🎾 17 - Your Body’s Sức Mạnh¶
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17 - Your Body’s Sức Mạnh — tài liệu 8 trang từ thư viện sách tennis.
Chủ đề chính: Power
Tóm tắt nội dung (trích từ tài liệu gốc): Revolutionary Tennis Tennis That Makes Sense Step 4 Your Body's Power � Mark Papas mark@revolutionarytennis.com To step or not to step into the ball, that is the question. Does your body empower you more when you move into and step into the ball, or when you remain in an open stance? Or when you throw the back leg around from an open stance? Well, try pushing someone away from you, or throwing a ball, without stepping into what you're doing. The answer is clear: move, take that step. How about accuracy? Ever throw a ball while aggressively swinging your back leg around? You have no accuracy. P
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Revolutionary Tennis
Tennis That Makes Sense
Step 4
Your Body's Power
� Mark Papas
mark@revolutionarytennis.com
To step or not to step into the ball, that is the question.
Does your body empower you more when you move into and step into the ball, or when you
remain in an open stance? Or when you throw the back leg around from an open stance? Well,
try pushing someone away from you, or throwing a ball, without stepping into what you're doing.
The answer is clear: move, take that step. How about accuracy? Ever throw a ball while
aggressively swinging your back leg around? You have no accuracy.
Power means shifting body weight. The weight is shifted, creating momentum, into your body's
power zone to empower your arms or legs. There's acceleration with the striking mechanism
(hand. leg, bat) for more pop, but it's the weight shift that counts.
You can shift your weight in a variety of ways, and instinctively tennis players are always trying to
shift more weight into the ball. But what we want is a system that gets the most bang for the
buck and can be repeated easily. All athletes are trying to achieve power with the least amount of
energy expenditure possible because overdoing things leads to injuries and inconsistent results.
Two terms used for momentum: linear and angular. I know biomechanists would add minutiae to
my descriptions, but I want to keep it simple. It's angular momentum when the body rotates the
torso and/or hips, like a golfer or baseball batter during a swing, and it's linear momentum when
the body shifts straight without rotation, like moving straight into someone and pushing them
away from you.
Every tennis manual asks you to rotate your body for power like a baseball batter or golfer when
swinging, but consider this:
WHY DO YOU HAVE SO MUCH POWER HITTING ON-THE-RUN
MOVING FORWARD INTO THE COURT
WHEN YOU HAVE NOT ROTATED ANYTHING AT ALL?
You know the example I'm talking about. The ball's short, you're forced to run forward, you hit
while moving (on-the-run), and at times you have too much power. Absent rotation, what's
going on?
You're using linear momentum from the body for power when hitting on-the-run, not angular
momentum, AND it's being directed solely into the ball and not along the ball's flight line toward
the opponent.. (The swing is angular, yes, because it goes around, due to the arm.) By following
Steps 1 and 2, your momentum moves into the ball. Linear momentum shifts weight in a straight
line, and believe me, it's enough of a power supply for you or any other tennis player.
I know what you're thinking, this is crazy, but I'm not advocating hitting groundstrokes
on-the-run. I'm arguing what's right for tennis based on the game's point of view, and the body's
point of view. Let's compare tennis with golf and baseball to see if we're talking apples and
apples, or apples and oranges.
TENNIS GOLF BASEBALL
the ball angles away lies still thrown at you
the player moves to the ball stands still stays in a box
and back
1 point is many hits is one hit may hit once after
series of tries
playing area 39 feet long, 26 feet wide hundreds of hundreds of feet
and begins up to 39 yards away, long and wide
feet away from you 10's yards wide
Tennis demands movement into a ball and stroke repetition, all within a small playing field.
Except for the hand-eye coordination, a golfer or baseball batter's body technique during the
swing is of no use for a tennis player because their realities are much different. Body rotation for
power is required when the player does not or can not move, moves very little, or the field is
large. It's clearly apples and oranges when comparing tennis with golf and baseball.
Steps 1 and 2 describe moving INTO the ball with 4 steps on groundstrokes. When you move
INTO the ball your linear momentum is also directed INTO the ball, they go hand in hand.
