Static stretching before training quietly weakens you. Dynamic stretching doesn't. The science on what to do before, during, and after a kickboxing or Muay Thai session.
FightFlow Team
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August 25, 2026
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11 min read
Training safety
This article is for education, not diagnosis. If symptoms show up after head contact, stop training and speak with a licensed medical professional.
Walk into almost any Muay Thai or kickboxing gym fifteen minutes before class and you'll see the same picture. Someone is sitting on the floor pulling their toes toward their face. Someone else is doing the splits, or trying to, holding it and breathing through it like it's medicine. After class, the same fighters are out the door before the sweat dries.
Both halves of that picture are upside down. What the research says you should do before training is roughly what most gyms do after, and the part you actually skip is the part that builds the flexibility you're chasing in the first place.
This is a long topic with a lot of confidently bad advice in circulation, so it's worth going through it carefully.
Three things tend to get lumped together under the same word:
They affect the body in different ways. Treating them as the same thing is where most of the bad warm-up advice starts.
The cleanest summary of how each one affects what happens next is a 2011 review by Behm and Chaouachi in the European Journal of Applied Physiology that pulled together more than a hundred studies. The headline numbers from that review:
Small to moderate effects, but the direction is consistent across decades of research: holding a long static stretch right before you ask the muscle to produce force quickly tends to make the muscle produce less force, less quickly. PNF is worse on this score. Dynamic stretching is the only one that nudges performance the right way.
Newer meta-analyses keep landing in the same place. A 2023 net-meta-analysis on warm-up methods for lower-limb explosive strength found static stretching reduced vertical jump and sprint performance, while dynamic stretching improved both. The most reliable dose of dynamic stretching in those studies was around 7 to 10 minutes, and a separate review of jump and range-of-motion outcomes found that both static and dynamic stretching improved range of motion equally, so you don't need the static holds to be ready to kick high. Dynamic work gets you the range without the force cost.
For a sport whose punches land in 50–250 milliseconds and whose kicks finish inside about 300 milliseconds (the numbers from the research on where striking power comes from), losing a few percent of fast-force production right before sparring is not a trade you want to make.
The mechanism, roughly: a long passive stretch reduces musculotendinous stiffness and dials down neural drive to the muscle. A more compliant, less neurally primed unit is worse at the one thing a strike needs, which is turning on hard and fast. The mechanical and neural pieces probably both contribute; the practical effect is the same either way.
The duration of the stretch matters a lot, and this is where the nuance lives.
A 2024 systematic review with multi-level meta-analysis in Sports Medicine - Open worked through the threshold question directly. Holds of less than 60 seconds per muscle group produced only trivial deficits, around 1 to 2%. Holds at or above 60 seconds per muscle started showing high-magnitude strength losses. So a single 30-second hamstring stretch before pads is not going to cost you a fight. A ten-minute splits session before sparring well might.
If you do want to keep a few short static holds in your warm-up (say, on a chronically tight muscle that won't move otherwise), keep each hold under a minute, and follow it with dynamic and sport-specific work so the nervous system gets re-primed before you start throwing.
For decades the case for static stretching wasn't really about performance. It was about not getting hurt. That case has weakened a lot under careful examination.
The most-cited meta-analysis here is Lauersen, Bertelsen and Andersen in the British Journal of Sports Medicine in 2014, pooling 25 randomised trials and roughly 26,000 athletes. Strength training reduced sports injuries to less than a third of baseline. Overuse injuries fell by close to half. Proprioception training helped. Stretching, isolated as its own intervention, showed no clear effect on injury rates.
That's the headline most coaches now go with, and they're right to. But it's not the whole story. A more recent meta-analysis (Sport Sciences for Health, 2024) looked specifically at muscle injuries (strains, tears, the soft-tissue stuff) and found static stretching did reduce them (odds ratio 0.37, meaning roughly a 63% lower odds in the stretching groups). It did not reduce tendon injuries, and it didn't reduce all-cause injury. So stretching is not useless on the injury column; it's just narrower than the gym lore had it.
