Early morning workout not good for health
They claim the body’s immune system is not ready to cope with intense exercise first thing in the morning.
A pre-breakfast work-out puts the exerciser at greater risk of infection than the same level of exertion after work, the study by sports scientists suggests.
Evening is the best time to exercise, they say, because a stress hormone which damages the immune system is at its lowest level then.
The researchers, at the Sports Science Department at Brunel University in West London, examined the levels of cortisol, a stress hormone that can suppress the immune system, in 14 British competition swimmers.
The swimmers, with an average age of 18, were put through their paces at 6am and 6pm on separate days. They were told not to drink, smoke or have sex for 12 hours before each session.
The scientists took saliva samples from the swimmers before and after the exercise.
Tests revealed cortisol levels were lower – and therefore better – in the evenings.
But levels of immunoglobulin A (IgA) – a marker for antibodies in the blood that help fight off infection – were down sharply in the morning, meaning swimmers were running the risk of picking up infections.
The study, published in the British Journal of Sports Medicine, revealed that the same findings would apply to almost any athlete, whether professional or amateur and regardless of the level of fitness.
Dr Lygeri Dimitriou, who led the study, said: ‘These findings suggest the body clock – or circadian rhythms – have a considerable impact on the immune system. The best time of day to train is in the evening, when baseline levels of cortisol and those produced after exercise are both lower than in the morning.
‘Salivary flow rate, which also helps to protect against bugs and viruses, also peaks in the evening.
‘Exercising in the morning could possibly increase susceptability to infection compared to an afternoon training session.’
Dr Dimitriou added: ‘At the very least, early morning training sessions should be avoided by those returning to training after injury or illness, those close to competition and when stress levels are higher.’
