MSR Freestyle Swimming, Part 4: Flutter Kick and Lower-Limb Coordination
The flutter kick is the alternating up-and-down leg action used in freestyle swimming. It contributes to propulsion, body position, and coordination with the arm stroke. Its demands vary with pace, distance, and technique, from a restrained distance-swimming rhythm to the faster kicking used during sprint efforts.
Parts 1–3 examined arm action, shoulder support, and trunk function. Here, we explore how hip movement, knee motion, and ankle position work together, with particular attention to the downbeat. For practitioners, understanding these relationships helps connect examination findings with MSR treatment and physical preparation that support the swimmer’s goals.
Article Index
Understanding the Flutter Kick
The flutter kick is the alternating leg action used in front crawl. As one leg moves downward, the other moves upward, with coordinated motion through the hips, knees, ankles, and feet. The kick contributes to propulsion and helps manage body position and rotation alongside the arm stroke.
A Continuous Alternating Action
The downbeat describes the foot moving toward the pool floor; the upbeat describes its return toward the surface. Body roll changes the orientation of these movements, so the legs do not always travel in a strictly vertical plane.
Movement develops through the limb rather than occurring at one joint alone. Hip motion leads into changing knee position, while the ankle and foot respond to muscular activity and water resistance. The knee bends and straightens through the cycle; an effective kick does not require a rigidly straight leg.
The feet generally remain plantarflexed, with the toes directed away from the shin. Available ankle movement helps the foot accommodate the water, but forcefully holding the toes pointed is different from maintaining a supple ankle during repeated kicking.
Timing With the Arm Stroke
Swimmers use different kicking rhythms. A two-beat kick involves two leg beats per complete arm cycle, meaning one cycle of both arms. A six-beat kick involves six. Other patterns also occur.
A restrained rhythm may suit sustained distance swimming, while faster efforts often involve more frequent kicking. The appropriate pattern depends on pace, distance, skill, and the swimmer’s coordination. No single rhythm is universally ideal.
Why This Matters Clinically
Observe how hip movement, knee motion, and ankle position work together, especially when fatigue or symptoms develop. A large knee bend, limited foot movement, or widening kick may warrant investigation, but observation alone cannot distinguish restricted mobility from reduced capacity or a learned technique.
The clinical aim is to identify physical findings that matter to the swimmer’s kick, then connect treatment, exercise, and coaching input where appropriate.
The Downbeat: Hip Flexion and Knee Extension
During the downbeat, the thigh moves downward relative to the swimmer’s trunk, followed by the lower leg and foot. Hip flexion and knee extension overlap in a coordinated sequence, rather than moving the whole leg downward as a rigid lever.
From Thigh Movement to Foot Acceleration
As the hip begins to flex, the knee may remain briefly bent while the lower leg follows. The knee then extends as the foot continues downward. This changing relationship allows movement to travel along the limb, with the foot’s path influenced by ankle position and water resistance.
The amount and timing of knee flexion vary with technique, kicking frequency, and effort. A visible knee bend is therefore expected; its relevance depends on how it contributes to the complete action.
Muscular Contributions
The iliopsoas contributes to hip flexion. Rectus femoris crosses both the hip and knee, contributing to hip flexion and knee extension, while the vasti contribute to knee extension. Their loading changes as the thigh and lower leg accelerate and encounter water resistance.
The hamstrings and other surrounding muscles contribute to joint control and transitions between actions. Trunk musculature helps manage the pelvis as the legs alternate. Muscle activity cannot be inferred precisely from the appearance of the kick alone.
Why Ankle Position Matters
The ankle generally remains plantarflexed as the foot moves through the downbeat. Available plantarflexion and coordinated foot positioning influence how the foot meets the water.
Restricted ankle movement may change the action, but a foot that appears less pointed does not automatically require stretching or manual treatment. Compare active and passive movement, symptoms, and the swimmer’s ability to sustain the position.
