Two people arrive at hybrid training with the same problem seen from opposite sides. One has spent years in the gym, moves decent weight and gets out of breath climbing four flights of stairs. The other runs half marathons and cannot do five pull-ups. Both know what they are missing. What neither of them knows is how to combine strength and endurance in the same week without one eating the other.
The interference effect: what it is and what is true about it
The idea is old and famous in gyms: endurance training interferes with strength and muscle gains. It became popular through studies in the 1980s and has been repeated so often since that plenty of people have concluded you simply cannot do both.
What has been seen since qualifies that quite a lot. Interference exists, but it is far smaller than the legend suggests, it shows up mainly when endurance volume is very high, and it affects power and speed considerably more than maximal strength or hypertrophy. In the other direction there is barely a problem at all: strength training does not hurt your running, it improves it.
Put another way: if your goal is to be the strongest person at a powerlifting meet, running forty kilometres a week will cost you. If your goal is to move well, be strong and not gas out, the problem is not combining them. It is combining them badly.
The three rules that solve it
One: the order within the session. If you do both on the same day, whatever you want to prioritise goes first, with a fresh nervous system. If you are after strength, the barbell comes before the rower. If you are preparing for a race, the running intervals come before the squats. Doing a brutal metcon and then attempting a heavy deadlift is not training two qualities, it is doing both of them badly.
Two: the gap between hard stimuli. Interference spikes when hard endurance work and hard strength work land too close together. With six to eight hours between them, or simply on different days, the problem all but disappears. The worst thing you can do is a long run on Saturday morning and heavy legs on Saturday afternoon.
Three: total volume. This is the rule nobody wants to hear. If you stack five days of strength and four of running because you read that both are good for you, you will progress at neither: you will accumulate fatigue. Four well-ordered days beat six badly distributed ones.
Three sample weeks
On three days. This is what most people with a job and a family do, and it works perfectly well. Monday: lower-body strength plus a short conditioning block at the end. Wednesday: running, with intervals. Friday: upper-body strength plus a metcon. At the weekend, if you feel like it, a walk or an easy run that does not count as hard training.
On four days. You add a day and gain room to separate things. Monday: leg strength. Tuesday: running intervals. Thursday: push and pull strength. Saturday: easy long run or a mixed session. This is the split that gives the best balance between progress and having a life.
On five days. Here you have to be more careful. Two clearly heavy strength sessions, two running sessions (one intervals, one long) and a fifth session that is clearly easy: mobility, technique, gentle aerobic work. The fifth session is not one more session, it is what keeps the other four working.
What to sacrifice when you can’t fit it all in
The bad week arrives: you travel, you sleep badly, work gets complicated. The temptation is to do everything half-heartedly. It is the worst possible decision.
If you can only train two days, do the two sessions that get you closest to your goal and drop the rest without guilt. The quality that holds up on low volume is strength, so if you are short on time, prioritise the barbell: it is lost more slowly and recovered more quickly than your engine. And if you are preparing for a specific race, then the race dictates and strength drops to maintenance, one session a week.
Signs you have overdone it
- Your resting heart rate goes up and stays up for several days.
- You sleep worse exactly when you are training most.
- Your usual weights feel heavier than normal two weeks running.
- You lose the desire to train, and not as a one-off case of laziness.
- Niggles that appear, go away and come back in the same place.
None of these signs on its own means anything. Three at once mean you should cut volume for a week, not push harder.
How we solve it at KOR
The hybrid training session comes pre-ordered, which is exactly what almost everyone lacks when organising things on their own: activation, a strength block with week-by-week progression, a conditioning block with set times and paces, and accessory work. Sixty minutes in which you know which part you are in and why, without having to decide yourself whether today is barbell or rower.
You will find it at all four clubs and we explain it in detail on the hybrid training in Barcelona page. If what you want is to understand how it differs from CrossFit before choosing, we compare them in this article, and if you come from the running world you will get more out of CrossFit for runners.
And if you would rather try it than read about it, the first class is free at any of the four clubs.