Sex Differences in Load Carriage for Female Ruckers: Mostly Body Size, Not Biological Disadvantage
- Alastair Hunt
- 1 day ago
- 5 min read
A systematic review published in Applied Ergonomics pulled together 33 studies and over 1,240 participants to answer a question with real practical weight for rucking, hiking, and military communities:
Do men and women respond differently to carrying a loaded pack, physiologically and biomechanically, or do the well documented sex differences in injury rates and performance actually come down to something else?
The researchers systematically searched five major databases, screened over 4,600 records, and qualitatively synthesised findings on oxygen consumption, heart rate, joint mechanics, and gait patterns during loaded walking.
As ever, please talk to your doctor or medical practitioner most familiar with your medical history before implementing any changes in diet, exercise or lifestyle, especially if you are under treatment. Links to studies at bottom of page.
What They Found
The headline finding is refreshingly clear: when oxygen consumption was expressed relative to body mass rather than as an absolute number, most sex differences disappeared. Men typically had higher absolute oxygen uptake, but that's largely because men in these studies were, on average, heavier and taller. Once you account for body size, the physiological cost of carrying a given relative load was broadly similar between sexes.
That said, a few real differences did emerge. When men and women carried the same absolute weight (rather than a load scaled to their body mass), women worked at a higher percentage of their own aerobic capacity and tended to hit exhaustion earlier during maximal tests. This makes intuitive sense: if a 20 kg pack represents a much larger share of a smaller person's capacity, it will be proportionally harder for them, regardless of sex. Heart rate also tended to run higher in women under fixed absolute loads, though this wasn't a fully consistent finding across all studies.
On the biomechanical side, the review found little evidence of sex differences in the most commonly studied movement patterns, forward-and-back joint angles, ground reaction forces normalised to body weight, and stride length or rate. Where differences did appear, they were subtler: some evidence pointed to greater hip adduction and rotation in women, particularly over longer marches, along with a possible economic advantage from wider, more mobile pelvises.
A couple of studies also suggested women may develop smaller knee range of motion under heavy absolute loads, though this could relate more to differences in muscle mass than sex itself.
What This Means for Us
The practical takeaway here is genuinely important for anyone coaching mixed-sex rucking groups or designing training programmes: the common practice of issuing identical absolute pack weights to everyone, regardless of body size, likely disadvantages smaller individuals, who are disproportionately though not exclusively women. A 20 kg pack is a very different relative burden for someone weighing 55 kg versus 90 kg. Scaling load to body mass, where the task allows it, appears to be a more physiologically fair approach, and this logic applies just as well to civilian rucking training as it does to military load carriage.
If you are preparing for events where pack weight is fixed and non-negotiable regardless of body size, this review suggests that lighter or smaller ruckers, again not necessarily female, but disproportionately so, may need targeted strength and conditioning work to increase lean body mass and aerobic capacity, since this appears to be the more meaningful lever than sex itself.
It's also worth flagging that the review found surprisingly little research on how men and women's gait and joint mechanics diverge during longer marches or on uneven terrain, both highly relevant to real-world rucking. Most studies were short duration lab-based walks, so how these patterns hold up across a multi-hour event on variable ground remains an open question.
Given that women in military populations have consistently shown higher injury rates during load carriage training, understanding these longer-duration, real-terrain responses is a genuine gap the authors flag for future research.
If you are training for the PARAS'10, a Norwegian Foot March, or just to get fast and fit, our self-paced online course"Built to Ruck The Science and Practice of Rucking" covers everything the research tells us about load carriage training, pacing, progression, heat management, hydration, fueling and more. It is built for ruckers at every level of experience, and draws directly on the peer-reviewed military and sports science research.
Practical Advice for Female Ruckers
Prioritise strength training, especially lower body and hip strength. Since much of the apparent "disadvantage" traces back to a fixed pack weight representing a larger share of aerobic and strength capacity, building lean muscle mass is the most evidence backed lever available, more so than any gait modification.
If your event allows relative loading, use it. For training (not fixed-weight events like the Norwegian Foot March), scaling pack weight to a percentage of body mass rather than copying a training partner's absolute load will give a fairer, more comparable training stimulus.
Pace conservatively relative to your own capacity, not a training partner's. Because a given absolute load sits at a higher percentage of aerobic capacity for smaller frames, matching a heavier partner's pace stride for stride under the same pack weight may mean you're working substantially harder relative to your own ceiling.
Pay attention to hip and knee mechanics on longer sessions. The review flagged increased hip adduction and rotation in women specifically emerging over longer distances (5 km+), which is relevant to injury risk. Hip strengthening work (glute medius, deep hip rotators) and periodic gait awareness checks on long rucks may help manage this.
The review's core message is that most apparent physiological gaps vanish once body size is accounted for. A well conditioned smaller rucker is not inherently disadvantaged, the fixed absolute loads common in some events are what create the disparity.
Wherever you are: train safe and enjoy the process!
Alastair
Key Studies and Resources
Hudson S, Barwood M, Low C, Wills J, Fish M. A systematic review of the physiological and biomechanical differences between males and females in response to load carriage during walking activities. Appl Ergon. 2024 Jan;114:104123. doi: 10.1016/j.apergo.2023.104123. Epub 2023 Aug 23. PMID: 37625283.
Schram B, Rosseau J, Canetti EFD, Orr R. Sex Differences in the Metabolic Cost of a Military Load Carriage Task: A Field Based Study. Sports (Basel). 2025 Dec 9;13(12):442. doi: 10.3390/sports13120442. PMID: 41441426; PMCID: PMC12736546.
Loverro KL, Hasselquist L, Lewis CL. Females and males use different hip and knee mechanics in response to symmetric military-relevant loads. J Biomech. 2019 Oct 11;95:109280. doi: 10.1016/j.jbiomech.2019.07.024. Epub 2019 Jul 31. PMID: 31405526.
Comments