Having flexibility in your hips are important to be able to maintain your posture and keep your spine angle throughout your swing. Tight hip flexors may cause low back muscles to weaken leading to low back pain.
Lie on your back with legs extended.
Bring one knee to your chest trying to keep your other leg extended straight.
Hold position for 8 to 10 counts
Return to the start position and repeat on opposite leg.
Do 8 to 10 repetitions on both legs.
If you cannot straighten the leg on the floor, then you will need to work on increasing the flexibility in your hip flexors.