Back & Biceps are good muscle groups to pair together since they are both "PULL" moves.
BICEPS: A ZOTTMAN CURL AKA bicep curl going up and reverse curl going down. Hold 2 DBs at your side and perform a regular bicep curl, palms facing up. When your DBs reach your shoulders, ROTATE your wrists so palms are facing down and slowly bring the DBs back down to the starting position. I am holding 15lb DBs. 12 reps. 3 times.
MIDDLE BACK: REVERSE GRIP BENT OVER ROWS. With your feet apart and bent over at the waist (stick that butt out there)…. keep your back flat, DON'T round your back or hang your head! Keep your head up.
Grab a BB with palms facing up/reverse grip. Pull the BB towards your body, keeping elbows close to your body and squeeze the back muscles when you reach full contraction and hold for a second. DON'T squeeze the bar or your forearms will burn. I am holding a 40lb BB. 10-12 reps. 3 times.