Fats are confusing. With so many different types it is very difficult to know which ones are good and which are harmful. Certain fats however, such as trans fats, have had bad press. But what is a trans fat? And what makes them so bad for us above other types of fats? In order to understand this, we need to have a basic understanding of the structure and function of fat.
What are fats made up of?
Fats are also known as lipids and are the most energy dense food substance available to us at 9kcal/gram (in comparison to carbohydrate and protein, both at 4kcal/gram). This holds true for all fats whether it is healthy olive oil or a lump of lard. All fats are made up of 3 elements; carbon, hydrogen and oxygen. Although they have the same elements, different fats vary in structure and therefore behave differently in our body.
Triglycerides make up approximately 90% of our dietary fat and the vast majority of fat in our body. When we have excess calories in our body, they are stored as triglyceride. They are made up of 3 fatty acids stuck onto a glycerol back-bone. Think of a letter E. The part of the triglyceride structure that needs our attention is the fatty acid. It is here where the battle of good vs bad fat begins.
With the knowledge that fatty acids (FAs) are made from carbon, hydrogen and oxygen lets look at the structure of each individual fatty acid in a little more detail.
Saturated fatty acids are packed full of hydrogen bonds with no double bonds, in other words have no more room left in the molecule. These fats are hard white and solid in their visible form e.g. the white coating found within meat. The physical properties of all fat is very dependent no their composition and temperature. The more hydrogen ions in the FA, the 'stiffer' therefore more solid the fat. in addition, the colder the saturated fat is, the more solid it becomes. Less visible saturated fats can be found in coconut oil, cheese and whole milk. These saturated fatty acids have been closely linked to heart disease, stroke and type 2 diabetes.
In contrast, unsaturated FAs do have double bonds in their structure. A mono-unsaturated fat has one double bond and poly-unsaturated fats have two or more. The double bond(s) create ‘space’ within the molecule with fewer hydrogen ions. This means that unsaturated fats are 'less stiff' a substance and typically liquid at room temperature. Examples include sunflower, safflower and olive oil. All the 'good for you' Mediterranean diet classics. Unsaturated fats have been shown to lower cholesterol and are 'heart healthy'. Omega 3 and 6 are also types of polyunsaturated fats.
Trans saturated fats
Tran fats are unsaturated fats that have been tampered with by a process called hydrogenation. This basically means blowing hydrogen ions through the fat to break the double bonds and pack out the FA molecule. Why would anyone want to do this I hear you ask? Hydrogenatingfat makes it more solid at room temperature and aids food preservation and storage. This is great for manufacturers who don't want their product to go bad and improve the shelf life of their products. It can also enhance the culinary property of the food.
An important distinction is between partial and fully hydrogenated fats. A partially hydrogenated fat, is what we refer to as trans fats. If the hydrogenation process continues then the FA becomes packed full or 'saturated' with hydrogen ions, and essentially becomes a saturated FA. Trans fats, like most saturated fats, raise blood cholesterol levels, particularly levels of ‘bad’ LDL cholesterol. Trans fats can also reduce the ‘good’ HDL cholesterol, as well as increase levels of another form of blood fat called triglycerides. All of these effects of trans fats can raise your risk of coronary heart disease (CHD). Gram for gram, trans fats appear to increase risk of CHD more than saturated fats, and so pose a greater risk for our health.
There has been speculation whether trans fats may also occur when ordinary vegetable oils are heated to fry foods at very high temperatures and this is one reason why takeaway foods can sometimes be high in trans fats. But the jury is still out on that one. Naturally occurring trans fats also do exist and are found in small amounts in dairy products, for example cheese and cream, and some meats.
All trans fats may be potentially unhealthy, no matter where they come from, but if they are present or consumed at low levels, they are unlikely to have a signicantly harmful effect.
Gram for gram, trans fats appear to increase risk of CHD more than saturated fats, and so pose a greater risk for our health.
Now you know what trans fats are all about, here are some simple steps you can take to reduce the amount of trans fats in your diet;
In summary, be aware of the daily requirements for all the different types of fat. NHS guidelines indicate that the average adult can eat up to 70g of fat a day, of which no more than 20g should be saturated and the rest (50g) unsaturated. Reducing your trans fat consumption to a minimum can only be good for your heart, weight and general health.
Look out for my blog on fish oils and cholesterol to explore the world of fat a bit further! Thanks for reading!
When I ask my patients what they know about omega, most will know that it has something to do with fish or cod liver oil. Some will tell me that regular fish oil supplementation lubricates our joints while others say it is good for our heart. But what actually is omega and what does it do for our health? Read on to find out.
What is Omega
The first home truth is that omega-3 is actually fat. A polyunsaturated fatty acid to be more precise (have a read of my blog on trans fats to brush up on what constitutes a fatty acid before continuing trans-fats-the-fat-of-the-matter.html). It is termed an ‘essential fatty acid’, which means that it must be ingested, as the body cannot produce it. There are different types of omega, with the most renowned being omega-3 and omega-6. The number refers to where the first double bond occurs in the FA chain. For example with omega-3, the first double bond occurs 3 carbons into the chain. The placment of the first double bond is important as it changes the chemical nature of the compound and how our bodies react to it.
