THESE super-fit girls can lift weights without breaking a sweat. But the one place that isn’t their strong point is the bedroom.

New research shows too much exercise can kill your sex drive. The University of North Carolina in the US studied people’s exercise habits and libido levels. It found those who train for a long time at high intensity suffer an almost instant loss of sex drive.

Exhaustion from training leaves some too tired to perform, while pushing yourself with extreme exercise can lead to an under-functioning pituitary gland, meaning low levels of testosterone and oestrogen.

Women also need a certain level of body fat for the reproductive system to work effectively.

Too much exercise and too little body fat can cause it to shut down, nipping passion in the bud.

Here, four fitness fans tell Jenny Francis how working out in the gym and enjoying hard training has affected their love life.

‘My libido’s vanished’

Nikki Harvey worries a “zero sex drive” will push away her 26-year-old partner Jordan Burgess, a personal trainer.

Nikki, from Wolverhampton, was an overweight smoker who did no exercise but has transformed her body in three years. She says:

“In the autumn of 2014 I was a size 16, drinking, smoking, living off junk food and generally pretty miserable.

“One night I met Jordan and we quickly became an item.

“He’s a rugby player and he caught me crying to myself in my bedroom when I couldn’t fit into my size 14 clothes.

“He told me anyone can turn their life around and inspired me to get healthy and take up fitness and bodybuilding.

“I signed up for a 14-week intensive program, pushing me harder than I ever dreamed possible. I loved every second.

“Every gram of excess weight was stripped from my body — better than any faddy diet.

“I now train every morning at 5.30 for two hours, then do an hour’s cardio every evening.

“It really impacts on my relationship. I haven’t been on a date night with Jordan since January and my libido has vanished.

“Right now I have zero sex drive so Jordan and I haven’t had made love for two months. Jordan hates it but he knows it’s not because I don’t fancy him. I love my training so much that two months ago I quit my job to do it full time.

“In April I came second in the UK Bodybuilding and Fitness Federation National Finals and qualified for three international championships.

“My libido might be gone but I look better and am now so much healthier.

“I just hope that Jordan will stick by me without sex.”

‘I don’t need a relationship’

Fitness addict Gabriella Prior, 22, from Bournemouth, would rather be in good shape than have a sex life. Gabriella has not had sex for more than 18 months. She says:

“At the start of 2016 I did almost no exercise. I went out drinking, enjoyed lazy weekends, had boyfriends and a healthy sex life. I wasn’t depressed but I felt like I didn’t have any hobbies.

“One morning, on a whim, I decided to join the nearby House of Pain boxing gym. I was nervous but when I left I was so full of energy I couldn’t wait to do it again.

Exercising is now like a drug to me. Within weeks I was training twice a day for two hours each session, five or six days a week. I still do that now.

“It’s 100 per cent effort training with weights, sparring and cardio. Boxing isn’t a sport you do by halves. I can hardly tie my shoe laces after I have finished a session, let alone think about sex. I used to have boyfriends but they ran their course.

“Now I don’t have time to meet men. I have realised I don’t need a relationship or sex to be happy. I value independence and fitness more than I thought possible. My sex life now is a dim and distant memory.

“I hope that if I ever want to, I can reduce the intensity of my training and then get my libido back. But I’m not bothered now.

“I’ve had a couple of short-lived relationships since I started training but quickly I’ve been dumped because they thought I was boring, as I did not want to have sex all the time.

“I have been crowned Miss Fitness Inspiration UK, which means more to me than any amount of sex.”

‘It was my physique which first attracted my man to me’

Milly ­Mahoney’s low sex drive puts pressure on her relationship with partner Manny Tankov, 26, an airconditioning worker. Milly, 25, of Wood Green, North ­London, says:

“I remember seeing a friend’s washboard stomach on holiday three years ago and thinking, ‘I want that’. I’d done a bit of running before but knew I had to hit the weights to get the body I wanted. So I joined a gym.

“Five or six days a week I train as hard as I can for two hours, to the point of exhaustion. When Manny comes on to me, sex is the last thing I want as I’m shattered. I push away his hands. He’s visibly frustrated and takes a few minutes to calm down.

“Before I started training I would have sex at least five days a week, which seems strange now. I’m also obsessive about my diet, weighing every last gram of protein or carbs — which means we do not eat takeaways together or have date nights in restaurants. I’ve been with Manny for 18 months and he understands how much I love working out — it was my physique that first attracted him.

“I’m training for a bikini competition and we haven’t had sex for two months. I guess it’s a bit like giving up drinking for a month — you realise how much better you feel, then when it comes to the end of the month, you question if you actually want a drink at all any more.

“I feel fantastic and look great. No amount of sex beats that.”

‘I have hard pecs instead of boobs so I don’t feel attractive’

Stacey Boyce trains so hard that she often cannot even muster enough energy to cuddle her husband. The conference company director from Brighton goes to the gym daily and admits that starting at 5am or finishing after midnight means she has no time for sex. She says:

“I have been training really hard down at the gym since 2014.

“While I love it and wouldn’t change a thing, it gets harder every year.

“I’m in the gym most days of the week and my diet is so closely controlled, it has become completely addictive for me.

“I have been with my husband, Mark, for six years and thankfully he also works in the fitness industry.

“He understands the way I am, to a certain extent, but the strain on our relationship is massive.

“Before I started with all the gym training, it was totally different between the two of us. We would have sex at least three times a week.

“Now, sometimes we don’t talk for days — and having sex even once a month is a push.

“My libido is non-existent. I know I’m demanding a lot from my body by lifting massive weights and sometimes I can’t even cuddle.

“Every single muscle in my body hurts, making sex completely out of the question.

I’m exhausted all the time and when I’m training hard I have hard pecs instead of boobs, so definitely don’t feel at all attractive or feminine.

“I get so focused on myself, constantly checking my weight, measuring body fat, weighing food and training for endless hours.

“I know it’s very selfish to behave in this way. But that’s how I became a 2015 British UK Ultimate Physiques Bikini Champion.

“Of course, sex is natural and enjoyable. But if you are in a loving and understanding relationship, the sex can wait.”

This article originally appeared on The Sun and has been republished with permission.