacement (MKD). This affects postural control during sports manoeuvres. Previous sports medicine-related research suggests that the nature of these fluctuations provide rich and more sensitive information to identify risk of (re)injury. We aimed to investigate the fluctuations of the centre of pressure (CoP) in individuals with and without excessive MKD. Twenty females (12 controls; 8 excessive MKD) were instructed to perform single-leg landing tasks from three different directions. The participants landed on a force plate and stayed still for 20 seconds. The fluctuations of the anterior-posterior and medial-lateral directions of the CoP were determined through the calculation of Sample Entropy. Mixed-model ANOVAs (3 [Landing Direction] x 2 [Group]) were used. We have found that only the entropy of the medial-lateral direction was different between groups. Individuals with excessive MKD exhibited an increase in entropy values, indicating greater randomness in CoP fluctuations. This suggests a decreased ability to adapt to environmental demands that likely result in an increased risk of injury.

This study investigated the relationship between back squat depth capacity, ankle dorsiflexion resistance to stretch and maximal range of motion (ROM), and Achilles tendon stiffness of healthy individuals (n = 20). Squat depth capacity was assessed with 2D kinematic analysis. Ankle dorsiflexion maximal ROM was assessed using a smartphone digital goniometry (lunge test) and isokinetic dynamometry (prone test). Ankle dorsiflexion resistance to stretch was assessed during the prone test. Achilles tendon stiffness was estimated at rest [using shear wave elastography (stiffness-SWE)] and during isometric contraction through tendon force-length relationship (using B-mode sonography). Squat depth was associated only with ankle dorsiflexion ROM in the lunge test (r = 0.69, p = 0.001). Ankle dorsiflexion ROM in the lunge test was associated with the ankle resistance to stretch (r = 0.46, p = 0.050) and Achilles tendon stiffness-SWE (r = 0.62, p = 0.005); and it was the only variable different between individuals with low and high squat depth capacity (p = 0.014). No other statistically significant associations were found. In conclusion, back squat depth is associated with ankle dorsiflexion ROM when the knee is flexed, without evident influence of global joint and Achilles tendon mechanical properties.

Purpose:To investigate the muscle-activation patterns and coactivation with the support of kinematics in some of the world’s best breaststrokers and identify performance discriminants related to national elites at maximal effort.Methods:Surface electromyography was collected in 8 muscles from 4 world-class (including 2 world champions) and 4 national elite breaststroke swimmers during a 25-m breaststroke at maximal effort.Results:World-class spent less time during the leg recovery (P = .043), began this phase with a smaller knee angle (154.6° vs 161.8°), and had a higher median velocity of 0.18 m/s during the leg glide than national elites. Compared with national elites, world-class swimmers showed a difference in the muscle-activation patterns for all 8 muscles. In the leg-propulsion phase, there was less triceps brachii activation (1 swimmer 6% vs median 23.0% [8.8]). In the leg-glide phase, there was activation in rectus femoris and gastrocnemius during the beginning of this phase (all world-class vs only 1 national elite) and a longer activation in pectoralis major (world champions 71% [0.5] vs 50.0 [4.3]) (propulsive phase of the arms). In the leg-recovery phase, there was more activation in biceps femoris (50.0% [15.0] vs 20.0% [14.0]) and a later and quicker activation in tibialis anterior (40.0% [7.8] vs 52.0% [6.0]). In the stroke cycle, there was no coactivation in tibialis anterior and gastrocnemius for world champions.Conclusion:These components are important performance discriminants. They can be used to improve muscle-activation patterns and kinematics through the different breaststroke phases. Furthermore, they can be used as focus points for teaching breaststroke to beginners.

