Tag Archives: Exercise

Exercise now, thank yourself later

by Glenn Wadley, Associate Professor, Institute for Physical Activity and Nutrition (IPAN), Deakin University, Australia.

Endurance exercise and healthy hearts

A wealth of evidence shows that physical activity helps prevent heart disease and all causes of mortality (1) and has benefits for the heart at any age (2): aerobic exercise – often referred to as ‘cardio’ – and in particular endurance-training, is beneficial to the heart. But these effects – in adults – are only temporary and lost soon after training is stopped (3-5). Because of this, it has been assumed until now that the beneficial effects of exercise for the heart are also temporary for young and adolescent mammals, including humans.

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The athlete’s heart – when big is beautiful

Moderate levels of endurance exercise training improve the structure and function of the heart, and makes it grow larger, resulting in what is called athlete’s heart, or physiological cardiac hypertrophy (3-5). This larger heart is beneficial and quite distinct from the enlarged hearts observed in disease, which display reduced function, and increased scarring and molecular and structural differences, in addition to heart failure and increased mortality (6). In contrast, athlete’s heart can improve quality of life, since people with a physiologically healthy, bigger heart will pump more blood and thus can train harder at any given age (7). This effect is of particular benefit as adults get older.

The workhorse cells of the body – cardiomyocytes

 In the heart, specialised muscle cells do the heavy lifting: they are called cardiomyocytes, and are highly resistant to fatigue. The adult human heart contains several billion cardiomyocytes and their coordinated contraction produces around 100,000 heartbeats per day, every day.

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Cardiomyocytes up close.

Until recently, we thought that the number of cardiomyocytes in mammals’ hearts was fixed shortly after birth. Adult cardiomyocytes don’t get renewed or multiply much, so we thought that the heart grew larger in response to training because the existing cardiomyocytes grew larger, rather than because there were more of them.

However, our recent study has established that an increase in cell number also plays a considerable role in cardiac growth in response to just four weeks of moderate intensity exercise, if the training is conducted during juvenile life, which is 5-9 weeks of age for a rat. This training period would be equivalent to late childhood and puberty in humans. We also found that this effect of exercise on cell number diminishes with age and is lost by adulthood. Indeed, when the same exercise training program is conducted in adolescent rats (11-15 weeks of age, or around the time of late puberty and reproductive maturation in humans), there is a much smaller impact on cardiomyocytes multiplying. In adult rats, heart mass and cardiomyocyte size still increase following exercise training, but without any increase in cardiomyocyte number. Clearly, endurance exercise is beneficial for the heart at any age, but it appears that a window of time exists in the younger heart whereby exercise might be able to grow more cardiomyocytes.

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With regards to the benefits of juvenile exercise for the heart, perhaps the most compelling finding is that the increased heart mass and around 40% increase in cardiomyocyte number remain well into adulthood. What’s more, this increase in cell number is sustained despite the rats being couch potatoes for a prolonged period of time – the equivalent of 10 years in humans! Having more cardiomyocytes potentially makes the heart better equipped for the structural and functional challenges of adult life. For example, in the UK, the 915,000 survivors of heart attack (8) are left with a heart containing up to 25% fewer cardiomyocytes (9) that are not replaced, along with a large degree of scarring and fibrosis. Thus, having more cardiomyocytes saved up for a rainy day could be a handy reserve if you are unfortunate to suffer a cardiac event.

There are already plenty of good reasons to exercise regularly and we know exercise is beneficial for heart health at any stage of life. However, should these recent findings translate to humans they would provide a new reason to ensure there are sufficient opportunities for children to engage in regular physical activity in school curricula. Importantly, our research suggests that there may be long-term cardiac benefits of physical activity for all children, even if the children do not continue with regular exercise in adulthood. Unfortunately, we know the majority of children do not meet physical activity recommendations (10) and therefore their hearts may be missing out on the best start to life.

