Single-arm shoulder press in sitting with dumbbell

Sit upright in a chair with your arms relaxed by your sides and hold a weight in one hand.
Bend the elbow and bring the dumbbell towards your shoulder keeping your upper arm by your side.
This is your starting position.
Then press the dumbbell up towards the ceiling and straighten your elbow.
Keep your neck muscles relaxed as you move your arm.
Return to the starting position.