Post No.: 0732
Furrywisepuppy says:
Skeletal muscles are said to be made up of two kinds of muscle fibres – Type I or slow-twitch, which are good for endurance but lack power; and Type II or fast-twitch, which are good for power but lack endurance.
Type I fibres are oxidative, which means they rely on aerobic respiration to fuel their contractions. Type II fibres can be further broken down into two sub-types. Type IIa fibres are oxidative-glycolytic because they use oxygen and glucose for energy. Type IIb (or IIx) are glycolytic. Type IIa fibres are therefore essentially intermediary and are the most adaptable type.
Most people are born with roughly an equal amount of slow-twitch to fast-twitch fibres, but some will have more of one kind than the other, which will make them more suited to power sports than endurance sports, or vice-versa.
Irrespective of your personal ratio of muscle fibres – there’ll be a number of sports or physical activities that you can excel at, such as sprinting instead of cross country running. If you’re not built to be a power athlete like a shot-putter then you could be an endurance athlete like a triathlete. There are different race distances in swimming, cycling or running to suit everybody. There are many sports where a mix or balance of speed and endurance is beneficial. Size doesn’t matter too – if you’re large then you could do brilliantly at rugby, or if you’re small then you could do superbly at gymnastics. Outfield footballers come in a range of sizes at the elite level. So there’s always a physical activity that you could excel at (unless you’re in a coma or have something like locked-in syndrome I suppose). If you find that one sport isn’t for you then you could try another one. Woof!
The current thinking is that these muscle types can be technically altered via training i.e. it’s nature and nurture. Regardless, the real-world effect is that all muscles are adaptable to a useful extent. You can improve your speed and/or stamina regardless of what ratio of fibres you were born with. If you lift plenty of heavy weights then your muscles will grow larger, or if you run marathons frequently then you’ll develop a leaner look. Thus if you don’t wish to stick to what you may be best for (enjoyment isn’t just based on what you may be best at doing but factors like joining in with what your friends like to play) – your body can adapt over time to whatever exercise and training it is subjected to.
This means that two elite marathon runners with identical times can possess quite different muscle compositions. It however appears to be easiest to change or adapt between the two fast-twitch fibre types, and from being a speed athlete to an endurance athlete than vice-versa (because slow-twitch muscle fibres require oxygen and if pushed too hard, lactic acidosis can quickly arise and lead to muscle fatigue, hence they apparently cannot be trained to increase in much power, whereas fast-twitch fibres can be trained to increase their oxidative capacity). Top sprinters may therefore be born, as it were, but top marathon runners can be made. However, endurance is vital for many sports (and life itself is a marathon, not a sprint!)
Our mentality can adapt too. Roger Federer had to learn to control his temperament before he became world class. Andy Murray knew he had to work on his stamina before he could win a major. So sometimes it’s mental, sometimes it’s physical.
I might be someone who has a higher ratio of Type II to Type I fibres because I’m naturally zippy, yet I’ve managed to develop a decent walkies endurance too. One can maintain both a decent level of power and stamina; albeit one cannot be the best one can personally be at both simultaneously.
Anyhow, if you don’t have proportionally more fast-twitch fibres then you’ll have proportionally more slow-twitch fibres, or vice-versa. There’s far more to most sports than just an issue of power versus endurance but if you’re struggling to find a sport that you’re excelling at then it could be a case of trying something else that involves more bursts of speed, or is slower-paced but lasts.
The rest will depend on the opportunities one receives (e.g. the chances for a child to try different kinds of sports rather than just those decided by their PE teacher), one’s motivation to push oneself, and how one trains, eats and rests. And the younger you start (with age-appropriate activities), the more likely you’ll one day reach your full sporting potential.
There’s a high likelihood, based on the sheer number of people who’ve ever lived, that the world record holder for, say, the high jump, doesn’t possess the absolute best genetics ever for that event – but the person who has/did simply didn’t have the opportunity to explore high jumping as a career choice. Tibetans who live in high altitudes have genetic adaptations to cope excellently in low-oxygen climes, yet no Tibetan has been a Tour de France winner so far. Talents, like sporting or musical talents, aren’t as simple as looking at genetic inheritance – they’re a complex interplay of genetic and environmental factors. That’s why we cannot dismiss the impact of opportunity and support.
Genetics are nonetheless naturally an element for performance. A ‘gene for speed’ (ACTN3) is specifically expressed in fast-twitch muscle fibres, for instance. Environment is the other main element. Fatigue during exercise is down to many factors – including mental factors (the motivation and desire to push), physical fitness, training (not only its physical but also mental effects e.g. the experience of handling the pain at one’s limits) and one’s efficiency of exercise technique. Other temporary or environmental factors include the temperature (overheating), oxygen supply (which can relate to the altitude of one’s location), one’s blood glucose levels, fluids, electrolyte balance and other minerals (e.g. calcium and iron), stimulants and supplements, present injuries or soreness due to an insufficient recovery from previous sessions, and one’s current mood.