References:

  1. G. Erikssen, Sports medicine (Auckland, N.Z), 2001, 31, 571-576.
  2. S. Lachman, S. M. Boekholdt, R. N. Luben, S. J. Sharp, S. Brage, K. T. Khaw, R. J. Peters and N. J. Wareham, Eur J Prev Cardiol, 2017, DOI: 10.1177/2047487317737628.
  3. O. J. Kemi, P. M. Haram, U. Wisloff and O. Ellingsen, Circulation, 2004, 109, 2897-2904.
  4. R. C. Hickson, G. T. Hammons and J. O. Holloszy, Am J Physiol, 1979, 236, H268-272.
  5. D. S. Bocalini, E. V. Carvalho, A. F. de Sousa, R. F. Levy and P. J. Tucci, Eur J Appl Physiol, 2010, 109, 909-914.
  6. B. C. Bernardo and J. R. McMullen, Cardiology clinics, 2016, 34, 515-530.
  7. R. J. Shephard, British journal of sports medicine, 1996, 30, 5-10.
  8. British Heart Foundation, BHF CVD Statistics Factsheet – UK, https://www.bhf.org.uk/statistics
  9. M. A. Laflamme and C. E. Murry, Nature, 2011, 473, 326-335.
  10. Australian Bureau of Statistics, Australian Health Survey: Physical Activity, 2011-12. 2013. http://www.abs.gov.au/AUSSTATS

 

The Myth of a Sport Scientist

Back in school, I was a sporty student taking part in a plethora of activities from netball and hockey, to kayaking, tennis and 1500m, but I was never keen on becoming a professional athlete. I was always nominated for the sport day events and typically took charge as captain. When looking at my A-level choices and what career to follow, I naturally pursued the sport route, aligning with topics such as physical education and biology.

Then, when it came to higher education, studying sport science was at the top of my list. Whilst visiting institutional open days, and speaking to friends, family and teachers, it became apparent that there was a mismatch between the perceptions of what a sport scientist is about and what skills it entails. Here I present some top common misconceptions of being a sport scientist.

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Myth #1: You have to be an elite sportsperson

This is my pet hate and the main myth I try to debunk! It is not true that a sport scientist has to be good at sport; yes it can sometimes help to have an interest in physical activity, exercise or sport, but you don’t have be a Messi or Ronaldo. The whole benefit of studying sport science is that you can inspire anyone from the inactive to the elite. Studying sport science is more about being interested in the application of science to the interpretation and understanding of how the body responds to exercise. It involves expertise across a range of scientific disciplines including physiology, psychology, biomechanics, biochemistry, anatomy, and nutrition.

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Myth # 2: You are either a physical education teacher or a coach

Another persistent myth about being interested in sport and studying sport science is that you run around a rugby pitch with a whistle. As much as I respect the talents and skills of PE teachers and coaches, and although many of our students may go into these careers, these are not the only skills and applications of a sport scientist. Sport scientists can be performance analysts. Or they may specialise in exercise physiology. They may even go into marketing, rehabilitation, PR, sport media, or education. The diversity and depth of transferable skills means that there are a variety of options and directions to take, whether you want to help improve the health and wellbeing of a population through exercise plans or the recovery of injured athletes. I always had an interest in teaching sport or science. It was during my PhD that I became aware of the opportunities and careers in academia. Then, becoming a lecturer became my focus, combining my love of the subject and passion for the research!

Finally, Myth #3: It’s not a ‘real’ science

This final myth really bothers me, and is most applicable to the research aspect of my job. It can be frustrating when we are not as respected in the field of science, where some say it’s not a ‘real’ science’. Many of us who are in the field of sport science are specialised in a discipline. For me, it was exercise physiology and biochemistry.

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As an exercise physiologist, I am specifically interested in the relationship between the use of exercise as a stressor and how the body responds at a cellular level with specific use of biochemical and immunological analytical techniques. Just because we use models of sport performance, exercise bouts or physical activity sessions, doesn’t mean that there aren’t complex scientific skills, theories, analytics and techniques behind the work. My primary research focuses on how the immune system and metabolism help our skeletal muscles repair after physical activity, exercise, and training. My current research is about ultra-endurance running profiling of endurance performances, rehabilitation techniques for muscle damage and inflammation, and the use of exercise plans in management of diseases such as type 2 diabetes.

With the developments and interest in sport across the nation following events such as the 2012 and 2016 Olympics, and other events such as Wimbledon, the Football leagues and the Rugby World Cup, hopefully people are starting to realise how sport science can advance sport performance and health.


