Note: The following was taken from the Jim Wendler forum. It was in response to an older lifter, new to 5/3/1 but not new to training. However, he had not been lifting long and wanted some advice on his training. Below is my answer.
I've thought about this for awhile and I can't really give you very specific advise- training and getting older is a whole mess of issues that are very individualized. On this topic, I'm still learning every damn day and will be until the day I die. There are thousands of different roads you've gone down by age 60; unlike 13 years old where majority of kids are the same, or at least have had fewer roads to travel. And as we know, many of these roads beat you up in some way.
So here's some advice:
1. If you are interested in flexibility/mobility (as you've stated) - I really think this stuff is as important as strength training. HOWEVER, thankfully you don't need to devote a lot of time to it in order to get better. 10-15 minutes a day (or twice/day) is probably all you need to feel awesome. So....find a routine or a couple routines that you like (or at least you don't hate). I do basic stretches and use the foam roller. Nothing fancy. Understand that there are a ton of flexibility/mobility things that you can do; it's not just 'touch your toes'. Be consistent with this and you'll thank me in 10 years. I know in the "strength world" that this is heresy and a waste of time - but I don't care. It helps. You don't have to be perfect but you should be consistent.
2. Conditioning - most of your conditioning should be "easy" aka walking or something similar. HOWEVER, this doesn't mean you should never do crazy sh*t such as Prowler/sled, etc. Limit these things to once/week (at most) and enjoy them. But don't run yourself ragged.
3. Strength work - I don't know what you want to do or how your body feels; PR sets or pushing the last set is awesome for mind and body. HOWEVER, don't be afraid to only do sets of 5 on some days and call it a win. I am a big believer in big, barbell movements. But I also understand that there is some limitations with them. So learn how to do awesome assistance work that is balanced and builds some muscle. You can be as boring or creative as you need to be; essentially the way I use the barbell with people is akin to this: Barbell = power and awesomeness. Assistance = beefcake-ness
So really dial in on the barbell sets and then pump up like a stud on the assistance. With my youngest son (currently 10 years old)- we call the main lift of the day the "Berserker Lift". That means we want to be strong, awesome and powerful. We do ONE of these every training day. The other two movements we do are called "Beefcake Lifts" (assistance) - so he knows we are generally doing more reps and getting a pump. I fully acknowledge that he never gets a pump; but I am planting the seeds.
So in conclusion - if you don't know exactly what to do:
1. One main lift/day - some days are PR sets, some days only 5 reps.
2. Main lift is done with precision and power. You "own" every single rep.
3. Assistance is done to build some muscle, balance and support the main lift.
4. Do some kind of mobility/flexibility every single day.
5. Do easy conditioning more often than hard conditioning.
Start with choosing a training program that you can do as written and that fits in your schedule. Commit to it so you're not constantly negotiating before and during training sessions. That is a waste of energy. Don't overthink the introduction of basic stretching and conditioning. Just do something. Once you've hit a good stride you can be more specific with those and increase the challenge. Then? Never stop.