The two most significant sources of power are hip and shoulder rotation (Angular Momentum) and weight transfer (Linear Momentum). These power sources are important fundamentals. Any stroke can be placed in to one of three categories. These categories are based on the stroke’s most significant source of power.
- Swinging strokes (ground strokes, serves, swing volleys) use angular momentum where hip and shoulder rotation is the most significant source of power.
- Punching strokes (volleys, half volleys, difficult returns) use linear momentum where weight transfer is the most significant source of power.
- Some strokes require a balanced combination of both sources (approach shots and high volleys).
In angular momentum, the hips and shoulders are literally the central gears of the swing system. An efficient swing is a series of rotational movements that flow in sequence and balance is critical to initiate this rotation. The feet must be in contact with the ground, and there cannot be a disconnect between the upper and lower body. With the hips and shoulders the central gears, the muscles between the hips and shoulders are significant. The swinging movement begins with the muscles of the trunk. Because of the elastic action of the muscles between the hips and shoulders, a relatively small degree of hip and shoulder rotation can account for a high proportion of swing force.
The hips and shoulders are not efficient power sources for all strokes though. On a low volley, hip and shoulder rotation can be detrimental. On this shot emphasis should be placed on weight transfer, or the use of linear momentum.
It is critical for an aspiring high performance player to understand these power sources. As a player you want to be efficient to ensure a long career in tennis. Efficiency means effective results with little waste of energy. So many great players don’t reach their full potential or careers are cut short due to injury because this fundamental was neglected or not properly trained at a young age.