Imagine having a personal trainer right in your pocket, available 24/7. Thanks to AI, it’s not such a far-fetched concept anymore—at least in theory. The question is whether AI will become powerful enough to actually do everything as it’s been billed to do, and whether it can work as a personal trainer that’s right for you.
At first glance, the technology is exciting, especially since AI uses predictive algorithms from the data you provide to tailor your workouts to your fitness level. “I see AI going to the point where, in probably a few years, it’s going to be able to not just design, but modify and coach and adapt all of your workouts to your needs,” says Mike Israetel, the sports scientist, competitive bodybuilder, and fitness creator behind the Renaissance Periodization YouTube channel and RP Hypertrophy app for bodybuilders, in a recent Strong Talk episode.
The key phrase here is “a few years.” While Israetel does believe AI will transform the fitness industry, he acknowledges that it’s not a good tool for every fitness level right now. In this Strong Talk episode, he joins MH US fitness director Ebenezer Samuel, C.S.C.S to discuss the three major limitations of using AI for workout planning. The episode also dives into the two best ways to use AI right now and the future of AI.
The first issue with AI personal trainers is they don’t have a human body. While a workout routine may look good on paper, Israetel explains an AI can’t account for the varying changes a human body might feel, such as daily fatigue. With a human coach, he says, it’s easier to notice external factors and adjust a certain workout. AI, on the other hand, will never come up with the idea unless you tell them.
The second issue is that AIs rely more on their language training than they do on their three-dimensional world model training. To his knowledge, Israetel says AI models are not currently trained sufficiently on video. If they were, he could see the technology gaining a better understanding of deep physics and biomechanics of the world.
Think of a person going into a squatting position. You can infer the next position based on the movement of the knees and joints. Israetel says AI currently can’t make the same deductions.
“It just understands exercise from a logical and linguistic perspective,” describes Israetel. “It’s like the biggest nerd that’s never been to the gym but read every book about training.”
The last issue with AI is its context window problem. An AI’s memory isn’t infinite. The more you chat, the less it remembers the earlier messages. “At some point you run enough workouts, and it forgets all the workouts you did a while ago, because its context window shifts down,” explains Israetel. It’s similar to a coach forgetting that you’re focusing on lower body this week or asking you to do exercises you’ve already told them you can’t do. That might be a problem IRL too—but that’s an easy reason for you to find a better, more organised coach.
If you are interested in using AI, Israetel recommends approaching it in two ways. First, ask AI to give sample workout ideas. Don’t feel obligated to follow the full regimen because it may provide “some wacky stuff.” The second way is to look at AI as a “wizard” for your training. Instead of having ChatGPT write out workouts, use it to answer common questions, like whether slow eccentrics are better for muscle development than regular eccentric. Just double check that the model isn’t serving you hallucinations.
“For the beginner, leaning on AI to ask those questions is a good way to learn and develop basic knowledge,” adds Samuel. If you’re an expert, Israetel says you may be better able to guide AI toward higher-level conversation. Someone with a deep well of fitness knowledge is better suited to point out inaccuracies and when a response could increase injury risk.
Want more deep-dive fitness wisdom from Samuel and other celebs and experts who’ve been on our Strong Talk podcast? Check out all our episodes here.
Jocelyn Solis-Moreira, MS is the associate health & fitness for Men’s Health and has previously written for CNN, Scientific American, Popular Science, and National Geographic before joining the brand. When she’s not working, she’s doing circus arts or working towards the perfect pull-up.
