One of’s most popular training programs is Kris Gethin’s 12-Week Muscle-Building Trainer. Gethin is a world-renowned fitness icon who prides himself on his never-ending quest for knowledge, superior supplement line, and unrelenting ambition to demolish his body in the gym in pursuit of myth-busting, jaw-dropping transformation results. As a Certified Personal Trainer, Strength and Conditioning Coach and Sports Nutritionist, I have nothing but respect for Kris and what he’s done for the world of fitness, but I’m not going to let my admiration of his education, influence, or work-ethic sway my professional opinion as I dive into this program and assess the viability and responsibility of this hypertrophy training program.


Anyone who has written, seen or executed a professional training program knows that there is one thing you always find in the best of them: consistency. Consistency is difficult to find in the 12-Week Muscle-Building Trainer. Only 3 of the 12 weeks are structured consistently, and even those have participants switching equipment each workout, which makes exercise aptitude more difficult, not to mention decreases the feasibility that participants will have each piece of equipment available.

Breaking the program down into detail did reveal some method to the madness. Here is how each muscle group is categorized and targeted over the course of training:

  • Traps – 1 Workout
  • Calves – 10 Workouts
  • Legs – 12 Workouts
  • Chest – 12 Workouts
  • Back – 12 Workouts
  • Biceps – 12 Workouts
  • Triceps – 12 Workouts
  • Shoulders – 12 Workouts
  • Abs – 18 Workouts
  • Cardio – 20+ Workouts

For the life of me I don’t know how one “Trap” workout could be intentionally programmed, but considering I found several obvious errors as I was going through each week, it’s possible someone mis-labeled that particular day, but the exercises featured are consistent with trap-dominant movements so who knows. There was a day labeled as “Chest and Triceps” but in the list of exercises it was clearly Chest and Biceps. Some days are labeled “Calves” but many “Leg” days included calve exercises without including “Calves” in the title. Another day listed 5 sets but only provided the rep scheme for 3 of them, and another page was missing the description for an exercise, and that was just me scanning the days to glean the most critical information needed for this review. I would expect there are more errors to be found if you actually read each day’s workout thoroughly, but there is a video of Gethin training included with each day so I would hope that any confusion from the program would be cleared up by watching the video, as long as you have time to do that.

The overall structure to the program mirrors a typical bodybuilding split with most muscle groups being hit once per week, but again the way workouts and exercises alike shuffle and swap week to week makes it difficult to really understand where Gethin was going with this. Most weeks list the leg workout on Day 1, but 2 weeks it moves to Day 2. Sometimes Calves are trained with legs, sometimes with shoulders, sometimes with arms, for 2 weeks in a row they’re not there at all. Once or twice there are 2 workouts in a day, but otherwise there’s only one. It really is a difficult program to follow and understand.

Good exercise programs minimize the learning curve. The more days get restructured, exercises get swapped, rep schemes and volume change, the harder it is for the user to know which weight to choose, how to pace themselves for the rest of the workout that is coming, where to find the equipment, etc. As a trainer, I can see a lot of consistency and intentionality in the movements that Gethin programs each day of each week, but from a user’s perspective it’s far more chaotic than it needs to be. Muscle confusion is great, but user confusion is not. There is not a single week that is consistent with the previous one in terms of exercise selection, order, or intensity, and that’s a big red flag when it comes assessing a training program’s viability.

Will it work? Absolutely. I’ll say that right up front. If follow this program 80-90%, or somehow follow it 100% without tendonitis, you should definitely see some growth. Will you put on 20lbs like Kris Gethin supposedly did? Probably not. For those of you who don’t know, your muscles are a little more than 70% water. When you haven’t worked out in a while, your muscles lose some of that water, which is what makes it seem like you’re “losing all your gains.” Gethin apparently went 4 months without a real workout before Day 1 of the 12-Week Muscle-Building Trainer, so much of the 20lbs he was advertised to have gained was actually just water (and glycogen) replenishment to muscle tissue that already existed. I would estimate up to 10lbs of the 20lbs he gained had nothing to do with new muscle tissue growth.

The fluctuation between 30 rep and 5 rep sets covers the gamut of muscle fiber and hormonal stimulus. Not enough people try really high rep sets, so it’s cool that Gethin both utilizes and promotes them. He does so at the expense of consistent stimulus though. Five rep sets stimulate more of a neurological strength adaptation, but only if consistently performed week after week. Thirty rep sets target Type-1 muscle fibers which primarily stabilize the skeleton during movement. Great for joint strength, but because they’re the smallest of the muscle fibers, not so great for noticeable muscle growth. Most sets stick to 8-15 reps which is considered the most ideal for muscular hypertrophy, so with exception of some occasional stimuli for adaptations not specific to muscular growth, the exercises are largely geared towards hypertrophy.

