Tag Archives: training

“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;

photo credit: <a href=”http://www.flickr.com/photos/65483692@N06/13191313253″>Limassol Marathon, #Cyprus 2014</a> via <a href=”http://photopin.com”>photopin</a&gt; <a href=”https://creativecommons.org/licenses/by-nd/2.0/”>(license)</a&gt;


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.

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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