Clinical Application
When the downbeat is restricted or symptomatic, examine hip flexion, knee movement, ankle plantarflexion, and relevant resisted loading. Consider the iliopsoas, rectus femoris, quadriceps, and surrounding structures according to the findings.
Distinguish a movement restriction from difficulty producing or repeating force. Treat relevant limitations, reassess the original task, and connect useful changes with progressive exercise and swimming practice.
Lower-Limb Muscles: Anatomy and MSR Treatment Priorities
The downbeat combines hip flexion with changing knee position and a generally plantarflexed ankle. The muscles producing these movements also interact with those controlling the pelvis and the returning leg. Examine relevant structures according to symptoms, available movement, and loading tolerance.
Iliopsoas
Anatomical involvement: Psoas major arises from the lumbar vertebral region, while iliacus occupies the iliac fossa. They converge toward the lesser trochanter through the iliopsoas tendon. Iliopsoas contributes to hip flexion as the thigh moves into the downbeat, with its mechanical demands influenced by hip position and pelvic movement.
MSR treatment priorities: Compare active and passive hip movement with resisted hip flexion. Anterior hip discomfort does not establish iliopsoas involvement; consider hip-joint and other regional findings. Where treatment is indicated, use trained anatomical access and controlled pressure, respecting nearby abdominal and neurovascular structures. Reassess the relevant movement or loading task and connect useful changes with progressive hip-flexor exercise.
Rectus Femoris
Anatomical involvement: Rectus femoris originates from the anterior inferior iliac spine and the region above the acetabulum. It joins the quadriceps tendon and acts through the patella and patellar ligament to the tibial tuberosity. Crossing both hip and knee, it contributes to hip flexion and knee extension.
Its length and force contribution depend on the position of both joints. During the downbeat, shortening at one joint may coincide with lengthening at the other, so its behaviour cannot be described from knee movement alone.
MSR treatment priorities: Assess anterior thigh findings, resisted hip flexion and knee extension, and knee flexion with the hip in different positions. Treat relevant muscle restrictions or symptoms without assuming that a visible knee bend reflects rectus femoris tightness. Reassess the identified limitation and develop capacity across appropriate hip and knee positions.
Vastus Lateralis, Medialis, and Intermedius
Anatomical involvement: The vasti arise from the femur and join the quadriceps tendon. Unlike rectus femoris, they cross only the knee. They contribute to knee extension as the lower leg accelerates through the later downbeat and help control knee motion against changing resistance.
MSR treatment priorities: Examine knee range, resisted extension, anterior thigh symptoms, and tolerance to repeated loading. Consider relevant quadriceps findings alongside the patellofemoral joint and quadriceps or patellar tendon when indicated. Adapt treatment to tissue irritability, then reassess movement and loading. Avoid attributing the swimmer’s knee control to one portion of the quadriceps without supporting findings.
Muscles Supporting the Action
The hamstrings, gluteals, calf muscles, and ankle dorsiflexors also contribute to the alternating kick through movement, control, and transitions. Their relevance extends beyond the downbeat and will receive greater attention in Part 5.
For this instalment, examine them when findings suggest that they influence knee movement, pelvic control, ankle position, or symptom response. Repeated involvement directs clinical attention; demonstrated limitations determine treatment.
Freestyle Swimming: Connecting Hip, Knee, and Ankle Function
The flutter kick depends on how movement passes along the limb. Available motion at one joint does not establish that the swimmer can coordinate the complete action. Interpret hip, knee, and ankle findings together, considering pelvic control and the response to water resistance.
Hip Movement and Pelvic Control
As the hips alternate between flexion and extension, the trunk helps manage pelvic position. If hip movement is restricted or uncomfortable, the swimmer may accommodate it through changes in pelvic or spinal movement, knee bend, or kick amplitude.
These adjustments are not automatically harmful. Compare the observed pattern with symptoms and examination findings before deciding whether it warrants treatment or coaching input.
Knee Motion Within the Sequence
The knee bends and straightens as the thigh changes direction and the lower leg follows. The amount of bend reflects coordination, effort, and interaction with the water, alongside available joint movement.
