Movement Analysis of the Freestyle Stroke in Swimming

Abstract

In swimming, the freestyle stroke is one of the most frequently used movements. This movement takes years to learn and execute efficiently and powerfully. It is a movement that is unnatural and quite awkward to perform at first for most athletes. Constant practice is necessary for proficiency in this skill. Understanding the mechanics of this movement will ensure that coaches can teach this complex multi-joint exercise. Learning how the body's mechanical forces interact in this movement is crucial for strength and conditioning coaches to build their athletes for this specific movement. Physiotherapists, sports surgeons, and athletic trainers should learn the mechanics of this skill so that they can better aid their athletes. Overall, this movement is one of extreme complexity that involves resistance, balance, and multiple joints and muscles acting in various planes of motion. One such crucial joint and muscle interaction for the freestyle stroke is the movement of thoracic rotation.

Keywords: swimming, freestyle, movement analysis, streamline

Movement Analysis of the Freestyle Stroke in Swimming

Introduction

In swimming and other sports, such as water polo, the freestyle stroke is one of the most used movements. It is the fastest stroke in swimming and essentially the only stroke used in water polo. This stroke is not the most challenging type to master. However, it is often the first learned, and it takes athletes years to become truly efficient. One of the most difficult aspects of this movement is creating balance in the water while counteracting the resistance of water to propel oneself forward.

Swimmers face several unique challenges that athletes in most land-based sports rarely encounter. The first challenge is the total body nature of all four competitive strokes, which involve movements of both the upper and lower extremities. A coordinated effort of the musculoskeletal system is required to keep each body part moving correctly to maximize movement efficiency through the water. (McLeod 1, 2010)

As described by Ian McLeod in his book Swimming Anatomy, another critical challenge to swimming is the effort to stay efficient in the water. This task requires full body integration to create stability and power in the water. In the freestyle stroke, contralateral superior and inferior limb movements co-occur while being stabilized by the core. Practitioners see this when the right arm is reaching forward, or in the 'recovery phase', the left arm is pulling water while the left leg is kicking in succession with the right leg. The freestyle stroke heavily uses the glenohumeral joint, the shoulder girdle, the elbow joint, the hip joint, and the tibiofemoral joint. Muscles crucial to propulsion creation in the freestyle stroke are the latissimus dorsi, pectoralis major, triceps brachii, iliopsoas, rectus femoris, the hamstrings, the gluteal muscles, and quadriceps group. Many muscles are also heavily used as stabilizers in this complex movement. Due to the exercise's medium, the body must constantly work to maintain stability. Muscles crucial in this are the core stabilizers, such as the transversus abdominis, rectus abdominis, obliques, and the erector spinae. Furthermore, shoulder girdle stabilizers such as the rhomboids, lower trapezius, serratus anterior, and pectoralis minor control this powerful movement.

Athletes with highly developed control of these muscles and their joint actions tend to have the best and most efficient freestyle strokes. A well-developed freestyle stroke tends to look effortless. Athletes with this level of ability in this movement can reduce drag in the water, pull maximal amounts of water with each stroke, kick consistently and efficiently, and stay in control of their body as much as possible to create maximal hydrodynamic efficiency. Swim coaches focus on these concepts through drills and instruction. These drills teach timing, stroke mechanics, breathing patterns, reduction of drag and strength, and 'feel' in the water. Overall, understanding the movement of freestyle and its constituent muscles and joints will aid a coach in coaching this complex skill.

Movement Phases

Stance Phase

Because the freestyle stroke does not take place on land, the term 'stance phase' is better thought of as a position just before the athlete gets into the streamline or preparatory phase position. For the context of this paper, the stance phase will be considered the push-off portion of the freestyle stroke. Although this phase requires some eccentric and concentric contraction, it is the movement that occurs directly before the preparatory phase. That preparatory phase contains joint actions that truly prepare the body for the freestyle stroke, such as the lengthening of the latissimus dorsi, the plantar flexion of the talocrural joint, and the stabilization of the lumbar spine to create balance in the water.

