With increasing hand pressure and then shoulder neck pain that could potentially step from locking out your arms, all the lumps and bumps along the road jolt up through hands, arms and into the shoulders and neck with no shock absorption. The follow on from that would be why are you locking out your arms, bike fit probably, maybe too short of a stem or you’re far more upright than you think, maybe that stems from inflexibility, weak core perhaps meaning you can’t hold a position bent at the elbow for extended periods.