The Relationship Between Swimmers' Flexibility Training and Swimming Speed

Introduction

Stretching after training is a standard requirement for swimmers imposed by almost all coaches, and the belief that “good flexibility makes you swim faster” is deeply ingrained. However, sports science research offers a more nuanced answer: flexibility does directly contribute to swimming speed in certain joints, but excessive flexibility—particularly in the shoulder joint—can actually increase injury risk and even reduce propulsive efficiency.

This article analyzes the impact of flexibility on swimming by joint and provides evidence-based flexibility training strategies.

The Impact of Joint Flexibility on Swimming Speed

Ankle Plantarflexion (Impact on Swimming Speed: High)

Ankle plantarflexion range of motion is one of the determining factors in kicking efficiency. Research shows that for every 10-degree increase in ankle plantarflexion angle, freestyle kick efficiency can improve by approximately 8–12%. Elite freestyle swimmers typically have ankle plantarflexion angles exceeding 60 degrees, while the average person has only 40–50 degrees.

Conclusion: Actively train ankle plantarflexion flexibility to directly improve kicking speed.

Shoulder Joint Range of Motion (Impact on Swimming Speed: Moderate; Excessive Range Is Counterproductive)

The shoulder joint needs sufficient range of motion to achieve the high arm recovery before entry and the high-elbow catch position. Insufficient shoulder flexion (limited ability to raise the arm forward) directly restricts the stroke trajectory.

However, shoulder joint hypermobility is actually the problem—the stability of the glenohumeral joint decreases, reducing the efficiency of propulsive force transfer with each stroke and increasing the risk of shoulder impingement.

Conclusion: Shoulder flexibility should target “functional sufficiency,” not extremes. Stability and mobility must progress together.

Thoracic Spine Rotation (Impact on Swimming Speed: Medium-High)

Torso rotation in freestyle requires mobility of the thoracic spine (not the lumbar spine). When thoracic rotation is restricted, the body compensates with the lumbar spine, increasing lumbar stress and reducing rotational efficiency.

Conclusion: Thoracic extension and rotation mobility training clearly benefits both freestyle and butterfly.

Hip Joint and Lumbar Spine (Impact on Swimming Speed: Medium)

Both dolphin kick and freestyle kick require sufficient hip flexion and extension range of motion. Tight hip flexors (as mentioned earlier) restrict the kicking amplitude and reduce propulsive force.

Static Stretching vs. Dynamic Mobility Training

Key Finding: Prolonged static stretching before training (>30 seconds, particularly of the lower limbs) temporarily reduces muscle explosive power and tendon elasticity. Therefore, warm-ups before training should focus on dynamic mobility, while static stretching is best performed after training.

Flexibility Training Program for Swimmers

Every Morning (10 minutes after waking up)

• Thoracic Rotation Stretch: 10 reps/side
• Kneeling Hip Flexor Stretch: 30 seconds/side
• Ankle Plantarflexion Stretch (kneeling sit): 60 seconds
• Shoulder Abduction Stretch: 20 seconds/side

After Training (20 minutes)

Debunking Flexibility Training Myths

• Myth 1: “The more flexible, the faster”: The ankle joint does indeed benefit from greater flexibility, but extreme looseness in the shoulder joint is actually harmful. The goal of flexibility is “functionality,” not pursuing extreme range of motion beyond what competition demands.
• Myth 2: “You must stretch extensively before training”: Static stretching should be done after training. Only dynamic warm-ups should be performed before training.
• Myth 3: “Stretching prevents all injuries”: Flexibility training is just one component of injury prevention; strength training and movement pattern correction are equally important.

Practical Recommendations

• Once a month, use a measuring tool (goniometer or app) to record ankle plantarflexion angle and track training progress.
• Athletes with excessive shoulder flexibility (naturally lax ligaments) should focus on strengthening the rotator cuff muscles rather than continuing to stretch.
• PNF stretching (contract-relax method) is the most efficient way to improve range of motion; it is recommended to learn it under the guidance of a coach or therapist.

Conclusion

The core philosophy of flexibility training is “goal-oriented”—train each joint to the exact degree of range of motion it needs, no more and no less. Actively stretch the ankles, maintain shoulder mobility within stability, and keep the thoracic spine rotationally flexible—this “smart flexibility strategy” will help you improve swimming speed and athletic longevity far better than blindly pursuing whole-body flexibility.

Related Reading

• Flexibility Training for Swimmers: Ankle, Shoulder, and Thoracic Spine Mobility
• Flexibility Program for Swimmers: Systematic Training for Ankles, Shoulders, and Thoracic Spine
• Flexibility Training for Swimming: The Impact of Ankle and Shoulder Range of Motion on Kicking and Stroking
• Swimming Kick Power: A Guide to Calf Flexibility Training