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The perception of painful bodily sensations is usually negatively associated with endurance performance, and dissociative strategies are routinely recommended to divert attention away from these signals. The effectiveness of dissociative strategies has not been clearly established, but associative strategies seem to benefit physically trained individuals. The purpose of this study was to clarify and compare the effects of these two strategies on the maintenance of physical effort in a physically active population. We hypothesised that an associative focus would increase endurance performance more than a dissociative focus. The participants (572: 161 women and 411 men) performed muscular endurance tasks until exhaustion in associative and dissociative conditions. The aerobic fitness level could be tested in 285 participants using a maximum aerobic speed field test. To perform additional statistical analyses, two fitness-level groups were created based on the median. Our results showed that participants performed better in the associative condition than the dissociative condition, and complementary analyses revealed that association specifically improved performance in the higher aerobic fitness group. These results suggest that monitoring afferent painful signals could be an interesting attentional strategy and that individuals can develop abilities to tolerate and apprehend this sensory feedback. These results are discussed in relation to a recent interoceptive model of physical effort. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the neural and muscular changes associated with electrical stimulation (FS) training and subsequent detraining. Twenty healthy active men were randomized to receive (intervention group) or not (control group) 4 weeks of ES strength training followed by 4 weeks of detraining. Quadriceps ES training sessions (20 minutes per session, 4 sessions per week) were completed under isometric loading conditions. Quadriceps maximal voluntary contraction (MVC) strength, activation level, maximal electromyographic (EMG) activity, and excitation-contraction coupling properties were assessed before training, after training, and after detraining. Maximal voluntary contraction strength did not change after training but significantly increased after detraining (+21.5%; p < 0.05). Activation level (+7.3%) and maximal EMG activity (+27.9%) increased significantly after training and remained elevated after detraining (p < 0.05). Vastus lateralis M-wave amplitude did not change during the study period, whereas quadriceps contractile properties were significantly impaired after training but then recovered to pre-training values after detraining. We conclude that the maximal force-generating capacity of the quadriceps was unchanged after 4 weeks of ES strength training because of the interplay between neural (increased activation) and muscular (contractile impairment) changes. On the other hand, recovered contractile function and preserved activation after 4 weeks of detraining resulted in significant MVC strength increases. Quadriceps strength training via ES may induce overreaching and delayed adaptations and therefore should be used with caution. These findings may help in conceiving effective ES strength training programs for physically active subjects. KEY WORDS knee extensors, muscle activation, excitation-contraction coupling, contractile properties

Background and Objective: Individuals who survive a stroke often display considerable gait impairments that occur in part due to inadequate muscle force production. This study aimed to investigate lower limb muscle forces in poststroke patients during walking. Methods: Kinematics, kinetics, and electromyographic (EMG) measurements were performed on nine poststroke and healthy individuals walking at natural speed in a cross-sectional study. Recorded parameters were used in an EMG-driven model to estimate the forces exerted by the muscles around the knee and ankle joints during the stance (braking and propulsion) and swing phases. Results: For hemiparetic patients, in comparison to healthy controls, the paretic side exhibited (i) lower forces generated by plantar-flexors and quadriceps respectively during the braking and propulsion phases, but (ii) higher knee-flexors forces during the propulsion phase. Regarding the non-paretic side, it displayed (i) higher forces generated by knee-flexors and quadriceps (only for the propulsion phase) forces during the stance phase, and (iii) higher plantar-flexors forces during the swing phase, in comparison to controls. Conclusion: Reduced forces exerted by the plantar-flexors and the knee-extensors along with increased force generated by the knee-flexors on the paretic side give possible explanation for hemiparetic gait abnormalities. Increased muscle forces exerted by the non-paretic side might be a compensatory strategy to better support body weight and properly adjust the center of mass forward. [ABSTRACT FROM AUTHOR]