They are still out there!! I got this from an athlete I work with. Someone was out in the hinterlands giving a 1970s style treatise on the pendulum swing. Well-meaning people are still out there teaching antiquated pendulum type mechanics. If you hit up to down you are inviting injury. That is the number one reason to teach bio-mechanically sound technique. This is not an opinion but a scientific fact. That loop de loop swing invites shoulder, back, and elbow over-use injuries.
Why is this still happening? Mostly from well-meaning people who are teaching others to play the way they played. I saw recently a young junior player was having arm issues. The thing that irritates me is I begged that player’s coach to listen to me when I told them about the mechanics issues because I knew this young player would be having problems. I guess pride or something kept him from listening and now the kid has to change!
I cannot tell you the amount of folks I have helped who were in pain playing. Shoulder, elbow and back injuries come seeking pendulum players. The first person I cured was myself! I had tennis elbow so bad at one point the Drs. told me I’d have to quit racquetball or get an operation to reattach my tendon to my elbow! Luckily I was able to rehab my arm by changing stroke mechanics (Thank you Dave and Gregg Peck and thank you Physical Therapist in Fishkill, NY).
Swinging a racquet on a horizontal plane has the advantage of efficiency in shot making. Most players will rate that as the number one reason for flat mechanics; but not me-I rank injury prevention ahead of the rest. Ever had tendonitis? Shoulder issues or a back operation? Then you know what I am talking about.