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The previous articles dealt with the best kind of aerobic activities and their length, frequency and intensity. Now it is time to talk about “when” to practise them. It may seem a minor problem, and it actually is, since doing some exercise is far more important than conditioning it to a specific timetable. However, the choice of time can partially influence the slimming effectiveness of the activity. This may seem strange because the consumption of calories is always supposed to be the same, no matter what time we practise aerobics (but this is not actually so). In fact, we have to bear in mind that aerobic activities with energy purpose can consume both sugars and fats, according to the availability of the energy substrate. I will be more clear: if we practise aerobics after eating a big piece of cake, we cannot be under the illusion that we will burn our adipose tissue or the circulating fatty acids coming from it. Instead, for energy purpose, we will use the sugars partly present in our muscles as well as those coming from the cake. Our body mainly uses sugars as fuels for a dynamic purpose, and the insulin stimulated by the hyperglycaemia induced by the consumption of the cake stops lipolysis. Therefore, if we aim at stimulating the oxidation of fats in order to lose weight, we have to train at a time of the day when glycaemia and the glycogen levels are low, in order for our body to use fats mainly for energy purpose. This basically happens in the morning, on an empty stomach. Being on an empty stomach for 8-10 hours favours lower glycaemia and is also the right condition for the secretion of GH (lipolytic hormone) induced by physical exercise. This is a successful approach for the majority of people, but non for everyone. There are two categories of people who do not derive benefit from this approach: those with extremely low metabolism and hyperadrenocortical people. The people whose metabolism has slackened – for example due to a too restrictive or too protracted diet – have an even slower metabolism in the morning, on an empty stomach. This can be deduced by a body temperature below 36,5°. In this case breakfast, especially based on proteins, can increase thermogenenis, inciting the metabolism and – without increasing glycaemia levels – predispose the body to burn more. Hyperadrenocortical people tend to have particularly high cortisol levels in the morning. The circadian rhythm of cortisol is normally characterised by higher levels in the morning. This is because cortisol is a hyperglycaemising hormone tending to increase glycaemia which would otherwise be too low after the lack of food at night. Yet, in these people the levels are particularly high and unfortunately cortisol increases glycaemia, turning the muscular proteins into glucose, thus having a catabolic effect on the muscle. In short, people who have a high cortisol level and practise aerobics in the morning on an empty stomach risk losing their muscle mass instead of burning fats. In this case, a meal based on proteins to be consumed before physical exercise may be useful to contrast catabolism, as well as the consumption of special integrators. However, it is better to practise aerobics when cortisol is lower, that is, after 4pm. Clearly, also in this case it is advisable non to have a meal based on carbohydrates before training… How can people find out if they are hyperadrenocortical? From a blood test measuring the cortisol level in the morning, or better still the level of cortisol in urine in the previous 24 hours. Even simple observations can help us, though. Cortisol is the stress hormone, so it is generally higher in people who are stressed (who is not, nowadays?), above all executives, entrepreneurs, people dealing with the public. There are also some constitutional morphologies more susceptible to stress: people who tend to accumulate fat in an android way, above all in the central part of the body, that is abdomen and lower back. On the contrary, those who accumulate fat in a gynoid way (in the lower part of the body) are more protected from stress. Anyway, reactions to physical exercise are often quite symptomatic. There are people who train in the morning and are full of energy for the whole day, while others feel exhausted for the rest of the day. The latter are probably hyperadrenocortical, so if they choose to practise physical exercise in the morning, their approach must be very soft and gradual.
We may go on and on talking about “when” to practise physical exercise, but due to space reasons I have to stop here. However, I want to answer a question I am often asked: “If I go to the gym and do weightlifting, is it better to practise aerobics before or after weightlifting?” If the aim is to lose weight, then it is definitely better to do aerobics after weightlifting. Since training with weights is an anaerobic activity, it mainly uses carbohydrates for energy purposes, thus causing a decrease in glycaemia as well as in muscular glycogen levels. So, it creates the best conditions to burn fats for energy purpose if followed by aerobics. Now that you know everything about aerobic training you do not have excuses… start training now!
