How much time would you say you spend sitting each day? Well if you’re the average person it’s about 8 hours, though some results estimate it can be as high as 15 hours. Not surprisingly, the number of sedentary jobs has increased by 83% since 1950; this coupled with a dramatic increase in total screen time (i.e. using computers, watching television, playing video games) contributes significantly to daily sitting time. Shockingly in a 65 year lifespan, you will have sat in front of the TV for over 9 years! Work sites, schools, homes, and public spaces continue to be developed in such a way as to minimise human movement and muscular activity. Excessive sitting, which is defined as anytime you sit for more than two hours per day, leads to what health professionals call ‘sitting disease’. It’s responsible for exacerbating 4 of the top 7 killers in the developed world; heart disease, cancer, stroke and diabetes, which ultimately leads to an overall shorter lifespan. The NHS advises 30 minutes of moderate activity a day for adults, but what about the other 15.5 hours of every day, assuming you get 8 hours of sleep? It’s important not to spend that time sitting down and here’s why.
Very few people are able to resist the urge to slump in their chairs whilst sitting. Although it may seem like a relatively innocuous and comfortable habit, the dangers of this hunched shape are very real. Firstly, sitting in this position opposes your spine’s natural S-shaped curve; anything different causes an imbalance within the spinal discs, generating uneven pressure and straining the surrounding muscles. Overtime these problems can become a permanent feature of our lives, developing into disorders such as kyphosis and lordosis. Furthermore, sitting in this crouched position with your head down and shoulders forward reduces your overall tidal volume by compressing your lungs. This results in less oxygen filtering into your blood and being transported around your body, which understandably leads to lower energy levels.
- Weight gain
Lipoprotein lipase is a special enzyme lining your capillaries, which is responsible for breaking down fat molecules as they pass through the blood. In the time it takes you to watch one episode of Brian Cox’s ‘Wonders of the Universe’, that’s about an hour of sitting, your body reduces its production of this fat-burning enzyme by up to 90%, so if you don’t reduce your caloric intake at that point then you’re going to gain weight. Additionally this will lead to your body’s cells becoming less responsive to insulin, which could lead to diabetes, obesity and even heart disease.
- Your Mind
Your brain requires both oxygen and a good flow of blood to remain alert, however bad posture and not moving around often enough will hinder these factors. This is why taking walks – especially in parks and around nature – is conducive to a creative, sharp and concentrated mind. Sitting down to study may feel like the norm, however you’ll be far more productive up on your feet. Obviously this isn’t always the most practical solution – you can’t exactly go wandering about in your lectures – so in this case, it’s just important to remember your posture and adjust it if need be.
In 2011, the CDC conducted a study among employees with sedentary jobs, who were made to give up their seats and remain on their feet all day. The results showed that throughout the course of the day, 87% of the respondents felt more energised, with 71% feeling more focused and 66% feeling more productive.
Just as exercising your body improves endurance and muscle size, sitting too often has the complete opposite effect – your muscles acclimate to being still. Overtime this can lead to what’s called disuse atrophy, which means that your muscles lose flexibility and mass whilst your bones lose density. This makes them brittle and can possibly lead to osteoporosis.
Telomeres are specialised protein structures that protect the ends of your chromosomes from deterioration, much like the plastic tips at the end of shoelaces. They naturally get shorter each time a cell replicates itself, until they become so short that the cells are unable to divide and die. In other words, the length of these tiny structures directly corresponds to your biological age. According to a recent study published in the British Journal of Sports Medicine, sitting down less often and standing up more can actually protect our DNA from ageing by lengthening telomeres, thereby increasing your lifespan.
A study based on a survey of 222,497 adults and published in the Archives of Internal Medicine concluded that prolonged sitting is a major risk factor for early mortality, no matter how much exercise you do. Sitting still for sustained periods of time takes its toll on your metabolic and vascular systems and increases your odds of a premature death. The researchers found that those who sat for more than 8 hours a day had a 15% greater risk of dying within 2.8 years than those who sat for fewer than 4 hours, whilst those who sat for more than 11 hours had a 40% greater risk! Additional evidence regarding the relationship between sitting time and mortality is limited; further studies are also needed to distinguish between the effects of sedentary behaviour and physical inactivity.
Unfortunately, there is currently not enough evidence to set a specific time limit on how long people should sit each day, but some countries such as Australia, the US and Finland, typically recommend about one to two hours a day. The American Medical Association agrees that sitting for extended periods of time can be bad for personal health and recommends that organisations offer sitting alternatives, including standing work stations and isometric balls. But even if your job doesn’t allow you to work outside the office or use a standing desk, standing up for just a few minutes every half an hour or so may reduce the risk of diabetes and heart disease by stimulating your metabolism and help counteract the adverse effects of a sedentary lifestyle.
From an evolutionary perspective, humans were designed to move and engage in manual labour throughout the day – inside us are over 360 joints and about 700 skeletal muscles that enable easy fluid motion. This was essential to our survival as a species. That’s not to say that sitting should be completely avoided. Short bouts of sitting can allow the body to rest and recuperate itself, especially after a long walk or an intense interval of exercise, however doing so all the time – behind your computer screen or on your couch watching TV – will ultimately hurt your mind and body.