The Energy Cost
of Attention.

Between lessons I sometimes have an hour, and I sit in my car, in the air conditioning, partly so nobody talks to me for an hour. I am physically resting. And half the time I spend that hour on the phone anyway, answering emails, reading this and that. When I come back to the court I am more tired than before the break.

That used to puzzle me. My body rested the whole hour. My mind did not, and apparently that is not free.

Players know a version of the same thing. A player has a good session on Tuesday. Attention comes easily, stays on the ball, holds through the long rallies. On Thursday the same player, with the same instruction and the same intention, cannot hold it for four points in a row. Attention frays. It goes to the phone in the bag, to the error two points ago, to what happens after practice.

The usual explanations are motivation and discipline. He did not want it enough today. She was not focused.

Sometimes that is accurate. Often it is not. And there is a third explanation that is easy to miss, because it does not present as a mental problem at all.

Naomi Osaka, asked at the Australian Open how she judges her own performances beyond the scoreline, described the cost directly. Even in a match that looks comfortable from the outside, she said, "you had to focus that entire match and it's mentally a bit draining." The scoreline showed a straightforward win. What it did not show was what holding attention for two hours had taken out of her.

That is not a figure of speech. The brain is about two percent of body mass and uses roughly twenty percent of the body's energy. That budget is not fixed. It moves with sleep, illness, inflammation, chronic stress, and age.

What matters for a player is which functions get cut first when the budget tightens. It is the expensive ones. Holding attention on one object for a long time is expensive. Staying with a sensation you would rather not feel is expensive. Keeping attention off the last point, when it keeps returning there, is expensive. Mind-wandering costs very little by comparison: the network that produces it runs cheaply.

So he lost focus in the third set can be a true description of what happened and still be the wrong diagnosis of why. In many cases the player did not decide to stop attending. The capacity to keep attending ran out, the way a leg gives out in the fifth set of a long match. We do not usually call that a discipline problem.

Once you look at it this way, a set of unrelated-looking problems turn into one problem: the fog after illness, the plateau in a meditation practice, the player whose quality drops in week three of a hard training block. The situations are different. The constraint underneath is the same one.

The helmet

Since the end of July I have been carrying a helmet in my tennis bag. It has more than 250 infrared lights on the inside, I wear it every day, and I have started putting it on players before they practice.

It is called the Neuromatrix Headset, and it is a photobiomodulation device, which is a long word for a fairly narrow idea: use light to act on the energy supply rather than on behavior.

I first heard about technologies like this fifteen years ago, sitting in a silent retreat, listening to Shinzen Young talk about them. They were first of their kind then. He was using them on himself, and he did not know what the long-term effects would be. Nobody did. That was the deal at that stage of the science: you experiment, and you do not know the outcomes, long-term or mid-term. It takes those people. That is what the frontier of a field looks like from the inside, someone running the experiment on themselves so the people after them do not have to guess.

Fifteen years later, because of people like him and like Sanjay, one of those objects is the one in my bag, with a research literature around it instead of a guess. I am excited about this in a way I am rarely excited about equipment. There is a device on a tennis court that turns the background noise down and makes focusing easier, and I heard it described as a possibility a decade and a half before I could put it on a player.

Sanjay Manchanda, who designed it, has spent over three decades in clinical practice, twenty-five years of it in neurotherapy, and about as long as a meditator and teacher. I will keep the mechanism short and let his paper carry the precise claims.

Light between roughly 600 and 1100 nanometers, red through near-infrared, passes through skin and skull in usable amounts. Inside the brain, his paper maps four effects with real evidence behind them. It raises energy production: the light is absorbed mainly by one enzyme in the mitochondria, cytochrome c oxidase, and ATP output rises. It improves delivery: nitric oxide gets knocked off that same enzyme and widens local blood vessels, so blood flow rises where the light landed. It gives the cell a training stimulus: a brief, small rise in oxidative stress that the cell answers by strengthening its own defenses. Athletes know this curve from physical training: the right load builds you up, too much does not. It is also the reason more is not better with this device. And it settles the brain’s immune cells, which under chronic stress or illness sit in an inflammatory mode that makes ordinary thinking expensive.

On the first of those, the paper is exact about what kind of claim it is making:

This is not a metaphor about “energy.” It is a measurable change in the rate of a specific enzymatic reaction.

Sanjay Manchanda, The Energy Behind Awareness

Those four effects are all one dial: how much energy the system gets to work with. There is a second dial, and it is rhythm. The light is not continuous. It pulses, and the pulse rate matters on its own: 10 Hz and 40 Hz produce different effects on brain rhythm at an identical dose. His paper makes the argument in one line: “If light only added energy, pulse rate would be irrelevant and only average power would matter. It is not irrelevant.” So the device has two controls: how much energy arrives, and what rhythm it arrives in.

