Vietnam Swimming: Reading the Lane from the Hidden Kicks

In the women's 200-metre individual medley, the gap between gold and fourth place at a SEA Games is often only half a second. That half-second is not born in the final 50 metres. It is born long before, in the underwater kick after the first turn, in the angle of the foot as it leaves the wall, in a pacing decision made three months earlier in a training session with no spectators.

People watch the touch at the wall; I watch the ten strokes before it. In swimming, those ten strokes sit below the surface, where the stands cannot see and television cameras rarely replay.

After many years watching lanes, I have learned one thing: the final result is the easiest thing to read and the least informative. The scoreboard tells us who won. It does not tell us why.

Context: a swimming nation looking for its footing

Vietnamese swimming stands at a crossroads. After several SEA Games cycles in the regional lead group, a larger question has emerged: how to close the distance to the continent and the world, rather than merely holding a position within the region.

On the Asian swimming map, the hierarchy is fairly clear. Japan and China split most medals in the medley and middle-distance freestyle events. South Korea has risen on a generation of well-schooled athletes, many of whom matured abroad. Southeast Asia has isolated bright spots, including Singapore, Thailand and Vietnam, but no nation has yet produced a stable stream of athletes at continental level.

For Vietnam, the memory of Nguyen Thi Anh Vien remains a milestone. The girl from Can Tho won medals on the Asian stage, opening a belief that Vietnamese swimmers could compete at continental level. She was followed by Nguyen Huy Hoang, then by younger names such as Tran Hung Nguyen, evidence that the stream has not entirely broken.

But a few individuals do not make a swimming nation. And this is where the data story begins.

Reading the lane: the result is the tip of the iceberg

If we look only at the final time, we miss almost the entire story. A swimmer in the 200-metre individual medley can touch the wall with the same number in two different races, while the distribution of effort inside tells two opposite stories.

Take pacing. A good lane is usually divided into four 50-metre segments. The second segment, right after the first turn, is where a swimmer's nature shows most clearly. Those who hold speed here have usually built a controlled fitness base. Those who fade in the second segment but surge in the fourth are often swimming on emotion more than on a plan.

There are two classic pacing strategies: positive split and negative split. A positive split means swimming fast in the first half then slowing; a negative split means swimming slower in the first half then accelerating to the finish. In sprint events, positive splits are common. In middle and long distance, a negative split is often the sign of a swimmer with a solid physical and mental base.

What stands out is that at regional meets, very few national teams publish split data systematically. We know the result, but not the process that produced it. This is the biggest gap in Vietnamese swimming: the absence of a culture of recording and cross-checking data.

The data whirlwind of 2026 did not just change how I read a match, it changed how I see people. That year, when I began working with analytical models for a football league, I realised something that applies intact to swimming: numbers do not reveal character, but the way numbers are produced does.

The underwater part: a race inside the silence

In swimming, the part below the surface decides more than we think. After every start and every turn, a swimmer may use underwater dolphin kicking for a limited distance, 15 metres in freestyle events, with separate rules by stroke in other events. That stretch is a race of its own, run in silence.

A swimmer who loses half a second in the underwater phase after a turn will struggle to recover it while swimming on the surface. Good coaches see this first; spectators only see it once the scoreboard shows the result.

Over many years watching lanes, I have always asked myself: if we measure only the surface, how much of the race have we left out? The answer, in many short-course-distance events, can reach a third of total time. Silence in the stands is not lost data, it is a new kind of data.

Technique: a system of small decisions

Swimming technique is a chain of small decisions repeated thousands of times. Stroke rate and distance per stroke are two quantities that always trade off against each other. Raising stroke rate adds instant speed but usually reduces distance per stroke. Extending distance per stroke saves energy but can slow the rhythm.

Elite swimmers do not choose one extreme. They find a balance point, and that balance point shifts across the lane. In the first 50 metres, they may raise stroke rate; in the middle, they extend the stroke; at the end, they return to a higher rate using their last reserve.

In breaststroke, the story is more complex. Each cycle allows only one dolphin-style kick, and this rule turns technique into a problem of timing. Kick too early, and the swimmer loses momentum; kick too late, and the swimmer loses rhythm. In butterfly, two kicks per arm cycle create an almost dance-like rhythm, where missing a quarter beat loses the whole cycle.

This is why analysing swimming cannot stop at time. The same figure of 2 minutes 10 seconds can be the result of a smart lane or a wasteful one. Only split data and technical video can separate the two cases.