Why do we need Omega
Most studies agree that we don’t consume enough omega-3 in our diets. Omega 3 is needed for the production of hormone like compounds, otherwise known as prostaglandins. Prostaglandins act as anti-inflammatory agents in our bodies with positive health benefits. This anti- inflammatory action is suggested to improve most conditions in the body where 'inflammation' is a problem including asthma, inflammatory joint disease, cardiovascular health, certain brain conditions such as Alzheimer's. But before you hail omega is a miracle drug, there is very little evidence from big studies suggesting that this is actually the case.
Can omega help my health and performance?
In short, yes. A lot of the beneficial properties with omega, particularly omega-3 are due to the anti-inflammatory affect of prostagladins. Lets have a look a few suggested key areas where omega can make a difference:
1. Exercise usually puts your body into a catabolic state, which means that muscles and tissues are being broken down with a degree of inflammation present. Anything that helps the body reduce that inflammation will ultimately help muscle soreness and aid recovery time. There is some suggestion that omega-3 aids protein synthesis which in turn helps muscle to build.
2. Animal studies have shown that a higher dietary omega-3/omega-6 fatty acids ratio is associated with beneficial effects on bone health. This ultimately helps in the prevention of bone stress reaction and fractures. A systematic review of omega-3 fatty acids and osteoporosis - NCBI
3. Symptoms for medical conditions such as exercise induced asthma may also be improved http://www.resmedjournal.com/article/S0954-6111(13)00139-X/abstract.
4. Another key area where omega can improve our performance is with nerve conduction and neuromuscular control. Fat surrounds the nerve axons in our body acting as an insulator. This insulation increases the rate of transmission of signals and improves its quality. For a performance point of view, this translates into improved control of muscular contraction, speed and reaction times.
Omega-3 and heart health
In contrast one area where omega-3 has a well proven positive benefit to our health is with heart disease. The UK Scientific Advisory Committee on Nutrition suggest a "large body of evidence" suggests that fish consumption, particularly oily fish, reduces the risk of cardiovascular disease. It does this by;
Different types of omega-3
Omega-3 comes in a variety of forms that we should be aware of;
Both EPA and DHA are longer chain fatty acids and are found in oils of cold water fish, such as herring mackeral sardines and shellfish. ALA are short chain forms of omega and are not utilised by the body as well.
Why are fish in particular packed out with omega-3 you may ask? And why cold water fish in particular? Remember, the more double bonds in the fatty acid, the more liquid the fat will be and therefore the less likely it is to freeze at colder temperatures. The cell membrane and other cellular structures in cold water fish therefore remain fluid in a very cold environment due to the number of double bonds.
Recommendations for omega
Omega-6 fats are found in vegetable oils such as rapeseed, corn, sunflower and some nuts. While most of us get sufficient omega-6 in our diet, mostly from cooking oil, we're advised to eat more omega-3 by eating at least two portions of fish a week, including one of oily fish. To help protect against heart disease everyone should try to eat 1 serving of high Omega 3 fish and 1 serving of white fish a week. Tinned fish is as good a source of omega 3 as fresh fish, tends to be cheaper, and is convenient as it can be easily stored. The British Heart Foundation endorses the Princes brand of tinned fish as it has a higher Omega 3 content.
Eat at least two portions of fish a week, including one of oily fish.
If you are vegan or vegetarian, there are other foods that contain omega-3 such as;
Is all omega good omega?
A word of warning, foods such as flax and chia seeds, nuts, avocado, olive oil contain ALA omega-3 chains rather than EPA and DHA. This is great but unfortunately the cardiovascular benefits of omega-3 discussed are more associated with the longer chain omega-3 FAs. In addition less than 1 percent of ALA is converted to EPA and DHA.
Don’t fear though, this is where fish oil supplementation are worth their weight in…well…omega. Cod liver oil supplementation is great source of omega-3 which in recent years may have lost flavour due to mercury poisoning scares. With omega-3 supplements, aim for 0.5 – 1.0g omega 3 daily (on the active ingredients will be listed as EPA and DHA).
In addition, excessive amounts of omega-6 polyunsaturated fatty acids and a very high omega-6/omega-3 ratio (as is found in today's Western diets where is can reach 20:1) promote the pathogenesis of many diseases, including cardiovascular disease, cancer, and inflammatory and autoimmune diseases. By increasing levels of omega-3 (lowering the omega-6/omega-3 ratio) exerts suppressive effects. To improve our ratios we need to increase our omega-3 consumption and reduce omega-6 as much as possible. This is difficult as we have already discussed omega-6 is very readily available, especially in cooking oil. We are aiming for a omega-6:omega-3 ratio of about 4:1 (The importance of the ratio of omega-6/omega-3 essential fatty acids.). But this is definitely something not to get obsessed about, just bear it in mind.
In conclusion, omega and omega-3 in particular has many potential benefits to help you with your performance and recovery. However, remember that there is still much more scientific evidence required to back this. One area where omega-3 does make a big difference is with cardiovascular health. It is definitely therefore worth making sure you have having the recommended weekly dose of omega-3 to ensure you reap all those benefits!
Have you ever felt fatigued, drained, convinced that your iron levels are low. Then been to the GP who checked your bloods… only for them to come back normal. No answers or solutions found… just ongoing tiredness.
The truth is there are many reasons why people may feel more tired than usual, and the first port of call should be a full check up by your GP. Although exercise is good for you in many ways, it can actually deplete your body’s iron and leave you feeling more tired than usual. The way that this occurs can be quite surprising.
