This is the real key to maximizing the benefits from your workouts.
But not really.
In truth, you don’t get any credit for performing the 9th rep. Stated otherwise, performing more reps isn’t an end in itself, it’s a means to an end and an indication that you are, in fact, improving.
The real focus, toward the end of the set of any exercise should be, “I need to fail with perfect form.” Altering form to get one more rep satisfies our innate desire to “improve” but this really isn’t improvement if we have altered our form, accelerated through a transition and used momentum, or locked out our arms or legs to rest a bit before we attempted the next rep.
Make no mistake, we should attempt to improve and complete that 9th rep but our real objective is to fail with perfect form. This is the stimulus for our physiology to change.
Apply this in your next workout: On rep 8 or 13, when you are uncomfortable and closing in on muscle failure, put your entire physical and mental focus on reaching muscle failure with perfect form. And then, let the rep number fall where it may.