SAFETY TIP
Make sure that you maintain shoulder contact with the ground. You should not feel pressure on the head or neck when performing this exercise.
VARIATION
Single-Leg Physioball Bridge
This advanced version of the exercise should be initiated after you are able to maintain good control of your hips while performing the bridge exercise. The ultimate goal is to hold the hips in the bridged position, lift one leg for 5 seconds, lower it back to the ball, lift the opposite leg for 5 seconds, and then continue this alteration for 60 seconds.
CHAPTER 7
LEGS
Strong legs are a critical component to reaching your true potential as a swimmer. They are not only the basis for having a powerful and efficient kick but also the key to driving your body off the starting blocks and turn walls. They also play an often overlooked role as a member of the kinetic chain by balancing your stroke mechanics and contributing to a tight streamline.
The lower extremity consists of three major joints—the hip, the knee, and the ankle. Five bones make up the three joints. The pelvis serves as the link between both legs and the torso. Each thigh is composed of a single long bone called the femur. The lower leg contains the tibia and fibula. The talus is the bone that serves as the connecting point between the ankle and lower leg. The hip joint is formed by the bony socket of the pelvis, called the acetabulum, and the head of the femur, which is shaped like a ball. The knee is the junction of the femur and the tibia, and the ankle is composed of the lower ends of the tibia and fibula and the upper part of the talus.
As a ball-and-socket joint, the hip is capable of a wide range of movements that can be described in three pairs. Flexion involves lifting the thigh upward toward the ceiling as if you are lifting your leg to climb a set of stairs. Extension is movement of the thigh backward. Abduction occurs when the leg is moved to the side away from the midline of the body, and adduction is the movement of bringing the leg back toward the midline of the body. Internal rotation is the process of touching the big toe of each foot together along the midline of the body. External rotation is the opposite and allows you to touch the back end of both heels together.
At the knee, a hinge joint, two primary movements occur. Flexion is the process of pulling the heel to the buttocks, and extension is straightening the knee from a flexed position. Four movements take place at the ankle joint. The process of pointing your toes, as you do in a tight streamline, is plantarflexion. Lifting your toes off the ground and toward your shin is called dorsiflexion. Rolling your ankle inward so that the bottom of your foot faces the midline of your body is inversion. Finally, eversion involves twisting your foot outward as you would before initiating a breaststroke kick.
The muscles of the leg can be categorized as those that act on the hip and knee and those that act on the ankle. The thigh and hip muscles can further be categorized into the following groupings: anterior, medial, gluteal, and posterior. Within the anterior grouping are seven muscles. The iliopsoas (figure 7.1 on page 142) is a deep muscle that arises from the anterior aspect of the lumbar vertebrae and the inner aspect of the pelvis and then crosses the hip joint to attach to the proximal femur. The primary movement generated by the iliopsoas is hip flexion. The quadriceps femoris, the largest muscle group in the body, is divided into four separate muscles that are named according to their point of origin. The rectus femoris, the only one to cross both the hip and knee, originates from the anterior aspect of the pelvis. The vastus lateralis arises from the lateral aspect of the femur, the vastus medialis arises from the medial aspect of the femur, and the vastus intermedius is in the middle. All four muscles have a common insertion on the anterior aspect of the tibia through the patellar tendon and function to extend the knee. Because the rectus femoris crosses the hip joint, it also functions as a hip flexor. The tensor fasciae latae (TFL) runs from the anterior aspect of the pelvis to combine with the iliotibial band (IT band), a thickened band of fascial tissue that runs down the lateral thigh. It then inserts on the lateral aspect of the tibia just below the knee joint. The primary actions of the TFL are hip flexion, abduction, and internal rotation. The final muscle of the anterior group is the sartorius, which is a long straplike muscle that runs diagonally from the anterior pelvis to the medial aspect of the tibia. Its primary actions are to flex, abduct, and externally rotate the hip.
The medial grouping can be divided into the adductor muscle family and two additional muscles that lie in close proximity. The adductor family is composed of three muscles (adductor magnus, adductor longus, and adductor brevis), which all arise from the inferior portion of the pelvis near the midline of the body and attach to the medial aspect of the femur. As the name implies, the primary function of this muscle family is hip adduction. Just superior to the adductors is the pectineus, which also originates from the inferior pelvis near the midline of the body and then inserts along the medial aspect of the femur. Besides assisting the adductors, the pectineus also flexes the hip. The gracilis is the most medial and inferior. It has the same origin as the other muscles but crosses the knee to attach on the medial aspect of the tibia just below the knee joint. Besides adducting the hip, the gracilis is also a secondary flexor of the knee.
Figure 7.1 Muscles of the front of the legs.
The gluteal group contains the three gluteal muscles and a collection of six deep rotators. The gluteus maximus (figure 7.2), the largest and most superficial of the gluteal muscles, arises from the posterior half of the pelvis and a portion of an adjacent bone called the sacrum. It then crosses the hip joint to combine with the IT band, also attaching to a small portion of the femur. The main action of the gluteus maximus is extension of the hip. It also assists other muscles in the region with external rotation of the hip. The gluteus medius and minimus both lie deep to the gluteus maximus and arise from the lateral part of the pelvis. The two muscles cross the hip joint, attaching to a bony prominence on the femur called the greater trochanter. Both muscles function to abduct and internally rotate the hip. The deep rotators are a collection of six small muscles (piriformis, gemellus superior, gemellus inferior, obturator externus, obturator internus, and quadratus femoris) that combine to rotate the hip externally and, like the rotator cuff at the shoulder, stabilize the hip joint.
Figure 7.2 Muscles of the back of the legs.
The posterior group is composed of the three hamstring muscles. The biceps femoris, as the name implies, has two heads, one arising from a part of the pelvis called the ischial tuberosity and the other arising from the lower posterior aspect of the femur. The two heads combine to form a common tendon that inserts on the head of the fibula. The other two hamstring muscles, the semitendinosus and semimembranosus, also originate from the ischial tuberosity but run along the medial aspect of the knee joint to attach at the medial surface of the superior part of the tibia. Collectively, the muscles extend the hip and flex the knee.