This exercise: Builds upper body strength and makes your shoulders more stable. 
Steps: 

1. Sit upright, engaging your belly and maintaining good posture. 
2. Hold a small bottle in both hands or other small weights at your sides. 
3. Keeping your arms straight, raise the weights in front of you to shoulder height, and hold for 5-10 seconds. 
4. Lower the weights back down with control. 
5. Do 3 rounds of 10-12 counts.