The Six Data Fields Vietnamese Swimming Still Lacks Behind Every Results Board

22:40. I reopen the PDF of the national swimming championships results, downloaded from the organiser's page. Thirty-four lines. Four columns: name, year of birth, club, final time. Enough to rank. Not enough to analyse.

I need the 50-metre split table to know who went out fast and who held the back half. There is none. I need to confirm whether the pool is 50 metres or 25. The file does not say. I need reaction time and the first-15-metre split. Nothing. A board like that answers exactly one question: who touched first. It does not answer the question a coach actually needs — where the runner-up lost time, on the third length, on the touch, or in the last two metres of the return.

Data never lies, but it knows how to hide. In Vietnamese swimming it hides in the simplest place: only what decides a medal gets published.

A swim becomes analysable data only when six fields exist: meet name and date, pool length, event and distance, athlete name, final time, 50-metre split table. These six are the minimum. Without a date, nobody can separate a swim eased through the middle of a training block from one delivered at peak. Without pool length the comparison collapses at the root: a 25-metre pool has twice the turns, and the world federation ratifies separate records for each. Without event and distance there is no coordinate system to place a swim in — world record, all-time list, or current-season ranking.

Then comes the screen every all-time list must pass. At the 2026 World Championships in Rome, 43 world records fell in a single meet. From 2026 the world federation banned full-body polyurethane suits. Any comparison across the 2026 line without that discount is methodologically unsound. Vietnamese national records sit on both sides of it.

Domestic infrastructure makes the arithmetic harder. Few competition-standard 50-metre pools exist, and they cluster in a handful of cities. Most junior meets, club meets and fitness tests run in 25-metre water. Results are published as photographs of electronic boards, without splits. An athlete can post a visible personal best simply because the meet moved from a 50-metre to a 25-metre pool, and no line of the report says so.

The first error is pool length, and it is invisible. In the 100m freestyle in a 50-metre pool an athlete turns once. In a 25-metre pool, three times. Each turn adds a push-off and an underwater glide, a phase in which the body spends no energy holding stroke posture. The gap between the two pool types over 100 metres typically lands near one second — enough to invert a national ranking. When a meet changes pools, the performance curve of an entire cohort shifts, but the report offers one conclusion: progress. There is no progress there. Only more turns.

The split table is the only thing that shows where the back half went. Without splits, a 1500m freestyle swimmer leading at 800 metres and losing twelve seconds over the last 400 generates two entirely different readings: a pacing error, or a capacity limit exposed. The first is fixable with tactics. The second is not fixable by anything that season. For a long-distance competitor such as Nguyễn Huy Hoàng, who swam the 800m and 1500m freestyle at the Tokyo Olympics, that is exactly where the split table earns its place: it turns an opinion into a test that can be repeated. A coach without splits is choosing between the two readings by feel, and feel over distance is the easiest thing to be fooled by.

The same logic applies to classification. With splits, an athlete is sorted into front-half type, back-half type, or even-split type. Three types need three training plans. Without splits everyone is bundled into one group on one plan.

Start and first 15 metres is the emptiest data zone of all. The rules cap the underwater phase at 15 metres; breaststroke allows one dolphin kick after the start and after each turn. These are technical zones with their own rules, their own officials, and the highest time value per metre. Over 50 metres the start accounts for close to a third of total race time. Without published reaction times and 15-metre splits, every start decision is made by eye — and the eye cannot separate two-tenths of a second.

The split table is also the timesheet of the turn. International data uses 5m-in and 5m-out splits to measure the turn separately from the swim. Without that pair, an athlete who loses 0.4 seconds on the third turn is recorded as losing evenly across the whole race. The two conclusions point to opposite plans: one is turn and push-off technique, the other is conditioning.

An effort index is not an efficiency index. Session volume, weekly metres, number of surges — these get logged and packaged as proof of work. An athlete swimming 12km a day with stroke efficiency decaying over the final two months of a season produces a beautiful spreadsheet and a poor result. The metrics worth tracking are distance per stroke and stroke rate; those two say what total volume cannot: over the same distance, who converts better.

A swimmer does not fall away in one night. They fall away when the indices stop connecting. In Vietnamese swimming the disconnection usually sits in the multi-season series. When a female athlete enters the 14-to-17 age band, the puberty barrier is the largest physiological screen and the least discussed: times can stall or regress while training load keeps rising. Without a season-by-season record, that stall gets retold as a psychological story — lost motivation, lost competitive edge, the weight of expectation. All of it may be true. But no table tests it, and a fifteen-year-old has no obligation to defend herself against conclusions nobody verified. The career of Nguyễn Thị Ánh Viên has been narrated far more through emotion than through a time series, and that is a loss for the industry, not just for her.

A-cut, B-cut, and arithmetic the public cannot check. Olympic and world-championship entry runs on two tiers: an A-cut grants direct entry, a B-cut depends on quota allocation. To know how far an athlete is from a slot you need three things at once: the standard for that cycle, a ratified time, and the current-season ranking. Missing one, every comment on qualification odds is guesswork. Selection mechanisms differ enough to distort expectations: the United States model takes the top two on the day regardless of history; the comprehensive-evaluation model accumulates across meets and indices. Same athlete, two models, two different probabilities.

One false start ends it. Since the rule change, a single false start means disqualification, no second chance. That is an absolute, non-compensable risk: a meet prepared for four years can end at 0.00 seconds. No model forecasts it, which is precisely why the zone belongs in every analysis rather than being dropped for being unquantifiable.

Behind all of it sits the talent supply chain. Vietnamese swimming runs largely on national training centres and provincial units; there is no dense school-meet system generating internal competition the way the American college model does. The consequence is shallow depth: an event may hold only two internationally standard athletes, and when one is injured the entire event disappears from the map. Regional medal projections therefore rest on an individual, not a system — the highest risk profile any forecasting model can carry.

There is an inverse error, and it is more dangerous than missing numbers. A report full of nulls is easily read as an all-clear: no risks identified. In swimming, not detected and not present are different sentences, and only the second permits a conclusion. I have made this mistake.

In 2026 I labelled a young athlete's improvement curve a bubble, based on its slope. Two seasons later the times held. My error was not in the model but in the baseline data: the meet I used as a reference was swum in a 50-metre pool, the later meet in a 25-metre pool, and I had not checked the second of the six fields. Since then I publish my wrong calls at the same frequency as my right ones. Luck is the thing I do not have. I have probability and data thick enough — but only while the data still has all six fields.

Correlation is not causation either. An upward time series coinciding with a coaching change does not prove the new coach is better. It proves two curves ran in the same direction inside a very small sample. In Vietnamese swimming the sample is smaller still: the number of internationally standard athletes in a single event rarely exceeds ten. At that size one good season is not a signal. Three consecutive seasons is where it starts.

Six data fields are not a technical demand. They are an editorial decision: publish splits or do not. The federation that publishes first holds the analytical first move, and that move converts into voice in selection meetings, where arguments are still settled by belief.

The signal I am watching in the next cycle: a 50-metre split line appearing in national championship results. When it does, the first thing to check is the gap between first and second at the 300-metre mark of the 400m individual medley — the event where Trần Hưng Nguyên has been a familiar Vietnamese name. That gap will say more than any post-final interview.