Strength vs Endurance: What Actually Improves Rucking Performance

0:00 If you've been rucking for a while, you've probably asked yourself at some point, am I actually training the right way to get better at this? Should I be doing more miles, more running, more strength work, or some combination of these three? Because I suspect most ruckers are maybe just winging it, putting in extra miles, throwing on weight, and just going. But what if we didn't have to guess? That's exactly what Rob Shaul and the team over at Mountain Tactical Institute set out to answer. They ran a series of studies to figure out what actually improves rucking performance. And today, I'm breaking all that down for you so you can train smarter, avoid wasting time, and actually get faster under a ruck. You're listening to the Rucker's Edge podcast, a show all about rucking that is designed to help you improve your rucking routine, lose weight, and ultimately gain your strength and energy back.

0:48 Each episode dives into the science, stories, and strategies behind rucking. You'll learn from top ruckers, coaches, health experts, and performance specialists. who break down what it takes to train smarter, recover faster, and stay ready for the next challenge. So whether you're new to rucking or an experienced rucker that's logged hundreds of miles, this is the show for you. I'm your host, Spencer. Thanks for listening in. Before we get going, I have two things I wanted to say. First, I just want to say thank you to everyone who's been reaching out lately. I've been getting a lot of messages, emails, whatnot. You know, people sharing their stories, their progress, how they found the show. And honestly, it means a lot. If I haven't responded yet, I promise I'm working through responding to them. I appreciate your patience as I work through my inbox. I really do read each and every single one, and I'm trying to respond to each and every single one as well. The second thing I want to say, if this show has helped you in any way, it would be amazing if you could drop me a quick review or rating on whatever app you're using to listen to me right now. It helps me bring new episodes every week, and more importantly, more people looking to improve their fitness will be able to discover the podcast. So you can help someone else start or improve their rucking. Thanks so much. Okay, so here's the deal. I had Rob Shaul lined up for today's episode.

2:08 As I mentioned before, Rob is the founder and president of Mountain Tactical Institute, or MTI. And he and his team have done some really incredible, interesting work, you know, practical rucking research. being done by that team and that group. We're going to dig into the Ruck Deep Dive study series together, but you know, life happens and we had to push that conversation to a later date. But honestly, I'm not going to let the research sit on the shelf because after going through all of it, I think this stuff is too good to not talk about right now. There are some genuinely interesting findings in here that are worth sitting with, even if some of them are still early stage. So today I'm doing a solo episode. I'm going to walk you through the MTI Ruck Deep Dive study series from start to finish, what they tested, what they found, and what it might mean for how you approach your training. I do want to set expectations up front.

3:02 Some of what we're going to be covering today is well supported across multiple studies. Some of it's early exploratory type of studies and findings. And MTI themselves are the very first to say, you know, more data might be needed. I'm going to be straight with you about which is which throughout the episode, because I think that's actually more useful than just handing you a list of rules. So let's start. So the whole Ruck deep dive series started with a pilot study. It was a small study, just six guys. MTI calls their test subjects lab rats, which I absolutely love. But the results were interesting enough that they knew they were onto something and wanted to keep digging. The question they were trying to answer was pretty simple. What physical attributes actually matter for wrecking performance? And that seems like a question with an obvious answer, right? Like, just be in shape. Go run a lot.

3:57 You know, lift weights a lot. But Rob and his team wanted to actually test that assumption rather than just assume it. So here's what they measured. They measured body weight, height, front squat, and bench press maxes. Max pull -ups and one and a half mile run for time. Then two days later, everyone did a 10K ruck. If you don't do kilometers, that's about 6 .2 miles. And they were carrying 29 kilograms. And again, for those of you thinking in pounds, that's around 64 pounds. And, you know, they chose those measurements, 10 kilometers and 29 kilograms. based off a 2009 NATO study that identified it as the average fighting load for operations in Afghanistan.

