The physical demands of a world-record breaking polar expedition

Polar explorer Sam Cox tells us what it takes to attempt a world first solo unsupported Antarctic expedition. 

Humans have always attempted to push themselves to extremes, whether in harsh unforgiving environments or over huge distances. 

As an Antarctic explorer, Sam Cox is set to do both. 

This November he departs the UK for the Antarctic where he is attempting a world-record breaking expedition to complete the first solo, unsupported, crossing of the continent. 

But what does it take to embark on such an epic adventure? 

We caught up with Sam ahead of his expedition to discuss the physical requirements he will need to complete his eighty-day adventure. 


Sam will be experiencing some of the harshest environments on the planet. With temperatures plunging to -27 degrees (and occasionally colder) Sam’s body will have to adapt to live in this unforgiving climate. 

The good news is that the body is a complex machine capable of adapting. Training in similar environments like northern Sweden and Norway will help Sam to recognise and manage the conditions he will be working in. 

Sam will be skiing for long periods in extreme negative temperatures, so will also have to manage his own body temperature through his work rate, clothing, and day-to-day life management. 

He doesn’t want to overheat and sweat – that would cause a whole new set of problems when it then freezes! 

“Every day when I pack up and leave camp, I need to start feeling pretty cold,” said Sam. “However, the work rate of skiing and pulling a sled quickly warms you up.” 

Duration and intensity  

Sam is planning to ski for between 10 and 12 hours every day, across the two-month expedition, so there will be long days on the ice. Managing his work rate will literally be difference between aborting and finishing the expedition; and even staying alive. 

Throughout the expedition he is therefore aiming to maintain a consistent level of exertion which will be the equivalent of a “brisk walk up a hill”.  

“I like to call it conversational exercise,” added Sam. “So, the level of intensity where you can maintain a conversation without getting out of breath. It’s a slow and steady progression across the ice. Some might call it a plod!” 

However, maintaining a consistent level of work rate will be affected by an array of external and physiological factors. “The type of ice I’m travelling over, the obstacles I need to get over, wind direction and speed, ambient temperature and weather conditions can all play their part in the distance I’ll cover while maintaining the same level of exercise intensity. 

“On the ice I could measure my heart rate to give me an indication of how hard I’m working. However, in reality I’m not going to want to dig through layers of clothing on a regular basis to check the display, so an understanding of my perceived exertion, literally how I feel, will almost definitely be most accurate way of maintaining a steady work rate.” 

Cardiovascular fitness 

It goes without saying that you can’t take on an extreme feat of endurance without a significant base level of cardiovascular fitness. However, the fitness required for an expedition like Sam’s is very different to that of an ultra-runner or rugby player. Sam needs to be fit for the task ahead. 

That means that Sam’s body must be conditioned to endure low intensity exercise over a long period of time. 

This starts in the gym with long low-intensity sessions and extends out into the mountains where Sam has spent time developing multi-day training opportunities to replicate the conditions and level of intensity he will experience during the expedition. 

Over time, Sam’s heart, lungs, muscles and circulatory system have all being trained to work for long periods at that low intensity.  

Sam said; “Am I the fittest I’ve ever been? That’s a difficult question to answer. The answer would be no if you’re talking about running or explosive activities like rugby that I’ve played in the past, however for low intensity endurance work I’m in the best shape ever. 

“And the reason for that is that I’ve been preparing my body over the last two years to cope with the environments and intensity I will experience on this expedition. I’ve had to train my body for a different type of fitness.” 


On an expedition of this nature it will not always be a consistent smooth steady state of exertion. There will be situations where Sam will be required to use explosive strength.  

As part of his preparation Sam will be pulling a sled packed with over 160 kilogrammes of kit. That’s over 25 stone, or the equivalent of two fully grown men. 

“Although heavy, the effort required to pull the sled over uniform ice is significantly less than carrying a rucksack,” said Sam. “It does, however, require a fair bit of strength to get over that initial inertia – but once you’re going it’s about maintaining a steady even pace, keeping the connection between me and the sled as consistent as possible.” 

However, the ice will not be consistently flat, and Sam will need to navigate and manage the 160-kilogram sled over ice waves, called sastrugi, some of which can be over a metre tall, and other obstacles on the way to and across the Antarctic plateau.  

Core strength and the ability to manoeuvre his sled around or over these obstacles requires significant levels of core muscular strength.  

Fortunately, Sam has developed good upper body strength; focussed weight training in the gym has also enhanced this to help him cope with manhandling his sled over obstacles. 


In any feat of endurance, efficiency is key.  

Efficiency can be achieved through planning, choice of route, and of course good technique. 

“That’s something I’ve really focused on this year,” added Sam. “The more efficiently I can travel across the ice, the less weight I’ll need to carry and the quicker I’ll reach my goal. It could even mean the difference between a successful and aborted expedition. 

