This is a topic I am quite interesting, because you’ll hear a lot of opinions from both sides of the fence. Just like with most things in life, I don’t think there’s a clear answer nor is there a right answer. However, I’ll aim to provide some research, thinking points and guidelines to help you strike the right balance for your own situation & goals.
Ultimately, the answer boils down to specificity and your individual situation. If you’re training to be a rugby player, it ultimately doesn’t matter if cardio training will dull your strength training, because you need both at the end of the day and more importantly, you need to be good at your sport.
Since it is well established that high-volume endurance training has a negative impact on muscle hypertrophy, strength and powerHickson, 1980; Jones et al., 2013; Kraemer et al., 1995
The concept of opportunity cost can bring you down a logical rabbit hole, where anything other than the said activity is hurting your performance. I.e., this is why professional sports players don’t play other sports and don’t also have second jobs (insane high salaries not withstanding). To be truly great at something, you’ll have to sacrifice everything else. It is very rare for a person to be a true phenomenon in more than one thing, whether that be powerlifting, playing golf, running a business or writing a novel.
Nevertheless, you came here to read if cardiovascular training will stunt strength performance. So with this in mind I look at two studies with somewhat different conclusions.
To begin with, at both extremes, marathon runner vs powerlifter, they are at opposite ends of the spectrum. I think it’s safe to say that if you’re training to run a full marathon, you won’t be able to display maximum trainable strength and vice versa.
What Do the Studies Say?
Wilson JM, Marin PJ, Rhea MR, Wilson SM, Loenneke JP, Anderson JC.
This study took a group of rugby & hockey players, all with prior strength & endurance training experience. Subjected groups to resistance training, steady state cardio & high intensity interval training.
They found all the groups to show similar strength gains across all groups, when looking at heavy squats to parallel after six weeks, The study only saw an increase in VO2 max for the individuals who trained either steady state or interval cardio training. They recommended cardio & resistance training, the order was of importance, since this study performed resistance training before any cardio training.
They also found that power, measured in vertical jump height to be compromised with in both cardio groups. The authors also point out the relatively short time span of the training study (six weeks).
Our results indicate that interference effects of endurance training are a factor of the modality, frequency, and duration of the endurance training selected.Wilson et al
This study had three groups, strength, endurance & strength & endurance. The workout protocols were as follows:
Strength: 30-40mins 5 days/week
Endurance: 40 mins bicycle, 6days/week
Combined: both protocols.
They found that the endurance & combined groups had increases in VO2 max levels. But none in the Strength group. The endurance only group showed no signs of increased strength. The strength & combined groups showed similar improvements in strength for the first seven weeks, but eventually levelled off & declined by the 9th & 10th weeks.
These findings demonstrate that simultaneously training for S and E will result in a reduced capacity to develop strength, but will not affect the magnitude of increase in VO2maxHickson
I’ve only looked at two studies, so there is a limited data set to base the following recommendations on…
Where does this leave us when deciding to incorporate endurance training into our strength training? Again, it comes down to our goals. Are you an elite level strength athlete? If so, 1-why are you reading this?, 2-your priorities would be to show strength at the maximum possible level, so I wouldn’t recommend any extra endurance training, outside of your specific sport/event.
These findings show that training for strength alone results in gains in strength, power, and speed while maintaining endurance. S[trength]+E[ndurance] training, while producing gains in endurance and upper body strength, compromises gains in lower body strength and does not improve power or speed.Hennessy Liam C.; Watson, Anthony W.S.
Journal of Strength and Conditioning Research: February 1994
For somebody like me, who’s priority is strength, but isn’t paid to do so, I could benefit from some aerobic training. Especially when it comes to improving activities not related to lifting weights, e.g., walking up a flight of stairs, hiking, working at a job that isn’t 90% sitting down. I could go on, but the fact of the matter is, I may prioritize strength development, but my life doesn’t revolve around sttrength and includes a lot of activities that don’t require me to deadlift 500lbs one time.
For moderator variables, resistance training concurrently with running, but not cycling, resulted in significant decrements in both hypertrophy and strengthWilson et al
Another thing to consider is the type of aerobic training, I like rowing, because it is low impact, very scalable and incorporates both upper and lower body. Something like an aerodyne or assault bike is another great choice, that also has the extra option of arms or legs only. Something like running would be low on my list of recommendations, because it is higher impact and slightly harder to scale that the rowing or assault bikes.
Finally, the volume of aerobic training will be a factor to it’s affects on strength. Based on the Hickson study, the subjects did 40 minutes of activity 6 times per week. Because this level of activity had a negative long term effect on strength development, I could make the argument that less than this activity would have fewer, if any, negative effects on the development of strength.
Since we’re assuming elite level maximal strength development is not the goal. We can use the activity level of 40 minutes, 6x per week as a good upper limit. This should minimize the negative effects on strength development, whilst still developing aerobic capacity. I’m currently on a twice per week, 30 minute maximum limit on each session, focusing more on steady state cardio, with a couple of HIIT sessions thrown in over a month.