I am now training for marathon running and marathon swimming simultaneously for coming races in both sports.

Will this be likely to give me better or worse performance than if I only do a single sport, if the training amount and methodology is exactly the same for a single sport?

E.g. I'm swimming 4 times a week with 15 km total, and running 3 times a week with 45 km total to train for both marathon swimming and marathon running at the same time.

Will my running performance likely be better or worse if I stop swimming, and only run 3 times a week with 45 km total with the exact same structure?

  • 1
    This is based on nothing, but if the total amount is within what your body can handle without injuries and recover from. there should be some improvement of the combination. Would be interesting to see some scientist looking at Strava data for a real answer and not opinions Dec 21, 2019 at 9:53
  • Depends what kind of recovery you're getting. With high volume there's always a risk of over training. If doing both is over training, (depends on your lifestyle etc), then you'll most probably run better if you reduce the swimming and vice versa.
    – E.Aigle
    Mar 31, 2021 at 8:59

3 Answers 3


I think you would perform better in running if you would concentrate on it. But that doesn't mean you shouldn't be swimming, your body needs some variety that it won't get boring.

But if your goal is just to run a marathon, not the fastest time possible for your Body. Then this is okey too, because you will still improve your Cardio either way and this will help in the opposite sport as well.


Given what you're asking, it probably boils down to your specific body, and can't really be answered in the general case. When I was training for my first triathlon, I had the least experience with swimming. When I started swimming, I put on surprising amounts of muscle in my arms and shoulders. It was enough that for longer runs, I felt the weight. The extra endurance exercise helped my conditioning so it was probably a wash for my running.

If you're one of those people who can just glide through the water like a fish, and don't really put on muscle that quickly, then it's probably mostly additional conditioning, which is helpful right up until the point you overtrain.

But if you're like me, or more so, it might get more complicated. Also, what would you be doing with your suddenly free time? Getting rest? Eating nachos?...

I think that the answer for you is not going to be applicable to everyone, or even nearly everyone. Same for me. Try it and see.

I will say that if you're training for a marathon, your mileage is lower than I used in my marathon training.

Good luck with your races.


Having tried it both ways, my experience has been that doing both is optimal as long as your diet and recovery supports the toll on your body taken by both activities. You might have to mix and match rates of exercise and rest days to get the right mix of time on the road / trail and time in the water to figure out what optimization looks and feels like. I wouldn't wall yourself into your current plan [I'm swimming 4 times a week with 15 km total, and running 3 times a week with 45 km total to train for both marathon swimming and marathon running at the same time] if it's generally arbitrary; be self aware and play with your training plan. The other important variable is how much time you have to prepare. I don't mean to insult your intelligence if you've competed before but the closer you get to game day the less risk you should take in over doing it. Lastly, only YOU know what you need work on... Take that into account in terms of the competition and apply the time and energy to what needs more work. If you're a phenomenal runner than swim a bit more, if you just glide through the water, spend a little more time on the road. Come game day it will less about training optimization and more about your times. Good luck out there!

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