Your ability to judge when to relax your body and when to lock it tight in maximal tension is a critical factor in your development in the sport. Tension in the body is absolutely necessary WHENEVER YOU ARE TRYING TO INHIBIT THE MOVEMENT OF YOUR OPPONENT. In most other cases it is undesirable, as it costs you greatly in endurance and efficiency of movement. The clearest examples of a time when you want to shut down your opponent’s movement is during the application of a submission hold - so unsurprisingly, this is a time when there ought to be considerable tension locking your body into the hold until the application is complete. This explains why failed submissions, particularly in long combinations, are among the most tiring aspects of a match. Learning to keep your body relaxed when you want to generate movement, and then switch to maximal tension when you want to lock the opponent down and complete a given move is a big part of your shift from beginner to expert. Jiu jitsu is a typically played out as long cycles of relatively relaxed periods interspersed with short bursts of maximum tension as critical moves are attempted. Just make sure those periods of great tension are kept short and spaced apart or you will quickly exhaust yourself. The most dangerous part of maximal tension is the natural habit most people have of HOLDING THEIR BREATH UNDER TENSION - be very careful - once you go into oxygen debt it is very hard to get out of debt under the stress of a tough match. Monitor your breathing careful and keep breathing even when your body is fully locked in a deep submission hold. Here, Georges St-Pierre shows an excellent degree of body tension as he locks in a tight inside heel hook in an inside sankaku variation of cross ashi garami. Notice that although his BODY is exhibiting strong tension, his FACE is not - this is usually a good sign that breathing is uninterrupted and that the tension is being applied in the correct places.