Exercise Selection

I was for the most part pleased with the amount of free-weight, compound movements included in this program. One of the things you will learn if you ever choose to pursue a Strength and Conditioning or Personal Training certification program is the risk of injury associated with long-term use of machine-based exercises rather than free-weight (you can read my article on this here). Gethin includes some great compound movements like Bent Dumbbell Rows, Incline Barbell Bench Press, Barbell Squats and Straight Leg Deadlifts to supplement the heavy volume of machine exercises like Hack Squats, Leg Extensions, and Smith Machine presses. Gethin has to rely on machines more than most due to some injuries has had and still deals with, so for him to substitute free-weights with machines it makes more sense, but it’s worth mentioning that those who don’t have injury limitations should have a different exercise selection profile than Kris.

Most of the 12-Week Muscle Building Trainer’s upper body exercises are excellent free weight and cable options. The biggest discrepancy I saw amongst the exercises was the frequent use of the Leg Extension machine. Rather than explain here why appropriate times to choose this movement are few and far between, I’ll just link to to a detailed article about it, featured on a website the average person reading this already trusts: The Truth about Leg Extensions. Gethin himself mentions experiencing pain around his knee-cap so bad after the very first week that he had to skip Leg Day the next week so he could heal. This is by no means a direct consequence of any one movement in particular, but as a professional on the outside looking in and seeing the exercises chosen and the volume prescribed (which I will touch on later), it is not surprising that Gethin frequently mentions the agonizing pain during and after his workouts in the daily diary of the program.

Frequency / Duration / Density

Being a typical Bodybuilding split (aka “Bro-Split”) each muscle group is trained primarily 1x/wk, with the exception of Abs being trained more frequently. I like the amount of core movements and cardio there are, and in most cases I like the over-all volume of the rep schemes for each muscle group, but it has been well documented that spreading a high volume out over 2 days is often more efficient and effective than isolating it to a single day, especially in well-trained athletes like Kris Gethin and many of the people committed enough to try this program. Here’s an article at Men’s Health that corroborates this so you don’t have to take my word for it, but completely apart from reducing the risk of straining a muscle, tendon or ligament by cutting a day’s work in half, a stimulus can be added 2-4 days after the previous one to further stimulate growth. This not only gives sufficient time for the muscles to recover from the first workout, but it prevents any loss of progress that might occur were there to be several more days without any further stimulus.

Since the volume of this program is limited to a single day of training each muscle group, the duration and density of these workouts is not for the faint of heart, or those with limited in time. Nine workouts list over 600 repetitions be performed, one even goes over 1,000. If a single “rep” lasts 2 seconds on average, that’s 32 minutes of just repetitions. These workouts are dense. With abnormally high rep recommendations up to 75-100+ reps per exercise and usually 6-8 exercises per muscle group, participants are not only going to be committed to staying at the gym for 2-3 hours some days but 3-6 days of serious soreness that could deter many from continuing with the program, or even disallow them from doing so.

Volume / Intensity

Looking back at some of my most successful programs, 300-500 reps is pretty easy to achieve in a single workout. The difference between how I program for the average person and how Kris Gethin’s 12-Week Muscle Building Trainer programs for his followers, however, is he programs 300, 600, 800, and 1,000+ reps for a single muscle group, whereas when I program 300-500 reps it includes at least 2, often 3 muscle groups. That’s a very, very big difference in the amount of trauma a muscle is experiencing within just one or two hours.

I don’t necessarily think 600, or occasionally even 800 reps on a single muscle group in a single day is unrealistic, but the amount of metabolic distress and Central Nervous System fatigue this kind of volume would trigger would need to be given adequate time to recover from, regardless of how muscle group training is split. Gethin doesn’t do this though. Immediately after the 1,000+ rep leg day, he wants you doing an 800+ rep chest day, and no, neither are split into two-a-days. Now I am neither by profession or experience a professional bodybuilder, but given my countless hours spent in the gym as both an athlete and a trainer, both doing and observing many a bodybuilding workouts and even more bodybuilders, I have never heard of or seen anyone doing this many reps in a single workout, much less back-t0-back. It’s no secret that competitive bodybuilders today are basically required to “enhance” in order to stand a chance on stage, or even qualify. Steroidal supplementation vastly improves the body’s ability to execute and recover from high-rep and/or high-intensity workouts like these. Given that I’ve never seen known steroid-enhanced bodybuilders doing anything like this, the nicest way I can describe this kind of programming is irresponsible, and I’ll discuss this further in the next section about injury risks.

The intensity of these workouts is actually in the hands of the participants since resistance levels are not directly suggested. More risk-averse users will (and should) choose conservative weight, while more aggressive users (your average “bro”) will likely throw caution to the wind out of solidarity with the “hardcore” mantra Gethin envelopes. Kris knows his body, he knows his strengths, and he knows his injury limitations, so Kris Gethin knows better than anyone how to safely complete Kris Gethin’s 12-Week Muscle Building Trainer. The problem is, hundreds and potentially thousands of people are likely going to try this program and very few of them will have the expertise or self-awareness of Kris Gethin, making it extremely likely that they will over-train. When reps are high and intensity follows, it becomes more than probable that instinct will take over and movement mechanics will begin to compensate for fatigued primary movers and begin shifting workload to the joint stabilizers. When stabilizers begin assuming the role of movers, bones start shifting out of position at the joint. This is when impingement, cartilage damage, strains and sprains become increasingly likely. I know this from personal experience; it’s what inspired me to pursue my professional education in fitness.