Dr Hannah Jayne Moir is a Senior Lecturer in Health & Exercise Prescription, at Kingston University, London. Her research is driven in the discipline of Sport & Exercise Sciences and she is co-chair and theme leader for the Sport, Exercise, Nutrition and Public Health Research Group.

This post is part of our Researcher Spotlight series. If you research, teach, do outreach, or do policy work in physiology, and would like to write on our blog, please get in touch with Julia at jturan@physoc.org.

Diet, exercise or drugs – how do we cure obesity?

by Simon Cork, Imperial College London, @simon_c_c

October 11th is officially “World Obesity Day”, a day observed internationally to promote practical solutions to end the obesity crisis. The term “obesity crisis” or “obesity epidemic” is often repeated by the media, but how big is the problem? Today, over 1.9 billion adults worldwide are overweight or obese. By 2025, this is projected to increase to 2.7 billion with an estimated annual cost of 1.2 trillion USD. Of particular concern is that 124 million children and adolescents worldwide are overweight or obese. In the UK, this equates to 1 in 10 children and adolescents and is projected to increase to 3.8 million by 2025. We know that obesity significantly raises the risk of developing 11 different types of cancer, stroke, type 2 diabetes, heart disease and non-alcoholic fatty liver disease, but worryingly, we now know that once someone becomes obese, physiological changes to the body’s metabolism make long-term weight loss challenging.

Our understanding of the physiology of food intake and metabolism and the pathophysiology of obesity has grown considerably over the past few decades. Obesity was seen, and often still is seen, as a social problem, rather than a medical issue: a lack of self-control and willpower. We now know that physiological changes occur in how our bodies respond to food intake. For example, hormones which are released from the gut following food intake and signal to the brain via the vagus nerve normally reduce food intake. However, in obesity, the secretion of these hormones is reduced, as is the sensitivity of the vagus nerve. The consequence of this is a reduced sensation of feeling full.

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Imaging of the hypothalamus (a key region for keeping food intake at a balanced level) shows a reduction in activity following food intake in lean men, an effect which was absent in obesity. This effect may relate to a reduction in the body’s responses observed following food intake in obesity, such as balancing blood sugar and signalling that you are full. Furthermore, numerous studies have shown that obese individuals have a reduced availability of dopamine receptors, the structures on cells that respond to the pleasure chemical dopamine, in key brain regions associated with reward. Whether the reduction in dopamine receptor availability is a cause or consequence of obesity remains to be fully explored, but it is likely to be a combination of both of these factors. Individuals with a gene called the Taq1 A1, associated with a decreased availability of dopamine receptors, are more likely to become obese, suggesting that decreased responsiveness to high calorie foods leads to increased consumption in order to achieve the same level of reward. (Interestingly, this same gene is also associated with an increased risk of drug addiction). However, much like drug addiction, hyper-stimulation of the dopamine system (i.e. by consuming large quantities of dopamine-secreting, high calorie foods) can in turn lead to a reduction in dopamine receptor levels, thus creating a situation where more high calorie foods are required to stimulate the same level of reward.

It is therefore clear that obesity is not simply a manifestation of choice, but underpinned by complex changes in physiology which promote a surplus of food consumption, called positive energy balance. From an evolutionary standpoint, this makes sense, as maintaining a positive energy balance in times of abundant food would protect an individual in times of famine. However, evolution has failed to keep up with modern society, where 24-hour access to high calorie foods removes the threat of starvation. The good news is that we know that weight loss as small as 5% can yield significant improvements in health, and can often be managed without significant modification to lifestyle.

 

