ChatGPT made me strong

The fitness wars with AI have escalated. It started four months ago when OpenAI put out an ad showing how you can use ChatGPT for fitness.

Anthropic recently responded by making fun of OpenAI for putting ads in ChatGPT (starting today).

We'll see how long Anthropic holds out before inevitably introducing ads themselves. I tend to prefer Claude for most things, but joke's on them, because I already used ChatGPT to get strong.

In early 2025, I started to focus more seriously on my health, and I remembered reading an article in late 2024 from Men's Health about using ChatGPT to replace a fitness trainer. Unfortunately, the author was pretty biased, and most of the issues stemmed from a lack of understanding about how to effectively use LLMs. I decided to try it myself with the requisite context.

Context

Context engineering is one of the most critical things to get right to get the most effective output from LLMs. I compiled the best data I could for an effective prompt including:

• 6 months of training data - I've been inconsistently strength training at the gym for years and have recorded my exercises, weights, and reps consistently in the same FitNotes app. I exported that data in .csv format to share with my prompt.
• Muscle Building Plan - Ironically, the Men's Health editor failed to ask ChatGPT to use their own resources to build a plan. I didn't. I told ChatGPT to use this as its source of truth to ground any fitness plan.
• Research mode - This caused the LLM to pull the latest health research and scientific studies to validate and tailor the training plan to me.
• My health history - I detailed my history of shoulder issues to ensure the plan didn't aggravate those
• Personal preferences - I specified I wanted to do three days per week, one hour per workout. I asked it to prioritize hypertrophy (bigger muscle size) and long-term injury prevention.

This kicked out a great weekly schedule that I saved to a PDF and now reference each day in the gym. Over time, I asked for substitutions and variations as I injured my knees or grew bored with the plan. 

Eventually, I moved the plan to Claude and massaged it more. I added recommended rest periods, and even an optional 4th day of accessory work. You can see the plan here.

This plan does a great job of balancing push/pull activities, as well as compound and isolated exercises. All backed by research and the latest in diet and nutrition. And no, I don't skip leg day!

Results

I've been pretty happy with it. I paired my plan with eating better (using the MacroFactor app), and over the course of just five months I saw real progress. Obviously, LLMs didn't consistently drag me to the gym three times a week or force me to eat healthier, but I stuck to the plan, and I've been happier and healthier ever since.