Are you doing any plyometrics or isometric exercises?
Consider split squats, single-leg calf raises, bridges, and pull-ups.
I’ve been following Mike Rosa’s YouTube channel, Anabolic Aliens, for a while now. He has an excellent series of intense five-minute workouts tailored for different equipment levels (bodyweight, dumbbells, resistance bands, etc.). I’ve found doing 3-4 sets per muscle group to be really effective! He also offers an app called Exerprise that incorporates many of the same workouts but generates custom routines based on your time, sets, equipment, etc.
I use a weighted vest (45 lbs for a 6’1” male weighing 165 lbs).
This vest is great for rucking (long walks with weight) because it’s comfier than a backpack. I also use it for squats and one-legged squats, often with extra weights in my hands.
Rucking is an amazing exercise. Regular power walking no longer boosts my heart rate without incorporating odd movements. The vest allows me to raise my heart rate and potentially helps prevent injuries (though I haven’t found any research on that).
I use rucking to balance my running; when I run more, I walk less and vice versa.
P90X Legs and Back really opened my eyes to how weak I actually was, even while running 70 miles a week.
Did anyone save the top comment? I wanted to read it but found it deleted.
Dr. Mike just released a video for you: Check it out
Also, investing in gym rings for around $30 is worthwhile if you find a spot to hang them. You can perform tough single-leg and core exercises with rings. Search on YouTube for ideas.
Here’s a link to a workout I love: Iron Strength Workout.
It’s intended for incorporation 1-2 times a week and focuses on all the muscles important for runners, designed specifically by a runner and doctor.