Bjoern Braunstein

Background: Fast-jet pilots frequently experience high +Gz forces, leading to cervical musculoskeletal adaptations and performance impairments. The biomechanical mechanisms underlying these effects remain unclear. Understanding these biomechanical adaptations is critical to developing preventive measures and ergonomic guidelines aimed at reducing the risk of injury, maintaining pilot health and ensuring long-term operational readiness, and ultimately improving flight safety. Aims: This study compared cervical muscle properties, kinematics and movement-related pain perception between fast-jet pilots and matched non-pilot controls. Methods: Twenty Eurofighter pilots and 20 near-matched non-pilots participated in a cross-sectional comparative study. Muscle tone, stiffness and elasticity were measured using MyotonPRO. Cervical movements were analysed via 3D motion capture. Pain was measured by the Visual Analogue Scale. Statistical group comparisons were performed. Results: No significant differences in cervical range of motion between groups were found (P > 0.05). Pilots exhibited reduced elasticity in the sternocleidomastoid and trapezius muscles (P < 0.05), suggesting neuromuscular adaptation. Increased muscle tone was observed in non-pilots (P < 0.05). Pain perception did not differ significantly (P > 0.05). Conclusions: Pilots maintain normal cervical mobility, compared to non-pilots, despite high-G exposure, but altered muscle properties suggest long-term adaptations. Occupational medicine approaches, including ergonomic cockpit adjustments, targeted physiotherapy, and preventive exercise protocols, are recommended to address cervical muscle adaptations identified in this study. Such strategies could mitigate musculoskeletal strain, enhance pilot wellbeing, and sustain operational safety throughout pilots’ careers.

The cervical spine of fast jet pilots is exposed to high +Gz accelerations during large range of head movements which may lead to biomechanical impairments. The objective of this study therefore was to quantify and analyze the resulting external cervical spine joint moments experienced by fast jet pilots during standardized head movements in real–flight during +5Gz, +7Gz and +9Gz maneuvers. The in– flight helmet orientation recordings and additional ground based motion capture recordings of isolated head movements of seven Eurofighter pilots were processed using a custom made pipeline. Subsequent inverse kinematics and inverse dynamics simulations of the in–flight head movements using individual OpenSim pilot models showed a significant reduction in the head extension angle with increasing +Gz acceleration. Cervical spine joint moments did not change significantly with increasing +Gz acceleration. However, theory–based model analysis indicated that constant head positions under higher +Gz acceleration would lead to an increase in joint moments. The pilots seemed to exhibit reduced head extension at higher +Gz levels, while external joint moments remained relatively constant. Furthermore, the designed pipeline may support individual cervical spine health assessment and monitoring, as well as to inform strength training or rehabilitation programming.

Animals must adapt locomotion to changing environmental conditions, but how the nervous system flexibly controls movement remains unclear. Gravity provides a powerful perturbation because it alters body loading, limb dynamics, and proprioceptive feedback. Apollo astronauts often skipped on the Moon, adopting an asymmetric gait rarely used on Earth, yet the sensorimotor basis of this behaviour is unknown. Here, by studying hypogravity locomotion in humans and mice, we show that reduced gravity reveals a conserved proprioception-dependent mechanism for locomotor state expression. In humans, skipping in simulated lunar gravity is generated through flexible temporal reconfiguration of existing motor modules rather than construction of a new motor architecture. In mice, simulated lunar gravity elicited a skipping-like locomotor state, and genetic elimination of muscle proprioceptors abolished this response. Thus, hypogravity reveals how proprioceptive feedback enables flexible expression of locomotor states.

Technical ability of force application (sagittal force vector orientation) is considered a performance determinant in sprint acceleration, yet the underlying kinematics require further investigation. Sixteen elite male bobsleigh athletes performed unresisted and resisted (85 kg sled push) accelerations initiated with full effort, while ground reaction forces and kinematics were recorded for ground contacts 1 to 5. Ratio of forces (RF), body position, centre of mass velocity components, and lower limb segment rotations were examined for correlations and differences between acceleration tasks. RF was significantly associated with body position (unresisted: r = .82, p < .001; resisted: r = .83, p < .001) and extensional velocity components (unresisted: r = .83, p < .001; resisted: r = .90, p < .001). There was also a significant correlation between body position and extensional velocity component (unresisted: r = .98, p < .001; resisted: r = .84, p < .001) regardless of acceleration task. Shank orientation significantly explained variance in body position (unresisted: adj. R² = .86, p < .001; resisted: adj. R² = .81, p < .001). Resisted acceleration provoked greater RF and forward orientations as well as higher shares of extensional velocity components. To improve technical ability, practitioners should focus on manipulating body position to increase the extensional velocity component as well as on shank segment rotation in preparation for the ground contact phase.

