There is a lot of speculation around whether or not Chris Hemsworth's transformation for Thor was natural, or if he did a steroid cycle during his prep for the film in 2009.
Chris Hemsworth purportedly gained between 20-25 pounds of muscle in 6 months to prepare for his role of Thor [R].
I do not believe it was a natural transformation, and I'm going to outline exactly what I think he took, as well as the dosages he used.
Natty Chris Hemsworth In “Home And Away” (2004-2007)
If you go back and look at Chris Hemsworth in “Home and Away,” you can see what his physique looked like naturally.
This athletic looking physique with about 15% body fat is pretty typical for a young man with a half decent metabolism.
Chris doesn't look like anything special here, and does not have much muscle on his frame.
This is what his physique looked like in 2007 at the tail end of his appearances in Home And Away.
Chris claimed that prior to Thor, he had never strictly weight trained with the intention of packing on muscle.
Natty Chris Hemsworth In “A Perfect Getaway” (2009)
A Perfect Getaway was filmed from March 31st, 2008 – May, 2008 we can see that Chris packed on a little bit of mass for this role.
While he isn't as big as he became for Thor in 2010, we can start to see his genetic shape as he packs on some lean tissue.
Chris was likely still natural here, but may have started weight training by this point.
Natty Chris Hemsworth In “The Cabin in the Woods” (2011)
The Cabin in the Woods is the best glimpse we get into a “before” of Chris before filming Thor as it was filmed from March 9th, 2009 – May 29th, 2009.
In this movie we can see exactly what Chris' physique looked like almost exactly 6 months before filming for Thor began in 2010.
Chris looks slightly leaner in this movie than he did in A Perfect Getaway, but does not look like he packed on any additional muscle.
At this point, Chris already secured the role as Thor and knew how much muscle he had to pack on over the remaining months in the year, so it is likely that he had already started resistance training in some capacity during the time frame this movie was filmed in.
I believe Chris was still natural in The Cabin in the Woods.
Gaining 20-25 Pounds Of Muscle In 6 Months For His Role In Thor (2011)
After filming for The Cabin in the Woods finished at the end of May in 2009, Chris had about 7 and a half months to pack on as much muscle as possible for Thor.
Thor was filmed from January 11th, 2010 – May 6th, 2010, as well as October 10th, 2010 – October 31st, 2010.
Chris claims he didn't lift weights prior to preparing for Thor.
Chris didn't show his physique very much in the movie Red Dawn, which was filmed between September 8th, 2009 – December 11th, 2009, so the physique we see during The Cabin in the Woods serves as our best benchmark for a before and after transformation.
Over 6 months following the filming of The Cabin in the Woods, Chris added 20-25 pounds of fat-free mass to his frame, and completely transformed his physique.
Even as an untrained natural newbie with amazing genetics, it is nearly impossible to gain 20-25 pounds of muscle in 6 months.
With that being said, I do not believe that Chris actually gained 20-25 pounds of pure muscle.
It was probably closer to 15 pounds, with an additional 5-10 pounds of temporary water and nitrogen retention, and with a portion of that last 10 pounds also being fat gain.
He's not much leaner in Thor compared to his last role, if at all.
Considering that, some might start to consider that this transformation may be possible naturally.
It is debateable, but I believe that the nail in the coffin for Chris is when you reference what his physique looks like between his appearances as Thor.
He is clearly not capable of sustaining that level of mass year-round.
It really isn't that hard to maintain muscle mass on steroids.
The only exception to this are bodybuilders with such an unnatural amount of muscle that they need to be on a low dose blast year round to maintain their size, but obviously this does not apply to Chris Hemsworth, myself, or likely you either.
Clearly he eats at least moderately clean year round, otherwise he wouldn't stay as lean as he does.
Considering that, he would literally have to stop working out entirely to lose the amount of muscle he does between his Thor appearances to lose that muscle if he stayed on TRT year round.
The rate at which he loses the majority of his size between movies is a flagship indicator of steroid cycling.
When you compare Chris Hemsworth's physique in different movies, it is pretty clear that there is a night and day difference in muscle mass in his Thor appearances relative to other roles.
Even including roles where he has gotten very lean, like Rush in 2013.
From what I can see, Chris Hemsworth's physique peaked in size for the first Thor movie, and during his Thor prep in 2009 is likely when he used the highest dosed steroid cycle that he has ever used for the entirety of his career.
Maintaining Muscle For His Role In “The Avengers” (2012)
The Avengers was filmed from April 25th, 2011 – September 4th, 2011.
Chris appears to be a bit smaller in this role than he was in the first Thor movie, but clearly put in the work to attempt to replicate that look again for this movie.
Losing Muscle For His Role In “Rush” (2013)
Rush was filmed early to mid-2012 [R].
This was less than a year after The Avengers was filmed.
