The Empty Decoding Sheet: Why Vietnamese Swimming Still Has No Public Data Layer

On May 12, 2026, from the stands of the My Dinh aquatic centre, I sat with a stopwatch, timing the eight lengths of a men's 400-metre individual medley final.

Four strokes. Eight lengths. One press of the button for each. I recorded sixteen numbers: cumulative splits and individual splits, plus a start reaction time I estimated by eye. When the official result sheet went up on the board, it returned a single line: name, province, final time.

No splits. No reaction time. No stroke rate. No distance per stroke. No underwater time after the backstroke turn. No turn and breakout data.

I have kept that hand-timed sheet in a notebook to this day. It is evidence of an uncomfortable paradox: we stage a regional Games with an electronic timing system that meets international standards, yet most of the data that system produces never reaches the public — and certainly never reaches the people who need it most, the young coaches in the provinces.

That is why I call this piece the empty decoding sheet.

Swimming is the most measured sport, and the most hidden one

No sport is measured as densely as swimming. In a 50-metre lane, an athlete passes dozens of measurement points: reaction time, entry angle, maximum dive depth, number of underwater dolphin kicks, breakout point, 15-metre time, every 50-metre split, stroke rate, distance per stroke, turn contact time, push-off time, closing speed. In the 1,500-metre freestyle, a swimmer covers thirty 50-metre segments — thirty pacing decisions, thirty judgments within a few thousandths of a second each.

At world championships and the Olympic Games, Omega Timing publishes almost all of this through its race analysis system. Anyone with a laptop can download the splits of a final, rebuild the speed curve, calculate distance per stroke, and compare two athletes segment by segment.

In Vietnam, that data layer barely exists in public form.

National championships run by the federation have electronic timing and electronic scoreboards, but the split data — which costs a little storage and a little staff time to export — usually stays on the organiser's server and vanishes when the meet ends. At youth level the situation is further behind: most provincial and national youth meets still use hand timing, where each press of the button can carry an error of up to three-tenths of a second.

When I worked as a swimming reporter for a major daily early in my career, I once filed a formal request for the split sheets of a national championship. The reply was a question in return: "What do you need the segment times for?"

It was not a stupid question. It reflected a deep-seated way of thinking: the result is the score, and the score is the medal. People need to know who finished first, who finished second, and which province leads the table. That an athlete lost 1.4 seconds in the third 50 of a 400 IM is not considered information worth keeping.

SEA Games 2026 taught me that poor data can still open a vast universe. I was 19 that year, asked by a lecturer to compile statistics for a U23 football match. I built a spreadsheet tracking 37 passes in the attacking third and calculated an expected-goals figure of 0.68 for a team that lost 0-3. The spreadsheet was ugly, manual, full of error. But it said something the scoreline could not.

In swimming, we do not even have that ugly spreadsheet at system scale.

What a data layer actually contains

For a swimming nation to see itself, it needs five layers of data at minimum.

The first is split times by segment. Without them, every tactical judgement is guesswork.

The second is technical metrics: stroke rate, distance per stroke, and the ratio between them. Stroke rate is measured in strokes per minute. Distance per stroke is metres travelled per stroke cycle. The two tend to oppose each other: raise the rate and distance per stroke usually falls, and vice versa. An efficient swimmer holds a high distance per stroke while maintaining a fast enough rate — and knows how to change rate by segment rather than holding a constant across the whole race.

The third is turn and underwater data: contact time, dive depth, number of dolphin kicks, breakout point. In short-course racing, the underwater phase after the start and after each turn can account for nearly half the total distance swum. A swimmer who dives shallower and surfaces half a beat earlier has lost an advantage before the race truly begins.

The fourth is physiological data: lactate after each swim, heart-rate recovery, training volume by intensity zone. This is where Vietnamese swimming is furthest from the world, and it is also the most expensive layer.

The fifth is trajectory data: results by age, by training cycle, by season. How fast does a 16-year-old swim the 400 IM, how many seconds per year does he improve, at what age does peak performance normally arrive — questions no single fitness test can answer without long-term records.

These five layers are not independent. Without the first, the other four lose their anchor.

The gap behind the medals

Nguyen Thi Anh Vien is the greatest swimmer of Vietnamese swimming this century. Born on November 9, 2026 in Can Tho, she won eight gold medals at the 2026 SEA Games in Singapore, and according to domestic press tallies her career total of SEA Games golds exceeds twenty — a record for Vietnamese sport at regional level. She competed at three consecutive Olympic Games. She medalled across event groups: individual medley, butterfly, backstroke, freestyle.

That is what the record book tells us.

And that is also all it tells us.

