Meet Billy D
I started by following the same online programs many people buy. They promised better performance, but they did not explain what my body needed or why I was still stuck.
Training should explain your body instead of asking you to trust a template
I did not begin with a clear system. I was trying to improve my basketball performance, so I followed advice from the internet and bought programs from well-known online trainers. I tried one after another, hoping the next plan would finally tell me what to do.
Over time, I became frustrated with depending on an expert who could not see me, ask better questions, or explain why a program should work for my body. That disappointment pushed me to study human movement for myself. I wanted to understand the problem before prescribing the solution.
My work has since grown through graduate study, three years in NCAA performance environments, and four years of one-to-one private coaching. Bill Hartman's work helped me see how much potential can be developed when training starts with the person in front of you. I use those principles alongside my own methods and experience rather than copying one model.
That is also where the name comes from: B4 is short for before. Understand what your body needs before you train it, before you buy another program.
Credentials You Can Verify
Billy is the English name I coach under; the D. stands for Dai. Certifications show my legal name, Zihan Dai.
- M.S., Human Movement and Rehabilitation ScienceNortheastern University
- Certified Strength & Conditioning Specialist (CSCS)NSCA — #7348536088, valid through December 2026
- USA Weightlifting Level 1Earned November 2023
Better movement should change how you live and train
I get real satisfaction from watching a person understand their body, move with less hesitation, and see progress that lasts. That is why I do this work. B4 is built around careful observation, clear explanations, and one-to-one decisions that help your body work more efficiently in daily life and training.
Start With the Movement Diagnostic
See what Billy finds before deciding whether you need longer-term coaching. $99, one time.