This is first role we can see that Chris clearly dropped a significant amount of his Thor mass for.
Chris appears to have 10-15 pounds less fat-free mass in Rush, but actually looks a bit leaner than he did in Thor.
Whether he was natural for this role or not is tough to say, as he is still much more muscular than he was in Home And Away.
Can you attribute that to just training less and eating less?
However, the fact that Chris stated how difficult it was to lose muscle mass for the role is also a red flag that implies that he was unnatural when he filmed this movie as well.
If you go from being enhanced to natural, the muscle will fall off your body with ease during calorie restriction.
You would also not stay as lean as you were when you were enhanced.
The fact that Chris Hemsworth's physique appeared to have lost muscle and a bit of extra fat, and the difficulty he stated he had with losing that muscle implies that he was still on a steroid cycle during his preparation for this role.
The dosage was probably much lower though, or he could have had residual amounts of androgens still clearing his system from his previous showing as Thor in The Avengers.
It is not hard at all to lose muscle when you are natural and deprive yourself of calories.
Gaining Muscle Back For His Role In “Thor: The Dark World” (2013)
Thor: The Dark World was filmed from September 10th, 2012 – December 14th, 2012.
Within just a few months of filming Rush, Chris packed on a decent amount of size for the second Thor movie again.
Losing Muscle For His Role In “Blackhat” (2015)
Blackhat was filmed in May, 2013.
Chris lost the mass he had in the second Thor movie within a few months to play this role, and I believe he likely accomplished that just by going off cycle.
Losing Muscle For His Role In “In The Heart Of The Sea” (2015)
In The Heart Of The Sea was filmed in September, 2013.
This was the most shocking transformation to the public, as a viral picture taken by Chris started circulating which showed him looking emaciated for his role in the movie.
I believe the hype around this transformation was a bit exaggerated, as he clearly still has a fair bit of muscle on his frame in the after picture.
He's still more muscular and leaner than he was in Home And Away, but the way he's posing and the lighting is unflattering on purpose to make the transformation look as dramatic as possible.
With that being said, he clearly lost size for Blackhat, and took the weight loss to another level for a short stint when filming In The Heart Of The Sea a few months later in September of the same year.
Gaining Muscle Back For His Role In “Avengers: Age of Ultron” (2015)
Filming for Avengers: Age Of Ultron occurred between February 11th, 2014 – August 6th, 2014.
Chris went from looking like an emaciated version of himself to looking muscle bound for Thor again in only 4-5 months.
Is he as big as he was in 2009 when he prepared to film the first Thor movie?
No, I don't think so, but he's definitely not far off.
The lighting is poor in this clip, so it is hard to say for certain, but he obviously packed on the majority of the size again in a short time span.
With the muscle memory Chris developed from his previous bulking phases and the state of calorie deprivation he put his body in, the rebound back to a muscle bound Thor was probably fairly easy for him during those 4-5 months.
What he used to prepare for the first Thor movie, he likely used again to prepare for this role at the tail end of 2013 before filming started in 2014.
Regardless of how you much you want to may want to believe a transformation like this is possible naturally, 99.9% of humans can't stay the same level of body fat and gain 20 pounds, lose 20 pounds, gain 20 pounds, lose 20 pounds of lean tissue back and forth like this.
The amount Chris fluctuates between roles and between his showings as Thor is very indicative of exogenous hormone use in my opinion.
Losing Muscle For His Role In “Ghostbusters” (2016)
After the 2015 Avengers movie, Chris downsized again and we can see this in his 2016 roles that were filmed in 2015, as well as in his interviews in 2016.
Gaining Muscle Back For His Role In “Thor: Ragnarok” (2017)
Filming for Thor: Ragnarok occurred July 4th, 2016 – October 28th, 2016 and in July, 2017.
This is probably the leanest Chris has gotten for any appearance as Thor, although I believe he was still a bit bigger in the first Thor movie.
He's leaner and dryer than he was in the first Thor movie, but with what appears to be 5-10 pounds less overall mass.
With that being said, this is yet another example of Chris transforming his body in a short time span to play Thor.
As Chris gets deeper into his 30's, the need for exogenous anabolic support becomes even more necessary to support these quick transformations, and is just another red flag that his preparation for his appearances as Thor are likely completed with hormonal assistance.
Chris Hemsworth's Steroid Cycle
Which Steroids I Think He Used
Based on the fact that Chris' biggest physique was in the first Thor movie, as well as factoring in that it was the first time Chris gained that size (it is harder to gain muscle the first time around due to muscle memory), I'm going to elaborate on what I believe he took to prepare for that movie in particular.
Chris' Hemsworth trainer said that he gained 20 to 25 pounds of muscle in 6 months.
That number could be inflated, and I think that it is more likely that Chris gained 20 to 25 pounds of fat-free mass, not dry tissue.
