The Roundhouse Kick in Six Systems — Why the Same Kick Looks Six Different Ways

Overview

Few questions escalate a martial arts forum faster than this one: whose roundhouse kick is best? The Thai kick with the shin? The chambered dollyo chagi of Taekwondo? The savate fouetté, stabbing through a tight guard with the toe of a boot?

The question is badly posed — and that is the interesting part. A kick is not an isolated movement you either perform correctly or incorrectly. It is the solution to an optimisation problem, and the problem is set by the rule set. A system that allows you to catch a leg and throw produces a different kick than one that does not. Fighters who wear shoes kick differently from fighters who fight barefoot. A sport that forbids punching to the head will inevitably grow a leg that goes there.

This article places six systems side by side — Muay Thai, Kyokushin karate, Taekwondo, savate, sanda and capoeira — and treats each as what it is: a coherent answer to a particular fighting situation. The evidence comes from two directions: the 3D motion analysis that has existed for cross-system comparison since 2017, and the competition rules from which the technical decisions can be derived.

One result up front, because it surprises most readers: in the only controlled measurement of impact forces across three systems, there was no statistically demonstrable difference between Muay Thai, karate and Taekwondo.

What the Data Shows

The most solid source for direct comparison is a study by Colin J. Gavagan and Mark G. L. Sayers, published in 2017 in PLoS ONE (12(8): e0182645). It remains the only work to have measured experts from three systems against each other under identical laboratory conditions.

Setup: 24 advanced practitioners, eight per discipline, each with at least five years of training and high competitive ranking. Lower-limb 3D kinematics were captured with a nine-camera infra-red system at 500 Hz, impact force with a strain gauge at 1000 Hz. The target pad was positioned at the height of the mastoid process — that is, head height. The movement was broken into four phases: preparation, chamber, extension, recoil.

The Measurements

Measure	Muay Thai	Karate	Taekwondo
Execution time	1.02 ± 0.15 s	no sig. difference	1.54 ± 0.52 s
Max. knee extension velocity	−706 ± 200 °/s	−947 ± 94 °/s	−943 ± 106 °/s
Vertical centre-of-mass velocity	1.24 ± 0.15 m/s	0.78 ± 0.24 m/s	0.93 ± 0.19 m/s
Impact force	1400 ± 419 N	1211 ± 219 N	1547 ± 530 N

Statistically supported: Muay Thai’s shorter execution time versus Taekwondo (P = 0.028), Muay Thai’s slower knee extension versus karate (P = 0.010) and Taekwondo (P = 0.011), and Muay Thai’s markedly greater centre-of-mass movement (P = 0.001 and P = 0.02 respectively).

Not supported: the difference in force. P = 0.281. The standard deviations are wider than the gaps between the means.

What Follows — and What Does Not

Two widespread claims do not survive this measurement.

“The Thai kick is slower but stronger.” Muay Thai’s execution time was the shortest, not the longest. What is slower is the knee extension — and that is not a deficiency but the design principle: Muay Thai does not accelerate the shank against the thigh, it rotates the entire body. The roughly 1.5× higher centre-of-mass velocity compared to karate is precisely that difference expressed in numbers.

“Taekwondo kicks are weaker.” The highest mean impact force belonged to Taekwondo (1547 N). It is not significant — but anyone who wants to turn that number against Taekwondo has to accept that it points the other way.

Three caveats belong with this, otherwise the study quickly becomes an argument it cannot carry:

Eight people per group. At this sample size a difference has to be very large to reach significance. “Not demonstrated” is not “not present.”
Measured at head height. That is Taekwondo’s showcase and the exception in Muay Thai, whose core weapons are the mid and low kick. The setup structurally favours systems specialising in high kicks.
Force is not damage. A strain gauge measures peak force in newtons. What destroys a leg is impulse — force over time — and that is systematically higher for a heavy, barely-yielding mass like the shin than for a fast instep, even at equal peak force.

In short: the study does not refute the simple “heavy versus fast” formula, but it shows the matter is considerably more complicated than tribal loyalty would have it.

The Six Systems Side by Side

System	Name	Striking surface	Chamber	Hip action	After the kick	Driven by
Muay Thai	tae wiang	shin	none to minimal	full rotation, centre of mass drops in	rotation carries through, sometimes a full 360°	clinch legal, shins conditioned, scoring rewards visible effect
Kyokushin	mawashi geri / gedan mawashi geri	instep and shin	moderate	strong rotation, weight sinks into target	hold the stance, follow up	full contact without head punches, no grabbing, barefoot
Taekwondo	dollyo chagi	instep, ball of foot	steep, knee at hip height	fast opening, torso leans back	immediate re-chamber	electronic scoring, head strikes heavily weighted, no grabbing
Savate	fouetté	toe of shoe, sole	pronounced, fencer-like	controlled, upright posture	retreat to range	shoes mandatory, shin and knee strikes forbidden
Sanda	bian tui	shin and instep	moderate, variable	rotation, but abortable	fastest recovery of the six	leg catches and throws score highly, platform pushes score
Capoeira	martelo, armada, meia lua de compasso	instep, heel, outer edge of foot	out of the ginga, often none	full body rotation, often with hands on the floor	transition into the next movement	play in the roda, evasion as an integral part

Muay Thai — Rotation Instead of Extension

The Thai kick is the only one of the six that deliberately abandons the knee extension. The leg is not snapped like a whip but swung like a bat: the support foot pivots on the ball through 90 degrees and beyond, the hip turns all the way through, and the arm on the kicking side is thrown down and back to generate the counter-torque. The knee remains slightly bent at impact.

