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.

The aim of this study was to compare the kinematic profile of on-water and on-ergometer kayaking during maximal paddling. Eleven elite junior female kayak athletes (Mean SD, age: 16.8 ± 1.2 years; body mass: 64.1 ± 8.1 kg) performed a 2-minute maximal kayaking exercise with their competition equipment on water, and a 2-minute maximal kayaking exercise on a standard ergometer. Kinematic data was recorded with an inertial motion capture system. Elbow, shoulder and knee angles and their respective angular velocities were extracted and normalised with respect to the stroke cycle. Statistical Parametric Mapping (SPM) was used to identify statistically significant differences between the two conditions. The stroke rate was significantly higher on ergometer (122.1 ± 6.8 strokes per minute) compared to on water (107.1 ± 4.6 strokes per minute, p < 0.05), with a difference of 8.4 ± 5.9 strokes per minute. Elite kayak female athletes exhibited differences in elbow, shoulder and knee kinematics when comparing on-ergometer to on-water performance. Moreover, the results demonstrated an increased range of motion in lateral bending in the thoracolumbar joint (p < 0.001). The current results support recent findings that a kayak ergometer may not replicate on-water kinematics.

The aim of this study was to generate a subject-specific musculoskeletal muscle model, based on isometric and isovelocity measurements of the whole lower extremity. A two-step optimization procedure is presented for optimizing the muscle-tendon parameters (MTPs) for isometric and isovelocity joint torque profiles. A significant improvement in the prediction of joint torque profiles for both the solely isometric and a combined isometric and dynamic method of optimization when compared to the standard scaling method of the AnyBody Modeling System (AMS) was observed. Depending on the specific purpose of the model, it may be worth considering whether the isometric-only would be sufficient, or the additional dynamic data are required for the combined approach.

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