"I asked the coaches to name the single biggest change in elite triathlon training in 2017 compared with a decade earlier. The answers had nothing to do with wearable tech or secret workouts. Instead both gave the same answer: strength training." -Alex Hutchinson
This article by Alex discusses the "interference effect", between endurance and strength training.
According to Hutchinson, the most interesting point, in his view, is "Baar’s suggestion that you should design your strength workout to use heavy weights so that you reach failure after relatively few reps. This will maximize the metabolic signals for muscle growth, while minimizing the calories burned and metabolic stress."
And, "As you get stronger and hit the upper end of these ranges before hitting failure, increase the weight for the next workout."
As Hutchinson suggests at the end of this nice article, is that you shouldn't freak out unless you are in beast mode on a regular basis. He says that unless you are not undergoing endurance training 4+ times a week, or pushing beast mode 80%VO2 max sessions, you are unlikely to impact your strength gains with 4+ endurance sessions.
Find the article here: