Watching aggressive videos can boost muscle strength

Athletes can train with heavier weights if they watch a video clip that stimulates the production of hormones like testosterone just before working out. English sports scientists write about it in Hormones and Behavior. Clips that show aggression work particularly well when it comes to building physical strength.

Testosterone and resistance training
The higher the concentration of biological testosterone in their blood, the more intensively bodybuilders or other strength athletes train. The concentration of hormones is not constant, but fluctuates. Testosterone levels rise, for example, as a result of looking at porn. Team members will produce more testosterone if they watch a recording of a previous victory. [Psychoneuroendocrinology. 2010 Apr;35(3):475-9.]

The researchers added these two facts together, and wondered whether strength athletes would reap more rewards if they trained after watching a video that would boost testosterone levels.

The researchers got twelve professional rugby players to do squats on six different occasions, and measured the weight with which the players could just manage three reps [3RM].

A quarter of an hour beforehand the subjects had watched a four-minute video. On one occasion they watched a clip from the TV show The Big Bang [Humorous], on another it was a news item on underfed children in Africa [Sad], a “clip featuring exotic dancing” [Erotic], a clip on an athlete’s training methods [Training] and lastly a compilation of rugby players interacting aggressively during matches [Aggressive].

During a control session the subjects sat in front of an empty screen [Control].

The sad and humorous clips did not have a statistically significant effect on the men’s performance. The erotic, aggressive and training clips did, and boosted the 3RM. Of the three clips the aggressive clip worked best.


The figure below shows the effect of the clips on the concentration of cortisol and testosterone in the subjects’ saliva. It was the aggressive and the training clips that boosted the secretion of these hormones the most.


The researchers have an important piece of advice for athletes and trainers who are thinking of experimenting after learning about the results of this study. Everyone reacts differently to video clips they stress.

“The video clip effect appears to be highly individual, even within a relatively homogenous population”, the researchers wrote. “Within the group results, some individuals were highly responsive to the entire emotional context, some with context-dependant responses, and others who had a minimal response to all visual stimuli.”

“These variances may be explained by individual differences that exist on a number of levels (e.g. hormonal, life experiences, psychosocial, personality).”

“We contend that, at the elite athlete level, examination of individual hormonal responses and effects may yield more relevant results than group considerations.”

Changes in salivary testosterone concentrations and subsequent voluntary squat performance following the presentation of short video clips


Previous studies have shown that visual images can produce rapid changes in testosterone concentrations. We explored the acute effects of video clips on salivary testosterone and cortisol concentrations and subsequent voluntary squat performance in highly trained male athletes (n = 12). Saliva samples were collected on 6 occasions immediately before and 15 min after watching a brief video clip (approximately 4 min in duration) on a computer screen. The watching of a sad, erotic, aggressive, training motivational, humorous or a neutral control clip was randomised. Subjects then performed a squat workout aimed at producing a 3 repetition maximum (3RM) lift. Significant (P < 0.001) relative (%) increases in testosterone concentrations were noted with watching the erotic, humorous, aggressive and training videos (versus control and sad), with testosterone decreasing significantly (versus control) after the sad clip. The aggressive video also produced an elevated cortisol response (% change) and more so than the control and humorous videos (P < 0.001). A significant (P < 0.003) improvement in 3RM performance was noted after the erotic, aggressive and training clips (versus control). A strong within-individual correlation (mean r = 0.85) was also noted between the relative changes in testosterone and the 3RM squats across all video sessions (P < 0.001). In conclusion, different video clips were associated with different changes in salivary free hormone concentrations and the relative changes in testosterone closely mapped 3RM squat performance in a group of highly trained males. Thus, speculatively, using short video presentations in the pre-workout environment offers an opportunity for understanding the outcomes of hormonal change, athlete behaviour and subsequent voluntary performance. Source: