Floren Colloud

The hammer throw requires optimal spatial and temporal coordination to maximise release parameters. This study aimed to identify differences in the spatiotemporal organisation of the throw across varying performance levels ranging from highly trained to world class. Using a video analysis protocol, we reconstructed the 3D hammer trajectories of 27 female and 20 male throwers. Azimuthal angles (i.e., the horizontal orientation of the hammer) were computed at key instants, and weighted regression models were used to examine their associations with performance. Results revealed significant differences in azimuthal angle at the start of the double support phase, with higher-performing throws associated with earlier foot landing ( p < 0.05). In male throwers, this pattern was also linked to an earlier initiation of the single support phase ( p < 0.001). In female throwers, performance level was differentiated by azimuthal angles at the high and low vertical points of the trajectory ( p < 0.05). These findings suggest that training should target dynamic balance to facilitate earlier support transitions and enhance angular control of the hammer's high and low points, as these spatiotemporal features are key determinants of elite performance.

Force-velocity (FV) relationships are used to evaluate athletes and individualise training in several tasks. In rowing, only one previous study has determined FV relationships using ergometers. This study aimed to develop a method to obtain FV relationships during on-water rowing, to assess their quality and inter-day reliability and to compare them with ergometer profiles. Fourteen participants performed 8 all-out starts in instrumented double scull boats with 3 scull lengths under two conditions: two active rowers or one active and one passive rower. The FV relationships, reconstructed with all the conditions, were linear with a high goodness of fit (median R²: 0.96), covering 24.6 ± 5.0% of the velocity range. Ninety-five per cent confidence intervals for maximal force (F₀: 3.9 ± 0.5%) and maximal velocity (V₀: 6.2 ± 1.5%) were relatively narrow. The coefficient of variation for inter-day reliability was below 10% and intraclass correlation ranging from 0.69 for V₀ to 0.96 for F₀. Correlations between on-water and ergometer rowing were significant for F₀ (r = 0.70) and P_max (r = 0.82) but not for V₀ (r = 0.11). F₀ and V₀ were significantly higher (23%) and lower (31%) on the ergometer, respectively. These results highlight a reliable linear FV relationship during on-water rowing to characterise rowing force production capacities, largely affected by on-water technical skills.

Purpose: This study investigated how muscle coordination is adjusted in response to a decrease in the force-generating capacity of one muscle group during a sprint cycling task. Methods: Fifteen participants were tested during a sprint before and after a fatigue electromyostimulation protocol was conducted on the quadriceps of one leg. Motor coordination was assessed by measuring myoelectrical activity, pedal force, and joint power. Results: The decrease in force-generating capacity of the quadriceps (−28.0% ± 6.8%) resulted in a decrease in positive knee extension power during the pedaling task (−34.4 ± 30.6 W; P = 0.001). The activity of the main nonfatigued synergist and antagonist muscles (triceps surae, gluteus maximus and hamstrings) of the ipsilateral leg decreased, leading to a decrease in joint power at the hip (−30.1 ± 37.8 W; P = 0.008) and ankle (−20.8 ± 18.7 W; P = 0.001). However, both the net power around the knee and the ability to effectively orientate the pedal force were maintained during the extension by reducing the coactivation and the associated negative power produced by the hamstrings. Adaptations also occurred in flexion phases in both legs, exhibiting an increased power (+17.9 ± 28.3 [P = 0.004] and +19.5 ± 21.9 W [P = 0.026]), associated with an improvement in mechanical effectiveness. Conclusion: These results demonstrate that the nervous system readily adapts coordination in response to peripheral fatigue by (i) decreasing the activation of adjacent nonfatigued muscles to maintain an effective pedal force orientation (despite reducing pedal power) and (ii) increasing the neural drive to muscles involved in the flexion phases such that the decrease in total pedal power is limited.

Non-human agents are taking a growing place in our society, in various areas (e.g. professional, private or medical) and serving numerous purposes. Therefore, understanding the way we interact with them seems crucial. In this experiment, we focused on both Human-Human and Human-Robot Interactions. The goal of the study was to extend knowledge concerning action co-representation in task sharing. We aimed to demonstrate that prior sensorimotor experience with a virtual robotic hand (via an exoskeleton) could improve action co-representation of this agent. We used an extended version of the Simon task (Joint Simon task) to evaluate action co-representation of others action.

Between limb movement asymmetries and foot force production asymmetries are thought to be detrimental for both rower's performance and risk of injury, particularly when rowing frequently on ergometers. Several ergometers with different designs can be used by rowers as part of their indoor training. Hence, this study aimed to compare asymmetries in lower limb joint kinematics and foot force production with respect to ergometer design and rowing intensity. A new symmetry index was proposed to assess these asymmetries in elite rowers during a test on three ergometers. Additionally, the asymmetry in lower limb length was assessed to investigate its relationship with kinematic and kinetic asymmetries. Parameters describing medium (5-10%) or high (>10%) asymmetries were compared between rowing ergometers and intensities. Results indicated medium asymmetries for the ankle joint angle and hip-knee joint accelerations and high asymmetries for the resultant force and the ankle joint acceleration associated with a low inter-stroke variability. Kinetic asymmetry was neither correlated to kinematic asymmetry nor with lower limb length asymmetry. The use of a mobile ergometer led to higher joint acceleration asymmetries. Further studies are necessary to investigate the relation between these findings and muscular adaptations that may increase the risk of lower-back injury.