Ever wonder why tennis players grunt when they serve? For the same reason Buakaw yells every time he strikes: power. . .


Most gyms teach beginners to breathe out when they throw a strike in order to not lose their breath. Getting into this habit is useful as it teaches the practitioner to pace themselves.

As one gets more advanced in one’s training, he or she will even be told by the trainers to yell or make some sort of sound every time they kick or punch on the pads and/or bags. This is the same reason tennis players make noises every time they smack the ball towards their opponent’s side: for breath and for power.

The effects of “grunting,” as it has been put by studies, have been reviewed scientifically numerous times. Mainly, the studies focus on the increased strength, power, or speed output when an athlete grunts vs when they don’t grunt. Grunting “improves muscle recruitment and force production,” as put by a study by O’Connell DG, et al. when looking at collegiate tennis players. This study found that those who grunted served the ball about five miles per hour faster, regardless of gender or what the athletes thought about grunting. Another study by Welch and Tschampl found “significant increases in forearm flexion force and grip force during shouting.”


All of this is great, but where is the application to Muay Thai and other martial arts? Luckily for us, a study has been published in February 2018 that examines the effect of grunting in a setting closer to home: kicking.

Scott Sinnett and company took a group of 20 people who had at least one year of MMA or Muay Thai training, with some people even having had professional fights. During the experiment, each person kicked a 100-pound heavy bag 15 minutes after completing an one-hour Muay Thai or MMA class. Specifically, they kicked the bag with their power side only five times, each time as hard as they could, with a 30 second break between each set. (They were allowed to rest longer if they felt tired, but none of the participants did.)

The researchers measured the force generated with an accelerometer. This was repeated a week later under the same conditions but those who grunted were told not to grunt, and those who didn’t grunt were told to grunt.

As predicted, more force was generated with the kicks when the participants grunted… 9% to be exact! But wait, that’s not all they found.


The second part of this study looked at how grunt is also distracting. They took participants with no prior martial arts experience, and with normal hearing and vision. These participants watched clips of someone throwing a kick, either with the grunt sound or without the grunt sound. They then had to notate what direction the kick was going in (up or down). Their answers as well as how fast they put down an answer (via pressing a key) was recorded.

Results? They found that with the grunt noises, the participants took a longer time to decide which direction the kick was going in. The participants also tended to be wrong about which direction the kick was going in when there was a grunt.

Science has spoken – start working on your yells and grunts at the gym and eventually start working them in when you compete. Adding greater power and a distracting element to your strikes can be an ultra-deadly combination.

Sean “Muay Thai Guy” Fagan presents

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Angela Chang
Plant-based fighter, foodie, and aspiring physical therapist. Angela is currently living in Bangkok and training full time.

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