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Couch Potatoes vs Iron Men

05 Oct 2017

Exercise has been proposed as both a preventative measure and cure for a range of diseases for millennia, with the first recorded prescription for exercise made in 600 BCE. With an ever-growing array of research into new ways in which exercise can be advantageous, or how different types of exercise can have different effects on our bodies, why aren’t we doing  more?

The increase in office jobs, sedentary hobbies, and less arduous methods of transport than walking, means that people are much less active than is recommended – a recent Public Health England report found that 41% of middle-aged English people walk for less than 10 consecutive minutes in a month.

The World Health Organization recommends that adults do at least 150 minutes of moderate-intensity physical activity (exercise which raises your heart rate) each week, but in 2010 more than one in five of adults were not achieving this.


Why bother?

Few people would disagree that, generally speaking, exercise is good for us. But with the wide variety of exercises available, and different ways to measure health benefits, what are the specifics? Jerome Fleg recently published a review on the effects of high intensive interval training (HIIT) – a style of aerobic exercise which involves short bursts of intense “all out” exertion, with periods of lower intensity exercise in between to allow recovery. As free time becomes more precious, this type of exercise may be an efficient way for people to stay physically fit.

The review collates numerous studies which found that HIIT had a positive effect on issues including high blood pressure, obesity, and cardiovascular disease. It also increased the maximum rate that oxygen was consumed in healthy adults – a common measure of physical fitness. However, it isn’t just physical fitness that exercise affects in healthy people – it can also protect against some types of cancer.

There is a large body of evidence that physical activity reduces the risk of colorectal cancer, with the risk of colon cancer dropping by 20-25%. Vikneswaran Namasivayam and Sam Lim discuss the links between exercise and colorectal cancer in a recently published Faculty Review, providing a comprehensive summary on how physical activity, or lack of, influences the possibility of developing colorectal cancer.

There are many studies demonstrating how exercise results in a decreased risk of colon cancer but the relationship with rectal cancer is less clear, although a recent meta-analysis found that moderate levels of exercise do reduce the risk – this is likely due to the effects of exercise on your cardiovascular fitness, which has also been determined to have a protective effect.

Interestingly, Namasivayam and Lim also highlight evidence that sedentary activities like watching TV or sitting at a desk increase the risk of colorectal cancer independent of whether or not someone also exercises. High levels of physical activity (defined as over an hour of moderate exercise a day) appear to counteract the overall health risks of sedentary behaviour, but the effect upon on colorectal cancer specifically is not yet known.

Keeping Fit

Exercise is also important with regards to maintaining muscle strength – as we get older it becomes more likely that we will develop sarcopenia, one of the main aspects of frailty. Sarcopenia is where the muscles begin to shrink, and whilst it is associated with inactivity even people who had an active lifestyle when younger may be affected. There are obviously many reasons why this is unwanted – from loss of strength to reduced independence – and researchers are searching for ways to prevent or even restore this muscle loss.

Jessica Cegielski and her colleagues were aware that resistance exercise training can improve muscle mass after the onset of sarcopenia, however the problem is that this requires both access to a gym and the motivation to actually stick to an exercise program. Instead, they hypothesised in their article that is currently under review that many more people would stick to an exercise program if it could be performed at home alongside normal household activities, for example lunging with your shopping bags or doing bicep curls as you cook.

The researchers enrolled a small number of healthy adults in their 60s to follow a 4-week exercise plan – while nobody followed the plan completely, the self-reported logs showed an 87% compliance. This figure is much higher than the 38% who manage to meet the recommended levels of physical activity in general. The team used a number of indicators to determine whether the exercise regime had an effect on the overall fitness and musculature of the participants, ranging from cardiovascular measurements to the length and thickness of the exercised muscles.

Over the 4 weeks, there was no significant changes to heart rate or blood pressure – this could be due to the exercises being anaerobic rather than aerobic in nature, or the short duration of the study. This is in contrast to studies highlighted by Jerome Fleg’s review, which investigated aerobic exercise over longer periods of time. Cegielski et al. observed that whilst muscle mass didn’t increase significantly – either in the exercised muscles or as a whole – there was a positive trend overall and the strength of the exercised muscles was increased, which is arguably the most important aim of the exercise plan.

Participants had to complete three sets of twelve repetitions for each exercise every day, which at six seconds per exercise quickly adds up to just over 200 minutes if the plan is adhered to, easily meeting the WHO recommendations for physical activity.

The Extreme

While many people don’t get the 150 minutes of exercise a week that’s recommended, others go above and beyond. Forget conventional marathons, Ironman triathlons are an extreme triathlon where contestants swim 2.4 miles, cycle 112 miles, and then finish up with a full length marathon on foot. However, extreme levels of exercise have their perils too – Hae-Rang Yang and colleagues helped with planning and providing the medical support for the Ironman 70.3 Busan race held in South Korea, a half Ironman that took place in 2016.

They recorded the injuries that occurred during each section of the race, and those sustained by the staff and supporters. Of the 765 athletes who took part in the race, just over 20% were treated by the medical team, although it’s important to note that some of these injuries could have been caused or exacerbated by the hot weather.

The vast majority of the injuries suffered were muscle pain, which isn’t surprisingly during such extreme conditions, and occurred during the final leg of the race – the most serious injuries were during the cycling where 5 people required a trip to hospital, however the article implies this was the result of collision rather than exercise-induced injury.

Needless to say, the athletes participating are incredibly physically fit – while determining the ideal conditions for a person to be successful. In Ironman triathlons, Beat Knechtle and colleagues found that Ironman athletes were training for around 14 hours a week. That’s 120 minutes of intensive exercise a day!


Click here to view the full article which appeared in F1000 Research