Tag Archives: cycling

Does beetroot juice work for you?

Drinking beetroot juice before a race has become very popular, as it can make you go faster. However, a new study suggests that beetroot juice will not help you if you are already very fit.2631746551_ba1338f5b7

Studies have shown that a single intake or a short term (3-6 days) supplementation of beetroot juice shortens your time on a time-trial event and allows you to tolerate high intensity exercise much better. This is because beetroot contains nitrates (NO3-).

Your body absorbs NO3- and secretes it into your saliva, where your mouth bacteria transform it into NO2-, which is then taken up by your stomach as you swallow. (That is why beetroot has no effect if you use antibacterial mouthwashes.) NO2- becomes NO in tissues which are in need of oxygen, such as working muscles.

NO dilates blood vessels and makes your body more efficient at using oxygen to produce energy. It also improves the contractibility of your muscle fibres.
This is great news, not only for athletes, but also for the elderly who have a reduced aerobic capacity, and for people suffering from hypertension as it will lower their blood pressure.
However, there is a problem. Most studies showing a benefit have been done on sedentary or moderately fit people. Studies on elite athletes on the other hand, are rather disappointing.

To try to understand this better, Simone Porcelli and her colleagues have studied the effect of beetroot juice on 21 young men of different aerobic fitness levels. The VO2 max values of the participants ranged from 28.2 ml/kg/min (sedentary people) to 81.7 ml/kg/min (elite level).
The researchers tested their fitness by a run to exhaustion, a series of 6-min sub-maximal runs on the treadmill, and a 3 km time trial. All the participants performed the tests twice, once after taking 500 ml/day beetroot juice for 6 days and once after drinking the same amount of a placebo for the same time.

There was an inverse relationship between the VO2max of the participants and the benefits of taking beetroot juice. In other words: the participants with the highest VO2max showed the least benefits, while those with the lowest VO2max benefitted most. The researchers also measured the blood levels of NO3- and NO2- of the participants, and noted that the fitter ones showed a smaller increase after drinking beetroot juice.

These results are not easy to explain, and Simone Porcelli and her colleagues have come up with 3 possibilities:

1) NO2- is mainly transformed into NO when tissues need oxygen. Elite athletes will have more blood vessels in their muscles due to many years of training, and it is therefore possible that the right conditions to form NO happen only rarely.

2) Athletes might take in much more nitrates with their normal diets, as they are likely to eat more than sedentary people. In this case the supplements would not matter anymore, and could just end up in their urine. Unfortunately, the researchers did not check the urine levels.

3) Our bodies can also make NO via a completely different pathway, without the need of any dietary NO3-. It is possible that many years of training have optimised this system and fine-tuned the athletes’ metabolism, making nitrate supplements superfluous.

The researchers noticed a higher NO3- and NO2- blood level in the fittest participants before taking any juice, which makes one of the two last possibilities (or both) more likely than the first one.

Whatever the reasons, if beetroot juice does not work for you, you should be happy!

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Exercise and mortality

5797534694_a36e9d8b0dExercising helps you to live longer, whatever the amount you are doing. If you exercise a little, your risk of an early death drops and if you exercise a lot, it drops even more. This is the conclusion of a study published on April 6th in the JAMA.

If you plot “benefits” against “dose” on a graph, most biological systems will show an inverted “U”. Take food for example: if you eat too little, you might die, but if you eat too much, you might also die. If you take a medicine, you have to take the right amount, as taking not enough will have no effect and taking too much is toxic.

Is the same true for exercise? Everybody agrees that you need a minimum of exercise to stay healthy, but some people believe that too much is bad for you. The recent cases of sudden deaths during competitions and the findings of heart rhythm disturbances in older endurance athletes have fuelled the debate.

To answer this question, Hannah Arem and her colleagues have looked at the mortality rates and physical activity levels of 661 137 men and women over 14.2 years.

Sure enough, they showed that having the recommended amount of exercise (a minimum of 150 min of moderate intensity, or 75 min of vigorous intensity endurance exercise per week) resulted in a 30% lower mortality risk compared to not exercising at all. However, any exercise is much better than none, as people who did less than the recommended amount already reduced their mortality risk by about 20%.

Working out more is even better, and exercising 2 to 3 times the recommended amount reduces your risk by 37%, while doing 3 to 5 times more leads to a 39% reduction.

