When clients say "I feel tight," they can mean a few different things. In practice, "tight" usually boils down to three main properties (there are more, but for the purposes of this article, we'll stick to these):
- Range of motion – how far a joint can move.
- Tension (mechanical resistance to movement) – how much the tissue pushes back when you try to move or press into it.
- Soreness or sensitivity – how tender a spot feels to pressure.
These properties can move together or not. Someone can have okay range of motion but high tension, or very little soreness but a lot of resistance when you try to move the tissue. There isn't one single "tightness." That's why measuring the right thing matters.
In this article, I'll go over what each of these properties in detail and what exactly MuscleMap measures or not.
How Massage Affects the Different Properties
Range of Motion (how far it moves)
Massage can improve range of motion, but not as you might think by physically stretching muscle fibers like taffy. The bigger driver is the nervous system. After a massage, the brain often feels safer at the end of a joint's range, so it "permits" more movement. Researchers call this increased stretch tolerance.
There can also be small physical contributions: massage improves local blood flow, warms tissue, and reduces protective reflexes that normally resist stretch. Together, these make muscles feel more supple and joints move more freely.
So the short answer is: massage changes both the brain's perception (less guarding, more tolerance) and the local tissue state (warmer, better circulation, reduced reflex resistance). That's why movement often feels easier right after a session.
What to tell clients: "Massages don't physically lengthen your muscle fibers in ten minutes, but it can help your nervous system relax and your tissues become more pliable. That combination is why motion feels easier."
Where MuscleMap fits: It doesn't measure ROM directly, but if ROM improves because resistance dropped, you may see that reflected as lower measured tension.
Tension (mechanical resistance to movement)
This is what MuscleMap measures.
In a lab study using ultrasound elastography: "massage reduces muscle stiffness"—but the effect was short-lived after a single seven-minute session.
In a five-week randomized trial: repeated massage kept stiffness lower in the upper trapezius for at least three weeks.
What this means for practice:
- Single sessions drop stiffness briefly.
- A series of sessions can create longer-lasting changes.
Where MuscleMap fits: It shows before/after numbers for tension and helps track whether those changes carry over between sessions.
Soreness or Sensitivity (pressure pain threshold)
When clients say a spot feels "sore," they're describing sensitivity to pressure. This is not the same as mechanical tightness or shortening.
Researchers measure this with the pressure pain threshold—how much pressure it takes before a spot feels painful. After massage, this threshold usually goes up, meaning the tissue tolerates more pressure and feels less sore (Aboodarda et al., 2015; Furlan et al., 2024).
Where soreness comes from:
Nervous system side: Stress, fatigue, or fear can make the system more reactive, so light pressure feels painful. Relaxation, trust, and calming touch can turn the volume down.
Physical tissue side: Locally, sore areas often have reduced blood flow, low oxygen, and a buildup of chemicals (Shah et al., 2008). These chemicals sensitize nerve endings, so pressing hurts more than in healthy tissue.
So soreness is both a brain process and a tissue process. The tissue environment becomes chemically sensitive, and the nervous system decides how "loud" that sensitivity feels.
Do sore muscles actually have more stiffness? Not always. Studies show stiffness (resistance) and soreness (sensitivity) are related but separate. For example:
- Range of motion can improve without big changes in stiffness (Konrad & Tilp, 2014).
- Massage can reduce soreness (higher pressure pain threshold) even if stiffness doesn't change much (Eriksson Crommert et al., 2015).
In practice: A sore muscle doesn't always mean a stiff muscle.
What to tell clients: "Soreness doesn't always mean the muscle is tighter. It means the nerves in that area are more sensitive right now. Massage can calm the chemistry and reassure your nervous system, so the spot feels less tender."
Then, What Are "Knots"?
When clients say they have a "knot," they're usually describing a myofascial trigger point: a small, localized area of muscle that feels denser or rope-like.
Physically: A 'knot' is best thought of as a taut band with a hypersensitive spot.
Why it's sore: That contraction develops a chemical environment that sensitizes local nerves (Shah et al., 2008).
Why the brain matters: Repeated signals from that spot can also sensitize the nervous system, sometimes even referring pain elsewhere (Simons et al., 1999).
In our three-property model, a knot usually lights up two properties:
- Tension – because fibers are contracted.
- Soreness – because the area is chemically and neurologically sensitized.
It usually doesn't directly block ROM, unless multiple knots build up resistance across a whole muscle.
What to tell clients: "A knot is a small patch of muscle that's both tighter and more sensitive than the rest. Massage helps by improving blood flow, calming the chemistry, and reassuring the nervous system."
When "Tight" Isn't Actually Tight
Clients often describe a muscle as "tight," but that feeling doesn't always match what's happening in the tissue.
Research shows there are different contributors to the "tight" sensation:
- Mechanical stiffness (tension): how much the tissue resists movement.
- Range of motion: how safe the nervous system feels at the end of a stretch.
- Soreness/sensitivity: how reactive the nerves in the area are.
Here's the key point: a muscle can feel tight even when it isn't objectively stiffer. For example, hamstrings often feel "like a rope" after a run, but stiffness tests may show no big difference from the other leg. The nervous system may simply be more protective, or the tissue is more sensitive.
Citations
- ROM & training vs stretching – Afonso et al. (2021). Strength Training vs Stretching for Increasing Range of Motion: A Systematic Review and Meta-Analysis.
https://www.mdpi.com/2227-9032/9/4/427 - Massage reduces soreness (pressure pain threshold) – Aboodarda et al. (2015). Effect of Massage on Pressure Pain Threshold of Exercise-Induced Muscle Soreness.
https://doi.org/10.1186/s12891-015-0729-5 - Strength & ROM adaptation study – Konrad & Tilp (2014). Effect of Stretching Training on Muscle–Tendon Properties and Muscle Strength.
https://doi.org/10.1519/JSC.0000000000004721 - Biochemical environment of trigger points – Shah et al. (2008). Biochemicals Associated with Pain and Inflammation in Myofascial Trigger Points.
https://doi.org/10.1016/j.apmr.2007.10.018 - Massage reduces stiffness (short-term, ultrasound elastography) – Eriksson Crommert et al. (2015). Massage Induces an Immediate, Albeit Short-Term, Reduction in Muscle Stiffness.
https://pubmed.ncbi.nlm.nih.gov/24856792/ - Massage vs. stretching effects on stiffness – Eriksson Crommert et al. (2015). Short-term effects of massage and stretching on muscle stiffness.
https://pubmed.ncbi.nlm.nih.gov/25487283/ - Systematic review of massage and pain outcomes – Furlan et al. (2024). Massage Therapy for Pain: An Updated Systematic Review and Meta-Analysis.
https://pubmed.ncbi.nlm.nih.gov/39256711/ - Trigger point pain referral and sensitization – Simons et al. (1999). Clinical and Etiological Implications of Myofascial Trigger Points.
https://pubmed.ncbi.nlm.nih.gov/18164347/