When it comes to Isometric Training, we generally learn 2 distinctive styles: Overcoming & Yielding. Overcoming Isometrics is using great force against something immovable such as a wall or a curl using a strap. It's one of the more common uses of isometrics as it teaches how to maximize the tension with such great force that only a few seconds will be needed. You can do longer durations of Overcoming Isometrics with less intensity which can aid in hypertrophy and endurance. Yielding Isometrics are in a nutshell, various exercises where you're fighting gravity and you keep a certain position or posture for a period of time such as a plank, wall sit, horse stance, hanging from a pullup bar or a stopping point in a pullup. These are more likely done using areas of Yoga or Qi Gong where posture type training focuses on the energy in your body while externally creating load.
Both styles of Isometrics have their pros and cons and various people prefer one or the other like those who are fond of the Iso-Chain (Overcoming Isometric Device) and those (like a certain Blue-Collar roughneck) who like to hold horse stances and push-up positions for time in order to build long-term strength and conditioning (Yielding Bodyweight Isometrics). Personally I like the Overcoming style because I can generate as much force as possible for a few seconds and get better results. From time to time I'll do Yielding like holding a stance for 3 minutes or so, 1 minute fist plank or mid-range fist push-up, 3 minute bridges or several 1 minute sets of wall sits. Both work really well regardless.
Hybrid Isometrics however is a completely different animal that utilizes both styles at the same time and create such incredible strength that they're a bit more difficult than one style or the other. Imagine going against gravity but at the same time hit a sticking point that generates a lot of force to stay in place. Even very powerful guys who can do solid isometric work would have trouble holding a Hybrid version for more than a minute because you're not just engaging muscles, there's certain coordination involved and it takes another level of the mind/muscle connection for it to work. I would bet that even someone who can hold a 5 minute plank wouldn't even come close to that if they used a strap for the Hybrid version. Shaking like a leaf in a matter of seconds would be an understatement.
The great benefit you can get from Hybrid Isometrics is that they don't take long to feel everything. Because of the strength needed to stay in place but also push or pull against something immovable, you're getting the best of both worlds and can create another level of strength and endurance that could carry over to everyday life. Below are a couple examples of Hybrid Isometric Training that you can try. The first is the Hybrid Push-up where you would wrap a strap around the upper area of the back and press against the strap with bent arms in the push-up position. This works your whole body like crazy especially the core muscles just to stabilize you while you maintain incredible tension. The second is what I call the Isometric Zercher Squat where you put the strap around the inner area of the forearms (as if you're holding a barbell in the front of the body) and you get into a squat position (preferably mid range or a quarter squat) and drive upward. This really tackles the tendons and ligaments in the legs and strengthens the lower back and core muscles for stabilization.
If you did just a couple sets each for a maximum of 30 seconds at a time, you'll be getting the workout of your life and feeling muscles you didn't think you could feel. Just a couple minutes and you'll feel like you just ran a marathon, it's about as intense as it can get. There are other exercises you can learn on Hybrid Isometrics by grabbing the book Overcoming Isometrics from Red Delta Project. One of the best books out there today on the subject of Isometric Training.