The researchers noticed that those who exercise 10 times or more the recommended amount did not reduce their risk any further, but they could not observe any evidence of harm either.

Can I believe this?

This is very large study, which makes it trustworthy. Moreover, the results are the same for both genders and all BMI ranges.

On the other hand, it is based on questionnaires, and participants can easily over- or underestimate what they are doing or change their habits. However, most population studies about exercise and mortality suffer from these same limitations.

If Hannah Arem is right, concerning exercise, there cannot be too much of a good thing. Even though I have never met anybody running marathons or participating in triathlons for health reasons only, it is good to know we are not harming our bodies.

Keep going, but make sure that you avoid overtraining and injuries!


Arem H, Moore SC, Patel A et al. Leisure time physical activity and mortality: a detailed pooled analysis of the dose-response relationship. JAMA Intern Med 2015; DOI:10.1001/jamainternmed.2015.0533. (Abstract)


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“Aerobic” and “anaerobic” exercise are misnomers

1673932398_5b4211ff72Most people still use the terms “aerobic” and “anaerobic” exercise to name intensity levels, referring to the way your body produces the required energy. However, the way you produce energy is one big continuous chain of reactions, and categorizing exercise in this way can lead to misunderstandings.

In an article in March 2015, Kamir Chamari and Johnny Padulo suggest using the terms “explosive efforts”, “high intensity efforts” and “endurance intensity efforts”.

Energy production: a complex chain of reactions

When you exercise, your body transforms glycogen, glucose, fats or some proteins into a specialised molecule called ATP (adenosine triphosphate), which can then be used by your muscle fibres.

There is some ATP available for immediate use to perform very intensive bouts of exercise, e.g. sprinting, which we should call “explosive efforts”.  After about 6 sec however, it is gone and your body therefore immediately starts topping it up.

Glycogen or glucose is first broken down in the cytoplasm of the cells into pyruvic acid, producing about 3 molecules of ATP. This might not sound as very much, but the system is quick. It does not need any oxygen, even if oxygen is available, and it is therefore often called “anaerobic”. It is everything you need for short, intense bouts of exercise which Chamari and Padulo suggest calling “high intensity efforts”.

Pyruvic acid is then used by the mitochondria of your cells to produce about 32 molecules of ATP in a complex series of reactions. This part of the energy production chain is very productive but it is rather slow. As it requires oxygen, it is often called “aerobic” and the exercise intensity at which you rely most on it is “endurance intensity exercise”.

The bottle neck between high intensity and endurance intensity levels

As the first part of the chain is fast (up to pyruvic acid, without the need for oxygen) and the second slow, there will be a bottle neck between the two of them. If you go harder, the bottle neck will become bigger, and more of your energy will have to come from the first “anaerobic” part of the chain, even if there is plenty of oxygen available.13191313253_05274951ac

Whatever the intensity you are exercising at, you will always be using energy from both parts of the chain. The relative amounts will differ, obviously, but will be determined by the intensity of the effort and not by the presence or absence of oxygen. Labelling a workout as “aerobic” or “anaerobic” is therefore incorrect, and can lead to confusing and misunderstandings.

Lactic acid

If you are going hard, pyruvic acid will be accumulating in your cells due to the bottle neck. It changes then into lactic acid and moves out of the cell. As lactic acid can very easily change back into pyruvic acid, which can used to produce a lot of energy, it is eagerly taken up by other tissues. It is therefore not a waste product at all, but a very important molecule.

However, if you produce more lactic acid than your tissues can take up, the amount in your blood will increase. Your brain uses this rise as a signal that you are going a bit too hard and it will slow you down by making your muscles ache.

As you can have this feeling even if you are doing an endurance workout, it is clear that you are getting energy via every part of the chain.


Chamari K and Padulo J. “Aerobic” and “anaerobic” terms used in exercise physiology: a critical terminology reflection. Sports Medicine- Open.  2015; 1:9. doi: 10.1186/s40798-015-0012-1.

