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Back or Knee Pain? Uh-Oh, You May Have ‘Dead Butt Syndrome’

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Back or Knee Pain? Uh-Oh, You May Have ‘Dead Butt Syndrome’

Nov. 13, 2025 – You won’t find any support groups for dead butt syndrome, aka gluteal amnesia, sleepy glutes, flabby butt, longback, or, for King of the Hill fans, diminished gluteal syndrome.

“They all mean sort of the same thing: weak gluteal muscles,” said Dean Somerset, a clinical exercise physiologist based in Edmonton, Alberta, Canada, and co-author of Rock Solid Resilience.

If you guessed that small, weak, and poorly functioning glutes are often the result of too much sitting and too little exercise, you wouldn’t be wrong, according to Somerset.

Meanwhile, Los Angeles-based physical therapist Chad Waterbury, DPT, has seen it in healthy, fit, active clients, including a few professional athletes. “When we do exercises like squats, deadlifts, lunges, it’s very easy for other muscles to do the work you want the glutes to do,” Waterbury said

In both populations, the glutes stop doing what they should, and that can lead to serious problems up and down the movement chain. 

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If misfiring glutes force the lower-back muscles to take on loads they’re not meant to handle, the result can be years of back pain. And if the glutes fail to perform their stabilizing role in exercise and sports, you could be looking at chronically sore knees, or perhaps even an ACL injury. 

That means the Venn diagram of dead butt sufferers includes people who sit a lot, active people, those with back pain, and those with knee pain. All those people, all that overlap, all those butts.

Is your butt among them?

Putting a Name to the Pain

Stuart McGill, PhD, coined the term “gluteal amnesia” to describe what happens when pain causes people to change how they move.

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“In people with longer-term pain, the pattern of nerve pulses distributed to the muscles can become corrupted,” he explained. “The pain kicks off an inhibition pathway, so the brain finds a different way to do the same basic thing.” 

That, in turn, changes the way muscles like the hamstrings contribute to the movement.

“But even when the pain has gone away, the brain often remembers the painful pattern,” McGill said. Which means it also forgets how to use the muscles appropriately and efficiently. 

McGill, a distinguished professor emeritus at the University of Waterloo and author of Back Mechanic, showed how the process works in a 2013 study. In that paper, he and his co-authors used “gluteal amnesia” and “gluteal inhibition” interchangeably. 

The latter term is probably more appropriate, given that some people hear the former and think it implies gluteal dementia, as if the misplaced movement patterns can never be restored.

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Fortunately for the gluteally deficient among us, they can. Just not in the way most of us would assume. 

Hips, Femur, Knees, and Woes

While McGill was teasing out the connection between gluteal amnesia and back pain, Christopher Powers, PT, PhD, was looking at how abnormal glute activation patterns could lead to knee problems. 

“The gluteal muscles control the femur,” he explained. “The femur’s half the knee joint. So by definition, the gluteal muscles control half the knee.”

Powers is associate chair of the Division of Biokinesiology and Physical Therapy at the University of Southern California, where he studies the root causes of the lower-body injuries. And he addresses a lot of them with the athletes and patients he sees at the Movement Performance Institute in Los Angeles, which he founded and owns. 

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His research has shown that a key function of the gluteal muscles is to prevent the femur from rolling inward during sports, exercise, or everyday physical activities. 

“Once you stop using the muscle, the brain kind of forgets about it,” Powers said. “You lose the neural connectivity.”

And if the brain forgets how to stabilize the femur, just about anything you do, from walking to landing after a jump, will put stress on your knee joints. 

How to Know if Your Butt is Dead or Dying

Remember, given that sedentary and active people have this issue, aside from chronic knee or back pain, you may not be able to tell if your glutes are firing properly or improperly. 

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Waterbury recommends this self-test: the single-leg glute bridge. 

Lie on your back with one leg lifted out straight and the other leg bent at a 45-degree angle with the foot flat on the floor. Your thighs should be parallel. Raise your butt so your thighs and torso form a straight line. 