Research in physiology and sports science has shown that fatigue, a complex psychophysiological phenomenon, has a relevant impact in performance and in the correct functioning of our motricity system, potentially being a cause of damage to the human organism. Fatigue can be seen as a subjective or objective phenomenon. Subjective fatigue corresponds to a mental and cognitive event, while fatigue referred as objective is a physical phenomenon. Despite the fact that subjective fatigue is often undervalued, only a physically and mentally healthy athlete is able to achieve top performance in a discipline. Therefore, we argue that physical training programs should address the preventive assessment of both subjective and objective fatigue mechanisms in order to minimize the risk of injuries. In this context, our paper presents a machine-learning system capable of extracting individual fatigue descriptors (IFDs) from electromyographic (EMG) and heart rate variability (HRV) measurements. Our novel approach, using two types of biosignals so that a global (mental and physical) fatigue assessment is taken into account, reflects the onset of fatigue by implementing a combination of a dimensionless (0-1) global fatigue descriptor (GFD) and a support vector machine (SVM) classifier. The system, based on 9 main combined features, achieves fatigue regime classification performances of0.82±0.24, ensuring a successful preventive assessment when dangerous fatigue levels are reached. Training data were acquired in a constant work rate test (executed by 14 subjects using a cycloergometry device), where the variable under study (fatigue) gradually increased until the volunteer reached an objective exhaustion state.

International audience; ObjectivesNeurodynamic techniques are often used to treat people with sciatica pain, but their mechanical effects on the sciatic nerve are unknown. Shear wave elastography (SWE) has been shown to effectively estimate the stiffness of peripheral nerves in real time. The aim of this study was to use SWE to assess the effects of slump neurodynamics in the sciatic stiffness of people with sciatica.MethodsSixteen participants volunteered for this study. The sciatic stiffness of 8 patients with unilateral chronic sciatica and 8 healthy control participants was measured by SWE, with the participants in a prone position and during a dynamic condition (ie, ankle dorsiflexion). These measurements were performed before and immediately after the neurodynamic intervention, which consisted of a static slump position applied to the symptomatic limb of the patients with sciatica and in a randomly chosen limb of the healthy participants.ResultsThe 8 patients with sciatica included 6 male and 2 female patients, and the 8 healthy control participants included 5 male and 3 female volunteers. Slump neurodynamics resulted in an immediate decrease in the sciatic nerve stiffness of the symptomatic limb in people with sciatica by 16.1% (effect size = 0.65; P = .019). The intervention showed no significant changes in the sciatic nerve stiffness of the healthy participants (effect size = 0.05; P = .754).ConclusionsSlump neurodynamics have the potential of decreasing the sciatic nerve stiffness in people with sciatica, and this effect can be quantified by SWE, which may provide valuable information for health professionals.

Dynamic knee valgus is a multi-planar motion that has been associated with anterior cruciate ligament injuries and patellofemoral pain syndrome. Clinical assessment of dynamic knee valgus is usually performed through visual appearance of medial knee displacement (MKD) during the overhead squat. The aim of this study is to identify the kinematic and neuromuscular parameters associated with MKD. Twenty-two females performed an overhead squat and were assigned to the control group (n = 14) or the MKD group (n = 8). Electromyography and kinematic data of the lower extremity were collected. We observed MKD to exhibit greater muscle activity in the following muscles: adductor magnus, biceps femoris, vastus lateralis and vastus medialis muscles during the eccentric phase of the overhead squat. No group differences were observed during the concentric phase. Regarding the kinematics, the MKD group showed higher knee internal rotation and, knee abduction and ankle abduction, compared to controls. The combined information from the muscle activity results and kinematics of squat helps to explain the occurrence of excessive medial knee displacement and, hence, providing relevant information for health professionals to address this injury risk factor.

BACKGROUND: Older persons are the fastest growing segment of the population living in the Western hemisphere. Longevity comes at a price, including a higher rate of morbidity, functional and mental disability and the eventual loss of independence. Physical inactivity further aggravates the decline in physiological function along the aging process. Therefore, the promotion of regular exercise may be seen as one of the main non-pharmacological approaches that should be recommended to older adults. METHODS: We performed a comprehensive review on the interaction between exercise training and improved physical fitness in the elderly. Specifically, 175 papers describing the overall benefits of exercise training on the cardiovascular, neuromuscular and brain function of older adults were included. The effectiveness of training for improving quality of life at an older age was also reviewed. RESULTS: Exercise training can partially reverse the age-related physiological decline and enhance work capacity in the elderly. Numerous studies have shown that maintaining a minimum quantity and quality of physical exercise decreases the risk of cardiovascular mortality, sarcopenia, prevents the onset of osteopenia and even exerts a prophylactic role against neurodegeneration. The systemic physiologic effects are profound and may be directly linked to a favorable feedforward cycle whereby improved physiologic function begets improved physical function and so on. CONCLUSION: We conclude that structured training programs should be designed to improve the physiological function in this population. Finally, the benefits of exercise training vary as a function of training volume and this relationship is independent of age and sex. info:eu-repo/semantics/publishedVersion