All of that is upstream. What comes out the other end is a larger budget. The important part is what a larger budget changes and what it does not, and that is easier to show than to say.

What it actually does

One of my older players stopped me in the gym and asked what the helmet was for. I told him: “It doesn’t give you an ability to focus that you don’t already have. But it allows you to access your focus at the higher end of what you do have.”

Sanjay makes the same claim about his own device, which is part of why I took it seriously. In conversation he calls it “a resonance device” that “helps you catch that frequency in your system… like the tuning fork idea.” If the frequency is available in you, the light gives you something to catch. His written formulation is careful, and it is worth quoting exactly:

PBM does not install a state. It removes an energetic constraint on the states you are already capable of entering.

Sanjay Manchanda, The Energy Behind Awareness

That is a narrow claim, deliberately. It is also the one that matches what I have seen.

What I have noticed

I have been using it daily since the end of July. My protocol is eight minutes on the rejuvenate setting followed by twelve minutes on focus, sitting, usually meditating through it. The meditation is not required. It works either way. But the time is there, so you might as well use it.

What I notice is not dramatic, and it is not supposed to be. It is closer to the difference between a practice session where concentration gathers on its own and one where I have to keep rebuilding it. Both sessions happen. The light seems to move the odds toward the first kind.

The comparison I keep coming back to is retreat. On day three or four of a silent retreat, something changes in how attention behaves. It stops needing to be dragged back. It settles and stays settled, and the whole practice gets easier, not because you have learned anything new in three days but because the noise has come down. That is the quality this reproduces, in a smaller dose, in twenty minutes.

What the players noticed

I have started testing it with players I coach, with their knowledge and on a voluntary basis. Three reports are worth passing on.

The first player meditates regularly and has sat a silent retreat. She used the focus setting for the second time before a practice, and her description afterwards: it simulates being on a silent retreat for a full day, just from putting the helmet on. What she pointed to was the noise. Normally there are a lot of things happening at once. With it on, she said, you do not have all the extra noise in your head. You are tracked on one thing. Not the thing to do later, not the message to answer. She went to practice and said she could focus much better, and that she was in the moment, on one thing at a time.

The second player compared it in this way: it felt like Adderall, he said. Really stimulated, more locked in. Whatever it is you are doing, you are really focused on that. At the water break that session he told me he had attention on almost every single ball, and that he was much more consistent. From the outside it looked like it: the same shots, significantly fewer mistakes.

The third report was also very insightful, because it came on a bad day. The player arrived feeling fine physically and terrible emotionally, and said he had tried to meditate that morning and could not, that ten minutes had felt impossible. I had him sit under the helmet for twenty minutes and practice his regular mental exercise. His report afterwards was subtle and precise. He was not simply lost in thought the whole time. The drifting did not feel as drifty as normal. When he wanted to place attention on something for a second, it felt easier, it was just right there. Getting lost in thought during practice, he said, usually feels like going under anesthesia: you disappear and surface three minutes later. This time, even when he was thinking, he was presently thinking. He also had noticeably fewer thoughts, and he felt better for it, because the thoughts were what had been agitating him: going over the problems of the day so far. And then he added: still suffering a lot. Which is correct. It does not get rid of anything that is there.

Three reports, from the first weeks, from players who knew what the device was supposed to do. That is not evidence. It is the reason to keep looking.

Where this lands in the three skills

The mental training I do stands on three skills: concentration, sensory clarity, and equanimity. One thing about them needs saying first. Every player is already training these skills every time they play, whether or not they have ever done a minute of formal mental training. Trying to focus on something for a whole point is concentration in use. The method may be rough, and that is fine. You are doing it to whatever degree you know how.

Which is why the energy budget concerns every player, not only the ones who train the mental side systematically. Whatever amount of these skills you have built, formally or just by playing, more of it is available to you when the energy to run it is there. Focusing gets easier at every level of skill. And the player who is as focused as they can be will outperform the one who cannot get there.

A tool that changes the energy budget does not train any of the three. But each of them costs something to use, so each one is exposed to the budget in its own way.

Concentration is where attention goes, for how long, and with what reliability. This is the skill the reports so far point at. Holding attention on one object, and holding it against the pull of everything else, are the two expensive parts of the skill, and they are exactly what the players described getting easier: one thing at a time, the extra noise gone, attention just right there when you reach for it. It is what I notice in my own sitting too. Attention holds without needing to be rebuilt so often.

