When performing exercises like deadlifts, dumbbell rows, and barbell rows the lower back will eventually fatigue as you work through your repetitions and sets. Fatigue can make it more difficult to maintain the natural arch of the lower back – which can put you at increased risk for injury. When you begin to fatigue and lose proper form you will begin to notice difficulty maintaining that natural curve – the spine will begin to round forward or flex. Ignoring this change in positioning and inability to maintain correct form can allow for a few more repetitions, but take care when doing this. Continuing the exercise when the lumbar discs are not in a favourable position in addition to having fatigued muscles is not a great idea! It is better to stop when you feel your back begin to curve forward into flexion. If you want to continue, lighten the weight, or take some extra rest. Quality over quantity. Remember, if you are no longer able to maintain the proper form for your exercise of choice, switch it up!