Why we need iron
Most of people know that iron is involved in the formation of our red blood cells. Haemoglobin, an iron containing compound, is essential for transferring oxygen in your blood from the lungs to the tissues. In muscles, myoglobin functions as an oxygen storing unit, providing oxygen and energy to the working muscles. Myoglobin contains haeme and is responsible for the red colour of our muscle and iron rich red meats. In fact, across our whole body iron is an essential compound which allows every single one of our cells to access its stored energy (to create ATP via the electron transport system). Also, our iron levels play an important part in controlling our susceptibility to infection and immune function.
Where we store iron
In the western world, most people have approximately 4-5 grams of iron. Approximately 70% of this is found in Haemoglobin and used for our oxygen carrying capacity. About 25% is stored in a protein called ferritin that can be found in most cells but in abundance in our liver, spleen and bone marrow. Ferritin plays a significant role in the absorption, storage, and release of iron. As the storage form of iron, ferritin remains in the body tissues until it is needed to make more red blood cells. Doctors measure ferritin as an indicator of our body iron levels as we will discuss later.
Why we lose iron?
Although dietary iron is poorly absorbed, the body conserves its iron stores carefully, reabsorbing most of the iron released from the breakdown of red blood cells. As a result, the body normally loses only 1 to 2 mg of iron per day. This loss is restored by the iron absorbed in the from dietary sources. However, some people are at a higher risk of developing anaemia than others. For example, women with heavy menstrual losses and pregnant women. However, people who exercise are another high risk group that are often forgotten.
So why does iron loss occur in people who exercise?
Iron requirements and replacement
Athletes have dietary iron requirements that are 1.3 to 1.7 times higher for athletes than non-athletes. This is to make up for the extra losses described above, but also regular exercisers usually have more red blood cell (RBC) mass, meaning higher iron needs. As we exercise, our body is continuously regenerating and growing raising iron requirements.
To measure iron status, doctors often use reference values to determine whether ferritin levels are normal. A low ferritin level can be considered less than 15 ug/L. However due to the higher iron requirements for exercisers, this reference range can be misleading. People who exercise should have a lower threshold for the treatment of low ferritin levels or anaemia. For instance, some professional footballers are often treated for iron deficiency when ferritin levels dip below 50-70 ug/L, which would be considered normal to most doctors.
The best way to replace low iron levels is through diet, and I will discuss this in another blog. However, if you do a lot of exercise, it is always worth letting your doctor know how much before you have a blood test to investigate anaemia. After all, a long distance runner putting in 50 miles/week will have different iron requirements to the average patient.
I hope you now understand a little more about the iron in your blood. Look out for my next blog on the best way to replace iron by adapting your diet!
People who exercise may know what it feels like to ‘feel the burn’. And most runners will have experienced ‘a stitch’ whilst running. Usually poor old lactic acid gets the blame. I have even heard people blame lactic acid for their cramps.
But what is lactate and lactic acid and why does it why does it get such a hard time? This post aims to dispel some of the common myths regarding lactate. I make no apologies, it gets a bit geeky...
Myth 1. Lactate is acidic
Strictly speaking, an acid is a substance that is able to donate hydrogen ions (H+). Lactic acid is such a substance. When it donates a hydrogen ion the resultant product is referred to as the conjugate base of the acid and in this case is Lactate. The body does not store lactic acid but quickly breaks it down to lactate. Lactate itself is therefore not an acid!
Myth 2. Lactate is a waste product
Wrong. Lactate and lactic acid for some time have been considered a waste product resulting from a lack of available oxygen to the working muscles. Far from being a waste product, the formation of lactate allows the metabolism of carbohydrates to continue through glycolysis. The heart, brain and most slow twitch fibres are very good at clearing lactate from the blood and in some cases lactate may actually be the preferred source of fuel. The vast majority of lactate produced is reused and is not a waste product.
Myth 3. A Lactate build up causes our muscles to burn
Nope. The burn or ‘stitch’ you may feel is thought to be due to the acidity, or excess of H+ ions, of muscles during exercise. Lactate, as we now know is a conjugate base and therefore helps to mop up these excess hydrogen ions. Lactate actually prevents muscle acidosis by transporting H+ ions out of muscles.
Myth 4. Lactate hangs around the body for days and causes ongoing soreness.
During and after your workout, your muscles and heart can metabolise lactate for energy. Your liver clears lactate from the bloodstream by converting it into glucose. The liver can also convert lactate into amino acids, the building blocks of proteins. Some lactate is lost in your sweat as well. All of these processes contribute to the rapid clearance of lactate from your bloodstream after exercise. Nearly all of the lactate you produce during a workout is cleared within 30 to 60 minutes, even after very intense exercise. Performing an active cool-down after your workout will help clear lactate more quickly than simply resting.
Myth 5. Massage therapy can clear lactate
Lactate accumulation after vigorous anaerobic exercise is cleared rapidly and efficiently by the body. This occurs on the cellular level via metabolic pathways and not by soft tissue therapy. However, massage therapy may help the mechanical symptoms of delayed onset muscle soreness, or DOMS, which is muscle soreness that typically develops a day or two after exercise. DOMS results from microscopic damage to your muscles, usually from exercises that you are not accustomed to doing.
