First, kudos to you for trying to teach stroke mechanics to your kids. Too few high school coaches work with their players. Thus, those without private lessons keep on with their pushing ways that served them reasonably well when they were younger.
Check out the following video of Soderling serving and you can see how he uses the powerful muscles in his whole body, from his powerful leg push off to the incredible sideways forming a bow, then reversing the bow, to power his serve with his core muscles:
http://www.youtube.com/watch?v=a56pvP1i6x8
This is a video worth replaying many times, stopping it every time a teaching point is made to fully understand all of the great points:
- ball tossed with a straight arm, moving only at the shoulder, with no hand or elbow flip
- holding the ball like an ice cream cone
- ball release is just after raising it past the shoulder to get it to come back to the contact point in an upside down J shaped parabola
- the tossing arm keeps going up and up and up until the tossing arm is straight up, and held there to balance the server in the trophy pose.
- having the tossing arm straight up means the hitting shoulder is very low and the tossing shoulder is very high.
- the three sources of power are the leg drive, uncoiling of the shoulders and hips, and the powerful reversal of the bow shape as the shoulders "cartwheel" [quickly vertically reverse so that the back shoulder goes straight up while the front shoulder goes straight down] - the shoulders should not just be swung around from right to left.
- the bow shape at the trophy pose [the player is in the shape of a bow when viewed from the side] involves getting the front hip forward to counterbalance the sideward lean of the upper body.
- the trophy pose is point where the player is fully loaded with all three body parts - full coil, full bow shape, and full leg bend.
- the power in the serve comes from quickly and forcefully reversing all the pent up sources of power - first the powerfull leg push off, followed by the powerfull uncoiling of the shoulders/hips and the powerful reverse of the bow shape with the vertical shoulder over shoulder cartwheeling.
- the leg pushoff is virtually straight up, with only the slightest push forward into the court
- the deep racquet drop only possible by getting elbow pointed straight up
- the importance of PRONATION
- the body stays sideways at contact
- land on the left leg, with the right leg going directly backward [a sign your players have too much uncoiling and not enough unbowing/vertical shoulder over shoulder cartwheeling is if they swing their right leg around to the right, rather than push it straight back.]
Really, watch the video again and again. It shows you the sources of power your players are lacking, but it also demonstrates the fine points of the ball toss, keeping the tossing arm straight up for balance and proper deep shoulder angle, and the proper way to land on the front leg with the back leg kicking back.
Virtually the same points are made in Nick Bolletieri's sonic serve video:
Nick Bollettieri-Sonic Serve.wmv
http://www.youtube.com/watch?v=ajoZ0f7hw-A
But here are the videos that emphasize each of the components, and give a better feel and understanding of each one:
Tennis Serve Toss - How to Hold the Ball like an ice cream cone to avoid having to turn the wrist outward as you get the ball higher in the more commonly used hand toss
http://www.youtube.com/watch?v=M8kynEzufNE&feature=related
Tennis Serve Tossing Motion Tempo: how to start to coil away from the ball with your body as you bring your arm up and up and up, releasing the ball just past your your shoulder height and continuing to bring it up and up and up at the same pace as before release until your tossing arm is straight up to help balance you into a hip out trophy pose
http://www.youtube.com/watch?v=CeZp90h-Ar8&feature=relmfu
Watch how Federer, Murray, Hass, Hewitt, Davydenko, Safin, Tsonga all make the same move when tossing the ball, keeping their tossing arm parallel to the baseline while they coil their shoulders and hips back (and also bending their knees to allow that coiling) at the same time they keep bringing their arms up.
http://www.youtube.com/watch?v=lIF-UaRUd6k&feature=related
Tennis Lesson: Serve Tips: Lead with the Hip to get into that powerful bow shape
http://www.youtube.com/watch?v=HgeYmEScfgQ
Coach McCraw explaining a serve pronation exercise to get that powerful slap at the ball that will result in real "pop":
http://www.youtube.com/watch?v=iONY6fcqZGg
Getting the proper vertical shoulder over shoulder cartwheel action is important not only to get pop and spin on the ball, but is important to prevent rotator cuff shoulder injuries:
http://www.youtube.com/watch?v=lTRvxaBMh8s
Your serve technique doing more harm than good? "Aiming your chest up at the ball" while leaning back from the knees [not by arching the back] by getting the heels way off the court, lets the arm swing up and over the ball to get that topspin needed to bring a powerful serve in (while sparing the shoulder from abnormal stress).
