⭑ Prolonged sitting is bad ✔ but some scientists say exercise fixes it
⭑ Two studies - two opposing conclusions ✔ here's what you need to know
⭑ Less argument here: dementia correlated with prolonged sitting ✔
⭑ Harnessing the power of eccentric movements ✔ strength
Sitting - the 8th deadly sin?
My eyes boggled when I read contradictory health advice on the one day this week about a very specific topic - prolonged sitting.
I've covered it all in this newsletter for you. You'll learn whether exercise ameliorates the significant health problems caused by prolonged sitting, or not. And what you should do to forestall dementia-related effects from sitting too long - see item #3.
When medical population research yields contradictory conclusions it is hard to know what action to take. Here's how to understand the contradictions about prolonged sitting and the benefits of exercise - see item #2.
Well-cited studies find that exercise does not offset the health problems caused by prolonged sitting. But a new study contradicts them - see item #1.
01 Exercise Does / Does Not Counteract Prolonged Sitting
Prolonged sitting: "Exercise does not offset health risks", or does it? As Shakespeare would say - to exercise or not to exercise.
I was struck by two headlines I saw this week. "Exercise does not offset health risks", says the AHA, and "How 22 minutes of exercise a day could reduce health risks from sitting too long", says another.
Many research studies have highlighted the concerning health risks associated with prolonged sitting. Mayor (2015) found that regardless of physical activity levels, sitting for extended periods increases the risk of developing cardiovascular disease, type 2 diabetes, and cancer.
Younger (2016) discovered that moderate exercise before prolonged sitting did not relieve the adverse effects on cardiometabolic function. Lurati (2018) examined the hazards of prolonged sitting and sedentary behaviour, underscoring the significance of reducing sitting time, even for those regularly exercising.
From these, we can conclude that individuals who meet the recommended levels of moderate-vigorous physical activity (MPVA) but spend most of their waking hours in sedentary activities may have compromised health.
On the other hand...
In contrast, a very new study (October 30, 2023) found that higher levels of MVPA were associated with a lower risk of mortality, regardless of sedentary time.
This study involved 11,989 participants aged 50 years and above. Physical activity and sedentary time were measured using hip accelerometry. The analysis adjusted for various factors and aimed to determine associations between physical activity, sedentary time, and other factors using statistical methods.
The analysis found that 22 minutes of MVPA per day eliminates the association between sedentary time and mortality risk. This implies that individuals who accumulate sufficient MVPA may mitigate the adverse effects of prolonged sitting on their health outcomes.
What this means for you: How do we reconcile the differences, and what action do we take?
I view it as I view insurance and the risk-reward for the effort (for the cost). For example, let's say I am reasonably convinced by the studies finding that exercise does not reduce the risks of prolonged sitting.
Will I stop exercising, and sit for longer? No. Even with this belief, I will still reduce my sitting times and exercise more.
Why? Because let's say that in 10 years time research reveals with certainty that regular exercise does counter the adverse effects of prolonged sitting. By then it's a bit late for me to take action if I have been inactive for those 10 years.
⇒ In other words, the effort required to be more active, to reduce your sitting period, and accumulate 22 minutes of exercise a day, is not a high price to pay even if this is ultimately proven to be ineffective.
Coming to the opposing results from the studies: the variation in findings could be due to differences in the study designs, population samples, or methodologies used in the two studies. I'll discuss this in the next section.
02 How To Reconcile Opposing Research Results, and What To Do
As mentioned, the variation in findings could be due to differences in the study designs, population samples, or methodologies used in the two studies.
While Mayor (2015) emphasises the negative impact of prolonged sitting on health outcomes, the 2023 study highlights the potential benefits of engaging in MVPA (moderate-vigorous physical activity) even in the presence of long sedentary time.
In both studies participants used devices, such as accelerometers, to measure their sitting and active phases. So we can conclude that the different study outcomes where not due to basic record-keeping differences.
What does differ, upon close scrutiny, is the lack of distinction between physical activity and fitness. This is crucial, especially for older adults.
Physical activity refers to any bodily movement that expends energy, while fitness is a state of well-being where one has adequate endurance, strength, and flexibility to navigate daily tasks efficiently.
What does this mean for you? My belief is that the contradictory study results underscore the notion that a balanced approach to fitness which transcends mere physical activity and promotes a holistic approach to health could significantly mitigate the health risks associated with prolonged sitting.
The studies that found no benefits from exercise generally measured "activity", whereas the 2023 "positive benefits of exercise" study measured moderate-vigorous physical activity.
Moderate-vigorous intensity activities are those that get you moving fast enough or strenuously enough to burn off three to six times as much energy per minute as you do when you are sitting quietly. Think of a friendly soccer game, jogging, or a game of tennis singles. For these, you require "fitness".
