ECSS Paris 2023: CP-BM17
INTRODUCTION: Proprioception plays a critical role in movement control by providing the central nervous system with information about limb position, and force production. Two commonly assessed components of proprioception are the senses of force and position, which rely on overlapping but distinct neural mechanisms. The proprioceptive sense of position primarily relies on afferent input from muscle spindles and joint receptors, whereas the proprioceptive sense of force relies on integrating this sensory feedback with centrally generated motor commands. Disruptions in both senses following anterior cruciate ligament reconstruction (ACLR) potentially contribute to persistent neuromuscular deficits and altered knee function. Although impairments in both have been reported after ACLR, it remains unclear which is affected more. Therefore, the purpose of this study was to determine if the proprioceptive force or position is more impaired in people with ACLR. METHODS: Male and female athletes with a history of unilateral ACLR (1.4 +/- 0.95 years post-surgery; age: 19.7 +/- 1.6 years; height: 165 +/- 4 cm; weight: 155 +/- 18 kg) were recruited and compared to an age- and sex-matched healthy control group with no history of knee injury (age: 21.6 +/- 1.3 years; height: 173 +/- 8.6 cm; weight: 74 +/- 17 kg). All testing was conducted about the knee joint using a Humac Norm isokinetic dynamometer. The proprioceptive sense of force was evaluated using submaximal force reproduction tasks, where participants performed target contractions with visual feedback followed by reproduction trials without feedback, relying on perceived effort to match the target. The proprioceptive sense of position was evaluated using a position reproduction task, during which participants moved their leg to a target knee angle corresponding to 60-70% of their maximum knee extension range of motion with visual feedback, followed by an active reproduction of the target position without feedback. Force and position reproduction was quantified using absolute error (accuracy) and constant error (bias), calculated relative to the target force or position. We hypothesized that participants with ACLR would demonstrate greater relative impairment in force sense compared with position sense, reflecting the greater reliance on central motor integration processes. RESULTS: Preliminary results showed that people with ACLR had similarly impaired senses of both force (p = 0.0071; d = 0.59) and position (p = 0.0072; d = 0.64) in their injured leg, compared to the uninjured leg, whereas there were no differences in the senses of force (p = 0.51) or position (p = 0.34) between the legs of the healthy controls. CONCLUSION: These findings indicate that, following ACLR, there are similar impairments in the proprioceptive sense of force and position, suggesting that proprioceptive deficits may be due to widespread sensory deficits.
Read CV Isabella RyanECSS Paris 2023: CP-BM17
INTRODUCTION: Work-related musculoskeletal disorders (WMSDs) are highly prevalent globally and pose substantial health and economic challenges. Exoskeletons might reduce physical load and biomechanical stress during physically demanding tasks. However, operating such assistive devices requires additional motor and cognitive resources, potentially leading to cognitive-motor interference (CMI). Thus far, the influence of exoskeleton use on accuracy and speed in precision tasks has received limited attention. Building on previous work, this study assessed the reproducibility of speed-accuracy trade-off slopes during an exoskeleton-supported overhead drilling Fitts task, comparing long (12 repetitions) and short versions (8 repetitions) under single-task (ST) and dual-task (DT) conditions in a simulated work environment. METHODS: Fifteen participants (mean age M = 25.2 years, SD = 3.99 years; 20% males, 80% females) without neurological or musculoskeletal disorders were recruited from the German Sport University Cologne and performed an overhead drilling Fitts task with indices of difficulty 2.32, 3.91 and 5.39 across eight simulated working conditions. Four conditions were completed with and without an active upper body exoskeleton: (1) ST long version (3 sets of 12 repetitions), (2) ST short version (2 sets of 8 repetitions), (3) visual DT (DTv) long version, and (4) DTv short version. Slopes of the speed-accuracy trade-off were evaluated across all conditions. The reliability of the speed-accuracy trade-off slopes for the long and short conditions was assessed using an intraclass correlation coefficient (ICC), mean differences were calculated in SPSS. RESULTS: The slopes of the speed-accuracy trade-off showed low agreement between the long and short conditions. Most of the mean comparisons of the slopes were non-significant (p < = 0.05), with ICC values of 0.119 for ST with exoskeleton use, and 0.288 and 0.018 for ST and DTv without exoskeleton use, respectively. A significant mean difference with an ICC of 0.542 was observed only for DTv with exoskeleton use. Several outliers were detected in the initial analysis. CONCLUSION: The speed-accuracy trade-off slopes of the long and short versions of the Fitts task showed low and generally non-significant ICCs, indicating limited reliability and reproducibility between the two versions. These results might be influenced by the relatively small sample size and the uneven gender distribution of the participants. The present analysis will be verified to identify potential reasons for the outlier values as part of a data quality assessment.
Read CV Isabel BraunECSS Paris 2023: CP-BM17
INTRODUCTION: An urgent situation or pressured environment often makes people perform beyond or below their ordinary performance. These examples suggest that people implicitly set limits on their own performance depending on context. In the field of motor control, people tend to adjust their performance in response to feedback obtained during a motor task. The current study demonstrated that the personal limit can be changed by unwittingly manipulated feedback on one's performance during a pinching force exertion and throwing. METHODS: In the pinching task, participants applied their force on a pinching device with the thumb and index fingers for 5 seconds while a time-series of the applied force was displayed on a screen in real time. Each participant exerted the maximum force and 50% of their maximum force on a subjective scale in 3 trials each. Each trial was assigned unwittingly to one of the three feedback types: control (no manipulation), upwards (gradually increased in the second half), or downwards (gradually decreased in the second half). In the throwing task, participants threw a ball toward a net while the ball speed was displayed on a screen. Each participant performed two sets of 10 balls with their maximum effort. Each set was assigned unwittingly to one of the two feedback types: upwards (gradually increased in the second half), or downwards (gradually decreased in the second half). The average of the applied force/ball speed was compared across the period (the first vs. second half of the trials/sets) by a paired t-test. RESULTS: In the pinching task, the average force in the last 1sec was significantly larger with the downwards feedback (average increase of 7.9% in maximum force) and smaller with the upwards feedback (average decrease of 7.0% in maximum force) compared to that in the first 1sec of each trial (p<.05). In the throwing task, the average ball speed in the second 5 balls was significantly larger with the downwards feedback (average increase of 1.2km/h) and smaller with the upwards feedback (average decrease of 2.2km/h) compared to that in the first 5 balls of each set (p<.05). These results suggest that the participants under- or over-estimated their own performance due to the unwittingly manipulated feedback, which in turn increased or decreased the applied force. CONCLUSION: Our findings suggest that the limit of people’s motor performance can be changed due to changes in the perception of their performance based on the covert manipulation of feedback. With the appropriate use, such feedback manipulation may contribute to the improvement of motor performance and promotion of learning and skill acquisition in various sports fields. On the other hand, it has theoretical implications on how the brain controls its own limit in performance.
Read CV Ayane KusafukaECSS Paris 2023: CP-BM17