In this article
Many people want to be strong and fit: to lift well and also run, cycle or play sport. For years, gyms repeated a warning that cardio “kills your gains”. The real picture is more encouraging, and it comes with one useful exception.
Key facts
- 1980: the year a famous study first showed that heavy endurance training could slow strength gains. This is called the interference effect.
- 43 trials: a 2022 review of the research found that combining the two does not reduce gains in muscle size or maximum strength.
- The exception: explosive power, such as jumping and sprinting, improved less, especially when both were done in the same session.
- Cycling interferes less than running, according to a 2012 review.
Where the worry came from
In 1980, researcher Robert Hickson compared three groups over ten weeks. One lifted weights, one did endurance training, and one did both. The endurance gains were the same whether or not people also lifted. But the group doing both stopped gaining strength after about seven weeks, while the lifting-only group kept improving. That finding gave the “interference effect” its name.
It is worth knowing how hard that study was. The combined group trained for both, every day, about six days a week, roughly 70 to 80 minutes a day. Few people train like that.
What later research found
A 2012 review of 21 studies found that interference was linked to how much endurance training people did and what kind. Running hurt strength and muscle gains more than cycling, probably because running adds more pounding and muscle damage to the legs.
The biggest review so far, published in 2022, pooled 43 trials with more than 1,000 people. It found that doing both did not reduce gains in muscle size or maximum strength, whatever the type of cardio, the age of the people or how often they trained. The one clear cost was explosive strength, the ability to produce force fast, as in jumping or sprinting. That cost was biggest when cardio and lifting were done in the same session.
| Goal | Does adding cardio hurt it? | What helps |
|---|---|---|
| Bigger muscles | Generally no | Enough protein and total training volume |
| Maximum strength | Generally no | Keep lifting heavy at least twice a week |
| Explosive power (jumps, sprints) | Somewhat, especially in the same session | Separate cardio and power work by several hours or a day |
| Endurance (aerobic fitness) | No; lifting does not hurt it | Lifting may even help running economy |
A simple weekly plan
This sample week suits a healthy adult with some training experience. It keeps the hardest leg work away from hard running, and puts power work when the legs are fresh.
| Day | Session | Notes |
|---|---|---|
| Monday | Strength: full body, heavy | 3 to 5 sets of 3 to 6 reps on main lifts |
| Tuesday | Easy cardio, 30 to 45 minutes | Cycling or jogging at a pace where you can talk |
| Wednesday | Speed and power, then upper-body strength | Short sprints or jumps first, while fresh |
| Thursday | Rest or a walk | Recovery day |
| Friday | Strength: full body, moderate | Slightly lighter, more reps |
| Saturday | Longer endurance session | 45 to 90 minutes at an easy pace |
| Sunday | Rest | Sleep well and eat enough |
Five rules that reduce interference
- Separate them when you can. If both are on the same day, leave several hours between them, or do the one that matters most first.
- Keep most cardio easy. Most endurance work should be at a comfortable, talking pace.
- Prefer cycling or swimming if leg strength is your main goal.
- Do power work fresh. Sprints and jumps go at the start of a session, never after a long run.
- Eat and sleep enough. Training for two goals needs more fuel and recovery.
For more on recovery, read our guide to how long to rest between workouts and what sleep does for the body.
Health note: This article is general information, not medical advice. If you are new to exercise or have a health condition, check with a doctor and build up gradually.
Frequently asked questions
Will running make me lose muscle?
Not if you keep strength training and eat enough protein and calories. Large amounts of running with too little food can slow muscle gain.
Should I do cardio before or after weights?
Do first whatever matters most to you that day. If strength or power is the priority, lift first or on a different day.
How long should I wait between cardio and weights on the same day?
There is no single rule, but several hours apart tends to work better than back-to-back, especially for power training.
Browse more guides in the Fitness section.
