There’s no avoiding heavy packs in mountain and backcountry hunting. You either have to load them up for a long expedition, carrying your house and all the things you need on your back. Or, you kill a big critter while out on a day hunt and have to make several trips packing it out of the hills. Relatively heavy packs are a certainty. The problem is, there’s a lot of bad advice out there on how you ought to train to carry them.

The main myth that we’re about to systematically dismantle is that you should, and only need, to train with a heavy pack to be ready for heavy packing. That dog just does not hunt. What it mostly does for you is create bad habits, cause unnecessary wear and tear, and make your hips and back feel awful on the way to an injury. Not only that, but it trains your body to fatigue much faster than it should, which not only charges a physical tax, but a high mental one, too.

Instead of just slapping a bunch of weight on your back and walking, I’ll teach you how to safely and effectively build the capacity to carry a heavy pack. We’ll cover the demands of heavy packs, the different aspects of fitness necessary to carry them, when and how to start pack training, different types of heavy pack work, and common heavy pack prep mistakes. I’ll leave you with a sample heavy pack training template.

The Demands of Carrying a Heavy Pack in the Mountains

Carrying a heavy pack in the mountains places demands on just about every aspect of your fitness besides jumping and sprinting power.

It places huge demands on your aerobic system. Your need for oxygen dramatically increases under load. Oxygen demand increases by 25% with just 20% of your body weight on your back on a 10% incline. That’s not very steep, and it’s only a moderate load. If you don’t build the aerobic capacity (how long you can produce energy) and aerobic power (how fast you can produce energy) to meet that demand, you’ll quickly fatigue while moving uphill under load. And you won’t recover from hard efforts.

Lower-body muscular endurance is also a huge factor. If you lose your legs early, you won’t have to worry about your heart or lungs — they won’t get to work hard enough. Your legs must be able to sustain work for long uphill stretches, and they need to be able to do it while still leaving gas in the tank. When your legs break down, everything up the chain takes more stress. Not only do you perform worse, but you set yourself up to hurt your hips, back, and ankles.

Relative strength is also a big demand. It is how strong you are for your body weight. Being generally strong without having a high body weight makes each step you take cost less, because each step happens at a lower relative amount of force compared to what you're capable of producing. Consider that in packing terms. You’re marching through the hills with your body weight plus up to as much as 40% more. Decreasing the cost of each step by being strong adds up.

Then there’s posture and stability. Where you carry a load, and how well you’re able to stay under it, matters a whole lot. It matters for saving energy, and it matters for avoiding unnecessary wear and tear. Now, having a pack that fits you and that’s loaded with good weight distribution is likely the majority of this battle. However, if you can’t maintain good posture it’s difficult to keep the pack in the right place on your back. It will also be difficult to breathe effectively. On top of all that, stable joints in a bodily frame with good posture distribute the load more evenly throughout your body while also better bearing the weight. Each contributes to protecting you from injury and saving you energy.

And we have the biggest factor which all of the above contributes to — efficiency under load. This is posture, gait, breathing, relative strength, muscular endurance, and aerobic development. If you can’t maintain your posture and gait, your breathing suffers, you put yourself in poor positions that drain your energy and disproportionately stress your muscles and joints, and as a result of each, you fatigue quickly while setting yourself up for injury. If you’re not efficient under load, carrying a heavy pack on flat ground will be too much, let alone hauling one uphill and downhill through the mountains. 

So, you have to build your foundation. And it starts with aerobic fitness.

Why Aerobic Fitness is the Foundation for Carrying Heavy Packs

Picture yourself on an uphill climb with all of your gear on your back. You’re packing in for a week-long elk hunt. On average, your pack will weigh anywhere from 35 to 60 pounds, trending more towards the 50 to 60 pound end of the spectrum if you’re by yourself. As you get going on the climb, your heart rate jumps through the roof right quick and in a hurry, and it stays there. You get about halfway through the climb and pause to rest. You keep waiting, but your heart rate won’t come down. Then, you start climbing again and your heart rate jumps even higher. It’s day one, and you’re in big trouble.

In this scenario, your aerobic system was not developed well enough to support uphill packing. Your heart rate jumped because you didn’t train your cardiovascular system to be efficient. One of the key markers of a solid aerobic system is a low resting heart rate. Your heart rate decreases as you gain aerobic fitness because your heart becomes more efficient. It does that by increasing the amount of blood it pumps out with each beat (stroke volume) and the amount of blood it pumps out in one minute (cardiac output). When your heart can pump out more blood with each beat, it doesn’t have to work as hard. That means it can sustainably send more oxygen and nutrients to working muscles at a lower cost. You can work harder, and longer, without sending your heart rate through the roof and without as much fatigue.

When your heart rate does rise, it means that your body is working at a higher overall intensity. You recruit more fast-twitch muscle fibers instead of slow-twitch muscle fibers. Fast-twitch muscle fibers predominantly use carbs for fuel (instead of fat) and they fatigue much faster than slow-twitch fibers. This tanks your endurance because you’re not energetically efficient.

Building your aerobic system is so crucial for heavy packing because of energetic efficiency. You’re better able to use fat for fuel, which allows you to sustain work for far longer. You develop your slow-twitch muscle fibers so that your fast-twitch fibers don’t take over. This fights fatigue. And you’re better able to recover between difficult uphill sections not only because you didn’t have to work as hard to climb them, but also because your aerobic system is your recovery system. It replenishes oxygen and nutrients in working muscles while also recycling the metabolic byproducts of hard work. Without it, you rely too heavily on carbs, your fast-twitch muscles fatigue, and you can’t overcome the oxygen debt created by hard uphill work or clear the metabolites that build up to signal fatigue.

You must develop your aerobic system if you want endurance and recovery for carrying heavy packs in the mountains.

There are a lot of ways to generally develop your aerobic system. You can bike, run, hike, swim, row, and even do body weight calisthenics. But you can’t do it without spending enough time in Zones 1 and 2.

Specifically, rucking is a great tool for aerobic development. It can do all of the nice things described above while also improving your efficiency under load — if you load your pack with an appropriate weight. Eventually, though, rucking on flat ground won’t be difficult enough to drive aerobic development. You’ll have to get on an incline and/or start running (without a pack) to improve your aerobic system. Flat ground rucking with appropriate weight just won’t be stressful enough, and adding more weight will only break you down while making you inefficient without making a meaningful difference in your aerobic fitness.

As you build your aerobic foundation, you also must build your muscular endurance.

Build Your Lower-Body Muscular Endurance

What is loaded uphill hiking from your lower body’s perspective? 

It is repeated contractions at submaximal effort for a long duration. I’ll say that less like a nerd. It’s stepping up for a long time at an intensity that doesn’t require all of your effort. However, without the right training, the effort trends towards maximal as your muscles and your nervous system fatigues. Muscular endurance in general is your ability to sustain those submaximal contractions for a long time while recovering quickly during breaks. Loaded uphill muscular endurance is, mostly, your lower body’s (calves, quads, hamstrings, glutes) ability to do that while battling the slope of the incline and the extra-heavy gravity provided by your pack. Loaded downhill muscular endurance is, mostly, your lower body’s ability to repeatedly contract while controlling your descent. Without each type of muscular endurance, you lose your legs quickly. Then you’re in very big, no good trouble.

You need, and can develop, muscular endurance at all intensity levels. One of the main reasons for developing your slow-twitch fibers with Zone 1 and 2 work is because they are way better at clearing metabolic products (lactate, etc.) than fast-twitch muscle fibers. However, no matter how solid your aerobic development, your heart rate will eventually rise as you hike uphill with a loaded pack. Your fast-twitch fibers will start to do more work. If you’re not trained to handle it, metabolic byproducts will build up in your muscles, limiting their ability to contract. This happens because the byproducts signal fatigue to your nervous system, so it stops sending strong contraction signals. The muscles themselves also lose the ability to contract as often or as hard. Oxygen debt increases. You breathe harder. Your legs take you nowhere.

