The comparison between individual 2D modelling and experimental data in squat jumps

• Published in: British journal of sports medicine Vol. 45; no. 15; p. A14
• Main Authors: Cimadoro, G, Babault, N, Alberti, G, Van Hoecke, J, Minetti, A E
• Format: Journal Article
• Language: English
• Published: London BMJ Publishing Group Ltd and British Association of Sport and Exercise Medicine 01.12.2011; BMJ Publishing Group LTD; BMJ Publishing Group
• Subjects: Athletes; Human performance; Muscular system; Simulation; Tendons
• ISSN: 0306-3674; 1473-0480
• DOI: 10.1136/bjsports-2011-090606.44

Intra-individual simulation needs accurate data about actuators (muscles) and force transmission (bones, joints) for obtaining accurate predictions. That work preludes to a more comprehensive 2D jump simulator, dealing with the estimation of squat jump parameters based on maximum torque measurements. An individual male athlete was investigated. The maximum torque (T, Nm) of hip, knee and ankle joints extensor muscles was measured by a dynamometer (Quickset 4, Biodex Medical System In., US) at different angles (φ, deg) and at different positive and negative angular speed (ω, deg/s). After correcting the positional data for real bone alignment (Tsaopoulos et al.2011), a suitable equation describing the 3D surface (T vsφ vs ω) of each muscle group. The subject was also tested for vertical ground reaction force and kinematics during maximal squat jumps and during 1RM ‘half back squat', starting at 90° knee angle. The predicted outcomes were obtained by a software simulation of squat jump (Working Model 2D, Knowledge Revolution, US) where the model included anthropometric and inertial characteristics of body segments according to Chandler (1975), with a delay among actuators following Pandy et al (1991). Simulation versus experimental data showed that the model accurately reproduces: a) half back squat 1RM (1374 vs 1422–1511 N range), and b) maximal squat jump (peak force of 2009 vs 1580–1965 N range, toe-off speed of 2.17 vs 2.12 m/s, jump height 0.23 vs 0.23 m, respectively). The model was further tested by allowing different start angles of the jump. As expected, results showed a decrease of the toe-off speed as the knee angle increases. A more comprehensive model including the effect of elastic structures in the limbs (tendons, foot arch, etc) and measured anthropometric values will provide more accuracy. From the comparison between detailed model outcomes and subject performance, the effects of a given athlete conditioning strategy will be tested.