Browsing by Author "Martinez-Valdes, Eduardo"

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    Changes in the ankle muscles co-activation pattern after 5 years following total ankle joint replacement
    (2018) De la Fuente, Carlos; Martinez-Valdes, Eduardo; Cruz-Montecinos, Carlos; Guzman-Venegas, Rodrigo; Arriagada, David; Pena y Lillo, Roberto; Henriquez, Hugo; Carpes, Felipe P.
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    Distal overactivation of gastrocnemius medialis in persistent plantarflexion weakness following Achilles tendon repair
    (2023) Fuente, Carlos De la; Martinez-Valdes, Eduardo; Rocha, Emmanuel S. da; Geremia, Jeam M.; Vaz, Marco A.; Carpes, Felipe P.
    Structural alterations of the triceps surae and Achilles tendon (AT) can promote plantarflexion weakness one-year following an AT repair, influencing the activation strategies of the Gastrocnemius Medialis (GM) muscle. However, this is yet to be demonstrated. We aimed to determine whether patients with plantar flexion weakness one-year after AT repair show altered GM spatial activation. In this cross-sectional and case-control study, ten middle-aged men (age 34 +/- 7 years old, and 12.9 +/- 1.1 months post-surgery) with a high AT total rupture score who attended conventional physiotherapy for six months after surgery, and ten healthy control men (age 28 +/- 9 years old), performed maximal and submaximal (40, 60 and 90%) voluntary isometric plantarflexion contrac-tions on a dynamometer. The peak plantar flexor torque was determined by isokinetic dynamometry and the GM neuromuscular activation was measured with a linear surface-electromyography (EMG) array. Overall EMG activation (averaged channels) increased when the muscle contraction levels increased for both groups. EMG spatial analysis in AT repaired group showed an increased activation located distally at 85-99%, 75-97%, and 79-97% of the electrode array length for 40%, 60%, and 90% of the maximal voluntary isometric contractions, respectively. In conclusion, patients with persistent plantar flexion weakness after AT rupture showed higher distal overactivation in GM.
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    Understanding the effect of window length and overlap for assessing sEMG in dynamic fatiguing contractions: A non-linear dimensionality reduction and clustering
    (2021) De la Fuente, Carlos; Martinez-Valdes, Eduardo; Ignacio Priego-Quesada, Jose; Weinstein, Alejandro; Valencia, Oscar; Kunzler, Marcos R.; Alvarez-Ruf, Joel; Carpes, Felipe P.
    The Short-Time Fourier transform (STFT) is a helpful tool to identify muscle fatigue with clinical and sports applications. However, the choice of STFT parameters may affect the estimation of myoelectrical manifestations of fatigue. Here, we determine the effect of window length and overlap selections on the frequency slope and the coefficient of variation from EMG spectrum features in fatiguing contractions. We also determine whether STFT parameters affect the relationship between frequency slopes and task failure. Eighty-eight healthy adult men performed one-leg heel-rise until exhaustion. A factorial design with a window length of 50, 100, 250, 500, and 1000 ms with 0, 25, 50, 75, and 90% of overlap was used. The frequency slope was non-linearly fitted as a task failure function, followed by a dimensionality reduction and clustering analysis. The STFT parameters elicited five patterns. A small window length produced a higher slope frequency for the peak frequency (p < 0.001). The contrary was found for the mean and median frequency (p < 0.001). A larger window length elicited a higher slope frequency for the mean and peak frequencies. The largest frequency slope and dispersion was found for a window length of 50 ms without overlap using peak frequency. A combination of 250 ms with 50% of overlap reduced the dispersion both for peak, median, and mean frequency, but decreased the slope frequency. Therefore, the selection of STFT parameters during dynamic contractions should be accompanied by a mechanical measure of the task failure, and its parameters should be adjusted according to the experiment's requirements.