adjust holding breath rules

charts.tex

@@ -247,7 +247,7 @@
 
     Fighting & Each round inflicts 1 \gls{fatigue}. \\
 
-    Holding Breath & 1 \gls{fatigue} per round. \\
+    Holding Breath & 1 \gls{fatigue} per negative \glspl{ap}. \\
 
     Marching & 1 \gls{fatigue} per mile. \index{Marching}\\
 

combat.tex

@@ -706,6 +706,11 @@ However, they can get up as by spending 1 \gls{ap}.
 
 Gaining the higher ground grants +1 to the Attack Bonus, as you target the enemy's head easier and gravity aids your downward swings.
 
+\subsubsection[Holding Breath: 1 \glsentrytext{fatigue} per negative \glsentrytext{ap} at the end of the round]{Holding Breath}
+
+Anyone holding their breath takes a number of \glspl{fatigue} equal to their negative \glspl{ap} at the end of the round.
+So someone ending a round on -3 \glspl{ap} would take 3 \glspl{fatigue}.
+
 \subsection{Manoeuvres}
 
 These additional actions cover different ways to engage with enemies.