Movement equals power. Movement into the ball automatically places the contact between
identical feet, Step 3, and delivers power into the ball (4A, 4B) without the need for
compensatory technique.
LINEAR MOMENTUM "INJECTS" POWER ON A STRAIGHT LINE
The back foot doesn't stay flat on the ground, it goes up on its toe when you shift into the ball.
You already know how to do this. Get up and walk s-l-o-w-l-y. Notice how your weight goes
� Mark Papas Step4 p.2 /8
from one foot to the next, and how each foot moves heel to toe. The back heel lifts, leaving only
the toes touching the floor when shifting onto the front foot.
On the tennis court keep moving into the ball to shift the weight into the ball. Don't hesitate,
pause, or pull back. I know that sounds obvious, but imagine you want to kick a soccer ball back
down field and you're told to run toward the sidelines, get "in position," and then kick it. Or
you're told to run up to it, turn, shift your weight back away from the ball, and then kick. These
two examples represent the standard advice on weight shifting for tennis players. Less is more.
WHY NOT BODY ROTATION?
Body rotation is designed to shift weight if you're not moving into the object to begin with, or if
you're standing still prior to contact. But a tennis player gets to move, and should take advantage
of this huge benefit by moving into the ball instead of to the side fence.
Body rotation by definition means the body rotates inward from the
contact spot, no matter the sport. From overhead, the trajectory of a
tennis ball is a tangent line, angling away from the player, and it continues
to angle away at contact. The direction of the body's rotation here is
inward from the tangent line, inward from the contact spot (4C).
Or look at it this way. Stand and face your computer monitor. Draw an
imaginary line perpendicular to it from your navel. This line has a fixed length to it. Rotate your
body to one side and notice how your imaginary line arcs inward from the monitor.
As a tennis player you face the reality of a ball angling away from you. If you rotate your body
during the swing, this means both your racket and your body are moving away from the ball at the
same time the ball is moving away from you. �Ay caramba!
Linear momentum is an easier and more reliable source of power than angular momentum. Its
mathematical equation is simpler as well. When a tennis player rotates, it's overkill,
counterproductive, and everything gets more complicated. What happens when a golfer or batter
tries to hit the ball harder? They rotate more, and their accuracy suffers.
LINEAR BODY WEIGHT SHIFT
The length to the linear shifting of your body weight is small.
This is the main advantage, there is very little "shifting" to do
since you've been moving into the ball. The tennis balls placed
below the center of my body in photo 4D represent this length,
and the arrow shows the direction of the shift. Aggressive
players will add more length to this shift by taking a longer
stride.
Let me show the direction in which your weight shift should
proceed. 4E shows the difference between shifting your weight
forward into the ball, or shifting it "forward" toward the
opponent in the direction of your stroke, which isn't forward
� Mark Papas Step4 p.3 /8
into the ball. You shift into the ball, and there is only one direction for that.
If you're like most players, often your momentum has
been going to the side fence. You're sideways, and to
compensate you'll rotate your body to redirect your
momentum more into the ball. Unavoidably, this
rotation adversely impacts your stroke.
Or, you'll rotate your body to generate momentum
from an open stance because you've stopped moving,
you won't step into the ball. Ironically, this momentum
from rotation will not go into the ball but away from it,
the largest single source of unforced forehand errors in the pros. On a replay after the pro has
netted an easy forehand, notice how severely he or she rotated the body inward from the contact
spot toward the opponent's side of the court, that is away from the ball.
I know the idea of no body rotation is different. It runs counter to the established method. Well,
if you move into the ball correctly with both feet, step into it with the front foot, shift your weight
linearly into the ball, and don't rotate the body during the swing, you'll be amazed at how strong
your contact is with linear momentum as a power source. Large muscle groups are still
responsible for transferring weight, only now their contribution is linear, not rotational. This is a
new idea. Revolutionary.
