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- Effects of attentional focus on torque regulation and muscle activation in acute anterior cruciate ligament injured individualsPublication . Filipe, Hugo Manuel dos Santos; Vaz, João Pedro Casaca de RochaAttentional focus has been extensively studied in the context of motor learning, demonstrating a significant influence on movement execution and control. However, its effects in populations with anterior cruciate ligament (ACL) injury, particularly regarding torque variability and muscle activation, remain underexplored. This study aimed to examine the effects of different attentional focus strategies (internal vs. external) on torque production and electromyographic activity in athletes with ACL injuries. Eleven participants with ACL injuries performed submaximal isometric knee contractions under internal or external focus instructions, using an isokinetic dynamometer. Variables such as sample entropy (SampEn), torque coefficient of variation (CV), co-contraction index (CCI), and electromyographic activity of the vastus lateralis and biceps femoris were analyzed. Results revealed no statistically significant differences in torque variability between conditions; however, higher levels of co-contraction and hamstring activation were observed under the external focus condition. These findings suggest that attentional focus may modulate motor control patterns in individuals with ACL injuries by influencing neuromuscular compensation strategies throughout rehabilitation. Thoughtful implementation of attentional focus instructions may serve as a valuable component in the optimization of exercise-based rehabilitation protocols.
- The effects of neck pain on postural control variability in dental medicine students : a longitudinal studyPublication . Vieira, Sofia de Oliveira; Almeida, Manuel João Videira da Silva Barbosa deNeck pain is a common complaint among dental medicine students, resulting from sustained postures during clinical practice and potentially compromising postural control. However, the longitudinal effects of neck pain on postural control variability remain underexplored. This study aimed to analyze how the presence of neck pain influences postural control variability in dental medicine students over the course of three semesters of clinical training. Forty-four students initially participated in the study and were divided into two groups— with and without neck pain—based on the Nordic Musculoskeletal Questionnaire. Postural control was assessed using a force platform across eight distinct postural conditions, considering both anteroposterior and mediolateral components. Postural control variability was quantified using SampEn, calculated via a customized MATLAB script. Data were analyzed through a linear mixed-effects model, with fixed factors including group, time, postural position, cervical rotation, and visual condition. Results revealed that, over time, the neck pain group showed a progressive reduction in postural variability, reflecting a more rigid control pattern, especially under more demanding tasks such as tandem stance with eyes closed. These findings suggest that neck pain negatively affects the students’ ability to adapt posturally, highlighting the need for preventive strategies in academic and clinical settings.
- The effect of focus of attention during a single bout of resistance exercise on plantarflexion torque complexity and cortical drive in older adults : a randomized controlled trialPublication . Marques, Tiago José Santos; Vaz, João Pedro Casaca de RochaIntroduction: Ageing is accompanied by impairments in neuromuscular function, contributing to reduced force control, increased muscle co-contraction during gait, and diminished adaptability, ultimately increasing the risk of falling. Resistance training and attentional focus strategies have independently been proposed as potential modulators of these deficits, yet their combined effect remains unclear, especially in older adults. The present study investigated how different attentional focus instructions during a single bout of plantarflexion resistance training influence force control and the underlying neurophysiological mechanisms in this population. Methods: 23 participants (≥ 60 years old) were screened and homogeneously randomized into internal, external, or visual (distal) external focus groups after a familiarization session. In the evaluation session, neuromuscular and cortical drive measures were obtained before and after a single standardized seated calf raise resistance training bout. Results: No group-related differences were observed. However, acute pre- to post-training effects emerged across all groups, including reduced maximal force production, increased torque variability (coefficient of variation), and decreased corticospinal inhibition. Torque complexity and intracortical measures remained unchanged. Conclusion: These findings suggest that attentional focus strategies applied during a single resistance training session are not sufficient to modify force control or cortical mechanisms in older adults. Nonetheless, the observed neuromuscular fatigue and corticospinal modulation highlight this population’s acute adaptations to a single resistance training session.
