For a bit of context, my training for the last 2 years has consisted of full body training every other day, finishing each session with 15-20 mins of HIIT. I've built strength and size, but there's always been that lagging feeling of not being "athletic", conditioned or as fit as I could be.
Inspired by some articles I read I started building sprints (primarily hill sprints) into my routine around 6 months ago - typically into an upper-lower split so that I'm sprinting 2 x pwk (around 1000m total sprint distance per session). I feel like this has improved my body fat levels (around 12%) and I definitely feel more athletic, but it's had an impact on my upper body strength and size. My numbers have stalled (and possibly gone backwards in some lifts) and I'm convinced that my muscles feel flatter and less full.
Thinking it through, if we take shoulders as an example, with the full-body workouts I was training them 3-4 times pwk, and with the sprints routine this has dropped to 2-3 times pwk. My (perhaps irrational) mind is suggesting that this might be causing the perceived loss of strength and tone. Or perhaps the extra metabolic workload from sprinting has eaten into recovery?
Can anyone offer any words of wisdom here? I feel a little bit lost at this stage.