4:43 So they collected all that data, ran correlations, and looked at what tracked with who rucked fast and who rucked slow. Here's where it gets interesting, at least as a starting point. In this group, the single variable most highly correlated to rucking performance was relative upper body strength. Specifically, the bench press relative to body weight. Pull -up scheme in second. Then the one and a half mile run time. Then relative front squat strength. Height and weight didn't show a meaningful correlation in this particular group. Now I know what some of you are thinking. Bench press for rucking? That sounds interesting. But here's the explanation they offered in their paper. Definitely worth considering. They said when you're rucking, especially under a heavy load over a distance, you're constantly transferring force through your midsection and upper body to stabilize that load. So if your upper body is weak, the stabilization may break down and it could cost you in speed and efficiency over X amount of miles. Let's pump the brakes for a second because this is important. Again, this pilot study was kind of small, only six people in it. MTI was very clear that they treated it as exploratory, a starting point to generate their hypotheses, not a definitive answer. So when we move on to the next study, keep in mind

6:16 we're watching MTI try to figure out if this upper body strength signal holds up with a much bigger group. Because that science is pretty good. You find something interesting in a small group, and then you go test it properly. Okay, so after the pilot study... MTI wanted more data, more subjects, more diversity, more confidence in what they were seeing in the pilot study. So they partnered with the University of Colorado out of Colorado Springs and their ROTC program to run a proper study. In September 2015, they tested 46 ROTC cadets over four days. Day one was the Army Physical Fitness Test, a two -minute push -up test, two -minute sit -up test. and a two -mile run. A couple days later, they tested one rep max front squat, one rep max bench press, and max pull -ups. Then the next day, the same 10K ruck at 29 kilograms. This is where the findings started to get kind of nuanced, because they were able to look at males and females separately, and the results were different enough between the two groups that you really can't just lump everyone together. Let me start with the women.

7:32 For female athletes in this study, rucking performance was pretty strongly tied to size, height, and weight. A combination of size and aerobic capacity are among the strongest predictors of ruck performance relative to upper body strength and also correlated fairly closely with ruck performance. It's worth noting, again, similar to the pilot study, this sample of women was small. I think it was four. So we want to hold these findings loosely. but the pattern was interesting enough to be worth paying attention to. One data point that kind of tells you how complicated this stuff gets, their fastest female ruck performer was actually the shortest and lightest athlete in the group. So size showed up as a trend in the data, but it clearly wasn't riding anyone's destiny, I guess you could say. For the men, things were more spread out. No single variable dominated the picture. The two -mile runtime was the only single variable that reached a meaningful predictive level on its own, coming in at around 34 % predictive power. But here's what was really interesting.

8:36 When they started combining variables, the predictive power jumped. For males, a combination of the two -mile runtime and sit -ups had a predictive strength of 82%. Two -mile runtime and push -ups, 75%. So for men, it was the combination of aerobic capacity and muscular endurance that started to paint a fuller picture of ruck performance, not a single thing or variable on its own. The big takeaway from study number one is that rucking performance is genuinely multifactorial. Or is it multifactorial? What I'm trying to say is no one single variable moves the needle that much by itself. It's a combination of things.

9:20 It involves aerobic fitness, strength, muscular endurance, and in some groups, body size. The mix of what matters most seems to shift depending on whether you're a man or a woman. That's not a weakness in the research. That's actually just helpful or useful information because it tells you there's no one -size -fits -all answer. Next up, we'll talk about what actually improves your ruck in the next study of the series that they did. But first, I want to take a quick break to say thanks so much again for listening to this show. If you're finding this research helpful, text it to someone that's starting or a current rucking buddy that you have. It might give them some insight on how to improve their rucking.

10:02 Alright, back to it. Okay, so now we have some picture of what predicts rucking performance. The next question, and this is the one that's really useful from a training standpoint, is what actually makes you better at rucking? So Study 2 was designed to answer exactly that. MTI took 25 of the ROTC cadets who completed both rounds of testing, put them through a six -week training program, and then reassessed everything. Same tests, same 10K ruck at... 20 kilograms. The training program was a mix of heavy barbell work, bodyweight strength training, aerobic endurance, some work capacity training, and core work. This was done five days a week for six weeks. Then they looked at which improvements in training tracked with improvements in ruck performance.