In Australia, data is an industry

In Australia, where I live and work, swimming is an industry with decades of data depth. Training centres record every session, every lactate reading, every technical video clip. When a swimmer competes, the team behind them already holds hundreds of data points for comparison.

Vietnam does not yet have such a system. The cause lies not in intellect but in the habit of turning observation into traceable data. A coach may have an excellent memory, but memory cannot match a standardised database.

Analysts call the information sitting between public numbers the hidden space. Between the start time and the finish time lies a chain of events that is not recorded. Whoever can read that chain understands the race.

When the crowd asks who won, I ask how. In swimming, that question leads to data zones few touch: breathing rhythm, entry angle, depth of the underwater kick, number of dolphin kicks after a turn. These do not appear on the scoreboard, yet they determine the scoreboard.

Records and the context of an era

World records in swimming must be read alongside the context of their era. The high-tech suit era, which ended in 2026, left behind a layer of records hard to reach, and many records from that period still stand across several Olympic cycles. So comparing times across eras while ignoring equipment is a common mistake.

For small swimming nations, this has practical meaning. A swimmer may improve clearly in technique and fitness while times still fail to break old marks, simply because those marks were set in a different era. Correct assessment requires seasonal and cycle rankings, not only comparison with absolute records.

The Olympic cycle and the problem of choice

Swimming runs on a four-year cycle. Each cycle has its own rhythm: the first year builds the base, the second accumulates, the third breaks through, the fourth peaks. Misreading this rhythm is a common reason swimmers peak too early or too late.

For small swimming nations, the pressure to perform at the SEA Games often distorts the cycle. Swimmers must stretch themselves at the regional meet, and by the time the Olympic cycle needs a breakthrough, the body has run dry. This is a conflict between short-term and long-term goals that very few small swimming nations resolve.

One standard deserves mention: the A-cut and B-cut of the Olympics and world championships. An A-cut lets a swimmer qualify automatically; a B-cut depends on quota. For Vietnamese swimming, having more swimmers meet the A-cut across multiple events would be a sign of a foundation, not merely an individual achievement.

A contrarian view: star or foundation?

Here a contrarian view is worth debating. Many believe Vietnamese swimming should concentrate resources on a few outstanding individuals, so they shine on the continental and world stage. That thinking is reasonable for short-term effectiveness.

But the history of world swimming shows the opposite. Strong swimming nations do not produce lone stars; they produce a layer of athletes thick enough to compete internally. It is domestic competition that creates the development threshold. A swimmer with no rival of the same generation will struggle to surpass themselves.

If we invest only to get one person to Olympic standard, we have an individual. If we build a group of ten competing for places, we have a nation. The 2026 World Cup was the first time I heard my own voice amid the choir, and that lesson still holds: value lies in seeing what the majority overlooks, even when it runs against the common expectation.

A rarely mentioned risk: the puberty barrier and the career curve

A risk factor often overlooked in swimming analysis is the puberty barrier. In many female swimmers, peak performance appears before or around puberty, then plateaus as the body changes. Developed swimming nations have built dedicated pathways for this phase: adjusting volume, protecting the mind, and patiently waiting for the body to stabilise again.

For male swimmers, the curve differs. Peak performance usually arrives later, and careers last longer. This means that at the same age, a male and a female swimmer need two entirely different training strategies. Ignoring that difference is to create risk.

Alongside this is the risk of specific injuries. The shoulders of freestyle and butterfly swimmers, the knees of breaststroke swimmers, are zones under load repeated millions of times each season. Injury prevention, therefore, is part of training, not a side activity.

The industry current behind the lane

Behind every lane is a value chain. Upstream is the youth development system and the coaching market. In the middle are the athletes and the events. Downstream are broadcasting, sponsorship, equipment and derivative markets.

For Vietnam, the downstream part remains thin. A strong swimming nation needs all three layers to develop together. When only the middle layer, athletes and events, grows while the other two stand still, the current will not hold.

It took me three years to understand: the whirlwind is not to be feared, but ridden. Data is the same. It does not threaten those in sport; it hands them a tool to see beyond the scoreboard.

What remains

Swimming, in the end, is a common language. A lane in Can Tho and a lane in Melbourne obey the same law of water, the same limits of the human body. The difference lies in how we record and learn from the water.

The question left behind is not how many more medals Vietnam will win, but whether we will begin to record the journey that produces those medals.