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Royal Marines pioneer tech, training and treatment to tackle heat illness

Commando Training Centre Royal Marines medical staff demonstrate the treatment of heat illness in recruits
25 November 2021
Pioneering technology, training and treatment is helping to eliminate the risk of potentially fatal heat illness as recruits strive to become Royal Marines Commandos.

State-of-the-art body monitors recording trainee commandos’ physiological data, trained instructors studying that information, and medical teams on hand to treat trainees almost immediately could all-but eliminate the most serious cases of exertional heat illness in those striving to earn the legendary green beret.

Introduced in the spring of this year, the heat illness risk assessment and management system at the Commando Training Centre Royal Marines has already saved the life of one individual and prevented a couple of very serious casualties.

It follows more than three years of work and research led by the Royal Navy’s scientific experts from the Institute of Naval Medicine (INM) in Gosport and the US Army Research Institute of Environmental Medicine, plus the Royal Marines team at Lympstone, near Exeter, to better understand exertional heat illness, predict it – and intervene where necessary.

The result is a monitor – Open Body Area Network (OBAN) which records key physiological features as a trainee tackles arduous activities such as the 9 mile speed march or the gruelling ’30 miler’ which epitomises commando training.

Beyond providing the medical officer and instructors with data such as heart rate, the OBAN also records skin temperature and with a unique algorithm devised by INM and the US Military predicts the estimated core temperature and Heat Strain Index. Future generations of the OBAN will incorporate an accelerometer that will record the trainee’s running gait and with the use of the ‘wobble index’ have another metric in which to use to predict the onset of exertional heat illness.

Individuals undertaking activity whose core temperature rises above of 40°C may not necessarily be suffering from exertional heat illness – everybody is different, and some trainees may be attuned to such circumstances; this is where the OBAN’s smart algorithm provides invaluable information to allow the medical team to intervene only when necessary.  

Other recruits can quickly shift from mild symptoms – dizziness, muscle cramps and exhaustion, to heat stroke causing collapse and loss of consciousness requiring immediate intervention within a few minutes. Early recognition of Exertional Heat Illness is key to allow effective cooling to commence as soon as possible. Untreated, heat stroke can lead to multiple organ failure, permanent disability or in the worst cases loss of life.

We do not want to lose anyone and therefore process and education is paramount.

Major Erik Nielsen

The team at Lympstone have two ambulances and a rapid response 4x4 equipped with water, ice and monitoring equipment on standby with medics across Dartmoor during major exercises.  

Heat stroke sufferers are rapidly submerged in pods which are filled with ice-cold water, to cool them as quickly as possible while their condition and temperature is constantly monitored, and they’re then transported to hospital or the medical centre at the marines’ base for further treatment and observation.

The goal – beyond initially saving lives – is to return the trainees to training when they’ve fully recovered so they can continue their dream of becoming Royal Marines Commandos.

“Royal Marines’ training is arduous. It pushes people to their physiological limits, but no-one should die in training from heat illness. We do not want to lose anyone and therefore process and education is paramount,” stresses Major Erik Nielsen MBE RM.

“We know a recruit’s physical condition, their training progression, their nutrition and hydration status. Thanks to the data and that knowledge, we can better prevent, intervene and manage the risk of exertional heat illness.

The team at Lympstone are focused on exertional heat illness – caused by the body overheating through strenuous activity, carrying heavy loads and wearing equipment.  During the spring and summer months they mitigate the impact of the higher ambient temperature to cool trainees down – such as starting at sunrise or running them through Dartmoor’s many streams.

With the OBAN and the data it feeds back to instructors – there’s not total coverage yet over Dartmoor to provide continuous live feedback throughout the 30-miler but it should be available in the new year as the tech develops – this next step of increased capability is hailed as a ‘game changer’ by staff at Lympstone. 

More than 200 recruits have benefitted from the system to date. The medical team is certain the life of one trainee has been saved, and a couple more were treated in good time without serious impact on their path to earning the green beret.

“The biggest win for us is not just the wearable technology, though it is exciting and cutting edge,”

explained Dr Ross Hemingway.

“It’s also the training and education around it. It’s about having a wider understanding and knowledge of exertional heat illness across the training centre and wider defence.

“The OBAN is an additional safety measure to flag individuals at greater risk of exertional heat illness so we can provide a robust dynamic risk assessment during high risk arduous trainings serials.”

“The medical and training teams at CTCRM have a much greater understanding of the risks, signs and symptoms and management of Exertional Heat Illness. We are much better educated, prepared and trained to deal with heat illnesses than we were five to six years ago.”

When heat stroke occurs the goal is to reduce the core body temperature to below 39.5°C within 30 minutes to limit damage to the body’s cells.

‘’Rapid and effective cooling of heat stroke casualties in ice cold water reduces the risk of long-term morbidity and mortality. With the introduction of this capability we have definitely saved one life and prevented long term complications in several others.” 

The programme at the Commando Training Centre has significant potential across the entire Armed Forces and the team are working with the Defence Safety Authority and other departments and units to share their expertise and findings.  

A significant number of cases at the Commando Training Centre are due to known risk factors such as previous heat illness, infections or injuries – which some trainees may try to hide initially.

However, some casualties have no obvious underlying cause for their episode of exertional heat illness.

Therefore, research is also being undertaken at CTCRM in conjunction with Liverpool John Moores University and the British Army Recruit Health and Performance Research Teams to better understand novel risk factors in exertional heat illnesses.

“It’s not necessarily the guy at the back of the pack on a march you should be worried about, but the person at the front, all charged up, leading on his comrades, utterly motivated to finish,” said Major Nielsen.

“He may be hiding a cold, an upset stomach, stress, suffering from lack of sleep or some other illness because he wants to win. These are the ones who suddenly ‘heat up’ and suffer heat illness with no prior warning.”

The MOD launched a new heat illness prevention policy in October 2020, written hand-in-hand with the front line for the front line.

Following that policy has saved at least one life and a suite of new heat illness prevention training modules are now being rolled out via the Defence Learning Environment to individual personnel and commanders.

You can find the policy here: Management of health and safety in defence: arrangements (JSP 375 volume 1, Chapter 41) - GOV.UK (

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