What is the lactate threshold?
Anaerobic power and capacity (creating energy without the use of oxygen) are essential elements in sports where brief and explosive movements are required. Take a 100 metre race. If you're running at full capacity your body will not be able to meet your energy demands through respiration and oxygen intake. Anaerobic pathways take over and lactate levels will eventually build in blood.
In contrast, if you pace yourself well throughout a marathon race, you may never need to rely on anaerobic power as your energy requirements may be met through breathing and aerobic glycolysis pathways. This is providing you do not cross your anaerobic threshold, the point at which body demands cannot be met by aerobic metabolism and anaerobic takes over. This threshold is also sometimes called lactate threshold as vigorous exercise beyond this will cause lactate blood levels to rise.
(NB. The above description is hugely simplified. In reality there is no real 'distinct threshold' as aerobic and anaerobic pathways are being utilised all the time, just in varying degrees, but you get the idea...)
The anaerobic or lactate threshold is often a marker of fitness and can be trained over a period of time. Primarily for three reasons;
1. Lactate utilisation increases
2. Lactate production declines and
3. Lactate clearance increases.
Lactate in sport
In elite athletes, lactate levels are tested throughout their year/season to determine their lactate threshold. This is done by a simple pin prick blood test after a predetermined vigorous exercise programme. This acts as a marker of their fitness levels. The longer it takes an athlete to reach their lactate threshold, the greater their aerobic capacity and cardiovascular reserve must be.
Knowing your lactate threshold can help you determine how hard to train or when to push yourself during a race
Why does any of this matter to me?
Amazingly, some heart rate wrist monitors can estimate your lactate threshold by using your heart rate responses to set running protocols, without a drop of blood in sight. For experienced runners, the threshold occurs at approximately 90% of their maximum heart rate and between 10k and half-marathon race pace. For average runners, the lactate threshold often occurs well below 90% of maximum heart rate.
Knowing your lactate threshold can help you determine how hard to train or when to push yourself during a race. If you know you are exceeding your lactate threshold 5km into a half-marathon race, then there is no way that pace will be sustainable. Whilst training however, you want to be pushing your lactate threshold on occasion to gain the maximum cardiovascular and health benefit!
By training smart you should see your lactate threshold rise over time. But more importantly, by having a basic understanding of the science behind how our bodies create energy, this gives us another tool to help us train better and maximise our results.
Ask yourself this question. If you had to choose between being thin without having to do any exercise, or doing lots of exercise but still have a high BMI, which would you choose? Silly question I know, undoubtedly most people will opt for the former. But after reading this blog see whether you have a different opinion.
We all know someone who seems to have no problems with their weight. No matter what they eat, or how little exercise they do, they are slim and in shape. You may even be this person. On the other hand, we may know people who seem on the larger side but are brilliant at a sport or fitter than you could ever hope to be. In fact, fitness and fatness aren’t as closely linked as we once thought. In addition, newer understanding about where we store fat may actually prove to be the most important factor.
People often change their lifestyle and exercise levels as a reactive measure. The classic example is putting weight on during the festive season, and then stepping up the exercise in the new year. However, science is increasingly telling us that there is actually very little correlation between our size and our overall health and fitness. Some studies suggest that the risk of cardiovascular disease is lower in individuals with a high BMI and good aerobic fitness, compared with individuals with normal BMI and poor fitness (1).
In addition to this, the way our body distributes fat can hold more significance in how damaging it is to our health. Fat that is more centrally placed (sometimes described as being apple shaped) is potentially much more harmful than more peripherally distributed fat. Central fat is often accompanied by fat around our organs (visceral fat) and within the abdominal cavity. You may have heard the term ‘fatty liver’ before. Ironically, it is possible to have large stores of visceral fat but low levels of fat below the skin (subcutaneous fat). This will give you the appearance of a TOFI, thin on the outside, fat on the inside.
Why does central obesity matter?
In medical terms, this type of obesity epidemic is called ‘central obesity’. There are very strong links with central obesity and developing the Metabolic Syndrome. The metabolic syndrome is a cluster of biochemical and physiological abnormalities that are associated with the development of cardiovascular disease, insulin resistance and type 2 diabetes. Not good news at all.
Are genetic factors important with central fat?
I often hear patients blame their genetics for being overweight, saying ‘big bones run in the family’. This may even affect their willingness to try and lose weight as they feel it is a battle they are destined to lose. When it comes to losing subcutaneous fat, for most people, there is no reason why it can't be lost. There are however associated genetic traits that make this more difficult e.g. a large appetite, variations in metabolism. But very rarely are genetics the primary cause of obesity (Prader-Willi syndrome is one example of a rare genetic condition that makes you put on weight). In many cases, obesity is more to do with environmental factors, such as poor eating habits learned during childhood.
On the other hand, when it comes to central obesity some studies suggest that genetics play a much bigger role and the majority of inter-subject variance in central abdominal fat in non-obese individuals is due to genetic factors (2). There may also be a variation across different ethnic backgrounds. People of a South Asian origin have a more centralised distribution of body fat without necessarily developing generalised obesity and show raised obesity-related risk at lower waist circumference levels (3).
How do we measure internal fat?