The overall aim in bobsleigh is to minimise the elapsed time required to cover a given distance. A run in bobsleigh consists of a push phase, during which the athletes accelerate and load the bobsl...

Neuromuscular training to strengthen leg muscles is an important part of the treatment of musculoskeletal disorders and chronic diseases and preventing age–related muscle loss. This study evaluates different individualization approaches and their real–time implementation for OpenSim musculoskeletal models to estimate the external knee adduction moment during a leg–press exercise. A robotic neuromuscular training platform was utilized to perform isometric and dynamic leg extension exercises. Data were collected for 13 subjects using a 3D motion capture system and force plate measurements from the robotic training platform. Functional joint parameters, determined through dynamic reference movements, were integrated into the OpenSim models, allowing a personalized representation of the hip, knee, and ankle joints. This integration was compared with a conventional scaling method. The results indicate that the incorporation of functional joint axes can significantly enhance the accuracy of biomechanical simulations. These methods provide a real–time and a more precise estimate of the external knee adduction moment compared to conventional scaling approaches and underscore the importance of individualized model parameters in biomechanical research.

Applying joint position sense tests under different test conditions may introduce reproduction error bias, which can result in different therapeutic consequences. This study investigated the effects of body orientation, movement direction, and limb dominance on the active knee angle reproduction error. Subjects underwent active contralateral knee angle reproduction tests in a seated versus prone position, from a starting point of knee flexion versus knee extension, and with the dominant versus nondominant limb setting the target angle. The test order was randomly determined for each subject. The primary outcome was the absolute active knee angle reproduction error (°). The data of 54 healthy subjects (mean±standard deviation, age: 26±5 years, height: 174±11 cm, body mass: 69.9±14.4 kg, and Tegner activity score: 5.8±1.9) showed that the reproduction error was greater in the seated position than in the prone position. The use of the dominant limb as the reference limb was associated with significantly greater errors in the seated position, but not in the prone position. In conclusion, directly comparing the results obtained in the prone and seated positions is not recommended. However, the dominance of the reference limb might be relevant when testing patients and comparing healthy and injured knees.

The purpose of this work was to provide a fundamental, in-depth analysis of kinematics and kinetics of the bobsleigh push phase to establish a basis for performance analysis and enhancement. Fifteen elite male athletes performed maximal effort push starts, while ground reaction forces (GRF) and 3D marker trajectories were simultaneously recorded for ground contacts of different sub-sections of the push phase (start acceleration phase: first and second ground contact after the initial push-off from the start block, acceleration phase: 10 m and high-velocity phase: 30 m). To obtain a comprehensive view of the push phase, whole-body kinematics as well as joint kinetics were analysed and compared across the push phase. The results showed that propulsion during the start acceleration was hip extensor dominant. With increasing running speed, the contribution to propulsion increased at the ankle and decreased at the knee. In contrast to unresisted sprinting, bobsleigh athletes relied more on mechanical energy generation at the hip than at the ankle, especially during start acceleration. These findings should be considered for the strength and conditioning of bobsleigh athletes and further investigated in relation to a suitable performance measure.

Patients with sarcopenia, who face difficulties in carrying heavy loads, may benefit from collaborative robotic assistance that is modeled after human–human interaction. The objective of this study is to describe the kinematics and spatio-temporal parameters during a collaborative carrying task involving both human and robotic partners. Fourteen subjects carried a table while moving forward with a human and a robotic partner. The movements were recorded using a three-dimensional motion capture system. The subjects successfully completed the task of carrying the table with the robot. No significant differences were found in the shoulder and elbow flexion/extension angles. In human–human dyads, the center of mass naturally oscillated vertically with an amplitude of approximately 2 cm. The here presented results of the human–human interaction serve as a model for the development of future robotic systems, designed for collaborative manipulation.