A specialist anaesthetist turned software engineer, Dr David Bell writes about exercise science, fitness technology, AI, and cycling from NSW, Australia.

How Peloton, Apple, and Spotify Engineer Their Workout Playlists (And Why Most of Them Get It Wrong)

By Dr David Bell, Specialist Anaesthetist (Retired), Software Engineer, and Founder of Align AI Fitness, NSW, Australia In Part 1 of this series, I covered 25 years of research showing that tempo, not genre, is the primary driver of music's ergogenic effect during exercise. The evidence is clear:

Anthropic, the Pentagon, and the Question Nobody Wants to Answer

By Dr David Bell, Specialist Anaesthetist (Retired), Software Engineer, and Founder of Align AI Fitness, NSW, Australia Three weeks ago, the company that builds the AI I use every day was blacklisted by the United States government. Not for fraud. Not for espionage. For refusing to remove two safety restrictions

AI's Second Moment: The Explosion That Changed Everything

By Dr David Bell, Specialist Anaesthetist (Retired), Software Engineer, and Founder of Align AI Fitness, NSW, Australia In October 2025, Andrej Karpathy, one of the founders of OpenAI and former head of AI at Tesla, dismissed AI coding agents in a podcast interview. "The reason you don't

The Science of Workout Music: Why Tempo Matters More Than Genre

By Dr David Bell, Specialist Anaesthetist (Retired), Software Engineer, and Founder of Align AI Fitness, NSW, Australia Most of us build workout playlists the same way: pick songs we like, crank the volume, and hope for the best. Rock fans load up AC/DC. Hip-hop listeners queue Kendrick. EDM devotees

What Apple's AI Health Coach Gets Right, and What It Will Probably Get Wrong

By Dr David Bell, Specialist Anaesthetist (Retired), Software Engineer, and Founder of Align AI Fitness, NSW, Australia Apple's Health+ project was supposed to be the moment AI fitness coaching went mainstream. An AI health coach built into your Apple Watch and iPhone, trained on data from Apple'

Which Fitness Wearable Actually Improves Your Training?

By Dr David Bell, Specialist Anaesthetist (Retired), Software Engineer, and Founder of Align AI Fitness, NSW, Australia The wearable fitness market is splitting into two distinct camps. On one side you have the general smartwatch (Apple Watch, Samsung Galaxy Watch), designed primarily as a smartphone companion with fitness features bolted

The Fitter You Get, the More Your Brain Benefits from Each Workout

By Dr David Bell — Specialist Anaesthetist (Ret.), Software Engineer, and Founder of Align AI Fitness — NSW, Australia We accept that the returns on fitness compound over time in the obvious ways. Your resting heart rate drops, lactate threshold rises, body composition shifts. But a study published this month out of