No man is willing to waste his strength for the mere pleasure of wasting it.
It is interesting to note that, among the six hundred pages that make up the Economic Harmonies, Frédéric Bastiat dedicates only two dozens of them to a chapter titled Capital (to be compared to the brick that would be written fifteen years later by Karl Marx under the same title). It may well be because the concept is, all in all, fairly simple and should not really be a controversial topic (which, unfortunately, does not mean there are no misunderstandings around, obviously)
In order to introduce the concept in a simplified way and analyse straightly some of its attributes, the introduction to the chapter places us in presence of Robinson Crusoe because “Economic laws act in accordance with the same principle, whether they apply to great masses of men, to two individuals, or even to a single individual”. One could think that today’s quote that was valid in 1850 is not anymore in an era when sports are widely practised but, under intense scrutiny, it well seems that people often do sports for something else than merely wasting their strength, generally thinking it has something to do with staying healthy (triathlon seems to be the mysterious exception here). That said, I believe it is still valid and the choice of introducing capital as a means to reduce the effort required to obtain satisfaction appears fully relevant to me.
This is the premise that will help and understand that fixed capital formation is beneficial to all, viz. the owners of said capital (the capitalists), the users of said capital (the workers) and the consumers of products made with the help of the said capital.