Tennis Racket Stiffness
Does it Matter???
Short answer - No, not really. As with any other racket characteristic, taken in isolation "stiffness" is irrelevant. It is the combination of; weight, balance, stiffness, string pattern and string options that combine to create a racket's "feel", which ultimately is all that matters to each individual player.
In regards to tennis elbow there is a lot of conflicting information regarding the impact of frame stiffness.
Stiff frames repel the energy from impact back into the ball causing greater shock and vibrations but for a shorter time. More flexible rackets absorb more energy. This leads to less shock into the body but for a longer duration.
The general consensus is that more flexible frames feel more comfortable and are better for sufferers of tennis elbow. However, this increased flexibility and associated energy loss means players with these frames will need to swing longer and harder as well as insuring a more accurate contact with the ball as flexible frames are less forgiving for "off-centre" hits. The combination of which may actually lead to more problems than solutions..