Speaker #0Hi and welcome to Biopolites Deep Dive. Have you ever thought about what happens when the same muscle has to contribute to hip extension while maintaining the knee inflection? This is precisely one of the biomechanical challenges of airplane prep on the Cadillac, an exercise that combines movement of the femurs on the pelvis, lumbopelvic stabilization, and sequential articulation of the spine. However, we are going to focus primarily on two muscles that are sometimes not clearly differentiated within the hamstring group, the semitendinosus and the semimembranosus. We will examine their origins, insertions, actions, innervation, and, most importantly, the consequences of their biarticular nature in this exercise. To begin, you are lying supine with your head toward the roll-down bar. The arms are extended overhead and the hands are braced against the uprights of the Cadillac, slightly above shoulder level. Be careful. The arms are not there to pull the body upward. Their main purpose is to prevent the body from sliding along the table as the resistance of the springs changes. The scapulae remain stabilized against the ribcage but without excessive rigidity. The neck stays long and the cervical spine is not stretched. spine continues the line of the thoracic spine. The pelvis and spine are in a neutral position. The legs are hip distance apart. The knees are flexed and hooked over the bar so that the bar rests behind the knees. The ankles are plantar flexed and the toes are gently pointed. This position already requires precise organization. The weight should be distributed symmetrically behind both knees. The femurs remain parallel. and the pelvis should not be pulled into rotation or lateral tilt. Inhale to prepare for the movement. As you exhale, maintain the pelvis in neutral and extend the hips to direct the toes toward the table. The legs move away from the torso, but the movement comes from the hip joints. It should not be achieved by increasing the lumbar lordosis or thrusting the ribs toward the ceiling. As you inhale, Flex the hips to bring the legs closer to the torso while controlling the return of the bar. On the next exhalation, keep the hips and knees flexed. Then begin articulating the spine from the coccyx. The pelvis tilts, the sacrum leaves the table, and each vertebra gradually peels away. Continue upward until the weight is supported on the upper thoracic spine, but never on the cervical spine. Finally, As you inhale, gradually articulate the spine back onto the table from the thoracic region toward the sacrum until the pelvis returns to neutral. It is essential to allow the sacrum to return fully to the table before beginning the next hip extension. The hamstrings contribute to both hip extension and knee flexion. In airplane prep, they work with the gluteus maximus to direct the toes toward the table. During this first phase, they perform a concentric action at the hip. When the legs return toward the torso, the hips flex. The hamstrings do not simply relax. They control the return eccentrically. This control prevents the springs from bringing the legs back toward the body too quickly. At the same time, the angle of the knees should remain almost constant. The hamstrings therefore also have an important stabilizing role at the knee. In this situation, their action includes an isometric component that maintains contact between the backs of the knees and the bar. Let us begin with the semitendinosus. It originates from the ischial tuberosity through a common tendon with the long head of the biceps femoris. It then travels down the posterior and medial part of the thigh. As its name suggests, a significant portion of its length consists of tendon. which is particularly visible in its distal portion. It inserts onto the upper part of the medial surface of the tibia. Its tendon joins those of the sartorius and gracilis to form the pes anserinus. The semitendinosus extends the hip, flexes the knee, and when the knee is flexed, medially rotates the tibia. It is innervated by the tibial division of the sciatic nerve. primarily through the L5, S1, and S2 nerve roots. In airplane prep, the semitendinosus therefore contributes to hip extension as the toes move toward the table. However, because the knees remain flexed, it also helps maintain their angle. Its role is not to increase knee flexion, but to create enough tension to keep the bar properly positioned. The semimembranosus lies deeper than the semitendinosus. It originates from the supralateral part of the ischial tuberosity. Its proximal portion is broad and flattened, which explains the name semimembranosus. It inserts primarily onto the posterior surface of the medial condyle of the tibia. Some of its tendinous expansions extend toward the posterior and medial structures of the knee, particularly the oblique popliteal ligament. Like the semitendinosus, it extends the hip, flexes the knee, and medially rotates the tibia. when the knee is flexed. It is also innervated by the tibial division of the sciatic nerve with primary contributions from the L5, S1, and S2 nerve roots. The semimembranosus and semitendinosus therefore form the medial hamstrings. Their insertion on the medial side of the tibia explains their ability to produce medial rotation of the leg. In airplane prep, however, this rotational action should not become dominant. If these muscles work asymmetrically, one knee may move inward, one foot may change direction, and the pelvis may begin to rotate. It is therefore important to maintain equal pressure behind both knees and keep the legs parallel. The semitendinosus and semimembranosus are biarticular muscles. This means that they cross two joints, the hip joint and the knee joint. their length and their ability to produce force. therefore depend simultaneously on the position of both joints. With the exception of the short head of the biceps femoris, the hamstring muscles cross both the hip and the knee. When the hip flexes, the hamstrings lengthen proximally. When the hip extends, they shorten. When the