The truth about sports, nutrition and pain!

¨Hitting the wall¨

You probably have heard of this expression before if you are a runner and may have even experienced it yourself. ¨Hitting the wall¨ usually happens around the 29th to 35th kilometer. The runner´s pace slows down considerably, the legs become very heavy and thinking often becomes hard and confused (now that I think about it, this last thing happens to me quite often). This happens because we basically run out of available energy.

The runner´s primary sources of energy during prolonged exercise are carbohydrates and fats. We have lots of stores of fat, around 70.000 to 75.000 kcla, even in a lean adult, but the fat metabolism requires a constant supply of oxygen, and delivery of energy is slower than that provided by the carbohydrate metabolism. The carbs reserves (glycogen), on the other hand, are quite limited and have only around 2.000 to 2.400 kcla, which happens to be enough energy to get us to kilometer 29-30. Since the body is much less efficient at converting fat to energy, running pace slows and the runner suffers from fatigue.To make things even worse the brain, which  only accounts for 2% of your weight and consumes 20% of your energy, gets its fuel source only from carbohydrates!!  So now next you ¨hit the wall¨you will know why that is. Hope you liked it. Till next time


Kenney L, Wilmore J, Costill D. Physiology of Sport and Exercise sixth edition, Human Kinetics,2015.

As I mentioned in my last post, scientist still don’t know why we get muscle cramps while exercising. The old theory was the electrolyte depletion and the new one is the muscle fatigue. I gave some flaws of the electrolyte theory, but this does not mean that I totally disregard that theory. As there are some people who actually lose salt at a rate five times faster than normal. Salts are essential to hydration despite of that mineral’s reputation for drying you out.  A body short of salts won’t deliver the water efficiently to the muscles. So even if you are drinking bottles and bottles of water, nothing will happen. The thing is that most people don’t lose salt so fast so, in my opinion, most of the exercise muscle cramps come from fatigue. There is also a difference between electrolyte depletion cramps and fatigue cramps. Electrolyte depletion cramps are much more serious, they affect more than one muscle and stretching won’t alleviate the cramp. Fatigue related cramps aren’t that serious, and usually by stopping the activity and stretching the cramp will go away.

So what can we do to try to avoid the muscle fatigue cramps? Go slower, decrease the intensity or train better, let me explain. We often get these cramps in competition and not while training. This is usually because, when we are competing, we are going faster or more intense than during practice due to the adrenaline or to due the mere fact that we are competing to get the best results. If the body is not trained to go at that intensity it will get tired faster, meaning a higher chance of getting a cramp.  And that is what the studies have shown, namely that the increased running speed is what predicts who will get the exercise associated muscle cramps. (1-5)

Hope you liked it.

  1. Schwellnus MP, Drew N, Collins M: Increased running speed and previous cramps rather than dehydration or serum sodium changes predict exercise-associated muscle cramping: a prospective cohort study in 210 Ironman triathletes. Br J Sports Med, 1-7, Dec. 9, 2010
  2. Schwellnus MP, Derman EW, Noakes TD. Aetiology of skeletal muscle cramps during exercise: A novel hypothesis. Journal of Sports Sciences, vol.15, pp 277-85. 1997
  3. Schwellnus MP. Muscle cramping in the marathon:aetiology and risk factors. Sports medicine. Auckland, NZ 2007.
  4. Schwellnus MP. Cause of exercise associated muscle cramps ( EAMC)–altered neuromuscular control, dehydration or electrolte depletion?
  5. Braulick KW, Miller KC, Albrecht JM, Tucker JM, Deal JE. Significan and serious dehydration does not affect skeletal muscle cramp threshold frequency. Br J Sports Med, 1009 Jun:43(6):401-8

The answer to this question is quite simply…… we still don’t know. Most people, even trainers, think that it is due to the loss of salts or electrolytes but in the past few years the scientific evidence out there clearly does not support this hypothesis. But most people still believe this thanks, in part, to the help of sports drinks.

This myth started almost 100 years ago in shipyards and mines, where workers were cramping up.  They did an analysis of their sweat which showed that it contained high levels of chloride (an electrolyte). So, they came to the conclusion that loss of electrolytes was the reason for the workers’ muscle cramping, along with dehydration. The problem with this is that they never checked the sweat of the people that were not cramping up. So, it sounded logical but this hypothesis had a couple of weak links.

