The idea is joint-centred, with the aim being usable range; aka movement you can actively control, not just passive flexibility. Tissue adapts to the demands placed on it, so you load joints through their full range, then build strength at the end of that range.
The main tools are:
CARs (Controlled Articular Rotations): slow, maximal, active circles of a joint at the edge of its range, with tension elsewhere in the body. They work as a daily joint check and maintenance routine.
PAILs/RAILs (Progressive/Regressive Angular Isometric Loading): isometric contractions at end range, used to simultaneously expand flexibility and strengthen newly acquired ranges.
End-range strengthening: protocols like Passive Range Holds that build strength and control in the newly gained range so it sticks.
What it adds to the plan:
The plan's lifts mostly work in mid-range. Jiu-jitsu takes hips, shoulders, spine, neck, and wrists to the ends of range under load, from awkward angles. FRC gives you a systematic way to find the limited joint, expand its range, and then own it. Where FMS shows that a pattern is limited, FRC helps work out whether the cause is a joint range limit or a control problem.
Practical example:
Before training, spend five minutes on CARs: shoulders, thoracic spine, hips, and wrists. Say your hip CAR shows a ragged, restricted arc on internal rotation, and it matches an FMS squat limitation. On a tonic day, you add a short PAILs/RAILs block for that hip, then finish with a slow, loaded lateral lunge that uses the new range. For a guard player, this is more directly useful than another set of heavy squats.
A note on safety and limits:
Skip end-range loading around painful or recently injured joints, and ideally learn the technique from a qualified practitioner. The evidence base for FRC is thinner and more practitioner-driven than for conventional strength training, so take its larger claims accordingly.