Hold that position for 20 seconds (or as long as you can up to 20), while paying close attention to which muscles you feel are working the hardest. Lower your hips and repeat with the other leg. 

If you felt the strongest contraction in your hamstrings or lower back, instead of your glutes, you need to improve your gluteal activation. Also, muscle imbalances are common, so it’s also not unusual for you to feel weaker in one glute or the other.

Two of Powers’s studies offer encouraging news for those whose glutes have lost their way. 

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The first, published in 2016, found that a week of glute-activation exercises increased neural drive to the muscles. 

A follow-up, published in 2022, found that the same exercise protocol made the muscles more able to stabilize the femur.   

So let’s take a look at the program.

Wake Up, Dead Butt

Powers’s program includes just three exercises, all of which may look familiar: clamshell, side-lying hip abduction, and fire hydrant. 

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Even if you haven’t used the exercises in your own routines, you’ve probably seen other people doing variations of them. 

Here’s the catch: To do the program correctly, you have to forget what you’ve done or seen. 

Instead of doing sets and reps, you’ll hold each position for up to a minute at a time. And you’ll need to do the program almost every day. 

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“When you do reps – up and down, up and down – the focus tends to be on the movement,” Powers said. Isometric holds like these require something else: intense concentration on squeezing the muscle in one continuous position.

That extended muscle activation allows the brain to reopen its channels of communication. If you follow the isometric holds with exercises that use the glutes, like squats or step-ups, you reinforce those neural signals.

To get the most out of the exercises, you’ll want to use a miniband positioned around your thighs, just above your knees. When you can hold a position for a full minute, use a more challenging band the next time. 

Here’s a closer look at each exercise. 

Clamshell

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Lie on your side with your legs together and your hips and knees bent 45 degrees. 

Lift your top knee straight up while keeping your feet in contact with each other. 

Feel the squeeze in your glutes and hold for up to a minute. Switch sides and repeat. 

Side-Lying Hip Abduction

 Lie on your side with your top leg straight and bottom leg bent at the knee about 45 degrees.

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Lift your top leg up and slightly back.

Feel the squeeze in your glutes and hold for up to a minute. Switch sides and repeat.

Fire Hydrant

To Powers, the fire hydrant is the best of the activation exercises. “If I were to pick one, I’d take it over the other two,” he said.

But it’s also the trickiest one to get right, since you’re asking your glutes to perform three functions, as you’ll see: 

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Kneel on all fours with your hips parallel to the floor and your hands shoulder-width apart.

Without shifting your hips, lift one leg up (hip abduction) and back (hip extension). Position your thigh so it’s neither perpendicular to your torso (straight out to the side) nor aligned with it (straight back), but instead about halfway between those two points. (It’s called “fire hydrant” because you’re mimicking a dog doing what a dog does to a fire hydrant.)

Now turn your thigh outward (external rotation) until you feel tension in the band. 

The goal isn’t to achieve any particular range of motion. It’s to reach a position you can hold while keeping your hips level with the floor.

Hold for up to a minute, switch sides, and repeat. 

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Restoring Your Seat of Power

People in Powers’s studies did three isometric holds of each exercise, with each leg, twice a day for seven consecutive days. 

But Waterbury, who studied under Powers at USC, uses a streamlined version of the program with clients, athletes, and patients. 

Start with these exercises:

  • Clamshell, 30 seconds per side
  • Side-lying hip abduction, 30 seconds per side
  • Fire hydrant, 30 seconds per side 

Do the exercises six days a week for four weeks, either on their own or as part of a warmup before a workout. “That’s plenty to get the glutes activated,” Waterbury said.

After four weeks, do the exercises three times a week, preferably before a strength workout that includes squats, deadlifts, lunges, or other movements that use your glutes in coordinated action with other lower-body muscles. 

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You can also do more advanced versions of the exercises, as Waterbury demonstrated in this video.

What matters most, he emphasized, is that you make these isometric holds a permanent part of your fitness routine.

“Too many things we do throughout the day make your glutes want to shut down again,” he said. 

Ultimately – and this is pretty good life wisdom – it’s a lot easier to keep your butt alive and well than it is to bring it back from the dead.