You must build your lower body muscular endurance if you want to carry a heavy pack in the mountains.

We do that in a few specific ways.

Tempo Strength Training

This method involves keeping your muscles under constant tension for 30 to 60 seconds while moving slowly, then starting your next set before you’re completely rested. The constant tension while moving coupled with the incomplete rest creates an oxygen debt in the working muscles that causes slow-twitch muscle fibers to grow while also getting better at clearing metabolic byproducts. It’s as miserable as it sounds. Here’s an example.

You’ll do rear foot elevated split squats (aka Bulgarians) one leg at a time, completing all of the sets on one leg before moving onto the other. You’ll do 10 reps at a 2-second down, 2-second up tempo, never locking out and never bottoming out the movement. You’ll rest for 40 seconds between sets, and you’ll do 3 total sets per leg. By the end of the sets, you will hate me. But you’ll also have taken a huge stride toward improving your lower body muscular endurance. 

High-Intensity Continuous (HICT) Step-ups

HICT comes at muscular endurance from a different angle. Instead of training your slow-twitch muscle fibers, it trains the aerobic capacity of your Type IIa fast-twitch muscle fibers. These are your middle-of-the-road fibers. They contract relatively fast and primarily use carbs for fuel, but they can also be trained aerobically. You drive them to function more aerobically with training. Enter HICT.

HICT is a training method used to train Type IIa fibers with hard contractions at regular intervals with enough rest between contractions to ensure you’re aerobically training the fibers. We use it in multiple ways, but we wear our packs and do box step-ups to use it specifically for heavy pack muscular endurance. Here’s an example.

Get a 12-inch box and load your pack with somewhere between 20% and 30% of your body weight. (This is for beginners. We’ll have experienced folks go heavier.) Do one, very forceful step up onto the box every 5 seconds, alternating legs each rep. Do this for sets lasting anywhere from 6 to 20 minutes. Each step up must be done with maximal intent — meaning you have to make that shit forceful. And you can’t let your heart rate sky rocket, otherwise you’ll start recruiting too many of the wrong kind of fast-twitch muscle fibers, negating the whole point. Letting your heart rate creep into Zone 3 is fine. Getting higher than that ain’t fine.

Incline Treadmill Hiking and Stairclimbing

The incline treadmill and the stairclimber are useful for building uphill muscular endurance. They’re especially useful for flatlanders without access to terrain. We use each for a lot of Zone 1 and 2 pack work. But we also use them to do Zone 3 work and lactate threshold intervals; each trains uphill muscular endurance making your legs more efficient at using carbs for fuel while also improving how fast they clear and recycle byproducts. 

If you have access to terrain with good, long climbs, you can substitute the actual mountain for the treadmill and the stairclimber.

When and How to Start Pack Training

Well, barring any muscle and joint injuries you might be dealing with, you could start right now. I’ll upgrade that to could to should if you have limited pack experience. How you start and how you progress is very important.

We know that efficiency under load is best challenged and trained at around 20% of body weight. That’s the point at which you can maintain your gait while also building the breathing mechanics and postural integrity necessary to build resilience for heavier weights. We also know you start losing that efficiency if you regularly train with more than 30% of body weight for extended periods. So, most of your pack training should be in the 20% to 25% of body weight range.

However, you should start at a lighter weight if you’re new to rucking and pack training. This is also the case if you’ve had a long break from time under your pack. In either case, you should start with about 15% of your body weight and progress up to 20%. And you should start by increasing distance first. Here’s a simple progression.

Start with 15% of your body weight for a few miles at a time. Once that’s easy, either ruck more frequently or do some longer single workouts for longer distances or times. Then, cut the distance back a little bit and bump up to 20%. Throughout this process, you can start adding in lower inclines around 8% on the treadmill to build up tolerance for uphill work.

As you adapt to all of that, and it gets easier, start adding in steeper inclines. Progress by adding time or distance.

