The not-so-gentle art: Jiu jitsu, like all combat sports, aspires towards maximum efficiency in physical output. It strives to use the least amount of to get the job done. This is often misconstrued to mean that everything should appear effortless and flowing in execution. It is certainly true that for the majority of any given match your body ought to be fairly relaxed and loose to allow efficient movement, but there are definitely times when you want to exert near maximal contraction and for short bursts. THIS is part of the pathway to true efficiency. If you are too relaxed when applying a submission hold and the opponent escapes – then you have to start all over again – necessitating the repeated expenditure of a large amount of energy and potential risk of losing. There is nothing efficient about that. True efficiency is being relaxed when appropriate (usually the majority of the match) but also tight when appropriate (usually for short when scoring or finishing). This way you don’t waste getting to a scoring or finishing situation and fail due to lack of tight connection/power and then have to repeat yourself all over again. One burst of near maximal energy output that ends a match is not as fatiguing as twenty minutes of relaxed sparring that requires you to keep going and going due to repeatedly failing to or finish because you were too loose at the critical moment. So yes, stay relaxed most of the time – but when it’s to go – GO