Should you perform a specific number of reps?
The answer is, it depends, however the broad over arching answer is no.
Although this discussion assumes you would like to gain strength, improve muscle definition, lose weight or become a better lifter.
(If your goals fall outside of this, this discussion may not apply to you.)
Here's where there is a fork in the road, if you are novice versus intermediate in your weight/resistance training experience.
Novice meaning less that 1 -2 years of experience in the weight room. If you're newer to the weight room:
One, welcome and congratulations.
Two, your goal maybe better served by focusing on mastering movements and steering clear of "failure" in terms of muscular fatigue, MOST of the time.
As a novice you'll get much more out of improving and dialing your technique, with challenging weight, to a set number of reps.
While this should include "burning," increased exertion, and some muscular fatigue, going to failure may work against your over arching goals. i.e. improve the efficiency of how you move to maximize return on investment on your time in the gym.
Likely this is a 5 - 6 on the rate of perceived exertion (see the chart below) and rarely but occasionally visiting a 7 - 8.5 level of effort.
Your efforts are best spent between the 6 - 20 rep range at various levels of perceived exertion.
Now if you're an intermediate (2 years +) lifter this may mean that you're missing out on a chance to see strength and hypertrophy improvement if you're not reaching a level of fatigue nearing failure.
A great strategy to maximize strength or hypertrophy as you improve your "training age" aka years of lifting, is to base your exercise on how many reps are left, instead of how many total you complete.
This strategy is known as Reps in Reserve (read: how many reps are left in the tank at the end of the set.)
This allows you to capture additional, and often dynamic rep ranges to ensure you're creating enough stimulus to elicit the desired response, and while various rep ranges can be used for your particular goals (ie strength, hypertrophy, endurance or variety) you can reach an ideal working volume by listening to how your body is managing fatigue.
Likely this is a 7 - 9.5 on the rate of perceived exertion (see the chart below) leveraging general warm up and warm up sets within your training to support your higher intensity working sets.
Your efforts are best spent between the 3 - 20 rep range, (depending on your goal possibly even higher or lower!) at various levels of perceived exertion.
Here is a great chart covering the Rate of Perceived Exertion relative to Reps in Reserve that can really dial up your training effect by keeping you from "checking the box" and getting you to challenge the muscles.
If you have any questions don't hesitate to reach out:
alex@elevatemytraining.com
Always happy to geek out and answer nerdy questions about how to get the most out of your training!