Fitness: how the individual is everything?

Although fundamental laws work the same for everyone (for example, calorie intake expenditure), the individual characteristics of each person also play a role.

What works and what doesn’t, research tells us. This is the best that science has, but it also shows the “average temperature in the hospital.” This may or may not apply to you. Research provides a base, important principles, and starting points. But the response to exercise and diet can be very different from one person to another.


  1. Your friend swears that high-intensity interval training is perfect for weight loss. He not only burns a lot of calories in training but throughout the day after it; he is alert, moves a lot, and burns a lot of calories outside the gym. After an exhausting morning workout, you want to lie down and fall asleep; you feel tired and overwhelmed all day.
  2. You are reading an article that deep squats are the only correct and most effective for muscle growth. But every time you try to sit down with a barbell “to the floor,” your lower back and knees start to hurt.
  3. A friend tells you not to do morning cardio – it makes her very hungry and interferes with dieting the day after training. On the contrary, you feel less hungry after cardio, and with its help, it is easier to stick to a diet during the day.
  4. In the gym, someone says that muscles only grow from base to failure and train each muscle weekly. You don’t see progress unless you train your muscles several times weekly in many exercises.

Who is right in each scenario? Probably everything.

For example, let’s take cardio, and only in the context of losing weight (we will not consider cardio’s benefits for health, endurance development, etc., for simplicity). Let’s say you want to add cardio to your weight loss program. In addition to spending calories directly in training, cardio can contribute to weight loss in another way:

  • It can affect the control of hunger and appetite, and through this – the amount is eaten after a workout during the day.
  • It can affect your activity level during the day – how exhausted and tired you feel or whether you feel energized and energized after a workout.
  • The quantity and quality of sleep.
  • For progress in strength training.
  • And even on willpower throughout the day.

Cardio and Appetite

In a study ( 2 ), scientists looked at calorie intake after an hour of slow cardio training. They wanted to know if the body compensates for the calories expended in training by increasing appetite during the day after it. If you spent 100 calories in training, would you not notice those 100 calories afterward?

The graph below shows how the situation varies from person to person (each box represents a different person).

The solid line is the complete absence of any calorie compensation.

The dotted line shows that people fully compensated for the calories burned during training (for example, they burned 100 calories and then also ate 100 calories more than normal).

Everything above the dotted line is already compensation “with a margin.” These people ate more than burned during the workout because their appetite soared after cardio.

As you can see, several people were left in a 300-600 calorie deficit post-workout. But several people not only nullified the “excess” food spent in training but also ate 300-600 calories in excess.


How does this apply to you?

Suppose you feel more hungry in the days after cardio and can not control yourself due to severe hunger. In that case, reducing the amount of cardio, intensity, or duration is probably better. If cardio reduces appetite, it will help create an additional calorie deficit and help lose weight.

Cardio and activity during the day

For weight loss, training in the gym is important and the daily activity level in general. A person spends an hour several times a week on training, so how much he moves outside the gym is no less important. How does cardio affect it?

The scientists followed 34 women who exercised for 13 weeks ( 4 ). Some women were active post-workout and expended many calories outside the gym. Others, on the contrary, compensated for the calories expended in training by reducing the activity level the day after. Probably, cardio made them so tired that they had no strength to maintain their usual active lifestyle. Or maybe they thought that since they worked out, they had the right to sit all day.

  • Blue color – group without reduction in calorie consumption
  • Red color – the group that showed a decrease in calorie expenditure during the day.

Some women became so sedentary for the rest of the day that they canceled all the calorie expenditure in training. The average calorie consumption per day was the same as if they weren’t exercising.

How does this apply to you?

If you’re feeling tired and overwhelmed after cardio, sitting or lying down a lot, and not moving much, it’s probably worth limiting your cardio to your diet. But if you feel more energetic and alert, this is an effective tool.

Cardio and sleep

Some people experience sleep problems due to exercise ( 6 ). The sleep-wake cycle and its disorders may also depend on genetic characteristics ( 7 ). Some people are more prone to exercise-induced sleep problems than others.


