Two camps have dominated fitness thinking for decades.
The strength camp says: lift heavy, get strong, running is cardio and cardio kills gains. The endurance camp says: log the miles, build the base, heavy lifting will bulk you up and slow you down.
Both camps are wrong — or more precisely, both are right in specific contexts and wrong when applied universally to athletes who need to perform across multiple physical demands simultaneously.
Military athletes do not get to specialize. You need to be strong enough to carry a teammate and fast enough to chase one. You need the endurance to operate for hours and the power to explode when it counts. The question is not whether to train both — it is how to train both without one undermining the other.
The answer, based on the research and years of practical application, is that it is absolutely possible. It just requires smart programming.
What the Research Actually Shows
The conventional fear — that endurance training will kill your strength gains — comes from a real phenomenon called the interference effect. And the research does show it exists. A 2012 meta-analysis on concurrent training found studies demonstrating that combining aerobic and resistance training led to decreases in strength, hypertrophy, and power compared to resistance training alone.
But here is what that same analysis also found: a substantial number of other studies showed no decrements in strength when endurance training was added.
So which is it?
The answer is in the programming. A 2006 study by Nader found that concurrent training only compromised strength when the training engaged the same muscle groups at the same time. When the programming was designed to be synergistic rather than antagonistic — when the two types of training were structured to complement rather than compete — there was no interference effect.
The problem is not concurrent training. The problem is poorly designed concurrent training.
What “Poorly Designed” Looks Like
The most common version of the interference problem: someone tries to get stronger and improve their run time simultaneously by doing long slow distance runs and heavy lifting in the same sessions or back-to-back days, with the same muscle groups taxed in both.
Long slow distance running causes significant mechanical stress on the legs, elevates cortisol, breaks down muscle protein, and extends recovery time. Doing this regularly while also trying to drive strength adaptations in the same muscle groups creates a recovery deficit that neither adaptation can overcome efficiently.
The result: mediocre strength gains, mediocre run improvement, and a level of fatigue that makes both feel harder than they should.
What Smart Concurrent Programming Looks Like
The goal is training that improves both qualities without one undermining the other. Here is the framework that works:
Strength work: maximize strength without maximizing mass. The military athlete does not need to be a powerlifter. A 300-pound squat on a 180-pound frame is not an asset in the field — it is a liability if someone has to drag you to safety. Train for strength through heavy low-rep work (3–5 sets of 1–5 reps) to drive neuromuscular adaptation and force production without triggering significant hypertrophy. Think gymnast, not powerlifter. As covered in how to get strong, the strength gains from this approach come primarily from improved motor unit recruitment and coordination — not from adding mass.
Conditioning: intervals, not long slow distance. Two to three high-intensity interval sessions per week — short intervals one day, longer intervals another — improve your maximal aerobic power without the downsides of long slow distance training. Less muscle protein breakdown. Less cortisol. Less accumulated fatigue. Better carry-over to the events that actually matter. The endurance mini-course covers this approach in detail — the same method that took a 21:37 3-mile down to 17:55 while maintaining strength across all the major lifts.
The key structural principle: keep high-intensity strength and high-intensity conditioning on separate days where possible. When they must share a session, strength before conditioning — never the reverse. Fatiguing your legs with intervals before a squat session is a reliable way to produce both a bad strength session and a bad conditioning session.
This combination provides sufficient recovery between the demands of each type of training, which is what allows both adaptations to occur simultaneously rather than competing with each other.
The Proof of Concept
This is not theoretical. Running this exact approach — heavy strength work three to four days per week combined with two interval sessions — produced a sub-18 3-mile alongside a 2.5x bodyweight deadlift, a 2x bodyweight squat, and 26–28 strict pull-ups. No sacrifice of strength for speed. No sacrifice of speed for strength.
The research conclusion from that 2012 meta-analysis puts it directly: “Interference effects of endurance training are a factor of the modality, frequency, and duration of the endurance training.”
Translation: it is not concurrent training that causes the interference. It is how you program it.
If you want the full system for building run capacity without losing strength — the interval structure, the mechanics, and sample workouts — the Free 5-Part Endurance Mini-Course is the starting point.
The Deeper Reading
This post covers the question of whether you can be strong and fast simultaneously. The next logical questions are how to program the strength side to maximize force production without adding bulk — which is covered in get strong and moving faster — and how the explosive/dynamic effort component fits into a weekly training structure, which is in strength speed training with EMOMs.
All three posts form a complete picture of concurrent training done right. If you want it laid out as a complete program without having to piece it together yourself, the Strategic S&C 12-Month Program is 52 weeks of exactly this — strength, work capacity, endurance, durability, and mobility structured to work together rather than against each other.