Spinal Muscles & Function
The erector spinae group and transversospinales group share this general line of action on the spine.
What is extension and ipsilateral lateral flexion of the trunk and neck?
The external obliques and internal obliques rotate the trunk in opposite directions. Describe the pattern.
What is external oblique = contralateral rotation; internal oblique = ipsilateral rotation?
The iliopsoas group acts concentrically during this phase of walking.
What is hip flexion during the swing phase?
The quadriceps perform this primary function at the knee and lose about 20% of their strength without this bone.
What is knee extension, and the bone is the patella?
Define isometric contraction and provide a functional example involving the trunk.
What is muscle tension without joint movement, such as holding a plank position?
The multifidi and rotatores assist in rotation. Which direction do they rotate the trunk relative to their contraction side?
What is contralateral rotation?
During a reverse crunch, which abdominal muscle group primarily produces the posterior pelvic tilt, and what contraction type is used?
What are the rectus abdominis and obliques, acting concentrically?
The gluteus maximus and hamstrings share this primary concentric action at the hip joint.
What is extension of the thigh?
The popliteus initiates this motion to unlock the knee from full extension.
What is medial rotation of the tibia?
During the landing phase of a vertical jump, what type of contraction occurs in the hip and knee extensors, and why?
Eccentric contraction to absorb impact and decelerate body mass.
During controlled trunk flexion (as when lowering into a forward bend), the erector spinae perform what type of contraction, and why?
What is an eccentric contraction, to control the descent against gravity?
The transversus abdominis compresses the abdominopelvic cavity. How does this function contribute to spinal stability?
By increasing intra-abdominal pressure, creating a stabilizing corset effect around the spine.
The gluteus medius and minimus perform this motion in the frontal plane, and prevent this gait abnormality.
What is hip abduction; prevents contralateral pelvic drop (Trendelenburg gait)?
The gastrocnemius crosses two joints. Describe its dual actions.
What is plantarflexion at the ankle and flexion at the knee?
Explain how gravity determines whether a muscle works concentrically or eccentrically during movement.
If the muscle moves against gravity, it’s concentric; if it controls gravity’s pull, it’s eccentric.
The splenius capitis and splenius cervicis differ from the semispinalis capitis in this way during rotation.
What is that they rotate the head ipsilaterally, whereas the semispinalis rotates contralaterally?
In a supine leg lower, which muscle group works eccentrically to control hip extension and prevent lumbar arching?
What are the abdominal muscles, primarily rectus abdominis and obliques?
The tensor fasciae latae and gluteus medius can both abduct the hip. How do their secondary actions differ?
The TFL medially rotates and flexes, while the gluteus medius laterally rotates and extends (posterior fibers).
The fibularis longus and brevis both evert the foot. Which additional ankle motion do they assist with, and why?
What is plantarflexion, because their tendons pass posterior to the lateral malleolus?
Describe the reverse action of the hip flexors during a sit-up movement.
Instead of lifting the leg, the hip flexors tilt the pelvis anteriorly and flex the trunk toward the thighs.
When performing a side bend holding a weight in the right hand, which spinal muscles are active and on which side?
What are the right-side lateral flexors (erector spinae, obliques, quadratus lumborum) working concentrically?
Explain why training “core movements” rather than isolated muscles (like the transverse abdominis) is biomechanically superior.
Because spinal stabilization arises from coordinated multi-muscle activation patterns, not isolated muscle recruitment.
Explain how the adductor magnus can act as both an adductor and an extensor of the thigh.
Because its anterior fibers adduct/flex, while its posterior fibers attach to the ischial tuberosity and extend the hip.
In a calf raise, compare the roles of the gastrocnemius and soleus in terms of knee position and muscle fiber type.
The gastrocnemius is active with knee extension, more fast-twitch; the soleus works with knee flexion, more slow-twitch postural fibers.
During a Romanian deadlift, which hip muscles act eccentrically, and what is the functional benefit of this control?
The gluteus maximus and hamstrings, eccentrically controlling descent to store elastic energy and stabilize the pelvis.