The muscles of the lower leg can be grouped according to their actions at the ankle joint. The gastrocnemius and soleus are the primary plantarflexors and share an insertion into the Achilles tendon. The tibialis anterior and posterior, named according to their attachment location on the tibia, function to invert the foot. The fibularis muscle group (fibularis tertius, fibularis brevis, and fibularis longus), located on the lateral aspect of the ankle joint, originates from the fibula and has the primary function of foot eversion.
For discussion purposes, the muscle recruitment patterns of the freestyle and backstroke flutter kick are described jointly because the patterns are practically identical. The propulsive portion of the flutter kick begins with the torso and core-stabilizing musculature acting as the foundation on which your legs generate their force. The actual kicking movements begin with the hips in a small amount of extension. From this extended position the iliopsoas and rectus femoris are activated to initiate hip flexion. Also acting on the knee joint, the rectus femoris initiates knee extension and is quickly joined by the remainder of the quadriceps group, which helps to increase the force produced during the kick. These muscles remain active throughout the entire propulsive phase of the kick. At the ankle joint, the tibialis anterior and tibialis posterior work in concert to maintain the foot in a position of slight inversion, while contraction of the gastrocnemius and soleus plantarflexes the foot. The hip extension that takes place during the recovery phase is guided by the hamstrings and gluteus maximus. Unlike in flutter kicking, during butterfly and dolphin kicking the torso serves not only as the foundation for the kick but also as a component. The undulating body movements of the torso initiate the kick, and paired movements of the legs follow in a manner identical to the action of the flutter kick. One difference in the paired movement of the legs is that a greater amount of flexion and extension occurs at both the hips and knees. The undulating movement of the torso is guided by the contraction of the abdominal and erector spinae muscles, but the muscles that guide the movements of the legs are identical to those used in the flutter kick.
The starting point for the propulsive phase of the breaststroke kick is with the feet 8 to 10 inches (20 to 25 cm) apart and the knees and hips flexed. From this position the TFL, gluteus medius, and gluteus minimus internally rotate and abduct the hips, which results in the legs further separating from each other. As the ankles begin to separate, the biceps femoris contracts, pulling on the outer portion of the lower leg, which externally rotates the lower leg and results in further separation of the ankles. At the same time the fibularis muscle group contracts to evert the foot. These combined movements place the legs in the position to begin the whip portion of the kick. From this position the gluteus maximus contracts forcefully to extend the hip, the quadriceps muscle group functions to extend the knee, and the powerful adductor muscles (adductor magnus, adductor longus, adductor brevis, pectineus, and gracilis) pull both legs back toward the midline of the body. At the ankle joint the tibialis posterior, gastrocnemius, and soleus contract to return the ankle to a streamlined plantarflexed position for the glide portion of the stroke. Recovery is accomplished by recruitment of the rectus femoris and iliopsoas, which serve to flex the hip, and recruitment of the hamstrings, which serve to flex the knee.
Back Squat
Execution
1. Rest the barbell across your upper back and position your feet shoulder-width apart.
2. Initiating the movement with your hips, squat down until your thighs are parallel to the ground.
3. Return to the starting position by straightening your legs.
Muscles Involved
Primary:Rectus femoris, vastus medialis, vastus intermedius, vastus lateralis, gluteus maximus, gluteus medius
Secondary:Erector spinae, biceps femoris, semitendinosus, semimembranosus, adductor magnus, adductor longus, adductor brevis, pectineus, sartorius, gracilis, transversus abdominis, external oblique, internal oblique
SAFETY TIP
Improper squat technique is one of the leading causes of injuries during dryland or weight-room training. Be sure to start with a light weight and add weight only when you have become comfortable with performing the lift and have had a certified strength and conditioning professional review your technique.
Swimming Focus
Squats are a good all-around exercise because they recruit all major muscles groups of the lower extremity. Increasing the strength of the knee extensors transfers to improved force generation and endurance when kicking, regardless of stroke. Strengthening of the gluteal muscles, specifically the gluteus maximus, helps to improve the force that is generated with the extension of the hip during the breaststroke kick. Because of the similarities in the movements performed in squats and starts, particularly flat starts, squats should be a mainstay exercise for enhancing a swimmer’s start.
Extra caution should be used because of the potential for injury to the low back or knees. To protect the low back, beginners should start with just the bar until they are fully comfortable with the exercise. Emphasizing tightening of the core musculature, as described in the introduction to chapter 5, will also help protect the low back. The most common causes for injury to the knee are shifting of the knees forward past the toes or allowing the knees to collapse inward when squatting down.
VARIATION
Overhead Squat
Advantages of overhead squats are that they place a focus on maintaining an upright body posture and develop strength and confidence with the arms in an overhead position. Weight used is much less than in a traditional squat, so starting this exercise with a wooden dowel is best.
Single-Leg Squat
Execution
1. With a dumbbell in each hand, stand 2 feet (60 cm) in front of a flat bench and position your feet hip-width apart.
2. Reach back with one foot and rest your toes on the bench.
3. Initiating the movement with your hips, lower your body until the thigh of the standing leg is near parallel to the ground.
4. Return to the starting position by straightening your leg.
Muscles Involved
Primary:Rectus femoris, vastus medialis, vastus intermedius, vastus lateralis, gluteus maximus, gluteus medius
Secondary:Erector spinae, biceps femoris, semitendinosus, semimembranosus, adductor magnus, adductor longus, adductor brevis, pectineus, sartorius, gracilis, transversus abdominis, external oblique, internal oblique
Swimming Focus
Like double-leg squats, single-leg squats target all the major muscle groups of the lower extremity. An advantage of single-leg squats is that they isolate one leg at a time, which can help address muscle imbalances that may exist between the legs. Targeting all the major muscle groups of the lower extremity improves kicking strength and endurance as well as strength with starts and turns.