Biology subjects

Pageaux, B.

Publications and source records attributed to Pageaux, B..

3 recordsLinked to original sources

bioRxiv2022

Eccentric cycling involves greater mental demand and cortical activation of the frontoparietal network

Eccentric, compared to concentric exercise, is proposed to involve different neuro-motor processing strategies and a higher level of mental demand. This study compared eccentric and concentric cycling at matched perceived effort and torque for the mental demand and related-cortical activation patterns. Nineteen men (30 {+/-} 6 yrs) performed four different 5-min cycling conditions at 30 RPM on a semi-recumbent isokinetic cycle ergometer: 1) concentric at a moderate perceived effort (23 on the CR100(R) scale) without torque feedback; 2) concentric and 3) eccentric at the same average torque produced in the first condition; and 4) eccentric at the same moderate perceived effort than the first concentric condition. The conditions 2-4 were randomised. After each condition, mental demand was monitored using the NASA Task Load Index scale. Changes in oxy-(O2Hb) and deoxy-(HHb) haemoglobin during exercise were meas-ured over both prefrontal cortices and the right parietal lobe from a 15-probe layout using a continuous-wave NIRS system. Mental demand was significantly higher during eccentric compared to concentric cycling (+52%, p = .012) and when the exercise intensity was fixed by the torque rather than the perceived effort (+70%, p .001). For both torque- or perceived effort-matched exercises, O2Hb increased significantly (p < .001) in the left and right prefrontal cortices, and right parietal lobe, and HHb decreased in the left, and right, prefrontal cortices during eccentric compared to concentric cycling. This study supports that acute eccentric cycling, compared to concentric cycling, involves a higher mental demand and frontoparietal network activation.

physiology↗

bioRxiv2021

Pharmacological blockade of muscle afferents and perception of effort: a systematic review with meta-analysis

BackgroundThe perception of effort (PE) provides information on task difficulty and influences physical exercise regulation and human behavior. This perception differs from other-exercise related perceptions such as pain. There is no consensus on the role of group III-IV muscle afferents as a signal processed by the brain to generate PE. ObjectiveThe aim of this meta-analysis was to investigate the effect of pharmacologically blocking muscle afferents on the PE. MethodsSix databases were searched to identify studies measuring the ratings of perceived effort (RPE) during physical exercise, with and without pharmacological blockade of muscle afferents. Articles were coded based on the operational measurement used to distinguish studies in which PE was assessed specifically (effort dissociated) or as a composite experience including other exercise-related perceptions (effort not dissociated). Articles that did not provide enough information for coding were assigned to the unclear group. ResultsThe effort dissociated group (n=6) demonstrated a slight RPE increase with reduced muscle afferents feedback (standard mean change raw (SMCR), 0.39; 95%CI, 0.13 to 0.64). The group effort not dissociated (n=2) did not reveal conclusive results (SMCR, -0.29; 95%CI, -2.39 to 1.8). The group unclear (n=8) revealed a slight RPE decrease with reduced muscle afferents feedback (SMCR, -0.27; 95%CI, -0.50 to -0.04). ConclusionsThe heterogeneity in results between groups reveals that the inclusion of perceptions other than effort in its rating influences the RPE scores reported by the participants. The absence of decreased RPE in the effort dissociated group suggests that muscle afferents feedback is not a sensory signal of PE. Key pointsO_LITo date, there is no consensus on the neurophysiological signal processed by the brain to generate the perception of effort. C_LIO_LIFollowing a systematic search in six databases, this meta-analysis suggests that reducing afferent feedback from the working muscles via epidural anesthesia does not reduce perception of effort. C_LIO_LIThis systematic review suggests that afferent feedback from the working muscles is not the neurophysiological signal processed by the brain to generate the perception of effort. C_LI

neuroscience↗

bioRxiv2021

Perception of effort during an isometric contraction is influenced by prior muscle lengthening or shortening

PurposeFollowing a shortening or lengthening muscle contraction, the torque produced in the isometric steady state is distinctly lower (residual torque depression; rTD) or higher (residual torque enhancement; rTE), respectively, compared to a purely isometric contraction at the same final muscle length and level of activation. This is referred to as the history dependence of force. When matching a given torque level, there is greater muscle activation (electromyography; EMG) following shortening and less activation following lengthening. Owing to these differences in neuromuscular activation, it is unclear whether perception of effort is altered by the history dependence of force. MethodsExperiment 1 tested whether perception of effort differed between the rTD and rTE state when torque was matched. Experiment 2 tested whether perception of effort differed between the rTD and rTE state when EMG was matched. Finally, experiment 3 tested whether EMG differed between the rTD and rTE state when perception of effort was matched. ResultsWhen torque was matched, both EMG and perception of effort were higher in the rTD compared to rTE state. When EMG was matched, torque was lower in the rTD compared to rTE state while perception of effort did not differ between the two states. When perception of effort was matched, torque was lower in the rTD compared to rTE state and EMG did not differ between the two states. ConclusionThe combined results from these experiments indicate that the history dependence of force alters ones perception of effort, dependent on the level of motor command.

neuroscience↗