How far can we go?

Now that I have radically reduced my packweight, I realize that new possibilities have opened up to me. In particular, it is clear that I can travel faster, hike comfortably for more hours in a day, and hence travel farther in one day than ever before. I am not the first to arrive at this conclusion, and in fact a number of authors have explored this topic in depth. An article by Roman Dial (2006-05-24) on the BackpackingLight website really got me thinking, and I am taking the liberty to summarize some of his conclusions here.

Each person, depending on their level of fitness and training can hike some number of miles in a day with no load on their back. This figure establishes a base value for each person than be be used to estimate distances covered carrying various loads. Roman (who is a wilderness racer) says he can cover 70 miles in a day. This is hiking for 17.5 hours at 4 miles per hour. A more reasonable value for a typical in-shape backpacker might be 40 miles (10 hours at 4 miles per hour). Each pound carried then reduces the number of miles per day travelled. Roman Dial estimates a penalty of 1 mile per day for every pound carried. I argue below that a penalty of 0.5 mile per day is more accurate for people not operating at elite levels with light loads (i.e. most of us).

On page 23 of Ray Jardine's book "Trail Life" (2009) is a graph of pack weight versus miles per day travelled. He says that this data was obtained by analyzing records of his and Jennies PCT hikes. I used a ruler to scale several points from this graph, and then fit a line to the points I scaled:

This fit crosses the Y axis at approximately 37 miles per day, which is a believable number for the number of miles hiked in a day by an individual in excellent shape carrying no load. The fit line drops 0.52 miles per pound of load, in other words for every 2 pounds on a persons back, he can cover 1 mile less each day. (Note that Ray's data was originally shown as a smooth parabolic curve). Note also that Ray Jardine says his typical hiking rate is 2.75 miles per hour.

Roman Dial is an interesting fellow to pull data from. He is an adventure racer, and the fact that he even mentions going distances like 60 miles in a day makes someone like me wonder if any information extracted from his experiences would be relevant to what I do. But I think his experiences are very relevant. First off he says that weight kills both speed and distance.
Some figures he quotes:

I used a ruler to scale data from Roman Dials article. Then I fit a parabola of the form y = a + b / x to this data (which fit his data very nicely) and plotted it along with Ray's data. For pack loads of 20 pounds and up, the data is almost identical.

I show two reference lines in the plot above, one with a slope of -0.5 miles per pound added (the blue line), the other with a slope of -1.0 miles per pound added (the purple line).

Given that Romans curve is a parabola, quoting a linear relationship like a 1 mile per pound penaly can only be correct over some range of the curve. Perhaps the most important conclusion to draw from a curve like this is that the greatest benefits of dropping pack weight are with light packs. If you are already carrying a 50 pound pack, an extra pound is not going to slow you down as much as if you are carrying a 20 pound pack and add an extra pound. So if you are ever thinking along the lines of "my pack is so light, it won't matter if I toss in something extra", you are completely wrong.

Conclusions

Although Roman Dial quotes the figure of a 1 mile per day penalty per pound on a persons back, I think this is more relevant to the somewhat unusual domain he operates in with really light pack loads. Most folks won't be covering 60 miles per day with a 10 pound pack. Even for him, with loads of 20 pound and up, a 0.5 mile per day penalty per pound carried is a better match to his data. For most lightweight backpackers, the 0.5 mile per day per pound penalty is correct over the full range of pack weights they are likely to carry.

Clearly, carrying a lighter load allows a person to either hike faster, or for more hours per day, or both.

Footwear

An oft mentioned principle is that a pound on your feet is like 5 pounds on your back. (If we accept this, then wearing my 4 pound pair of boots instead of my 2 pound pair of running shoes would be like 10 pounds on my back, and impose a 5 mile per day penalty.) On page 123 of Ray Jardines "Trail Life" he says that he figures that for every 3.5 ounces he removes from the weight of a pair of shoes he gains 1 mile per day. This scales to a 4.6 miles per day penalty for every pound in a pair of shoes, which is pretty close to the 5 miles per day penalty often quoted.

Other factors

A number of factors enter in to this "range estimation". The following is a list of things that I know affect me:

Roman Dial mentions in his article that food can substitute for sleep and vice-versa. He makes a number of calculations based on 3 pounds of food per day, but says that 2 pounds per day is a good target for trips of an intermediate length. He carries less on shorter trips, more on longer trips. He hopes to manage 500 miles in 3 weeks by training himself to a 75 mile per day unloaded base level, carrying a 10 pound base weight and 2 pounds of food per day. Well, well, a different realm than mine.

My own experience

Here is where the rubber meets the road. What can I manage at my "decent" level of fitness. I have done two "stout" day hikes since compiling the above, each interestingly enough covering a distance of almost exactly 12 miles.

Mt Lemmon - June, 2009. Covered 11.9 miles with 2000 feet of elevation gain (and loss) at an average elevation of 8000 feet in perhaps 7 hours or so (somewhat less than 2 miles per hour).

Mt Wrightson - July 13, 2009. Covered 12.1 miles with 4000 feet of elevation gain (and loss) at an average elevation of 7500 feet in exactly 6 hours. Almost exactly 2 miles per hour on the average. It took 3.5 hours to reach the summit (attempting to run the whole way), and 2.5 hours to get down. Beat my joints up big time, probably won't try this again.

These hikes were done with little or no pack weight on good, albeit steep, trails. They seem to bear out a hiking speed of 2 miles per hour, and a daily base distance of 12 miles. A greater pack load, off-country travel, or higher elevation would be expected to change this. On the other hand some of my previous days with 40+ pound packs have covered only 5 miles or so, so if I can consistently cover 10 miles per day, I won't be unhappy and can strive for more.

Have any comments? Questions? Drop me a line!

Tom's hiking pages / tom@mmto.org