The aim of this study was to compare the electromyographic patterns of the lower limb muscles during a golf swing performed by low- and high-handicap golfers.Ten golfers (5 low- and 5 high-handicap) performed 8 swings using a 7-iron. Surface electromyography (EMG) was recorded for the following lower limb muscles on both sides: biceps femoris, semitendinosus, gluteus maximus, vastus medialis and lateralis, rectus femoris, tibialis anterior, peroneus longus, and gastrocnemius medialis and lateralis. The golf-swing phases were determined by 3-dimensional high-speed video analysis.Compared with the high-handicap golfers, the low-handicap golfers performed the forward swing with a shorter duration of the swing phases, with the exception of the late follow-through, where they exhibited longer duration. Considering the EMG patterns, the low-handicap golfers showed a tendency for the studied muscles to reach an activation peak earlier and presented statistically significant higher muscle activity in some of the lower limb muscles, mainly from the left side.Differences between low- and high-handicap golfers were found in the average duration of swing phases and in the activation level of the lower limbs, with more evidence on muscles from the left side.

Objectives To analyze differences in trunk endurance time, fatigue and activation in tennis players with and without low back pain. Design Observational study, cross-sectional design. Methods Thirty-five tennis players completed an isometric trunk endurance protocol comprising four tasks (flexor, extensor and side bridge tests). LBP history was obtained through the Nordic Musculoskeletal Questionnaire. Endurance time was recorded for each test. Surface electromyographic activity was recorded bilaterally from rectus abdominis, external obliques, iliocostalis lumborum and longissimus thoracis. Average electromyographic amplitude and median frequency slopes during the tests were calculated and used as indicators of change in muscle activation and fatigue. Results Asymptomatic players had greater flexor (p = 0.004) and right side bridge (p = 0.043) endurance times. These players produced a greater increase in avrEMG during the right side bridge test for the left ES-I (p = 0.046) and right EO (p = 0.008). Players with LBP in the last 7 days showed reduced activation of the left (p = 0.014) and right (p = 0.013) ES-I and left longissimus thoracis (ES-L, p = 0.047) in the extensor test. In the left side bridge test there was a lower avrEMG slope of the left EO (p = 0.024) and left RA MF slope (p = 0.011). In the right side bridge test a lower left ES-I avrEMG slope was found (p = 0.048). Conclusions Symptomatic players show lower activation of extensor muscles, less co-contraction patterns and less abdominal endurance. Tennis coaches and clinicians should consider these factors in their approach to players with LBP.

Typically, gait rehabilitation uses an invariant stimulus paradigm to improve gait related deficiencies. However, this approach may not be optimal as it does not incorporate gait complexity, or in more precise words, the variable fractal-like nature found in the gait fluctuations commonly observed in healthy populations. Aging which also affects gait complexity, resulting in a loss of adaptability to the surrounding environment, could benefit from gait rehabilitation that incorporates a variable fractal-like stimulus paradigm. Therefore, the present study aimed to investigate the effect of a variable fractal-like visual stimulus on the stride-to-stride fluctuations of older adults during overground walking. Additionally, our study aimed to investigate potential retention effects by instructing the participants to continue walking after turning off the stimulus. Older adults walked 8 min with i) no stimulus (self-paced), ii) a variable fractal-like visual stimulus and iii) an invariant visual stimulus. In the two visual stimuli conditions, the participants walked 8 additional minutes after the stimulus was turned off. Gait complexity was evaluated with the widely used fractal scaling exponent calculated through the detrended fluctuation analysis of the stride time intervals. We found a significant ~20% increase in the scaling exponent from the no stimulus to the variable fractal-like stimulus condition. However, no differences were found when the older adults walked to the invariant stimulus. The observed increase was towards the values found in the past to characterize healthy young adults. We have also observed that these positive effects were retained even when the stimulus was turned off for the fractal condition, practically, acutely restoring gait complexity of older adults. These very promising results should motivate researchers and clinicians to perform clinical trials in order to investigate the potential of visual variable fractal-like stimulus for gait rehabilitation.