Willmore JH, Costill DL and Kenney W L. Physiology of sports and exercise. Ed: Human Kinetics 2008.


photo credit: <a href=”http://www.flickr.com/photos/33442021@N00/1673932398″>spitting blood</a> via <a href=”http://photopin.com”>photopin</a&gt; <a href=”https://creativecommons.org/licenses/by/2.0/”>(license)</a&gt;

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A happy brain makes you run better

Fatigue during endurance exercise is a weird and complex phenomenon, and scientists are still discussing what influences it. Samuele Marcora’s group has just published an article in Frontiers in Human Neuroscience reporting two experiments studying the effect of visual cues related to happiness and motivation. They showed that such cues can make your unconscious brain think you are working out less hard than you actually are, and that therefore you will keep going for longer.medium_1734834072

Samuele Marcora’s theory about fatigue states that the moment you stop exercising is determined by perceived effort (how hard you think you are working) and potential motivation (the maximal effort you are happy to deliver). This means that you will stop when you are judging that the effort required has become larger than the effort you want to make. This theory is called the psychobiological model of endurance performance. To delay fatigue you could therefore do two things: make the effort seem less important, or increase your motivation.

Our unconscious brain takes in much more information than we realise, especially visually. Only a tiny amount of this information makes it to our conscious attention, but we process all the information unconsciously and it therefore influences our behaviour. To study the impact of the unconscious brain on perceived effort, the researchers therefore set up a study during which they could give participants subliminal visual cues.

In their first experiment 13 participants cycled for as long as they could (i.e. to exhaustion) while looking at a computer screen. They were shown happy or sad faces on a regular basis during the effort, but the images came and went so quickly (in 16 msec) that they did not realise they were seeing them. Every participant performed the experiment twice: once with happy and once with sad faces.

In the second experiment, a well trained competitive endurance athlete cycled 12 times to exhaustion while looking at a screen showing words extremely quickly. The words were encouraging (action, go, lively, energy) during 6 workouts and discouraging (stop, toil, sleep tired) during the other workouts.

In both experiments, the participants cycled significantly longer when exposed to happy faces or encouraging words, and rated the effort as less strenuous. Their mood was not different however, proving that the information had not reached their conscious attention.

Samuele Marcora and his team concluded that these experiments confirm their theory. They also think they provide evidence against the central governor theory of Tim Noakes.

The central governor theory states that your pace, and therefore your fatigue, is determined by your unconscious brain which has to make sure that you get safely over the finish line. According to this theory your pace will thus be determined by “calculations” of your brain based on signals from your body, (e.g. working muscles, glycogen reserves), the environment (temperature, altitude…), but also on messages from your central nervous system, such as motivation, encouragement, knowledge about the course, etc…If you brain is not sure that you will get there safely, it will slow you down –or even stop you- by making you feel tired and reducing the number of muscle fibres you can use.

I am not so sure that the experiments contradict the central governor theory. Is it not likely that subliminal cues would also influence how your brain determines what you can do? Please let us know what you think!

Whatever you think about these theories, it is a good idea to surround yourself by positive images and words, and to smile to every runner you meet.

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Could exercising make you eat more?

Many people exercise in order to lose weight or to keep it under control, but does this make sense? It is beyond doubt that regular exercise will improve your health and well-being, but could it make you hungrier, and therefore make you eat more? If so, it would not make any difference for your waistline…

© Andre Maritz | Dreamstime Stock Photos
© Andre Maritz | Dreamstime Stock Photos

In the November 2014 issue of Nutrients, Stephanie Howe and her colleagues published a review article discussing what we know today about this subject. There are still plenty of questions left, especially concerning women, as most studies have been done on men. Studies on women are indeed much more difficult to conduct since oestrogen influences appetite, and researchers therefore have to control for the menstrual status.

Stephanie Howe and her colleagues explain how hormones influence our appetite, and how exercise influences these hormones. They then discuss several studies which have investigated this problem, and finally they look at the impact of diet.

They come to the conclusion that if you are sedentary, an acute bout of exercise is likely to make you overeat. However, as you become well-trained, your body becomes better and better at matching your energy intake with your expenditure.

They also note that as intense exercise suppresses your appetite more, you have to pay attention to what you are having after hard workouts: you could be tempted to eat too little or too late, which will delay your recovery.

Their article is free for all to read, and I will just try to make a summary in lay terms.

What determines your appetite?

Appetite is very complex and influenced by a long list of factors, such as gastric motility, the status of your energy reserves, temperature, dehydration… Your brain receives all this information via hormonal and neural signals, integrates them and then stimulates or suppresses your appetite.

