Balancing Cardio and Strength Training. What the Science Says About Improving Ruck Training Performance
- Alastair Hunt
- 19 hours ago
- 4 min read
If you've ever attempted a long hike or a rucking event carrying a heavy pack, you'll know that fitness matters enormously. But which kind of fitness? Is it better to run more, lift more, or simply practise carrying the pack itself?
A systematic review by researchers at the U.S. Army Research Institute of Environmental Medicine set out to answer exactly that, combing through a decade of military load carriage research to identify the training approaches that actually move the needle.
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 all studies / resources at bottom of page.
What the Review Did
The researchers searched multiple scientific databases and identified ten original studies that measured how physical training affected load carriage performance, defined as the time taken to complete a set distance while carrying a loaded backpack. They used a statistical technique called meta-analysis to combine results across studies and calculate overall effect sizes, giving a cleaner picture of what works than any single study could provide.
What They Found
The headline finding is clear: combining resistance training with aerobic training works significantly better than either approach alone. When that combined programme was conducted at least three times per week over at least four weeks, the improvements were large by conventional statistical standards. But the most striking result came when load carriage itself was built into training:
Adding progressive rucking or loaded marching to a resistance-aerobic programme produced improvements more than twice as large as resistance-aerobic training alone.
The principle at work here is specificity: the body adapts most effectively to the precise demands placed on it. Carrying a loaded pack recruits specific muscles, energy systems, and movement patterns that general fitness training only partially develops. Practising the task itself closes that gap.
One particularly interesting finding concerned upper body training. Upper body resistance work combined with aerobic training proved nearly as effective as full body resistance training. This makes physiological sense: in backpack-based load carriage, most of the weight is borne by the shoulders and upper torso, with hip belts only offloading around 30% of the burden. Strengthening the muscles that stabilise and support the pack appears to be disproportionately valuable.
Aerobic training alone produced inconsistent results across studies, sometimes showing meaningful gains and sometimes very little. Resistance training alone showed a similar pattern. Neither, on its own, appears reliably sufficient.
Periodised resistance training, where volume and intensity are varied systematically over time, also appeared to outperform simple linear programmes where the same number of sets and reps are used throughout.
The review does acknowledge important limitations. Studies varied considerably in participant type, load weights, distances, and training duration, which complicates direct comparison. Most criterion tests also covered relatively short distances of 3.2 km or less, leaving open questions about longer efforts.
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.
What This Means for Us
If you are training for a rucking event or simply want to carry a heavy pack further and faster with less fatigue, the evidence points toward a clear strategy.
Do not rely on running or lifting alone. Combine both, prioritise upper body strength work alongside your cardio, and, critically, include regular progressive loaded carries in your programme.
Start with lighter loads over shorter distances and build systematically over weeks.
That last element, practising the thing you want to get better at, may be the single most important thing you can do.
Wherever you are: train safe and enjoy the process!
Alastair
Related resources & research
The study in question...
Knapik JJ, Harman EA, Steelman RA, Graham BS. A systematic review of the effects of physical training on load carriage performance. J Strength Cond Res. 2012 Feb;26(2):585-97. doi: 10.1519/JSC.0b013e3182429853. PMID: 22130400.
Other
Oeschger R, Roos L, Wyss T, Buller MJ, Veenstra BJ, Gilgen-Ammann R. Influence of Soldiers' Cardiorespiratory Fitness on Physiological Responses and Dropouts During a Loaded Long-distance March. Mil Med. 2022 Jan 7;188(7-8):e1903–9. doi: 10.1093/milmed/usab540. Epub ahead of print. PMID: 35015894; PMCID: PMC10363014.
Orr R, Pope R, Lopes TJA, Leyk D, Blacker S, Bustillo-Aguirre BS, Knapik JJ. Soldier Load Carriage, Injuries, Rehabilitation and Physical Conditioning: An International Approach. Int J Environ Res Public Health. 2021 Apr 11;18(8):4010. doi: 10.3390/ijerph18084010. PMID: 33920426; PMCID: PMC8069713.
Godhe M, Helge T, Mattsson CM, Ekblom Ö, Ekblom B. Physiological Factors of Importance for Load Carriage in Experienced and Inexperienced Men and Women. Mil Med. 2020 Aug 14;185(7-8):e1168-e1174. doi: 10.1093/milmed/usaa050. PMID: 32248224.
Hunt AP, Billing DC, Patterson MJ, Caldwell JN. Heat strain during military training activities: The dilemma of balancing force protection and operational capability. Temperature (Austin). 2016 Feb 26;3(2):307-317. doi: 10.1080/23328940.2016.1156801. PMID: 27857960; PMCID: PMC4965006.
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