Small changes in how you pull or press shift which muscles work. Pull rows to your chest for upper back, toward your hips for the sides. Arnold press hits side delts instead of front. Overhead extensions work your triceps' long head better than kickbacks.
If you pull the bar to your chest on bent-over rows, you are going to work more of your upper back. If you pull the bar back to your hips, you are going to work more of the side of your back. If you do a regular shoulder press, you're going to work more of the front of your shoulder. And if you do an Arnold press, you're going to work more of the side of your shoulder. If you do tricep kickbacks, you're going to work more of this part of your tricep. If you do overhead triceps, You're gonna work more of this part of your tricep. And when you hold a plank for a minute, you're gonna look at the clock and see it's actually only been like 10 seconds.
