When it comes to concurrent training there has been a lot of research, some have shown that there is an interference effect meaning the cardio interfered with the subjects ability to put on muscle or strength. The problem with these studies was they were designed to show an interference effect which is more of a design problem and a fatigue problem than an interference effect. We have seen research on the use of concurrent training to build both strength and hypertrophy while improving aerobic capacity. Why would a strength athlete want to do that? Because your aerobic capacity is far more indicative to your recovery than any other energy system. The more fit you are to a certain extent the better you will recover. The research shows that shorter duration aerobic work that is at least 6 hours before or after training with the modality being low impact, preferably a spin bike of sorts will lead to the least amount of interference if any.
A lot of people look at the research and see that the more aerobic work you do the more problems it can create to getting stronger and while I agree there was an interesting study done by Kilen et al 2020 where they looked at 290 Danish military recruits and put them through a program that required at least one hour of running and one hour of training each week on top of their current routine of PT, marching, etc.. which equated to about 20 hours a week. So a lot of aerobic work and very little strength training. They concluded "Weekly distribution of low-volume concurrent training completed as either eight 15-min bouts or two 60-min sessions of which 50% was strength training did not impact strength gains in a real-world setting."
This is an interesting finding to say the least, maybe we have put such a negative spin on aerobic training that we may be missing out on some opportunities to improve our recovery and our overall health. I am not saying to train for a marathon but a well designed aerobic plan that is year round will be far more of a benefit than a hindrance.
Reference:
Kilen A, Bay J, Bejder J, Breenfeldt Andersen A, Bonne TC, Larsen PD, Carlsen A, Egelund J, Nybo L, Mackey AL, Olsen NV, Aachmann-Andersen NJ, Andersen JL, Nordsborg NB. Impact of low-volume concurrent strength training distribution on muscular adaptation. J Sci Med Sport. 2020 Oct;23(10):999-1004. doi: 10.1016/j.jsams.2020.03.013. Epub 2020 Apr 4. PMID: 32371120.