⇒ The best measure of your chances of offsetting the negative effects of prolonged sitting is your level of overall fitness. This includes strength training, flexibility, using resistance bands, jogging, running, swimming, balance and interval training, for example.
And remember to set your timer and stand up every 25 minutes or so, take some deep breaths, and walk around the block every now and then when you can.
Related (older blog posts of mine): How To Go From On-knee to Full Pushups, and Reap The Benefits
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03 Sitting All Day Increases Dementia Risk — Even If You Exercise
While the jury is out on prolonged sitting and longevity, a new study found that sitting all day increases the risk of dementia, even if a person exercises regularly.
- This 2023 study found that prolonged sitting increases the risk of developing dementia.
- The negative effects of sitting for long hours are even strong for those who exercise regularly.
- The study involved over 49,000 men and women aged 60 or older and found that sedentary behaviour increases the risk of dementia.
- Sitting for at least 10 hours a day raised the risk of dementia by 8%, while sitting for at least 12 hours a day raised the risk by 63%.
- The study also found that exercise does not undo the risks of sitting, but taking short breaks and reducing overall sitting time can help lower the risk.
To put it into perspective, compared to individuals who spent a median of 9.27 hours per day being sedentary, those who spent 10 hours showed an 8% higher risk of dementia. Furthermore, those who spent 12 hours had a 63% higher risk, while individuals spending 15 hours were at a staggering 221% higher risk of developing dementia.
⇒ The link between prolonged sitting and dementia is unknown, although there are suggestions that cerebral blood flow is affected, reducing the brain’s supply of oxygen and fuel.
What this means for you: While it's unsurprising that spending more time being sedentary is associated with a higher risk of dementia, this study also found that the length of sedentary bouts played a role.
Long periods of physical inactivity are associated with an increased risk of dementia, not just the total time spent being sedentary. Therefore, best to:
- Break Up Your Sedentary Time: Avoid sitting or lying down for long periods without taking breaks. Aim to get up and move around every hour, even if it's just for a few minutes - jump up at each 3rd or 4th ad break if watching TV.
- Stand Up and Stretch: If you have a desk job or spend a lot of time sitting, make it a habit to stand up and stretch at regular intervals. This can help break up your sedentary time and improve circulation.
- Use devices to set timers - to stand every 25 minutes, for example. I do this.
Breaking up long periods of inactivity is a small effort if it fends off dementia.
04 Avoiding Hip Pain - The Iliopsoas Muscle
Our exercise of the week is... stretching and strengthening the iliopsoas muscles.
An iliopsoas strain is one of the most common overuse injuries from frequent running or jumping. This typically manifests as a sudden, sharp pain or a pulling feeling in the front of the hip or groin.
This happens when lifting the knee towards the chest or during activities like walking, climbing stairs, or transitioning from sitting to standing. The latter is the clue!
Although it is "common knowledge" that "sitting shortens our hip muscles", which makes it harder to stand, this is not true. Our two largest "hip muscles" - hamstrings and quadriceps "quads" - remain the same length whether we stand or sit.
Sitting doesn't shorten our major hip muscles, except for the iliopsoas muscle.
In a seated position, the iliopsoas is in a relatively shortened position. As we stand, it extends and stretches - and thus feels tight. Ignoring this chronic tightness from extended sitting increases the chance of an iliopsoas straining while exercising.
What this means for you: We can strengthen and stretch our iliopsoas, reducing the chance of injury, but we must target it accurately.
For example, standing and bending the knee to bring the heel towards the buttock doesn't stretch the hip flexors as much as it stretches the quadriceps muscles.
To target the iliopsoas muscle, we need to perform a stretch that tilts our pelvis down to extend the hips:
Lunging Hip Flexor Iliopsoas Stretch (video):
- Start in a lunge position with your left foot forward and right knee on the ground.
- Keep your upper body upright and engage your core.
- Slowly lean forward while maintaining a slight tilt of your pelvis to feel a stretch in the front of your right hip.
- Hold for 30 seconds to 1 minute and then switch sides.
Standing Iliopsoas Stretch (video):
- Stand upright with your feet hip-width apart.
- Take a step forward with your right foot, keeping your left leg straight.
- Bend your right knee and tilt your pelvis forward, pushing your hips slightly forward.
- (Clasp your hands and bring both arms up and over your head to extend your pelvic tilt forward - not in the video).
- Feel the stretch in your left iliopsoas muscle.
- Hold for 30 seconds to 1 minute and then switch sides.
Or try the yoga-standing psoas stretch, which is simple and effective.
Thanks for reading!
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