Sensory clarity is the resolution of what attention lands on: whether the player notices the ball’s height, their own position, the early signs of the opponent’s direction, in enough detail and in time to act. The prediction here is simple. Attention that is not being spent on holding itself together has more left over for noticing. The first report has arrived here too: I asked the player from the bad morning whether a description another user had given me fit, that normally it is like looking through milky glass and now the resolution is turned up slightly, and he agreed, and connected it himself to attention being easier to move. What I watch for on court is specific: whether a player notices their position and distance earlier in the rally than they did before. Sanjay’s own report sits in this territory. He describes his vision clearing when he uses it, things looking “sharper, cleaner,” and says versions of that report are common among his users.

Equanimity is the ability to allow experience to be as it is, without suppression, clinging, or dismissal. It is not calmness, and this device does not make anyone calm. The connection to energy runs through a specific fact: fighting experience is itself expensive. Pushing away frustration after an error draws on the same budget everything else draws on. Grigor Dimitrov, asked about a difficult stretch earlier in the season, described that cost from the inside: “it’s tough mentally to really deal with that, but then in the same time go into a practice session and be sort of thought free and just focus on what you got to do.” Two things point at this skill. In Sanjay’s meditation study, the effect was strongest in practitioners of open-monitoring styles, the wide, allowing posture, which is what the energy argument would predict, because a broad field held without collapsing onto any one object is probably the most expensive posture there is. And less reactivity is among the reports his user community makes most often. And the bad-morning report says something here too: attention easier to place, and still suffering a lot. The device did not touch what was there to be allowed. From my side: my own sits are more open. And the court version follows from everything above. Staying with what is there costs energy, and when more energy is available, it is easier to allow.

What it does not do

If someone else had written this post, this is the section I would read first.

It is not a medical device. It is not FDA-cleared to diagnose or treat anything, and nothing here is a treatment claim. The company that makes it says this plainly in its own material, which I count in their favor.

The evidence is real but early. The result everything else in this field is built on came out of UT Austin in 2013: eight minutes of near-infrared light to the forehead, run against placebo, after which the treated group reacted faster on a sustained-attention task and did better on a working-memory task. Some of the difference was still there when they were retested two weeks on. Several independent labs have since found effects in the same direction, and the EEG work has been replicated in its direction. What has not improved much is the quality of the base: small samples, protocols that vary from lab to lab, and a young field with commercial money in it, which is exactly the setup where publication bias is hardest to rule out.

The meditation study is smaller than it sounds. The result most often cited in this space is a sham-controlled crossover study in twenty experienced meditators, which found a moderate increase in a measure of mystical-type experience under active stimulation. It is a genuinely interesting result, particularly because the effect was stronger in open-monitoring practitioners than in focused-attention practitioners, which is what the energy argument would predict. It is also twenty people, and it was run on a different device than the one I own. The manufacturer says so directly. Their similar findings on this headset are, so far, anecdotal.

More is not better. The dose-response curve is biphasic, which is an unusual property and easy to get wrong. Under-dose and nothing happens. Over-dose and you do not get more than the right dose would have given you, you get less, sometimes nothing at all. Push further and it turns actively unpleasant: tiredness, agitation, a headache, congestion. That is the opposite of the reason to put it on. The instructions say to start short and let the sessions lengthen over weeks, and they mean it.

The same session is not the same dose for everyone. Melanin absorbs near-infrared light, so how much of it reaches tissue depends in part on skin tone. Two players running an identical program are not necessarily getting an identical dose.

There are real contraindications. It uses flashing infrared light and has not been tested in people with photosensitive epilepsy. Anyone with a seizure history, an implanted medical device, a photosensitizing medication, or a pregnancy should talk to a doctor first. It is not intended for children.

And it does not build the skill. This is the part that matters for a player.

Where it fits in the training

A tool that raises the ceiling is only worth having if you are doing something with the room it opens.

A player who has not trained these skills deliberately still benefits, because they are using them anyway, at whatever level playing has built. But the light supplies no instruction about where attention should go, what to notice, or how to be with what arises. That part is the method, and there is no version of this where the device does it for you. More headroom makes the skills you have easier to reach. It does not add to them.

What it can do is change the conditions the training happens under. A player who arrives at a concentration exercise with more available headroom gets more out of the exercise. A player who does their between-point routine after twenty minutes under the light has a better chance of the routine actually landing. That is a supply-side intervention on a skill-side problem, and it only pays off if the skill work is happening.

Which is also the thing I am watching. There is a difference between a player having better sessions and a player building the skill faster. The first is easy to produce and easy to mistake for the second.

The excitement and the care are not in conflict, and I intend to keep both. The device acts on the supply. The skill is still the skill. What I will know in a year, and do not know now, is whether players who train attention with more headroom available actually build it faster, or whether they just have better practice days. When I know, I will write it.

Have a follow-up question? Ask the assistant →