  1. The first one being: When we sweat, we tend to sweat all over our body, meaning we are losing electrolytes equally in all  parts of our body. But somewhat surprisingly, exercise-associated muscle cramps only happen in the muscles that have been used extensively for the exercise. Kind of weird, right?
  2. When we sweat we lose much more water than electrolytes. In fact the loss of electrolytes is very low. Meaning that the concentration of electrolytes in our body is actually going to be higher than before doing the sport or activity. Also, two studies done on  ultramarathoners , showed that the runners who cramped up had a significantly lower sodium concentration (this means these runners were over-hydrated ), and lost less weight, and the more direct measures of the fluid in their blood showed they were better hydrated (1-4).  Amazing, isn’t it?
  3. Whenever we cramp up, we stretch and that usually makes the cramp go away for a while. So, if cramping is caused by loss of electrolytes or dehydration, how can simply stretching the muscle help us getting rid of our cramp?

Then why do we cramp up while exercising? Well, there is a new theory out there that basically says we cramp up because of fatigue. Let me explain: Muscle contraction is stimulated by a nerve, called the alpha motor neuron. One of the places this neuron gets its information from is muscle spindles and the golgi tendon organ.

1) Muscle spindles- We have probably all experienced the classic reflex, where a doctor or friend taps on the knee with a small hammer and you extend the leg. So, whenever your muscle is stretched too much, the muscle spindles activate and produce a muscle contraction (5).

2) Golgi tendon organ- Does the opposite, when it feels that a muscle is contracting too much, it will send a signal telling the muscle to relax (5).

Fatigue has been shown to increase the rate of muscle spindle and decrease the rate golgi tendon organ (5). Most muscle exercise cramps happen at the end of a race.

I will leave it at here for today. In my next blog I will talk about what we can do to try to prevent muscle cramps.




  1.  Schwellnus, M.P, Nicol R, Laubscher R, Noakes T.D Serum electrolyte concentrations and hydration status are not associated with exercise associate muscle crampint (EAMC) in distance runners. Brit J Sports Med 38(4): 488-92.
  2. Miller K, Knight K, Mack G, et al. Three percent hypohydration does not affect the threshold frequency of electrically-induced muscle cramps. Med Sci Sports Exerc. 2010;42:2056-2063.
  3. . Braulick K, Miller K, Albrecht J, Tucker J, Deal J. Significant and serious dehydration does not affect skeletal muscle cramp threshold frequency. Br J Sports Med. 2012;47:710-714.
  4. Sulzer N.U, Schwellnus M.P, Noakes T.D. Serum electrolytes in Itronman triathletes with exercise-associated muscle cramping. Med Sci Sports Exerc 3(7): 1081-85.
  5. Schwellnus M.P, Derman E. W, Noakes T.D. Aetiology of skeletal muscle cramps during exercise: A novel hypothesis. Journal of Sports Sciences, vol 15, pp 277-85, 1997.

The Fear of Back pain !!

I have already done quite a few blogs on back pain (Part 1, 2 , 3) but the myths surrounding it still continue, so I decided to do one more.

80% of us will probably experience an episode of back pain at one point or another in our life (some studies say that it is even more) (1-3). So, if you think about it, back pain is very common. In fact, to not experience back pain at some point in our life would be quite abnormal. And it doesn´t matter if you have strong or weak abdominals, or if you have too much flexibility or too little, or if one leg is larger than the other, or if you walk in a funny way, none of these factors will influence you experiencing an episode of back pain (4-8). To tell you the truth, the biggest factor for developing back pain is a history of back pain!!! (9). Sounds crazy but it is true.

So, instead of focusing on prevention of back pain (which we have already done for the last 20 years and nothing has changed), maybe we should focus on ¨how do I prevent my back pain from lasting so long¨. You see, when they experience back pain people get really scared, and get fearful of movement, which are two things that can actually make the back pain worse (10-11). Remember, we know the body needs movement to heal. Disk and cartilage etc. need movement to get their blood supply. So in most cases we should try and keep movement. Only when the pain is really bad should we rest but that rest should never be longer than 2 days (12). Pain does not equal tissue damage and it can be influenced by stress, beliefs, fears, anxiety and a thousand other things (as I have stated in previous blogs click here). Our body, including our back, is a wonderful strong machine. We have to start changing our beliefs around the idea that our back can get damaged easily or that our back is vulnerable.

In conclusion, we will all probably experience an episode of back pain in the coming weeks, months, years or whenever, just like we will probably experience a headache or a stomach pain. It is part of life and we shouldn´t get too worried. Studies say that 85-90% percent of the time we have back pain it is due to ¨non specific mechanical factors¨. This basically means we have no IDEA why your back hurts but it does. Only 2% of the time the pain is caused by a tumor, infection or a fracture and 8% due to a nerve compression (13-15). So next time your back hurts don´t be so afraid and keep moving. 😉