Risk of Injury

There are two things I want to point out about Kris Gethin’s 12-Week Muscle Building Trainer when it comes to consideration of injury risks: relative intensity and perceived education. I have already addressed that much of the injury risks falls on the user as their warm-up, weight selection and cool-down are unguided and left up to the participant, each of which plays a significant role in risks prevalence. But assuming all those are perfect, the amount of reps in this program push relative intensity at or near 100%. As I said before, even enhanced bodybuilders do not typically perform as much volume as several weeks of this program prescribe. If competitive (enhanced) bodybuilders don’t normally train this hard, yet look as good as they do, can you honestly say to yourself that this style of training is worth the time, pain, and potential injury?

The other thing to consider is the perceived education someone gets from the 12-Week Muscle Building Trainer. Kris Gethin is all about challenging what the body’s limits are and breaking down mental barriers. I’m all about that too, I just err on the side of caution more because I’ve experienced what carelessness and/or ignorance can cause (Degenerative Disc Disease, Bulging discs, SI joint dysfunction, torn rotator cuff and more). When someone does a program like this, written by one of bodybuilding’s most esteemed icons, they are likely to think “this is how you are supposed to train”, and that’s just not true. At most, ‘this is how you can train…sparsely.’ It is certainly not a realistic way to train on even a semi-regular basis.

Asking athletes to switch equipment each subsequent muscle-group workout while simultaneously sky-rocketing the sets/reps makes it very difficult for participants to select the right weight and improve their movement aptitude. And I don’t care who you are (or that I started a sentence with a conjunction), 600, 800, and 1,000+ rep days are going to demolish your CNS, metabolic pathways and muscle fibers, so asking people do this 9 times in 3 months (sometimes back-to-back) is just unnecessary and appeals too much to the “hardcore” mentality we think is required to succeed at anything. The fact is, most famous athletes are successful because they avoided serious injury. Sometimes injury can’t be prevented, but in the gym when we are supposed to have control over our environment and our stimulus in order to maximize training benefit while minimizing risks of injury, it should be. Gethin’s self-described knee injury in Week 2 that left him unable to do that day’s workout and another day I happened to see where he was very ill don’t speak well of the safety and responsibility of this program. It is my professional opinion that a program like this was a cool idea, but was not given enough attention to detail and should be re-worked to iron out the inconsistencies and create a more direct approach to the end-result.


There is a culture around not just around fitness but in sports themselves that the harder your push the greater you are. We all know and love the stories of people who won a Super Bowl on a broken leg, qualified for the Olympics with a torn ligament, or came back to win a Championship after a traumatic surgery. We all love underdog stories and inspirational come-backs regarding supposed impossibilities that all of sudden become conquerable. It gives us hope that things we thought or were once told are impossible may in fact be achievable with enough hard work. For what it’s worth, sometimes this will prove true, but in reality it will often not. There is a time and a place for pushing well beyond your comfort and safety zone, and that is on competition day, or a day you have trained and prepared for to go balls to the wall and leave it all on the court, track, field, or weight room. A good training program strategically prepares you for this day. It assesses the upcoming challenges, evaluates your strengths and weaknesses, and adapts a training program to balance and improve your athleticism to best fit the demands of the competition or performance.

Kris Gethin’s 12-Week Muscle Building Trainer is too inconsistent and varying for me to say that it adequately prepares anyone for the volume that doubles between Week 1 and Week 3, and triples between Week 4 and Week 10. The exercises change too frequently, the work load is too concentrated, and the example it sets for participants is as I mentioned previously, irresponsible. I am completely on board with Gethin’s nutrition guidelines, the man has been influential in my own nutrition knowledge and decision making so I don’t have any critique of the nutrition or even supplementation recommendations. I am personally not a fan of supplements most of the time but Kris’s products are some of the cleanest you can buy and he is more modest than most in his recommended intakes, so he is fair in his promotion and suggestion of his supplements brand.

I have to close with reminding readers that I have been and still am a huge fan of Kris Gethin. I am not accusing him of being on steroids, having a poor training philosophy or intentionally misleading anyone in the 12-Week Muscle Building Trainer. I honestly believe and others pressured him to create and perform this program and he had neither the right amount of time nor an adequate schedule to do it as well as it could and should have been done. He admitted on Day 1 of this program “Today was my first real workout in 4 months.” I only read a few of the daily diary entries, but when I saw that on Day 1 I couldn’t believe it. Seeing what he did the first week and in the weeks to come, particularly the pain and sickness he had to deal with, I really felt sorry for him.

I hope to review his other programs soon in hopes of seeing more promising programming, but I think his most recent one lead to a surgery on his rotator-cuff so I may end up finding out more of the same from this training program. If you have questions, comments, or suggestions for future reviews, please leave them below and thanks for reading.