Honestly if you cannot fit 1 hr into your schedule of lifting, you need to evaluate your time management skills.
I'm a Ph.D Biomedical engineering student, and I have plenty of time due to my superior time management skills to lift, swim, run, and rock climb.
For example, I wake up at 7 a.m., go the work at 8 a.m. work till 11 a.m. I then swim or run for a hour, eat lunch, come back around 12:30 p.m. and work till 5 p.m. And then go lift at 5 p.m., come back home, prepare my meals and then read something non-scientific and then sleep. I work in the biomaterials field, and I plan my everyday schedule, such that I know how much time it will take to run my experiments, etc.
You and others believe productivity is defined by how much time you spend research. Rather I believe productivity is based on quality, meaning how much you MAKE of that time and not so much the hours. Again, Quality > Quantity, and this is a big thing in science and engineeering, where prestige of publications are based on quality of work.
Get your head out of your ass and start thinking... this is what scientists do! Stop following mainstream science world and society, and start thinking towards your goals.
If good god, you cannot even develop critical and creative thinking skills from starting a Ph.D, you don't deserve to be a chemist/scientist/engineer.