@blade_302 Hill sprints work muscular endurance, work capacity, and anaerobic power. The hypertrophic stimulus is going to be very small unless you're starting from an untrained baseline. You need to get close to muscular failure to stimulate hypertrophy, and the form of failure involved in hill sprints is due to lactate buildup and muscular exhaustion. Those are very different things to the form of muscular failure needed to drive a hypertrophic stimulus.
Almost any lower body exercise with an external load will get you closer to muscular failure and thus be more effective for building leg muscle than hill sprints.
I'm a runner and thus do a fair amount of sprint work, including hill sprints. Yet, my quads are visibly smaller now than they used to be when I was getting in the gym on a more regular basis and doing proper externally loaded compound movements to get close to failure. Bodyweight and banded exercises were enough to maintain most of my muscle mass during COVID lockdowns, but the easiest way to build is with weights, and hill sprints probably aren't enough for anyone who's an intermediate trainee like myself to even maintain lower body muscle mass, and certainly isn't enough to build muscle mass.
Sprinting simply doesn't build muscle mass (unless, again, you're starting from an untrained baseline). Elite sprinters themselves spend a LOT of time in the gym. They sprint to get better at sprinting, and lift heavy to build muscle mass and strength. Even distance runners only sprint to develop better form and anaerobic power, not for the miniscule hypertrophic stimulus. Have you seen the legs on most distance runners? Many of them do more and harder hill sprints than you or I could even fathom, yet they look like that.
