The Nordic Defence Sector has interviewed the narcotics physician and researcher Johan Ullman, who leads the NATO project MASHIEN. The study investigates how shock exposure aboard fast boats affects the crew's combat readiness and health. The results will lay the foundation for a common standard to prevent serious skeletal and brain injuries among operators.

Johan Ullman is a reserve officer and physician. As a flotilla doctor in the 1st Fast Attack Flotilla in 1984, he noted the effects of shock exposure aboard high-speed boats.

– I was tasked with medically discharging conscripts from the torpedo boat divisions and was horrified to find that 85 percent had experienced back pain from their service aboard. They said it didn't matter whether they were sitting or standing; it just hurt immensely when the boats hit the water, Ullman tells NDS.

This insight prompted him to begin researching how the mechanics and exposure actually look. Historically, measurements at sea have focused on vibrations, which he argues is directly incorrect when assessing the risk of serious injuries.

– There was no real knowledge in this area. Most who have previously researched this have not understood the physics behind how much energy a shock contains and how extremely quickly that energy is transferred to the human body, he says.

To understand the real injury risk, the concept of "jerk" is central. It describes how quickly acceleration changes. A strong acceleration that builds up over time affects the entire body uniformly, while a sudden and hard shock has completely different consequences.

– If the acceleration goes from 0 to 10 g in ten milliseconds, it produces a much higher mechanical effect than if it takes 50 or 100 milliseconds. A blow that goes straight up to maximum immediately, and then dissipates, affects the body's various organs in different ways. This is because the stop time is so much shorter. It is this type of exposure that causes personnel to injure their backs and necks, Ullman explains.

To map the problems and find threshold values, he now leads a research group within the NATO Science & Technology Organisation (STO). NDS has previously published a post by John-Mikal Størdal, head of STO CSO. The study Ullman leads is called MASHIEN and involves a total of 34 researchers from 15 different countries. The project is primarily funded by the Swedish Armed Forces through research and technical development funds.

– Every person, wave, and hull impact is different. We need large amounts of data and must measure on the boats in real life. Two personnel per boat carry accelerometers attached near the iliac crest, measuring in three axes up to 5,700 measurement points per second per boat to analyse.

Ullman argues that a well-known problem within the marine environment is the underreporting of symptoms. Personnel often avoid seeking care at their unit for fear of losing their flight or sea status and ending up behind a desk. To obtain objective data, the technical measurements are now combined with daily, anonymous information gathering from the operators.

– Once a day, participants receive a ping on their mobile phones. They are to indicate if and where they have pain, and through a slider, rate on a scale how strong the pain is, if they have been on a boat and, if so, which boat. By matching the reported pain with the measured exposure, we can correlate which specific shock levels lead to problems, Ullman says.

Previously, the focus has almost exclusively been on musculoskeletal problems, but recently there has been a growing awareness that shocks also cause serious neurological and cognitive injuries. An internal survey directed at retired American operators showed that 33 percent had experienced loss of consciousness due to whole-body shocks aboard.

– It's not just about herniated discs and vertebral compression, but now also about brain injuries. When the boat hits the water and the body is pressed downwards, the head is thrown forward with enormous force. The brain shakes inside the skull, and the rotation causes injuries similar to those seen in former professional boxers or American football players, known as CTE (chronic traumatic encephalopathy).

The seriousness of the cognitive injuries became major news when an American boat operator took his own life, and the New York Times published an article about the case in 2024. The autopsy revealed that his brain was deeply permeated by cumulative injuries linked to his service.

– It started with him making reckless decisions and being medically retired. It was mistakenly thought to be a psychiatric problem. When the autopsy later confirmed extreme CTE, it gained momentum in the USA. This led to hearings in the Senate and resulted in several American researchers joining our study, Ullman recounts. Now another dozen have joined.

Within the study, 15 countries have agreed on a new way to measure and quantify shock exposure. The results will be used to provide drivers with relevant real-time information, specifically for each boat type, about when the exposure approaches or reaches presumed harmful levels.

Concerns have been raised that stricter safety regulations could force down speeds and reduce operational capability, but this view is completely dismissed.

– This will not limit capability; on the contrary. There will be a display on each boat indicating shock exposure in green, yellow, or red. This way, the driver receives immediate objective information and can adjust speed to the task. If one needs to go faster, for example, under fire, one can still do so, but in the long run, this reduces unnecessary and harmful exposure, and the units maintain combat readiness and operational capability, Ullman concludes.