Should You Train Cardio or Strength First? Optimal Workout Order for AFT Success

You wake up at 0500, head to the gym, and face the same question every Soldier preparing for the AFT eventually asks: should I run first or lift first? Maybe you've heard lifting before cardio burns more fat. Or that running first warms you up better for squats. The truth is more nuanced—and for AFT preparation specifically, the answer depends on which events you need to improve most.

The AFT demands both strength and endurance, often within minutes of each other. Your 3-Rep Max Deadlift requires raw power, while your 2-Mile Run demands aerobic capacity. Training for both simultaneously is called concurrent training, and research shows the order you train these qualities significantly impacts your results.

The Interference Effect Explained

In 1980, researcher Robert Hickson published a landmark study showing that training strength and endurance together produced smaller strength gains than strength training alone. This phenomenon became known as the "interference effect," and it's been the subject of intense scientific scrutiny ever since.

Here's what's happening at the cellular level: endurance training activates AMPK, a protein that promotes mitochondrial development and fat oxidation. Strength training activates mTOR, which drives muscle protein synthesis and hypertrophy. These two pathways partially inhibit each other. When you train both in close succession, your body receives competing signals about how to adapt.

A 2023 systematic review and meta-analysis published in Sports Medicine examined 59 studies with over 1,300 participants and confirmed this effect is real and measurable. The researchers found that concurrent training produces a statistically significant interference effect for lower-body strength adaptations in males—exactly the kind of strength you need for the MDL. The effect size was small but meaningful: a standardized mean difference of -0.43 compared to strength training alone.

Interestingly, the same review found no significant interference effect in females. The researchers suggested hormonal differences may play a protective role, though more research is needed to understand why.

A Journal of Physiology review on concurrent training dug deeper into the mechanisms. The authors concluded that despite the potential for several key regulators of muscle metabolism to explain the incompatibility between endurance and resistance exercise, it now seems likely that multiple integrated processes—rather than a single pathway—generate the interference effect. In other words, it's complicated, but it's real.

The interference effect isn't a death sentence for your gains. But it does mean you need to be strategic about how you structure your training.

What Research Says About Exercise Order

If you're going to train both cardio and strength in the same session, does the order matter? A 2017 meta-analysis in the Journal of Sports Sciences pooled the available evidence and found a clear answer—but only for one outcome.

The researchers analyzed studies comparing strength-then-endurance versus endurance-then-strength training sequences. Their key findings:

For lower-body strength: Training order made a significant difference. Performing strength training before endurance training resulted in greater lower-body 1RM gains, with a pooled mean difference of 3.96 kg (95% CI: 0.81 to 7.10 kg). That's roughly an 8-10 lb advantage for strength-first training.

For aerobic capacity: Training order had no impact. The pooled mean difference for VO2max was just 0.39 ml/kg/min—statistically and practically insignificant. Whether subjects ran before or after lifting, their aerobic capacity improved similarly.

This finding has direct implications for AFT preparation. If your MDL is your weakest event, you should prioritize strength training by doing it first in your sessions—the research suggests you'll gain more strength that way. But if your 2MR is holding back your score, you have more flexibility. Training cardio first won't compromise your running gains, and it might actually improve your running performance in that session since you won't be fatigued from lifting.

If Your Weakest Event Is the 2-Mile Run: Cardio First

Open the AFT Calculator and input your current scores. If your 2MR is dragging down your overall score more than any other event, your training structure should reflect that priority.

A 2019 review in Sports Medicine examined how resistance training affects subsequent endurance performance. The authors found that resistance training-induced muscle damage can impair endurance performance for 24-48 hours after heavy lifting. The magnitude of impairment depends on several factors: exercise intensity, exercise mode, the specific muscles trained, and individual recovery capacity.

The practical implication: if running performance is your primary concern, performing your key running sessions in a fresh state—before lifting or on separate days from heavy lower-body work—ensures you can hit the paces and volumes needed to improve. When you run after heavy squats or deadlifts, your running performance in that session suffers. That might be an acceptable trade-off if strength is your priority, but not if you're trying to drop significant time off your 2MR.

The research also suggests that the type of strength training matters. Heavy compound movements that induce significant muscle damage impair subsequent running more than lighter, less damaging work. If you must combine training in the same session with a cardio-first priority, the strength work that follows should account for this.

If Your Weakest Event Is the Deadlift: Strength First

When the AFT Calculator reveals that your MDL is your biggest weakness, the research clearly supports prioritizing strength training.

The 2017 meta-analysis finding bears repeating: strength-first training order produced significantly greater lower-body strength gains than endurance-first order. For a Soldier who needs to add 20+ pounds to their deadlift, this difference matters.

