The Weight vs. Reps Argument.
When you think about fitness, the first thing that comes to mind is weight. Whether it's how much you can lift, how much you weigh, or how much you know about weights, chances are good that it's a weight. While that makes sense on the surface, your coach (and most coaches) would tell you that there is more to it than weight.
There are a lot of things coaches track when they're training athletes: The number of reps completed, the amount of weight on the bar, or even how fast the weight is moving. But which one of these things is most important? Many of them will say that the number one thing they track is the amount of weight an athlete can do with a given number of reps, usually 1.
So why do coaches track different numbers? This is largely based on how they were taught. Because the personal training industry, and the fitness industry, are unregulated, many different coaches can have certifications and teach their specific model of fitness. There are more proven methods out there that show consistent data over long periods of time. I think the “wild west” portion of the fitness industry is a net good because it allows coaches to explore things that have not been tested and can be explored more freely.
Some coaches believe that reps are the most important indicator of success and others believe that weight is more important. Your own programming will reflect your personal beliefs. If you're focused on reps and sets, you'll program with variable weight and a rep range in mind. If you're focused on strength and power, you'll program with a variable rep range and a weight in mind.
Because different coaches have different ideas about what to track, they can prove or disprove certain benefits of training. An easy way to identify what is being tracked is to look at their programming: sometimes you'll see a rep range and other times you will see a weight range. Sometimes you'll see a velocity range and sometimes there won't be weight listed at all. It's all because each coach uses their own way to keep a constant variable. When testing an athlete by long-term programming, constants are something that you can test against. Like a weight for a variable number of reps or a set number of reps for many sets with increasing weights for each set.
It's also possible to measure progress by using velocity tracking as a constant instead of reps or weight. Velocity-based training (VBT) is a method of monitoring progress in strength training. It uses speed as a measure to determine how quickly an athlete is progressing. Velocity tracking can be done in many different ways, but the two most common are using tracking devices such as force plates or accelerometers and using video cameras. While velocity tracking is not as common as other methods, it has been gaining popularity recently, although the science behind it is still under study.
So as you can see, there is more than one constant that you can use to measure progress. However, none of these constants are perfect. You will always have outliers in each category. Athletes will be fast one day, and slow the next, allowing for a bad evaluation of performance. So don't be held down by what you think success looks like when programming. No matter what type of program you are doing, you should give your best performance for the day. If there is something wrong with your training methods, then it's time to make changes that will better benefit your body and long-term development.