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.

Tensiomyography Derived Parameters Reflect Skeletal Muscle Architectural Adaptations Following 6-Weeks of Lower Body Resistance Training

“…The BS's ability to activate the full closed kinetic chain, from requirement of torque being produced through multiple joints in the body; whilst maintaining a fixed foot position (Clark et al, 2012;Kwon et al, 2013). Performing BSs has been shown to recruit knee extensor musculature as prime movers alongside the hip, with trunk and back musculature acting in a stability/postural capacity (Caterisano et al, 2002;Schoenfeld, 2010;Marchetti et al, 2016). Conventional deadlifting is also commonly used in lower body RT.…”

Kinematic and Electromyographic Activity Changes during Back Squat with Submaximal and Maximal Loading

“…As a multijoint exercise, the knee extensors (e.g., rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM)) and the hip extensors (e.g., gluteus maximus (GM), biceps femoris (BF), and semitendinosus (ST)) are considered to be the prime movers during squat exercise, with other muscles acting in a secondary capacity [7–9]. …”

Muscle activity of the vastus medialis obliquus during squat motion after static stretching of the tensor fasciae latae

“…Rectus femoris (RF), VMO and VL activities of the right lower extremity were measured using EMG (WEB-7000; Nihon Kohden, Tokyo, Japan). Electrodes for the RF were attached at the midpoint along the line from the anterior spine iliac to the superior border of the patella 11) . Electrodes for the VMO were attached 4 cm superior and 4 cm medial to the superomedial border of the patella at approximately 55° from the long axis of the femur.…”