LESS IS MORE, SIMPLE IS BEST
Let's talk about turning the body, because I
know the popular idea is to "turn" the body
when you take the racket back. First,
when you move you automatically turn the
hips and shoulders, it doesn't work the
other way around, shown in diagram 4F.
Movement = turning, as illustrated when
hitting on-the-run forward into the court.
Very few students move across the court
with their shoulders parallel to the net.
Second, if you turn first, you've turned
the body and its momentum away from
the ball. With this over-turn, you'll have
to re-turn the body into the ball to
support the stroke at contact. All of
that adjustment, especially in such a
short amount of time, adversely impacts
any swing. Compensatory technique
should not be offered as a model.
Third, and last, what about the popular
idea of turning the upper body a lot
� Mark Papas Step4 p.4 /8
first, winding it up, to accelerate the stroke more via rotation? Step 6 elaborates on why this
doesn't work, but for here let me refer you to diagram 4G. As long as your hips and feet (your
body center) lead you into the ball there will be a limit on upper body rotation, or wind up. If,
however, you allow your hips (body center) to turn more because the upper body winds up, you'll
find yourself and your momentum no longer moving into the ball but away from it. Your stroke
then needs more time to curve its way around to line up into the ball, and, more importantly,
hitting on time becomes more difficult to achieve (more on this in Step 7).
FOR ADVANCED PLAYERS...and those who aspire to be
I have received a lot of feedback regarding upper body rotation on a forehand. For advanced
players the answer is yes, there is some, if you want to call it rotation. But when I asked a
student of mine who's an attorney whether or not she considered what follows to be rotation, she
answered, "Not really, because I'm trying to lock my torso after a point." Let me explain. What
follows also applies to two handed backhands.
Diagram 4H begins, like 4G before, showing the limit to the upper body's coiling, or turning,
while moving forward into the ball. Next, during the forward swing, the torso re-turns to match
the angle of the hips beneath it, something it wants to do quite naturally. And if the torso stops
when it matches that angle it acts as a boost to get the racket going. By stopping its limited
rotary movement, the torso helps accelerate the racket ON ITS OWN. This is similar to
cracking a whip, where the handle stops and the rest of the whip accelerates and continues
beyond it, or similar to a hammer throw, where the body prior to release stops its rotary
movement to help the arms accelerate the throw.
The stroke does not accelerate as much as explained above if the shoulders continue to rotate
(and the hips) in the direction of the swing and wind up facing the net. There is a point in tennis
where rotary movement becomes counterproductive to stroke speed and contact control, a point
easily breached when either hips or shoulders rotate to face the net in an effort to accelerate the
swing. Tennis is not golf or baseball. We need to move, adjust our stride and closeness to the
ball, adjust the stroke, exercise more control over the hit, keep it in a small playing area, and get
ready to do it again a few more times for one point.
� Mark Papas Step4 p.5 /8
I'm including a photo here of the great Stan
Smith to illustrate the movement in 4H. Stan's
explaining something about hitting down the line
with these two photos, but a few things
prominent to Revolutionary Tennis stand out
even though these aren't mentioned in the article.
It's clear that 2 steps are taken prior to contact
and that both feet are identical, or pointing into
the ball (Step 2). Stan's shoulders are turned
more than his lower body (photo left), and then his shoulders re-turn to match the hipline (right)
per diagram 4H. His contact spot lies between the width of his feet (Step 3), and his overall
posture is good (Step 5). This photo by Fred Mullane appeared in Tennis magazine.
How can you learn the movement described in 4H? First, move into the ball and don't coil the
upper body as you begin taking the racket back. Your torso will be turned slightly like your
lower body. Then step into the ball with the front foot, shift your weight linearly, and swing
without moving your torso or hips. A common teaching tool is to to freeze after contact, that is
follow through and freeze. The "freeze" stops body rotation and produces a strong hit.
As a teacher I find students naturally turn the torso slightly on the forehand when taking the
racket back, and they naturally overrotate the shoulders forward with the swing. I guess you
can't have everything. So my job is to get them to stop that forward overrotation to improve their
stroke.