The involved hormones can roughly be divided into two types: tonic circulating and episodic hormones.

The tonic circulating ones reflect your energy reserves and suppress your appetite when your energy stores are full, and are thus more involved with long term regulation. The best known ones are insulin and leptin.

The episodic hormones on the other hand are involved in short term appetite. Most of them are gut hormones and are released when you are eating or just before a meal. They suppress appetite, except for ghrelin, which makes you feel hungry. As their levels depend on what you are eating, it is easy to see why some diets make you feel fuller than others. Foods rich in fibres for example, will allow you to take in fewer calories without feeling hungry.

As mentioned earlier, oestrogen and progestogen also influence appetite, which explains why many women tend to gain weight during the menopause.

All these hormones act on the hypothalamus (an organ in your brain), which integrates the information and controls your appetite. Despite this sophisticated system, other factors, such as the sight and smell of food, cultural and social elements or the time of the day, also influence your desire to eat and can even override the hormonal influences.

Working Up Sweat (ID: 74747)
© Vlad | Dreamstime Stock Photos

Studying appetite

Researchers who want to study the influence of exercise on appetite therefore have to measure the amount of the appetite hormones in your blood as well as your desire to eat. The first can easily be done by a blood test, and the latter is often done using a visual analogue scale (VAS) or by measuring what the participants eat at a buffet in the research centre. A visual analogue scale typically consists of a series of numbered boxes (e.g. from 1 to 10), where the first and the last ones correspond to the extremes (e.g. “I’ve never been so hungry” and “I couldn’t eat anything at all”). You can then mark the box that corresponds best with how you are feeling.

Appetite hormones and exercise

A bout of aerobic exercise decreases your appetite by influencing your gut hormones. This effect is more pronounced in weight baring and more metabolic demanding exercise, such as running, than in non weight baring exercise.

Intense exercise influences the hormones more than moderate exercise. This suppression is only temporarily, but it can be enough to interfere with your next meal, and therefore with your recovery. This explains why it is so hard to eat anything solid after a race!

Resistance exercise on the other hand, does not seem to have an influence.

Are you really eating less?

It is not because your hormones are suppressing your appetite that you will eat less. As I am sure you know by experience, you can override your appetite if the food looks nice or if you believe you have good reasons to eat (e.g. I have spent a lot of calories, I need some comfort after all this hard work…).

© Ragne Kabanova | Dreamstime Stock Photos
© Ragne Kabanova | Dreamstime Stock Photos

Most studies looking into energy intake after exercise do so by measuring what the participants eat at a buffet offered by the researchers. This does not necessarily simulate real life and might therefore lead to false conclusions. Even so, there is evidence that trained people are able to match their energy intake to what they have spent, and can therefore maintain a healthy weight. Sedentary people however, are more likely to overeat after an acute bout of exercise.


Most athletes are health conscious and will choose a diet rich in fruit, vegetables, whole grains etc…Such a diet will contain fewer calories per volume than an unhealthy one. It will also make you feel full much earlier. For the vast majority of us this is excellent news, but the combination of a low calorie diet, intense exercise and appetite suppression can become a trap for some athletes. It can lead to a chronic negative energy balance, and is more often seen in women engaged in sports for which being lean is an advantage, such as long distance running. It can lead to menstrual disorders with all their complications: poor bone health, injury, illness…


If you want to recover quickly, you have to refuel as soon as you can. This can be difficult if your appetite is suppressed. Other factors such as fatigue, dehydration, an elevated core body temperature or gastrointestinal problems can make things even trickier. A good recovery drink can help you out though, as drinking is much easier than eating.


Altitude training for endurance athletes

© Ichtor | Dreamstime Stock Photos
© Ichtor | Dreamstime Stock Photos

There is no doubt that if you want to compete at altitude, you will first have to acclimatize to the lack of oxygen. If not, you will probably not perform as well as you could and you will certainly put your health at risk. However, does training at altitude help you to perform better at sea level? The jury is still out…

Lorenzo Pugliese and colleagues have published the latest article about this question in the September issue of the Journal of Sports Science & Medicine. It is an observational study of two elite endurance athletes, a race walker and a marathon runner, who used altitude training as part of their preparation for the Athens Olympic Games (2004). As both of them obtained gold medals, it must have worked for them, even though we do not know for sure what would have happened if they had stayed at sea level.