  1. Biering-Soeren2012 Feb 4;379(9814):482-91. doi: 10.1016/S0140-6736(11)60610-7. Epub 2011 Oct F. A prospective study of low back pain in a general population. Occurence, recurrence, and etiology. Scand S Rehabilitation Med 1983;19:71.
  2.  Balague F, Mannion AF, Pellise F, Cedraschi. Non-specific low back pain2012 Feb 4;379(9814):482-91. doi: 10.1016/S0140-67
  3. Hashemi L, Webster BS, Clancy EA, Volinn E. Length of disability and cost of workers compensation on low back pain claims. J Occup Environ Med 1998:40:261-66.
  4. Biering-Sorense F. Physical measurements as risk indicators for low-back trouble over a one-year period. Spine, 1984: 9:106-19.
  5. Battie MC, Bigos SJ, Fisher LD, Spengler DM, Hansson TH, Nachemson AL, Wortley MD. The role of spinal flexibility in back pain complaints within industry: A prospective study. Spine 1.
  6. Axler CT, Mcgill SM. Choosing the best abdominal exercises based on knowledge of tissue loads. Medicine and Science in Sports and Exercise. 1997: 29:804-11.
  7. Hellsing AL. Tightness of hamstring and psoas major muscles. Upsala Journal of Medical Science 1988. 93:267-76.
  8. Sandler R, Xuemei Su, TImothy C, Fritz S, Beattie P, Blari S. Are flexibility and muscle-strengthening activities associated with a higher risk of developing low back pain. Journal of Sciend and Medicine in Sporte. 2013.
  9. Taylor JB, Goode AP, George SZ, & Cook CE. Incidence and risk factores for first-time incident low back pain: a systematic review and meta-analysis. Spine Journal 2014
  10. Gheldof EL, Crombez G, Van den Brussche E, et al. Pain related fear predicts disability, but not pain severity: a pathway analytic approach of the fear avoidance model. Eur J Pain.2010;14:870
  11. Awinkkels-Meewisse IE, Roelofs J, Schouten EG, Verbeek AL, Oostendorp RQ, Vlaeyen JW. Fear of movemen/ re injury predicting chronic disabling low back pain: a prospective inception cohort study. Spine( Phila Pa 1976) 2006;31:658-664.
  12. Deyo RA, Diehl Ak, Rosenthal M. How many days of bed rest for acute low back pain? New England Journal of Medicine 1986;315:1064.
  13. Agency for HEalth Care Policy and Research (AHCPR). Acute low back problems in adults. Clinical Practice Guideline Number 19. Washington DC, US. Government Printing. 1994.
  14. Danish Health Technology Assessment (DIMTA). Manniche C, et al. Low back pain. Frequency Managemente and Prevention from an HAD. Perspective. 1991.
  15. Royal College of General Practioners (ACGP). Clinical Guideline for the management of Acute Low Back Pain. London Royal College of General Practicioner.1999

I want to try to make this blog as simple as possible so that most people can understand these ¨myths¨ once and for all. Let us start by giving some definitions to these words.

Toxin-  It sounds quite scientific but nobody really knows what the hell it is. All these miracle diets will tell you that they will get rid of those nasty ¨toxins¨ but won´t give you an explanation of what they are or how they will get rid of them. If they had a name, the experts could measure these toxins to see if the miracle diets or the ¨detox diets¨ really work. In fact, in 2009 a network of scientist assembled by the UK charity SENSE about SCIENCE contacted the manufacturers of 15 products sold in pharmacies and supermarkets that claimed to ¨detoxify¨. When the scientists asked for evidence behind the claims, not one of the manufactures could define what they meant by detoxification, or toxins (1)!!

Detox- Also sounds really fancy and scientific but if we just made clear that we can´t measure these toxins or that they even exist, then how is a detox diet going to work? I mean what are they detoxifying??? In medical terminology, real detoxification refers to treatment for dangerous levels of drugs, alcohol, or poisons (to name a few examples) and the treatment usually occurs in the hospital. And guess what…. doctors can measure all these things.

But the best thing of all, and something that I have been stating all through my blogs, is that our body is the best machine we have and it is ready in case we have to ¨detoxify¨ ourselves, and for this it counts on lots of helpers like:

  • LIVER-  It is incredibly efficient at getting rid of noxious substances. It contains enzymes which convert toxic substances into less harmful ones. These are then dissolved in water and removed in the urine.
  • KIDNEYS- Are fundamental in removing acids and regulating the body pH.
  • COLON- Responsible for removing unwanted solid matter from the body.
  • LUNGS-  The respiratory system is also involved in controlling blood pH. We breathe out all that carbon dioxide we produce.

So in other words, the body is perfectly capable of ¨detoxifying¨ itself and getting rid of all those nasty ¨toxins¨ (whatever those may be). And if it wasn´t capable of doing that you would be in lots of trouble and probably needed to go to the hospital.

