Is sport good for us?

“Is sport good for us” was the question posed to me for my first blog article for Engineering Sport. Not exactly an ‘easy ice breaker’, but I thought I’d have a good go at it. So, where to start? First, I think it’d be a good idea to differentiate (at least a little) between sport and exercise. My colleague Dr Simon Choppin recently blogged on ‘what is sport’. He concluded that sport could be defined as an activity that has elements of both competition and physical, human movement. For example, although highly competitive, chess wasn’t classed as a sport (in the article) because a computer or robot could be programmed to move the chess pieces (removing the need for physical activity). Clearly, competition in isolation isn’t always good for us. What I think I’m dealing with here (especially when we think about our own bodies) is:

Is exercise good for your body?

To answer this, first we need a concept of what exercise actually is. A quick Google search will reveal a variety of potential answers with phrases like ‘physical activity’, ‘effort’, ‘health’, ‘fitness’ and ‘conditioning parts of the body’ being frequently mentioned. All of these phrases conjure mental images of people running, jumping, straining muscles and generally expending huge amounts of energy. This highlights a key theme of exercise: the production of force.

Force is produced by our muscles and is necessary to create movement, a defining feature of exercise. These movements could be anything from opening a door to lifting dumbbells but, at the simplest level, all movements boil down to force produced by muscles in conjunction with some external force (that is a force outside of our body, like the weight of a dumbbell for example). To create force, a muscle changes length. This is an important concept and, as I have the opportunity, I should briefly explain it. A muscle changes length, it does not ‘contract’ or even ‘expand’; this misleading terminology dates back to Galen (A.D. 129-216) an ancient Greek physician. In 1663, Jan Swammerdam placed a muscle (the thigh of a frog!) inside a sealed tube and activated it using a nerve. He was the first to note that muscle volume does not change when a muscle exerts a force, i.e. the muscle did not get smaller (contract) or get bigger (expand), it changed length. The mechanisms of how a muscle changes length will be broached in a subsequent blog article, discussing why we get hot when we exercise.

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Jan Swammerdam (left) and a sketch (right) of his muscle experiment in 1663.

To create movement, skeletal muscles are arranged in pairs to pull against each other to produce a turning force about a joint, i.e. a pivot involving two or more bones. As a quick, practical example, keep your upper-leg still and move your lower-leg upwards; the movement is a result of your quadriceps and hamstrings muscles working together – one muscle shortens (known as concentric) and the other lengthens (known as eccentric). What happens to the lengths of these muscles when you move your lower-leg downwards?

Anyway, so far I’ve only addressed muscle activity when a muscle changes length; I’ve yet to address muscle activity when a muscle does not change length. Winter and Fowler (2009) highlight that muscles also produce force during ‘isometric’ (zero movement) conditions: the picture below of a gymnast illustrates how skeletal muscle can produce huge quantities of force, but without causing movement, i.e. the gymnast’s muscles do not change length nor does the gymnasts position.

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Running requires muscles to produce force whilst changing (dynamic) length whereas the gymnastics rings exercise requires muscles to produce force and not change (static) length.

Taking both static and dynamic elements of muscular activity into account, Winter and Fowler (2009) provide this definition for exercise (homeostasis refers to the stable physical state of the body):

a potential disruption to homeostasis by muscle activity that is either exclusively, or in combination, concentric, eccentric or isometric.

So, exercise can be any muscular activity, regardless of how big or small, that alters your body’s current, stable state. Is exercise good for your body? In short, yes. Unfortunately the scope of this blog is far shorter than the mountain of scientific evidence that supports this; however Warburton et al. (2006) highlight some important points that should help illustrate this:

…there is irrefutable evidence of the effectiveness of regular physical activity in the primary and secondary prevention of several chronic diseases (e.g., cardiovascular disease, diabetes, cancer, hypertension, obesity, depression and osteoporosis) and premature death.

Warburton et al. (2006) go on to highlight that your health such increase in line with the amount of physical activity. However, The volume part of exercise, i.e. how often, how long and how hard, is difficult to identify. Different researchers have revealed different exercise doses, however the NHS is a good starting point and has exercise guidelines for children, young people, adults and older adults. Of course, there are also many social benefits to be found through participating in exercise and sport. These are often overlooked but Bloom et al. (2005) remind us of just how sport and exercise can improve social networks as well as an individual’s sense of belonging in a community. So, is exercise good for the body? For me, it’s a resounding yes.

References

Bloom, M., Grant, M. and Watt, D. (2005). Strengthening Canada: The Socio-economic Benefits of Sport Participation in Canada. The Conference Board of Canada. Ottowa, Canada.

Warburton, D.E.R., Nicol, C.W. & Bredin, S.S.D. (2006). Health benefits of physical activity: the evidence. Canadian Medical Association Journal, 174(6), 801-809.

Winter, E.M. & Fowler, N. (2009). Exercise defined and quantified according to the Système International d’Unités. Journal of Sports Sciences, 27(5), 447-460.

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About tennisgait

Dr Marcus Dunn is a researcher in the Centre for Sports Engineering Research (CSER), specialising in video-based performance analysis systems, camera calibration and sports biomechanics. Prior to joining CSER, Marcus graduated from the University of Portsmouth with a first-class, BSc (hons) degree in Sport Science and was awarded the John Wiley and Sons Ltd. prize for 'Best Final Year Project'. He went on to complete an MSc in Sport and Exercise Science at Sheffield Hallam University, specialising in sports biomechanics. Marcus has a keen interest in the biomechanics of running as well as field-based measurement systems. Marcus completed his PhD at Sheffield Hallam University in 2014 which was was sponsored by the International Tennis Federation. Marcus also develops performance analysis systems for the Sheffield Hallam University City Athletics Stadium (SHUCAS) project. Recently, Marcus has worked with FIFA (via Labosport UK) to assess Goal-Line Technology systems using high-speed photogrammetry.

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