REMINISCE FOR A MOMENT ABOUT THE FIRST TIME SHE SLIPPED HER HAND below your waistline and inched it lower… lower… lower. Now imagine biting into a tender, juicy steak. And remember when the older kids used to chase you and your friends? You ran for your life, terrified, but once you’d escaped, the rush you felt bordered on euphoria.

In each case, your brain’s survival circuitry flooded your synapses with dopamine and other reward chemicals, forever conditioning you to mate, eat, fight, flee or bond with others as the situation warranted. Odds are, your first months in the gym inspired similar feelings of awesomeness that rippled beyond those walls whenever your girlfriend caught you shirtless.

Evolutionarily, it makes perfect sense: exercise not only boosts your sex appeal but also, as you become fitter, increases your odds of living to see your next meal. At least that’s how your brain’s pleasure-reward centres (the frontal cortex and nucleus accumbens) view the situation; they don’t realise that working out isn’t, in fact, necessary for survival in the modern world. Indeed, exercise burns kilojoules that could be used to mate, flee and fight.

“We know the hardwiring that promotes voluntary movement and playing – or in this case exercising – is likely tied to the same neurocircuits involved in searching and feeding,” says Rodney Dishman, a professor of exercise science at the University of Georgia who’s been studying the role of motivation in physical activity for 30 years. “So if our bodies have evolved to conserve energy and resist things like fat loss, then it makes perfect sense that our brains will actually defend against moving too much.”

The solution is to hack your brain’s hardwiring to trick those pleasure-reward centres into once again perceiving exercise as necessary to your survival. In other words, you need to make your workouts seem as desirable as sex, as stimulating as running for your life and as sublimely hedonic as biting into a warm cookie. And you can do that with just a few simple tweaks to your existing fitness routine.

BRAIN HACK 1: Speed Up Your Workouts

When you sprint all out towards a goal – as when our prehistoric ancestors chased down food – your brain’s reward is a blast of dopamine that imprints the memory of your success and how good it felt. “High-intensity interval training [HIIT] has a similar effect,” says Dishman. “Unlike resistance training or even long-distance cardio, it significantly increases bloodflow in the frontal cortex.”

YOUR MOVE

Find a hill that takes about 20 to 30 seconds to sprint up, and after a brief warm-up (10 minutes of jogging will do the trick), race to the top as fast as you can. When you get there, do 40 mountain climbers followed by 10 push-ups; then walk down.

Repeat the circuit (sprint, mountain climbers, push-ups, walk) as many times as you can in 20 minutes. “Hills do triple duty,” says Josh Stolz, a personal trainer at Equinox in New York City. “You have a goal you can see, you’re building power and reaching exhaustion faster than you would on flat ground, and the walk back down provides a natural recovery period so you’ll be able to push it during the next uphill interval.

It’s a great cardio workout.”

BRAIN HACK 2: Use Sex as a Motivator

Have you ever found yourself doing something wholly unpleasant – shopping for linen, attending a baby shower, watching Grey’s Anatomy – simply to please a woman? That’s your brain on sex; your neurochemistry is prodding you to muscle through the anguish to increase your odds of copulating.

Similarly, you can use sex as a motivator to keep yourself moving through your workouts and coming back for more, day after day, says Men’s Health sex and relationships advisor Debby Herbenick. She’s a research scientist at Indiana University and the author of Great in Bed, so she ought to know.

YOUR MOVE

One week each month, strike a bargain with your partner that you can have sex only on the days you (or even better, both of you) work out.

“The benefits extend beyond simple motivation,” says Herbenick. “Increased bloodflow from exercise stimulates the genitals, enhancing arousal and pleasure.”

And let’s face it: Sex requires a lot of repetitive motions, especially in the core. If you want to sustain that woman-pleasing rhythm, you’d better hit the gym regularly.

BRAIN HACK 3: Lift to the Death

The human brain is one of nature’s most advanced systems, but it nevertheless has a hard time distinguishing the difference between real and imagined threats. You can use that programming to your advantage by creating “life or death” scenarios in the weight room that trick your brain into releasing reward chemicals, helping you push yourself harder and longer, says Stolz.

YOUR MOVE

Grab a pair of 24kg kettlebells and have a buddy jump on a rowing machine. Rack the kettlebells – that is, hold them in front of your shoulders with your elbows tucked and your palms facing in – and have your buddy start rowing as fast as he can. If you lower the weights before he reaches 250 metres, he’s “dead”.

Once he hits his mark, switch positions and repeat. That’s one round. Go for five. “It forces you to ‘save’ your friend,” says Stolz. “After one or two rounds, you’ll be holding on – and rowing – for what seems like dear life.”

BRAIN HACK 4: Showcase Your Skills

Socialising, playing and cooperating with others – behaviours long known to be essential for human survival – can have a significant impact on workout performance, according to a Michigan State University study. The researchers found that people who worked out together as part of a team exercised harder and more than twice as long as those who sweated solo.

Their motivation? Fear of being the weakest link. And anyone can enjoy the same performance boost by backing off the lone-wolf sweat sessions and participating in more group workouts, preferably with complete strangers, says Greg Robins, a coach at Cressey Performance in Massachusetts.

YOUR MOVE

Join a five-a-side game at an unfamiliar court, sign up for an intramural sport or just take a new group class. “If you’re playing or exercising with new people, you’ll hustle and work harder to elevate your game,” says Robins.

BRAIN HACK 5: Taste Something Sweet

There’s a reason you have a sweet tooth: your brain rewards you for ingesting sugar, which is a major source of cellular energy once it’s converted to glucose. Energy drinks are meant to replenish those glucose stores, but you don’t need to actually drink them to enjoy a boost.

In research from the UK, endurance cyclists who simply rinsed their mouths with glucose-infused water (a sports drink by any other name) pedalled faster, had more power and showed increased activation in their brains’ reward centres, resulting in increased overall performance.

YOUR MOVE

When you feel yourself hitting a wall during a spin class or long run, swish a mouthful of your favourite sports drink and spit it out. You’ll get the neurochemical reward without the kJ price tag.

Just don’t try to swap in a zero-kilojoule beverage. In the study, cyclists who were given an artificially sweetened drink failed to feel a lift.