We do it this way because it’s best to increase volume (distance or time) before adding intensity (weight or incline). Increasing volume first makes you more efficient and resilient before adding more weight into the equation. It allows your entire body to adapt to carrying weight before you make it more difficult.

Then there’s a follow up question. What training methods should you use with heavier packs?

Different Types of Safe Heavy Pack Training

Before we go into this, I’ll say again — once you’re past the initial stage and you’ve built up to 20% of body weight, most of your pack training should be done between 20% and 25% of your body weight. That said, there are times when it’s appropriate to go heavier. You just have to use the right methods, you have to do them the right way, and you have to earn your way up to them. Here are a few that work.

Incline Treadmill and Stairclimber

Continuous uphill work on the incline treadmill or stairclimber is a safe way to introduce heavier packs. The environment is controlled and you’re steadily moving in one direction with very little deceleration, or need to slow yourself down. This keeps you from putting too much stress on your joints. We’ll have some members that have earned it, and can benefit from it, do incline treadmill or stairclimber workouts with as much as 35% of body weight on their backs. However, we only do a handful of these workouts spread out throughout a training block. We don’t do them all the time. Also, folks who are acclimated to heavy packs can do heavier pack work on well-groomed mountain trails. 

HICT

Earlier I mentioned HICT as a means to develop the aerobic capacity of your fast-twitch muscle fibers for better muscular endurance. It’s also a safe way to acclimate to heavier packs. The environment is a little less controlled than on a treadmill or stairclimber, since you’re stepping onto and off of a box, but it’s still pretty controlled. I’ll do HICT sessions with as much as 50% of my body weight in my pack, and some of our members have earned their way up to that kind of weight, too. But it takes time and consistency with lighter loads to get to that point.

How to Know if You’re Ready for a Heavy Pack

After you’ve progressed up to 20% of body weight, the best way to know if you’re ready for a heavier pack is to test. You can do that with our 10-Minute Step-up Test and Pack Capacity Calculator.

The Packmule 10-Minute Step-up Test

The 10-Minute Step-up Test is simple, not easy. 

Here’s the equipment you need to do it:

• 12” box

• Chest strap heart rate monitor

• Pack loaded with 20% of your body weight

• Rep counting app on your phone

Here’s how to do it:

• Get all of your equipment ready. Chest strap on, heart rate monitor app ready, app counter up, box on the floor, pack loaded with 20% of your body weight.

• Before you strap on your pack and get going, do 15-minutes of light activity to warm-up before the test. This brings your aerobic system online.

• After the 15-minute warm-up, strap on your pack, start up your heart rate monitor, get your counting app up, press start on your 10-minute timer, and start doing step-ups, alternating legs with each step.

• Move at your FASTEST SUSTAINABLE pace for 10 minutes. That means it should feel pretty hard, like a 7 or 8 out of 10 on the effort scale. However, you don’t want to come blazing out of the gate and then tank. It’s best if you build speed over the first minute. Be sure to hit your rep counter with each step.

• A step counts when the stepping leg is fully locked out at the hip and knee, and the bottom of your non-stepping foot touches the top of the box.

• At the end of the 10 minutes, stop your heart rate monitor and record your average heart rate and max heart rate. Check your rep counting app and record the total amount of steps.

Now that you know how to do the test, let’s talk about why it’s a solid tool for predicting your packing capacity.

WAIT, before we move on, I need to reiterate one more thing about this test. It’s based on a common mistake people make when doing it. Move at your fastest sustainable pace. If you are at all comfortable while doing this test, you’re doing it wrong. It should feel hard. Not so hard you’re not sure you can make it through. But it should suck a little. If it doesn’t feel that hard, you won’t get an accurate score. You have to push yourself.

The Pack Capacity Calculator

Once you finish the 10-Minute Step-up Test, you can plug your numbers into our Pack Capacity Calculator. When you plug in your body weight, your pack weight, and the number of step-ups you completed in 10 minutes, it gives you a read out that tells you how heavy of a pack you could likely safely manage for uphill hiking without grinding yourself into the dirt. 