Muscle synergy extraction has been utilized to investigate muscle coordination in human movement, namely in sports. The reliability of the method has been proposed, although it has not been assessed previously during a complex sportive task. Therefore, the aim of the study was to evaluate intra- and inter-day reliability of a strength training complex task, the power clean, assessing participants&rsquo, variability in the task across sets and days. Twelve unexperienced participants performed four sets of power cleans in two test days after strength tests, and muscle synergies were extracted from electromyography (EMG) data of 16 muscles. Three muscle synergies accounted for almost 90% of variance accounted for (VAF) across sets and days. Intra-day VAF, muscle synergy vectors, synergy activation coefficients and individual EMG profiles showed high similarity values. Inter-day muscle synergy vectors had moderate similarity, while the variables regarding temporal activation were still strongly related. The present findings revealed that the muscle synergies extracted during the power clean remained stable across sets and days in unexperienced participants. Thus, the mathematical procedure for the extraction of muscle synergies through nonnegative matrix factorization (NMF) may be considered a reliable method to study muscle coordination adaptations from muscle strength programs.

This study sought to examine the shear modulus (i.e., an force index) of three quadriceps muscles [i.e., vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF)] during passive stretching to determine whether epimuscular myofascial force transmission occurs across muscles. Secondly, this study compared the shear modulus between the quadriceps muscles, in both proximal and distal regions. Twelve healthy individuals were assessed during a passive knee flexion maneuver between 0 and 90 of knee flexion with the hip in two positions: flexed (80 ) vs. neutral (0 ). Muscle electrical activity was also assessed during the testing. No differences were observed between the hip testing positions for myoelectric activity (p > 0.43), and for VL and VM shear modulus (p = 0.12–0.98). Similarly, there were no differences between the proximal and distal regions for all muscles (p = 0.42–0.93). RF showed a higher shear modulus with the hip in the neutral position (p = 0.004). With the hip flexed, the VL showed the greatest shear modulus among the tested muscles (p < 0.025); while with the hip in the neutral position, no differences were observed for shear modulus between VL and RF (p = 0.817). These findings suggest that epimuscular myofascial force transmission (at a muscle belly level) does not occur between the quadriceps muscles when passively flexing the knee until 90 . Whether epimuscular myofascial force transmission occurs in the quadriceps muscles bellies with greater muscle stretch (either through knee flexion or hip extension) remains to be examined. info:eu-repo/semantics/publishedVersion

Purpose To assess the stiffness of hamstring muscles during isometric contractions in healthy individuals, using ultrasoundbased shear wave elastography to (1) determine the intra- and inter-day assessment repeatability, (2) characterize the stiffness of semitendinosus (ST) and biceps femoris long head (BFlh) along the contraction intensity, and (3) characterize stiffness distribution among the hamstring muscles and inter-limb symmetry. Methods Two experiments were conducted. In experiment I (n = 12), the intra-day repeatability in assessing the BFlh and ST stiffness were determined at intensities between 10–60% of maximal voluntary isometric contraction (MVIC) in a single session. In experiment II (n = 11), the stiffness of the hamstring muscles of both thighs was assessed at 20% of MVIC in the first session; and retested (for one randomly chosen thigh) in a second session. Isometric contraction of knee flexors was performed with the knee flexed at 30° and with the hip in a neutral position. Results Moderate-to-very-high intra- and inter-day repeatability was found (ICC = 0.69–0.93). The BFlh/ST stiffness ratio increased with contraction intensity. At 20% of MVIC, the ST showed the highest stiffness among the hamstring muscles (p < 0.02), with no differences between the remaining hamstring muscles (p > 0.474). No differences were found between limbs (p = 0.12). Conclusions The stiffness distribution among the hamstring muscles during submaximal isometric contractions is heterogeneous, but symmetric between limbs, and changes depending on the contraction intensity. Shear wave elastography is a reliable tool to assess the stiffness of hamstring muscles during contraction. info:eu-repo/semantics/publishedVersion

