Validation of an Embedded Motion-Capture and EMG Setup for the Analysis of Musculoskeletal Disorder Risks during Manhole Cover Handling

Musculoskeletal disorders in the workplace are a growing problem in Europe. The measurement of these disorders in a working environment presents multiple limitations concerning equipment and measurement reliability. The aim of this study was to evaluate the use of inertial measurement units against a reference system for their use in the workplace. Ten healthy volunteers conducted three lifting methods (snatching, pushing, and pulling) for manhole cover using a custom-made tool weighting 20 and 30 kg. Participants’ back and dominant arm were equipped with IMU, EMG, and reflective markers for VICON analysis and perception of effort was estimated at each trial using a Visual Analog Scale (VAS). The Bland–Altman method was used and results showed good agreement between IMU and VICON systems for Yaw, Pitch and Roll angles (bias values < 1, −4.4 < LOA < 3.6°). EMG results were compared to VAS results and results showed that both are a valuable means to assess efforts during tasks. This study therefore validates the use of inertial measurement units (IMU) for motion capture and its combination with electromyography (EMG) and a Visual Analogic Scale (VAS) to assess effort for use in real work situations.

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

The 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. The aim of this meta-analysis was to investigate the effect of pharmacologically blocking muscle afferents on the PE. Six 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. The 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). The heterogeneity in results between groups reveals that the inclusion of other perceptions 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 generating PE.

The Effect of Static and Dynamic Stretching during Warm-Up on Running Economy and Perception of Effort in Recreational Endurance Runners

This randomized crossover counterbalanced study investigated, in recreational runners, the acute effects of pre-exercise stretching on physiological and metabolic responses, endurance performance, and perception of effort. Eight male endurance runners (age 36 ± 11 years) performed three running-until-exhaustion tests, preceded by three warm-ups, including the following different stretching protocols: static (SS), dynamic (DS), and no-stretching (NS). During the SS and DS sessions, the warm-up consisted of 10 min of running plus 5 min of SS or DS, respectively, while during the NS session, the warm-up consisted of 15 min of running. Physiological and metabolic responses, and endurance running performance parameters, were evaluated. The perception of effort was derived from the rating of perceived exertion (RPE). Running economy significantly improved after SS (p < 0.05) and DS (p < 0.01), and RPE values were significantly lower in SS (p < 0.05) and DS (p < 0.01), compared to NS. No differences in physiological and metabolic responses among the sessions were found. This study showed that including SS and DS within the warm-up ameliorated running economy and decreased the perception of effort during a running-until-exhaustion test, highlighting the benefits of stretching on endurance performance. These results should encourage recreational runners to insert stretching during warm-up, to optimize the running energy costs, reducing the perception of effort and making the training sessions more enjoyable.

Perception of effort and the allocation of physical resources: a generalization to upper-limb motor tasks

PURPOSE: The perception of effort (PE) is widely used to prescribe and monitor exercise during locomotor and resistance tasks. The present study examines the validity of PE to prescribe and monitor exercise during upper-limb motor tasks under various loads and speed requirements.METHODS: Forty participants volunteered in two experiments. In experiment 1, we used four PE intensities to prescribe exercise on a modified version of the box and block test (BBT) and a pointing task. We investigated the possibility of monitoring the exercise intensity by tracking changes in PE rating in response to three different tempos or additional weights. Experiment 2 replicated the possibility of prescribing the exercise with the PE intensity during the BBT and explored the impact of additional weights on performance and PE during the standardized version of the BBT. Muscle activation, heart rate and respiratory frequencies were recorded.RESULTS: In experiment 1, increasing the PE intensity to prescribe exercise induced an increased performance between each intensity. Increasing task difficulty with faster movement tempo and adding weight on the forearm increased the rating of PE. Experiment 2 replicated the possibility to use PE intensity for exercise prescription during the BBT. When completing the BBT with an additional weight on the forearm, participants maintained performance at the cost of a higher PE. In both experiments, changes in PE are associated with changes in muscle activation. CONCLUSION: Our results suggest that PE is a valid tool to prescribe and monitor exercise during upper-limb motor tasks.

Effect of the subjective intensity of fatigue and interoceptive awareness on perceptual regulation and performance during sustained physical activity

Background: The subjective experience of fatigue impairs an individual’s ability to sustain physical endurance performance. However, precise understanding of exactly how the perception of fatigue limits performance remains unclear. Methods: Here, we examined whether subjective intensity of perceived fatigue, pre-induced through prior upper body activity, differentially impacted performance and altered perceptual (effort) and affective responses during a sustained, isometric contraction in lower body. We also explored whether (cardiac) interoceptive awareness moderated the relationship between the perception of fatigue and effort. Using a repeated-measures study design, thirty male participants completed three experimental conditions, with the intensity of the pre-induced state of fatigue manipulated to evoke severe (SEV), moderate (MOD) and minimal (control; CON) perceptions prior to the performance of a sustained, sub-maximal contraction in the dominant knee extensors. Results: Participants’ capacity to sustain the isometric contraction was significantly impaired (vs. CON, MOD: -9.5 ± 19.1%, p=0.007; SEV: -13.7 ± 17.2%, p&lt;0.001), with perception of effort higher (SEV, MOD vs. CON: b=-0.90, p&lt;0.001), when perceptions of fatigue were elevated. However, the effect on performance (SEV vs. MOD: -2.5 ± 19.9%, p=0.455) and effort perception (SEV vs. MOD: b=-0.06, p=0.612) was not dependent upon the manipulated intensity of the pre-induced state of fatigue. Perceived fatigue was shown to predict the perception of effort during the endurance task. However, disassociation of perceptual constructs was evidenced with perceived effort, but not fatigue, associated with endurance time (CON: r=-0.57, p=0.004; MOD: r=-0.69, p&lt;0.001; SEV: r=-0.59, p=0.003). Interoceptive awareness was shown to attenuate the relationship between perceived fatigue and effort, but only when fatigue was elevated within the experimental manipulations (b=-4.45, p=0.005). Conclusions: Perception of fatigue indirectly limits endurance performance by exerting influence over sensory processes making a physical task appear more effortful. Moreover, this effect is influenced by individual awareness of interoceptive representations of bodily states.

Results of a postural education program, with a gamified intervention vs traditional intervention

The teaching methodology adopted by teachers can influence the levels of participation and learning of students. The main goal of this study was to compare the effect of two intervention programs of postural education according to the used methodology. A total of 36 students (19 girls and 17 boys) in the 1st year of high school participated in the study. In the first intervention program a gamified methodology was applied, while in the second one a traditional methodology was used. Both intervention programs were carried out along 6 sessions. Theoretical contents were analyzed through questionnaires (COSACUES and COSACUES-AEF) and muscular endurance through three physical tests (Biering-Sørensen Test, Side Bridge Test and Prone Forearm Plank Test) before and after the intervention. Motivation levels (Feeling Scale) and perception of effort (OMNI Scale) were measured after each session. The results obtained did not show significant differences between methodologies, but differences have been found in terms of gender and type of methodology. Girls were shown to assimilate better contents with the gamified methodology. There was also a greater perception of effort and greater motivation with the gamified intervention. Therefore, the application of gamified educational interventions by teachers can be an interesting strategy to increase the levels of motivation and effort of students.