The Interference Effect: Can you Train Strength and Endurance Concurrently?

Should Decathletes run 7 miles on Sunday morning just to improve their 1500m time?

Can you train both short-to-long and long-to-short at the same time?

Can you train for strength AND train for endurance, for example, the STREND event?  (i.e. 5 weight events followed by a 5k/3 mile run?)

And don’t get me started on Crossfit!

Can you Train Strength and Endurance Concurrently?

Interference call in Hockey

The answer is, of course you can, but is it beneficial?  Will it work?  Is there an interference at the muscle fiber level?  Or, more specifically, at the molecular level?

Time an time again, I hear this argument.

Here’s my take…

Take the 1st Law of Thermodynamics:

Energy cannot be created nor destroyed.  You only have certain amounts of energy.  I do weights after the running workouts and the weights are nowhere near my max.  Weight Training and Olympic lifting is not my sport… I want to run fast.

But when I got injured, and stopped running, my weight numbers exploded!  I could never bench 3 plates (i.e. 140kg or 315kbs) until I actually stopped running.

All the energy I was consuming was now going to the weight room.


strength–endurance continuum SEC

Before I go into the discussion, we need to talk about Charlie Francis “vertical integration”.  Many others have plagiarized this concept but basically it’s doing all components of training all the time.

We do speed, speed endurance/special endurance, aerobic conditioning (via tempo runs), weight training, Olympic lifts, plyos, med ball, core all year ‘round.  In a given week, we cover them all.

By knowing how this works is important in setting up your annual plan and determine what exercises you need to do for muscle adaptation.

Concurrent Strength and Endurance Training

There is a great read titled Concurrent Strength and Endurance Training: From Molecules to Man by Gustavo Nader.

Basically it says to avoid combining hypertrophy strength training (i.e. 10+ reps) with high intensity endurance training. That’s mainly where you’ll see an interference effect.  Low intensity endurance combined with hypertrophy strength training (10+ reps) is acceptable.  As well, you can combine max strength training (5 reps or less) with high intensity endurance.

Why is this?

Without going into biochemistry and physiology in detail, hypertrophy training and high intensity endurance training both stimulate peripheral adaptation.  That’s interference.

Also, high-intensity endurance training increases capillary density as well as the mitochondria density… which are reduced in hypertrophy training.  Again, that’s interference.

This is why I am surprised when I see baseball players train (this is February… Spring Training!).   A lot of them, especially pitchers, do a lot of cardiovascular endurance training when the sport is clearly power and speed.   Baseball players should be doing more plyometric, explosive weight training and short intervals on the track.

I’m not saying baseball players should NOT do cardio, but watch the intensity.

To close out this discussion, it really all boils down to 2 factors when designing a training program for any sport:

Volume x Intensity

Comments, anyone?

Jimson Lee

Jimson Lee

Coach & Founder at
I am a Masters Athlete and Coach currently based in London UK. My other projects include the Bud Winter Foundation, writer for the IAAF New Studies in Athletics Journal (NSA) and a member of the Track & Field Writers of America.
Jimson Lee
Jimson Lee
Jimson Lee
  • very interesting Jimson, thank you.
    this is exactly what crossfit is attempting as they incorporate some endurance runs, usually 5-10km, into an otherwise anaerobic/weights routine.
    however even the elite crossfitters are relatively poor distance runners, which would support the idea that it is impossible to have all energy systems fully fired up in the same individual at the same time.

  • and let’s not forget EPOC. High intensity training will raise EPOC for up to 48 hours, resulting (eventually) in chronic fatigue for the un-trained/de-conditioned, if no rest (or active recovery) periods are prescribed.
    Also, doing back-to-back high intensity will not aid glycogen replacement, leading to chronic fatigue (eventually). Most coaches will prescribe endurance training as part of an ‘active recovery’ phase, enabling the athlete to recover whilst working a different area of fitness.

