Resources Library

ePublication of Australian Fitness Network

This week: Why it’s so hard to ignore the call of booze and burgers • It’s not that you sit, but how (and where) • Extreme exercise can strain without damaging the heart

Extreme exercise can strain without damaging the heart

Researchers have found no evidence of elevated cardiac risk in runners who completed a 24-hour ultramarathon (24UM), despite the transient elevation of blood biomarkers that measure cardiac health. According to the Brazilian study in the journal Heliyon, trained runners were more likely than their novice counterparts to experience raised levels, reflecting the greater cardiac load and pituitary-adrenocortical response to extremely strenuous exercise.

‘Experienced runners performed with greater intensity and speed, which placed strains on their hearts. Novice runners ran with less intensity, which resulted in lower cardiac biomarker levels’ explained co-lead investigator, Rodrigo Hohl, PhD, from the Federal University of Juiz de For a in Brazil. Hohl also noted that 24UM participants self-pace for a set time and towards an established endpoint. Runners with differences in training experience and competitive performances present variations in running speeds and, therefore, cardiac biomarker responses.

‘The good news is that while experienced runners pushed their heart limits during the ultramarathon, they did not show evidence of cardiac risk assessed through elevated biomarkers’ Hohl noted; ‘Novice runners appear to pace themselves well below their cardiac limit, self-selecting a safe pacing strategy for their hearts.’

The study examined the relationship between self-selected exercise intensity with cardiac biomarkers comparing experienced and novice runners able to finish a 24UM. Biomarkers that measure necrosis, inflammation, cardiac function/injury, and ischemia were used to understand the impact of acute exercise on the cardiac health of runners with different training levels and performance, including cortisol, total creatine kinase, C-reactive protein, and leukocyte levels. The findings showed higher levels of cortisol in the experienced group and confirmed previous research that cortisol is a good predictor of speed during a 24UM.

Although the study did not show clear evidence of cardiac risk when comparing cardiac biomarker levels with clinical cut-off values, it did establish that prolonged heart overload varies according to running speed. The wide range of ultramarathon distances and durations makes it challenging to generalise about cardiac risks and biomarkers response. Moreover, competitors modulate running intensity according to individual exercise tolerance and motivations to push themselves to increase levels of physical endurance, and little is known about the effect of extreme environmental conditions. Therefore, experienced ultramarathon runners should not consider themselves free of risk.

‘Our study provides evidence for caution and self-monitoring especially for experienced runners. After participating in an ultramarathon, runners should recover for at least two days before running any significant distance. This time is needed to normalise cardiac markers and allow the heart time to recover after such a challenge’ cautioned Hohl. A total of 25 runners participated in the study, which involved observation of a 24UM and blood tests before and after the event. Eleven runners in the experienced group had trained a distance of more than 100km a week over a five-year period. Fourteen novices had previously run at least one regular marathon, but had not participated in an ultramarathon. Exclusion criteria eliminated smokers and steroid users, as well as anyone with cardiovascular or metabolic disease or musculoskeletal injury from the study group.

Source: Elsevier


It’s not that you sit, but how (and where)

Sitting for long periods of time has been linked to increased risk of cardiovascular disease and early death, but a new study suggests that not all types of sitting are equally unhealthy.

The study, published online in the Journal of the American Heart Association and led by researchers at Columbia University Vagelos College of Physicians and Surgeons, found that leisure-time sitting (while watching TV), but not sitting at work, was associated with a greater risk of heart disease and death among the study’s more than 3,500 participants. The study also found that moderate-to-vigorous exercise may reduce or eliminate the harmful effects of sedentary television watching.

‘Our findings show that how you spend your time outside of work may matter more when it comes to heart health’ said study author Keith Diaz, PhD, assistant professor of behavioural medicine at the college, and a certified exercise physiologist; ‘Even if you have a job that requires you to sit for long periods of time, replacing the time you spend sitting at home with strenuous exercise could reduce your risk of heart disease and death.’

A growing body of research shows that people who are sedentary – especially those who sit for long, uninterrupted periods of time – have a higher risk of cardiovascular disease and death.

But most previous studies did not follow people over time, making it difficult to draw conclusions about the relationship between sedentary behaviour and health risk. These studies have included mainly people of European descent rather than African Americans, a group that has a higher risk of heart disease. Previous studies also measured physical activity using an activity monitor, which is unable to distinguish between different types of sedentary behaviour.

The new study followed 3,592 people, all African Americans, living in Jackson, Mississippi, for almost 8.5 years. The participants reported how much time they typically spent sitting while at home watching TV and during work. They also reported how much time they spent exercising in their down time.

The participants who had logged the most TV-viewing hours (four or more hours a day) had a 50% greater risk of cardiovascular events and death compared to those who watched the least amount of TV (less than two hours a day).

In contrast, those who sat the most at work had the same health risks as those who sat the least.

Even for the most dedicated TV watchers, moderate to vigorous physical activity – such as walking briskly or doing aerobic exercise – reduced the risk of heart attacks, stroke, or death. No increased risk of heart attack, stroke, or death was seen in people who watched TV for four or more hours a day and engaged in 150 minutes or more of exercise a week.

