PHT 5216: Unit 2 — Thermotherapy (Superficial Heat)

1) What thermotherapy is (and isn’t)

Goal: Heat superficial tissues to increase tissue extensibility and reduce pain; may trigger reflex heating of deeper structures.

Not ideal for deep targets (e.g., deep muscle belly/joint capsule): consider other heating modalities if the primary goal is true deep heating.

2) Clinical forms you should know

Moist hot packs (MHP) — primary focus of this unit

Paraffin bath

Fluidotherapy (dry heat via convection)

Others: electric heating pads, air-activated wearables (superficial)

3) Biophysical dose: what determines the effect?

Target temperature rise: 104–113°F (vigorous heating range). Above this → burn risk.

Rate of heating: Faster ↑ effect but may ↑ pain if heat can’t dissipate.

Tissue volume heated: Larger areas (e.g., hot tub/jacuzzi) → systemic responses (↑ BP/HR, possible pulmonary effects).

Tissue composition & dissipation: Highly perfused tissues change more; impaired sweat/pain sensation (e.g., C5 incomplete SCI) = burn risk.

4) Physiological effects you can bank on

Vascular

Cutaneous vasodilation (especially with moist heat)

↑ Capillary permeability → fluid shift; can mimic mild inflammatory response

Neuromuscular & Pain

Pain ↓ via thermal Gate Control (thermoreceptors inhibit nociception in dorsal horn)

NCV changes (sensory conduction altered locally and possibly distally via consensual heating)

Muscle spindle/GTO: ↓ Type II spindle afferent firing; ↑ Ib (GTO) firing → ↓ α-motor neuron activity (indirectly via ↓ γ-drive; superficial heat doesn’t penetrate to directly change α)

Connective Tissue

↑ Elasticity, ↓ Viscosity, ↓ Joint stiffness, ↑ Muscle flexibility (think better stretch tolerance post-heat)

5) Heat transfer mechanisms (match to modalities)

Conduction: direct contact → MHP, paraffin

Convection: moving medium → fluidotherapy

Radiation: EM waves (covered conceptually here)

6) Moist Hot Pack (MHP): parameters & safety (high-yield)

Storage temp (hydrocollator): 158–167°F (info sheet often lists 150–170°F)

Layering: 6–8 towel layers (MHP cover = 2 layers → add ≥4 towels); 8–10 layers if supine on the pack

Treatment time: 15–30 min (check at ~5 min); first treatment often 10–15 min

Risk: One of PT’s #1 liability modalities → educate patients not to remove layers “because they don’t feel it” (sensory adaptation happens)

7) Indications (when heat helps)

Main indication: Increase superficial tissue extensibility to aid stretching/manual therapy

Pain modulation (subacute/chronic), muscle guarding, stiffness reduction, improving stretch tolerance prior to mobility work

8) Contraindications (don’t heat these)

Impaired hot/cold sensation

Severe vascular insufficiency / compromised circulation

Recent burns; infection/open wounds

Malignancy (skin/lymphatic)

Acute injury/inflammation (can increase swelling)

Decreased cognition impacting safety

Excessive HTN (resting >160/90)

Long-term steroid therapy (thin skin → burn risk)

Others commonly listed: hemophilia, severe CV/respiratory disease

9) Heat vs. Cold: quick compare for plan-of-care decisions

Both can ↓ pain.

Cold helps limit swelling/hemorrhage acutely; Heat can increase swelling if used too early.

Choose based on healing stage, tissue goals (extensibility vs edema control), and patient factors (sensation, perfusion, BP).

10) Practical checklist (what to do every time)

Screen for contraindications/precautions (sensation, circulation, cognition, BP).

Explain purpose, expected sensations, risks; obtain consent.

Set dose: correct layers, positioning, timer; re-check at ~5 min.

Monitor skin & symptoms; document parameters and response.

11) Sample documentation line (plug-and-play)

MHP to L lumbar paraspinals, prone with pillow under abdomen; 8 towel layers; 20 min; skin intact pre/post; pt reports “pleasant warmth,” pain 6/10 → 3/10, improved forward flexion by 15°; education on home heat safety provided.

12) Safety pearls (boards & clinic)

Large-area heating (hot tubs/jacuzzi) may cause systemic responses — avoid in pregnancy.

Patients with impaired sweating or pain perception (e.g., C5 incomplete SCI) are high burn risk.

When in doubt, add layers, shorten time, and re-check early.