Side plank hold. There are many challenging body weight exercises that strengthen your core and your stabilizers which are essential if you are a BJJ athlete
What a lot of people don't know is that weight training as we know it came about from the body building industry where dudes who would toss around big chunks of metal in the form of bars or dumbbells in an effort to get huge. Going to the gym and doing our 8-12 reps with some rest and then doing it all again 3 times through before we move to the next station is considered normal for strength training but it is actually stock standard hypertrophy training and ideal for body builders, not necessarily for a performance athlete.
Body building training is fine... if you want to be a body builder, or if you want to have great pecs for the beach (for the dudes) or if you want a perky butt in a tight pair of jeans (for the ladies). However this type of training may not help improve you in your sport. The body only knows the movement patterns and the amount of force exerted during that movement. It doesn't know numbers, weights or reps. The body only adjusts to the stimuli it is exposed to, so if you expose it to just a certain movement at a certain weight, with a certain range of motion at a certain speed for a certain amount of time, your body will respond to that specific stimuli only. Basically, what I am trying to say is that if you do slow steady hamstring curls in the gym but your sport requires you to do explosive take downs, then maybe the slow steady hamstring curls may not be that beneficial for your sport - even if you do end up with nice looking hamstrings. What would be a better option would be plyometric box jumps or sled sprints to build on that explosive power.
Since the body only adapts to the specific stimuli it is presented with, it makes much more sense to do movement patterns that are the same or as close to as those of your sport. A jiu jitsu match can last anywhere between 5 - 10 minutes depending on your age and belt rank. Jiu Jitsu requires muscular endurance as well as bursts of intense power based movements so it would make more sense to do strength training in a circuit format with little rest. Body weight exercises are always best and adding explosive moments such as squat jumps and clap push ups will help you to build speed as well as cardiovascular fitness.
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