Even though altitude training is popular between endurance athletes and coaches, it is still controversial between scientists. In theory it should work of course: as the air pressure is lower at altitude, your body learns how to use oxygen more effectively, what then allows you to perform better when you are back at sea level. The best known effect is an increase in red blood cells, and thus in haemoglobin mass, although there are also adaptations at the level of the muscles and the mitochondria. This increase is triggered by the hormone erythropoietin or EPO, which is produced by the kidneys. However, some people produce less EPO than others and there are therefore important inter-individual differences between the effects of altitude on athletes.

Training hard and altitude

If you want to win endurance races, you need to be able to train at fast paces. Running fast for a long distance is difficult to do at altitude when you are not used to it, as your muscles need more oxygen than you can deliver to them. This is even more so for elite athletes, whose muscles are trained to perform at an optimal level. If you do not train intensively enough for a period of a time, your muscles become detrained, and anything you might have gained by improving your oxygen metabolism will be useless.

While you are acclimatizing, you will face some other problems:

  • Sleeping can be difficult as you are short of breath.
  • As soon as you arrive at altitude, your plasma volume (=the water part of your blood) will decrease, as your body wants to increase the red blood cell concentration and producing new red blood cells takes some time.
  • The air is colder and drier which can easily lead to dehydration.
  • As your muscles cannot extract as much oxygen from your blood as they do at sea level, your VO2max is in effect reduced. Running at the same speed as at sea level will therefore mean working at a higher level of your VO2max, which will feel harder.
  • You are more vulnerable to infections.

All these factors will make it difficult to train at the required level during the acclimatization. Once you are used to the altitude the situation will improve, but in the meanwhile you might have lost valuable time and your legs might have lost speed.

Athletes and coaches have therefore developed live-high-and-train-low camps, whereby they live at altitude and train at lower level. Alternatively, they might do live-low-and-train high camps, whereby they perform some of their sessions at altitude to have an additional training stimulus.

 Olga Vasilkova | Dreamstime Stock Photos
Olga Vasilkova | Dreamstime Stock Photos

Reasons for the controversy

Studies about altitude training contradict each other, whatever formula they use (live-high-and-train-high, live-high-and-train-low or live-low-and-train-high). It is of course possible that athletes and coaches have noted some benefits that are too small to be measured by scientists. As major championships are won or lost by seconds, such very small benefits can make a big difference indeed.

It more likely that the controversy is due to a lack of control groups: in a good study you would compare similar athletes doing the same training at altitude as at sea level, and you would take into account that some people do not react as well as others. In practise such a study is very difficult and expensive to conduct. To complicate matters even further, there could be a placebo effect, as most athletes believe that altitude training is beneficial.

Lorenzo Pugliese’s athletes followed a live-high-and-train-high program. However, they were able to train at the same running/walking pace as at sea level and, according to Pugliese, this is the reason why the camp worked so well for them. Both of them had extensive altitude training experience and that might well have been the reason for their success. Maybe a three week camp so now and then is simply not enough, and you might need to live for a long time at altitude to reap the benefits? This would explain why so many top endurance athletes are born and/or live at altitude. Bad news for all of us who live at sea level though…


D M Bailey and B Davies. Physiological implications of altitude training for endurance performance at sea level: a review. Br J Sports Med. 1997; 31:183-190.

L Pugliese, FR Serpiello, GP Millet et al. Training dairies during altitude training camp in two Olympic champions: an observational case study. J Sports Sci Med. 2014; 13(3):666-672. eCollection 2014.

Strength after endurance or endurance after strength training?

All endurance athletes (runners, cyclists, cross-country skiers…) need some strength training. Personally, I prefer to train for endurance and strength on separate days, but for many of us it is more time-effective to combine the two in one session. If that is your case, what do you do first?

© Phil Date | Dreamstime Stock Photos
© Phil Date | Dreamstime Stock Photos

This is an important question, as research has shown that endurance and resistance training lead to different adaptations. Strength training leads to increased muscle mass, while endurance training will allow you to use the available energy and oxygen more effectively and exercise for longer. If you combine both in one session, you will not have any recovery between them and it might be impossible for your body to benefit fully from both. If so, the order in which you do them (first endurance and then strength or the other way around) is important.  Getting it wrong could make a big difference.