This is exactly what the Gavagan study measures: the slowest knee extension, the greatest centre-of-mass movement. The energy does not come from the leg but from a torso rotating about its own axis and dropping as it goes.

The price is commitment. A fully committed Thai kick cannot be aborted. If it misses, the body turns past the target — in the extreme, a full 360 degrees. In Muay Thai that is a calculated risk: the clinch is legal, and a caught leg leads to control but not to a fight-deciding throw.

Shin as striking surface. The tibia has almost no soft-tissue padding and is the hardest structure that can be moved at high speed. A 2026 review in Healthcare on kicking mechanics and injury risk (14(4): 430, synthesising 23 studies) states the trade-off plainly: shin contact maximises momentum transfer but carries elevated risk of tibial contusions, periosteal irritation and stress fractures. The conditioning Muay Thai answers this with is not folklore — it is the precondition for the weapon not damaging its bearer first.

Kyokushin — The Kick That Grew Out of a Rule Gap

Kyokushin forbids punching to the head and any grabbing, but permits full contact without protective gear. That combination produces a very specific fighting range: two fighters standing close together, neither able to punch the other in the head or hold on.

The logical answer is the gedan mawashi geri, the low roundhouse to the thigh. In Kyokushin it is what the jab is in boxing: the single most frequent technique, not intended as a finisher but as attrition. A thigh that has absorbed twenty low kicks stops carrying its owner — and the rules do not permit the recipient to catch the leg.

Mas Oyama’s execution relies less on speed-strength than on mass: strong hip rotation and a deliberate sinking of body weight into the target. The body and head are traditionally kicked with the instep, the thigh and ribs with the shin — one technique, two striking surfaces, selected by target.

Taekwondo — Built for the Scoreboard

The dollyo chagi is the counter-model to the Thai kick. The knee chambers steeply, roughly at hip height and in line with it, then the shank opens explosively. The torso leans back to gain reach and take the head out of the counter line. Immediately after contact the leg re-chambers.

The measured −943 °/s of knee extension velocity is the quantitative image of that construction. It is also the reason for the longer overall execution time of 1.54 s: chamber, extend and re-chamber are three phases where the Thai kick has one.

Why build it this way? Because the rule set pays for it. Under WT rules head strikes are worth a multiple of a body strike, punching to the head is forbidden, and grabbing and leg-catching are as well. A fighter who need not fear having a leg caught can use it high and often. And a fighter striking an electronic sensor is paid for precision and repeatability, not for destruction. Re-chambering — a luxury in full-contact fighting — is a core tactical advantage here: the second kick arrives without the foot touching the floor.

A detailed breakdown of the system is in Taekwondo Kicking Techniques.

Savate — Fencing With the Feet

Savate is the only one of the six fought in shoes — and the only one that explicitly forbids shin and knee strikes. Contact may be made with the foot alone: specifically the toe, sole or edge of the shoe.

That single rule determines the entire technique. When the striking surface is a hard shoe toe of a few square centimetres, precision matters more than mass. The fouetté is accordingly a whipping kick out of the knee that stabs rather than swings — placed into the gaps of a closed guard rather than through it. The posture is upright, the range work bouncing, and both the terminology and the movement vocabulary are closer to fencing than to kickboxing. Savate recognises the fouetté at three heights: bas (low), médian (middle) and haut (high).

Practitioners coming from a shin-based system routinely underestimate how unpleasant a shoe is. The same energy over a tenth of the area produces many times the pressure.

Sanda — The Kick That Has to Come Back

In sanda the opponent may catch your leg and throw you. A throw scores; so does putting the opponent off the platform (lei tai) while you stay standing. That sets the central design constraint: a kick that does not come back fast enough is not a weapon but an offer.

The sanda roundhouse resembles the Thai kick at first glance — shin and instep, hip rotation — but differs in one decisive respect: it is abortable. The rotation is not driven through unconditionally, the centre of mass stays controllable, and the leg returns by the shortest path. The stance is lighter and springier than in Muay Thai, because level changes and entries into the body clinch have to be expected at all times.

Often the kick in sanda is not intended as a finish at all but as an opening: it forces a reaction out of which the throw is set up. Anyone reading the sanda kick as merely a “weaker Thai kick” has misunderstood its job.

Capoeira — Kicks From a Different Logic

Capoeira does not fit this series as a variant of the same tool; it is its own category. There is no fixed fighting stance from which the kick starts. Everything emerges from the ginga, the swaying base movement that continuously shifts weight and never stands still.

