Today, I want to talk about Isometrics.
There's really three types of muscular contractions. Concentric, when a muscle shortens, eccentric, when a muscle lengthens, and isometric, when a muscle isn't changing length at all. If you take the concentric and eccentric movements and combine them together (like in most gym based movements, you get what's called an isotonic contraction.
Isotonic make up the significant proportion of what we do in the gym, and they are pretty awesome. You can manipulate the speed, duration, intensity and volume of them to manipulate your performance or sporting outcomes.
But there is also a place for isometrics in your program. Isometrics are by no means a replacement for the functional isotonic work that forms the meat and potatoes of most gym programs, but they can have a profound positive effect on tissue quality, improving durability, performance, and helping in recovering from injuries like Osgood Schlatters and shin splints.
Here are my four favourite benefits:
#1: Increase time under tension for short range of motion movements.
With isotonics, there's a level of bounce that tendons give to movement (known as the plyometric effect). That means the muscle, during those movements, isn't actually working for the entire range of motion.
A great example is with rotator cuff external rotation work. It's so easy just to bounce in and out of position. But by doing a hold, that infraspinatus is forced to hold its contraction for much longer.
#2: Spare joint stress.
If you have a grumpy knee, there is a pretty good chance you've also got an inhibited and a weak VMO muscle. That means you need to build that guy up.
To build that VMO up, knee extensions are a great starting place, but they can also irritate the joint as you increase flexion and apply greater patellofemoral compression. By instead holding the weight close to end range, you minimise joint compression and cartilage irritation while still putting some time under tension into the VMO.
#3: Work the weak point.
All muscles have a natural tendency to work harder at some points and easier at others point depending on the joint angle and muscle length. For example, the bench press is hardest a couple of inches above the chest (this is called the sticking point and is different for every exercise). You want to spend more time working muscles at or near their sticking points, and less when you're at an advantage in positions of biomechanical advantage.
This applies perfectly to hamstring curls. It's easy to start and finish a curl, but between roughly 90º and 135º of knee flexion the hamstring has to work at it’s hardest, if you really focus your work there (either moving slowly through it or doing holds at that position), the hamstrings are going to be doing a whole lot more work.
#4: Think about muscles in terms of the function as opposed to the action.
The textbook definition for each muscle would be the action it performs, but its action doesn't always correlate to what it does in the real world (Glute med is a perfect example).
I think this applies perfectly to the core. The core is designed to provide stability and resist motion. Think of it as an anti-movement device. Planks and side planks are much better options for core training than things like crunches or Russian twists.