A key component to proper form during strength training is maintain correct spinal position. The spine, with its many joints, wants to move but we do not allow it to. Perfect case scenario the spine is held in ridged extension.
Keeping the spine straight requires several parts
1) Proprioception (awareness)
2) Contraction of the back muscles (spinal extensors - erectors and latissimi dorsi)
3) Proper breath (thoracic and diaphragmic breath with the Valsalva maneuver)
4) Contraction of the core muscles (spinal flexors - rectum abdominis and obliques)
The combination of these four aspects will constitute the most effective bracing mechanics allowing for the spine to stay ridge transferring force through the trunk and into the larger joints responsible for moving a barbell as possible.
Proprioception
As you lean your torso forward it’s the erectors verses the hamstrings which are battling for pelvic control. The erectors must win. If it doesn’t the pelvis will tuck under and back will round.
In the proper hinge position, you should feel a stretch in the hamstrings. To exhibit incorrect pelvic position, allow your back to round. This will cause the tension in your hamstrings to go away. This shortens the distance between ischial tuberosity and the head of the tibia and fibula, the attach sites for the hamstrings.
Slacked hamstrings do not effectively aid in hip extension, not to mention it places the back and knee in a vulnerable position for injury
Back
Now that we’ve establish spinal position, we’ll need maintain that with a conscious effort to extend. Arching the back hard and keeping the chest up while hinging is what the lifter needs to think about. There are some cases where this overcorrection cue will place the lifter in hyper extension. In this case it will require some fine tuning to get the right amount of extension.
Breath
Before we start moving the bar, we must hold a big breath. A good rule to impart: anytime the barbell is moving you are holding your breath.
There are two ways you can breathe using the diaphragm or using the chest. Ideally, we want the diaphragm to contract first then the thoracic respiratory muscles.
Many people will be chest breathers. Meaning if instructed you to take deep breath with your right hand on your chest and your left hand on your belly and asked you which hand rose. If the chest rises that means we are not effectively using the diaphragm.
To effectively brace a we’ll need a combination of both for the best spinal tightness. This can be done by breathing into the belly as much as you can then continuing to fill the chest cavity as well.
If you can’t use you’re diaphragm this doesn’t mean you can’t brace it just means it will limit your ability to produce maximal intraabdominal pressure. In some cases where one holds a lot of mass in abdominal region there is very little difference between bracing only using thoracic breathing and a combination of both diaphragmic and thoracic breathing because of the reduced space in the abdominal cavity.
Core contraction
After the air has filled up the ventral cavities of the body it’s time to lock it all in place by flexing the abdominal. This tightness should be fine turned for the application. 1RM attempt, you’ll full exertion, for something your doing 20 reps with, you made need about 60% core tightness.
Fun Fact: A lifting belt works by restricting the expansion of the belly. When you breath in, the breath expands to belt then start to pressurize the abdominal cavity. You are able to start with a higher intrabdominal pressure before the abdominal contraction, making the core even tighter.
Keeping the spinal immovable will allow for the safest most effective lifting as possible. As you get stronger your ability to brace effectively will get better. A lifting belt allows for more effective bracing. Coupled with a strong back from frequently lifting will allow you to lifting heavier weights. Getting you one step close to your goal of being stronger.