|
Track & Field and Athletics: #1 Sports site with latest training info for coaches and self-coached athletes
|
|
High Jump Abstracts
Searching for the best straddle technique
Dapena, J. -- Track Technique, Los Altos, CA (March 1974),55, pp. 1753-1756
When a straddle high jumper reaches the bar he must have
a basic rotation obtained during the takeoff. Without this basic rotation it is
impossible for the jumper to do a normal bar clearance. The acquisition of this
basic rotation is done at the expense of a loss in the height that the center of
gravity (c. g.) of the jumper will reach. So, the basic rotation acquired at
takeoff must be as small as possible in order to make the c. g. reach the
greatest height. After takeoff, the parabola to be followed by the c. g. is
fixed, and the angular momentum of the body remains constant. They cannot be
changed until the athlete touches the ground again. Still, the athlete can move
with a certain freedom after takeoff:
1) He can lower some part of his body. As his c. g. cannot change its parabola, some other part of the body will have to go up as a compensation.
2) He can make some part of his body rotate slower than the rest. As his total angular momentum cannot be changed in mid-air, some other part of the body must rotate faster as a compensation.
3) By altering the position of his limbs, he can change the moment of inertia about his axis of rotation and therefore turn at different speeds. The better the jumper uses these movements, the less basic rotation he will need in order to clear the bar. Thus, he will be able to elevate his c. g. more.
The high jump takeoff mechanism
Ozolin, N. -- Track Technique, Los Altos, CA (1973), 52, pp. 1668-1671
The support phase of the takeoff is the means by which
the horizontal speed built up in the run-up is transposed into vertical speed.
The horizontal speed is not smoothly transformed into vertical speed. Instead,
another mechanism acts the energy amassed during the run-up is absorbed in the
pushoff and is used at that time to get a very active takeoff. As the supporting
leg bends, the straining muscles stretch out, and powerful contracting forces
arise in them. The "explosion" occurs at the moment when the pressure on the
support eases. This moment is related to the motion of the swinging leg. During
the support phase only a small part of the horizontal speed is left to be used
for going over the bar.
There are only two ways to increase takeoff effectiveness. Both ways require an increase of horizontal speed in the run-up, in order to impart greater energy into the takeoff leg. In the first variant, the legs must be placed further forward and the angle of body lean must be increased. This puts a much greater load on the muscles of the support leg and may require a greater load on the muscles and a greater bending of this leg. The muscles have to be very strong in order to complete a takeoff effectively from such a position. It is natural, in this case, for the support leg to last longer. The second variant seems to be more promising. In this method the fast horizontal speed must provide a powerful charge of kinetic energy to the support leg and must enable the jumper to use this energy in the shortest possible time and with optimum effect. To do this the foot must not be as far forward, the body lean must be less, the support leg less bent and the support, or takeoff, phase must take less time. To some degree, the second variant already exists. It is the Fosbury flop. In record jumps the time used for the takeoff was 0.17-0.18 sec for Brumel, but only 0.12-0.13 sec for the Fosbury flop.
The plant and takeoff in the Fosbury flop
Santos, J. -- Track and Field Quarterly Review, Kalamazoo, MI., 79 (1979), 1,
pp. 48-49
The key to successful jumping by using the flop as a
technique is not bar clearance in itself, and the technique involved, but rather
the key is how high can the jumper raise his center of mass. A jumper can have a
bar clearance technique that is perfect in regards to mechanical features in the
jump, but if he can only raise his center of mass to a height of 6-10, he may
remain strictly a 6-10 jumper. Raising the center of mass as high as possible
over the bar therefore is the most important factor in high jumping, and
practice sessions and training sessions should be devoted greatly to this task.
It is for this reason that at least 80-90% of the coaching and training should
be devoted to the approach, the plant and the takeoff in the flop, rather than
spend time on bar clearance technique as a major portion of the training
sessions.
Why use a curved approach to the flop high jumping style?
