Energetics of load carrying in Nepalese porters

Journal: Science

When you picture someone traversing a mountain with too much gear, you're probably either thinking about a Marine or a Nepalese porter.

Can you imagine the energy it takes to carry 175% of your body weight over 60 miles through the Himalayas? Neither can I, but there are humans who do it every week.

THE STUDY
Researchers from Belgium's University de Louvain posted up in a remote market town in Nepal called Namche. They used lemonade and cookies (oddly a diet that provided some necessary energy) to bribe porters into an observational study.

Next they weighed the packs of eight different porters and filmed them as they walked across a 10-ft platform made of force plates. Using oxygen consumption and carbon dioxide production, researchers then calculated their energy costs of loaded and unloaded walking.

Their study then compares this data with two control groups to determine the metabolic cost of this type of activity and see what makes these guys so physically talented.

WHY I CARE
Nepalese porters perform extraordinary physical feats on a daily basis. In fact, they live that story your dad told you about how he walked to school barefoot in the snow...uphill both ways!

I'm curious what they're doing differently than the rest of the humans, and if it's something I can adopt to bear the weight of my pathology book. Who knows, maybe even get some tips for an upcoming backpacking trip this Spring?

The research compared the energy expenditure with European backpackers and African women of the Luo tribe who also carry unimaginably heavy loads. What surprised me the most was that this research turned into a comparison of the energetic cost of carrying loads that were supported by their heads. The tribal women referenced here are capable of carrying an equivalent to 70% of their body mass balanced on the top of their heads. Is this the same type of seemingly miraculous endurance as the porter’s strength?

THE RESULTS
Most porters in the study carried about 90% of their body weight (around 113 lbs.). A quarter of them carried more than 125% of their weight, and the heaviest load was 175% of a 125 lb. man. That's 220 pounds! Keep in mind this occurs with elevation gains beyond 26,000 ft. (the elevation of McKinley is 20k ft.).

A typical Nepalese porter carries a load nearly as heavy as he is. Better yet though, the porter burns less energy per pound than an average backpacker would need to carry half that weight.

Previous research showed that many porters are actually overworked and don't have the best diet either, defeating any theories of foreign superfoods or mystical training strategies. Their capacity to work appears to be a combination of physical attributes like long-term endurance and acclimation development, alongside the psychological determination to make a living.

Oh, and I should also mention that they mostly run back home, covering the 60 miles in 2 days without their load. Endurance, with a capital E.

SCIENTIST SAYS
"We observed, for example, a group of heavily loaded porters making slow headway up a steep ascent out of a river gorge. Following whistled commands from their leader, they would take up their loads and labor uphill for no more than 15 seconds at a time, followed by a 45 sec. period of rest."

"So how do they do it? They might reduce the muscular work required to carry a load, or increase their overall efficiency. The actual mechanism is unknown at this time."

TAKEAWAY
If, like me, you were hoping for some ancient wisdom on endurance then, unfortunately, it’s not here. Researchers found that the only difference between a Nepalese porter and an average Joe is a lifetime of hiking with heavy gear. So there goes that dream.

A Nepalese porter will use less energy than someone doing half the amount of work. This might as well be the definition of successful training. In fact, this is as good an example as any of what the human body is capable of after years of hard work.

Researchers also noted a unique carrying style that emphasized walking slowly and taking many breaks. Porters are known to take their time, even hiking into the night to avoid moving too quickly during the day. When they avoid rushing, they are less prone to accidents - a component that allows them to maintain such a demanding job for decades, not to mention a good motto to live by.

Porters also use a cool little contraption called a tumpline to balance the weight evenly across their back and neck, instead of relying solely on shoulder strength (for you visually inclined). Could this be the hot tip we’re looking for? Well, Popular Mechanics claimed it was back in 1944.