Don't worry about the weight, just slow down.

Your body doesn’t know the number of reps you’re doing or the weight on the bar. It only knows the tension it must create to overcome a load, and the time that tension takes. In other words, if your goal is to build muscle you should stop obsessing over the weight on the bar and instead focus on the contraction of each muscle.
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Slowing down your lifting tempo allows you to both improve your mind-muscle connection and increase your time under tension, a key component to increasing metabolic-stress driven hypertrophy.
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Try a 3111 Tempo
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• The first “3” is the eccentric or negative.
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• The second number is the “bottom” of the rep. In this case, take a one second pause.
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• The third number is the concentric or the “up” phase, so you should lift “up” in one second.
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• The final number is the end of the rep before beginning the next. In this case, a one second pause between each rep.
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