Adding endurance training to a lifting program can limit gains in maximal strength, but it does not appear to block hypertrophy or explosive performance in trained lifters. In an 11-week 2026 study of trained young men, the concurrent group did not improve maximal isometric strength, yet still grew their quads (+8.8% cross-sectional area) and improved jump impulse (+8.8%). The practical takeaway is that if you run, ride, or row alongside lifting, a program built around explosive intent and hypertrophy holds up far better than one chasing a heavier max.
The "interference effect" is one of the most debated topics in strength training. Research consistently suggests that combining endurance and resistance work can blunt some strength adaptations, but the size of that effect depends on who is training, how the sessions are programmed, and which outcome you care about. This study adds a useful layer: it tracked not just whether interference happens, but when it shows up across a training block.
Key Finding
Concurrent training stopped maximal strength from improving and delayed early-phase rate of force development (RFD), but it did not prevent muscle growth or gains in jump performance. Lifting-only participants improved more on most measures, yet the concurrent group still made meaningful hypertrophy and power adaptations.
The authors conclude that concurrent training can work well for trained individuals when the resistance component is periodized toward neural-driven explosive qualities or hypertrophy, rather than pure maximal strength.
Study Details
Researchers from Portugal randomly assigned 30 trained young males to one of three groups for 11 weeks:
- Endurance training only (E)
- Resistance training only (R)
- Concurrent training (CT), combining both
The program ran in two mesocycles:
- Weeks 1-5: emphasis on maximal strength
- Weeks 6-11: emphasis on explosive strength
Testing happened at baseline, mid-training (after the first block), and post-training. Measures included:
- Leg-press maximal voluntary isometric contraction (MVIC)
- Rate of force development, including early-phase RFD (0-50 ms)
- Countermovement jump kinetics (positive impulse)
- Vastus lateralis cross-sectional area (CSA) and pennation angle, measured by imaging
- Quadriceps electromyographic (EMG) activity
The mid-point test is what makes this study interesting. It lets us see that the concurrent group's adaptations were not just smaller, but arrived on a different schedule.
Results
Maximal Strength: The Clearest Interference
Leg-press MVIC improved only in the resistance group, by 18.4 ± 10.2%. Neither the concurrent nor the endurance group showed a significant change. This is the most direct evidence of interference in the study, and it lines up with the broader literature suggesting maximal force production is the quality most sensitive to added endurance work.
Rate of Force Development: Delayed, Not Denied
Peak RFD improved in both the resistance group (31.8 ± 23.2%) and the concurrent group (23.1 ± 27.9%). The timing differed:
- The resistance group improved progressively through both mesocycles.
- The concurrent group improved only during the second, explosive-focused block.
Early-phase RFD (the first 50 ms of a contraction) followed the same pattern. The resistance group improved from mid-training onward, while the concurrent group improved only between mid- and post-training, by 38.3 ± 40.4%. That late improvement came with greater quadriceps EMG activity, pointing to a neural adaptation. The endurance-only group showed no RFD changes.
Jump Performance: No Interference
Countermovement jump positive impulse increased in both the resistance group (12.7 ± 9.0%) and the concurrent group (8.8 ± 8.3%). The authors found no evidence of interference for jump-related explosive performance.
Hypertrophy and Muscle Architecture
Vastus lateralis cross-sectional area increased significantly in both groups:
- Resistance only: +17.0 ± 13.0%
- Concurrent: +8.8 ± 9.4%
Pennation angle, the angle at which muscle fibers attach to the tendon and a common marker of architectural hypertrophy, rose by 18.6 ± 15.1% in the resistance group and 10.1 ± 12.9% in the concurrent group.
The raw averages suggest the lifting-only group grew roughly twice as much. However, the standard deviations are large, and the abstract reports within-group changes rather than a clear between-group difference for hypertrophy. The safest reading: concurrent training still produced real muscle growth, possibly somewhat less of it.
Limitations
This is a well-designed study, but a few constraints are worth keeping in mind:
- Small sample. Thirty participants split across three groups means roughly ten per condition, and the wide standard deviations (some larger than the mean change) reflect high individual variability.
- Narrow population. Results apply to trained young males. Women, older lifters, and highly advanced athletes may respond differently.