The closest relative of the roundhouse is the martelo — hammer kick, delivered with the instep. More characteristic, though, are the rotational kicks:

Armada (also meia lua de costas): a fast 360-degree turn, striking with the outer edge of the foot. The power comes entirely from the torque the body builds during rotation.
Meia lua de compasso (rabo de arraia): the best-known movement in all of capoeira. The body lowers, one or both hands go to the floor, the support leg becomes the centre of a compass, and the kicking leg sweeps a wide arc to strike with the heel. It is simultaneously an evasion and an attack — the practitioner watches the opponent from under their own arm as it goes.

The decisive difference from the other five systems is context. In the roda one plays; one does not knock out. A kick that lands has often already missed its point: the aim is to force the other to move and to make the opening visible. Evasion and attack are therefore not two phases here but one.

The Three Adjustment Screws

Across all six systems the differences reduce to three decisions. The 2026 Healthcare review identifies exactly those three as the technical determinants of both effect and injury risk.

1. The Support Leg

Does it pivot or not? A fully pivoted support leg frees the hip and allows full rotation — while loading rotational stress onto your own knee. The review names cruciate ligament and meniscus injuries as the associated risk. A non-pivoting support leg is more stable but transfers less.

Muay Thai and capoeira pivot maximally, savate and Taekwondo considerably less, sanda deliberately holds the middle.

2. The Hip

Pelvic angular velocity is the single strongest factor for effect — via the proximal-to-distal sequence, the transfer of energy from the large, slow mass at the centre to the small, fast one at the end. Gavagan and Sayers found similar maximum pelvic rotation velocities across all three groups studied. The difference lies not in how fast the hip turns but in what happens next: Muay Thai lets the rotation run on, Taekwondo adds knee extension on top.

3. The Striking Surface

Here the trade-off is sharpest:

Surface	Advantage	Risk	Typical of
Shin	maximum momentum transfer	tibial contusion, stress fracture, periosteal irritation	Muay Thai, MMA, sanda
Instep	higher velocity, greater reach	metatarsal fracture, ankle injury	Taekwondo, karate
Ball / edge of foot	precision, small contact area	toe and capsule injuries	Taekwondo, capoeira
Shoe	high pressure at low mass	comparatively low for the kicker	savate

Competition injury rates run, according to the review, at 6 to 12 injuries per 1000 athlete exposures in Taekwondo and karate; in MMA and Muay Thai, 39 per cent of athletes reported at least one health problem.

What This Means for Your Own Training

Striking surface and target belong together. The most common error in cross-style training is to adopt the movement and forget the striking surface. A Thai kick thrown with the instep into an elbow breaks the metatarsal. A fouetté thrown with the shin is simply illegal in savate.

Learning the rotation means learning the conditioning with it. Shin training is not an ingredient but a precondition. Bone adaptation under Wolff’s law takes months to years and requires recovery phases — the mechanism is the same one behind Shaolin conditioning.

Abortability is a skill in its own right. Anyone moving into a rule set with leg catches (sanda, MMA, self-defence) has to relearn the kick, not merely adapt it. Recovery is simply not trained in Muay Thai, because there it has no value.

The chamber is a timing tool, not a beginner’s mistake. The steep Taekwondo chamber conceals until the last instant whether a high or a low kick is coming. That is the tactical gain that pays for the longer execution time.

Common Fallacies

“System X has the strongest kick.” The only controlled cross-system measurement found no significant difference in force. Anyone saying this sentence usually means a particular target, a particular range and a particular striking surface — in which case it may be true, but only there.

“Traditional chambered kicks are inefficient.” They are optimised for a different criterion: concealment, repeatability, recoverability. In a rule set without leg catches and with high scoring for head strikes, that is the superior solution.

“You can build the best version out of all of them.” Only up to a point. The decisions hang together: full rotation presupposes shin conditioning, shin conditioning presupposes barefoot fighting, barefoot fighting rules out the savate fouetté. Anyone mixing has to know which rule set applies in the end.

“Capoeira kicks don’t work.” They work for what they were built to do. The meia lua de compasso is one of the most powerful rotational movements in the entire martial arts spectrum — it simply is not designed to appear out of a static fighting stance at boxing range.

Sources and Further Reading

Gavagan, C. J. & Sayers, M. G. L. (2017): A biomechanical analysis of the roundhouse kicking technique of expert practitioners: A comparison between the martial arts disciplines of Muay Thai, Karate, and Taekwondo. PLoS ONE 12(8): e0182645 — the only controlled 3D measurement across three systems, open access
Mechanical Efficiency and Injury Risk in Leg Kicks Across Combat Sports: A Narrative Review of Stance, Hip Rotation, and Striking Surface Effects. Healthcare 14(4): 430, 2026 — a synthesis of 23 studies from 2000–2025 on the relationship between effect and injury risk
Choi Hong Hi: Encyclopedia of Taekwon-Do — the primary source on ITF kicking systematics
Mas Oyama: This Is Karate — Oyama’s own account of Kyokushin mechanics