Q&A w/Coach Brian: Combining Cardio & Strength Training

Question from Dominique Alessi: For someone that wants to get better at both cardio (e.g. running) and weightlifting, what would you suggest? I would imagine there’s a point at which cardio will impede your weightlifting progress and vice versa, but it also seems that cardio and strength are less antithetical than we once thought they were.


You are correct: training for both strength and endurance are much less antithetical than we once thought. For a brief history, I have had my feet in both general strength & conditioning and CrossFit coming up on 21 years at the writing of this article, and I remember back then the dogma was you cannot train both fitness qualities at the same time with the expectation to make much improvement in either strength or endurance. Concurrent training was seen by some as an inferior method due to a phenomenon known as the interference effect (a reduction in the rate of strength, power, and hypertrophy when endurance training is added to a resistance training program). Much of this idea hinged on the 1980 Hickson study “Interference of strength development by simultaneously training for strength and endurance” that examined three exercise groups (strength training only, endurance training only, and a combination of strength and endurance training). The study showed that there were no differences in strength adaptations in the concurrent program until after the 7th week, when subjects saw a decline in strength in weeks 9 and 10 leading researchers to conclude “these findings demonstrate that simultaneously training for [strength] and [endurance] will result in a reduced capacity to develop strength…” This study and its abstract (because who has time to read the whole damn thing) persevered in the fitness community for many years.

The predominant opinion in the early years of CrossFit was that constantly varied training was less than ideal for maximizing the 10 components of fitness. CrossFit would get you mediocre at everything at best, and injured at worst because it is a “shotgun method:” a wide spread of training stimuli to target multiple qualities all at once. Not everyone felt that way (Greg Glassman being the founder of CrossFit, as well as the late sprint coach Charlie Francis arguing to “do all the components, all of the time”) but there were enough voices out there to either drown out the dissenting opinions or so many “experts” were touting this either-or notion that it was just taken as a fact without question.

However, CrossFit has turned that notion on its head in the last two decades, making many question whether the interference effect is actually something to be concerned about, or that it may simply be poor planning coupled with dogma taken as fact. The performances of athletes at the CrossFit Games clearly fly in the face of the interference effect, and in a more traditional sport, the Decathlete and Heptathlete are able to be very well rounded across strength, power, speed, and endurance. Hell, even bodybuilders do not appear to inhibit their strength & hypertrophy gains despite doing significant cardiovascular training for shows. As a personal anecdote, I am comfortable maintaining <7 minute/mile pace for just over 5K while still being able to squat over 400lbs for multiple reps (sometimes even on the same day, hours apart), although most people assume I am just the “lifting guy” at this gym.

So why did the 1980 Hickson study come to the conclusion that concurrent training leads to poorer strength outcomes? Let us look beyond the abstract and into the methods section of this study. The strength training group performed 5 days per week of training (squats, deadlifts, leg presses, leg extensions, leg curls, calf raises, and situps w/approximately 80% of 1RM). The endurance training group performed 6 days per week of training (alternating 3 days of interval training on a bike and 3 days of 30-40min runs). The concurrent training group did the exact same workouts, at the same intensities as both the strength and endurance group, with ~2hrs of rest between sessions. It becomes painfully obvious why the concurrent training group had lessened strength gains than the strength only group. The authors themselves make a note in the discussion section of their own paper.

It does not take a PhD to understand that this is an extreme volume of training irrespective of training age and fitness level. There is a reason you should not expect great training results if you did both Hyrox and OlyWOD/CrossFit WOD 5-6 days per week for 10 weeks on end. If you were to properly periodize (plan) your training, you would avoid the interference effect and would see a similar rate of improvement with concurrent training as you would for strength only or endurance only training. Specialization is an entirely different topic for a different article. Study after study (and meta-analyses) in the last decade have demonstrated this. CrossFit is obviously one of the best methods to develop a well rounded and robust fitness base.

This is why at CrossFit NYC we program on a sliding scale of volume/intensity on our Strength and Conditioning pieces. On days where we are performing a large volume of Strength, the Conditioning is often a little less intense, intervals, or shorter in duration to avoid much conflict with maximal strength gains, and vice versa where the Strength portion may be more skill oriented. A practical application at this gym for your own goals: simply dial one portion of the WOD up or down as you see fit. If you desire to develop more conditioning, then you should dial back your intensity or volume in the strength portion (drop 10-15% of the weight or perform fewer sets/reps) and put more effort into the Conditioning that day. If you wish to improve maximal strength, then slightly dial back the weight, volume, and/or intensity in the Conditioning until you achieve your strength goals.

*If you have any more questions related to fitness, please send them to [email protected]*

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