This is spinal zap

Then they were told to prepare for a job interview. They were to imagine that this interview was for their ideal job. And with only five minutes of preparation, each participant was made to give a speech on why they were the best candidate for the job. They then performed the speech in front of a camera, without notes, for five minutes. If a participant stopped talking during that time, they were prompted to continue until their five minutes was up.

And if that wasn't difficult enough, one half of the participants were asked to give their speech while sitting in a slumped position; while the other half were made to sit in a very upright position.

Everyone who took part believed they were in a competition to win $200 in vouchers. In reality, they were taking part in a psychological experiment. The University of Auckland researchers were using a variation of the Trier Social Stress Test, a test designed to cause short-term psychological stress.

And by monitoring each participant's behaviour, speech patterns, blood pressure and heart rate, the researchers could see that all of the participants were under stress.

But some handled it better than others.

The researchers found that those who had been made to sit in the slumped position experienced the most stress. These participants also reported feeling sleepy and sluggish during the experiment.

However, those who had sat upright had felt more enthusiastic and excited, and less fearful during the test. This led the research team to conclude: "Sitting upright may be a simple behavioural strategy to help build resilience to stress."

It's well established that improving your posture provides a number of important benefits. It reduces neck and back pain, it alleviates some headaches, and it can even improve your breathing by allowing your lungs to expand and contract properly.

But can it really help you beat stress and improve your mental well-being?

Following the success of this study, the University of Auckland team repeated it. "I was interested in doing this study because there's quite a bit of research that shows that our posture changes with our mood," says the study's senior author, Elizabeth Broadbent. "But I wanted to answer the question, can changing your posture change your mood?"

This time, the volunteers were screened to identify those with the symptoms of mild to moderate depression. "Most of the existing research was done with healthy people," says Elizabeth. "This is one of the first studies that's actually tried to look at the effects in people with depression."

All of the participants had significantly slumped posture, which is recognised as a physical symptom of depression. And in this experiment, one half of the participants maintained their normal slumped posture, while the other half were put into an upright posture and held in that posture with the aid of physiotherapy tape.

Immediately before and immediately after the experiment, the participants completed questionnaires to establish their mood. There were no differences between the two groups at the start. But on completing the experiment, those in the upright group reported feeling more positive and less fatigued - despite being held in an uncomfortable position during a stressful experience - than those in the slumped group.

The researchers used a number of methods to gauge how each participant was feeling, such as monitoring their blood pressure and heart rate. But the researchers were particularly interested in how the participants spoke. So each job interview speech was analysed using the Linguistic Inquiry and Word Count program, a tool that "analyses the emotional, cognitive, structural and process components of language".

"Basically, people with depression tend to speak less and more slowly than people who are not depressed," explains Elizabeth. "With this study we found significant differences between the two groups in the number of words they spoke and the types of words they used.

"For example, people with depression tend to use the words 'I' and 'me' more. What we found in this study was that when people were asked to be more upright, they actually used fewer of these personal pronouns.

"This tends to suggest that maybe it is making them less internally focused, and maybe that's a good thing."

Elizabeth and the team at the University of Auckland are not the only researchers examining the link between posture and well-being. In a joint effort by San Francisco State University, California, USA, and Kaohsiung Medical University, Taiwan, students were asked to recall happy and sad events while sitting in either an upright or slumped position.

According to the students, recalling happy events while seated in a slumped position was much more difficult than recalling sad events. And by monitoring electrical activity in the brain while a student was trying to recall happy and sad events, the researchers could confirm that the brain had to work harder to retrieve the happy events while the student was slumped.

However, sitting upright did not cause any of the students to be flooded with happy memories; they just had equal access to both happy and sad memories.

Another study, this time by Ohio State University, found that adopting an upright posture can give you more confidence in your own thoughts. When the study was published in 2009, professor of psychology at the university, Richard Petty, said: "Most of us were taught that sitting up straight gives a good impression to other people. But it turns out that our posture can affect how we think about ourselves. If you sit up straight, you end up convincing yourself by the posture you're in."

While the link between posture and mental well-being is still being explored, the link between posture and physical health is well established and well understood.

But despite this knowledge, according to physiotherapist Mairead O'Riordan, who runs TherapyXperts in Maynooth, Co Kildare, most of us have posture that's far from ideal.

