RESUMEN
INTRODUCTION: The accuracy of muscle and joint contact forces (JCF) estimated from dynamic musculoskeletal simulations is dependent upon the experimental kinematic data used as inputs. Subcutaneous adipose tissue makes the measurement of representative kinematics from motion analysis particularly challenging in overweight and obese individuals. PURPOSE: The purpose of this study was to develop an obesity-specific kinematic marker set/methodology that accounted for subcutaneous adiposity and to determine the effect of using such a methodology to estimate muscle and JCF in moderately obese adults. METHODS: Experimental kinematic data from both the obesity-specific methodology, which utilized digitized markers and marker clusters, and a modified Helen Hayes marker methodology were used to generate musculoskeletal simulations of walking in obese and nonobese adults. RESULTS: Good agreement was found in lower-extremity kinematics, muscle forces, and hip and knee JCF between the two marker set methodologies in the nonobese participants, demonstrating the ability for the obesity-specific marker set/methodology to replicate lower-extremity kinematics. In the obese group, marker set methodology had a significant effect on lower-extremity kinematics, muscle forces, and hip and knee JCF, with the Helen Hayes marker set methodology yielding larger muscle and first peak hip and knee contact forces compared with the estimates derived when using the obesity-specific marker set/methodology. CONCLUSION: This study demonstrates the need for biomechanists to account for subcutaneous adiposity during kinematic data collection and proposes a feasible solution that may improve the accuracy of musculoskeletal simulations in overweight and obese people.
Asunto(s)
Articulación de la Cadera/fisiología , Articulación de la Rodilla/fisiología , Músculo Esquelético/fisiología , Obesidad/fisiopatología , Análisis y Desempeño de Tareas , Caminata/fisiología , Adiposidad/fisiología , Adulto , Fenómenos Biomecánicos , Electromiografía , Femenino , Humanos , MasculinoRESUMEN
Net muscle moments (NMMs) have been used as proxy measures of joint loading, but musculoskeletal models can estimate contact forces within joints. The purpose of this study was to use a musculoskeletal model to estimate tibiofemoral forces and to examine the relationship between NMMs and tibiofemoral forces across walking speeds. We collected kinematic, kinetic, and electromyographic data as ten adult participants walked on a dual-belt force-measuring treadmill at 0.75, 1.25, and 1.50 m/s. We scaled a musculoskeletal model to each participant and used OpenSim to calculate the NMMs and muscle forces through inverse dynamics and weighted static optimization, respectively. We determined tibiofemoral forces from the vector sum of intersegmental and muscle forces crossing the knee. Estimated tibiofemoral forces increased with walking speed. Peak early-stance compressive tibiofemoral forces increased 52% as walking speed increased from 0.75 to 1.50 m/s, whereas peak knee extension NMMs increased by 168%. During late stance, peak compressive tibiofemoral forces increased by 18% as speed increased. Although compressive loads at the knee did not increase in direct proportion to NMMs, faster walking resulted in greater compressive forces during weight acceptance and increased compressive and anterior/posterior tibiofemoral loading rates in addition to a greater abduction NMM.