Front Crawl Technique: Arm Stroke Analysis and Muscle Activation
Front Crawl Arm Stroke: Curve 2 (Sweep Down/Phase-Out Grip)
Initial Position
The arm is almost fully extended, slightly forward and outward from the shoulder line. The elbow is higher than the hand and points upward and outward. The wrist is slightly turned outward, and the hand faces down, out, and slightly back.
Final Position
The arm reaches maximum depth, nearly straight and outward from the shoulder. The elbow is flexed, pointing up and out. The wrist is slightly flexed and internally rotated. The hand faces inward, backward, and upward, preparing for the next phase.
Motion Description
The hand curves downward, slightly outward and backward, maintaining its facing direction. This semi-circular motion is primarily driven by elbow flexion, which progresses from nearly straight to a sharp bend. Elbow flexion accelerates as the hand descends, reaching maximum flexion at the point of maximum depth.
Muscles Involved
Home Fitness Focus:
- Triceps brachii: Maintains arm extension.
- Biceps brachii: Increases flexion at the end of the phase.
- Deltoid: Moves the shoulder outward.
- Long, deep flexor of fingers, palmaris longus, supinator: Flex and supinate the wrist.
School Fitness Focus:
- Carpi ulnaris: Flexes the wrist.
- Anconeus: Extends the arm at the elbow.
- Pectoral: Provides attachment and support.
Other Considerations
After arm extension, the wrist should be turned outward and slightly back, maintaining a downward angle of attack of approximately 40 degrees. The hand should push water with appropriate softness and angle. For optimal propulsion, the azimuth angle (the angle between the hand’s direction of motion and the swimmer’s longitudinal axis) should be slightly greater than 90 degrees (D. Chollet). This ensures efficient water flow over the hand, exiting with increased speed on the inside of the wrist.
The hand moves downward, outward, and backward, pushing water in the same directions. This allows for shoulder rotation and hand slippage outward. The elbow should remain above the hand throughout the movement. As the hand moves towards the elbow, the elbow progressively flexes.
Just before reaching maximum depth, the hand initiates the inward and upward sweep, accelerating and twisting the wrist to prepare for the next phase. Continuous hand movement is crucial.
This phase is less propulsive when considering the entire swimmer’s body. Its positive contribution comes mainly from the lift force generated by the hand against the water flow. Form drag is less significant, with resistance and suction drag being the primary forces.
What does the other arm do? The sweep-down phase occurs while the other arm releases its grip on the water (E.W. Maglischo, “Swim Faster”).
Front Crawl Arm Stroke: Curve 3 (Sweep Back-In-Up/Pull Phase)
Initial Position
The arm is at maximum depth, nearly straight and outward from the shoulder. The elbow is flexed, pointing up and out. The wrist is slightly flexed and internally rotated. The hand faces inward, backward, and upward.
Final Position
The arm is positioned between the neck and the body’s midline, roughly below the shoulder. The elbow is at maximum flexion, pointing outward and slightly upward. The hand is at its shallowest point, facing outward, back, and up, preparing for the next phase.
Motion Description
The hand transitions from facing outward, back, and down (from the previous phase) to facing inward and back. The wrist rotates from slight internal rotation to slight external rotation. The arm, primarily using the shoulder and biceps, directs the hand inward and back.
Starting deep, the hand accelerates upward to the highest point of the stroke in a circular motion from outside to inside and bottom to top, effectively “fetching” water.
Muscles Involved
Home Fitness Focus:
- Pectoralis major: Abducts the arm.
- Latissimus dorsi: Abducts and rotates the arm.
- Teres major: Rotates the arm.
- Biceps: Contributes during flexion.
- Triceps: Contributes during extension.
- Deltoid: Elevates and moves the shoulder.
School Fitness Focus:
- Anconeus: Flexes the arm.
- Brachialis: Flexes the arm.
- Coracobrachialis: Flexes the arm.
- Radial muscles and finger muscles: Support hand and finger movements.
Other Considerations
This phase ends when the elbow reaches maximum flexion and the hand reaches its highest point. The hand’s ending position varies among swimmers. While some texts suggest it should reach the body’s midline, many swimmers finish this phase earlier, initiating the outward and upward sweep sooner.
The point where the hand prepares for the next phase depends on the depth achieved in the previous phase. Generally, if sufficient depth was reached, the hand finishes this phase behind the body.
Drag force (due to the hand’s shape) should dominate in this phase. For this to occur, the hand should face backward at approximately 40 degrees (D. Chollet, Maglischo). Hand acceleration must exceed the water flow speed for a positive resultant force.
For optimal balance between forces, action-reaction, and lift, the swimmer should aim to move water upward and backward with equal magnitude, at roughly 45 degrees.
A more open hand path would result in a force not parallel to the swimming direction, wasting energy on correcting the downward movement caused by upward thrust. A more closed hand path, while ignoring other technical implications, would reduce movement effectiveness, relying solely on form drag and neglecting lift force. This could increase stroke rate by shortening the stroke length without necessarily increasing distance per cycle.
The ideal angle of attack depends on water velocity and hand speed. While hand speed changes throughout the stroke, these changes, though relatively small in absolute value, are significant proportionally. The angles of incidence and azimuth must be adjusted dynamically based on swimming speed and hand acceleration relative to the water flow.
Swimmers intuitively adapt their hand position based on water speed. These subtle adjustments contribute significantly to the overall efficiency of elite swimmers compared to others.