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Concurrent Training: Can You Build Muscle and Run Fast?

🕐 7 min read📅 February 2026

The "interference effect" — the idea that endurance training blunts strength and muscle gains — has worried athletes for decades. The research shows it's real, but far more manageable than most people think.

The Original Discovery

Robert Hickson (1980), in a landmark study published in the European Journal of Applied Physiology, was the first to document that combining heavy strength training with high-volume endurance training compromised strength gains compared to strength training alone. This study launched decades of "cardio kills gains" anxiety.

However, Hickson's protocol was extreme: subjects performed both heavy squats and 40 minutes of intense running or cycling 6 days per week. This is far beyond what most people actually do.

Modern Understanding

Wilson et al. (2012), in a comprehensive meta-analysis of 21 studies published in the Journal of Strength and Conditioning Research, quantified the interference effect more precisely:

  • Hypertrophy: Concurrent training reduced muscle growth by a small but significant amount — approximately 10-15% less than strength training alone.
  • Maximal strength: Moderately affected, with about 8-12% less improvement.
  • Power and explosive performance: Most affected, with reductions of 15-20%.
  • Running was more interfering than cycling: The eccentric muscle damage from running created more interference than cycling, which is more concentric in nature.

Minimizing Interference

Baar (2014), in a review published in Sports Medicine, identified the molecular mechanisms behind interference: endurance training activates the AMPK pathway (catabolic), which can suppress the mTOR pathway (anabolic) activated by strength training. Based on this, he proposed practical solutions:

  • Separate sessions by 6+ hours: This allows the molecular signals from each session to peak without directly competing. Morning strength, evening cardio (or vice versa).
  • If you must combine: Do strength first, endurance second. Strength training when fresh produces better neuromuscular adaptations.
  • Fuel adequately: Interference is amplified in a caloric deficit. Eating enough — particularly protein (1.6-2.2g/kg) and carbohydrates — mitigates much of the interference.
  • Limit running volume: If muscle/strength is the priority, keep running to 2-3 sessions per week of 20-40 minutes. Or substitute cycling, which causes less interference.

Practical Programming

For an athlete wanting both strength and endurance:

  • Monday AM: Lower body strength / PM: Easy 30min run or rest
  • Tuesday: 45-60min endurance session (moderate intensity)
  • Wednesday AM: Upper body strength / PM: Easy 30min run or rest
  • Thursday: Rest or active recovery
  • Friday AM: Full body strength / PM: Interval session
  • Saturday: Long easy endurance session
  • Sunday: Rest

The key: prioritize whichever modality matters more to your goals earlier in the day and earlier in the week, when you're freshest.

Key Takeaway

You can absolutely build muscle and improve endurance simultaneously. The interference effect is real but modest (10-15% reduction). Separating sessions by 6+ hours, doing strength first, fueling adequately, and favoring cycling over running for cardio minimizes interference to a practically negligible level for most athletes.

References

  • Hickson, R.C. (1980). Interference of strength development by simultaneously training for strength and endurance. European Journal of Applied Physiology, 45(2-3), 255-263.
  • Wilson, J.M. et al. (2012). Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises. Journal of Strength and Conditioning Research, 26(8), 2293-2307.
  • Baar, K. (2014). Using molecular biology to maximize concurrent training. Sports Medicine, 44(Suppl 2), 117-125.
  • Murach, K.A. & Bagley, J.R. (2016). Skeletal muscle hypertrophy with concurrent exercise training. Sports Medicine, 46(8), 1029-1039.
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