In this stance phase, the body performs a horizontally oriented squat jump off the pool wall with the arms overhead in a streamlined position. The lower body will achieve a squat jump type of progression to start this movement. This squat jump is an open chain-style movement because the hands are not fixed to an object, although they are pushing through the resistance of the water. According to the textbook Manual of Structural Kinesiology, the squat is "separated into two phases for analysis: (1) lowering phase to the squatted position and (2) lifting phase to the starting position." In a squat jump or pushing off the wall in swimming, there is slightly more movement in the second phase, which involves leaving the contact surface. In the lowering phase, the trunk maintains extension by isometrically contracting the erector spinae and quadratus lumborum. The hip and knee lower into flexion through the eccentric contraction of the gluteus maximus, semimembranosus, semitendinosus, biceps femoris, rectus femoris, vastus medialis, vastus intermedialis, and vastus lateralis. In this lowering phase, the ankle moves into dorsiflexion through the eccentric contraction of the gastrocnemius and soleus. In the standing and lifting phase, the hip and knee flexors previously mentioned move into an explosive concentric contraction. The trunk stays in its isometric contraction to maintain core stability, and the ankle moves into plantar flexion. This plantarflexion is essential to provide the last part of the force crucial for leaving the wall in the push-off.

The upper body does much more in this movement than in a regular squat. This position can be considered a facedown position with arms overhead throughout the push-off. Both shoulder joints are in one hundred and eighty degrees of forward flexion and abduction. The shoulder girdle is in scapular elevation and scapular upward rotation in this phase of the movement. This arms overhead position with arms parallel and in line with the ears and hands stacked is known as the streamlined position in swimming. The stacked position refers to one hand being on top of the other. The streamline creates an arrow-like formation that pierces through the water effectively. To achieve this arm overhead stacked streamline position, the body will recruit the serratus anterior, the rhomboids, the trapezius muscles, the pectoralis minor, the medial fibers of the deltoid, the levator scapulae, and the pectoralis major. All these muscles will work together to forwardly flex and abduct the shoulders and elevate and upwardly rotate the scapula. The elbows are in an extended position via the flexion of the triceps brachii. The radioulnar joint is in a pronated position in this streamline or 'stance' phase. One hand is stacked over the other, requiring slightly more shoulder flexion out of one side of the body than the other. The wrist is in a neutral position, with the fingers and thumb in an adducted position. These wrist and finger joints are also slightly extended to up to five degrees, if at all.

Preparatory Phase

This movement phase directly follows the stance phase, and the only significant difference between these two initial phases is the straightening of the legs. In this position, the hip joint is in a neutral position. The tibiofemoral joint is in a neutral position, and the talocrural joint is ideally in fifty degrees of plantarflexion. This plantarflexion allows the kick to be more powerful throughout the future stages of the movement. Plantar flexion occurs via the flexion of the gastrocnemius and soleus.

As for the trunk and spine, the neck is in a neutral position with slight capital flexion to keep the head down and in a hydrodynamic position. The lumbar region is neutral; however, due to the overactive nature of the iliopsoas for most swimmers, the lumbar spine tends to be slightly extended in this phase of the movement. In this preparatory phase of streamlining, many stabilizers within the core are constantly working to maintain balance and buoyancy. The muscles working in the trunk to achieve this isometric contraction are the transverse abdominis, external oblique, erector spinae, iliopsoas, quadratus lumborum, and rectus abdominus.

Along with these lower extremity joints and trunk positioning, the shoulder girdle, glenohumeral joint, elbow joint, and radioulnar joints are in the exact positioning as the stance phase. The only difference is that the hands are removed from the stacked streamline position just before the next movement step and moved into an eleven-streamline. This eleven-streamline position is where the hands are parallel to each other and in line with the ears. The radioulnar joint is still in pronation. To move from the stacked streamline position to the eleven-streamline, one must slightly adduct the shoulders using the latissimus dorsi, the pectoralis major, and other shoulder adductors. Overall, the joints' muscles in and around the shoulder are in a preparatory position. Specifically, the latissimus dorsi will be stretched and effectively primed in this phase to prepare for the next step of pulling through the water.

Movement Phase

Within swimming, the movement phase is referred to as the pull phase. From the position of the streamline, the pull phase starts with one arm pulling down through the water towards the hip. While one arm pulls, the other is still outwardly stretched forward in preparation for its pull phase. As this downward and backward pull occurs, the simultaneous spinal rotation allows the body to cut hydrodynamically through the water, and both legs are repeatedly executing the 'flutter kick.'

Using the right arm as an example of this catch phase of the movement, the joint and muscle actions are as follows. In the upper body, the glenohumeral joint, shoulder girdle, lumbar spine, and elbow joint do most of the moving in this phase. Initially, in the glenohumeral joint, the arm extends via the initial contraction of the pectoralis major, with the latissimus dorsi contracting shortly after that. These two muscles do most of the moving through this phase. During this, the shoulder girdle is also moving through downward rotation and depression through the action of the pectoralis minor, the rhomboid's lower fibers, and the trapezius's lower fibers.

