title: Kinematic, kinetic and EMG patterns during downward squatting.
abstract: The aim of this study was to investigate the kinematic, kinetic, and electromyographic pattern before, during and after downward squatting when the trunk movement is restricted in the sagittal plane. Eight healthy subjects performed downward squatting at two different positions, semisquatting (40 degrees knee flexion) and half squatting (70 degrees knee flexion). Electromyographic responses of the vastus medialis oblique, vastus medialis longus, rectus femoris, vastus lateralis, biceps femoris, semitendineous, gastrocnemius lateralis, and tibialis anterior were recorded. The kinematics of the major joints were reconstructed using an optoelectronic system. The center of pressure (COP) was obtained using data collected from one force plate, and the ankle and knee joint torques were calculated using inverse dynamics. In the upright position there were small changes in the COP and in the knee and ankle joint torques. The tibialis anterior provoked the disruption of this upright position initiating the squat. During the acceleration phase of the squat the COP moved posteriorly, the knee joint torque remained in flexion and there was no measurable muscle activation. As the body went into the deceleration phase, the knee joint torque increased towards extension with major muscle activities being observed in the four heads of the quadriceps. Understanding these kinematic, kinetic and EMG strategies before, during and after the squat is expected to be beneficial to practitioners for utilizing squatting as a task for improving motor function.
authors.affiliation: Laboratory of Clinical Studies in Physical Therapy, University of Ribeirão Preto, Ribeirão Preto, Brazil. vcdionisio@gmail.com
authors.forename: Valdeci Carlos
authors.initials: VC
authors.lastname: Dionisio
authors.forename: Gil Lúcio
authors.initials: GL
authors.lastname: Almeida
authors.forename: Marcos
authors.initials: M
authors.lastname: Duarte
authors.forename: Rogério Pessoto
authors.initials: RP
authors.lastname: Hirata
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000502:physiology; D001696:Biomechanical Phenomena / Q000379:methods; D004568:Electrodiagnosis / Q000379:methods* / Q000706:statistics & numerical data; D004576:Electromyography / Q000379:methods / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007700:Kinetics; D007719:Knee Joint / Q000502:physiology; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009068:Movement / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology; D011187:Posture; D012016:Reference Values; D012815:Signal Processing, Computer-Assisted; D013334:Students; D013997:Time Factors