We can somewhat acclimatise to temperature and oxygen conditions, and that’s what athletes try to do before they enter a competition in a different part of the world. (Most heatstroke problems actually occur early in the summer when people haven’t yet acclimatised to the relatively higher temperatures, rather than later when people have. And then once you get used to 30°C, suddenly going down to 22°C can feel cold, when 22°C feels warm in winter!)
Nurture can also affect the expression of genes without altering their nucleotide sequences (epigenetics). It’s perhaps possible that exposure to exercise and various environmental stimuli can modify the expression of the gene that controls the GLUT4 glucose transporter, for instance. Some gene expression modifications will be transient, while some can be maintained for quite some time (even passing on for a couple of generations in some cases).
Genes arguably don’t code for behaviour directly – they code for function. And the disease phenylketonuria (PKU) shows us that even if something is definitely genetic, it often requires an obligate environment for the disease to express; and if the environment isn’t obliging for the disease then one will live as healthily as someone without the same genetic risk.
So regarding something like obesity – a healthful diet can enable a person to live a high quality of life regardless of their genetic propensity for obesity. An individual’s genetics may have some influence on how their body reacts to an intake of glucose. But it might also be because they earned a more diverse gut microbiome via their diet, or they exercise regularly thus have a better insulin sensitivity.
Then again, one’s environment influences one’s diet. Someone could have genes that make them crave more calorie-dense foods or want to eat more, and they would’ve been fine if only they weren’t exposed to calorie-dense ultra-processed foods and drinks – like in many of our modern environments.
We could also point out that one’s courage to try new things, self-discipline to train, tenacity and personality are determined by the combination of one’s genes and upbringing too.
But let’s not focus on what we cannot or couldn’t control, especially when – from our lived experiences at least – there’s so much that can be done that’s within our own furry control at present.
Unless they lead to congenital diseases, there are few, if any, ‘objectively good’ or ‘objectively bad’ genes – just different ones that are good or bad depending on the situation or environment. For example, there are advantages and disadvantages for having dark or light skin, for being tall or short, for constantly craving calories or being more easily satisfied, for being curious or cautious, for being a genius or not (e.g. has the invention of nuclear weapons unequivocally been a welcome thing?), or indeed for having fast-twitch or slow-twitch muscle fibres.
Both nature and nurture overall play a role in equal ways. But all experts agree that training offers the greatest performance gains, thus a highly-trained athlete will always beat someone who is untrained, no matter what each of their natural genetic starting points were (e.g. between an untrained person who’s naturally very large and a trained weightlifter who’s smaller, the trained person will win at weightlifting; or between a naturally lithe person and a trained climber who’s much heavier, the trained person will win at climbing). So a trained body is stronger than any natural build without as much training or current conditioning. Trained women under 48kg can lift >115kg over their heads – most men who are much more massive cannot lift anywhere near that! Post No.: 0675 taught us that we cannot reliably judge strength with our eyes. A predisposition isn’t a guarantee because there are many other factors that lead to success or failure.
Of course, if both nature and nurture optimally align then one can potentially become one of the very best in one’s sport. So if one wants to be a professional athlete then one should ideally choose a sport that suits one’s genetic potential. And there’s a sport(s) for everyone because of the wide range of power to endurance events, and everything inbetween. This will usually be a sport you enjoy because you’re good at it, but not always.
Irregardless of the technical points – which may refine over time with more scientific research – the main thing to take away from this is that there is at least one sport or physical activity for every child! It may then boil down to being aware of that sport and having the opportunity to try it and receive decent coaching for it (e.g. young kids depend on adults to buy them equipment or take them to parks or pools, and local authorities and businesses need to provide those amenities – opportunities can make or break a budding career).
Physical activity is important for everybody, not just to keep fit and able whatever bodily abilities one may possess – but physical fitness affects our mental health and self-confidence too.
We all need to regularly exercise and/or move by doing enough NEAT (non-exercise activity thermogenesis) activities to keep healthy. Genetics do matter but they’re only one part of the picture. If you don’t already regularly exercise then recognise that if para-athletes can keep fit and push themselves to explore what their bodies can do then so can most other people too. Despite their difficulties, many fit ‘disabled’ people are therefore more physically able than unfit ‘able’ people! They give their all and don’t give up easily. They’re more independent and live with greater self-esteem than those who resign to their disabilities. So apart from those with extremely debilitating conditions – don’t use your biology as an excuse for not giving physical exercise another chance if you’ve not done it for a while. Give something a go. Even if you fail, you can try again or try another activity because there are hundreds of sports to try…
Woof!
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