    • As a survivor (just…) of the early 1960’s ‘sand dunes and training runs of 30 miles will improve your mile times’ rubbish, I find ‘active recovery’ is an oxymoron. Recovery means minimal activity, or better yet, absolute rest. Training must be specific and progressive, from lower to not-quite-so-low, to higher-ish to higher, and then high! Pre-tests are essential, and advancement from a lower to a higher level should be based on post-tests. Pain is unnecessary in training and should be confined to competition. Power training (not Powerlifting), with low reps and maximum weight moved fast, combined with a similar approach to high intensity interval training, with almost complete recovery between reps on the track, (not the road, country hills or dales), and plenty of time off between training sessions will produce the most appropriate adaptations. Oh yeah…. youngsters need recovery, middle-aged need recuperation, and old-farts need convalescence! Ha! :) Just and opinion, guys…

  • Almost (and in generally) true from a methodological point of view. But I think that the debate was more oriented on generic terminology and classic principles or classification; probably about cycles and their dominant orientation than about planing sequences inside the micro-cycle. May be I am wrong, my English is not the best. But I’d not make the confusion between a low speed workout session coming after a HI one, and a specific endurance workout session. I’d rather call that recovery workout session.

    Anyway, this is a kind of fundamental or (may be) the primary question – the “to be or not to be” of the physical conditioning.

    The previous quotation is the reflexion of a 75 years old track and field coach (50 as coach)… Constantin Dumitrescu – nobody heard of… He coached few Romanian champs and most of them have been recruited, trained and formed by him from childhood to the end of their career – very important and helpful regarding the possibility to retrieve valuable data and to get to some solid conclusions… But in this world performance talks so one of his athletes was the first woman who high-jumped 2m… Back to the story… so the first time I heard about his “concern” in 1995. Since than I saw few PHDs writing interminable works assuming a kind of innovative approach with this “questioning”. He told me that is a quiet old and shared “dilemma” – since the 80’s – for many coaches around the world. It’s a little bit hard to find out more from these people, but in my opinion for him was not a dilemma at all. He made his choice 30 years ago.

    It’s an interminable long talk here so I really don’t know. Experiments might help (not sure), even if protocols and interpretations are always subject of polemics but… If this can help (!?), could someone explain to me what does it mean, please (!?) :
    Early-phase muscular adaptations in response to slow-speed versus traditional resistance-training regimens – Department of Anatomy, College of Osteopathic Medicine, University of New England, Biddeford, ME, 04005, USA,


    Thirty-four untrained women participated in a 6-week program to investigate slow-speed versus “normal” speed resistance-training protocols. Subjects were divided into: slow-speed (SS), normal-speed/traditional-strength (TS), normal-speed/traditional muscular endurance (TE), and non-exercising control (C) groups. Leg press, squats, and knee extensions were performed 2 days/week for the first week and 3 days/week for the remaining 5 weeks (~2 min rest). The SS group performed 6-10 repetitions maximum (6-10RM) for each set with 10 s concentric (con) and 4 s eccentric (ecc) contractions. The TS and TE groups performed sets of 6-10RM and 20-30RM, respectively, at “normal” speed (1-2 s/con and ecc contractions). TE and SS trained at the same relative intensity (~40-60% 1RM), whereas TS trained at ~80-85% 1RM. Pre- and post-training muscle biopsies were analyzed for fiber-type composition, cross-sectional area (CSA), and myosin heavy chain (MHC) content. The percentage of type IIX fibers decreased and IIAX increased in all three training groups. However, only TS showed an increase in percentage of type IIA fibers. CSA of fiber types I, IIA, and IIX increased in TS. In SS, only the CSA of IIA and IIX fibers increased. These changes were supported by MHC data. No significant changes for any parameters were found for the C group. In conclusion, slow-speed strength training induced a greater adaptive response compared to training with a similar resistance at “normal” speed. However, training with a higher intensity at “normal” speed resulted in the greatest overall muscle fiber response in each of the variables assessed.

  • …or…if you prefer regenerating/re-energizing workout session….because if after intensity, next day is coming volume just for changing the physiological (or the energetic) support, I really do not see the interest for the most of sports…(less the long distance race/runners)

  • this topic is to big. Not precise enough…bigger than USSR…too vast to debate around. Please Jimson, try to be more precise…bring it from general to particular – period of the season, age, experience in practice, etc. All these factors might change the perspective!…The best part of this thread JL quote: “And don’t get me started on Crossfit!” :)))))))))))))))))))))))