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Presently, treatment options for obesity are limited. The first line treatment is still diet and exercise; but as the above examples of how our physiology changes show, maintaining long term weight loss through self-control alone is almost always impossible. However, the future does look bright, with new classes of drugs either recently licenced, or in production. Saxenda (a once-daily injectable drug which mimics the gut hormone GLP-1 made by Novo Nordisk) has recently been licenced for weight loss in patients with a BMI greater than 30. However, after 56 weeks treatment, average weight loss was a modest 8kg. Likewise Orlistat (which inhibits absorption of dietary fat, made by Roche) has been on the market for a number of years and shows average weight loss of around 10%. However, it is associated with unpleasant side effects, such as flatulence and oily stools. Presently, bariatric surgery is the only treatment that shows significant, long term weight loss (around 30%, depending on the surgical method used) and is also associated with long-term increases in gut hormone secretion and vagus nerve sensitivity.  Research is currently underway to assess whether the profile of gut hormones observed post-surgery can be mimicked pharmacologically. Studies have shown that administering select gut hormones in combination results in a reduction in body weight and food intake greater than the sum of either hormone when administered in isolation. This observed synergy between gut hormones will undoubtedly form the basis for future pharmacotherapies with improved efficacy, with various combinations currently in both clinical and pre-clinical trials.

For healthcare policy makers, the future obesity landscape does not make for happy reading. A combination of better therapies and improved public health messages are undoubtedly needed to stem the rising tide. However, both policy makers and society as a whole should be mindful that changes in ones physiology mean maintaining long-term weight loss through diet and exercise alone are unlikely to be the whole answer.

Spinning Out of Control? Public Engagement at SPIN Cycle Festival

By Daniel Brayson, @drdanbrayson

SPIN cycling festival, a celebration of all things cycling, took place on the weekend of 12 May 2017 at the Olympia in Kensington, London. Here at The Physiological Society, we thought it would be the perfect opportunity to showcase the wonders of physiology, using funding from The Society’s Public Engagement Grants.

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The premise of our activity was to find some anecdotal dogma, which is prevalent in sports like cycling, and disprove it. Put simply, we went on a myth-busting mission.

A popular assumption among amateur cycling enthusiasts is that it is good to cycle at a high cadence. Discarding the jargon, this essentially means pedalling really fast. Many people think this because successful professional athletes such as Chris Froome, and previously Lance Armstrong, cycled at very high cadences when they were racing in huge competitions such as the Tour de France, the most famous cycling race in the world.

We based our experiment on a paper in one of The Society’s journals, Physiological Reports, from 2015 by Formenti and colleagues titled Pedalling rate is an important determinant of human oxygen uptake during exercise on the cycle ergometer. What the paper essentially showed is that the faster you pedal for a given work rate, the more energy you use.

Bike like the wind

With this in mind, we set out to perform some live experiments on festival-goers. We set up a bike on a smart turbo trainer with a computer that we could use to read measurements. We recruited many willing volunteers over the course of the weekend, fitting them with a device to measure heart rate, and setting them up on the bike.

Using the smart turbo trainer, we set the amount of work that the volunteers would do to 150 watts of power and placed headphones on them. They then sat for 1 minute before beginning to cycle in time with a metronome, or a clicking sound, that was playing through the headphones. We changed the speed of the click at set intervals which meant that the volunteer would change their cadence accordingly. At each cadence, we recorded the heart rate of the volunteer twice, 30 seconds apart.

Pedalling faster, beating faster

We found that as pedalling rate increased, so did heart rate. This can be seen on the left-hand graph below by the line which goes up in diagonal from bottom left to top right. This suggests that faster pedalling did indeed require more energy, even though the power output remained constant.

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Our graph, on the left, comes to a similar conclusion as Formenti and his colleagues on the right. As pedalling rate goes up, so does work rate and energy expenditure. Where Formenti measured oxygen uptake, which requires unwieldy equipment unsuitable for our event, we used heart rate as an easily obtainable proxy measurement, and it agrees nicely with Formenti’s findings.

What does it mean, really?

The real world meaning here is that cycling along the road in lower gears than necessary with high pedalling rate uses more energy than cycling in slightly higher gears but pedalling at a slower rate.

So what’s the deal with Chris Froome?

Chris Froome, and other pro cyclists are not your average human beings from a physiological perspective, so it’s probably a bad idea for us to copy them! The science does show that pedalling quickly at sustained power outputs up to 400 watts, achievable mostly by elite athletes, is far less wasteful. This is because most of the energy gets transferred to the bike in this scenario.