But anyway, some people won´t believe this and will try different diets or different methods (colonic irragation to name one) to try to get rid of those ¨toxins¨. To those people I want to say that, before going out and wasting (I´m sorry, I wanted to say spending) your money on those treatments: try this new method, it involves exercising, eating properly and sleeping well 😉



The importance of resting.

Most people are quite competitive with themselves and always want to get better at what they do. If it is running, they want to get faster, if it is resistance training, they want to get bigger and stronger Whatever sport it is we usually want to get better. And what do we do to get better? We train, we train harder, we train faster, we train over and over again until we achieve our goal. And that is for the most part correct, We have to train to improve, but it is not the whole equation, an important part and one that people take for granted is REST.

Let us take running for example. Whenever we run high forces are applied that cause damage to our body. If we rest and recover, our bodies heal and adapt, making us stronger in the process. This is known as supercompensation and it can be applied to most sports. Injuries occur when these forces caused by the sports we practice exceed the body´s ability to handle it, either, because the body is too weak or the forces are too great. And most of the time this is due to 2 factors. We train too much and we don´t rest enough.

If you think about it we shouldn´t really be getting injured nowadays when running, I mean, with all the high-tech shoes out there, how is it possible? But the truth of the matter is that we still get hurt on a frustratingly regular basis, just like 30 years ago. Why you ask? Well in my opinion is not the shoes (1-2). The shoes aren´t even that important ( did a blog on it). The two main factors that predict if you are going to get injured are weight and volume. Meaning, the more you weight the more likely you will get injured, and the more you run the higher your chances of getting injured. And volume and rest are connected, as the more you run the less you rest. Rest includes sleeping properly and this is what a lot of people don´take seriously. Just this year a study came out that said ¨ adolescent athletes who slept eight or more hours each night were 68 percent less likely to be injured than athletes who regularly slept less¨(3). Did you guys see that? It said 68% percent less likely, that is a lot, and something we should take into account. So training is important but resting could be even more important as it could prevent a lot of injuries. And remember if you are injured you cannot train, meaning you won´t get better. So in conclusion REST!!!!!

  1. Theisen D, Malisous L, Genin J, Delattre N. Influence of midsole hardness of standard cushioned shoes on running-related injury risk. Br J Sports Med.2013
  2. Richards CE, Margin PJ, Callister R. Is your prescription of distance running shoes evidence-based. Br J Sports Med.2009 Mar;43(3):159-62.
  3. Mileski MD, Skaggs DL, Bishop GA, Pace JL, Ibrahim DA, Wren TA, Barzdukas A. Chronic lack of sleep is associated with increased sports injuries in adolescent athletes. J Pediatr Orthop 2014 MAr,34(2)129-33.

The myth of Lactic Acid!

I think we have all heard that muscle soreness is produced by lactic acid. That somehow, when you train your body, it produces lactic acid and that is what causes the pain after an intense workout. But the truth of the matter is that this is not true. Scientists have proven that years ago but the myth still persist, even within the sports community. The myth started back in the 1920´s when researchers showed that the exposure of frog legs to high levels of lactic acid interfered with the ability of the muscles to contract in response to electrical stimulation. Later research determined that lactate was produced through the breakdown of glucose without the help of oxygen. So, they concluded that fatigue happened at high exercise intensities because the cardiovascular system could no longer supply the muscles with enough oxygen to keep up with muscular energy demands. This would eventually lead the body to rely on the breakdown of glucose without the help of oxygen, which would lead to the buildup of ¨lactic acid¨. But now we know that is not true, in fact, lactic acid is a chemical that your body produces to feed your muscles so that you can move (1). So it really does the opposite of what a lot of people think!!

So what produces muscle soreness? It is still not 100% certain but most scientist think that next-day soreness is more likely the result of damage to muscle and connective tissue, or inflammation. (That is normal, even good, so don´t get scared)

But the real question most people want to know is what they can do to get rid of the muscle soreness that sometimes occurs after training? And like I said in one of my previous post (click here), not that much! Massage, stretching, it feels good and it relaxes but it won´t prevent you from having that uncomfortable feeling the next day (2-4).


  • Cairns SP. Lactic acid and exercise performance: culprit or friend? Sports Med 2006;36 (4) 279-91.
  • Lund et al. The effect of passive stretching on delayed onset muscle soreness, and other detrimental effects following eccentric exercise.Scandinavian Journal of Medicine & Science in Sports 1998.
  • Cheung et al. Delayed onset muscle soreness: treatment strategies and performance factors.Sports Medicine 2003 .
  • Weber et al. The Effects of Three Modalities on Delayed Onset Muscle Soreness.  Journal of Orthopaedic & Sports Physical Therapy 1994.

Tag Cloud