This matches what shows up in the combat-sports injury literature. The most common injury in Muay Thai gyms is a soft-tissue strain or sprain, mostly in the legs, and a chunk of it traces back to skipping or rushing the warm-up. The fix there is a proper moving warm-up, plus the strength and pacing work that keeps cold legs from being asked to move like warm ones. Longer splits holds won't do it.
If static stretching is a poor pre-training tool and a thin injury-prevention tool, what is it good for? Flexibility. Real, kick-the-head-of-a-tall-opponent flexibility. But only when you treat it like training, not a five-minute pre-class ritual.
A 2025 systematic review and meta-regression in Sports Medicine dug into the mechanism. Chronic static stretching does increase range of motion, and most of the gain comes through two things: a real reduction in passive muscle stiffness, and an increase in stretch tolerance (the nervous system letting you go further into a stretch before it tells the muscle to push back). The change in actual muscle architecture (fascicle length) is small to nil at the doses most people use.
Translation: improving your splits or your head kick is partly tissue and partly the brain learning that the position is safe. Both need consistent exposure.
The consistent dose in that literature is roughly:
That is a lot more stretching than the five minutes most fighters do before class. And critically, none of it has to happen pre-training. Done after training, on a rest day, or as its own session at home, it builds the flexibility without taxing the power you need on the mats.
If you stretch every day for fifteen years and never throw a single high kick on it, that work still pays off. If you stretch hard for ten minutes before sparring and skip the post-class flexibility work, you've inverted the dose and lost performance on both sides.
A biomechanical study comparing roundhouse kicks across Muay Thai, karate, and taekwondo practitioners found five variables that drive effective kicking across all three: pelvic axial rotation, hip abduction velocity, hip flexion velocity, knee extension velocity, and rapid center-of-mass displacement toward the target. The impact-force-to-foot-velocity correlation was moderate (r = 0.66), and an average professional Muay Thai roundhouse landed at about 1,400 N.
What that list says is that the limit on your kick is rarely raw arm-or-leg strength. It's how fast the hip can open and rotate, how cleanly the trunk can twist, and how far the leg can travel through that range. That's a hip-mobility problem and a stretch-tolerance problem more than a strength problem. The fighters whose head kicks land cleanly aren't necessarily stronger; they're moving more range, more freely.
So static stretching is genuinely worth doing for kickers. Just not in the ten minutes before you throw kicks.
The model strength coaches keep coming back to is Ian Jeffreys' RAMP protocol. It's just a structure: Raise, Activate, Mobilise, Potentiate, in that order, taking 10 to 15 minutes total. Mapped onto a kickboxing or Muay Thai session, it looks roughly like:
What's missing from that list, deliberately, is sitting and holding a static stretch. Save those for the cool-down, when the nervous system is already winding down and you're not about to ask the muscle to produce maximum force.
The same structure works for a solo session at home, just at smaller scale. The order is what matters.
A few things to keep in mind before treating any of this as gospel.
The acute-performance effects from static stretching are small to moderate on average, and they vary by who's doing it, how long they hold each stretch, and what they're being tested on. A trained fighter holding a 30-second hamstring stretch isn't suddenly throwing weak kicks. The case against pre-training static stretching is about direction and dose: wrong direction at long doses, not "never do this."
The chronic-flexibility numbers (4 minutes, 5x/week, 3+ weeks) are the dose that consistently shows results in research. Plenty of people get gains on less. The point is mainly that flexibility is a training quality with a dose-response curve, not something you absorb by stretching once in a while.
And the injury data is, like most combat-sport data, noisier than anyone wants. The cleanest finding remains the negative one: stretching alone doesn't prevent injury the way the old coaches said it did. Strength training does most of the heavy lifting there.
If you train Muay Thai or kickboxing and you want one usable rewrite of your warm-up routine, it's this:
Before training, dynamic for 7 to 10 minutes inside a 10–15 minute RAMP-style warm-up. Keep any static holds under 60 seconds and follow them with movement.
After training, when you're warm and the work is done, that's when you stretch for flexibility: longer holds, more time per muscle, with the head-kick height you actually want as the goal.
A few times a week, on or off the mats, treat flexibility like a real training block. Four minutes per target muscle, consistently, for at least three weeks before you decide whether it works.
Lift, eat, sleep. Most of the injury-prevention budget belongs there, not in your hamstrings.
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