A marathon requires long time, whereas a sprint needs short time.
Trekking in the Himalayas is more like a marathon than a sprint for nine reasons:
Trekking requires more energy than simple walking. If you go for a sprint that itself a high impact activity, in no time you will exhaust all your energy.
Spend energy judiciously to complete your trek.
2. Goodbye to gravity and hello to altitude
When you trek in the Himalayas, you intentionally betray the gravity. You cannot simultaneously have both support of gravity and joys of altitude. Love for altitude literally takes your breath away, testing your aerobic fitness. This makes extra demand on your body that in turn affects your walking speed.
3. Overfriendly gravity and sick of altitude
On return, the jealous gravity tempts you into running downhill to get rid of altitude affect and probably home sickness. You stop gasping for a breath. But remember and be careful, the return is equally demanding and requiring full control over your walking speed. Otherwise you will fall face first and get the most hated injuries.
Actually, you can compensate for loss of time during slow ascents with relatively faster descents.
Quantification of speed
Here are some formulas where researchers have tried to quantify changes in the speed while going uphill and downhill:
Jack Daniels’s Running Formula
“Every percent gradient of incline (going uphill) will slow you by 12-15 seconds per mile, and every percent gradient of decline (going downhill) will aid you by 8 seconds per mile.” (Source)
Johan Kellogg’s Formula
“Every 10 feet of elevation change alters your time by 1.74 seconds, regardless of the horizontal distance covered.” (Source)
William Naismith’s Rule
A reasonably fit person not carrying a back pack or rucksack walks one kilometer in twelve minutes (5kms/hour) in a plain area.
If the person carries a moderately heavy backpack, the walking speed reduces by three minutes (4kms/hour) in the plain area. The speed will continue to fall with an increase in weight of the pack and terrain related difficulties.
If the person not carrying a back pack or rucksack walks in mountains, add 10 minutes for ascent of every 100 meters.
If the person carrying a moderately heavy backpack walks in mountains, add 15 minutes for ascent of every 100 meters.
4. Oxygen hates altitude
Even oxygen feels afraid of altitude and does not like to make a home there. The low oxygen levels, especially at high altitudes, make your body work more and harder, reducing the speed.
5. Unfrequented and virgin slopes challenge your route finding skills
If the trail is not well-marked, you will need extra time to find the route to your day destination. This process includes scanning the slopes for selecting a convenient and the shortest (not always) route.
But remember shortcut approach will not help you in finding the easiest route for entire team.
6. Natural attractions and hazards put a spoke in your wheel
Hard blue ice and deep fresh snow are popular attractions that support several adventure activities.
However, these attractions can block or hide the trail sections. Then the speed would plummet.
The hazards, including avalanches and landslides, force you to stop, take unwanted breaks, and walk slow.
7. Attractions tempt avid photographers
The mountains offer several attractions worth capturing. The attractions sometimes hypnotize avid photographers, slowing down their walking speed.
8. Body orders slow walk
If your body demands rest and snacks at regular intervals, the speed will be affected.
9. Side attractions want your attention too, increasing total trekking time
So moral of the story is Prepare Well. But do not try to be a Usain St. Leo Bolt (the world famous sprinter from Jamaica) when you are in the Himalayas. Instead, try to follow the turtle from famous folk tale The Rabbit and The Turtle: slow and steady wins the race.