Right off the bat I think the best answer is Cardio then weights. Why? I hear cardio, especially running, is entirely catabolic and takes a long time to recover from. However you can prime your hormones for recovery with the anabolic response to strength training. So weights after cardio is the best way to recover from cardio.
And I’m not going to mention the opposite because as far as I know there’s no benefit to it.
So that’s possibility one. You can eat before, after, or during, or all of the above.
But maybe you don’t have the glorious amount of free time I do and can’t get in an hour of running followed immediately by an hour of lifting. Maybe you have a job or a life or even both or maybe, just maybe, that exercise load is high for your current level and it sucks too much for you right now.
Then, possiblity two, I’d start with a run – or whatever cardio but I’m always going to say run – in the morning to wake up. Then eat right away and rest. Rest hard. For at least 3 hours then hit the weights. If you don’t eat and rest you’re just sabotaging the strength training.
Possibility three then would of course be the opposite. Maybe you really like hitting the weights in the morning. So do it. I’d either eat and wait at least an hour upon waking up then lift heavy for few reps.
Then eat a lot and rest hard, like a hot bath and some yoga, before heading out for a run much later. Otherwise you’re asking for form breakdown and you’re really increasing your injury risk.
Now let’s you work a physical job. With a desk job you’re over-resting all day and that has it’s own set of problems that gets talked about a lot but there’s less out there for people who’s work is work.
Possibility four would be a run before work to wake up and loosen up. Then eat and make work your active recover for the day.
When it’s time to lift weight afterwards you can build your lifting plan around what you did at work. If you spent all day picking things up off the ground obviously don’t do high volume deadlifts. Do pull ups or overhead work. The key is to balance out whatever you did on the job with whatever you do at the gym.
So the opposite, Possibility five, would be hitting the weights before work and running after.
In that case I would structure the work out with higher reps and lighter weights. Even if you ate breakfast you won’t have digested it yet and you’ll need to work out the sleep stiffness so don’t get under a heavy barbell first thing in the morning.
And at work if you’re sore or feel an injury coming on don’t push it, don’t man up. You think maybe you should ask for help lifting something because it’s awkwardly shaped and your back feels strained? You goddamn do it. Asking for help might feel foolish for a few seconds but you’ll forget, hurting yourself at work will make you feel like an idiot for however many weeks it takes to recover.
Then in the evening have some liquid carbs so you’re not burning from an already empty barrel and take a relaxing wind-down jog. The solo time will take your head out of work-mode and you’ll shake off any stiffness that work might accumulate.
So there you go, one of those options will surely work for you but try out even the ones you think might not, it’s best to leave no doubt.