You're not a factory production line
Most people's first thoughts about productivity are about efficiency. It's much like a production line in a factory. How do you work longer, harder, faster and so on. How far can you push yourself and your team without burning out?
No one really seems to think about what you're trying to do in the first place. What exactly are you trying to do more of, faster and for as long as you can go?
Not all tasks are created equal. The 80/20 principle shows that you're probably not the best person to be doing most of the tasks that you've got to do.
What would happen if you minimised the impact of the low value stuff that clutters up your workday? Instead of indiscriminately trying to do "more" you found other ways to get the low value stuff done? Then you can focus on the projects that you want to be doing more of in the first place.
The high value tasks that only you can do. The projects that go to the core of your skills, knowledge and expertise. The meaty ones that you're itching to get stuck into. The ones that really make the difference to you and to your clients.
For more on why working harder and faster for longer isn't the answer, see The Power of Full Engagement and The Way We're Working isn't Working.