10:56 Again, let's start with the women because the results were a little cleaner. For female athletes, three things showed up that were meaningful to wrecking improvement. Front squat, so lower body strength, two -minute sit -ups as a measure of core strength, and the two -mile run time as a measure of aerobic endurance. MTI's recommendation coming out of this was that females would likely benefit from prioritizing lower body strength first, with core and aerobic work as secondary focuses. I'll say the sample size for women in this study was small enough that I treat it as a useful starting hypothesis rather than a hard rule. But it's a reasonable place to start, and it's the direction the data pointed. For the men, the picture was a little messier, and I actually think that's interesting because it suggests that male ruck performance improvements are more distributed across a wider range of factors. The most statistically significant relationship for males was between push -up improvement, so upper body muscular endurance, and ruck improvement.

12:04 But that only accounted for about 29 % of the variation in scores, so it mattered, but it wasn't the whole story. One of the more practically useful things they did was break the men into high and low performer groups based on where they started, so the initial assessment. What they found is that where you start matters a lot for what you should focus on. This seems to be probably the biggest, this is the biggest factor that stood out to me when I first read this about a year or so ago when I got into rucking. or started seriously rucking, but for guys who started with lower strength levels, so maybe people that started rucking coming in cold, this is their entry back into getting into some sort of shape or physical fitness. In this case, a bench press under about 185 pounds, so improving upper body strength and core strength, correlate more with ruck improvement. For guys who were already strong, I guess, already in shape, have been rocking for a while, or have been doing some other sort of physical fitness, and they were measuring them, there was no single factor that had a strong effect. Their improvements were a lot more distributed. This led MCI to put forward what I think is one of the more compelling ideas in the whole series. Again, the concept of base strength requirement. The idea is that there may be a minimum level of strength you

13:34 need to have before your aerobic capacity can fully express itself in a ruck. Below that floor, strength gains move the needle. Above it, other factors, including aerobic training, become more important. Again, MTI is upfront about this. It's a hypothesis, not a confirmed threshold. They didn't have strong enough athletes in their subject pool to define where that ceiling is. The 185 pound number is specific to their subjects and not necessarily generalized for everyone. But as a framework for thinking about your training, you know, where you are right now or what you should be focusing on, I think it's genuinely useful. If you feel like you have entered rucking with relatively low strength, maybe focus on getting your strength up in your upper body before moving on to improving your robot capacity that wraps up the the rucking series that mti did a few years back before wrapping up today i did want to touch on one more thing or one more study that i thought was interesting for this last segment because this one isn't about what training program to run it's it's about what what's actually happening to your body during a ruck as fatigue starts to set in. And I think it adds a really useful layer to everything that we've talked about. And I've mentioned this in the past, but I haven't specifically called out MTI's study on this subject. But this study looked at 70

15:06 male infantrymen from the 82nd Airborne Division. There were guys who completed a 7 -plus mile ruck march in full combat gear. Average load of about 86 .9 pounds at the end of a 72 -hour field training exercise. So these guys weren't fresh. They were already pretty depleted. MTI outfitted each soldier with wearable motion sensors, one on the chest and one on each boot. They collected 3D movement data throughout the entire march. They divided the march into four equal segments to track how movement changed from start to finish. Awesome use of technology. Really cool, really interesting methodology here. What they found was a clear picture of how fatigue changes the way that you move under a ruck. So stride length got shorter as the march went on. Stride width got wider. Step -to -step consistency, so how similar each stride is to the last, decreased.

16:04 And torso sway increased both front to back and side to side. So let's think about what each of those things mean. Shorter stride length means more steps to cover the same distance, more repetitive stress on the same tissues. And over a long ruck, that increases your injury risk in a pretty meaningful way. Moving on to wider stride width. That's typically a sign that your body is searching for a balance under load. Your base of support widens to help keep you upright when your stability is compromised. The next one, more variability. With more variability in your steps, that means your movement is becoming less controlled and consistent. And lastly, the torso sway finding, which is really interesting. Average torso lean didn't change much. Your body is still pointing in roughly the same direction. Obviously, you're going in one direction when you're rocking, but the variability of the lean increased, which means your trunk is working harder to maintain roughly the same position and doing it with less precision as fatigue accumulates. So the movement.

