Taking an ice-cold bath would be the last thing to make you feel intimate, you may imagine - but it could give your sex life a significant boost.
Such is the experience of Dr Oberdan Marianetti, a Singapore-based psychologist and clinical sexologist and a practitioner of the Wim Hof Method. Wim Hof, known as The Iceman, is a Dutch extreme athlete who popularised cold therapy and breathwork, or controlled hyperventilation.
Four years ago, Marianetti founded OM-Ice retreats, a residential programme which incorporates psychology, breathwork, movement and cold exposure over a few days.
When he first heard of Hof's penchant for having people submerge themselves in ice baths, Marianetti was sceptical.
"Initially I dismissed the idea, this is clearly a gimmick, I thought."
But when he read articles backed by scientific evidence in support of the method, he decided to experiment.
He set up a homemade ice bath in his Singapore flat (cold showers were not an option; Singapore's mains water pipes flow at a fairly constant 24 degrees Celsius, and you need a temperature of 15 degrees or less to reap the benefits).
After his first icy plunge, he instantly felt better. Now he bathes in ice every day; this, combined with yoga and breathwork , has an array of mental and physical benefits - including being "in the best shape, at age 49, of my adult life".
Not long after his first ice bath, he made the connection between cold exposure and having a better sex life. "This is something I have thought about and looked into for quite some time," he says.
"Physiologically much of the sexual experience relies on a healthy cardiovascular system and a healthy nervous system," he explains, "because both the penis and vulva are erectile organs that rely on a strong blood flow to become engorged and allow penetration to occur to lead up to a pleasurable experience."
Regular cold exposure can provide a fundamental "workout" for the cardiovascular system.
"When you expose the body to extreme cold, blood vessels narrow as a result of vasoconstriction, the response whereby the blood vessels contract, especially in the extremities (which in evolutionary terms are 'expendable'), to push blood to the vital organs and head to keep them warm."
Vasoconstriction happens through the constriction of muscle fibres running throughout the body. Like any muscle, if not used enough they become weak, with the potential to lose part of their function.
In our modern, comfortable lives with central heating and air conditioning , there are fewer instances in which vasoconstriction and vasodilation occur naturally, he adds, unless one deliberately seeks them out.
"This cardiovascular 'training' can contribute to a more immediate and reliable sexual experience physically," Marianetti explains.
Even more important is the mental response.
"As a sex therapist, one of the most common complaints I see among men is erectile dysfunction. When it happens, it creates a psychological impact that can lead to deep self-confidence and self-esteem issues which, if left untreated, can destroy a relationship," he says.
"Often, this is down to past experiences, which can lead to a vicious cycle of anxiety." But when the body feels stronger and healthier, the brain reacts with more positive inputs - "the body and brain healthily feed each other positive signals".
There is also the factor of what he calls "spectatoring", another common complaint from clients who find themselves unable to be "present" and feeling like external observers when they have sex with their partner.
"The ability to train the mind to focus is another benefit from cold exposure that can positively influence the sexual experience," he says.
"Imagine I am eating the best pizza in the world, but I'm so preoccupied with a project, I'm paying zero attention to the pizza. The quality of the experience would be transformed were I to pay attention to what I was doing. When people say, 'there's no passion, no connection, it's not fun any more', training the mind can help with this."
Ice baths combined with breathwork can help build mental toughness, says Marianetti - it takes self-discipline to stay focused on your breathing and not to quit or start hyperventilating.
"Exposing yourself to cold forces you to develop your mental strength by managing the primal instinct to shiver and hyperventilate and, over time, you will learn to silence the inner panic in your mind, strengthening the ability to fight distractions and be present in the moment."
For those trying it at home, he recommends beginners start with just 30 seconds under a cold shower, switching to hot water and back to cold, building up to a few minutes at a time. He also advocates dipping in natural cold-water sources like lakes, lidos or the sea, if available. If not, a few minutes in a cold bath at home will do the trick.
The benefits of cold exposure are not limited to sex. The Wim Hof Method is known for its ability to help people combat depression, rebalance hormones, aid in fat loss and even suppress pain and fight autoimmune disease.
Inspired by Hof, scientists have experimented on Wim Hof practitioners to better understand the reasoning behind it.
For example, in a 2014 study, Wim Hof Method practitioners were injected with an endotoxin which showed they were able to control their sympathetic nervous system and immune response. This suggested the Wim Hof Method might be a tool to battle symptoms of autoimmune diseases.
Meanwhile, a 2018 study showed that the Wim Hof Method activated regions in the brain responsible for pain suppression.
Marianetti believes much of this comes back to the way cold exposure empowers the brain beyond our self-imposed limitations.
"All of the work I do professionally stems from the belief that many modern ailments are a result of a fundamental disconnection from ourselves.
"We lead lives that condition us to become compliant to society's expectations, we become adept at mixing with the crowd, we live lives that resemble a script that is not our own," he says.
"This can lead to feelings of emptiness. The aim is to break through our core self-limiting beliefs which are holding us back.
"Combining ice baths, movement and meditation or mindfulness provides an opportunity to reconnect with ourselves, rekindle our sense of self and sense of power that resides within being our authentic self."
This article was first published in South China Morning Post.