Without a published split sheet for a 400 IM, we cannot answer the most basic tactical question: which segment did she win, and which did she lose? For an individual medley swimmer, the breaststroke leg is usually where the podium is decided at continental level. If her breaststroke was around a second slower than her Southeast Asian rivals over 100 metres, then an entire training strategy had to revolve around compensating for or concealing that weakness — swimming the butterfly and backstroke legs faster to build a buffer before the breaststroke, then committing everything to the final freestyle leg.

We know she finished first. We do not know how she did it.

This is not an academic matter. It has direct consequences for the next generation. A provincial coach trying to develop an IM swimmer needs to know that at SEA Games level the decisive window sits in the third and seventh 50s of a 400 IM. Without the data, people coach by feel, and feel usually reproduces the model their own coach taught them twenty years earlier.

Every race is a confession; I am only the one who decodes the whispers from the sheet. In Vietnamese swimming, those whispers have never been recorded.

The pacing problem in the 1,500 metres

Nguyen Huy Hoang was born in 2026 in Quang Binh, and broke through at 18 with a silver in the 1,500-metre freestyle at the 2026 Asian Games in Jakarta, plus a bronze in the 800 metres. The gap between him and the champion that year was under four seconds — a tiny margin at the longest distance in the pool.

The 1,500 freestyle is a pure pacing problem. Thirty 50-metre segments. No two turns feel the same, because lactate accumulates steadily segment by segment. There are two broad tactical schools. The first is even pacing — holding near-constant speed throughout. The second is negative splitting, swimming the back half faster and committing the fastest section to the final 300 metres.

Both have physiological grounding. Even pacing conserves energy and delays lactate accumulation. Negative splitting demands an exceptional aerobic base but places psychological pressure on rivals in the decisive phase.

To choose between them, a coach needs one number: the spread between the fastest and slowest 50 in the swimmer's own race. For a young distance swimmer just starting out, that spread can reach four or five seconds. For a continental-level swimmer, the ideal spread is usually compressed below two seconds.

Without splits, nobody knows what that spread is. People only know the total time.

And the total time is an extremely lazy number. It collapses thirty different decisions into one line, then lets the reader believe those thirty decisions were identical.

With Huy Hoang's 2026 Asian Games splits, we would know a great deal. Did he go out too fast? Was the 500-to-1,000-metre section where he lost most time against the champion? Did his acceleration come in the final 200 or the final 400? An 18-year-old Vietnamese swimmer covering 1,500 metres with an internal spread under two seconds is an athlete whose aerobic base is approaching continental level. If his spread was four seconds, that is the signature of someone who still has a great deal of foundation to build before dreaming of the Olympics.

The difference between those two versions is the difference between two entirely different training programmes, spanning years and costing billions of dong.

We are making that decision without data.

The 400 IM and the standing of the breaststroke leg

Tran Hung Nguyen is one of the notable names in Vietnamese swimming in the individual medley, a regional gold medallist.

The 400-metre individual medley has the harshest structure in the sport: 100 butterfly, 100 backstroke, 100 breaststroke, 100 freestyle. Four strokes that differ in mechanics, in dominant muscle groups, in breathing rhythm, and even in how the stroke count is tallied.

At world level a fairly consistent rule applies: the fastest segment in a 400 IM is usually the opening butterfly, and the slowest is usually the breaststroke. The breaststroke leg is also where distance per stroke drops most sharply, because breaststroke has an underwater arm recovery and a much shorter glide phase than the other strokes.

In other words, in a 400 IM the third leg usually decides the race. Not the closing freestyle leg, as most spectators assume, but the third, breaststroke leg. The swimmer who holds the highest breaststroke speed without burning the reserve is the one who still has something left for the final freestyle.

A coach trying to improve a 400 IM time must answer one question: how many seconds does my swimmer lose in the 100 breaststroke against the theoretical baseline, and are those seconds distributed across stroke rate or distance per stroke?

If the loss comes from too slow a rate, the fix may be increasing frequency by shortening the glide — but a shorter glide reduces overall efficiency, so the trade-off must be balanced. If the loss comes from too short a distance per stroke, the problem lies in leg strength and kick mechanics, requiring months of supplementary work.

Those two diagnoses lead to two completely different training programmes. Without data, coaches often choose both at once, dilute both, and lose two years.

How much is three-tenths of a second

If you have ever stood at a pool deck with a stopwatch, you know the error on each press sits somewhere between two and three-tenths of a second. That is the error of ordinary visual reaction — the eye sees the hand touch the wall, the brain processes it, the finger presses.

At a national-level freestyle speed of about two metres per second, three-tenths of a second equals sixty centimetres. A 1.80-metre swimmer has a torso roughly sixty to seventy centimetres from shoulder to hip.