If you wish to spend your hard earned money measuring your internal fat a common technique used is bioelectrical impedance analysis (BIA) machine. You might find this machine at the gym or specialist sports clinics. This machine passes an electrical current through the body to calculate the percentage of body fat. Unfortunatley, there are lots of inaccuracies associated with this method. Dehydration, for example, affects BIA measurements as it causes an increase in the body's electrical resistance. Also, the jury is out on how accurately it can differentiate between internal and subcutaneous fat. New medical imaging techniques using MRI and CT are now allowing us to measure internal fat accurately. But these techniques are still mainly used for research purposes only.
Can we reduce central obesity and internal fat?
Yes, you guessed it. Diet and exercise come to the rescue once again. However, to target central and visceral fatty deposits, we need to be smart about how we exercise. Some studies suggest that light aerobic exercise is relatively ineffective at targeting central obesity. In contrast, anaerobic, or high intensity exercise depletes our muscle glycogen stores and requires the mobilisation of our fat stores from within the body. There is some evidence to also suggest that early morning exercise before eating carbohydrates help us to deplete our glycogen stores and burn that internal fat. Diet also plays an important part in reducing visceral fat. This includes avoiding refined sugar and carbohydrates and increasing our fibre content (fibre-facts-and-fibs.html).
TOFI vs. SUMO
Lets look at the life of a sumo wrestler. They are the experts in high intensity exercise, or interval training as they perform explosive bouts of movement followed by short periods of rest. If you were to look at a sumos’ body composition by putting them through a MRI scanner, amazingly they would demonstrate very little internal fat. They would also have an extremely good anaerobic capacity and very high fitness levels. All this despite the fact that some wrestlers can reach a BMI of 50+ and consume over 6000 calories a day. Sumos also have large amounts of muscle mass which helps increase their metabolism burning those stores of fat around their organs (gain-mass-to-lose-weight.html). In contrast, our skinny friend who does no exercise may display very poor fitness, low muscle mass, and high levels of central obesity, despite appearing thin and healthy on the outside.
What does this mean for me?
The message i'm trying to get across from this blog is not to judge fitness on appearance. And also not to be complacent and think that just because you might not be overweight you should neglect your fitness. Not many of us will ever get the opportunity to formally measure our central fat stores, just like we won’t get the chance to measure the state of our arteries (and if ever you do, it’s probably a bit too late!). However, by incorporating high intensity interval sessions like a sumo wrestler does, we can improve our anaerobic threshold and burn our internal fat stores, reducing the risk of developing type 2 diabetes and cardiovascular disease. A good way to start doing this is by mixing up your running! (smart-running-ways-to-train.html).
In summary, it is much better to treat our bodies with respect both on the inside and out, and not get obsessed with appearance and waistlines!
Physical inactivity is now recognized as one of the biggest health problems in the 21st century. It is up there with smoking and obesity. We all know it is better to take the stairs rather than the escalator, but how much does this actually help us lose weight?
Non-exercise activity thermogensis, or NEAT, is the energy we spend during the day essentially ‘figiditing’. These movements are not planned and spontaneous with no real purpose. Examples include tapping feet, leg shaking, standing and general pottering about. After all, the people who can’t sit still are generally the ones who are always thin!
But what if you are someone who goes to the gym 3-5 times a week. It shouldn’t matter if you sit down and are not as active for the rest of the day as you have already ‘burnt’ of your daily calories? Wrong. Amazingly, NEAT is the predominant component of energy expenditure and usually burns of more calories than are structure planned exercise. Even for those people who exercise regularly, they still burn more calories through all those unnecessary movements. Have a look at the calorie expenditure that is possible through NEAT.
NEAT is the predominant component of energy expenditure and usually burns of more calories than any structured planned exercise
So how do you increase your NEAT?
There are loads of ways to try and increase NEAT. Here are a few things you can try:
The table below highlightss how much NEAT can vary between different occupations. Now Imagine how much you can increase your calorie expenditure by making a few adaptations.
So remember, it is not enough to exercise and then sit around all day. Most of our calories are spent doing the smaller unplanned movements. It is the habits we form that will ultimately help us lose the most weight. Have a think about how you can put more NEAT into your day, good luck!
We’ve all woken up sore the day after a hard work-out or long run. I often hear my patients say they feel stiff in their muscles and tendons. The relationship between stiffness and tendons is actually a very intricate one, and the stiffness of our tendons can be a good predictor of our performance as well as our injury risk.
What does stiffness mean?
In the normal world, when most people say they are stiff, they are usually describing soreness or tightness. Some people may label their lack of flexibility as stiffness. But let us consider for a minute what stiffness means in the scientific world, as it is an engineering concept.
Stiffness is the mechanical property describing the relationship between the force applied to the tendon and the change in the length of the unit. In other words, how much a tendon will stretch with a certain force applied to it. If we think of a tendon as an elastic band, stiffness is the amount of stretch you will get by pulling it with a defined force. The more stiffer the tendon, the less it will stretch.
It can be summarised by the following equation:
Stiffness (N/m) = force/change in muscle-tendon complex (MTC) length
Why do we need stiff tendons?
Consider this scenario. You are a 100m sprinter. Would you want to have tendons that are stiff and transmit forces from your muscles quickly to create movement? Or more a ‘compliant’ tendon that is stretchy and uses up more time and energy. The former right? The truth is, stiffness is not a bad thing in some tendons. Those tendons that are shorter and are used for more explosive movements e.g. knee and ankle tendons, will benefit from being a bit stiffer in comparison to tendons which surround joints that benefit from larger ranges of motion e.g. the shoulder.