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“Forget living longer, exercise can make life easier right now”—a 72-year-old fitness influencer and marathon runner shares two accessible ways to start moving

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“Forget living longer, exercise can make life easier right now”—a 72-year-old fitness influencer and marathon runner shares two accessible ways to start moving

Retirement is often a time when people slow down, but in Christine Hobson’s case, she’s speeding up. When her daughter persuaded her to join a running club so she wouldn’t get bored, she had no idea she’d get the fitness bug and run 125 marathons in total, visiting all seven continents.

And the 72-year-old former teacher has plans to run the North Pole marathon in 2027.

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Why 21-15-9 Might be the Smartest Workout Format in Fitness – and How to Use it to Drive Muscle Growth

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Why 21-15-9 Might be the Smartest Workout Format in Fitness – and How to Use it to Drive Muscle Growth

CrossFit means a lot of things to a lot of people – because it’s made up of a lot of things.

Since the rise of the fitness giant, countless brands, events and training methods have sprung up around it – not claiming to be CrossFit, but looking suspiciously CrossFit-esque.

There are, however, a handful of things that are uniquely CrossFit: the ‘Girls’ benchmark workouts. The Hero WODs and, of course, its signature rep schemes.

Chief among them is ’21-15-9′.

The 21-15-9 rep scheme may just be the single most CrossFit thing in existence. But what exactly is it? Where did it come from? And why might it actually be better at building muscle in a hurry than its conditioning roots would have you believe?

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Let’s have a look.

What Is 21-15-9?

If you’ve never encountered it before, the format couldn’t be simpler. Choose two exercises (occasionally more) and perform 21 reps of each, then 15 reps of each, then nine reps of each, completing the entire workout as quickly as possible – with good form.

Probably the best-known example is ‘Fran’: 21 thrusters and pull-ups, followed by 15 of each, then nine. On paper it doesn’t look especially intimidating. In practice, it’s one of the most feared benchmark workouts in fitness.

Where Did it Come From?

Unlike many modern training methods, 21-15-9 didn’t come out of a study. It came from the gym floor.

CrossFit founder Greg Glassman has explained that the format emerged through years of coaching and experimentation in the 1990s. Rather than chasing a perfect sets-and-reps prescription, he was looking for a workout that allowed athletes to maintain a high power output from start to finish.

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The thinking is surprisingly elegant. You begin with 21 reps while fresh. By the time you reach the set of 15, your ability to produce force has already fallen. By the final nine, you’re significantly more fatigued – but the workload has dropped by almost the same amount.

Instead of grinding through increasingly miserable sets of the same length, the workout ‘meets you where you are’, reducing the work required as your capacity declines. The result is a workout that encourages you to keep moving instead of standing around trying to recover.

The numbers themselves are also remarkably practical. Forty-five total reps per movement provides plenty of training volume without turning the session into an endurance slog, while every set divides neatly into thirds if you need to break it up.

(Although I’ve got to be honest, I’m a 20-15-10-5 man myself, just for the sake of round numbers.)

Why Does it Work So Well?

Although there isn’t research showing that 21-15-9 is somehow the magic formula, there are obvious reasons why it consistently produces brutally effective workouts.

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Descending reps help maintain intensity. As fatigue accumulates, reducing the target allows movement quality, bar speed and overall work rate to stay higher than they would if you simply repeated the same number of reps over and over.

It also tends to land in a physiological sweet spot. Most 21-15-9 workouts take between three and eight minutes, depending on the movements and the athlete. That’s long enough to create a serious cardiovascular challenge while still requiring meaningful force production throughout. You’re taxing your anaerobic systems hard while relying on your aerobic system to help you recover just enough to keep going.

Finally, there’s the psychological trick. The hardest-looking part comes first. Once you’ve survived the opening 21, every remaining round appears more manageable. ‘Only 15 left.’ Then, ‘Just nine.’ In reality, you’re becoming more fatigued with every rep, but the shrinking target keeps you attacking the workout instead of pacing too conservatively.

Why it Might be Surprisingly Good for Building Muscle

Perhaps the biggest misconception about 21-15-9 is that it’s ‘just cardio with weights’.