In other words, using hand timing at youth meets means letting half a human body fall into the blind zone.

Results at youth meets are therefore noisy at the two-to-three-tenths level — enough to change the ranking between two evenly matched swimmers. And when the underlying data is noisy, every analysis built on it is noisy too, not additively but multiplicatively.

I once sat with three consecutive years of hand-timed youth meet data and tried to build a regression line for performance progression. The line came out almost flat. At first I thought it meant the swimmers were not improving. Then I realised there was a simpler possibility: the line was flat because the error was larger than the signal.

A coach looking at that table would conclude the child has no potential left. That conclusion may be right, and it may also be an unjust sentence.

That is why I always tell young analysts: electronic timing is not a luxury. It is the minimum condition for the question "is this swimmer improving" to mean anything at all.

Infrastructure, and the numbers nobody wants to publish

There are three foundational numbers for any national swimming programme.

The first is the number of 50-metre pools that meet competition standards. In Vietnam that figure is still in double digits, and its distribution is heavily skewed towards the two largest cities. The consequence is that a talented swimmer from a remote area must leave home at thirteen or fourteen to reach a proper pool. Not every family can do that.

The second is the proportion of coaches with formal training in sports science. That figure is far lower than the number of athletes competing in the national meet system.

The third is average weekly pool hours for youth swimmers. In strong swimming nations, young athletes train eighteen to twenty-four hours a week, plus three or four dry-land sessions. In Vietnam, many centres still revolve around ten to fourteen hours.

These three numbers explain most of our distance from the leading swimming nations of the continent. Yet all three rarely appear in end-of-season reports.

The reason is simple: they are not medals. A report saying we won ten medals at a regional Games will be read. A report saying only thirty percent of youth swimmers meet the recommended distance-per-stroke threshold will be ignored.

But it is the second kind of data that forecasts the medals of five years from now.

Behind a gold medal is an economic contract

I once sat across from a prize-money schedule for a regional Games, and what struck me was the gap between categories.

A regional gold can change a rural family's finances. It brings statutory bonuses, sponsor bonuses, advertising contracts, a permanent post with the managing body, and a university place.

A bronze changes almost nothing.

The gap between gold and bronze at a regional Games is sometimes one point two seconds. Meanwhile the gap in economic value between those two positions can be a multiple.

The consequence is that competitive incentives at national level bend towards optimising regional medals rather than absolute performance. A swimmer may choose an event where she is certain of a medal over one where she might break a national record but finish fourth.

From a medal-management standpoint, that is a rational decision. From a development standpoint, it is a form of silent talent leakage that no medal table ever records.

The numbers speak, but nobody asks how many times they have wept.

The contrarian angle: the medal table is a dirty variable

In statistics we distinguish clean variables from dirty ones. A clean variable measures exactly what it claims to measure. A dirty variable measures one thing while being driven by several others that are never recorded.

The medal table is a severely dirty variable.

It is driven by the number of events entered, by whether a rival nation sends its strongest swimmers, by the competition schedule, by whether the Games fall within a generation's physical peak. A country can increase regional golds while its athletes' absolute times stagnate or decline.

This is a classic error: correlation read as causation.

We believe many regional golds mean the sport is rising. But swimming's true benchmark is not regional. It sits at the Olympic qualifying standard, at the A and B cuts of continental championships.

A swimmer who wins regional gold while sitting three seconds off the Olympic qualifying standard is a very good swimmer at regional scope, and has not yet reached the global competitive threshold. Both facts are true at once, and collapsing them into a single narrative is where sports media usually loses its precision.

The reverse angle is more uncomfortable still: part of the reason we have not advanced further at continental level is that we invest extremely well in regional level. The system is optimised for the goal it is achieving. To reach a different goal, you change the yardstick, not just the budget.

This is a conclusion at current confidence levels, based on publicly available data that anyone can look up. If a complete split set from the last three regional Games were published, I would be ready to revise it.

Signals for the next cycle

An empty stadium is a strange marriage of data and loneliness. A pool at five in the morning is the same, except there you cannot see the crowd that has left — you only hear the water.

There are three signals I will be watching next cycle. First, the publication of splits at national meets, even as raw files. Second, the emergence of a dedicated race-analysis role within national team coaching staffs. Third, provincial centres moving from hand timing to electronic timing, even at small scale.

None of these are medals. But all three are conditions for a medal to become a credible signal rather than an over-celebrated random event.

I do not pray with bells, but with discrete strings of numbers each night. Every night I open an empty file, place the cursor in the first cell, and wonder whether someone in some training centre is filling in the same cells.

And while I wait, there is one question I have never answered: which number ever recorded the loneliness of a swimmer covering fifteen kilometres a day?