Frederik Heinen

Muscle-tendon unit scaling methods of Hill-type musculoskeletal models: An overview.

This article gives an overview of the state of the art in scaling methods of generic Hill-type muscle model parameters in view of different applications and implementation of experimental data. This article establishes the requirements used to alter a generic model toward subject-specific musculoskeletal models. This article aims to improve model transparency by a structured description of scaling methods and the associated limitations in musculoskeletal models and highlight the importance of selecting a scaling method supporting the purpose of the model.

Biomechanics of the ski cross start indoors on a customised training ramp and outdoors on snow

An effective start enhances an athletes chances of success in ski cross competitions. Accordingly, this study was designed to investigate the biomechanics of start techniques used by elite athletes and assess the influence of different start environments. Seven elite ski cross athletes performed starts indoors on a custom-built ramp; six of these also performed starts on an outdoor slope. Horizontal and vertical forces were measured by force transducers located in the handles of the start gate and a 12-camera motion capture system allowed monitoring of the sagittal knee, hip, shoulder, and elbow kinematics. The starting movement involved Pre, Pull, and Push phases. Significant differences between body sides were observed for peak vertical and resultant forces, resultant impulse, and peak angular velocity of the shoulder joint. Significantly lower peak vertical forces (44 N), higher resultant impulse (0.114 Ns/kg), and knee joint range of motion (12°) were observed indoors. Although movement in the ski cross start is generally symmetrical, asymmetric patterns of force were observed among the athletes. Two different movement strategies, i.e. pronounced hip extension or more accentuated elbow flexion, were utilised in the Pull phase. The patterns of force and movement during the indoor and outdoor starts were similar.

The effect of medially and laterally wedged insoles on lateral ankle stability during sidestepping movements

Since the start of the study in April 2009, 189 runners were included in the study. A total of 38% (n1⁄4 71) of the subjects completed their participation, whereas 34% (n1⁄4 64) were either excluded from, or dropped out of the study. Currently (1 February 2011), 54 subjects (28%) are actively involved in the study. A total of 35% of the subjects (25 of 71) who completed the study developed an overuse injury. Nine of the 25 runners developed an overuse symptomatic located at the knee joint. Twelve of 25 subjects showed overuse reactions at the foot (e.g. plantar fasciitis, Achilles tendonitis or shin splints). Four subjects developed an overuse injury located at the hip joint. The training logs enabled us to see/showed differences between healthy and injured runners based on the type of training session. Symptomatic runners completed more interval training sessions and competitions. No differences were found for running distance, training frequency and running time per week. Furthermore, no discrepancies were found between the use of neutral or supported footwear or reported running surface. Differences in ankle kinematics were found between the two groups. Significant differences were found in the barefoot condition, for both frontal and sagittal ankle motion, mainly between the nonsymptomatic runners and the runners injured at the knee joint.