That would include temporary water retention, nitrogen and blood volume.
With that being said, the amount of muscle he gained in the given time frame was still very unnatural.
My best guess is that Hemsworth just took Testosterone to prepare for his first appearance as Thor.
It has the best safety profile and clinical efficacy out of any human approved steroid, and it is just a no brainer go to for a first steroid cycle.
In addition to that, he's sporting a very watery and full look in Thor.
He looked dryer in both Rush and Thor: Ragnarok than he did in the first Thor movie.
He doesn't have a crazy androgenic dryness to his physique either.
That full look is advantageous for appearing as big as possible for Thor though, despite having a bit more intracellular water than would be ideal from a bodybuilding perspective.
With the goal being as much fullness and size as possible while maintaining a reasonably lean level of body fat, it is very likely that Testosterone was the compound of choice for this transformation.
Looking as inflated as possible was the goal, and I believe he accomplished that.
I doubt he stacked anything on top of that because it wouldn't have been necessary to achieve these results.
A supraphysiological dose of Testosterone was more than sufficient.
To determine what dose of Testosterone Hemsworth used for his transformation, we can extrapolate data from clinical studies conducted on healthy young men to get a better idea of what he likely took to achieve the results he did in the time frame given.
Testosterone Dose-Response In Healthy Young Men
The Study Parameters
This study evaluated the results of weekly administrations of Testosterone at dosages of 25 mg, 50 mg, 125 mg, 300 mg, and 600 mg for 20 weeks in healthy young men [R].
Keep in mind when you interpret these results that fat-free mass also accounts for water, it is not just pure muscle tissue.
As you would expect, the higher the Testosterone dose used, the more aromatization occurs.
The more aromatization there is occurring in the body, the more water retention will also occur, which is going to play a role here too, as it did in Chris Hemsworth's transformation.
- Nutritional intake was controlled
- The exercise regimen was controlled
- The dose was controlled
- Used pharmaceutical-grade testosterone
Energy and protein intakes were standardized at 16.33 calories per pound per day, and 0.544 grams per pound per day.
Participants were instructed to not partake in strength training or moderate-to-heavy endurance exercise during the study.
The only thing that differed between the participants was the dosage of Testosterone administered.
By looking at the body composition analysis in this study we can see that there was an expected dose-dependent response in muscle accrual across all groups.
25 mg Testosterone per week caused a drop in muscle mass due to the fact that endogenous androgen production was suppressed in the young men due to the presence of exogenous androgens, and the exogenous androgen dosage was lower than what would normally be endogenously produced naturally.
With 50 mg Testosterone per week, they're about breaking even here.
125 mg Testosterone is where things start to get very supraphysiological in terms of dose-response and the literal androgen load in the body significantly exceeding what a healthy young man would produce naturally.
On average, a healthy young man produces between 3 to 10 milligrams of Testosterone per day naturally.
In the 300 mg Testosterone treated group, fat-free mass increased by 5.2 kilograms.
In the 600 mg Testosterone treated group, fat-free mass increased by 7.9 kilograms.
7.9 kilograms is just shy of 17.5 pounds.
That means that over the span of about 5 months, healthy young men were able to gain 17.5 pounds of fat-free mass using 600 mg of Testosterone with a subpar protein intake and without even doing any weight training.
Those 2 factors will significantly impair potential muscle accrual, and we can expect that someone eating an optimized diet for bodybuilding and training hard with progressive overload could expect fat-free mass gains likely in the 20-25+ pound range.
This is where we can extrapolate the data and draw it back to exactly what I believe Chris used, and the duration of his use.
What Dosages I Think Chris Hemsworth Used To Prepare For Thor
Based on the dose-response study I outlined above, we can see that healthy young men gained upwards of 17.5 pounds of fat-free mass over a 5 month time span without even adhering to a strict resistance training plan or eating an optimal amount of protein for hypertrophy.
Relating this back to Chris Hemsworth's body transformation, we already know he gained 20-25 pounds of fat-free mass over the course of 6 months.
He was eating a strict diet tailored for hypertrophy, as well as following a very intense bodybuilding regimen (or at least we can assume it was intense).
Factoring in Chris' strict adherence to a tailored diet and training protocol, I would assume that he likely took between 400 to 600 mg of Testosterone per week for the last 6 months in 2009 leading up to filming Thor in 2010.
Chris Hemsworth's physique was at his biggest in the first Thor movie, so that was likely the highest dosed steroid cycle he has ever used in his acting career to prepare for a role.
It was also the first time he had ever packed on that size, which further solidifies that he likely took the highest dose of steroids he has used over his entire career to prepare for this first appearance as Thor.
It is much easier to gain back lost muscle via muscle memory and previously accrued myonuclei than it is to gain fresh new muscle for the first time.