The poll sits just behind the ears where the headpiece rests, with the jaw hinge and upper cervical joints directly beneath. Thin covering means light reaches the area quickly.

• Bridle and headpiece pressure
• Tension through the jaw hinge
• Resistance to flexing at the poll

Fit over a clean, dry poll with the bridle off, so the cap sits flat against the crest.

The face, jawline and muzzle. Skin is thin and vasculature superficial here, so this is one of the few areas a handheld device can cover in a couple of minutes.

• Facial muscle tension
• Sensitivity along the jawline
• Head-shy behaviour when handled

Never aim directly at the eyes — work from the side and keep the beam moving.

The C1-C7 cervical spine and the muscle running either side of the crest. This is the segment doing the work in every bend, flexion and downward stretch.

• Stiffness through one side of the crest
• Uneven bend left versus right
• Restricted downward stretch

Work in three passes along both sides of the crest — upper, middle, lower.

The withers and the shoulder blade beneath them — the first place saddle pressure concentrates, and the pivot for every stride of the front limb.

• Pressure marks under the front of the saddle
• Shortened front-limb stride
• Muscle tension behind the withers

A full blanket covers withers and shoulder in one pass; spot-treating tends to miss the lower edge of the shoulder blade.

The thoracic spine, ribcage and the full saddle-bearing surface. The largest single area on the horse, and the one most often treated as a whole after work.

• Reluctance to lift through the back
• Pressure points along the saddle panel
• Sensitivity over the ribs

Girth the pad just firmly enough to sit flat — compression is not what does the work here.

The lumbar span behind the saddle and the croup above the sacroiliac joint — where the push from the hindquarters is transferred into the spine.

• Tension across the loin
• Asymmetry through the croup
• Reduced engagement behind the saddle

Position the pad's rear edge behind the last rib, otherwise the loin is not actually covered.

Gluteals, hamstring group and the deep muscle over the hip. The thickest muscle mass on the horse, and the source of forward power.

• Loss of drive from behind
• Shortened stride on one hind
• Tightness over the hip

Deep muscle here — 850nm near-infrared reaches further than 660nm. Typically used after work rather than before.

Knees and hocks, cannon bones, fetlocks, flexor tendons and suspensory ligaments. The hock is hind-limb only — the front limb's equivalent joint is the knee, and the two behave quite differently.

• Filled tendon sheaths
• Warm or puffy fetlocks
• Stocking up after transport

Snug but never tight. Boots run on both fronts or both hinds together; the wrap suits a single hock or knee.

Hoof wall, coronary band, frog and sole. The coronary band is where new horn originates, so it is the ring most worth covering.

• Coronary band sensitivity
• Slow hoof wall growth
• Discomfort after shoeing

Pick out the sole first so the boot seats properly and the light sits close to the coronary band.