There is no right answer and everybody has their own interpretation of what a "Deep Tissue" massage is. I am going to explain what my understanding is of "Deep Tissue" massage and how I use it in my practice.
I read a great quote the other day, "Deep Tissue is a place, not a technique. There are many techniques in order to affect that place." Many people think a Deep Tissue massage is a different style, that it's painful and couldn't possibly be relaxing. This understanding comes from past experiences they may have had, that it is pressure/depth that "gets rid of knots" or breaks up scar tissue.
First things first. Deep is a location and shouldn't be used to describe pressure. Also, our sensory nerves are in our skin. When massaging, the hands on skin stimulates nerve endings which sends impulses to the brain. The brain processes the information and sends out impulses in response, creating the changes we experience in massage. Therefore, digging down into the muscles even though it can feel great and productive isn't always the best way to release tension and ease discomfort. To be honest, if you try pressing down on a piece of meat, you cannot reach much deeper than a couple of inches and that is without the layers of skin and fat on top. So this idea that driving an elbow into someones back is reaching the deeper layers of muscle doesn't make much sense. Another issue is that working too firmly or painfully can create or exacerbate a condition of the Nervous System called Central Sensitisation. The easiest way to describe Central Sensitisation is that, the more a painful stimulus is inflicted on the body, the more sensitive the nervous system can become to painful stimulation. This causes the pain threshold to lower. In my opinion, the reason people book in for a massage is to help and allow relaxation and ease tension, pain and discomfort. In this state of relaxation your Brain, Body and Muscles follow suit, allowing the Therapist to work easily around the body. When you fear or feel pain your body will tense, meaning the whole reason for you coming for a massage has just flown out the window and that cycle of Central Sensitisation increases. This is why I tell my clients that we work with a comfortable discomfort. I will only massage with a firm pressure up until the point I can feel the muscles begin to contract and tense up. This is a sign to me that the Nervous System has reached its pain threshold and we have passed the stage of comfortable discomfort.
Now don't get me wrong, I am not saying a massage can't or shouldn't be firm. Everyone has a different different level of pressure that they find relaxing and comforting.
The reason I advertise my massages as different styles; De-Stress and Deep Tissue, is only because these are recognisable types of massage. However once my client is on the couch I work specifically to what their body needs. Whether it's a light, medium or firm (not deep) massage or whether they have come for relaxation purposes or to target specific areas or injuries. I use and adjust the same techniques to provide the right massage for each individual. I hope to educate my clients that a "Deep Tissue" is no different to a De-stress massage. A Sports Massage does not mean you get beaten up and leave covered in bruises and a De-stress massage is not an "only for the wimps" massage. We leave our egos at the door and concentrate on the main purpose of a massage. A relaxed mind, a relaxed body and to feel tension and pain free.