If stiffness is so good for me, why does my Achilles hurt?
Imagine you have been for a long run, much longer than what you are used to. It is likely the next day your knee or ankle tendons will feel stiff. In fact, this is exactly what is happening. The first stage of a tendon reaction is called the reactive phase. The tendon swells with water as a short term adaptation. This is the body’s way of trying to stiffen the tendon to reduce the stress it is being put through. If we were to continue running long distances without the appropriate training our tendon will then change in cellular structure and breakdown. By training properly and increasing your running volume and intensity gradually, your tendons will naturally adapt and stiffen accordingly. Remember, if you are suffering from any tendon pain, you need a full assessment by an appropriately qualified clinician.
How can I train tendon stiffness into my tendons?
Different types of training will influence the stiffness of tendons differently. Endurance training will generally increase the stiffness across some joints. This could be beneficial for movements such as running because of the more powerful recoil effect, which results in more economical movement. On the other hand flexibility and pylometric training such as stretching and jumping exercises have been shown to decrease tendon stiffness.
In reality, by combining resistance training and stretching exercises, tendon load and resistance can be increased to deal with the biomechanical demands of running, while muscle compliance can be improve our range of movement and strength. However, striking the right balance between tendon compliance and stiffness perhaps needs more consideration than we have previously given it.
Ok, so you love tennis. Or cricket. Baseball? If you play a sport that involves either throwing a ball or racquet, try this little experiment. Take your throwing arm or racquet arm and see how far you can reach behind your back (from below). Now try this with your other arm. Any difference?
If you are able to reach your non-throwing arm significantly further up your back than the other side, you may be suffering from glenohumeral internal rotation deficit (GIRD). GIRD is a condition that leads to the loss of internal rotation in shoulder joint (the movement that allows you to put your hand behind your back). Lets look at a little shoulder anatomy and biomechanics.
The shoulder joint is surrounded by a thin layer of tissue called capsule. The capsule is responsible for sealing the joint space, providing stability by limiting movements. It also helps with our joint position awareness and proprioception. When we put our shoulder through repetitive throwing motions over a long period of time, our capsule is distorted, leading to GIRD.
To understand why this happens better, lets look at what happens during a tennis serving motion.
Kinetic chain theory
The tennis serve is a kinetic chain which has five different phases:
1. Wind up (knee flexion, trunk rotation)
2. Early cocking
3. Late cocking
4. Acceleration phase (including long axis rotation)
5. Follow through
During phase 2 and 3 of the serve (as demonstrated by the red rectangle), our shoulder is in a position of maximal abduction and external rotation. It is this position that causes the front (anterior) portion of the capsule to stretch, whilst the back (posterior) becomes tighter. This posterior capsule tightness is what eventually restricts our movement.
Why does GIRD matter?
You may be thinking ok, so what if I can’t get my hand behind my back? If anything, you may have greater external rotation (movement in the opposite direction) with your throwing arm which makes you more flexible, right?
Unfortunately, that's not how it works. If you suffer from GIRD, you are at a higher risk of injuring your shoulder in the long run. If the limitation of internal rotation exceeds the gain you may get in external rotation, there is a decrease in your rotational arc. This leaves the shoulder is susceptible to injury. Some studies suggest you are 25% more likely to suffer from a tear to the cartilage in the shoulder, or a SLAP tear. Also, there is more chance of developing instability and impingement symptoms in the shoulder
The sleeper stretch
If you think you suffer from GIRD, don’t despair. First principles are always keep your shoulders, back and core muscles well balanced with conditioning and strength work. Avoid over loading one particular side of your body without working on the other side too. For example, when we throw, the muscles of our rotator cuff that help us internally rotate our shoulder become very strong, so be sure to work on the external rotatorstoo. They can easily be isolated using the cable machine in the gym. Also, working on technique to minimise injury is vital. By using the whole kinetic chain when throwing, we use the bigger muscles in our legs and torso to generate power rather than the shoulder.
There are basic stretches you can do to improve the loss of internal rotation. The first is to practice trying putting your hand behind your back and reaching as far up as you can. Try getting into the habit of doing this regularly, for example in the shower.
You are 25% more likely to suffer a cartilage tear in your shoulder if you suffer from GIRD
The sleeper stretch is a specific exercise that works on increasing the amount of internal rotation of the shoulder. Here is a brief description of how to do it (see diagram above).
Keep a measure of how your internal rotation movement improves by seeing how far you can get it up your back. Ideally, you want both sides to be the same.
I hope this blog has introduced the concept of GIRD to you. Remember, it is always important to accompany your chosen sport with strength and flexibility work. This will keep you playing injury free for longer!!
Vitamin D is causing quite a stir in the news. In the summer of 2016, Public Health England (PHE) recommended that to protect bone and muscle health, everyone needs vitamin D equivalent to an average daily intake of 10 micrograms. PHE also advised that in spring and summer, the majority of the population get enough vitamin D through sunlight on the skin and a healthy, balanced diet.
This advice is great, but the requirements for people who exercise regularly differ greatly from that of general population.