knee extends, they lengthen distally. When the knee flexes, they shorten in that same distal region. In airplane prep, we combine hip extension With a knee that remains flexed, the hamstrings therefore shorten at the hip while they are already shortened by knee flexion. This combination may bring them closer to a position known as active insufficiency. The muscle becomes so shortened across both joints that it gradually becomes less effective at producing additional force. The force-producing capacity of the hamstrings does indeed vary according to the type of hamstring. to the combination of hip and knee angles. This is one of the reasons why the gluteus maximus is so important during this phase of airplane prep. The hamstrings should not be expected to do everything on their own. The gluteus maximus plays a major role in hip extension, while the hamstrings contribute to the movement and maintain the relationship between the pelvis, femur, and knee. For some people, excessive knee flexion combined with a large amount of hip extension may create a sensation of tightness or cramping in the backs of the thighs. The solution is not necessarily to push harder, but often to reduce the range of motion, distribute the effort more effectively through the gluteal muscles, and maintain fluid breathing. Maintaining a constant knee angle is one of the essential focus points of the exercise. If the knees flex further as the hips extend, The semitendinosus and semimembranosus shorten simultaneously across both joints. The quality of hip extension decreases and the bar may shift position. If the knees extend, the bar may slip and the relationship between the legs and the springs becomes unstable. The cue can therefore be very simple. Maintain the shape of your legs. The thighs move at the hips but the angle of the knees does not change. You can also ask the practitioner to imagine that the back of each knee gently molds around the bar without crushing it. Once the legs have returned close to the torso, the second part of the exercise begins, spinal articulation. At this point, the hamstrings should no longer lift the pelvis by increasing hip extension. The legs should remain close to the torso with the hips and knees flexed. The articulation is initiated by the abdominals, particularly the obliques and rectus abdominis. The transversus abdominis helps compress the abdominal region and stabilize the lumbopelvic area. The pelvic floor supports this deep organization. The pelvis curls and then the spine sequentially peels away from the table, from the coccyx toward the thoracic region. Avoid extending the hips again to increase spring tension and then using that tension as momentum to lift the torso. This would bypass the objective of the exercise. The arms brace against the uprights to prevent the body from sliding, but they do not pull the body upward. The four most common mistakes. The first mistake is arching the lower back as the toes move toward the table. In this case, the practitioner is confusing hip extension with lumbar extension. The cue can be Keep the sacrum heavy. The legs move away from the pelvis without the ribs lifting. The second mistake is changing the angle of the knees. The bar may then slip or the tension may become uneven between the two legs. The third mistake is using hip extension to initiate the articulation of the pelvis. The legs must first return close to the torso. Only then should the spine begin to curl. The fourth mistake. is rolling too far and transferring the weight onto the neck. The movement should stop on the upper thoracic spine. Finally, watch for asymmetries. Greater pressure behind one knee may reveal a difference in muscle recruitment between the two sides. The pelvis may then rotate and the bar may move laterally. If pelvic stability cannot be maintained in neutral as the hips extend, a slight imprinted position may be used. This adaptation does not mean pressing the lumbar spine forcefully into the table. It reduces the depth of the lumbar curve and improves abdominal control when neutral cannot yet be maintained with sufficient stability. The first modification is to perform only the leg movement. The sacrum remains on the table. As you exhale, extend the hips. and direct the toes toward the table. As you inhale, bring the legs back toward the torso. This version specifically trains the concentric and then eccentric action of the hip extensors. The second modification is to perform only the spinal articulation. The hips remain flexed, with the knees close to the torso. As you exhale, articulate the spine from the coccyx toward the thoracic region. As you inhale, gradually return the spine to the table. This version removes any potential momentum coming from the legs and provides a clear understanding of the role of the abdominals. Airplane prep is therefore not simply an exercise in which the legs move away and the pelvis is then lifted. It teaches us to distinguish several functions that must nevertheless remain coordinated. The gluteus maximus and hamstrings. produce hip extension. The semitendinosus and semimembranosus also help maintain knee flexion. The abdominals organize the spinal articulation. The scapular stabilizers maintain the relationship between the shoulder girdle and the rib cage, and the arms prevent the body from sliding without becoming the primary movers of the exercise. Understanding the biarticular nature of the semitendinosus and semimembranosus. allows us to observe the movement more accurately. We understand why the knee angle must remain constant, why the gluteus maximus must contribute to hip extension, and why excessive tension in the backs of the thighs does not always mean that the practitioner needs to push harder. In airplane prep, the difficulty does not come from strength alone. It comes from the ability to distribute that strength precisely Thank you. Control the springs and allow each region of the body to fulfill its own role. See you very soon for another exploration of movement, anatomy, and biomechanics applied to Pilates.
