title: Muscle Activation Differs between Three Different Knee Joint-Angle Positions during a Maximal Isometric Back Squat Exercise.
abstract: The purpose of this study was to compare muscle activation of the lower limb muscles when performing a maximal isometric back squat exercise over three different positions. Fifteen young, healthy, resistance-trained men performed an isometric back squat at three knee joint angles (20°, 90°, and 140°) in a randomized, counterbalanced fashion. Surface electromyography was used to measure muscle activation of the vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF), biceps femoris (BF), semitendinosus (ST), and gluteus maximus (GM). In general, muscle activity was the highest at 90° for the three quadriceps muscles, yet differences in muscle activation between knee angles were muscle specific. Activity of the GM was significantly greater at 20° and 90° compared to 140°. The BF and ST displayed similar activation at all joint angles. In conclusion, knee position alters muscles activation of the quadriceps and gluteus maximus muscles. An isometric back squat at 90° generates the highest overall muscle activation, yet an isometric back squat at 140° generates the lowest overall muscle activation of the VL and GM only.
authors: Graduate Program in Science of Human Movement, College of Health Science (FACIS), Methodist University of Piracicaba, 13423-070 Piracicaba, SP, Brazil; Institute of Orthopedics and Traumatology, School of Medicine, University of São Paulo, Laboratory of Kinesiology, 05403-000 São Paulo, SP, Brazil.
authors: Paulo Henrique
authors: 0000-0002-2016-936X
authors: PH
authors: Marchetti
authors: Graduate Program in Science of Human Movement, College of Health Science (FACIS), Methodist University of Piracicaba, 13423-070 Piracicaba, SP, Brazil.
authors: Josinaldo
authors: J
authors: Jarbas da Silva
authors: Department of Health Sciences, Program of Exercise Science, CUNY Lehman College, Bronx, NY 10468, USA.
authors: Brad
authors: B
authors: Jon Schoenfeld
authors: Institute of Orthopedics and Traumatology, School of Medicine, University of São Paulo, Laboratory of Kinesiology, 05403-000 São Paulo, SP, Brazil.
authors: Priscyla Silva Monteiro
authors: PS
authors: Nardi
authors: Graduate Program in Science of Human Movement, College of Health Science (FACIS), Methodist University of Piracicaba, 13423-070 Piracicaba, SP, Brazil.
authors: Silvio Luis
authors: SL
authors: Pecoraro
authors: Institute of Orthopedics and Traumatology, School of Medicine, University of São Paulo, Laboratory of Kinesiology, 05403-000 São Paulo, SP, Brazil.
authors: Julia Maria
authors: JM
authors: D'Andréa Greve
authors: Department of Physical Therapy, University of New England, Portland, ME 04103, USA.
authors: Erin
authors: E
authors: Hartigan