Short answer: you can combine running and strength training in the same week without muscle growth or maximal strength suffering in any meaningful way. In a 2021 meta-analysis, combined training built muscle and maximal strength as well as strength training alone, but explosive strength improved less, especially when both were done in the same session. For runners, the gym improves running economy. What matters is the order: hard runs and heavy leg sessions on different days, and the type of training that matters most for your goal first.
Does running hurt muscle growth?
The worry comes from the so-called interference effect: endurance training might blunt the results of strength training. In a 2012 meta-analysis (Wilson et al., 21 studies), combined training produced slightly smaller gains in muscle size, strength and especially power than strength training alone. The penalty grew with the amount of endurance work, and running appeared to interfere more than cycling.
The newer picture is more reassuring. In the updated meta-analysis by Schumann et al. published in 2021 (43 studies), combined training did not reduce muscle growth or maximal strength compared with strength training alone. The difference showed up in explosive strength, and only when running and lifting were done in the same session. When the sessions were at least three hours apart, no difference was found. Combining hard intervals with strength training also preserved muscle growth, but lower-body strength gains lagged slightly (Sabag et al. 2018).
In practice: if you train for muscle and strength and run 2-3 times a week at moderate distances, running is not a problem. If your goal is jumping, sprinting or explosive lifting, be more deliberate about what you do on the same day.
Why runners need the gym
In the other direction the effect is clearer. In a systematic review by Blagrove et al. (2018), strength training typically improved running economy in middle- and long-distance runners by 2-8%, meaning less energy was used at the same pace. Time trials over 1.5-10 km also improved, and body composition did not change in a way that would hurt running. The review recommends 2-3 strength sessions a week that include both heavy strength work and explosive exercises and plyometrics.
According to a review by Rønnestad and Mujika (2014), heavy strength training improves endurance performance without adding so much muscle mass that it would slow running down. During the competition season, they note, strength levels can be maintained with surprisingly little, for example one session a week.
You'll find a ready plan in the gym program for runners. If you train for Hyrox the same logic applies, and the sport-specific week is in the Hyrox training program.
Which comes first on the same day?
The best solution is to separate running and lifting onto different days or different times of the day. In the Schumann meta-analysis, the drop in explosive strength showed up only when both were done in the same session, not when they were at least three hours apart. That isn't always possible in real life, so here is a simple rule:
- Most important first. If your goal is muscle or strength, lift first and run after. If you are preparing for a race, run first.
- An easy run after the gym barely interferes. Hard intervals right after a heavy leg session are the combination to avoid.
- A short jog before the gym is a warm-up, not a running workout. It needs no special planning.
Keep hard days hard and easy days easy
The structure of the week matters more than the order within one session. Your legs are the shared bottleneck: a heavy squat or deadlift session and a hard interval workout load the same muscles, and if they land on consecutive days, neither goes well.
- No intervals or tempo runs the day after a heavy leg session.
- Put the long run as far from leg day as possible.
- Upper-body training and a hard run fit well on the same day or on consecutive days.
- When you add running, add it gradually. The ten percent rule is not a research-proven limit, but a sudden jump in weekly kilometres is the most common reason the gym starts to feel heavy.
Sample weeks
Three weeks for different goals. Move the rest days to fit your own calendar, as long as hard legs and hard runs don't land back to back.
Sample weeks for combining running and strength training
| Week | Mon | Tue | Wed | Thu | Fri | Sat | Sun |
|---|---|---|---|---|---|---|---|
| Gym first (3 + 2) | Full body | Easy run | Rest | Full body | Rest | Full body | Easy run |
| Balanced (2 + 2) | Lower body | Rest | Intervals | Upper body | Rest | Long run | Rest |
| Running first (2 + 3) | Easy run | Gym, heavy | Tempo | Rest | Gym, light | Rest | Long run |
Once the week is built, increase weights and kilometres one at a time. If your running volume goes up, keep gym weights steady for a while, and vice versa.
How SisuLift fits runs into your gym program
In SisuLift you can add running next to your gym program from the add menu in the Program view of the Workout tab (Add running to program). You pick 1-3 runs a week and a goal: general fitness, 5 km or 10 km. The app places the runs on free days using the same rules as above: tempo runs and intervals never land on the day after a heavy leg day, and the long run goes as far from leg day as possible. If the rules can't be met, the hard run is downgraded to an easy run.
When your gym program has a recovery week, the runs get lighter too, so recovery is handled by one logic instead of two separate apps. Running distance and time go into the same history, and pace per kilometre shows right after logging. Adding running to the program is part of Premium and also works during the 14-day free trial.
Sources
- Wilson JM et al. (2012). Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises. Journal of Strength and Conditioning Research 26(8).
- Schumann M et al. (2021). Compatibility of Concurrent Aerobic and Strength Training for Skeletal Muscle Size and Function: An Updated Systematic Review and Meta-Analysis. Sports Medicine.
- Sabag A et al. (2018). The compatibility of concurrent high intensity interval training and resistance training for muscular strength and hypertrophy: a systematic review and meta-analysis. Journal of Sports Sciences.
- Blagrove RC, Howatson G, Hayes PR (2018). Effects of Strength Training on the Physiological Determinants of Middle- and Long-Distance Running Performance: A Systematic Review. Sports Medicine.
- Rønnestad BR, Mujika I (2014). Optimizing strength training for running and cycling endurance performance: A review. Scandinavian Journal of Medicine & Science in Sports.
→ Read also: The deload week in strength training | All workout programs