The elbow becomes slightly bent at about one-third of the pull. The elbow flexion angle here varies by swimmer but is usually around ten to twenty degrees. This elbow flexion takes place via the contraction of the biceps brachii, brachialis, and brachioradialis. During this elbow flexion, the shoulder is still moving in its extension towards the hip, and the radioulnar joint stays in a pronated position. This elbow flexion and radioulnar pronation create a large surface area to pull water.

As this arm reaches the hip, the elbow begins to extend via the triceps brachii and anconeus contraction. During this phase of the pull, the lumbar region of the spine starts to rotate to allow the other arm to stay straight while keeping the body in a relatively prone position on the surface of the water. The erector spinae and internal and external oblique all work together to unilaterally rotate the spine in this pull phase. At the end of the pull, the elbow reaches full extension as the glenohumeral joint comes into backward extension. With this, the wrist joint moves into flexion to finish the movement. Shoulder and elbow extension is achieved through contraction of the posterior fibers of the deltoid and the elbow extenders. Wrist flexion is made possible by the contraction of the wrist flexors, such as the flexor carpi radialis, the flexor carpi ulnaris, and the palmaris longus.

The flutter kick is also occurring while this arm pull is happening, thus making this movement a challenging full-body exercise that continues to require the stabilization of the core by the muscles mentioned above. The kick occurs rapidly in the lower extremities, with one leg kicking downward while the other kicks upwards. The downward kick initiates through flexion at the hip joint, extension at the tibiofemoral joint, and plantarflexion at the ankle joint. Hip flexors such as the iliopsoas, the pectineus, the rectus femoris, and the sartorius create hip flexion in this downward kick. Tibiofemoral extension occurs through the muscular contraction of the quadriceps muscles, such as the rectus femoris, vastus medialis, vastus intermedius, and vastus lateralis. After the downward flutter kick comes the upward portion of the kick. The upward kick consists of hip extension, tibiofemoral flexion, and ankle plantarflexion. Hip extension happens by intense contraction of the gluteus maximus. Flexion at the knee, or tibiofemoral joint, occurs via contraction of the hamstrings, such as the biceps femoris, the semimembranosus, and the semitendinosus. This cycle of upward and downward kicking repeatedly happens throughout the freestyle movement.

Follow-through Phase

The follow-through phase is known as the recovery phase within the context of the freestyle stroke. Throughout this phase, the flutter kick continues. In this movement phase, muscles in the shoulder girdle and glenohumeral joint work to move the arm and hand into another pull phase. The arm ends the pull phase by exiting the water. In this recovery or follow-through phase, it moves towards the water in front of the head. Most swimmers use a 'bent arm' recovery, where the elbow flexes as it moves forward. This elbow flexion takes place via the contraction of the biceps brachii, brachialis, and brachioradialis. As the arm reaches forward, the glenohumeral joint goes through internal rotation, horizontal adduction, and flexion. These are all achieved by actions taken by the deltoid fibers and the rotator cuff. The rotator cuff muscles of the supraspinatus, infraspinatus, teres minor, and subscapularis work incredibly hard during the freestyle stroke because of this repeated action. Within the shoulder girdle, the body will recruit the serratus anterior, the rhomboids, the trapezius muscles, the pectoralis minor, the medial fibers of the deltoid, the levator scapulae, and the pectoralis major. All these muscles will work together to forwardly flex and abduct the shoulders and elevate and upwardly rotate the scapula to return the arm to a streamlined-eleven position. While the arm is in the middle of this recovery phase, the other arm is going through its pull phase. As Ian McLeod writes in Swimming Anatomy on page three, "The arm movements during freestyle are reciprocal in nature, meaning that while one arm is engaged in propulsion, the other is in the recovery process." Thus, the cycle repeats and propels the swimmer across the pool while continually moving through the flutter kick.

Conclusion

The freestyle movement is one of significant individual variability, but generally, it is done similarly across cultures and age groups. This similitude is because this specific sequence of coordinated movements is the fastest and most efficient way to move through the water. Again, this movement is unnatural and leads to an increased strain on the structures surrounding the shoulder. However, it leads to increased strength in the major muscles of the action, such as the pectoralis major, the latissimus dorsi, the hip flexors, and the quadriceps. Understanding the biomechanical requirements of this movement can help coaches and trainers better prepare their swimmers. Coaches and trainers can use this information to create training programs focusing on the major muscle groups involved in freestyle and injury prevention programs that will decrease the risk of injury in swimmers that focus on the freestyle.

References

Floyd, R. T., & Thompson, C. W. (2018). Manual of Structural Kinesiology (20th ed.). New York, NY: McGraw-Hill Education.

McLeod, Ian. Swimming Anatomy: Your Illustrated Guide for Swimming Strength, Speed, and Endurance. Human Kinetics, 2010.