Most, if not all, runners I know will start by endurance exercise, and according to Moktar Chtara and his colleagues that is indeed the right thing to do. They divided 48 young men in five groups. The first group performed endurance training only, the second strength training only, the third endurance plus strength and the fourth strength plus endurance workouts. The fifth group did not train and served as a control group. After 12 weeks the endurance plus strength group outperformed every other group during a 4 km run time trial, and their VO2max had improved most.

In the September issue of Medicine & Science in Sports and Medicine however, Moritz Schumann and colleagues published a study suggesting that this does not matter for cyclists. They divided 34 young men in two groups, one of which performed endurance plus strength workouts and the other strength plus endurance. The endurance part of the sessions consisted of cycling, and the strength part of exercises for all the major muscle groups but mainly for the legs.

Both groups improved in strength, VO2max and time to exhaustion, but after 24 weeks there were no significant differences between the groups. The researchers concluded that as endurance cycling is biomechanically similar to many of the strength exercises, they could enhance each other’s effect. Running is of course different.

Surprisingly, Schumann could not notice any significant reduction in body or visceral fat, or in cholesterol levels. Studies whereby the participants perform strength and endurance workouts on separate days on the other hand, typically do show improvements.  The researchers could not really explain this discrepancy: did the participants not train frequently enough (as they did two sessions worth in one go)? Only further studies can figure this out…

In the meanwhile, I’m going to continue planning my endurance and strength workouts in separate days.


M Chtara. K Chamari, M Chaouachi et al.  Effects of intra-session concurrent endurance and strength training sequence on aerobic performance and capacity. Br J Sports Med. 2005; 39:555-560.

GA Nader. Concurrent strength and endurance training: from molecules to man. Med Sci Sports Exerc. 2006; 38(11):1965-1970.

 M Schumann, M Kuusmaa, RU Newton et al.  Fitness and lean mass increases during combined training independent of loading order. Med Sci Sports Exerc. 2014; 46(9): 1758-1768.

A cold drink to exercise in the heat?

Could consuming cold drinks or ice slush during workouts in the heat help you to perform better? Scientists have been wondering this for many years.

Theoretically it makes sense: as your brain’s main objective is to keep you safe, it will force you to slow down or even stop if it presumes that your core temperature could increase to dangerous levels before the end of the workout. Anything that helps you to keep your core temperature down is thus beneficial, and as cold drinks could act as a heat sink they could be helpful indeed. Scientific studies however, have been inconclusive.

© Dnally | Dreamstime Stock Photos
© Dnally | Dreamstime Stock Photos

Florence Riera and her colleagues have just published the latest study about this problem in PlosOne. They compared the effects of a cold (3 C), ice slush (-1 C) or neutral drink (23 C) with or without menthol flavouring on the performances of 12 trained male cyclists in hot and humid conditions.

The cyclists were randomly assigned a beverage and performed a 20 km time trial in the lab, which means that each of them did the test 6 times (once with each beverage). The performance was better using ice slush whatever the aroma, and better with menthol whatever the temperature. Ice slush or cold water with menthol flavouring was therefore the best.

The researchers concluded that a cold or ice slush drink interferes with the rise in core temperature, allowing you to exercise harder without – or with a smaller- increase in core temperature. 

Menthol usually provokes a sensation of freshness, it is a bit stimulating and it improves the airflow (that is why you use menthol lozenges when you have a cold), but exactly how it works is unknown.

Drinking ice slush is probably possible when you are cycling on a turbo trainer or in the gym, but what can you do if you are a road cyclist? You could try to cool down your core in advance, and researchers have shown that ice vests or cool water baths are helpful indeed.

Pre-cooling techniques are usually unavailable for recreational athletes, but cold drinks can easily be obtained before the start of any event. Christopher Byrne and his colleagues therefore wanted to find out if you could pre-cool yourself with cold drinks.

Seven male cyclists ingested 900 ml cold (2 C) or neutral (37 C) water over 35 minutes before cycling as many kilometres as possible for 30 minutes in a lab. When the athletes drank cold water they cycled 2.8% further and their core temperature (as estimated by rectal temperature measurements) was lower at the end of the test. They felt really cold before starting off though, and one of them was even shivering. Most of them needed to urinate before the exercise. Probably not a very pleasant experience….

