With no roads, tourists to the Himalayas - home of the world's highest mountain, Everest - need local men and women to carry everything for them. And this means porters are everywhere in the mountains.
At 4,000m altitude sickness became acute
Navin Singh Khadka of the BBC's Nepali service took some time to travel with these hardy men, many of whom are only teenagers.
My home country of Nepal is so high, you can get sick just walking to the base camps at the bottom of the mountains.
At this altitude the porters carry baskets weighing more than 50kgs, as well as all the local goods that villagers need.
But this is a bad time in Nepal. Conflict between the government and Maoists sees gun battles reported every day, with the army bombing villages from the air.
But life must go on for the porters, who scratch out a living performing their service for the dwindling numbers of trekkers.
A good place to die
While I drag my feet and can hardly move, they stride confidently down the mountain.
"The tourists are ok, but they don't tell us about themselves," says one, as I struggle to keep up.
"They're pretty slow on the trail. We're always ahead. But that seems to make them happy - they get to see their luggage well ahead of them."
Another porter talks of the time he went with an Indian group to Tibet. One of the party developed chest pains - and shortly afterwards died.
The climb up the mountainside is dramatic - and dangerous
"The problem is that Indian trekkers don't tell us anything in advance, even if they're ill," he says.
"They're happy to die, because they think that this is the home of the Lord Shiva. It's a good place for them to die.
"But it definitely makes you feel bad. It could happen to one of us - you never know. High-altitude sickness could happen as well."
Altitude sickness occurs as breathing becomes more difficult above a certain height. Blood comes out of the lungs, you get headaches, terrible confusion, and eventually, if untreated, death can occur.
But despite the risks, porters are becoming a more common sight at these dangerous higher altitudes - where Sherpas have traditionally dominated.
Due to the ongoing Maoist conflict, there are now dwindling numbers of trekkers. So the porters and Sherpas fight over the small number of tourists who are still coming - and tensions are rising as the lowland porters trek higher and begin to encroach on Sherpa territory.
Beer and jokes
The porters feel the Sherpas look down on them in more ways than one. One recalled that on one trip, the Sherpas were staying in a "dining hall full of space - but they still made us sleep outside".
"What would these people do if we did not bring the tourists here?" he added.
"They would be selling potatoes, and grovelling to us to buy them."
The snow has come very late this year - and very deep
Meanwhile, some porters complain that guides are "exploiting" them. One trick is to set off on a trek, and only when it is well under way tell the porters they will not be paid for rest days.
The porters have their own banter and their own beliefs. One is that if a porter has sex on the way up the mountain, the snow will get consistently heavier until he dies.
However, not all the young porters - many of whom are teenagers - are convinced.
"We can do anything, because we are very strong," said one.
It has been a strange year in the Himalayas. It did not snow at all in the winter - and now in spring, when it should have been clear, it has started snowing.
At around 4,000m, we reach Tyangboche. It is a bleak place - just a monastery and one or two lodges for trekkers and porters. From here, you would have to walk for a week to reach the nearest road.
What can be done for fun in such a desolate place? Beer, playing cards and jokes, say the porters.
They also discuss politics - as I discover when I accidentally leave my microphone switched on.
One of the porters, I hear later when I play back the recording, thinks I am a spy. But another dismisses him - "if the entire government has done nothing, what can one man do?
"With the country reeling under all these problems, the BBC comes and talks to lowly porters. That's not going to solve anything."
They add that what they really do need are more trekkers. They worry about what they will do if the tourists stop coming - and with the weather worsening, this is now more likely than ever.
With snowfall up, trekker numbers are down
It was shortly after this that I developed altitude sickness myself. I was very ill all night and struggling to breathe.
In the morning, a helicopter came to take me out. There was no way I could go further up.
After a 20-minute flight I am 1,000 metres lower, in Lukla hospital, and feel almost normal again.
The doctor here is a Sherpa. He sees around 6,000 tourists a year, and a huge number of porters. Injuries to ankles and knees, from falls while carrying heavy loads, are the major hazards.
And yet around the corner from the hospital is the Karma Internet Cafe - and inside are porters and Sherpas desperately using the net to find work.
One of them, Tendashering Sherpa, told me that this was his only choice in life.
"There were no jobs, and I had to earn. My family background is mountaineering. And so here I am, climbing mountains in the Himalayas," he says.
"For us, it is all about business. If we have one successful climb, we think we will have more groups in the future. So it's always about making the group have a successful time.
"But I would not have done this if it was not for my wife and family. I would rather have been a farmer - and have none of the same risks."