Some posture issues are purely due to bad habits. For example, Mairead carries out a lot of workplace assessments in offices, and though the majority of office workers have the right equipment, most aren't using it correctly.

"When I do office assessments, I find that 90pc of staff do not have their bums in the back of the seat," she says. "Effectively, they're sitting on a stool. If you go to the pub to watch Ireland play and you only get a stool, by God, your back is sore by the end of the match."

But poor posture can also be caused by factors beyond our control - or knowledge. "We know that 14 out of every 100 people have some quirks in their bony architecture," explains Mairead. "It could be something as simple as a slight difference in angle in one hip joint. Or it could be a slightly malformed bone in the spine."

Most of these issues remain undiscovered unless they're picked up by an x-ray or by the trained eye of a physiotherapist.

Mairead has also seen evidence that quite a few of us are not as symmetrical as we appear to be. "The basic assumption is that we're relatively symmetrical," she says. "Your two arms should be approximately the same. Your two legs should be approximately the same. The muscle bulk around your shoulders should be approximately symmetrical, as should the muscle bulk around your bottom. But what we often see is that that is not the case."

However, the growth spurts of adolescence are a major contributor to poor posture. "In a growth spurt, bones grow first, and as they grow they stretch the muscles. And as the muscles are stretched, they become relatively incompetent for a period of time. During that period, an adolescent's posture can be horrible. But when the growth spurt ends, their posture improves as the muscles lay down extra cells to allow it to re-strengthen.

"For girls, growth spurts end when they're about 15-years-old. Boys continue to grow, skeletally, until the age of 23. So it's much more common to see boys with lousy posture."

One of the quirks of posture is that most of us are unaware that we have a problem. Even those suffering with neck and back pain may not associate those pains with their posture. Mairead says the best way to check your posture is to have someone photograph you sitting and standing. Better still, have someone video you walking and running - you can do it on a mobile phone.

For most of us, improving our posture is relatively simple, and Mairead has a couple of very effective techniques that she uses with her patients.

"First, sit on a stool and draw your head back until your earlobes fall behind your collarbone. Your eyes should be level and not turned to the sky. This will centre the weight of your skull on the architecture and muscles of the neck," she says, "allowing the muscles to move more equally around the neck."

Mairead recommends wearing some dangly earrings - if you have them - to help you line up your earlobe with your collarbone.

Her second technique is equally simple. "Gently slide your shoulder blades down towards the back of your hips. Just gently, slide them down. Hold for a few seconds. Then let go."

This exercise triggers the support muscles of the neck and spine and helps them to maintain good posture. It's particularly effective if done while walking.

"Repeat both exercise as often as you can," she says. "They will make a difference."

Mairead's tips will almost definitely provide physical benefits, but will they improve your mental wellbeing or protect you from stress?

Despite completing two very successful studies, Elizabeth Broadbent is reluctant to oversell her team's findings on posture and well-being. "It's a very interesting research area, but I wouldn't want to take these initial results and apply them too widely. Much more research will be needed before we can say that posture really has an effect," she explains.

"Much more work needs to be done with people who are seeing a clinician and who have a diagnosis of depression. We need to look at the effects of changing posture over both short and long time periods. And we need to see whom it works for and whom it doesn't work for.

"It's just interesting experimental research in its very early stages."

However, given how easy it is to make changes to your posture, and given the proven physical benefits if you do, not to mention the absence of side effects, it just might be worth trying.

Take a walk

Though primarily used as a method of rehabilitating heart and lung surgery patients, Physiotherapist Mairead O'Riordan believes timed walks are an excellent way to get started on improving your health, as follows:

* Starting at the front door of your home or office, walk as briskly as you can for six minutes.

* Stop. Make a note of how far you've walked

Turn on your heel and walk back to where you started. Your goal is to get back in six minutes.

Try to do this for four days in a row. You should notice that you're getting further each day on the outward leg of your walk.

* Increase the outward walk to seven minutes. As before, your goal is to get back to the start in seven minutes too. Continue for four days.

Continue this process, increasing the outward journey by one minute each time, until you reach 10 minutes.

* Once you've completed 10 minutes, you've completed the training period. Mairead says that you should now pick a nice spot, a park for example, and do 20-minute walks.