The Interference Effect: Can You Run and Lift Without Losing Gains?

Yes, you can run and lift at the same time and improve at both. The "interference effect" is real, but for most recreational and club athletes it is small, and it is mostly a scheduling problem rather than a reason to avoid either type of training.

Concurrent training simply means doing endurance and strength training in the same programme. The interference effect describes the finding that, in some situations, adding endurance work can blunt gains in strength, power and muscle size compared with lifting alone.

The concept dates back to a 1980 study by Robert Hickson, in which participants who combined heavy lifting with high-volume endurance training saw their strength gains stall after several weeks, while the strength-only group kept improving.

Since then, meta-analyses (including work by Wilson and colleagues in 2012 and Schumann and colleagues in 2022) have refined the picture:

• Endurance capacity (VO2max, running performance) is generally not harmed by adding strength training
• Maximal strength is usually only slightly affected, if at all
• Explosive power and muscle growth are the qualities most likely to be blunted
• Running appears to interfere more than cycling, likely because of the extra muscle damage from impact

In other words: the runner who adds lifting rarely loses running fitness. It is the lifter who adds a lot of running who has more to protect.

There are two main explanations, and they probably both play a part.

• Fatigue: a hard run leaves your legs tired, so the next strength session is lower quality. Lower quality lifting means a weaker stimulus.
• Competing signals: endurance work and strength work trigger different molecular pathways in muscle. In theory, heavy endurance training can dampen some of the signalling that drives muscle growth, although in practice the effect seems smaller than early lab studies suggested.

The practical takeaway is that fatigue and recovery are the things you can control, and they matter most.

These are the rules we use when we build programmes for runners, triathletes and Hyrox athletes:

• Separate hard sessions: leave 6 or more hours between a hard run and a heavy lift, ideally 24 hours
• Same-day option: if both happen on one day, put the most important session first. For runners, that's usually the run
• Hard days hard, easy days easy: stack your heavy lifting on the same day as intervals, so your easy days stay genuinely easy
• Keep strength volume low and intensity high: 2 to 4 hard sets of 3 to 6 reps on key lifts gives a large benefit for little fatigue
• Don't lift heavy legs the day before a long run or key workout
• Eat enough: under-fuelling makes interference much worse, especially carbohydrate around hard sessions
• Periodise: lift more in the off-season, then drop to a maintenance dose of 1 to 2 sessions a week in a race block

For a runner doing 4 runs a week:

• Monday: easy run
• Tuesday: intervals in the morning, heavy lower-body strength in the evening
• Wednesday: rest or mobility
• Thursday: tempo run
• Friday: lighter full-body strength and plyometrics
• Saturday: rest
• Sunday: long run

This keeps the hardest days together, protects the long run and still gives two good strength sessions a week.