17:16 breakdown that fatigue causes you know shorter steps wider stance less trunk control is consistent with what you'd expect to see from a body that's struggling to manage load and that raises a reasonable question what kind of training builds resilience against those changes so what can you do to to to minimize the sway in your torso and the shorter steps the wider stance to decrease your chances of injury and staying consistent with your rucking Well, building core and upper body stability seems like a sensible answer based on the mechanics. Practicing movement under fatigue, not constantly but deliberately, is another. Progressively longer rucks and loaded carries over time likely help your body learn to maintain mechanics further into a march. The study also validated that wearable sensors can track these changes in real time during actual field conditions, which is pretty exciting. development. Again, sucker for technology and research, but we're probably not far away from those tools that give individual athletes real -time feedback on how their stride and posture are holding up as they fatigue. That's a frontier worth watching, I think. Okay, so let's bring this all together, because I don't want to walk away with a pile of findings and no way for you to take action with all this clutter. Here's how I'd summarize the practical direction from the MTI ruck deep dive series with appropriate caveats where they belong. Number one, rucking performance is multifactorial. I think it's factorial.

18:49 You know what? Let me Google this real quick. I remember using this word a lot in grad school, and I can't remember if it's multifactorial. It is. It's multifactorial. Cool. I'll forget that tomorrow. Where was I? Oh, yeah. So, rucking performance is multifactorial, and that's actually good news. Aerobic fitness, strength, muscular endurance, they all showed up across these studies as being relevant. You know, no single thing owns your ruck performance, which means you have multiple levers to pull, and training any of them well is going to move you forward. So, focus on any of them. They're likely going to help you out. Two, strength, especially upper body strength. It appears to be relevant, though the evidence is still building. This showed up in the pilot study and again in study two, particularly for lower strength athletes, like I mentioned before. MTI's working theory is that you need a minimum level of strength to fully realize your aerobic potential under load. The exact threshold isn't really well defined, but in their study, they used under 185 pounds. That's a reasonable sign that strength work deserves more of your training time than it might be getting. Number three, for men starting from a lower strength base, prioritize strength and upper body muscular endurance. The data from study two pointed clearly in this direction for guys who began with lower strength levels. Once you've built that base, aerobic training likely becomes the more impactful

20:19 lever. It's not one or the other. It's sort of sequential. And then number four, for women, strength, core, and aerobic fitness all seem to matter, with lower body strength appearing as a useful... starting point and lastly talking about fatigue fatigue changes how you move under load in consistent measurable ways they've demonstrated that they've proven that with with their their their last study i talked about so building resilience against those changes through strength work progressive load exposure and sometimes training when you're already a little tired As I mentioned before, I'm looking forward to getting Rob on the show and going a little bit deeper on some of these as well as some of the other studies out of MTI.

21:02 There are threads in this research. I'd love to... pull on them with him directly. I'll make sure to let you know when that conversation is scheduled. In the meantime, I hope this gave you something useful to think about, at least, or maybe something to adjust in your training. Whether you're a competitive rucker, a military athlete, or just someone who wants to get better at moving under load, the research is worth understanding, for sure. All right. Well, that wraps up today's episode. If you're interested in any of these studies, I'll link them in the show notes. I'll also link where you can check out MTI's website. They have several plans that you can explore.

21:43 They offer them to the public if you're interested in improving your wrecking or other outdoor sports. They have several plans available. Go check them out. If you want to reach out to me, head on over to theruckersedge .com or on Instagram at theruckersedgepod. And if you enjoyed today's episode, make sure to follow or subscribe to the show in your favorite podcast app so you're notified of new episodes. I have a really cool episode coming up next. I had the absolute pleasure of speaking with Terrence Ogden. You may remember if you listened to an episode back in the fall where I did sort of like an update or rucking in the news sort of. episode he is the gentleman that rucked across the state of texas east to west and um really cool insight in that conversation and uh really amazing story his arc from from his past to where he is now definitely worth listen but um again that's it for today thanks for listening to this episode of the ruckers edge and i'll catch you in the next one