“Efficiency savings are compounded due to the duration of this expedition. If better technique allows me to travel an extra 500 metres a day, that could potentially add up to 40 kilometres difference and days of saved time, by the end of the expedition.

“I’ve been specifically focusing on my skiing technique to make sure I’m as efficient as possible whilst pulling such a heavy load behind me.  

“With this comes the other techniques that I’ll be required to carry out every day, such as putting up the tent, making water by boiling snow, as well as my 10-minute breaks that I’ll be taking every 90 minutes.  

“Getting quick at these small routines affords me another level of efficiency as I’ll be warm and fed quickly.” 

Food and fuel 

It may not surprise you that embarking on an expedition of this nature requires a huge amount of fuel. 

It’s estimated that Sam will be taking in upwards of 7600 kilocalories a day. That’s the equivalent of over 15 Big Mac burgers, or two and a half Colin the Caterpillar cakes! 

Everybody burns fuel in a different way. Some of this is based on genetics, but the body also adapts to levels of fitness, diet and environment. 

The rate at which an individual burns through fuel is also non-linear. For example, maintaining 7km per hour on a treadmill, Sam burns just over 500 kilocalories an hour. However, go just a little bit faster than 7Km an hour, and Sam doubles his energy expenditure. This is the point at which the body switches from using fats as a source of fuel and turns to stored carbohydrates instead. 

So pacing is a critical factor that will determine how much food Sam will need. 

Fortunately, due to Sam’s training and level of fitness (possibly also partly down to his genetics) he is able to maintain a relatively high intensity before seeing a big increase in fuelling requirements.  

“If Sam’s physiology was the other way around and he was a big carb burner we would have had to completely change his metabolism to best suit the event,” said Dr Barney Wainwright from Leeds Beckett University. “Tests like the one Sam went through help to inform the team about his current state of metabolism, which in turn inform his training regime. 

“If Sam was to start an expedition like this being more of a carb burner, I think he would struggle to finish because he would not be able to carry enough fuel.” 

Genetically, Sam was born to be an Antarctic explorer! 

As it is likely Sam will be burning through his fat stores during the expedition, in the weeks and months leading up to his departure Sam will be increasing his calorie intake. This is not about consuming a high fat diet; more that he’ll be looking to consume excess calories to store for the expedition. 

Physical resilience and the ability to delay fatigue 

Often the delineation between high level athletes is not their peak physical capacity, but the ability to delay fatigue. To withstand repeated periods of exercise intensity. 

That’s quite difficult to measure, but repeated exercise over multi-day activity can help the body adapt and offset the cumulative effect of exercise. In effect you can train yourself to be more resilient.  

“One of the key markers of fatigue can be quickly tapping into glycogen stores,” adds Dr Wainwright. “This will affect the ability for people to perform day after day, what you might refer to as resilience, something that is essential for Sam’s expedition. Fortunately, that’s not the case for Sam. 

“One of the key things that happens over multi-day training is an adaptation of fat oxidation, the body’s ability to use fat stores rather than burning carbohydrates. 

“So, Sam’s current level of physiology suggests he has a natural ability for polar expeditions, and his training has prepared his body for the task ahead.” 

The only way to understand the long-term effect on the body of multi-day endurance training, would be to regularly test and assess those changes over time. 

Dr Wainwright added; “Most likely, based on the figures from his tests, Sam’s body is trained well for this world record-breaking expedition.” 

Previous data  

As Sam’s expedition is so unique, there’s very little data around the physiological requirements for taking on such a challenge. There are some academic studies, but they tend to be on a shorter, less intense model.  

Sam is breaking new scientific boundaries, using the best data, and tests, available to him.  

In fact, Sam has even struggled to get a complete map to plan his route! Breaking new boundaries, likely stepping where no human has stepped before, comes with its own challenges. 

The expedition itself 

Ultimately the human body is very effective at finding the easiest way to complete a task. Sam’s body will find the most energy efficient way of travelling, whether that be his stride length or a particular way of moving. 

Therefore, to prepare for the expedition Sam needs to replicate the conditions and intensity of the activity ahead as closely as possible.  

“Training for an Antarctic expedition is very different from an elite sports person training to be the best at his or her sport. It’s about preparing my body for the temperatures, intensity and duration of an expedition that’s likely to take up to 80 days to finish,” said Sam. 

“During the expedition my body composition is likely to change as it adapts to the conditions and physical impact of the expedition. 

“I’m now focused on preparing myself to the best of my ability so that when we take our first steps in November I’m in the best shape possible.” 

Sam has been supported by Team Forces and Resilient Nutrition to embark on this epic adventure. 

For more information, follow Sam on www.frozendagger.co.uk 

Header image: Sam Cox. Credit: Team Forces

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