How to get bigger as a runner?
I’m a competitive runner and have drifted toward longer distances over the years. I’ve completed multiple marathons under 2:30, so most of my training is very endurance-focused. During marathon builds, I’m usually in the gym 2–3 times per week, but it’s almost entirely running-specific work: lighter reps, stability work, smaller muscle groups, impact training, improving running economy, etc.
My physique isn’t bad, but it’s definitely very “runner.” I have low body fat overall, but really thin arms and legs, and I’ve never had super visible abs. I’m 6’0” and around 155 lbs. I’ve honestly never really tried to gain weight or build muscle before.
What I’d really like is to add some size in my arms, chest, and calves while also getting a more defined six-pack. I still want to keep running at a fairly high level, but I’d like to look a little more athletic/filled out instead of just skinny endurance runner.
Does anyone have advice on how to approach this? Especially balancing marathon training with hypertrophy, nutrition, and putting on muscle without feeling sluggish?