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When is the best time to exercise to get the most from your workout?
Your muscles, fat and other cells respond differently to exercise depending on the time of dayPanoramic Images/AlamyUsain Bolt smashed the 100-metre sprint record at the 2009 World Championships in Athletics in Berlin in a floodlit stadium under an inky night sky.This article is part of a series on fitness that answers eight questions about exercise and its influence on our bodies and minds. Read more here.This was no coincidence: when it comes tosporting prowess, timing matters. For activities relying on sheer muscle power andendurance, evening or late afternoon arewhenmost world records have been set, probably due to assistance frompeaks in thedaily rhythms ofanumber of the bodys key physiological outputs.But what about everyday exercisers? Is therean optimal timeof day, or month, togetthe most out ofworkouts and reduce therisk of injury?AdvertisementWhichever aspect of sport you look at whether its sports medicine or exercise response time of day matters, says Qing-Jun Meng at the University of Manchester, UK. Later afternoon or evening is when our bodytemperature peaks, resulting in fastermetabolic reactions and nerve signal transmission compared with the early morning. Connective tissue is also more flexible in the afternoon, while our reserves of glycogen the biochemical energy source our muscles draw on during moderate to intense exercise have had time to be replenished.Circadian rhythmsOther physiological parameters also varyover the 24-hour period, which could berelevant for exercise: testosterone secretion peaks at around 9am; coordination tends tobebest at around 2.30pm; reaction times arefastest at around 3.30pm; cardiovascular efficiency, muscle and grip strength peak at 5to5.30pm.Circadian rhythms exist in almost all cellsof the body and regulate key processes relating to exercise and metabolism, says Meng. Depending on what time you exercise, your muscle, fat and other cells will also be inadifferent state, and they will respond to exercise differently.Indeed, a recent study by Renske Lok at Stanford University in California and her colleagues found that, on average, Olympic swimmers are more than athird of a second faster if they compete in theevening rather than in the morning. In40per cent of [swimming] races, the time-of-day effect isbigger than the difference between finishingfirst or second, they wrote.For sports involving more technical skills, such as tennis or soccer, peak performance tends to arrive a little earlier possibly because our cognitive abilities usually peak in the late morning or early afternoon. Soccer players juggle and chip the ball with the greatest precision at around 4pm; tennis players servestend to be faster in the evening, but more accurate in the morning. Of course, thesetimings are based on averages in reality,larks who tend to wake early and bemore active in the mornings will be at theirbest earlier, while owls, who naturally come to life in the evenings, will peak later.What are the implications of all this for howthe rest of us time our exercise? Last year, Fabienne Bruggisser at the University of Basel in Switzerland and her colleagues pored over the evidence from 26 previous studies and found little to support or refute the idea that training at a specific time leads to better performance or improved health outcomes.They did, however, find some evidence tosupport training at the same time of day asarace or competition to improve physical performance at this time. In other words, morning training improves morning performance more than evening training does,and vice versa. However, given that thestudies only included young male participants, it remains to be seen whether such conclusions apply to the general population, the authors said.Monthly cyclesWomen may have a further layer of complexity to consider. In recent years, several womens soccer teams, including Chelsea FC Women, have started tailoring their players training programmes around their menstrual cycles, claiming that doing so boosts their performance and reduces their risk of injury.The theory is that when oestrogen is high and progesterone is low thats an anabolic environment; its a good [time] to work hard, says Stuart Phillips at McMaster University in Canada. Yet when he and his colleagues recently reviewed the evidence for an influenceof menstrual cycle phase on exercise performance, they found it was remarkably thin. The evidence that we do have suggests that theres no merit to it, says Phillips.Even so, he doesnt dismiss recording symptoms and using them as a guide to scheduling training. I know some women aregenuinely adversely affected at certain phases of their cycle with menstrual-related symptoms: cramps, backaches, a lack of motivation, fatigue, etc. And for women athletes that do experience symptoms, tryingto manage them and making their coachaware of them is a great thing, he says.But as for a blanket, this-is-the-way-you-do-things-type approach, theres no consistent pattern to performance when its studied systematically, and we know gold medals andworld records have been set at different [menstrual] phases, and on and off the contraceptive pill.Meng believes there may be yet other factors to consider. Generally, he advocates exercising in the morning especially outdoors as this exposes people to bright light, which helps to synchronise our biological clocks with the time of day. Our bodies work best when the clocks inall our cells and tissues are aligned with oneanother, and with the time of day.And even if there isnt a best time of daytowork out, there may be a time to avoidexercise. Recent research by Meng andhis colleagues has suggested that a key mechanism for keeping the biological clocks inour bones and joints synchronised with those in other tissues is exercise, and that if mice are encouraged to exercise when they would usually be sleeping, this causes their skeletal clocks to desynchronise from their brain clocks a phenomenon Meng has namedskeletal jet lag.Though the implications for injury and physical performance in humans are unclear, further experiments in mice suggest that consistently exercising during their equivalent of night-time leads to the activation of genes that are associated with osteoarthritis. We suspect that if you did this over a long period of time, it could be really detrimental, says Meng.Topics:
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