What is Vitamin D
Vitamins are organic compounds (meaning they contain carbon) and can be characterised into water soluble vs fat soluble. Fat soluble vitamins are stored and sequestered into fat stores, and therefore have a much longer bioavailability than water soluble vitamins. In contrast water soluble vitamins are excreted out in urine if consumed in too large a quantity and are used by the body fairly quickly. Vitamin D is a fat soluble vitamin.
Where does vitamin D come from?
Our bodies cannot produce vitamins except for one exception, vitamin D. The term vitamin D is, unfortunately, an imprecise term referring to one or more members of a group of steroid molecules. Vitamin D3, also known as cholecalciferol is generated in the skin of animals when light energy is absorbed by a precursor molecule 7-dehydrocholesterol. If someone has adequate exposure to sunlight, theorectically they do not require dietary supplementation.
How does my body synthesis Vitamin D?
Vitamin D, as either D3 or D2, does not have significant biological activity. Rather, it must be metabolised within the body to the hormonally-active form known as 1,25-dihydroxycholecalciferol by a 2 step process in the liver and then kidney.
Optimal Vitamin D levels can reduce the risk of debilitating stress responses in bone
What does vitamin D do in the body?
Vitamin D is well known as a hormone involved in mineral metabolism and bone growth. Its most dramatic effect is to facilitate intestinal absorption of calcium, although it also stimulates absorption of phosphate and magnesium ions. In the absence of vitamin D, dietary calcium is not absorbed at all efficiently. Vitamin D stimulates the expression of a number of proteins involved in transporting calcium from the lumen of the intestine, across the epithelial cells and into blood. Not only does vitamin D assist in growth and maintenance of the bone, but it also aids in regulation of electrolyte metabolism, protein synthesis, gene synthesis and immune function.
What happens if I exercise with low vitamin D levels?
Although there is not yet enough convincing evidence to support vitamin D as a direct performance enhancer, obtaining optimal Vitamin D levels can reduce the risk of debilitating stress responses in bone which may lead to stress fractures. In addition, because of its active role in muscle and protein synthesis, recovery and fatigue may also be improved, all impacting your performance. Newer studies are also suggesting that as immune function is boosted, active people are less likely to suffer from common colds (1).
What should I do to boost my vitamin D?
1. Sunlight exposure
During the summer months, training or playing sport outdoors can have a massive impact in boosting your vitamin D stores. This can be further enhanced by maximizing skin exposure to sunlight e.g. by wearing shorts and tee-shirts. Your body can't make vitamin D if you are sitting indoors by a sunny window because ultraviolet B (UVB) rays (the ones your body needs to make vitamin D) can't get through the glass. Sunscreen prevents sunburn by blocking UVB light. Theoretically, that means sunscreen use lowers vitamin D levels. But as a practical matter, very few people put on enough sunscreen to block all UVB light, plus the risks of unprotected sun exposure far outweighs any additional vitamin D you might receive!
Remember, the bioavailbility of your replenished vitamin D stores during the summer months will last for weeks to months and therefore stand you in good stead for the sun deprived winter.
2. Managing obesity
A recent study funded by the British Heart Foundation has shown that for every unit increase in BMI (1kg/m2) was associated with a 1.15% reduction in the level of vitamin D in the blood (2). As we now know, Vitamin D is a fat soluble vitamin. This means the more vitamin we have ‘locked away’ in our fat stores, the lower the level circulating in our blood will be. This means we cannot effectively use the vitamin D in our body, the more fatty tissue we have. However, it also means, that we need adequate amounts of fat in our diet to absorb the Vitamin D in the first place. This again highlights the importance of a balanced healthy diet.
For every unit increase in BMI, there is a 1.15% reduction in blood vitamin D levels
3. Dietary intake
During autumn and winter, PHE recommends that everyone will need to rely on dietary sources of vitamin D, as sunlight is not enough. Vitamin D3 is also found in a small number of foods. Good food sources are:
The plant form of vitamin D is called vitamin D2 or ergosterol. In the UK, cows' milk is generally not a good source of vitamin D because it isn't fortified, as it is in some other countries.
Another source of vitamin D is dietary supplements. Recent guidance from PHE has suggested that the Vitamin D recommendation from consuming foods naturally containing or fortified with vitamin D, people should consider taking a daily supplement containing 10 mcg (micrograms) of vitamin D in autumn and winter. Ethnic minority groups with dark skin, from African, Afro-Caribbean and South Asian backgrounds, may not get enough vitamin D from sunlight in the summer and therefore should consider taking a supplement all year round.
What does the mean for me?
There is currently no guidance for people who exercise regularly on vitamin D, but in my medical opinion, we should be counted as a high risk group. This means as well as taking the above measures including optimising sunlight exposure and diet, supplementation should be taken over the winter months. If you exercise and train all year round, you will be doing no harm by taking 10 mcg Vit D supplementation all year round. Bear in mind however that even this dose may not be enough for high level exercisers and it is always worth asking for your Vitamin D levels to be checked by your doctor.
If you exercise regularly, you will be doing no harm by taking 10 mcg of Vitamin D once a day all year round. However, in some cases this may still not be enough.
What are normal values of vitamin D?
So you go to your doctor and get your vitamin D level checked. He tells you it is normal. Great.