© Denise Scott Jackson | Dreamstime Stock Photos
© Denise Scott Jackson | Dreamstime Stock Photos

I wonder if this kind of pre-cooling is possible for runners, as such a large amount of fluid is likely to create gastro-intestinal discomfort? I guess that the only thing runners can do is to get acclimatised and to accept that we will be slower…Or do you have a better idea?


C Byrne, C Owen, A Cosnefroy et al. Self-paced exercise performance in the heat after pre-exercise cold-fluid ingestion. J Athl Train. 2011; 46(6): 592-599.

 F Riera, TT Trong, S Sinnapath et al. Physical and perceptual cooling with beverages to increase cycle performance in a tropical climate. PLoSONE 9(8): e103718. doi:10.1371/journal.pone. 0103718. (Accessed 09/08/2014).

R Tucker. The anticipatory regulation of performance: the physiological basis for pacing strategies and the development of a perception-based model for exercise performance. Br J Sports Med 2009; 43: 392-400.

 Disclaimer: this article is for general information only, and does not replace medical advice. It cannot be used to diagnose or guide treatment. If you have any concerns or questions, you should talk to a qualified health provider.

Alcohol and recovery from exercise

We all know that we should have some carbohydrates and proteins to recover faster after a hard workout, but what happens if at the same time we have a few drinks to celebrate the achievement? How will that affect the recovery?

© Dana Rothstein | Dreamstime Stock Photos
© Dana Rothstein | Dreamstime Stock Photos

In 2003, Louise Burke and her colleagues studied the effect of alcohol on the rebuilding of glycogen stores after an exhaustive bout of cycling. They noticed that alcohol slowed down the glycogen storage during the first 8 hours, but after 24 hours there was no difference anymore. This means that if the early phase of recovery was poor, there must have been a period of catching-up. They also showed that the main problem with drinking alcohol is that it makes it unlikely that you are taking in enough carbohydrates to rebuild your glycogen reserves, and, as you cannot make glycogen from alcohol, you could be losing out.

However, recovery is not only about glycogen, but also about rebuilding damaged muscle fibres. To do so you need to make new proteins, and taking in high quality protein soon after your workout can help your body to do so.

In a study published in PloSOne, Evelyn Parr and colleagues showed that drinking alcohol during your recovery hampers the protein synthesis. 8 men performed a workout comprising resistance, continuous and interval exercise. Immediately and 4 hours afterwards, they had a drink containing protein, protein with alcohol or carbohydrate with alcohol. The study was constructed as a cross-over design, which means that each volunteer performed the workout three times, using each time a different drink at the end. The researchers took muscle biopsies before the exercise, and 2 and 8 hours afterwards.
As you can see from this graph from Evelyn Parr’s article, alcohol impaired protein synthesis by 24%, even if the athlete had enough protein during his recovery. In real life, it is likely that the athlete would not take in proteins, and that the situation would be at best similar to having the alcohol and carbohydrate drink. That would mean 37% less protein synthesis.

The athletes in this study had about 12 standard units alcohol in their drinks. This sounds awful, but according to the researchers it corresponds to the mean amount used by team athletes during a drinking binge (!). We do not know yet what a safe amount of alcohol would be, or if that exists. We need therefore more research. Until we have that, it is better to be careful…


Burke LM, Collier GR, Broad EM et al. Effect of alcohol intake on muscle glycogen storage after prolonged exercise. J Appl Physiol. 2003; 95: 983-990.

Parr EB, Camera D M, Areta J L et al. Alcohol ingestion impairs maximal post-exercise rates of myofibrillair protein synthesis following a single bout of concurrent training. PloSOne 2014; 9(2): e88384 doi: 10.1371/journal.pone.0088384.

Low volume, high intensity interval training


Keeping fit or becoming fitter by regular exercise is important if you want to stay healthy. The usual advice is to perform at least 150 min of exercise a week, but could shorter, more intense workouts be just as good or even better? This is an important question, as for most people lack of time is a real issue.

Competitive athletes of all levels use interval training, -together with continuous workouts-, as it improves their fitness more and quicker than continuous endurance exercise. It is also less time consuming. Interval training sessions consists of bursts of intense exercise (e.g. 3 to 5 min at 85 to 90% of your maximal heart rate) followed by short periods of easy exercise.

