With regards to training tennis players, I am wary of prescribing cable based, loaded rotational movements as I am unsure as to whether they will have a negative impact on such skilled motor patterns as those seen in tennis. Would training the abdominals toward their function as anti-rotators through stable core movements be more beneficial and have less impact on skilled rotational movement patterns?
When training clients for specific sporting activities, it is important to analyze the nature of that sport when designing an effective program. With your question in mind, let us consider a tennis shot. On both the backhand and forehand side, the majority of the power comes from the core muscles (transverse abdominis, multifidus and obliques) and the upper body muscles (pectorals and deltoids). Cables are an effective method for training the above muscles in a way that is specific to the rotational component of a tennis shot. In direct reference to your question on whether this type of training would be detrimental to the client in terms of motor skill performance, I would say no. I would never train a tennis player to perform core exercises in a way that is not specific to the game of tennis. Performing an abdominal crunch, for example, would almost certainly have a detrimental affect on an individual’s ability to perform motor skills because he or she would not be using their core muscles in a way that is specific to tennis.
I use several methods to train my players. Medicine balls are great for trunk rotation training and are more functional than cables. I find that rubber resistance bands are highly effective when training core function in a tennis shot. Here is a good tip: Tie one end of the band to a non moving object such as a pillar and tie the other end of the band to the upper handle to a tennis racket. Get your clients to practice their strokes. The added resistance will require individuals to work harder through the transverse plane and therefore promote core stability and strength. Search the PTN Exercise Library for more ideas on how to use cables, bands/tubing and medicine balls. In summary, just remember to be specific when training clients for sports. Good luck.