How does this apply to you?

If you notice that cardio interferes with sleep, you should reduce it. Lack of sleep harms not only health but also figure  ( 8 ).

Cardio and strength training progress

The dangers of cardio for muscle growth were first discussed in the 1980s. Since then, it has been proven that moderate cardio does not harm the muscles – up to a point, the increase in strength and endurance go together. But when cardio becomes too much (and for each person, this is a different amount), it will interfere with progress in strength.

How does this apply to you?

If you notice that cardio has a bad effect on your strength training, weights are falling; you do not have time to recover; you should reduce the intensity of your workouts or exercise less frequently. But cardio doesn’t affect strength training, and you enjoy doing it, no problem.

Cardio and willpower

It is believed that willpower is a limited resource that can be accumulated and expended. When faced with stressful tasks that require willpower, they may show less self-control later in the day.


How does this apply to you?

Let’s say you’re a morning person and you enjoy jogging in the morning. You have a good route, nice music, you like to sweat a lot, and you feel cheerful and energetic the whole day after that.

Or, let’s say you cringe every morning at the thought of exercising (by the way, it turns out that enjoyment of exercise may be determined by genetics  131415 ). For example, you have a hard time waking up earlier, you have to drive 40 minutes to the gym, and you hate driving during rush hour. Stubbornly following such a regime (“Turn on willpower or stay fat”) will drain self-control and cause you to put less willpower into the same day. This can lead to overeating, choosing more unhealthy and high-calorie foods, and sabotaging your attempts to lose weight. If the last scenario concerns you, you should give up morning cardio and not force yourself.

Strength training and muscle growth

This doesn’t just apply to cardio. In response to the same training program, different people will build different amounts of muscle. One study involved 53 previously untrained people. They did the leg extension in the seated machine for four sets of ten reps each, with a two-minute break between sets. The working weight on the simulator is 80% of the one-rep maximum. Training went on three times a week for nine weeks. The graph below shows the percentage change in the quadriceps cross-sectional area. Each column is a separate person.

The graph shows huge differences between people in response to the same training. While most people gained muscle, albeit, in varying degrees, five people lost muscle despite training.

It is also interesting that each person can be genetically predisposed to the growth of certain muscles. This means that some muscles can grow quite easily in response to any training, while other muscles refuse to grow even if a person puts in a lot of effort ( 16,  17 ).

In another study, participants trained for 21 weeks on a parallel development program for strength and endurance. Changes in strength also differed from one person to another. Moreover, despite the program’s strength training, some became weaker. And some with the same training increased strength by as much as 87%.


Thus, some people may get stronger and grow muscle faster than others ( 18 ). Interestingly, strong growth and muscle growth are not always directly related. A person can become stronger but gain more muscle according to the same program for another.

Recovery rate and genetics

Genetically, some people experience more muscle damage than others, so they need more recovery time ( 21 ). In addition, some people are much more susceptible to tendon and ligament injuries and need to be monitored for recovery ( 222324 ).

How does this apply to you?

Some people can do five failed sets of squats, deadlifts, and lunges and feel great the next day. At the same time, other unfortunates feel terrible for several days after the same workout. If you recover quickly, you can train with more volume and more often. If you haven’t had time to rest and recover from your scheduled workout, train less often/train with less volume/lower intensity/choose easier exercises.


Knowing exactly how you respond to changes in training and nutrition is important to achieve your goals. Research shows X is good doesn’t mean it’s good for you. Or just because the other person swears that Y works best and they know it from experience doesn’t mean Y is good for you.

The ideal weight loss program may include obligatory cardio, or it may not include it if you are sleepy and twice as hungry after a workout. The best strength training program for you may not include deadlifts/squats. May include training each muscle group 3 times a week – or may not.

There are many variables, and science is just beginning to study how people respond to them. The ability to build muscle, lose fat, and increase strength or endurance is also heavily influenced by genetics. So while research is useful and gives you a starting point, you’ll have to check for yourself and be attentive to what’s going on and how your body is reacting.


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