Percorrer por autor "Alves, Leonel"
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- Electromyographic assessment of agonist and antagonist muscles related to the anterior cruciate ligament following surgical reconstruction: A cross-sectional studyPublication . Paredes, Ricardo; Pereira, Soraia; Crasto, Carlos; Guedes, Diana; Montes, António Mesquita; Alves, Leonel; Arias-Buría, José L.; C. Guedes, Diana; Mesquita Montes, AntónioFollowing anterior cruciate ligament reconstruction (ACLR), neuromuscular control alterations may persist, increasing the risk of reinjury. This study aimed to investigate electromyographic (EMG) muscle activation and the co-contraction index (CCI) of ACL-related agonist and antagonist muscles during side- hop tasks in ACLR individuals, offering novel insights into neuromuscular strategies during dynamic tasks. A cross-sectional study was conducted with 15 ACLR individuals and 15 participants without ACL injury (N-ACLR). Participants performed side-hop tasks while kinematic, kinetic, and EMG data were recorded during the preparatory and loading phases. Statistical analyses were performed at a 95 % confidence level. During ipsilateral side hops, ACLR individuals exhibited higher semitendinosus (ST) activity in the initial contact (IC) and risk phases and increased quadriceps:hamstrings (Q:H) CCI in the risk phase compared to N-ACLR (p < 0.05). In contralateral side hops, ACLR individuals demonstrated higher Q:H CCI in the preparatory phase and higher vastus lateralis:biceps femoris (VL:BF) CCI in the IC and risk phases (p < 0.05). ACLR individuals display altered neuromuscular strategies during side-hop tasks compared to N-ACLR, highlighting adaptations in muscle activation and co-contraction patterns.
- Neurobiomechanical characterization of feedforward phase of gait initiation in chronic stroke: A linear and non-linear approachPublication . Freitas, Marta; Fonseca, Pedro; Alves, Leonel; Pinho, Liliana; Silva, Sandra; Figueira, Vânia; Félix, José; Pinho, Francisco; Vilas-Boas, João Paulo; Silva, Augusta; Ferreira Silva, Maria AugustaPostural control arises from the complex interplay of stability, adaptability, and dynamic adjustments, which are disrupted post-stroke, emphasizing the importance of examining these mechanisms during functional tasks. This study aimed to analyze the complexity and variability of postural control in post-stroke individuals during the feedforward phase of gait initiation. A cross-sectional study analyzed 17 post-stroke individuals and 16 matched controls. Participants had a unilateral ischemic stroke in the chronic phase and could walk independently. Exclusions included cognitive impairments, recent surgery, and neurological/orthopedic conditions. Kinematic and kinetic data were collected during 10 self-initiated gait trials to analyze centre of pressure (CoP) dynamics and joint angles (−600 ms to +50 ms). A 12-camera motion capture system (Qualisys, Gothenburg, Sweden) recorded full-body kinematics using 72 reflective markers placed on anatomical landmarks of the lower limbs, pelvis, trunk, and upper limbs. Ground reaction forces were measured via force plates (Bertec, Columbus, OH, USA) to compute CoP variables. Linear (displacement, amplitude, and velocity) and non-linear (Lyapunov exponent—LyE and multiscale entropy—MSE) measures were applied to assess postural control complexity and variability. Mann–Whitney U tests were applied (p < 0.05). The stroke group showed greater CoP displacement (p < 0.05) and reduced velocity (p = 0.021). Non-linear analysis indicated lower LyE values and reduced complexity and adaptability in CoP position and amplitude across scales (p < 0.05). In the sagittal plane, the stroke group had higher displacement and amplitude in the head, trunk, pelvis, and limbs, with reduced LyE and MSE values (p < 0.05). Frontal plane findings showed increased displacement and amplitude in the head, trunk, and ankle, with reduced LyE and MSE (p < 0.05). In the transverse plane, exaggerated rotational patterns were observed with increased displacement and amplitude in the head, trunk, pelvis, and hip, alongside reduced LyE convergence and MSE complexity (p < 0.05). Stroke survivors exhibit increased linear variability, indicating instability, and reduced non-linear complexity, reflecting limited adaptability. These results highlight the need for rehabilitation strategies that address both stability and adaptability across time scales.