But exercise order within a session is only part of the equation. The 2023 meta-analysis on concurrent training found that the interference effect on lower-body strength was consistent regardless of training status—both untrained and trained individuals experienced blunted strength gains when combining strength and endurance training. However, the same study found that for aerobic capacity, untrained individuals showed impaired VO2max improvements with concurrent training, while trained and highly trained endurance athletes did not.

What does this mean practically? If you're already a decent runner but need to bring up your deadlift, you can likely maintain your aerobic capacity with less running volume while focusing on strength. Your aerobic base won't disappear as quickly as you might fear, especially if you keep some running in your program. But if you're weak and have poor cardio, you're fighting interference on both fronts—a situation that requires careful programming and realistic expectations about the rate of improvement.

A 2022 meta-analysis on concurrent training in team sport athletes found that well-designed concurrent programs did not produce significant interference on strength or power development. The key phrase is "well-designed"—the researchers noted that appropriate recovery between sessions and intelligent exercise selection can minimize or eliminate the interference effect.

Concurrent Training Strategies for Balanced AFT Prep

What if your AFT Calculator shows relatively balanced weaknesses across events? Or what if you need to improve both the deadlift and 2MR substantially? The research points to several strategies that can help.

Separation between sessions matters. The interference effect appears strongest when strength and endurance training occur in close proximity. While no study has identified a precise "safe" window, the 2019 Sports Medicine review suggests that residual fatigue and muscle damage from resistance training can impair endurance performance for up to 48 hours. Separating your highest-quality sessions—whether by training at different times of day or on different days entirely—may reduce interference.

Intensity distribution matters. Not all endurance training creates equal interference. High-intensity interval training appears to interfere more with strength adaptations than low-intensity steady-state work, likely due to greater metabolic stress and competing recovery demands. A 2023 systematic review on concurrent training in females noted that the type and intensity of endurance training likely influences the magnitude of any interference effect.

Training status matters. The 2023 meta-analysis found that training status influenced outcomes for aerobic capacity but not for strength. Untrained individuals showed blunted VO2max gains with concurrent training, while trained endurance athletes did not. This suggests that if you're new to running, you may need to be more aggressive with your aerobic training volume to see improvements, even at the cost of some strength development.

Recovery capacity is individual. Some Soldiers can handle high training volumes across both modalities; others cannot. The research provides averages and trends, but your response to concurrent training will depend on factors like sleep, nutrition, stress, age, and genetics. Monitoring your performance in both domains over time is the only way to know how you personally respond.

How to Periodize for AFT Test Date

The research on periodization for concurrent training is less robust than the research on acute training order, but some principles emerge from the available evidence.

An umbrella review on resistance training variables found that training frequency, volume, and load all influence strength adaptations—and that these variables can be manipulated over time to optimize results. The same logic applies to concurrent training: your approach should change as your test date approaches.

During base-building phases (far from your test date), higher training volumes in both strength and endurance can be tolerated. This is when you build the raw capacities—aerobic base, muscular strength, work capacity—that you'll sharpen later. Interference may blunt the rate of adaptation, but the overall stimulus drives improvement.

During intensification phases (closer to your test date), volume typically decreases while intensity increases. This is particularly important for the interference effect: high-intensity work in both domains creates greater recovery demands. Reducing volume while maintaining or increasing intensity allows you to peak specific qualities without accumulating excessive fatigue.

During taper phases (the final weeks before testing), volume drops significantly while intensity is maintained. The research on tapering for concurrent athletes is limited, but general tapering principles suggest reducing training volume by 40-60% while keeping some high-intensity work to maintain fitness. The goal is to arrive at test day fresh, not to make further gains.

Use the AFT Calculator to identify which events need the most work, then structure your training phases to prioritize those qualities when it matters most.

Putting It All Together

The cardio-versus-strength debate has no universal answer. What matters is understanding the research and applying it to your specific situation.

The key takeaways from the research:

The interference effect is real: concurrent training produces smaller strength gains than strength training alone, particularly for lower-body strength in males. Training order matters for strength but not for aerobic capacity: if the MDL is your priority, train strength first. Recovery between sessions influences interference: separating your hardest sessions reduces competing demands. Individual factors matter: your training status, recovery capacity, and specific weaknesses all influence the optimal approach.

Start by using the AFT Calculator to identify which events are limiting your score. If your MDL is your biggest weakness, the research supports prioritizing strength training in both exercise order and overall programming emphasis. If your 2MR is the limiter, you have more flexibility in training order—but ensuring your key running sessions are performed fresh will help you hit the paces needed to improve.

The AFT rewards Soldiers who train intelligently, not just those who train hard. Understanding what the research says about concurrent training—and what it doesn't say—can help you make better decisions about how to structure your preparation.