- Associação entre potência muscular mensuradas em diferentes testes de sentar e levantar e a variabilidade do torque em indivíduos idosos : estudo correlacionalPublication . Espadilha, Ana Patrícia dos Santos Pinheiro; Radaelli, RégisIntrodução: A potência dos membros inferiores, avaliada pelo teste de sentar e levantar (STS), e a variabilidade do torque são preditores sensíveis da funcionalidade em idosos. Porém, a relação entre eles em idosos é pouco conhecida. Métodos: Este estudo teve como objetivo analisar a relação entre a potência muscular, mensurada por diferentes testes de STS, e a variabilidade do torque em indivíduos idosos. Neste estudo participaram 38 homens e mulheres idosos saudáveis. Foram mensuradas a contração isométrica máxima dos extensores do joelho num dinamómetro isocinético, e posteriormente mensurada a variabilidade do torque. A potência muscular durante a execução dos testes de STS foi avaliada a partir de três diferentes métodos: com encoder, na plataforma de força e por fórmula. Os participantes realizaram os testes de STS na plataforma de força e com o encoder com repetições lentas e rápidas, enquanto para o cálculo a partir da fórmula os praticantes realizaram o maior número de repetições de sentar e levantar em 30 segundos. Resultados: Foram encontradas correlações significativas positivas entre a variabilidade do torque e a potência absoluta e relativa, medida pelo encoder (R² ≈ 0,17– 0,39; p < 0,001), quando o teste de STS foi executado de maneira lenta e rápida. Também, foi observada corelação significativa entre a variabilidade do torque e a potência avaliada na plataforma de força de forma lenta (R² ≈ 0,12; p < 0,001). Por fim, também foi encontrado correlação significativa entre a variabilidade e a potência obtida pela fórmula (R² ≈ 0,39; p < 0,001). Conclusão: A potência muscular avaliada por diferentes testes de STS, mostraram correlação moderadas e significativas com a variabilidade do torque. Também, sugerem uma maior sensibilidade da relação entre a variabilidade e a potência muscular nos STS avaliada pelo encoder e pela fórmula.
- Prevalência das disfunções do pavimento pélvico, e o efeito que o tempo de treino e modalidade tem no pavimento pélvico das atletas de desportos aquáticos : estudo surveyPublication . Madeira, Ana Rita Boné; Vicente, SóniaIntrodução: A disfunção do pavimento pélvico (DPP) compreende um conjunto de sinais, sintomas e condições que afetam o pavimento pélvico, sendo reconhecida como um problema prevalente entre atletas do sexo feminino, diminuindo a sua qualidade de vida e podendo levar ao abandono da prática desportiva. Objetivo: Avaliar a prevalência das DPP em atletas de modalidades aquáticas e analisar o impacto do tempo de treino e modalidade na função do pavimento pélvico. Métodos: Estudo observacional, transversal, tipo survey, com uma amostra de 55 atletas femininas. As atletas preencheram um questionário composto por duas partes: a primeira para a caracterização da amostra, e a segunda para a avaliação das alterações do pavimento pélvico e do tempo de prática das atletas, com recurso a três instrumentos validados para a população portuguesa (ICIQSF; Australian Pelvic Floor Questionnaire; IPAQ). Resultados: A prevalência global de DPP foi de 45,2 %, com maior incidência nas modalidades de crawl e mariposa. Observou-se uma associação entre modalidades tecnicamente mais exigentes e maior prevalência de sintomas; contudo, não se verificou uma correlação significativa entre a carga horária semanal média (< 8 h) e a gravidade das DPP. Foram igualmente reportados sintomas nos domínios intestinal e sexual, sendo que a maioria das atletas referiu um impacto reduzido no seu quotidiano. Conclusão: As DPP são prevalentes em atletas de modalidades aquáticas, sobretudo em modalidades de maior exigência técnica, confirmando a natureza multifatorial destas disfunções. A ausência de associação com a carga horária sugere o contributo de outros fatores individuais e biomecânicos, reforçando a importância de maior sensibilização, avaliação sistemática e investigação dirigida nesta população.
