I stress technique in my writing, my coaching, and my training. Do it right before you do it heavy, do it fast, or do a lot of it. Practice makes permanent, after all.
But does it help you get more fit?
In very broad terms:
Volume will get you muscle size. Do enough reps with a proper weight, and you'll get bigger.
Weight will get you strength. Lift heavily enough, and you will get stronger.
Speed will get you power. Accelerate the weight enough, and you'll get more powerful.
Very High Reps will get you endurance. Do a lot of something and you'll get more endurance for that activity.
Those are gross simplifications, but they are basically true. Lift heavy for strength, fast for power, lots of times for muscle size, and even more times for endurance.
But what about technique?
Technique isn't on that list, but it's an underlying factor for all of those. Do an exercise right and you'll get the benefits of it. Do it wrong, and there are costs. You can exercise wrong and get benefits - volume, weight, etc. will still work their "magic" and your body will adapt.
But occasionally you might find that changing from poor technique (do a back-flexing dumbbell power clean) to proper technique (a neutral spine and hip, ankle, and knee extending dumbbell power clean) might cause you to drop in weight, get more tired more easily, and be less able to accelerate the weight. What gives? Why is "proper" technique holding you back?
And if it is, why not use the sloppy technique that is getting you those reps in, or letting you lift heavier, faster, or more often?
Basically, because of safety and the training effect.
Done poorly, an exercise changes. You may be able to lift a little heavier with a rounded back on the deadlift, or get in a few extra reps for the arms with some hip swing, or squirm up a pushup to the top. But there are downsides:
You Can Lose the Training Effect You Wanted - those extra reps or extra weight is being done using something other than the muscles and movements you are targeting. The hip-swing-assisted curls aren't really using your biceps to lift the weight. The squirming pushup is sacrificing the benefit you expect to get.
The exercise you turn it into might also be a useful exercise - but it's not longer the one you started out doing. Once you turn a pullup (upper body dominant, pulling) into a jump-assisted pullup (lower body jump with an upper body finish) you're no longer doing what you started out doing. This can mess with your programming. It's not the same exercise any more. A deadlift with a neutral spine held rigid is training your lower back to resist flexing under a load, and putting that load on your hips and legs where it belongs. A deadlift with your spine a bit loose is putting the load on your back, and not in a good or productive way. You may get a few more pounds up, or an extra rep, but even if you don't get hurt (see below) you really aren't getting the benefits of the exercise that you wanted in the first place. You're taking one step forward and then one step back instead of just a step forward.
Not only that, but the muscles are learning to work together in a sub-optimal way. They're learning to substitute for each other instead of you learning to make them work together for the maximum benefit.
Injury potential - some technique lapses can result in injury. This can be acute (you drop a weight on your foot from a loose grip, you tear a muscle) or chronic (your back starts to ache all the time, because you're letting it flex under the load while squatting). You're teaching your body to lift in a way that causes acute or chronic injuries.
Less Effective Workouts in the Long Run - Good, proper technique lets you train more effectively and more safely. The better your technique:
- the more weight you can lift.
- the more reps you can get in.
- the more efficiently you practice the movement, which in turn lets you lift heavier and for more reps.
- the more endurance you get in that specific movement.
- the safer it is, assuming it's a safe movement for you in the first place.
This makes for a virtuous circle. Remember that your body adapts to stress in a specific way - make demands for it to squat down properly and come back up under a heavy load, and it will get stronger and get better at squatting properly. Demands that it get the job done in any old way and hope for the best, and it'll do that . . . but you might not like those results.
That's why technique is important. That's why you can't forget it even for just a couple of sloppy reps to get them in. It's better to get in 9 perfect reps than 9 perfect reps and a sloppy rep that might lead to injury or grooving in bad movement patterns, and might not even get you any more than if you'd stopped on the last good one. Remember weight training is just expressing movement with an external load, not hiking the weight up in the air however.
Technique is your pathway to a long, healthy training life. Do your best to stay on that path.