A pronounced knee bend may warrant examination of hip movement, quadriceps capacity, and kick timing. It should not automatically be interpreted as quadriceps weakness or a knee-joint restriction.
Ankle and Foot Position
The ankle generally remains plantarflexed, allowing the foot to form a continuation of the lower leg. Its position changes subtly as muscular activity and water pressure interact.
Compare active and passive plantarflexion, symptoms, and the ability to maintain a comfortable foot position during repeated movement. Consider talocrural mobility and relevant lower-leg muscle findings when indicated. Avoid forcing greater range when the limiting factor is pain, control, or an individual anatomical boundary.
Fins also change the surface acting against the water and the demands placed on the lower limb. Ask about their use when symptoms or fatigue differ between sessions.
Reassess the Relationship
Select a meaningful finding, such as hip movement, knee-flexion range, or ankle plantarflexion, and reassess it after care. Then review whether the change affects the swimmer’s comfort or ability to sustain kicking.
Clinical improvement and improved kick coordination are related questions that require separate observation. Manual care and exercise address physical findings; swimming practice and coaching help establish how those changes are used in the water.
Distinguishing Mobility From Strength and Endurance
A swimmer may have sufficient hip, knee, and ankle range yet struggle to maintain the kick as training continues. Another may produce strong isolated contractions but encounter a restriction during each leg cycle. Compare available movement with the ability to produce and repeat force, then relate those findings to the swimmer’s symptoms and training demands.
Mobility: Is the Required Movement Available?
Compare active and passive hip flexion and extension, knee movement, and ankle plantarflexion. Note symptoms and whether changing the position of an adjacent joint alters the response.
For example, assess knee flexion with the hip in different positions when considering rectus femoris extensibility. At the ankle, distinguish restricted passive plantarflexion from difficulty actively positioning the foot. Neither finding alone establishes its effect on swimming.
Strength: Can the Swimmer Produce Force?
Use appropriate resisted testing of hip flexion, knee extension, and relevant supporting muscle groups. Interpret reduced force alongside pain, effort, joint position, and previous injury.
A painful contraction differs from a comfortable contraction with reduced force. Compare findings across the examination rather than identifying a single muscle as the cause of an altered kick.
Endurance: Can the Action Be Repeated?
Repeated hip-flexion or knee-extension tasks can help assess loading tolerance and declining performance. Select a manageable resistance and keep position, repetitions, and stopping criteria consistent when reassessing.
Review what happens in the pool. Does the kick become difficult to sustain? Do symptoms develop earlier during faster sets or when using fins? A change with fatigue warrants investigation but does not prove a local strength deficit.
Match Care to the Finding
Relevant mobility limitations may warrant targeted muscle or joint care. Strength and endurance findings require progressive loading, while transferring those gains into the kick involves swimming practice and, where useful, coaching input.
Progress should include both meaningful examination changes and improved tolerance to the swimmer’s chosen training. More range or greater isolated strength matters when it helps the individual meet those demands.
MSR Treatment Demonstration Video
Treatment Demonstration
In this video, Dr. Abelson demonstrates MSR procedures for lower-limb structures involved in freestyle swimming. Connect the demonstrated techniques with the demands of hip flexion, knee extension, and the swimmer’s examination findings.
Select procedures for relevant muscle and joint limitations, adapting pressure, positioning, and movement to symptoms, tissue irritability, and individual tolerance. Reassess a meaningful movement or loading task afterward, then reinforce useful changes with progressive exercise and swimming practice.
These procedures are intended for appropriately trained practitioners working within their scope of practice.
Conclusion
The flutter kick combines hip movement, changing knee position, and ankle control within a continuous alternating action. Understanding that sequence helps practitioners interpret lower-limb findings in relation to the swimmer’s technique, symptoms, and training demands.
MSR care should address relevant limitations, while progressive exercise develops the strength and endurance needed to use available movement. Reassessment establishes whether treatment changes a meaningful clinical finding; feedback from swimming helps determine whether that change supports participation.
