Editor’s Note:
We’d like to thank Jordan and the Mountain Tactical Team for allowing us to re-publish this informative piece that originally appeared on www.mtntactical.com. If you take your training as seriously as you do your hunting gear and skills, the Mountain Tactical Institute is one of the top sources for training and training related information around.
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As the coaches and clients that train at the Mountain Tactical Institute looked deeper into the physiological demands and effects of rucking, interesting questions guided us to interesting answers. As you might imagine, when certain questions are answered, more questions arise. The more we dove into the subject of ruck (or backpack) training the more we focused our attention on narrower, more novel queries. In exploring this critical (for our clients) subject, five useful pieces of info came to light. These rules of thumb as we think of them, can be applied to loaded running as well.
1) One pound on your feet equals five pounds on your back.
2) One pound on your feet equals five percent more energy expended.
3) An extra one percent of load carried (relative to body weight) makes you six seconds slower per mile.
4) A ten percent grade incline cuts your speed in half.
5) Going up slows you down twice as much as going down speeds you up.
Now, let’s expand on each of these bullet points a little more in depth.
1) One pound on your feet equals five pounds on your back:
This old adage from mountaineers holds true, with confirmation coming from a 1984 study from the U.S. Army Research Institute. They tested how much more energy was expended with different footwear — boots and shoes — and concluded that it takes 4.7 to 6.4 times as much energy to move at a given pace when weight is carried on the shoe versus on the torso. Of course, this finding came forty years after the commonly accepted genesis of this nugget, Edmund Hillary’s 1953 ascent of Mount Everest. In practical terms, this means you could carry a half-gallon more water — a little over four pounds — if you buy boots that are one pound lighter, which isn’t hard to do. That’s a lot of extra water you don’t have to pump, filter, gather or hike down to find.
2) One pound on your feet equals five percent more energy expended:
Heavier boots don’t just impact your energy expenditure because of their weight. They’re stiffer and less responsive as well. This reduces the efficiency of your body’s stretch reflex when interacting with the ground. Five percent doesn’t sound like much though, so how does five percent translate to run times? Well, five percent would slow your mile pace by thirty seconds, depending on how long you’re running. But, the faster you attempt to run, the greater that five percent will impact your performance.
3) An extra one percent of load carried makes you six seconds slower per mile:
Carrying weight on your torso isn’t free of cost though. As the rules state, adding one percent of extra load to your body weight makes you six seconds slower per mile. The average fighting load for a regiment is thirty-five percent — about sixty three pounds based on a one-hundred-eighty pound male — which means a soldier’s mobility is hampered by more than three minutes per mile. If you work that backwards, that equates to a twelve second slower one hundred meter sprint, which could double a fast soldier’s one hundred meter time. Admittedly, this math assumes a linear relationship, which isn’t truly realistic. The broader point is that no matter how fast you’re moving, and how much you’re carrying, you’ll be moving slower. And the faster you want to move, the more you’ll be impacted.
4) A ten percent grade incline cuts your speed in half:
Grade greatly affects speed. By “grade” we mean how much terrain incline or decline there is. Percent grade is a term that describes how much you go up versus how much you go forward. Ten percent, for example, means that for every ten feet you travel forward, you’ll travel one vertical foot. In terms of angles, ten percent equals 5.74 degrees. A 5.74-degree angle doesn’t seem like much until you’re humping up it mile after mile. You’ll know how hard it is because you’ll move twice as slow over it than over flat ground with a given load. That last little part – with a given load – is important. A ten percent grade will cut your speed in half no matter if you’re carrying forty-five pounds or eighty. This, perhaps, has training implications. Let’s say you know you have to make a ruck for time over hilly terrain. You find the average grade of the ruck terrain is ten percent, but don’t have the same terrain available to you — let’s say you live in Florida with flat terrain — but have to ruck in the mountains of North Carolina. Given the load you’ll carry, you can find out what your pace needs to be over flat ground to properly prepare for the average grade of the testing scenario. So, if you have to make 2.5 miles per hour over the ten percent grade terrain, you should train at 5 miles per hour on flat terrain. Now, again, the math here assumes a linear relationship between grade and speed, which most likely isn’t true, but using the rule will ensure your training will provide a proper time buffer.
5) Going up slows you down twice as much as going down speeds you up:
Don’t believe you’ll make time up on the other side of the hill. You won’t. You’ll only make half the time up. Famous running coach Jack Daniels provides numbers to this relationship, saying that an incline will add twelve to fifteen seconds to your mile time while a decline will only cut eight seconds off your mile time. Why don’t you gain as much running downhill as you lose running up? Braking forces. As you descend, you have to break your speed with your quads to keep yourself under control. The steeper the downhill, the more braking force is applied. So, although this point uses running focused data, the rule applies to rucking, especially as it relates to the braking forces required to absorb the impact of hiking/rucking downhill under load.
FOR A DETAILED LIST OF SOURCES REFERENCED PLEASE SEE THE ORIGINAL ARTICLE ON MTI’S WEBSITE
