Biology subjects

Sarcher, A.

Publications and source records attributed to Sarcher, A..

3 recordsLinked to original sources

bioRxiv2026

Mental fatigue impairs cycling endurance performance and perception of effort, but not muscle activation

Mental fatigue is induced by prolonged engagement in cognitively demanding tasks and impairs endurance performance. The neuropsychophysiological mechanisms underlying this decreased performance remain unclear, with suggestion that mental fatigue may disrupt motor command and consequently muscle activation. We aimed to test this hypothesis in a repeated cross-over design study in which 18 participants completed two experimental sessions involving a time-to-task failure cycling test at 80% of peak power output. Each cycling task was preceded by 1h of a prolonged Stroop task (Stroop condition) or a neutral control task (Control condition). Mental fatigue was assessed using a visual analog scale anchored with "not fatigued at all" and "extremely fatigued. Perception of effort and surface electromyography from ten lower-limb muscles of the right leg were recorded at regular intervals during cycling. Mental fatigue was higher in the Stroop compared to the Control condition (p = .002). Endurance cycling time was shorter in the Stroop than in the Control condition (887 {+/-} 284 s vs. 999 {+/-} 379 s, respectively; -111 {+/-} 160 s, p = .009). No significant differences in electromyography parameters were observed between Stroop and Control conditions, for any muscle (p > .05). Perception of effort was higher in the Stroop condition from the onset of the cycling task (p = .006), and the rate of increase in perception of effort was significantly higher in the Stroop than Control condition (p = .031). Our findings do not support the hypothesis that mental fatigue alters motor control or increases central motor command, as no changes in muscle activation were detected. Conversely, our results reinforce the notion that prolonged cognitive engagement impairs endurance performance primarily through an increased perception of effort. Future research should consider combining surface electromyography with more sensitive neurophysiological techniques to investigate potential subtle changes in motor drive during dynamic, whole-body tasks under mental fatigue.

physiology↗

bioRxiv2025

Expert drummers replicate neuromechanical signatures of physiological tremor at extreme movement frequencies.

This study investigates the neuromechanical characteristics associated with expert drummers ability to achieve unilateral ankle oscillation frequencies of up to 10 Hz, surpassing known limits for lower-body movements. Eighteen experienced drummers performed trials at various frequencies, using a protocol combining H-reflex measurement, motion analysis, and electromyography. Our findings closely parallel neuromechanical signatures observed in ankle tremors, with an average movement frequency of 6.3 Hz (SD: 0.5 Hz), and a modulation range of 5.5-7.3 Hz. Oscillatory behavior may result from the interplay between muscle-tendon mechanics and stretch reflex loops. At 6.3 Hz, soleus activation lasts 56.2 ms, shortening by 2.5 ms/Hz (p < 0.001), while tibialis anterior activation lasts 52.7 ms, decreasing by 5.3 ms/Hz (p < 0.001). The latency between ankle dorsiflexion and soleus activation is 48.5 ms at 6.3 Hz, matching the short-latency stretch reflex, and decreases by 11 ms/Hz (p<0.001). Limiting factors for the drummers maximal frequency are soleus and tibialis anterior co-activation, reducing ankle movement, and high levels of activation in hip and back muscles, associated with discomfort and pain. Drummers with higher maximal frequencies (above 7.5 Hz, n = 6) show shorter tibialis anterior activation durations (34.3 ms vs. 53.2 ms, p = 0.0013) and reduced tensor fascia latae activation (6.2% vs. 21.0%, p = 0.0135). These findings highlight phenomenological similarities between the ankle technique and physiological tremors, in terms of neuromechanical timing and oscillatory patterns. Precise tibialis anterior timing and relaxed proximal muscle activation are critical for performance, while injury prevention strategies remain essential. Significance StatementThis study provides a neuromechanical analysis of expert metal drummers producing exceptionally high-frequency ankle movements--up to 10 Hz--that surpass known limits for lower-body movements, and draws parallels with physiological action tremors. By comparing their motor patterns to those reported in tremor literature, this work highlights the role of neuromuscular timing and mechanical adaptations, such as stretch reflex dynamics and muscle-tendon interactions. The findings demonstrate that precise tibialis anterior timing and relaxed proximal muscles are critical for performance, while stabilization demands increase the risk of musculoskeletal disorders in the lower back and hips. These insights bridge performance science, biomechanics, and injury prevention, offering valuable perspectives for optimizing high-frequency movements in music, sports, and rehabilitation.

physiology↗

bioRxiv2021

Functional connectivity networks of common synaptic inputs to motor neurons reveal neural spinal synergies during a multi-joint task

Movements are reportedly controlled through the combination of synergies that generate specific motor outputs by imposing an activation pattern on a group of muscles. To date, the smallest unit of analysis has been the muscle. In this human study, we decoded the spiking activities of spinal motor neurons innervating six lower limb muscles during an isometric multi-joint task. We identified their common low-frequency components, from which networks of common synaptic inputs to the motor neurons were derived. The vast majority of the identified motor neurons shared common inputs with other motor neuron(s). In addition, groups of motor neurons were partly decoupled from their innervated muscle, such that motor neurons innervating the same muscle did not necessarily receive common inputs. Conversely, some motor neurons from different muscles - including distant muscles - received common inputs. Our results provide evidence of a synergistic control of a multi-joint motor task at the spinal motor-neuron level. TeaserThe generation of movement involves the activation of many spinal motor neurons from multiple muscles. A central and unresolved question is how these motor neurons are controlled to allow flexibility for adaptation to various mechanical constraints. Since the computational load of controlling each motor neuron independently would be extremely large, the central nervous system presumably adopts dimensionality reduction. We identified networks of functional connectivity between spinal motor neurons based on the common synaptic inputs they receive during a multi-joint task. Our findings revealed functional groupings of motor neurons in a low dimensional space. These groups did not necessarily overlap with the muscle anatomy. We provide a new neural framework for a deeper understanding of movement control in health and disease.

neuroscience↗