The title might be a little provocative, the proposition would have been in my PhD thesis if my promoter wouldn’t have been against it. “Stick to the science” he would tell me. “If you want to ventilate an opinion you can do so in the pub.” And in some ways he was right. I hadn’t done research with athletes, only with lung patients. So this statement, which was only based on my personal experience, had no scientific value. The same statement the other way around would have made more sense. “Lung patients are like athletes”. I have seen that in their struggle and determination to improve; to get better. But that is not the point I want to make here. Athletes are like lung patients. Now, years later, after I have started working with athletes, day to day practice shows me I was right then. Let me explain.
When I state that athletes are like lung patients, I refer to their exercise limitation. This should not be mistaken with exercise capacity. Exercise capacity is the ability to perform exercise, whether it is normal daily exercise like going to the grocery store, or it is sports like climbing a mountain on your bicycle. In exercise physiology we like to measure exercise capacity. Our favorite tool is the bicycle ergometer, where we can measure very accurately the amount of energy someone can produce over a certain time. We call this Watts. It shouldn’t be a surprise that an athlete has a better exercise capacity, i.e. can produce more Watts, than most lung patients. But it is not the exercise capacity, but exercise limitation that makes (some) athletes and lung patients alike. And exercise limitation is the factor that limits our exercise capacity. It is the reason that we can’t produce more Watts than we do.
In “normal” healthy untrained individuals, exercise during a maximal exercise test is limited by either the heart to pump oxygen around, or the enzymes in the muscles to process the oxygen. Some researchers1 even say it is the barrier between blood and the muscle. But one thing is clear, it is never the lungs. A healthy untrained individual uses only 70 to 80% of their maximal ventilator capacity. In other words, this individual will never breathe as hard as he/she can during maximal exercise. And they don’t need to. Before they reach maximal ventilation, they are already stopped by another limiting factor.
What happens if we start training? Let’s focus on aerobic endurance training. Muscles are easily trainable. If we train muscles, they get bigger, with more oxygen processing enzymes and more blood vessels to transport the oxygen. The heart is also a muscle and with aerobic endurance training, it gets bigger as well.
In well-trained cyclist, an enlarged heart (which we call athlete’s heart) is not uncommon. An athlete’s heart is associated with a low resting heartrate. Where a “normal” heart beats around 70 times a minute, the heart rate of a well-trained cyclist can be as low as 30 beats per minute. This lower heart rate is the effect of an increased stroke volume, being the amount of blood that is pumped out of the heart with each heartbeat. So with a lower heart rate and a higher stroke volume at rest, the same amount of blood is pumped around, to ensure sufficient oxygen supply to the body. During exercise this athlete’s heart gives a big advantage. Maximal heart rate is not very much influenced by the size of the heart. So with an increased stroke volume and a normal maximal heart rate, more blood can be pumped around during (maximal) exercise.
More blood means more oxygen. With a larger capacity to process this oxygen in the muscles, one can imagine that exercise capacity will increase, as is the purpose of training. But with the increase of exercise capacity, a greater load will be put on the ventilation. And the lungs, in contrast with muscles and the heart, are not very easily trainable with aerobic endurance training. There are even suggestions that with increase in heart size, the lung capacity will decrease, as lungs and heart are both trapped in the thorax together. So with no changes in the maximal amount of air we can breathe, the limitation to exercise shifts from the muscles and/or heart to the lungs. Not seldom do I see athletes at my lab, who use the full respiratory capacity during maximal exercise, without reaching their maximal heart rate. And this is exactly what we see in patients with lung diseases such as asthma, COPD or pulmonary fibrosis. They also use their full ventilator capacity. In this case not because the strength in the muscles and heart, but rather because of a weakness in the lungs.
What can we learn from this; how can we use this? First of all, we can use this as a measure of potential. Ventilation as limiting factor will give less room for improvement of maximal exercise capacity than the heart or muscles as limiting factor. This has consequences for training. With a cardiac or muscle limitation, the focus should be on improving these systems. This can be done with either long aerobic endurance training or high intensity interval training. Probably a combination (also known as polarized training) can be beneficial. When ventilation is the limiting factor, the main focus of the training must be shifted. Of course, training effects on muscles and heart must be maintained, but the main focus must be in increasing the level of the first ventilatory threshold (better known as anaerobic threshold or AT). This is the point where the body starts compensating for the accumulation of acid that comes from strenuous exercise. To maintain an acid balance in the body, ventilation will increase to get rid of carbon dioxide. The more we can shift this ventilatory threshold towards maximum exercise, the less ventilator strain there will be. This will improve maximal exercise capacity. To do so, the majority of the training has to be around the first ventilator threshold (AT). So these are the “high intensity” endurance training just below AT and the 5 tot 15 minute block training (also called aerobic resistance training) just above AT.
Furthermore, in subjects with a ventilatory limitation, inspiratory muscle training might be beneficial. The scientific evidence for this is weak, with some studies showing good effects and some showing no effect of inspiratory muscle training on exercise capacity. None of these studies did however specific target on athletes with a ventilator limitation. Therefore, as was also stated in a systematic review with meta-analyses, the use of inspiratory muscle training in athletes should be matched with the demands of the athlete2. So find out your limitation and optimize your training! Good luck.
- Wagner PD A re-analysis of the 1968 Saltin et al. “Bedrest” paper. Scand J Med Sci Sports. 2015 Dec;25 Suppl 4:83-7.
- HajGhanbari B1, Yamabayashi C, Buna TR, Coelho JD, Freedman KD, Morton TA, Palmer SA, Toy MA, Walsh C, Sheel AW, Reid WD Effects of respiratory muscle training on performance in athletes: a systematic review with meta-analyses J Strength Cond Res. 2013 Jun;27(6):1643-63..