- Variability of ground reaction forces between lower limbs during running in male and female rugby players after hamstrings injury : a cross-sectional studyPublication . Marques, Nuno Miguel Toureiro; Oliveira, Paulo Ricardo Miranda; Fernandes, Orlando de Jesus Semedo MendesHamstring injuries are among the most common in rugby, frequently affecting athletic performance due to their influence on lower limb biomechanics. This cross-sectional observational study aimed to evaluate the temporal structure of ground reaction force (GRF) variability between injured and uninjured lower limbs in rugby players with a history of unilateral hamstring injury. Using Detrended Fluctuation Analysis (DFA), the study assessed the temporal structure of motor variability during treadmill running in a sample of 20 athletes (95% male). The DFA alpha values for injured limbs (M = 0.735) and uninjured limbs (M = 0.706) indicated persistent correlations within a functional range (0.5 < α < 1.0), with no statistically significant differences between limbs (p = 0.317). However, a slight trend toward increased motor rigidity in the injured limb was noted, potentially reflecting compensatory adaptations. DFA emerged as a sensitive tool capable of detecting subtle changes in motor control that may not be captured by conventional biomechanical analyses. Limitations included the small sample size, gender imbalance, and treadmill-only testing, which constrain generalizability. Nonetheless, the results highlight the potential of DFA as a valuable adjunct in return-to-play assessments and injury prevention protocols. Future research should adopt longitudinal designs and recruit more diverse samples valid settings to fully explore DFA diagnostic and rehabilitative applications in sports performance.
- Comparison of ground reaction force variability between sprint athletes with and without hamstring injury history : a cross-sectional studyPublication . Feliciano, Margarida Nobre; Oliveira, Paulo Ricardo Miranda; Fernandes, Orlando de Jesus Semedo MendesSprint running exposes the hamstring muscles to high mechanical loads, particularly during the late swing and early stance phases, which are recognized as critical periods of elevated injury risk for this muscle group. In sprinters with a history of hamstring injury (W/HHI), alterations in vertical ground reaction force (vGRF) variability may persist even after rehabilitation, reflecting potential neuromuscular adaptations or constraints. Determining whether this variability falls within a functional range is essential, as both excessive rigidity and instability can compromise performance and increase the risk of reinjury. In this cross-sectional study, 17 sprinters (7 W/HHI, 10 WO/HHI) performed a 60-second submaximal sprint on an instrumented treadmill. VGRF variability was assessed using Sample Entropy (SaEn) and analysis of the force–time relationship (log-log slope). The W/HHI group presented lower mean log-log slope values (0.175 ± 0.342; range from -0.417 to 0.627) compared to the WO/HHI group (0.497 ± 0.546; range from -0.137 to 1.875), although this difference did not reach statistical significance (p = 0.195). A tendency toward lower SaEn values was also observed in the W/HHI group (SaEn_Force: 1.80 ± 0.433 vs. 2.16 ± 0.402; p = 0.103; SaEn_Time: 2.26 ± 0.382 vs. 2.50 ± 0.337; p = 0.219), suggesting distinct motor control profiles. In the W/HHI group, greater variability in force did not compromise responsiveness, which may reflect compensatory motor reorganizations. By contrast, the WO/HHI group demonstrated greater robustness in the force–time relationship but also signs of force instability that appeared to be counterbalanced by temporal variability. These findings underscore the relevance of assessing the temporal structure of vGRF variability in sprinters, as it allows the identification of trends in motor adaptation and reorganization associated with injury history. Moreover, they highlight the importance of integrating neuromuscular re-education programs into physiotherapy and prevention protocols, with the aim of re-establishing functional variability specific to the demands of sprinting, thereby promoting a safe return to performance, optimizing performance and reducing reinjury risk.
