5 exercises that can cause injury easily

1) Upright row with your head looking down

Performing an upright row with your head looking
down places your spine in a flexed position leaving yourself vulnerable to pulling a multifidus muscle in the neck. When it comes to any joint getting hurt the neck seems to be the worst and seems to affect more muscle groups because of all the nerves passing by the neck. So be sure to keep your head straight.

2) Extremely wide grip pull-ups
Many perform there pull-ups with a very wide grip to emphasis the Latisimus dorsi (the wings). What happens is that they usually develop little tares in there branchioradialis and get tennis elbow.

3)Heavy dumbbell flys
Flys are ok if done lighter. Done heavy they can
cause damage on the shoulders and especially the
rotator cuff. If you are a small boned person, chances are you have a type 1 acromion joint and will be prone to rotator cuff injuries.

4)Decline sit ups
Decline sit ups can be devastating if you have lower back pain what happens is, in a decline sit up, your hip flexor (psoass) attaches from your thigh bone to your lower back and when starting to pull yourself up at the bottom of the sit up, your hip flexor is pulling on
your lower back into an anterior tilt which makes your spine hard to flex. If you don't have a bad back I would still be very careful with this, and don't add weight.

5) Squats on a bosu ball

The Bosu ball is round. The knee is a hinge joint meaning it moves in one direction like the hinge on a door. When performing a squat on a round surface your knees are placed in a position where the ligaments on the sides on the knee are taking the resistance, not a good Idea.