The impact position according to many golf professionals is the most important position in the golf swing. Impact will determine direction, trajectory, and ball speed. Errors in any phase of the golf swing will most likely "show up" at the impact position and have a negative effect on the intended ball flight.
In order to create an effective impact position with the intended face and attack angle of the shot, requires each phase from the address position into the downswing to be performed in a biomechanically efficient manner. Inefficiencies in terms of timing or sequencing will typically effect the impact position and cause the development of compensations in the swing in an attempt to overcome these inefficiencies.
In order to accomplish this requirement of creating a biomechanically efficient golf swing where the correct impact position is created requires certain physical attributes to be present within the body. To explain the physical requirements required in the execution of the golf swing we can look at the body-swing principle.
The body-swing principle states that in order to execute a biomechanically efficient golf swing where speed is generated and transferred efficiently into the impact position requires certain physical parameters (flexibility, mobility, strength, stability, power) to be present in the body. If the body is lacking in the required levels of mobility, flexibility, strength, stability, and power, the ability to execute an efficient golf swing will be impeded. Such instances typically result in the development of compensations in the golf swing in an attempt to overcome these physical dysfunctions.

In order to understand what muscles require strength and what joints require mobility to execute an efficient golf swing we can turn our attention to the Mobility/Stability Pattern of Human Movement. This principle states in order to create efficient movement or athletic actions, the body must operate in an alternating pattern of mobile joints and stable body segments.
If this pattern of mobile joints and stable body segments is altered, dysfunction in movement patterns or athletic actions will occur. Relative to the golf swing this principle indicates the ability to execute each phase of the golf swing, generate speed, and transfer this speed to the golf club will be impeded if dysfunction exists within the mobility/stability pattern of human movement.
A joint-by-joint review of the mobility/stability pattern of human movement indicates the following: Ankle -- mobile, knee -- stable, hip -- mobile, sacral/lumbar/pelvic complex -- stable, thoracic spine -- mobile, scapular/thoracic spine -- stable, gleno-humeral joint -- mobile, elbow -- stable, wrist -- mobile as it pertains to efficient human movement and the golf swing.
Taking the information provided by the Mobility-Stability Pattern of Human Movement Principle and applying it the ability to create a biomechanically efficient golf swing, where the intended face and attack angle are present at the impact position indicates joints must be mobile and other body segments stable.
Mobile joints require specific ranges of motion within the actual joint structure and flexibility of the soft tissues (i.e. muscles) surrounding the joint. Whereas stable body segments require strength in the muscle associated with the body segment. Execution of a biomechanically efficient golf swing requires a combination of both.
One joint structure for many golfers impeding their ability to perform a biomechanically efficient golf swing are the hips. The hips are a ball and socket t-joint, requiring a large range of motion in order to execute an efficient golf swing. Any dysfunctions in terms of the mobility in the hips can easily affect the backswing, downswing, and the impact position.
A very effective golf fitness exercise to improve hip mobility is Windshield Wipers. This exercise address both the internal and external rotation of the hips, both of which are essential in the execution of a biomechanically efficient swing.
To perform the Windshield Wiper mobility exercise place yourself on the floor, back flat, knees bent at 90 degrees, hands between both knees, feet together, and head resting on the floor.
Slowly separate your feet keeping the knees in place and bent at 90 degrees. Create the separation of the feet through rotation at the hip joint. Separate the feet as far as possible apart while keeping the knees and hands in contact with one another. Return to the starting position and repeat for the 10-15 repetitions.
The ability to execute a proper impact position hinges upon the golfer executing a biomechanically efficient golf swing. A efficiently execute golf swing allows for speed to be developed and transitioned properly to the club head as well as creates the correct attack angle and club face position at impact.
In order for a biomechanically efficient golf swing to occur, certain levels of mobility and stability must be present in the body. This allows the golfer the opportunity to execute a biomechanically efficient swing where a proper impact position is executed. Golf fitness exercises can be very beneficial in developing mobility and stability within the body to achieve this goal. To learn more about Sean Cochran and his golf fitness training exercises go to http://www.seancochran.com.