Let's get one thing out of the way. We are not going to tell you running is bad. Plenty of us run, and several of the events we train for involve a lot of it. What we will tell you is why, on most weeknights, we would rather put weight on our backs and walk. Some of that is opinion. Where there are real numbers, we will give you the numbers.
Running burns more per minute. Rucking closes some of the gap.
Researchers rate activities in METs, a measure of how much energy they cost. Brisk walking at around 3.5 to 3.9 miles an hour is rated 4.8. Running at 5 miles an hour is rated 8.5 [1][2]. So minute for minute, running wins, and anyone who tells you rucking burns as much as running is selling something.
Adding weight does change the math for walking, though. The same reference lists slow walking at 2.5 miles an hour as 3.0 METs with no load and 4.8 with a 40 pound load, about 1.6 times the work at the same speed [1]. Our fair reading is that a 30 to 40 pound ruck makes a walk somewhere around a third to a half harder. You will see claims of three times the calories. We could not find evidence for that.
Rucking is easier on the body with each step
When you walk, the peak force through your legs on each step is about 1 to 1.5 times your body weight. When you run, it is about 2 to 2.9 times, and it climbs as you speed up [3]. That is the main reason people whose knees or hips complain about running often find they can ruck.
Be careful with the word low impact, though. A pack adds to the force on every step and changes how you walk: more forward lean, shorter stride [4]. The honest phrase is lower impact than running, not no impact.
Running injuries are common. Rucking has its own.
A review of the research put novice runners at about 18 injuries per 1,000 hours of running, and recreational runners at about 8 [5]. That is a lot of sore shins and knees.
We would love to give you the matching number for rucking, but nobody has measured it for people like us. What exists is military research, at loads far heavier than a club ruck, and it lists the usual suspects: foot blisters, stress fractures, back strain, knee pain, and nerve irritation from shoulder straps [6]. Almost all of it traces back to too much weight, too many miles, too soon. That part you control.
Where running wins
- Time. One large study found walkers needed about twice as long as runners to do the same amount of work [7]. If you have 25 minutes, run.
- Top-end fitness. Harder, faster training is the better tool for raising your ceiling.
- Simplicity. Shoes and a door.
The encouraging part of that same study: when walkers and runners did the same total amount of work, their reductions in risk for high blood pressure, high cholesterol and diabetes were similar [7]. Walking gets you there. It just takes longer.
So why do we ruck?
- We can talk the whole way. A ruck moves at a pace where conversation works, which is how a workout turns into a club.
- Everyone can do the same ruck. A fast runner and a slow runner cannot really train together. With a ruck, the strong one adds weight and the group stays together.
- It carries over. Carrying a load for miles is exactly what a GORUCK Challenge or a Spartan carry asks of you.
- We can still do it tomorrow. For a lot of us, the day after a ruck feels better than the day after a run.
You do not have to pick a side. Run if you love running. But if running has never stuck, or your joints have started voting against it, put twenty pounds in a backpack and walk three miles with us. That is the whole experiment.