Breathing is bracing.
Bracing means greater tension.
Greater tension means greater strength.
Greater strength means better results.
The breath (or better said: the WAY we breathe) plays a crucial role in perfomring every single rep of our lifts successfully.
WHY do we breathe in weightlifting? And more importantly: WHEN and HOW do we do it?
The number one reason why we breathe in strength training is to brace the body to produce more force.
Let's take a short excursion to the anatomy of inhaling and exhaling:
When we take a breath in, we fill our abdominal cavity and lungs with air.
Picture your abdominal cavity as vacuum behind your abdominal wall: When you inhale, you fill this space with air. Imagine you are expanding a balloon inside this space. Through this mechanism, greater pressure is produced towards the front, back, and side of this cavity. Eventually, this pressure is "recognised" by the lower back, adominal, and oblique muscles. As such, those muscles are receiving a message to "TIGHTEN UP" their grip around the abodminal cavity.
A tigther "grip" means more stability, reduced risk of injury, and better performance.
A good way to feel this effect is to draw air into your chest as well as upper part of your tummy. As you will observe, both your chest and shoulders start raising as a result of that.
Do you feel MORE tension in those areas when you breath in - or LESS tension? (the answer is obvious).
Comparatively, when you breathe out, do you feel more - or now LESS tension in those areas? (again, obvious answer).
In summary: breathing means bracing, which means greater tension, which means greater strength.
Secondly: WHEN do breathe in our lifts?
We breathe in before we lift (or lower) the bar. This may sound very obvious - but I have seen many beginners who are not accustomed to correct breathing yet and breathe in when the body is already under load. Too late.
Picture the breath in as a "GO!" signal for your lift to start. Breathe in - ready!
Thirdly: HOW do we breathe for better lifting performance?
Breathing correcly means drawing a short burst of air into your chest and upper part of the tummy. Once you've done that, imagine "sealing the jar" by closing your mouth and holding the air tight inside your body. When you do this, air cannot escape your mouth.
It is important to understand that you must NEVER breathe in through your nose when lifting weights. Reasons are that number one, you cannot draw as much air in through your nose as when breathing in through your mouth - and number two, there could be case of slight fainting by nasal breathing as the air usually ends up in your head rather than where it should go.
Lastly - and this is perhaps the most important aspect of breathing - is the concept of RHYTHM through regulating our breath.
Rhythm is a qualitative concept which describes the "perfect" sequencing of actions to perform a physical task successfully.
Rhythm - in comparison to cognitive thinking - is not subject to the motoric aspect of movement learning. An example: the first day you learn how to do the Press, you are instructed where to place your hands on the bar, where to place your feet on the floor, how to initiate the hip movement, how to lock your arms - etc.
This is highly COGNITION-based - almost ROBOT-LIKE - where steps are learned in a clear, logical way.
Rhythm - on the other hand - is a subconscious way to perform movements in a fluid way which negates the need for rational thinking. When you have rhythm, you can tell that your movements feel much more NATURAL - almost like you don't have to "think about them".
This is where breathing comes in:
The in-breath signals the start of the movement - the out-breath signals the end of the movement.
Repeated several times, the breath sets the rhythm for your reps to be performed in a fluid, "natural" way.
If you don't believe in the concept of rhythm (or haven't understood it yet), try constantly breathing in and out in sharp turns when you lift - and let me know how it goes.