Train with the fitness you have for the fitness you want. Not with the fitness you wish you had yet don’t.
Be consistent. With all the demands of life that weren’t there for the average 25-35yo, you have to make working out a priority at 45+. Instead of taking the day off bc shit hit the fan even a 15min run > no run.
worry about 2 sports now. Add in the 3rd. later. It’s easier to build fitness in 2 sports than 3.
Do little things that facilitate working out. Leave a bike on the trainer so you don’t have to set it up to ride zwift. If you have a treadmill do a short 10 min T run after every ride or a 15min easy run before every bike. Extending the overall session duration is a powerful training tool. 4 workouts of that can be 40-60min more per week at a very low recovery cost if you go easy. And you should go easy. No hard running .3-.4mph slower on the treadmill on these than you might normally run
As we age, especially on the run, we have more neurological decline and less elasticity in our muscles. This is not a prevalent on the bike because there is always some short hill to blast up. You need to reverse this with short fast :05-:06 efforts after a run. Just enough to start to get that back but not long enough to tear a hammie. The progress to strides, uphill strides, uphill reps all this before progressing to things like 400s/800s miles. Sure that sounds dumb as in why would I do a few 20m fast efforts but you have to condition the tendons to going fast. It sounds tedious as in it’ll take a few months before you get to intervals but it beats tearing a hammie. That will set you back much more than not doing intervals.
Did I mention hill reps - you can’t run enough as you get more miles under your legs. Great for improving economy. One of my 65yo athletes KQ’d on 4, yes you read that right, 4 interval sessions last year. But he did do hill reps 2-3x week all freaking year. He only ran 23 min faster than he had in the previous 4-5 seasons off the bike, not shabby for the 60+ AG. Plus hill reps are good for fixing over striding, recruiting more motor units etc
Speaking of motor units doing some lifting will help. Doesn’t have to be much, even a 20min session 2x week will help. You can do everything you need to and some of what you want to in 20 minutes in the gym.
Sleep - It’s the #1 training tool most triathletes, let me correct myself, most athletes underutilize. Alcohol is probably the #1 thing that should be utilized less especially since if you’re not day drinking (which is the best drinking) your drinking usually close to going to sleep, Alcohol can negatively impact sleep. Did I mention what your #1 underutilized training tool is?
Hope that helps. Walking you rdog more often and/or longer will never hurt, Your dog probably won’t complain as well. Off to go walk mine for 4km