There is a lot of hair to dig under, but a journey to the centre of Liam Coltman would reveal a core that is solid, durable and unlikely to melt even if a blowtorch is applied.
It's an assessment that can be made quickly and easily given his reaction to the installation of a new conditioning coach for the Highlanders' forwards during the pre-season. One Bradley Carnegie Thorn decided over the summer he'd like to take responsibility for getting the tight five fit and ready for the season.
Thorn is notorious: the veteran former All Black pushes himself harder than most - which is why at almost 39 he's still in this business. The Franks boys - Owen and Ben - used to have a bit of an exclusive training club with Thorn when they were Crusaders and All Blacks together. Hard-men-only kind of thing, with the rest of the forwards making their excuses.
They all knew the intensity would be extreme and their bodies pushed to, and probably beyond, their limits.
It says plenty for the mindset and ambition of 24-year-old Coltman that he's relished the input of Thorn.