BACKGROUND: The University of Western Ontario Questionnaire for Musculoskeletal Conditions in Senior Golfers (MSK Golfers) was developed in Canada because of a lack of knowledge concerning musculoskeletal conditions directly related to golf play and warm-up, although the high injury incidence in golf practice. This lack of epidemiological measures also exists for the Portuguese golf population. OBJECTIVE: The purpose of this study was to translate and cross-culturally adapt the MSK Golfers questionnaire into Portuguese and to test its construct validity and reproducibility. METHODS: The MSK Golfers was translated from English to Portuguese and tested for psychometric properties. Sixty-one golfers, aged between 14 and 70 years and with at least 1 year of practice in golf, were recruited. The validity of the MSK Golfers was assessed by evaluating data quality (missing, floor and ceiling effects). Reproducibility analysis included intra-class correlation coefficients (ICC) (2,1) and Cohen's Kappa coefficient. RESULTS: The ICC values for continuous items ranged from 0.634 to 0.998 with the exception of one item on golf activity. Kappa statistics for the categorical items ranged between 0.714 and 1.00. CONCLUSIONS: The Portuguese version of the MSK Golfers, including playing characteristics and warm-up patterns of golfers, showed a high reliability for a golfing population with an age range of 14 to 70 years.

Static stretching with rest between repetitions is often performed to acutely increase joint flexibility.Purpose:To test the effects of the lack of resting between stretching repetitions and the minimal number of stretching repetitions required to change the maximal range of motion (ROM), maximal tolerated joint passive torque (MPT), and submaximal passive torque at a given angle (PT).Methods:Five static stretching repetitions with a 30-s rest-interval (RI) and a no-rest-interval (NRI) stretching protocol were compared. Participants (N = 47) were encouraged to perform the maximal ROM without pain in all the repetitions. Each repetition lasted 90 s. Maximal ROM, MPT, PT, and muscle activity were compared between protocols for the same number of stretching repetitions.Results:The NRI produced a higher increase in maximal ROM and MPT during and after stretching (P < .05). PT decreased in both protocols, although the NRI tended to have a lower decrement across different submaximal angles (.05 < P < .08) in the initial range of the torque-angle curve. Significant changes in maximal ROM (P < .01) and PT (P < .01) were obtained at the 3rd and 2nd repetitions of RI, respectively. The RI did not significantly increase the MPT (P = .12) after stretching; only the NRI did (P < .01).Conclusions:Lack of rest between repetitions more efficiently increased the maximal ROM and capacity to tolerate PT during and after stretching. The use of 30 s rest between repetitions potentiates the decrease in PT. Rest intervals should not be used if the aim is to acutely increase maximal ROM and peak passive torque.

This study determined the influence of walking with blood flow restriction (BFR) on the excess post-exercise oxygen consumption (EPOC) of healthy young men. 17 healthy young men (22.1±2.9 years) performed graded treadmill exercise to assess VO2peak. In a randomized fashion, each participant performed 5 sets of 3-min treadmill exercise at their optimal walking speed with 1-min interval either with or without BFR. Participants were then seated in a chair and remained there for 30 min of recovery. Expired gases were continuously monitored during exercise and recovery. BFR increased the O2 cost of walking as well as its relative intensity and cumulative O2 deficit (p0.05). These data indicate that walking with BFR increases the magnitude of EPOC. Moreover, they also demonstrate that such increment in EPOC is likely explained by the effects of BFR on walking relative intensity and cumulative O2 deficit.

Background: Modeling physiological signals is a complex task both for understanding and synthesize biomedical signals. We propose a deep neural network model that learns and synthesizes biosignals, validated by the morphological equivalence of the original ones. This research could lead the creation of novel algorithms for signal reconstruction in heavily noisy data and source detection in biomedical engineering field. Method: The present work explores the gated recurrent units (GRU) employed in the training of respiration (RESP), electromyograms (EMG) and electrocardiograms (ECG). Each signal is pre-processed, segmented and quantized in a specific number of classes, corresponding to the amplitude of each sample and fed to the model, which is composed by an embedded matrix, three GRU blocks and a softmax function. This network is trained by adjusting its internal parameters, acquiring the representation of the abstract notion of the next value based on the previous ones. The simulated signal was generated by forecasting a random value and re-feeding itself. Results and conclusions: The resulting generated signals are similar with the morphological expression of the originals. During the learning process, after a set of iterations, the model starts to grasp the basic morphological characteristics of the signal and later their cyclic characteristics. After training, these models' prediction are closer to the signals that trained them, specially the RESP and ECG. This synthesis mechanism has shown relevant results that inspire the use to characterize signals from other physiological sources. publishersversion published