You can download it for free here >> Pack Capacity Calculator

If you’d like to read about how I devised it before you download it, you can read this article.

Common Heavy Pack Preparation Mistakes

I wouldn’t be doing my job if I didn’t tell you what to watch out for when prepping for a heavy pack. Here are the common mistakes hunters make.

Going Too Heavy Too Soon

You might have seen this one coming. But it’s way too common for my comfort. When you go too heavy too soon without following a proper progression, you place unnecessary wear and tear on your body. That’s a nice way to say that you set yourself up to get hurt. You will beat up your back. You will beat up your hips. And there’s a real good chance you’ll absolutely shellack your knees. But wait, there’s more! You’ll also train yourself to be inefficient under load. You’ll do that by training yourself into bad postures and breathing mechanics. As a result, you’ll fatigue much faster because you’ll waste a lot of energy. Follow the sensible progression laid out earlier.

Not Training Aerobically

Pack training is just like anything else, you can’t just jump into the deep end of the pool. Without an aerobic base, you will have poor endurance under your pack. So, you can’t skip building that foundation. Otherwise, you’ll jack your heart rate up every time you start moving and wear yourself out during the first uphill climb. Build your aerobic system. You can use pack training as part of your plan to do this.

Not Using Strength Training to Support Pack Work

Building your relative strength makes you more efficient and resilient. You need each of those things to manage heavy packs. Also, getting stronger bridges the gap between your 20% to 25% body weight pack work and the heavier packs you’ll carry in the field. Strength training builds the raw materials necessary to safely and effectively carry heavy packs.

Too Steep of Incline Work Too Soon

Say it with me kids, volume THEN intensity.

This falls in line with going too heavy too soon. Get efficient under your pack on flat ground and shallow inclines before you start ratcheting up to the steep stuff. Prepare your legs with some muscular endurance training, build your aerobic capacity, and lock in your posture and breathing. Then make the incline steeper.

If you want to get on steeper inclines sooner, just go hike without weight or get on the incline treadmill or stairclimber unloaded.

Progressing More Than One Variable at a Time (Volume, Weight, Incline)

If you try to add volume, weight, and incline to your training at the same time, you will introduce too much stress. Your body doesn’t adapt well to training when you give it too much stress at once. In many cases, it doesn’t adapt at all. Training just tears you down and you don’t have enough resources remaining to rebuild. One at a time.

Sample Heavy Pack Prep Program Template

With our bases covered, I’ll lay out a sample, three-month training template to work you up to heavier packs. We’ll start by assuming you’ve worked your way up to managing a pack with 20% of your body weight.

This a sample, an example, of how you could progress your heavy pack training. There are different paths you could take. But it will work.

Month 1

• 2-4 hours of aerobic training. You can use rucking for up to ¾ of this volume. Fill in the rest with hiking, biking, running, etc.

• 2 days per week of strength training.

Month 2

• 2-4 hours of aerobic training. You can use rucking for up to ¾ of this volume. Fill in the rest with hiking, biking, running, etc.

• 1 day of strength training

• 1 day of tempo strength training.

• Progress your ruck training by increasing the incline on one of your rucking sessions while maintaining your heart rate in the aerobic training zones (1&2)

Month 3

• 2-3 hours of aerobic training. You can use rucking for up to ½ of this volume. Fill in the rest with hiking, biking, running, etc.

• 1 day of strength training.

• 1 day of HICT.

• 1 day of Zone 3 rucking on an incline treadmill or stairclimber.

Heavy Packs are Earned Through Smart Training

You carry a heavy pack well by building the raw materials that allow you to do it. It’s a process. It takes time and consistency. You can’t skip steps, and you must progress intelligently. If you give yourself enough prep time, you utilize the info I laid out in this article, you will carry a heavy pack well in the mountains.

Want to know what kind of weight you can manage right now? 

Do the Packmule 10-Minute Step-up Test, download our free Pack Capacity Calculator, and plug in your numbers.

Download free >>> Pack Capacity Calculator