In a previous study, Diaz found that excessive sitting is linked to worse health outcomes and even more so when sitting occurs in lengthy, uninterrupted bouts.

‘It may be that most people tend to watch television for hours without moving, while most workers get up from their desk frequently’ Diaz said; ‘The combination of eating a large meal, such as dinner, and then sitting for hours, could also be particularly harmful.

‘More research is needed, but it’s possible that just taking a short break from your TV time and going for a walk may be enough to offset the harm of leisure-time sitting’ added Diaz; ‘Almost any type of exercise that gets you breathing harder and your heart beating faster may be beneficial.’

Although occupational sitting was less problematic, Diaz noted that the same approach to movement applies at work; ‘We recognise that it isn’t easy for some workers, like truck drivers, to take breaks from sitting, but everyone else should make a regular habit of getting up from their desks. For those who can’t, our findings show that what you do outside of work may be what really counts.’

The researchers suspect that the study’s findings may be applicable to anyone who is sedentary, even though the study focused on African Americans.

Source: Columbia University Irving Medical Center


Why it’s so hard to ignore the call of booze and burgers

A UNSW psychology experiment has shown why it can be so hard to direct our attention away from cues that might lead to behaviour we’d like to avoid, like drinking alcohol and eating unhealthy food.

If you’re stressed, tired or otherwise straining your brain power, you may find it harder to ignore cues in the environment, like advertising, that signal something rewarding.

That’s what a UNSW Sydney experiment by a group of psychologists – published in journal Psychological Science – has shown.

‘We knew already that participants find it hard to ignore cues that signal a large reward’ said study lead Dr Poppy Watson at UNSW.

This experiment, however, showed, for the first time, that ignoring these cues became harder as soon as participants had to perform a task while also holding other information in their memory.
‘We have a set of control resources that are guiding us and helping us suppress these unwanted signals of reward. But when those resources are taxed, these become more and more difficult to ignore’ Watson said.

Up until now, researchers didn’t know whether people’s general inability to ignore reward cues is just something we have no control over or whether we do use our executive control processes to constantly work against distractions. Now it’s become clear that the latter is the case – although unfortunately this resource is limited.

Executive control is a term for all cognitive processes that allow us to pay attention, organise our life, focus, and regulate our emotions.

‘Now that we have evidence that executive control processes are playing an important role in suppressing attention towards unwanted signals of reward, we can begin to look at the possibility of strengthening executive control as a possible treatment avenue for situations like addiction’ said Watson.

In the experiment, participants looked at a screen that contained various shapes, including a colourful circle. They were told they could earn money if they successfully located and looked at the diamond shape, but that if they looked at the coloured circle – the distractor – they would not receive the money.

They were also told that the presence of a blue circle meant they’d gain a higher amount of money (if they completed the diamond task) than the presence of an orange circle. The scientists then used eye tracking to measure where on the screen participants were looking.

‘To manipulate the ability of participants to control their attention resources, we asked them to do this task under conditions of both high memory load and low memory load’ Watson said.

In the high-memory load version of the experiment, participants were asked to memorise a sequence of numbers in addition to locating the diamond, meaning they had fewer attention resources available to focus on the diamond task.

‘Study participants found it really difficult to stop themselves from looking at cues that represented the level of reward – the coloured circles – even though they were paid to try and ignore them’ Watson said.

‘Crucially, the circles became harder to ignore when people were asked to also memorise numbers: under high memory load, participants looked at the coloured circle associated with the high reward around 50% of the time, even though this was entirely counterproductive.’

The findings demonstrate that people need full access to cognitive control processes to try and suppress unwanted signals of reward in the environment.

‘This is especially relevant for circumstances where people are trying to ignore cues and improve their behaviour, e.g. consuming less alcohol or fast food’ said Watson.

‘There’s this strong known link between where your attention is and what you eventually do, so if you find it hard to focus your attention away from reward cues, it’s even harder to act accordingly.

That also explains why people might find it harder to focus on dieting or beating an addiction if they are under a lot of stress.

‘Constant worrying or stress is the equivalent to the high-memory load scenario of our experiment, impacting on people’s ability to use their executive control resources in a way that’s helping them manage unwanted cues in the environment.’

Watson advised people to try and be strategic about exposure to cues; ‘If you are under a lot of cognitive pressure (stress, or tiredness) you should really try and avoid situations where you’ll be tempted by signals. You need to be in the right frame of mind to be in a situation where you can stop yourself from getting distracted and going down a path where you don’t want to go’ she said.

The researchers now want to look at how executive control can be strengthened – and if that presents an opportunity for situations like drug rehab.

‘Our research suggests that if you strengthen executive control you should have better outcomes. Some studies have already demonstrated that training executive control can reduce the likelihood that you will eat chocolate or drink alcohol. And in the clinic, training focus away from pictures of alcohol towards soft drinks has been shown to reduce relapse in alcoholic patients’ Watson said.

Source: University of New South Wales

Member Only Content