Balance and Center of Gravity in Japanese Swords: Handle Grip and Physical Impact in Iaido

What is Balance in Japanese Swords?

Japanese swords have a distinctive "center of gravity," and depending on how far it is from the handle, the feel when swinging, speed, and fatigue accumulation change significantly. Most swords have their center of gravity approximately 10-20 centimeters from the tsuba in the direction of the blade, and this position affects how easily the edge line can be maintained and the acceleration sensation when striking downward.

Practitioners of iaido and battojutsu often focus primarily on weight when selecting a sword, but in reality, the position of the center of gravity has a greater impact on ease of handling. Even with two swords of the same 900 grams, one with its center of gravity near the tsuba and another near the kissaki feel completely different to operate. This is the result of comprehensive design encompassing the construction of the blade, the curve, the difference between the width at the base and the width at the tip, and even the position of the mekugi holes and weight distribution of the nakago—it is a manifestation of refined craftsmanship in Japanese sword making.

Sword Weight and Center of Gravity: Understanding Feel from the Numbers

Weight guidelines vary depending on the type of sword.

Edo period combat swords were generally heavier than modern iaido training swords.

The feel also changes significantly depending on the position of the center of gravity.

Additionally, even with the same blade length, the position of the center of gravity changes depending on the depth of the curve. Deeply curved swords tend to have thinner forward portions, while swords with shallower curves or nearly straight construction tend to have their center of gravity closer to the handle. When selecting a sword, keeping in mind the relationship with such blade shape leads to more accurate judgment.

Basic Grip: The Meaning of Tightening the Pinky and Ring Fingers

The grip used for Japanese swords is unique even among martial arts. The basis lies in gradual variations in strength application.

• Pinky and ring fingers: Grip firmly
• Middle finger: Moderate strength
• Index finger and thumb: Light contact only

This is not merely a stylistic difference but is based on rational reasons rooted in body structure.

The reason for gripping primarily with the pinky and ring fingers is that muscle groups near the forearm's rotation muscles (pronation and supination) work effectively, allowing force to be transmitted without disrupting the edge line. When force is applied to the index finger and thumb, the wrist becomes locked and the edge line is easily disrupted. Particularly at the moment of drawing, maintaining smooth saya-biki requires not "gripping" the handle but "just touching" it—this distinction between releasing tension and applying firmness is one of the core principles of iaido technique.

The positional relationship between both hands is also essential.

• Right hand (front hand): Placed on the upper part of the handle, about one grip's width from the tsuba
• Left hand (back hand): Placed near the kashira (pommel)

By maintaining proper spacing between the hands, the movements of drawing, swinging, and returning the sword proceed smoothly. If the spacing is too narrow, operability suffers; if too wide, force disperses and the edge line becomes uncertain. Adjustment suited to the handle length and one's physique and arm length is essential.

Strain on Arms, Shoulders, and Hips: Knowledge to Prevent Injury

Improper grip, posture, and sword selection can lead to chronic strain on the shoulders, elbows, and wrists over time. Iaido and battojutsu may appear to be relaxed movements, but repetitive drawing motions continue to concentrate load on specific muscles and joints, making proper care and understanding of the body essential.

• Wrist (risk of tendinitis and carpal tunnel syndrome): The main causes are forceful gripping and repetitive motion without proper edge line alignment. Keep your wrist relaxed and develop the habit of confirming your edge line through mirrors or instructor feedback.
• Elbow (symptoms similar to tennis elbow or golfer's elbow): Prolonged use of a heavy sword can cause inflammation on the inside or outside of the elbow. Increasing training volume gradually and starting with a lighter sword helps prevent this. Particularly, beginners who start using heavy real swords too early are prone to elbow and wrist problems, so gradual progression is recommended.
• Shoulder (shoulder joint fatigue and rotator cuff inflammation): Continuous unnatural loading on the shoulder during the sequence of drawing, swinging, and returning the sword tends to cause inflammation. It is important not to neglect warm-up and cool-down and to continuously improve form.
• Hips and core: If the hips and core are unstable, excessive load concentrates on the upper body; in iaido's seated techniques, lower body stability becomes the key to enhancing whole-body coordination, and it is helpful to regard core strengthening as part of long-term care.

How to Check Balance When Selecting a Sword

Here are practical methods to confirm a sword's balance before purchase. Make the most of opportunities to try holding swords at blade dealers and dojos by keeping the following points in mind.

• Single-finger balance test: Place your index finger on the blade portion approximately 10 centimeters from the tsuba and try to keep the sword level. If the sword remains nearly horizontal at this position, the center of gravity is close to that point; if it tilts toward the handle, it is near-tsuba; if it tilts toward the point, it is near-kissaki. Use this information along with your school's training content and your own physique.
• Confirm the feel during practice swings: If possible, actually perform suburi (practice swings) and confirm the acceleration and resistance sensation in both downward and upward swings. When there is discomfort, it is important to discern whether it is something that will become natural with repeated training or something that does not suit your body structure. It is ideal to have a senior instructor or experienced practitioner present and receive objective opinion.
• Check handle thickness and length: A handle that does not fit your hand size can become a source of fatigue. Generally, a length where the pommel fits in the palm is ideal. Handle wrapping thickness and material (genuine silk or synthetic) also affect grip feel, and slip resistance when perspiring is also an important confirmation point.

Pursuing Unity with the Sword

Iaido and battojutsu are martial arts that pursue unity with the sword. When experienced practitioners speak of "the sword becoming part of one's body," it is no exaggeration—it is a state that arises only when center of gravity, grip, posture, and breathing are integrated.

To achieve this, it is first important to understand the characteristics of your own body. Your dominant hand's strength, shoulder flexibility, palm size, and habitual postural patterns—all of these affect sword selection and training methods. This is why the same sword is not necessarily optimal for everyone even when practicing the same school, depending on differences in physique and experience.

For long-term training practice, "building a body that does not tire easily" is also an important element. By not only understanding sword balance but also engaging comprehensively in core training, maintaining flexibility, and providing appropriate rest and nutrition, one can safely handle the sword even as one ages.

Understanding the sword also means understanding your own body. I hope you will deepen your awareness of balance and center of gravity through daily practice and pursue deeper technical exploration.