How to land on your front leg and kick back with your back leg, so you land balanced and can quickly split step and be ready for the return:
http://blip.tv/fuzzy-yellow-balls/leg-kick-on-tennis-serve-1190196
I don't have a video on this, so my explanation will have to do.
It concerns of
when to get in the bow shape during the "toss into the trophy pose" sequence.
In the photos below, notice that as Pete Sampras is bringing his arm up and up and up, he is coiling with his shoulders and hips (with the necessary knee bend to allow himself to do this (pics 1-6 below). While there is a little bow shape present, most of it occurs late as he allows his front hip to swing out counterbalance the greater sideways lean with his upper body late and gets a much deeper knee bend very late going into his trophy pose (picks 7-9 below). Getting into this deep a bow shape challenges a players balance, so that sinking (squatting) ever lower helps to really maintain the balance. Doing that accentuated bow shape/knee bending/squatting late means the balance only has to be held for a fraction of second into the powerful leg push off (pics 10-12).
[While those pics are up there it might be good to re-emphasize some of the previously made points:
Pic 9. Great trophy pose, with chest pointed up at the ball, heels off the ground to "bend from the knees", not by arching the back, and front hip out. Tossing arm still straight up to get that steep shoulder angle. Hips and shoulders fully coiled.
Pic 12. Deep racquet drop with the high elbow (elbow pointed straight up) to achieve that deep racquet drop
Pic 13. Side of racquet still largely pointed at the ball, with most or the powerful pronation movement to occur in the last split second up to, through and past contact. Notice the hitting shoulder straight up now and the tossing shoulder straight down. The side of his body (not the front) is directed at the deuce court as he powerfully cartwheels sideways in the direction of his serve.
Pic 14. His pronation movement is so powerful, that the follow through has his racquet pointing down even as his elbow appears straight in his rapid pronation follow through. He is going to land on his left leg, with his right leg kicking straight back, so that he will land balanced and can go into a split step to get ready for a return (although in Pete's case, he often kept charging right in for a serve and volley.)
Since your kids are going to have to practice a lot to get a good serve down, they better be strengthening their shoulder area and arms with these simple exercises to avoid an overuse rotator cuff or elbow problem.
Thrower's ten exercise program:
http://www.muhlenberg.edu/pdf/main/athletics/athletic_training/throwers10.pdf
Some of your kids will easily be strong enough and have enough balance to work on their serves, especially if they have had either specific tennis conditioning or are coming to spring tennis after fall and winter football, wrestling or basketball programs. Others will need to do at leas body squats and burpees to build up the strength and balance to get into an agressive trophy position and hit out of it.
Your most ambitious junior tennis players may even want to work out in routines found in Sports Fitness Advisor: Tennis Training Section
http://www.sport-fitness-advisor.com/tennis-training.html not only for this season, but to get ready for next season as well.
I spent a little time in this post because you are a teacher, and easily can absorb the info. Also, you will have an influence over multiple players under your care.
As a teacher you understand that they can't incorporate all of the aspects at once, anymore than you wouldn't assign them a whole year's material on day one.
Perhaps at first how to toss into an aggressive, but balanced, trophy pose could be a first goal.
At the same time, doing Coach McCraw's pronation exercise could get them the proper swing path to really put "pop" on the ball.
Putting it all together with the right mechanics will be a challenge for them not only this tennis season, but beyond. But at least you'll have pointed them in the right direction.
Don't underestimate your students penchant for learning from video. (My daughter's fifth grade basketball coach gave them all a video cd of plays/defenses; it was amazing to see the result.) You potentially could forward to them any of the video links above you might think appropriate.
Good luck, coach!