Low volume, high intensity interval training or HIIT takes the idea of saving time a step further. It consists of 3 or 4 bursts of 30 sec “all out” exercise at your absolute maximum, with about 4 min of easy exercise after each burst. This session is typically repeated 3 times a week. Even though each HIIT session is preceded by a thorough warming-up and followed by a cooling down, it would typically take only about 3 x 25 to 30 min = 75 to 90 min a week, and it could therefore be a solution for sedentary people who are short of time.

However, there is a problem: going all out for 30 sec is much harder than you imagine. In labs, volunteers usually require plenty of encouragement and most of them feel nauseous or light headed. Moreover, it is likely to put you at a higher risk of injuries, and it is not sure yet if it is safe for people with health problems. Scientists have therefore wondered if a longer exercise burst at a slightly lower intensity would be easier to manage.

Low volume HIIT sessions are usually performed in labs, using specialised material. It is therefore not clear yet if these sessions could also be done without equipment, e.g. by running in your local park.

Helen Lunt and her colleagues have investigated just that, and published their results in January 2014.

English: Fitness trail station, North Bay Park...

49 previously sedentary volunteers were divided in 3 groups. One group, called “walk”, performed 30 minutes of continuous endurance exercise by walking. Another group, “ait” undertook an interval training session by jogging or running for 4 minutes at 85- 95% of their maximal heart rate followed by 3 minutes of easy walking. They repeated this 4 times per session. The last group, “mvit”, ran all-out for 30 sec up a slope at maximal volitional intensity, followed by a 4 min of easy walking. They started off by doing this exercise burst 3 times, and tried to increase the number of repetitions per session. All the participants warmed up before their workout and cooled down afterwards, and performed 3 workouts a week. All the sessions were hold at a public park and supervised by the researchers. The aim was to keep going for 12 week and to compare the VO2max of the participants before and after this period. VO2max is a measure of your aerobic fitness, and higher values are indeed linked to better health and longevity, even in overweight or obese people.

Unfortunately, 1 participant of the walk group, 3 of the ait and 4 of the mvit group had to drop out because of injuries related to the exercise.

At the end of the 12 weeks, the ait group had improved their VO2max more than the walk and mvit groups. The walk group had experienced the least adverse effects, as only one the participants had to stop.

The researchers concluded that interval training can help you to improve your fitness without spending as much time as you would if you performed continuous endurance training, but it comes at a price: your risk of being injured is greater. The results of the mvit group were disappointing, but this might be due to the fact that so many of them dropped out. Moreover, the time gained was not that important: in practice the walk group ended up by working out for 116 min week, the ait group 74 min and the mvit 46 min.

Could interval training help me if I’m sedentary?

Interval training can indeed improve your fitness quicker than continuous training, but it comes at a price: it is much harder work. Moreover, it might not be safe for people with health problems, and you should therefore first check with your doctor to see if it is ok for you. As it is hard work, it is better to do it under supervision by a fitness professional, who can make sure that you work out at the right level and who will encourage you.

Is low volume HIIT useful even if I’m used to training?

Most athletes are reluctant to change a training schedule that works, and there are therefore not many studies evaluating low volume HIIT. Moreover, as they do many different sessions, it is difficult to find out if improvements are due to the low volume HIIT or to another part of their training schedule.

If you are a competitive athlete, you are probably used to interval training. A proper low volume HIIT session however, is very hard, and might be too hard to do without continuous verbal encouragement from your coach. As always, everybody is different, and you have to find out what is best for you.

Disclaimer: this article is for general information only, and does not replace professional advice. It cannot be used to diagnose or guide treatment. If you have any concerns or questions, you should talk to a qualified health provider.


A P Bacon, R E Carter, E A Ogle et al. VO2max trainability and high intensity interval training in humans: a meta-analysis. PlosOne. 2013; doi 10.1371/journal pone.0073182

M J Gibala, J P Little , M J MacDonald et al. Physiological adaptations to low-volume, high-intensity interval training in health and disease. J Physiol. 2012; 590(Pt5): 1077-1084.

H Lunt, N Draper, H C Marshall et all. High intensity interval training in a real world setting: a randomized controlled feasibility study in overweight inactive adults, measuring change in maximal oxygen uptake. PLoSOne. 2014; 9(1): e83256.


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