Some players hit successfully after both moving parallel to the baseline and rotating the body.
This is good enough, from time to time, but it's harder to make this style consistent because
rotation compensates for not lining up properly INTO the ball to begin with. When faced with a
harder or wider ball, the weakness in this style is exposed. Furthermore, this kind of player would
like to have more power yet keep the ball in. How to? Cut down on the rotation, and try moving
into the ball to begin with.
Contact, for any sport, is preceded by shifting body weight into the contact area, you shift and hit.
For tennis players it has been said that the timing of the rotation of the body (body weight shift)
with the swinging of a racket onto the ball is crucial for success. Wrong sport. Tennis players
need not rotate like golfers or baseball batters. Nor should they. And if your power isn't what
you want even though you're moving into the ball and using linear momentum for your weight
transfer, Step 5 will assist you.
Using a metaphor, the perfect swing works as smoothly as a child's swing swinging back and forth
between the legs of a swing set. But if Mr. Bully picked up the legs of the swing set and twisted
them, the swing would no longer move smoothly, it would fly off to the side. This is what
happens when you rotate the body while swinging the racket, the racket can't line up into the ball
smoothly.
CHILDREN AND JUNIORS
Promising young tennis players jump and rotate their bodies dramatically because they want to hit
the ball hard. Force is a product of mass times acceleration. Young kids don't weigh very much
� Mark Papas Step4 p.6 /8
and aren't very strong, so they throw every bit of mass they've got at the ball to get more zip. As
they get older they will naturally hit harder due to weight gain and increased physical strength but
their jumping and twisting motions will prove counterproductive in adulthood.
Power and strength develop naturally as children grow older. Since rotation is anathema to
success for an adult tennis player, children shouldn't nourish a set of skills that will hurt them in
later years. It doesn't make sense, but it happens all too frequently.
This photo, by Red Morgan, from I believe Tennis
Week, is worth more than a thousand words, but
I'll try to be brief. The well intentioned teacher
has the boy standing still and sideways, and will
drop the ball for the boy to hit. The boy learns to
wind up a lot to hit with power precisely because
he is standing still, in effect becoming a baseball
batter. But tennis isn't baseball where you get to
stand still waiting for the ball, the boy needs to
learn (how) to move into the ball and balance, or
reconcile, that action with his stroke and not the
other way around. You can say the teacher is trying to work solely on the boy's swing and that
I'm being too critical, but this teaching method is very common: both feet are sideways, the wind
up is large, the ball is dropped by the boy's side, and the front foot will step toward the net instead
of into the ball. Extremely unrealistic.
What would I do here instead? Let me refer you to the Stan
Smith photo above where he's taking 2 steps forward into
the ball and both feet point identically into the ball. Or look
at the young girl in the black and white photo on the left by
Russ Adams. Her feet are pointing correctly, she's not
standing sideways. Children do so many things naturally,
don't they?
I would ask the young boy to start taking his racket back as
a loop (explained more fully in Step 8 part II, How To Help
Your Forehand). I would drop the ball ahead and in front of
him (in the direction of the net post to the boy's right), and I
would ask him to take 2 steps forward into the ball before
striking it. In this way the young boy would absorb all the
elements to improve his game: stroke preparation, 2 step minimum forward movement, stroking
with the body's momentum behind it.
Juniors wonder why their mechanics fail them, and they are told inaccuracy can be overcome by
quality practice. That is practicing how to turn sideways, rotate, shuffle step... The standard
technique lets us all down.
It's very easy to get kids to move into the ball and hit well without rotation. But it's hard for them
to see they're establishing a foundation, like roots on a tree, that will allow their game to grow
unencumbered by compensatory technique.
� Mark Papas Step4 p.7 /8
You can do Steps 1, 2, 3, and 4 correctly and still not maximize your power. That's where Step
5, Strength & Stability, comes into the picture.
OLD THINK NEW THINK
� angular momentum � linear momentum
� rotate hips/shoulders during contact � shift straight into the ball/contact
� shift weight with ball toward opponent's side
� Mark Papas Step4 p.8 /8