Shoulder Injuries in Vietnamese Swimming: When Training Volume Doesn't Match Competition Load

On the third morning of the national swimming championship, a nineteen-year-old male swimmer stepped onto the starting block for the 200m butterfly. He entered the water in lane four, holding an even stroke rhythm through the first hundred and fifty metres. On the final turn, his right arm stalled in mid-air; the recovery phase would not close. No one in the stands noticed. The coach shouted. He touched the wall in fifth place, climbed out, and on the next warm-up could not lift his arm above his head. The organisers recorded a single line in the report: athlete withdrew from the event for health reasons. At Lạch Tray, I learned to read injuries from the very first numbers. That one line says nothing about how many metres he swam in the six weeks before, how many overhead press repetitions he did in the gym, or how many times he stepped onto the blocks in a state of incomplete recovery. It records only the outcome. The cause sits somewhere else, and that is where I want to look. A sport measured in metres, managed by a calendar Swimming in Vietnam has a structural paradox. Results here are measured to hundredths of a second, yet training volume is almost never recorded systematically. At major centres such as PVF or the national training centre, there are logs. At most provincial teams, volume is still remembered through the coach's experience. Pool time is the first bottleneck. A typical provincial team gets only two to three water sessions a day, each lasting ninety minutes to two hours, and must share lanes with other groups. As competitions approach, the common solution is to compress volume into a high-density block of four to six weeks. This approach has a popular name: the specialised training camp. It works for short-term performance. But the body cannot read the coach's intentions; the body only reads load. Anatomically, the shoulder is the most mobile joint in the body and the most heavily demanded in freestyle and butterfly. The supraspinatus tendon, one of the four tendons of the rotator cuff, passes through a narrow space beneath the acromion. During the recovery and entry phases, when the arm is abducted to roughly ninety degrees and internally rotated, that space narrows. Repeated several thousand times per session, the tendon tissue is compressed. The medical literature calls this subacromial impingement syndrome; the colloquial name is swimmer's shoulder. The share of swimmers who experience shoulder pain at some point in their careers is documented in sports medicine as ranging from forty to more than ninety percent, depending on definition and stroke. This is a widely cited figure, and I cross-checked it against my own logs at domestic meets. The trend matched. The core: re-reading that stalled shoulder through load data When I track a middle-distance swimmer, I do not start by reviewing technical video. I start by reconstructing the load curve. There are four variables I always record. First, weekly volume in metres swum. Second, intensity as a percentage of best competitive speed. Third, the number of overhead repetitions in dryland sessions. Fourth, the actual number of rest days between two consecutive hard sessions. For a freestyle swimmer, each twenty-five-metre length requires roughly sixteen to eighteen arm cycles. A session of eight thousand metres produces more than five thousand shoulder cycles. A heavy training week can push that figure to forty thousand. Multiplied across the four weeks of a training camp, the shoulder performs hundreds of thousands of loaded rotations. This is why the shoulder is the main battleground, not the knee. The decisive variable is not total weekly volume, but the ratio between acute and chronic load. The calculation is simple: divide the current week's volume by the average volume of the preceding three to four weeks. When this ratio exceeds roughly one point five, overuse injury risk rises sharply. Numerous studies across repetitive cyclical sports have confirmed this threshold, from football to distance running. Applied to the Vietnamese context, the problem becomes visible. Provincial swimmers carry a low chronic base because year-round pool time is scarce. When they enter the pre-competition camp block, weekly volume can jump from twenty-five thousand metres to forty thousand or higher. The acute-to-chronic ratio blows past one point five. That is why the swimmer who withdraws at the national championship is usually the one with the thinnest accumulated base, not the one who trained the most. I once built a comparison table for a group of swimmers at two different centres in the same season. One side maintained even volume year-round, increasing by no more than ten percent per week. The other compressed volume into the six weeks before the meet. As competition approached, the compressing side recorded more reported shoulder-pain cases and more sessions requiring a reduction in load. A small sample, I know. But its direction aligns with the literature, and that is worth tracking further. There is another layer of data that technical video usually overlooks: stroke length decaying toward the end of a race. In the final twenty-five metres of a 200m event, stroke count typically rises while distance per stroke shortens. A tired arm narrows the entry angle, the elbow drops, and the shoulder compensates by abducting further. This is the moment the subacromial space is compressed hardest. Faulty technique late in a race is a consequence of muscle fatigue, and muscle fatigue is a consequence of a load curve broken several weeks earlier. Studying technique at this point without looking back at the training calendar is like reading the last line of a book with the first page torn out. There is one more variable few people notice: the number of overhead movements in dryland sessions. Many teams add supplementary work with weights, push-ups, and pull-ups. When water volume is already high, adding overhead dryland load nearly doubles shoulder load while the tendon has not yet adapted. Dryland training is not bad. Dryland training placed wrongly in the cycle is the problem. The contrarian angle: technique is not the first culprit The reflexive response to a swimmer's shoulder pain is to scrutinise technique. Impingement, people explain, comes from an overly wide entry, a misaligned recovery, insufficient shoulder mobility. Those factors are real and require correction. But if they were the main cause, swimmers would hurt evenly throughout the year, rather than clustering in the weeks before competition. The timeline tells a different story. The stalled shoulder appears exactly when volume spikes. That is the signature of overload, more than the signature of a faulty movement. A second common explanation is inadequate warm-up. A proper warm-up helps, but it cannot compensate for a week in which volume doubled. No warm-up routine neutralises forty thousand shoulder cycles in seven days. And here is where I want to bend the argument. Intuition tells us that a swimmer who trains less will be safer. The data shows almost the opposite: those who train little year-round, then abruptly train hard before a meet, are the most fragile group. A thin chronic base is a thin cushion. Swimmers who train steadily all season at small, even, boring increments keep their shoulders intact longer. Shoulder injury in swimming is not born from one bad session. It is born from a curve broken precisely in the week of load increase. Numbers stay silent, but their sequence always knows how to tell a story. Look only at total volume and you see a number. Look at the weekly sequence of increasing volume and you see risk. The body is a closed system, but data is the key that opens it. The shoulder does not care what a drill is called; it only records loaded rotations and rest days for regeneration. What we call injury is often another name for a load debt that was never written down. What to carry forward Vietnamese swimming does not need a sophisticated analytical system to reduce shoulder-pain cases. It needs a notebook. Weekly volume. Overhead repetitions in dryland. Actual rest days. A few minutes of recording per session is enough to see a curve breaking before it breaks a shoulder. I do not expect this to change after one season. Changing record-keeping habits is slower than changing a training plan. But I believe in a simple rule: if an athlete cannot be measured, they cannot be protected. What remains open for coaching staffs at every level is whether they will accept slowing down for one week during a load increase, to preserve a shoulder for an entire four-year cycle.