Training in autumn without getting sick: how to look after your defenses when the load goes up

Moderate, consistent exercise protects against respiratory infections. What leaves the body most exposed is piling up training load without sleeping, eating or recovering enough. In autumn, with fewer daylight hours and more viruses in circulation, looking after your defenses starts with adjusting those three factors.

October brings together marathon plans, the return to the gym and the first colds of the season. It is also the time when more people become interested in food supplements aimed at the immune system, and it makes sense to ask what role they really play. Here I explain what the evidence says, which habits matter most and how to read the label on one of these products without being swayed by the box.

What training does to the immune system

The relationship between exercise and infections is usually drawn as a J-shaped curve. A person who doesn’t move has an average risk, someone who trains regularly at moderate intensity lowers it, and someone who stacks very high loads sees it rise again. The model was proposed by physiologist David Nieman in the nineties and remains a good starting point.

For years there was also talk of an “open window”: a few hours after intense effort during which the body would be left unprotected. That idea has lost strength. A review published in 2018 in Frontiers in Immunology argues that the drop in immune cells in the blood after training reflects their movement into other tissues, not a real decline in protection.

So why do so many runners get sick in race week? Because around a load peak other factors usually coincide: sleep gets worse, there is travel, people eat less than they burn and share space with thousands of others. Hard training rarely acts alone.

What matters most: sleep, energy and load

Before looking at any jar or vial, review these three areas. They move the needle most and are the ones most neglected when the plan gets demanding.

Sleeping more than seven hours

In a study published in the journal Sleep in 2015, 164 healthy volunteers were given a rhinovirus through the nose after a week with their sleep measured by actigraphy. Those who slept less than six hours were more than four times as likely to end up with a cold as those who slept over seven. If you get up early to train at the cost of cutting sleep, you are paying for the session with your defenses.

Eating what you burn

Training hard in an energy deficit is one of the combinations the immune system tolerates worst. In sessions longer than 90 minutes, taking in 30 to 60 grams of carbohydrate per hour helps contain the rise in stress hormones. Autumn is not a good time for aggressive diets either if you are preparing for an event.

Spreading the load

Two hard days in a row cost more than the same two days separated by an easy one. Increase weekly volume gradually, take at least one real rest day and cut back 20–30% every three or four weeks.

Alongside this, small habits help: wash your hands when you leave the gym, don’t share your water bottle and take off wet clothes as soon as you finish.

What supplements can and cannot contribute

A supplement fills gaps, but it does not make up for five hours of sleep or a badly planned week. That said, some nutrients have a recognised role in immunity, and in the European Union that recognition is regulated.

Only a few substances may state on their label that they contribute to the normal function of the immune system: vitamins A, B6, B12, C and D, folate, and the minerals zinc, selenium, iron and copper. Any other ingredient may accompany the formula, but it cannot be credited with that effect.

For people who train, vitamin C has its own nuance. European regulation recognises that an additional 200 mg per day contributes to maintaining immune function during and after intense physical exercise. This is in line with a 2013 Cochrane review: in the general population it did not reduce the number of colds, but in marathon runners, skiers and military personnel under extreme exertion the risk was halved.

Vitamin D deserves separate attention between October and March, when synthesis from sun exposure drops. If you always train indoors or at night, discuss it with your doctor before supplementing on your own.

How to read the label: a practical example

To bring all this down to earth, it helps to look at a specific supplement for the defenses. Propolvit Defens is a formula from MARNYS, the Cartagena laboratory that has been manufacturing since 1968 and now distributes more than 400 products in over 60 countries. It comes in 10 ml drinkable vials, and the recommended dose is one a day before breakfast.

Ingredient	Amount per vial
Royal jelly	1,000 mg
Colostrum	1,000 mg
Shiitake concentrate (organic)	250 mg
Reishi concentrate (organic)	250 mg
Purified propolis	40 mg (equivalent to 100 mg of raw propolis)
Vitamin B6	1.4 mg (100% of the reference value)

Reading it is straightforward if you apply the above. Vitamin B6 is the ingredient that supports the official claim: it contributes to the normal function of the immune system, to energy metabolism and to reducing tiredness and fatigue. Royal jelly, propolis, colostrum and mushrooms are ingredients with a long tradition of use that complete the formula.

The format makes sense for someone who trains early. A single-dose vial fits in a backpack, needs no water and takes seconds before leaving the house. The brand suggests it for seasonal changes and recommends assessing results after a quarter.

Read the fine print too. It is a product for adults, not indicated during pregnancy or breastfeeding, and it contains colostrum, which is a milk derivative: it is not suitable for vegans or for people with lactose intolerance. It contains no gluten. If you are allergic to hive products or fungi, or are on immunosuppressive treatment, consult a professional first.

When to stop: the neck rule

Not even the best plan prevents every cold, so it is worth being clear about what to do when one arrives. The most widely used rule in sports medicine divides symptoms by where they appear.

• Above the neck (congestion, sneezing, slightly sore throat): you can train gently. A short easy run, no sets or heavy weights, and go home if you feel worse after ten minutes.
• Below the neck (fever, generalised muscle aches, chest cough, digestive discomfort): complete rest. With fever, never train.

Return is done in steps. Wait until you have gone a full day without symptoms, resume with gentle sessions and expect to need two or three days of readjustment for every day you were off. Losing a week of training hurts less than dragging a virus around for a month.

Frequently asked questions

Does training lower the defenses?

Not in general. Moderate, regular exercise is associated with fewer respiratory infections than a sedentary lifestyle. The risk rises when very high loads coincide with little sleep, energy deficit, stress or travel.

How many hours should an athlete sleep during a heavy training period?

At least seven hours, and ideally closer to eight or nine in weeks of higher volume. Sleeping less than six hours more than quadruples the probability of catching a cold after exposure to a virus.

Can I train while I have a cold?

If the symptoms stay above the neck, you can do a short, gentle session. With fever, generalised muscle aches or chest cough, it is time to rest until they clear.

When does it make sense to start a supplement for the immune system?

The usual approach is to start at the beginning of autumn or a few weeks before a demanding block, and to keep it up continuously. It supports a varied diet and sufficient rest, and never replaces them.

Healthy Living