It's the bane of many knowledge workers. You join the gym, do some personal training, follow the workout sheets and put in the hours. And after a couple of months, you've barely moved the needle.

Maybe you have the wrong workout, or you're working out at the wrong time of day or you have a poor diet. But it's also increasingly likely you're bringing your professional stresses and mentality into the gym, where they get in the way of your body. In a new twist on an old aphorism, the body is willing but the mind is elsewhere.

"It doesn't matter your exercise, or how intense you make it," says Cameron Smith, owner of Protrain Fitness in Darlinghurst, Sydney. "If your mind is not engaged with your body, you won't get the results."

Smith's gym deals largely with what he calls high-achieving professionals, and with these people the starting point is not a lack of motivation but complete absorption in work-related issues. The distraction is their own minds.

"If a person is not focused, usually the first thing you notice is that they're holding their breath," says Smith. "They get dizzy, they get tired very quickly, and you have to stop, do some breathing exercises and get them back into it."

Another telltale sign is when a client forgets how to do an exercise halfway through the action, or can't remember what part of their body should be working.

Focus on form

"A lot of high-achieving people join the gym and they just go through the motions," says Smith. "They're thinking about what they'll say in a meeting or how they're going to answer an email. But if you're not thinking about your body movements, you're not getting the benefits of your workout and you raise the risk of injury. You don't want to be lifting weights if you're not focused on your form."

He says dealing with the mental aspects of a workout is an integral part of what he does. All his clients start their workouts with a discussion about the day's and week's events, which can be an effective release. Others need goal-setting reminders and discussions about progress.

Smith's business has become so concerned with getting clients' heads in the game he has invested in a $12,000 Japanese massage chair and opened a special noise-suppressed massage room.

"A lot of these people are stressed and they need to be left alone for a while," says Smith. "We offer a 20-minute wind-down massage after a workout, and all our clients use it. I think some of them are coming for that chair."

The connection between mind and body – fatigue and concentration – is well known, but most of the studies have served to show that physical fatigue degrades mental acuity. Swinburne University head of exercise science Clare MacMahon and a team turned this around with a study that investigated the effect of cognitive fatigue on physical performance in a running task.

Experienced runners performed two 3000 metre runs, one while they were mentally tired and the other when they weren't. The study, published in the Journal of Sport and Exercise Psychology in 2014, found completion times were significantly slower when the runners were cognitively fatigued. But there were no differences in heart rate, blood lactate levels or ratings of perceived exertion – it was all mental.

"The study showed that cognitive fatigue increases the perception of exertion, leading to a poorer performance in the running task," says MacMahon. "Even when the physiological levels are normal, your cognitive fatigue creates the perception of physical fatigue."

Put another way, where your brain leads, your body will follow.

Tired and unmotivated

MacMahon says there are two ways to look at the problem: the psycho-biological model, in which perception of fatigue overrides the physical reality; and the social psychology model, in which self-control is a finite resource. After a hard day of reading spreadsheets, the brain doesn't want self-control expended at the gym or on the tennis court.

Either way, says MacMahon, a person who has done nothing with their body all day can feel tired and unmotivated to exercise because their brain is tired.

"People who work all day processing information and making decisions become confused," says MacMahon. "They can't understand why it is that they sat on a chair all day and now they can't face the gym."

She says the research has shown a couple of easy fixes to quickly refresh the brain. "Being in nature, even for a few minutes, refreshes the brain. So does sitting quietly for a few minutes – no screens, no phones, no talking."

Ben Lucas, owner of Flow Athletic in Sydney, also deals mainly with high-achiever, professional clients at his Paddington gym. He gets them to workout after exercises in goal setting and motivation.

"If you're going to achieve your physical goals, you have to be mentally engaged in what you're doing," he says. "Some of our clients have enormous to-do lists and work loads, and we have to help them focus on getting the most out of their workouts."

Effective workout regimes

Lucas, a former rugby league player for the Cronulla Sharks and an ultra-endurance athlete, says effective workout regimes for high achievers have to start with the mind. "Our clients live by their diaries, so we start by getting them to schedule their workouts. If it's in the diary, they'll do it, as if it's a meeting. The diary equals commitment."

He keeps clients focused by insisting they keep exercise and food diaries, because measuring the work and gains makes people accountable for their actions.

"In 20 years of doing this, I have never had a client keep a food diary and not lose weight."

In the end, he says, physical gains don't happen if the brain doesn't want them to happen, so the mind has to be in control.

"The most important aspect of physical fitness is consistency. Many small steps, over a period of time, gets you to your goals. That takes discipline – and discipline is a mental quality."