Table 2. Quotes illustrating factors contributing to (not) engagement in PA among adolescents.

Themes/Subthemes	Quotes
Myself as a source/ Health benefits
The positive effect of sports on physical health motivates	“… I started training about a month and a half ago, and I have to say that I see results in terms of fitness. I just actually see that I can handle it more and more… I do not know, but I feel good after training… I am more tired and even better to go to bed sooner…”
The positive effect of sports on mental health motivates	“… but it also has a positive effect on me in terms of my mentality or something… I have to say those pressures and everything are somewhat distracting, when there is stress from school. I do not think about it when I exercise, for example… in my opinion, I would recommend it to those who are prone to those depressions and so that something to distract.”
Myself as a source/ How do we experience PA
Success motivates	“So, what I think motivates people to play sports is definitely the success. Because when people see that they are doing well, they just go up and try to reach their greatest peak…”
Failures demotivate	“… that many times, when someone was not good in PA since childhood and I was exactly like that… When I came to school, I was clumsy in football. You cannot even look on it. Once, I pushed the ball and almost broke the window. So not many people chose me for the team…”
Myself as a source/ Need to know how
They do not know how much and how to exercise	“… for example, someone does an activity, they need to know how to do it properly. Even when you exercise, it may hurt you.…I do not know for sure, but maybe the training was not as effective as it could be.”
To be able to try different physical activities	“… in order to find some sports that you will really enjoy, you will need a help to show you what those sports are like; or let you look more and find it by yourself, what you like best and then you would actually go into the fact that ‘I like this, I will play this‘, or just like that.”
Myself as a source/ Body decides
Physical predisposition, physical skills and fitness help	“Well, I think it could also be that someone is built for sports. Because, for example, my friend is not just a person who was built for sports. He does not do very well on the physical education, or anything like that, so when he is free, he does not just go out and play sports…”
Health problems as a PA barrier	“… medical condition, so my classmate actually had to finish ballet because she has such an illness as asthma and her trainer said she had to quit. The doctor told her the same and she is already quite demotivated. That she just misses ballet, the dancing.”
Myself as a source/ Resources in us
Laziness	“I think laziness plays a big role in that, because I have a lot of people like peers who are extremely lazy and just cannot get into things like that (*PA). They will say, ‘Well, I had rather play on PlayStation some video games’.”
To show determination	“So, it is basically about trying to get over ourselves and trying to do things that do not always suit us. Do not go into your comfort zone, but go out of it by doing things differently.”
How PA can be done/ PA at school
Physical education in schools as a duty and boredom, not joy	“… or still do it so that the exercise is not actually a punishment or an enemy, but that we actually take it gladly.”
Teacher as a facilitator	“Yeah, well, our gym teacher told us, ‘I live in Myslava [place near Kosice]. I go jogging every morning. You can join whoever wants‘.”
How PA can be done / PA at other occasions
Personality, experience and attitude of the coach	“Or even if we are already at that training, you can just sit down with your coach once in a while and ask him ‘What I should improve?‘ or, What I cannot do?‘, and then he can also tell us simply what is good and what is bad for us.”
When PA is fun	“I perceive the sport as fun. I enjoy it. I can go out with friends…and of course, I feel better when I exercise.”
Others as a source/ My friends
I am going where my friends are	“So, I think it can also be the team, because, for example, I personally just do not go cycling alone, because I do not like it, but if I am going with someone, I am out for 3–4 hours…”
The influence of the collective	“So first of all, it is a team, one hundred percent true. Because when I found good friends in the team, I really do not want to leave this team…”
Others as a source/ My family
If someone does not play sports as a child, it will be difficult later	“As I think, when person did not play sports as a child, so when he is older, it is getting harder for him, as when he did sports since childhood…”
My family supports me in PA	“Or maybe family and neighbourhood support. Because when they do not support person, he does it unnecessarily. That no one believes in him and he is just alone in it…”
Others as a source/ What others do?
The new generation is more passive and more striving for comfort	“…overall, young people move less, because it does not matter if we are at school or at home, we are still sitting. We are sitting on a chair either behind the desks or at the computer. Some may have around 14 hours per day and they spend most of that time either on a chair or when they are going by bus or whatever, so that their body may not be used to it (*PA)… they do not have to deal with it much.”
Among the surroundings there are very few who do PA every day	“So, in my opinion, they probably did not give true information. Because just from the way I notice my surroundings, I probably do not know any young person who would train or have any PA 6–7 times per week.”
Factors outside/ School duties first
To fulfil school duties in the first place	“… Because when we study in person, we need to go to school. I leave in the morning and come back in the afternoon, yeah, around 16:00. So, there is really little time space that I can find for some sport activities. So I come back home, eat something or whatever, and I start to do things for school. It takes a long time, yeah, because there is a lot of learning, writing, tests and whatever. So, in the evening, when I am done all my stuff, maybe it could be around 21:00, but I am really going to say that I do not want to do anything, because I am tired.”
Fatigue from school	“It may still be that person is stressed out. So, he actually does not do as well as he should and he is stressed out of school, for example. So, he just does not have the motivation to train…”
Factors outside/ We are more online
Videos, groups and posts on the internet are motivating	“So, if the person is a positive influencer, such as Attila Végh [Slovak athlete], which actually presents himself on these social networks as a person, not only as an athlete, but also presents his life and his family… It is not just that he brags about what he won and his achievements, and also those athletes who help some sick children, so that is actually the positive role model, is not it?”
Everyone is online	“It can be said, that when everyone is on the computer, this social contact is maintained through the computer. So this is how they satisfy this social need through their own "Discord" and other things that they can talk with whole internet community.”
Factors outside/ We have a place for PA
PA-promoting environment	“So, in my opinion, our environment is also affects it (*PA). For example, if I live far from something (*sport clubs), I just prefer to watch the series at home myself…”
Available sports clubs	“Well, it may also be that some sports are too expensive and someone cannot attend them, or rather the approach to those sports. For example, if I want to attend a sport, I have to go through the whole city because there is simply nothing in my area. Or in schools, there are just a few such sports clubs…”
Factors outside/ Inspire for PA
Famous person as a role model	“… if we have a role model in someone, that one day we would like to be like him/her, we go for it, and when the others do not really have anyone like that, nothing motivates them to be better.”
Sports campaigns as a means of PA support	“In my opinion, it is important to make more promotion among the students, and support those sports in general. Now there is one such project… where the sport is actually made in more attractive way with the help of those influencers, as Nina [Slovak name] said.”