- Comparison of acute cortical drive responses in scapular muscles after scapular-oriented exercises with electromyographic biofeedback or verbal and tactile feedback in healthy young adults : a randomized controlled trialPublication . Ferreira, João Francisco Santos; Neto, Carla MartinhoIntroduction: The scapular muscles are vital for movement and scapulohumeral rhythm. Electromyographic biofeedback and other feedback modalities are effective in enhancing electromyographic activity and motor control. Transcranial Magnetic Stimulation (TMS) assesses cortical plasticity, linking motor adaptations to the corticospinal system. A gap remains in the understanding of the role of cortical reorganization in mediating the effects of Electromyographic biofeedback on motor learning. This study compared the acute cortical drive responses in scapular muscles following exercises with Electromyographic biofeedback or verbal and tactile feedback in healthy young adults, hypothesizing greater responses with Electromyographic biofeedback. Methods: Twelve healthy young adults (aged 18–35) were recruited, all shoulder pain free and with no contraindications to TMS. Participants were randomized into two groups: TMS + Electromyographic biofeedback (BEMG) (n = 5) and TMS + Verbal/Tactile Feedback (AT) (n = 7). Both groups performed a single 30-minute exercise session focused on scapulothoracic muscles. Cortical drive was assessed via TMS, including Corticospinal Excitability (CSE), Silent Period (SP), and Short-Interval Intracortical Inhibition (SICI) of the Upper (UT) and Lower Trapezius (LT) muscles. Results: No significant differences were observed between groups in CSE or SP for either UT or LT. However, a statistically significant difference was found in the percentage change of UT SICI, with the AT group (verbal/tactile feedback) showing a substantially greater increase (mean difference = −64.89%; Cohen’s d = -1.325). For the LT, changes in SP showed a large effect size in favor of the AT group, although not statistically significant. Conclusion: Verbal and Tactile feedback may be effective strategies during the initial phases of scapulothoracic muscle strengthening, potentially facilitating motor learning more efficiently than visual feedback. The SICI results for the UT suggest distinct neuromodulator effects between feedback modalities. These findings should be interpreted with caution due to the small sample size (n = 12) and other methodological limitations. Future studies with larger samples and longer interventions are recommended.
- The association between muscle power and gait complexity in apparently healthy older adults : a correlational studyPublication . Ferreira, Filipa Cristina Luís; Vaz, João Pedro Casaca de RochaThis study explores the relationship between two established biomarkers of age-related functional decline: muscle power and gait complexity. Both are considered robust indicators of motor control decline, appearing before manifestations of age-related changes 1–4, but their interrelation remains unclear. We hypothesized a positive correlation between lower limb muscle power and gait complexity in healthy older adults. In this cross-sectional study, 28 participants aged 60 and above were analysed. Muscle power was assessed through a sit-to-stand task using a Bertec force plate, while gait complexity was measured during a 12-minute treadmill walk with a Bertec treadmill and custom MATLAB code. Correlation analyses showed no significant associations between muscle power (PRF/BW, RFD30/w, RFD100/w) and gait complexity (fractal scaling exponent α, or CV), with all coefficients low and p-values > 0.05. These findings suggest that, although both are early indicators of neuromuscular decline, muscle power and gait complexity may reflect distinct motor control mechanisms. Nevertheless, both remain valuable and complementary markers of functional aging.
- Comparison of cortical drive and muscle power in older adults with and without fear of falling : a comparative cross-sectional studyPublication . Sousa, Laís Karielly Rodrigues de; Radaelli, RégisIntroduction: Fear of falling (FoF) is a psychological factor that contributes to physical inactivity, social withdrawal, and increased fall risk. Previous evidence suggests age-related changes in cortical drive and muscle power. However, there is a lack of knowledge on how these changes affect FoF. This study aimed to compare corticospinal excitability (CSE), short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), silent period (SP) and lower-limb muscle power between older adults with and without FoF. Methods: Eighteen communitydwelling older adults (g65 years old) participated and were classified into two groups based on the Falls Efficacy Scale International (FES-I): NFoF (score <28; n=10) and FoF (score g28; n=8). Cortical drive was assessed using Transcranial Magnetic Stimulation (TMS), with measures of active motor threshold (AMT), CSE, SICI, ICF. Lower-limb muscle power was measured via countermovement jump on a force platform. Physical activity levels were evaluated using the IPAQ-short form. Results: Groups were similar in age, BMI, and height. Participants with FoF had significantly more falls in the past 12 months (p=0.006). No statistically significant differences were found between groups for AMT (p=0.864), CSE (p=0.565), ICF (p=0.999), SICI (p=0.355) or SP (p=0.667). Physical activity levels did not differ significantly between older adults with and without FoF (p=0.342; §= 0.325). No statistically significant differences were found in absolute or relative muscle power between groups (p=0.141; d=0.735 and p=0.150; d=0.717, respectively). Conclusion: The FoF does not appear to influence neurophysiological parameters or lower-limb muscle power in this sample of older adults.