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It was especially dynamic and rewarding to engage with a diverse mix of people and preach the gospel of physiology. I would like to thank all the visitors who staked their reputations by joining our experiment! I would also like to thank The Physiological Society for financial support and especially Anisha Tailor for all of her sage advice. A big thanks to Louis Passfield for his generous support and loan of equipment. Finally, I would especially like to thank all of my wonderful volunteer scientists without whom the whole event would surely have been a disaster Elizabeth Halton, Chris Fullerton, Ozama Ismail, Fulye Argunhan, Elena Wilde, Svetlana Mastitskaya, Xiao Xiao Han, and Nick Beazley-Long.

 

 

Horse or Human: who will win the race?

Place your bets now! Because tomorrow, on 11 June, the 36th annual Horse vs Man Marathon will take place in Llanwrtyd Wells, Wales, where humans will test their mettle against horses on 22 miles of mountainous terrain. Who will win this year?

On flat terrain, it would be a no-brainer: horses clearly have a significant advantage over humans. With their lean and muscular physique, thoroughbreds can reach speeds of up to 55 mph, while the world’s fastest human, Usain Bolt, lags behind with a top speed of only 27 mph. So how do horses reach such impressive speeds? We can find some clues by studying their anatomy and physiology.

The first proper studies began over 200 years ago, after the death of a particularly special racehorse, Eclipse, who was never beaten throughout his racing career from 1769 to 1770. His extraordinary success prompted the founding of the Royal Veterinary College in 1791 and ever since then, veterinary scientists have been making great strides in finding out what it is that allows horses to run so fast. It turns out that several factors play a role, including a big heart and the ability to increase heart rate to a remarkable degree:

 

Horses’ ability to increase the amount of blood pumped by the heart around the body to the muscles makes all the difference in a race, and that is helped by the spleen, which contains a store of oxygen-carrying red blood cells that are released into the bloodstream during exercise. They have other tricks up their sleeve too:  compared to humans, they have a far greater tolerance of increased body temperature and blood acidity, both of which go up fast during intense exercise.

We can find other clues to horses’ speed in their long and light-weight legs, which have very springy tendons that save energy needed to move quickly. So where does the muscular power come from?  The leg muscles aren’t in the lower legs as humans’ are, but tucked up close to the body, connected to the lower legs by very long tendons, which also generate  ‘springiness’. As with all four-legged animals, the muscles in the back, neck and abdomen also contribute to the ability to gallop. The quickest racehorses have lots of fast twitch fibres in these muscles, helping them to generate more energy for movement via both aerobic and anaerobic respiration.

Also unlike humans, the stride in galloping directly controls the timing of breathing: the huge weight of the hindgut acts like a piston on the lungs at the front, sucking in the maximum amount of air possible and then expelling it rapidly, as the torso moves with each step. This neat trick means that horses can move large volumes of air in and out of the lungs very quickly, helping to maintain their performance for longer.

And, of course, no racehorse is complete without its rider – who also plays a key role in the horse’s performance. Have you ever wondered why jockeys ride crouching over the horse, rather than sitting upright? Well, this is known as the ‘monkey crouch’ and was invented by Americans in the 1890s in order to improve horse speeds. This position separates the stride of the horse from the rider i.e. as the horse moves forward, the rider moves back, and vice versa. In this way, the rider takes up some of the effort required to move forward, enabling the horse to save some much needed energy for the race.

But what about humans? How can we possibly measure up to all this? By levelling the playing field, to something less level – which is exactly what the Horse vs Man Marathon has done, by holding the race on mountainous terrain. This gives humans a fighting chance – so while it’s true that horses have dominated the Marathon so far, there have been two occasions when a human has won the race. How come?  On rough hilly ground, the horses’ ability to reach and maintain their peak speed is severely reduced. Humans are much lighter, so the changes in direction needed on rough ground take less energy than for the much larger horses.

If we look at the cases where humans have won the race, one factor immediately jumps out, and that is: hot weather. It’s not immediately clear why that favours humans. Our ability to sweat, which cools us down in hot weather, is shared with horses. But, being smaller, we have relatively more skin to sweat from than do horses, and that may be a greater benefit than horses’ greater tolerance of high body temperature. And humans can take on extra fluid during the race, replacing that lost in sweat, without having to stop – something their equine competitors can’t do.

So, who will win tomorrow? The weather forecast predicts maximum temperatures of 19°C, so the human participants will have to draw on all of their abilities, to be in with a chance of winning.

Who will you place your bet on?