TFL Glossary
The movement terms used across the TFL Footwork Research Project, each with a plain definition and the context in which it appears. Terms borrowed from Taiji and Aikido are given in romanised form with the meaning the project uses. How these terms are said in Vietnamese - the usage varies by context - is recorded on the Vietnamese page, Thuật Ngữ TFL.
Split Step
The small hop made as the opponent's racquet starts forward, landing just as the ball is struck. It exists to load the legs like a spring, to unweight the foot that must step, and to buy the beat of balance in which every change of direction happens. Done twice per rally: returning serve, and answering the first attacking ball. Failure modes: jumping too high, landing on straight legs, splitting too early or too late.
Unweighting
Making a foot light so it can leave the ground before the body does: weight settles toward a 60/40 pattern and the stepping foot rests on the ball, heel barely down. Taiji calls it xu-shi - one foot full, one held empty; never double-weight. A foot that still carries load can only push; only an unweighted foot can redirect. In Vietnamese the action is called differently depending on context - lifting the heels to react, unloading body weight, or shifting weight off one foot - all collected on the Vietnamese page.
Load / Unload
The stretch-shortening cycle at the heart of the split step: the leg muscles lengthen under load, then immediately shorten to release the stored energy. Coaching version: bend and rebound - the dip is inches, not feet. Taiji's fa-jin describes the same coil-then-issue of force from the foot.
Dynamic Balance
Balance in motion, not stillness: the state from which any direction can be taken next. The test is the level head - if the head stays level through a change of direction, balance survived it.
Flexibility
In this project, flexibility is the body's ability to coil and uncoil - hips, knees and ankles that shorten and lengthen without locking. It is measured by how quietly the weight shifts, not by static range of motion.
Recovery
The return to neutral after every shot: the first step back to the ready position, re-centering before the next read. A rally is a chain of recoveries, and the split step is what makes each one possible.
Martial-Arts Terms
- Fa-jin (Taiji) - the explosive issue of force; here, the coil-then-release from the foot.
- Xu / shi (Taiji) - empty and full: the weight distribution of the feet, one loaded, one light. The source of "never double-weight".
- Root in the foot (Taiji) - force rising from the ground through the foot, not generated by the muscle.
- Hanmi / kamae (Aikido) - the ready stance, a triangle with the rear foot as base; 60/40 weight, never square to the opponent.
- Irimi / tenkan (Aikido) - enter straight off the line, or turn off the line; the two steps from which every technique is assembled.
- Ma-ai (Aikido) - distance and timing as one discipline: the step is right when the body is loaded exactly when the opponent commits.
- Tai-sabaki (Aikido) - body displacement: turning, weight-shift, the S- and V-shaped paths of the hips.
- San-ti (Xingyi) - the three-body stance, 3/7 weight distribution.
Translation Notes
The project ships in English and Vietnamese, one language per page and per diagram. Several movement terms have no single Vietnamese equivalent, and a few common mistranslations are worth naming so they do not spread: rally is pha bóng (not "phen bóng"); a tennis player is người chơi quần vợt / vận động viên quần vợt (not "cau thu"); the big-hop error is cú nhảy mạnh (not "cú nhảy to"); and unweighting is never "giải phép". The full list, with contexts, lives on Thuật Ngữ TFL.
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