Very few athletes train a single energy system, a single type of strength or a single type of endurance. The majority of events are a mixture along the continuum. Thus, most athletic training, even during a strength phase will include running.
We know from specialists that distance running hurts lifting and lifting hurts distance running- you can’t be great at both, but what about sports like football, rugby, lacrosse, and aussie rules football. They all require a good mix.
Sedano et al 2013 published a trial on concurrent training. 18 well-trained runners (VO2max above 65ml/kg/min) were divided into 3 groups. One which kept on running (8 sessions per 7 days), one which performed a strength based protocol with plyometrics and one who ran and performed high repetition weight lifting at 40% load. These protocols were followed for 12 weeks.
Pre/post-test analysis of counter-movement jump height, hopping average jump height, one rep max leg press, running economy, VO2max, maximal heart rate, peak velocity, rating of perceived exertion and 3km time trial showed differences (P <.05).
The strength-plyometric group improved it’s one rep max, running economy, peak velocity and 3km time trial. The mixed training group improved all of these except the time trial time. The traditional running group improved their VO2max and running economy.
Thus, if you have been training in a single modality for a while, change things up. The new method will stress your body in a different way. As long as it is transferable to your sport of choice- you will still improve.