Choose the right load and something interesting happens. Very few athletes complete every round unbroken. Instead, the workout naturally evolves into a series of short, broken sets separated by only a few seconds of rest.

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Your 21 might become 11-5-5. Your 15 becomes 8-4-3. Your final nine might stay unbroken – or become 5-4.

In effect, you’ve accidentally turned the workout into a form of rest-pause training.

Those brief pauses allow just enough recovery to squeeze out more high-quality repetitions before fatigue catches up again. By the latter stages of each mini-set, you’re repeatedly working very close to failure, recruiting the high-threshold motor units with the greatest potential for muscle growth.

It’s a similar principle to rest-pause training, myo-reps and cluster sets: all methods used to accumulate hypertrophy-friendly volume while keeping the load relatively heavy and the rest periods brutally short.

You’re basically speed-running a large number of hard, growth-stimulating reps in a very small window of time. Could this help explain why elite CrossFit athletes often carry an impressive amount of muscle despite spending relatively little time performing traditional bodybuilding splits?

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It’s certainly plausible, although the ‘elite’ part often selects for athletes with the greatest muscle-building potential.

Much of their training isn’t simply conditioning. It’s high-density resistance training performed under accumulating fatigue, with only fleeting recovery between efforts. In other words, they’re often doing something bodybuilders have deliberately programmed for decades: packing a lot of hard work into a very short period of time.

That’s not to say 21-15-9 is superior to a well-designed hypertrophy programme. If your sole goal is building muscle, there are more efficient ways to do it.

But if you’re looking for a workout that develops fitness, tests your mettle and still provides a meaningful stimulus for strength and size, it’s easy to see why this deceptively simple rep scheme has remained one of CrossFit’s defining fingerprints for more than 20 years.

Best Bodyweight 21-15-9 Workout: ‘JT’

If you’re looking for an interesting twist on the 21-15-9 format, look no further than Hero WOD ‘JT’, which concentrates the muscle-building potential of the format into a brutal upper-body workout.

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Created in honour of Petty Officer 1st Class Jeff Taylor, who was killed in Afghanistan in 2006, the workout strips away barbells altogether and relies solely on three bodyweight movements:

21-15-9 reps of:

Don’t let the lack of equipment fool you. The volume – 45 reps of each movement, 135 reps in total – combined with the descending rep scheme makes this a brutal upper-body test, hammering the shoulders, chest and triceps while demanding serious muscular endurance.

Better still, it perfectly demonstrates one of the biggest strengths of 21-15-9. As fatigue mounts and the sets naturally fragment, the workout begins to resemble one giant rest-pause set, allowing you to accumulate a huge number of hard, near-failure reps in less than 10 minutes.

If your goal is building an impressive upper body while developing serious work capacity, there are few bodyweight workouts that deliver quite so much bang for your buck, making ‘JT’ one of my personal favourites.

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If there’s one thing Kori Sampson knows, it’s how to optimise your body composition for performance. To tap into his knowledge as an elite athlete and coach, we asked him to create a 4-week plan to help you move faster, recover quicker and keep pushing when the fatigue sets in – all while improving your muscle-to-fat ratio.

Ready to build muscle, burn fat and come out the other side looking, feeling and performing better? Click here to get 14 days of free access to the plan via the Men’s Health app.


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10 minutes of swimming might not sound worth it – but I tried it for 2 weeks and found the benefits of a quick dip

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10 minutes of swimming might not sound worth it – but I tried it for 2 weeks and found the benefits of a quick dip

The concept of ‘exercise snacking’ has never been more popular. Not only is it convenient and accessible, but there is solid scientific evidence that short bursts of physical activity can yield real benefits for our health. But can a swimming workout be an effective ‘exercise snack’?

A study published in the European Heart Journal found that just 15 to 20 minutes of vigorous physical activity a week (almost as low as two minutes a day) was enough to significantly lower the risk of heart disease, cancer and early death. The study defined vigorous activity as any exercise that leaves you out of breath and raises your heart rate, including swimming.

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