- Limited outcome scope. Strength was measured isometrically on a leg press and hypertrophy at a single muscle site. Dynamic 1RM squat or deadlift performance, and upper-body interference, were not assessed.
The abstract also does not specify the endurance modality, intensity, or session sequencing, all of which research consistently suggests influence how much interference occurs.
What This Means for Your Training
The distinctive insight here is not that concurrent training causes interference. It is that interference is selective and time-dependent. Maximal strength took the hit; hypertrophy and explosive power largely survived. That gives lifters a clear framework for programming.
1. Match your goal to the quality that survives interference
If you are running or cycling regularly, a block built around hitting a new heavy single is fighting the most vulnerable adaptation. Blocks focused on hypertrophy (moderate loads, sets taken close to failure) or explosive intent (jumps, speed work, moving submaximal loads fast) are more likely to deliver results alongside endurance work.
2. Save peak strength phases for lower cardio volume
If maximal strength matters to you, consider periodizing your endurance work around it. A practical approach:
- Reduce endurance volume during a 4-6 week strength block.
- Return to higher endurance volume during hypertrophy or power phases.
3. Expect a slower start
The concurrent group's RFD improvements did not appear until the second block, after roughly five weeks. If your numbers look flat early in a concurrent program, that may be the delayed time course this study observed rather than a failed program. Give a block at least 8-12 weeks before judging it.
4. Train with explosive intent on lower-body work
The late RFD gains in the concurrent group coincided with greater quadriceps EMG activity, suggesting improved neural drive. Practically, that means:
- Include 2-3 sets of jumps or explosive lower-body movements once or twice a week.
- On compound lifts, move every rep with maximal intended speed, even at moderate loads.
- Keep explosive sets short (roughly 3-5 reps) so quality stays high.
5. Watch your trends, not single sessions
Because adaptations arrive on different schedules, a single session tells you little. Compare your lower-body numbers across blocks, and note how your endurance volume changed over the same period. This is where consistent logging in an app like Kenso earns its value: you can see whether a strength plateau coincides with a jump in weekly running.
How This Fits Into Your Training Log
Kenso's AI Coach can see your lifting history alongside cardio workouts synced from Apple Health, so it can spot whether leg-press or squat stalls line up with heavier endurance weeks. Ask the Kenso AI coach whether your runs are slowing your squat.
The Bottom Line
This study offers a more nuanced picture than "cardio kills strength." In trained young men, endurance work limited maximal isometric strength and delayed early force production, but muscle growth and jump performance still improved meaningfully. For lifters who also run, ride, or row, the smart move is to program around that reality: emphasize hypertrophy and explosive work during high-endurance periods, and reserve dedicated strength peaks for times when endurance volume is lower.
Concurrent training is not a compromise you have to accept blindly. It is a set of trade-offs you can manage with intention, a clear plan, and data from your own training over time.
Frequently Asked Questions
Does cardio prevent muscle hypertrophy?
Not in this study. The concurrent training group increased quadriceps cross-sectional area by 8.8%, compared to 17.0% in the lifting-only group. Growth may be somewhat reduced, but it was not prevented, and the large variability means individual results differ considerably.
Which strength quality is most affected by concurrent training?
Maximal strength showed the clearest interference. Leg-press maximal isometric strength improved 18.4% in the resistance group but did not change significantly in the concurrent group. Jump performance and peak rate of force development still improved with concurrent training.
How long does it take to see results from concurrent training?
In this study, the concurrent group's rate of force development improved only during the second training block, after about five weeks. Lifters combining endurance and resistance work should evaluate progress over at least 8-12 weeks rather than the first few sessions.
Should I stop running if I want to get stronger?
Not necessarily. A practical option is to reduce endurance volume during focused maximal strength blocks and increase it during hypertrophy or explosive-strength phases, which this study suggests are less affected by interference.
Do these findings apply to women or older lifters?
The study included only trained young males, so results may not transfer directly. Research on concurrent training in women and older adults exists, but this particular study cannot speak to those populations.
Citation
Gomes M, Costa M, Pezarat-Correia P, Mendonca GV. Lower-body strength and hypertrophy adaptations in response to concurrent training in trained young males. Journal of Strength and Conditioning Research. 2026. DOI: 10.1519/JSC.0000000000005698. PubMed: https://pubmed.ncbi.nlm.nih.gov/42949799/