Carried from the fitness industry: "no pain no gain" has been applied in the massage therapy industry for decades.
Indeed clients have been used to suffer in silence or at least have in their mind if they are going through aches and pains to have them addressed they need to go through some additional pain.
Which I believe discourage some people to seek from bodywork.
With this "no pain no gain" approach: leads to therapist who still work this way even though this was a way to work maybe 50 years ago but we now know that working on pain free threshold will create a greater soft tissue release because we will gain the trust from the client, as more relaxed, tissue will be more challenged for the best.
However, some clients are now used to this "no pain no gain" and believe that if they don't experience any pain then, it doesn't do anything, but when pain is experienced the body response is to protect itself by tensing and contracting muscle which is pushing away the therapist pressure so if we follow the "no pain no gain" we then should apply more pressure which causes more pain with more resistance from the body which is a vicious circle.
This is why instead of working against a body, it is important to work in a pain-free threshold to avoid that physiological reaction and keep doing what we are doing with a tissue relax.
Obviously, when we say pain free threshold, there will be some discomfort but there is a difference between it's uncomfortable and it's painful, indeed sometimes it can even be uncomfortable and it can feel good at the same time which is "bizarre" to experience but called therapeutic discomfort, the kind of discomfort that the nervous system likes.
So we need to break down the idea of being in pain during a massage is normal, when pain is experience we to be away from it so sometimes clients who won't say anything may show "nonverbal communication" : faces gesture, facial expression showing the discomfort, moving leg or taping on the table which needs to be taken into account and they are not always aware of doing it, which clearly show the intensity of the technique or treatment/massage.
As an example during one of my experience with sport team, we were 5 or 6 therapists providing sport massage to help athletes recovery post-match, one the therapist beside me was going so hard on his athletes that during the whole 30 min she was taping on the table trying to take it, trying to resist, saying I have so many knots that need to be worked out. It was hard to listen to her taping for 30 min and when we think about it taping is like a sign of surrender.
It is okay to experience some discomfort during a deep tissue massage, sports massage or bodywork, it should be bearable, monitored but not painful.