Aims: Our purpose was to determine whether Transcranial Direct Current Stimulation (tDCS) improves performance in untrained individuals for supramaximal intermittent exercise. Methods: In a cross-over design, 11 healthy male subjects (26.8 ± 4.6 years) performed four Wingate trials after 20 minutes of anodal or sham tDCS over the left Insular Cortex (IC). For performance indexes, Relative Peak Power (RPP), Relative Average Power (RAP) and Fatigue Index (FI) were computed. Also, a Rating of Perceived Exertion (RPE) and Electromyography (EMG) signal were used to assess central and muscle fatigue development. Results: There was a significant difference over trials on all performance indexes, but there were no significant condition x trial interactions for any of the indexes. RPE increased significantly over trials, but there was no condition x trial interaction. There was no significant difference over trials on EMG for the rectus femoris and vastus medialis muscles; however, EMG decreased over trials for the vastus lateralis muscle. Furthermore, there was no condition x trial interaction on the EMG signal for any of the muscles. Conclusion: Our findings suggest that the anodal tDCS technique has no impact on physical performance, perceived exertion nor muscle fatigue development for supramaximal intermittent exercise.
The aim of our study was to estimate the muscle skeletal load of human activities in the car industry, for that purpose MSC Adams Lifemodeler was used to build a mechanical model for a work place simulation were a electric screw driving was used. The data for model assembly was provided by video captured recordings, electromyography measurements and anthropometric data of workers. The task chosen for simulation was one of the more demanding, presenting a high-risk level for musculoskeletal disorders, considering the plant ergonomic department classification. The model allows the calculation of bone forces and joint moments of force. This will allow, in the future, to obtain the values of muscle skeletal action forces in wrist forearm and shoulder, caused by the action of the electric screwdriving tool. Results presented are from an ongoing study.
It is well established that caffeine has ergogenic effects on endurance exercise performance. This evidence often comes from well-designed studies in which subjects receive either caffeine or placebo in double-blind, randomized and counterbalanced order. Here, we propose a new methodology which aims to estimate the effects of participant expectancy of ergogenic or anti-ergogenic effects on performance. Sixteen (16) participants performed three (3) 30-minute running tests after being told they would be provided with either a harmful treatment (lactic acid), a beneficial treatment (caffeine) or a placebo. In each blinded case, subjects were given caffeine. The velocity and RPE during the time trial were examined in light of the participant’s expectancy before and after the endurance event using Bayesian multilevel models. For pre-exercise expectancy, there is a 92% probability that caffeine expectation decreases RPE (posterior median±SD -0.65±0.36) and a 79% probability that lactic acid expectation increases RPE (posterior median±SD 0.58±0.47) with expectations for placebo and ‘not sure’ falling in between (posterior median±SD: -0.37±0.32 and -0.22±0.37, respectively). In general, our interventions suggest an 81% probability that caffeine lowers RPE. However, there was no effect of caffeine supplementation on running velocity (median±SD 0.04±0.08 km.h-1). We concluded that when a participant believed they are under a potentially positive treatment, their RPE decreased but if they believed themselves to be under a harmful treatment, their RPE increased, regardless of the actual positive intervention; neither caffeine nor the expectancy of a particular intervention improved actual performance as measured by running velocity in a 30-minute period.
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