As we reach the end of the school holidays, many parents will be feeling exhausted after running around with their children for two weeks.
The children, however, will probably still appear energised and ready for their next adventure with no hint of tiring out. This endless energy that children seem to have has been the subject of a new scientific study and the results show what every parent already knows - the energy levels of children are greater than those of even professional endurance athletes.
Published in the journal Frontiers in Physiology the research compared the energy output and post-exercise recovery rates from children aged 8-12, untrained adults, and endurance athletes aged 19-27.
The children and untrained adults had not been participants in regular vigorous physical activity before. The endurance athletes were all national-level competitors in triathlons or long-distance running and cycling that trained more than six times a week.
The volunteers were asked to carry out two cycling-based exercise tasks staggered over two different days, one was to measure their aerobic metabolism and the other their anaerobic capabilities.
Aerobic means with oxygen and aerobic exercise stimulates the body so that the heart rate and breathing rate increase in a way that can be sustained for the exercise session.
The body is able to pump oxygenated blood around the body, which delivers the oxygen required to the muscles working in the exercise.
The aerobic exercise test involved having the volunteers sprint on a bicycle which was set up to provide resistance against their pedalling for seven seconds. After this quick session, the volunteers were given a one-minute recovery period before starting again.
Anaerobic exercise is a high-intensity but short-lasting activity where the body's demand for oxygen exceeds the supply of oxygen available.
The body copes by relying on energy sources that are stored in the muscles and this results in a by-product being produced called lactic acid. Too much lactic acid accumulating in the muscles from anaerobic exercise results in the muscles starting to fatigue.
The anaerobic exercise test involved the volunteers cycling as fast as they could for 30 seconds non-stop using a method known as the Wingate Cycle Test.
During and after each test, the volunteers had their heart rate, oxygen levels, acidosis and blood lactate levels measured, which assessed both how their bodies produced energy as well as how they recovered from exercise.
The results were fascinating - in all of the tests, the children outperformed the adults in both how much energy they had and how quickly they recovered after an activity.
The study found that children are able to utilise aerobic metabolism more than adults during exercise, which resulted in them being less tired during the high-intensity activities.
The children's heart-rate recovery and ability to remove blood lactate also recovered more quickly than the endurance athletes, meaning that their anaerobic metabolism was also superior and their muscles fatigued less.
The only area where the athletes beat the children was in the amount of power they were able to create due to their larger and stronger muscles.
Although the study only used a relatively small number of participants, its results support other studies that have looked at how children seem to be able to sustain large amounts of exercise and recover quickly from high-intensity activities.
The good news is, the science suggests that the more aerobic or cardio training adults can do, the more childlike they can train their bodies to be.
The bad news is, the almost infinite energy source that children seem to have will continue to exhaust their parents for years to come.
Dr Michelle Dickinson, creator of Nanogirl, is a nanotechnologist who is passionate about getting Kiwis hooked on science and engineering. Tweet her your science questions @medickinson