The aim is a kick the individual can comfortably sustain for their chosen pace and distance. Part 5 examines hip extension, ankle function, and common swimming complaints.
References
Fone, L., & van den Tillaar, R. (2022). Effect of different types of strength training on swimming performance in competitive swimmers: A systematic review. Sports Medicine - Open, 8, Article 19.
Matsuda, Y., Hirano, M., Yamada, Y., Ikuta, Y., Nomura, T., Tanaka, H., & Oda, S. (2016). Lower muscle co-contraction in flutter kicking for competitive swimmers. Human Movement Science, 45, 40–52.
McCullough, A. S., Kraemer, W. J., Volek, J. S., Solomon-Hill, G. F., Jr., Hatfield, D. L., Vingren, J. L., Ho, J. Y., Fragala, M. S., Thomas, G. A., Häkkinen, K., & Maresh, C. M. (2009). Factors affecting flutter kicking speed in women who are competitive and recreational swimmers. Journal of Strength and Conditioning Research, 23(7), 2130–2136.
Neumann, D. A. (2017). Kinesiology of the musculoskeletal system: Foundations for rehabilitation (3rd ed.). Elsevier.
Sanders, R. H. (2007). Kinematics, coordination, variability, and biological noise in the prone flutter kick at different levels of a “learn-to-swim” programme. Journal of Sports Sciences, 25(2), 213–227.
DR. BRIAN ABELSON, DC. - The Author
Dr. Brian Abelson is a chiropractor, author, and educator with more than 30 years of clinical experience in musculoskeletal care, rehabilitation, and sports performance. His educational work focuses on musculoskeletal conditions, human movement, sports biomechanics, and evidence-informed approaches to treatment and rehabilitation.
He is the developer of Motion Specific Release (MSR) and Clinical Director of Kinetic Health in Calgary, Alberta, Canada.
Continue Learning with MSR Courses and MSR Pro
For Healthcare Practitioners
Motion Specific Release integrates assessment, clinical reasoning, manual therapy, exercise, and patient education within one adaptable approach to musculoskeletal care.
MSR Pro and MSR courses support different parts of that learning process:
Structured Clinical Education: MSR courses connect applied anatomy and biomechanics with orthopedic and neurological assessment, myofascial procedures, fascial expansions, joint mobilization, manipulation, and rehabilitation.
Hands-On Skill Development: Live training provides opportunities to refine palpation, patient positioning, force application, and clinical decision-making through practice and direct feedback.
MSR Pro Clinical Library: Members receive access to more than 200 MSR procedures, downloadable and fillable clinical forms, examination resources, rehabilitation progressions, and exercise-prescription materials.
Extensive Video Resources: More than 800 videos support examination, treatment procedures, exercise rehabilitation, and clinical application.
Patient Education: A library of 50 condition articles helps practitioners explain common musculoskeletal problems and provide patients with practical information.
Continued Development: Resources are updated as MSR courses and clinical education continue to evolve.
Videos and articles can introduce concepts, but hands-on proficiency develops through deliberate practice, feedback, and experience. MSR is designed to help practitioners connect technique with clinical reasoning and adapt care to the individual rather than apply the same protocol to everyone.
Explore MSR Pro | View Online and Live Courses
Disclaimer
The articles and embedded videos on the MSR website are provided for educational and informational purposes only. They are not a substitute for individualized assessment, diagnosis, or treatment by an appropriately qualified healthcare professional.
Some videos demonstrate clinical examination and manual therapy procedures intended for licensed or regulated healthcare professionals with appropriate training. These procedures should be performed only within the practitioner’s legal scope of practice and should not be attempted as self-treatment.
Viewing or using this content does not establish a practitioner-patient relationship. If you have questions about a medical condition or symptoms that are new, severe, or worsening, consult an appropriately qualified healthcare provider.
MSR is not responsible for decisions made or actions taken solely on the basis of this educational content. For complete information about website use, third-party links, privacy, and legal terms, please review the MSR Terms of Use, Privacy Policy, and full website disclaimer.
Comments