No, not great. It is always worth finding out the value of your Vitamin D level as what is considered ‘normal’ can vary greatly. There is consensus that levels below 25nmol/Lqualify as ‘deficient’, but beyond this there is currently no standard definition of ‘optimal’ Vitamin D levels. Some sources suggest that levels above 50nmol/L are ‘sufficient’, while 70–80nmol/L is ‘optimal (3). It is worth noting that normal ranges also differ depending on which laboratory you get your blood processed in. Most sporting bodies will advise their athletes keep their levels above 90-100 nmol/L .
In other words, don’t be afraid to challenge your doctor if you feel your vitamin D levels are not being taken seriously enough! Or if he tells you they are in the normal range but doesn't take into account the fact you run 5 times a week. Optimising your Vitamin D intake is any easy way to improve your health and performance.
1. Nutrients. 2013 Jun; 5(6): 1856–1868. 2013 May 28. doi: 10.3390/nu5061856. Vitamin D and the Athlete: Risks, Recommendations, and Benefits D, Ogan, K, Pritchett.
2. Vimaleswaran KS, Berry DJ, Lu C, et al. Causal Relationship between Obesity and Vitamin D Status: Bi-Directional Mendelian Randomization Analysis of Multiple Cohorts. PLoS One Medicine. Published online February 5 2013
3. NICE. Vitamin D position statement. 2010.
We all know that stretching is meant to be good for us. Whether we are trying to touch our toes or are attending our weekly yoga class. But what is the best way to stretch? And is there a way of making it more interesting? There are actually many different ways of stretching. And depending what your goals are, they can be used to optimise your exercise.
Stretching is great for you in many different ways. We all feel better after a good stretch first thing in the morning or after a hard days work. Stretching aids relaxation, helping the tension in our muscles to switch off, and in turn can lower stress levels. By increasing the range of motion of a joint and making the surrounding muscles more compliant, our risk of injury decreases. Muscle tightness can increase the chance of injury during exercise e.g.muscle tears and tendon problems. Stiffness and achy muscles after exercise can also be relieved by a good stretch and, over time, our joints become more supple. Our performance during sporting activity may be enhanced if we warm up and stretch beforehand, after all, the more flexible we are, the better our movement will be. This is particularly important in sports which are heavily reliant on dynamic movements. Stretching and cooling down after sport and exercise can also help your body recover; ready for the next session.
In other words, a good warm up and stretch before your next 5 a side football match will help you play better, recover better and reduce your risk of injury. Well worth it!
What are the different ways to stretch?
When most people imagine ‘doing their stretches’, static stretching what they are referring too. ‘Static’ essentially means holding a stretch without moving. Static stretching can be active or passive.
Active stretching does not use external forces to produce the stretch. The stretch comes from the opposing muscles holding the limb in position, stretching the target muscle. For example, standing on one leg and holding the opposite leg out directly in front of you is classed as a static active stretch. The quadriceps actively hold the stretched limb out while the hamstrings are the muscle groups being stretched.
Passive stretching occurs when an external force is exerted on the limb to move it into a stretched position. This external force can be provided by using your own hands, a partner, gravity or a mechanical device such as a band. Using the floor to stretch still counts as a passive stretch, as the floor is providing an external force (for example trying to do the splits on the floor).
This is another type of static stretch where during a passive static hold, you contract your muscles against the resistance (but without your limbs moving). An example of this is a doing calf stretch against a wall. By trying to ‘push the wall’ you create an isometric contraction which will enhance your stretch.
Proprioceptive neuromuscular facilitation (PNF) may sound scary but is actually very simple. It is basically a combination of passive and isometric stretching. Imagine lying on the floor with one leg on the ground and the other in the air supported by a partner. Your partner creates a passive hamstring stretch by pushing your leg up vertically. If you push back against them i.e. attempting to bring your leg back to the floor, you create a isometric stretch (provided your limb doesn't move). If you continue pushing down for 30 seconds then relax, your partner will find they are able to push the passive hamstring stretch a little further and get your leg up a little higher. There are different physiological reasons why PNF stretching is so effective but many athletes in the elite sport world take advantage of it to gain extra flexibility.
This involves using movement patterns to mimic the exercise or sport you are about to do e.g. performing the motion of a golf swing to warm up. After a few repetitions, you will be able to increase reach and speed of movement. Another example is repeatedly swinging your leg back and forth. The movement should be one continuous smooth motion with no ‘jerking’. Dynamic stretching improves dynamic flexibility and is a very good way to warm up before a work out as it mimics the action you are about to perform.
Ballistic stretching uses the momentum of your body to ‘force’ the tendon beyond its normal range of motion. This uses the bounce or ‘elastic property’ of tendons to not only stretch the muscle, but help gradually length the tendon. This movement triggers the stretch shorter cycle, which is when a stretch of a muscle is followed by an immediate contraction and shortening. Each time the tendon stretches in the cycle it can lengthen that little bit more. An example ballistic stretch is bent over toe touching with a bouncing movement. On each movement, the athlete attempts to touch the ground using the bounce of gravity and bodyweight to assist in the stretch.
Beware! Ballistic stretching is potentially harmful as the muscles and tendons are forcefully pushed into a stretch. Use this one with care!
Stretching top tips
With all this in mind, here are some tops tips to spice up your stretches.
Have a go at all the different techniques to keep your stretching interesting. Create a warm up or cool down that uses a variety of stretches and mix up your routines. This keeps the muscles "on their toes" so they never get used to one particular exercise pattern!
Good luck and stretch safe!