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The aim of this study was to understand the amplitude and localization of neuromuscular response induced by a training session combining an aerobic and a resistance component. Ten healthy men completed a single session of combined (aerobic and resistance) and aerobic only training, in a randomized order. Surface electromyographic activity and torque obtained during maximal voluntary and electrically evoked contractions of the knee extensor muscles were analyzed to distinguish peripheral from central adaptations. The isometric torque developed by the knee extensor muscles during maximal voluntary contraction decreased significantly following a single session of both combined (-9.2%, p=0.043) and aerobic(-9.6%, p =0.005) training. This was accompanied by a decrease in central activation of the knee extensor muscles after each training session (respectively 2.9, p=0.005 and 1.8% p=0.040) as indicated by twitch interpolation technique. After the combined training protocol, the peak torque of the twitch significantly increased by 6.8% (p=0.046), whereas it decreased by 17.3% (p=0.016) after the aerobic training protocol. The present study demonstrates that the decrease in torque production is similar after a single combined training session or after an aerobic training session of the same duration. Both central and peripheral mechanisms could explain the decrease of torque. [ABSTRACT FROM AUTHOR]

Scene perception allows humans to extract information from their environment and plan navigation efficiently. The automatic extraction of potential paths in a scene, also referred to as navigational affordance, is supported by scene-selective regions (SSRs) that enable efficient human navigation. Recent evidence suggests that the activity of these SSRs can be influenced by information from adjacent spatial memory areas. However, it remains unexplored how this contextual information could influence the extraction of bottom-up information, such as navigational affordances, from a scene and the underlying neural dynamics. Therefore, we analyzed ERPs in 26 young adults performing scene and spatial memory tasks in artificially generated rooms with varying numbers and locations of available doorways. We found that increasing the number of navigational affordances only impaired performance in the spatial memory task. ERP results showed a similar pattern of activity for both tasks, but with increased P2 amplitude in the spatial memory task compared with the scene memory. Finally, we reported no modulation of the P2 component by the number of affordances in either task. This modulation of early markers of visual processing suggests that the dynamics of SSR activity are influenced by a priori knowledge, with increased amplitude when participants have more contextual information about the perceived scene. Overall, our results suggest that prior spatial knowledge about the scene, such as the location of a goal, modulates early cortical activity associated with SSRs, and that this information may interact with bottom-up processing of scene content, such as navigational affordances., (© 2024 Massachusetts Institute of Technology.)

Background: Falling is an important public health issue because of its prevalence and severe consequences. Evaluating muscle performance is important when assessing fall risk. The study aimed to identify factors [namely muscle capacity (strength, quality, and power) and spatio-temporal gait attributes] that best discriminate between fallers and non-fallers in older adults. The hypothesis is that muscle quality, defined as the ratio of muscle strength to muscle mass, is the best predictor of fall risk., Methods: 184 patients were included, 81% (n = 150) were women and the mean age was 73.6 ± 6.83 years. We compared body composition, mean grip strength, spatio-temporal parameters, and muscle capacity of fallers and non-fallers. Muscle quality was calculated as the ratio of maximum strength to fat-free mass. Mean handgrip and power were also controlled by fat-free mass. We performed univariate analysis, logistic regression, and ROC curves., Results: The falling patients had lower muscle quality, muscle mass-controlled power, and mean weighted handgrip than the non-faller. Results showing that lower muscle quality increases fall risk (effect size = 0.891). Logistic regression confirmed muscle quality as a significant predictor (p < .001, OR = 0.82, CI [0.74; 0.89]). ROC curves demonstrated muscle quality as the most predictive factor of falling (AUC = 0.794)., Conclusion: This retrospective study showed that muscle quality is the best predictor of fall risk, above spatial and temporal gait parameters. Our results underscore muscle quality as a clinically meaningful assessment and may be a useful complement to other assessments for fall prevention in the aging population., (© 2024. The Author(s).)

Purpose: Isokinetic knee extensor strength is poorly evaluated in geriatric day hospitals (GDHs), despite its potential functional significance compared to grip strength. This study aimed to investigate age-related effects on absolute and relative isokinetic knee extensor peak torque (KEPT) data in community-dwelling older GDH patients., Methods: A total of 472 French GDH patients (179 men and 293 women, aged 75-94 years) participated in this study. Absolute and relative KEPT were measured at six distinct angular velocities between 0.52 and 3.14 rad/s. In addition, comfortable gait speed and grip strength were assessed. Participants were stratified by sex and age using 5-year intervals. One-way ANOVAs were used to examine age-related effects on KEPT values. Multiple linear regression models were employed to investigate the associations between gait speed and both mean KEPT values and grip strength, with separate models conducted on absolute and relative values., Results: The recruited GDH patients presented lower absolute and relative KEPT values in comparison with established reference values for healthy community-dwelling older individuals, with men being consistently stronger than women. Notably, there was a significant decline in both absolute and relative KEPT values beyond the age of 85 for both sexes. Importantly, the multiple linear regression analyses conducted revealed a significant positive relationship between gait speed and mean KEPT values, surpassing the association with grip strength., Conclusions: These findings underscore the clinical importance of assessing isokinetic knee extensor strength in community-dwelling older GDH patients, particularly for tailoring personalized physical activity interventions., (© 2024. The Author(s), under exclusive licence to European Geriatric Medicine Society.)

Apathy is a pervasive clinical syndrome in neurocognitive disorders, characterized by a quantitative reduction in goal-directed behaviors. The brain structures involved in the physiopathology of apathy have also been connected to the brain structures involved in probabilistic reward learning in the exploration-exploitation dilemma. This dilemma in question involves the challenge of selecting between a familiar option with a more predictable outcome, and another option whose outcome is uncertain and may yield potentially greater rewards compared to the known option. The aim of this study was to combine experimental procedures and computational modeling to examine whether, in older adults with mild neurocognitive disorders, apathy affects performance in the exploration-exploitation dilemma. Through using a four-armed bandit reinforcement-learning task, we showed that apathetic older adults explored more and performed worse than non-apathetic subjects. Moreover, the mental flexibility assessed by the Trail-making test-B was negatively associated with the percentage of exploration. These results suggest that apathy is characterized by an increased explorative behavior and inefficient decision-making, possibly due to weak mental flexibility to switch toward the exploitation of the more rewarding options. Apathetic participants also took longer to make a choice and failed more often to respond in the allotted time, which could reflect the difficulties in action initiation and selection. In conclusion, the present results suggest that apathy in participants with neurocognitive disorders is associated with specific disturbances in the exploration-exploitation trade-off and sheds light on the disturbances in reward processing in patients with apathy., (© 2023. Springer Nature Limited.)