A solid chunk of the gym population does not warm up sufficiently or even at all before they get into their training. I get it, time is money, and if you only have an hour to squeeze your workout in, it's better to allot that time to the real "work" and meat and potatoes of the workout, right?
Actually, you'd be better off cutting into your workout time. Why?
In my skating world back in the day, warmup was an autopilot thing and I did it without fail- every single time. We all knew that our on-ice performance was bound to be a hot mess if we didn't go through every little bit of our warmup routines off-the ice first, then part two on the ice. It was ritualistic. Every elite athlete in the world has a specific warmup for whatever their sport may require of them on the field that day.
Think about it this way-- when it's 30º outside and your car has been sitting in an outdoor parking lot for the past 8 hours, do you hop in, turn the ignition on and slam on the accelerator, trying to go 80mph from the get go? If so, how well do you think that's going to work out for that engine? Have I been enough of a metaphorical jerk to make my point yet? Oversized kitty paws to the right to makeup for that.
Here's the thing- the majority of the population usually comes to the gym in two ways: either having rolled right out of bed in the wee hours to squeeze in their workout before work, or coming into their workout having sat hunched over at a desk in front of a computer monitor all day.
Your body is begging to be moved around and opened up before you decide to run, spin, sprint, load all your joints and muscles up with a heavy weight or anything else. Skimping on the all-important warmup is a quick shortcut to poor performance and/or injury. It's something people commonly know that they should be doing, yet frequently skim over it.
There is a myriad of great ways to get your body moving and there isn't one perfect or precise way to warm up.
But whatever you're doing, you should do it with intention, purpose, and diligent attention to quality of movement. Watching someone flopping around for a half-hearted stretch, some arm circles, checking email for 5 minutes sitting still, then sitting down to a loaded up bench press makes me feel like this:
As for warmup exercise choice: the way I tend to think of it, is what is on the menu that day for the training program? It's like making a marinade for a chicken- if the dinner theme is Mexican, you're not going to use Italian seasoning. If I am going to do some heavy squats, I'm going to tailor my warmup to focus on getting my hips and ankles mobilized and activating my glutes.
I typically like to do a combination of self-myofascial release (foam rolling, trigger point therapy), dynamic warmup, mobility drills, and a little aerobic warmup (rowing, jogging, biking, etc), pending on what I'm working on and what my goals are.
But regardless of what the training goal is of the day, the 4 primary purposes of warming up are:
1. Increasing your heart rate, breathing rate, core body temperature, and blood flow to your muscles.
It's important to get your body temperature up and even break a little sweat while you're warming up- it's essentially like preheating an oven.
2. Mobilizing the joints needed to be mobile, and increasing flexibility/extensibility of muscles.
Primarily speaking with your joints, your hips, ankles, and thoracic spine (tspine in human speak= upper/mid part of the back). This also can help quiet down some muscular imbalances that rear their ugly heads on difficult exercises that pretty much everyone has.
How will that squat feel with tight hips and ankles? Or that overhead press with rounded, tight shoulders? Those hamstrings should also probably get some warmup love before you decide to lift a barbell with them.
3. Engaging your nervous system
Your body is constantly exchanging electrical signals with your brain. That is how you move, breathe, think, and live. There are some automatic functions that our bodies will do without us actively telling it to like breathing, but then for things like movement, we want to prime and engage our nervous system to be extremely responsive to produce the most efficient movement possible.
If you're doing work on a computer then walk away for let's say 10 minutes, the computer monitor might go to "sleep." So when you return, you have to move the mouse back around to let it know you're back before you can start typing away and asking it to do a million things. Same thing here- warming up is priming your body to be ready to go so you get way more bang for your buck with whatever workout you are doing.
4. Laying down proper movement patterns
You know how they say practice makes perfect and that what you repeatedly do is a habit? I mean, nobody is becoming Jean Claude Van Damme (below) overnight, but your 10-15 minutes of warming up is already fighting an uphill battle with your rounded keyboard-tapping master shoulders.
So the more consistently you engrain those proper movement patterns, the more likely you'll translate them into better posture and movement in real life in addition to your likelihood at maintaining proper form on those tired, ragged last reps