Paolillo, B. -- Modern Athlete and Coach, Adelaide, 27 (1989), 1, pp. 19-20;
also in: Athletics Coach, Birmingham (England) 23 (June 1989),2, pp. 27-28;
Track and Field Coaches Review, Gainesville, FL., 97 (1997),2, p. 25
The purpose of the approach in any high jumping style is
to assist the athlete in clearing the crossbar. A straight line approach is
obviously faster than one that is curved. The problem in the flop bar clearance
is somehow to get the jumper's body into a horizontal position at the instant of
bar clearance. Let us assume the athlete is leaning away from the bar at the
instant the takeoff foot is planted. As the athlete executes the takeoff motions
bent free leg, knee driving upward slightly toward the far upright, simultaneous
single or double arm action and extension of the takeoff leg the athlete rotates
toward the bar along an axis on the ground, which passes through his/her takeoff
foot parallel to the crossbar. At the instant the athlete's body becomes
vertical, he/she leaves the ground. This rotation about the axis on the ground
transfers to rotation about an axis, which passes through the athlete's center
of gravity at the instant he/she breaks ground contact. Thus, the rotation that
originated on the ground during takeoff becomes the angular (turning) force that
turns the body from vertical to horizontal for an efficient bar clearance.
How the free limbs are used by elite high jumpers in generating vertical velocity
Lees, A; Rojas, J; Cepero, M.; Soto, V.; Gutierrez, M. -- Ergonomics,
London, 43 (2000), 70, pp. 1622- 1636
The aim of this study was to quantify how elite high
jumpers use their free limbs in a competitive high jump and to estimate the
contribution that these made to vertical take-off velocity. This was achieved by
analyzing the competitive performances of six elite male high jumpers using 3D
motion analysis and assessing limb function using the relative momentum method.
The mean peak relative momentum of the arm nearest to the bar at take-off was
9.4 kg/mis, while that of the arm furthest away from the bar was 11.3 kg/m/s and
these did not differ significantly. The free (lead) leg reached a mean peak
relative momentum of 20.9 kg/m/s. At touch-down the free leg had a large
positive relative momentum that was offset by the negative relative momentum of
the arms, although their combined value still remained positive. The mean
combined free limbs' relative momentum at touch-down was 13.8 kg/m/s and reached
a peak of 37.6 kg/m/s. The difference between these two values amounted to 7.1%
of whole-body momentum, which was judged to be the amount by which the free
limbs contributed to performance. The arms had a greater influence on
performance than had the lead leg. This was because the lead leg increased its
relative momentum little during the contact period while the arms had an initial
negative value that increased markedly after touch-down. The compressive force
exerted by the motion of the free limbs, estimated by the change in the combined
free limbs' relative momentum, reached a mean peak of 366 N and was greatest at
37% of the contact period.
It was concluded that to maximize the contribution the free limbs can make to
performance, given the restraints imposed on technique by other performance
requirements, the arms should have a vigorous downward motion at touchdown to
make the most use of the high (but little changing) relative momentum of the
lead leg.
High jump: technical aspects
Patrick. S. -- Track Coach, Mountain View, CA (Spring 2001), 155, pp. 4938-4940
The high jump is a technical event. While most jumpers
feel that the bar clearance is the most important aspect of high jumping, it is
not. Just as with the other three jumping events (LJ, TJ, and PV), the run-up or
approach is probably the most important aspect of the event. In fact when you
look at good junior high jumpers, they often have perfect (or near-perfect] bar
clearance technique. What they lack, however, is a perfect approach run. The
main concept with an approach run is to develop a lot of horizontal velocity,
directly towards the pit. A sharp, curving turn at the end of the approach run
creates rotation, allowing the athlete to jump with his back to the bar.
Horizontal velocity provides for two things:
(1) Translation of increased horizontal velocity into vertical velocity results in greater jumping heights.
(2) The greater the horizontal velocity, the farther away an individual can take off, allowing for a more gradual takeoff angle.
This is also advantageous because it provides the athlete with more time to
reach peak height. Although the high jump approach run shares many
characteristics with the approach runs of the other jumping events it is unique
in that it curves. If the athlete has performed the approach run and takeoff
correctly, there will be little problem with bar clearance. Much more crucial is
the takeoff, which should be short and quick. The lead leg should be raised very
quickly and should "block" once the thigh is parallel to the ground. It is
important that the lead leg block while the jumping leg is still in contact with
the ground. The arms should swing forward and upward and should also block while
the jumping leg is still in contact with the ground. Since every action causes
an equal but opposite reaction, this blocking will increase the "push" of the
jumping leg off the ground. The athlete should attempt to jump straight up, and
not towards the bar his horizontal velocity and the rotation started by the lean
into the turn will cause him to head over the bar.
Related Articles:
High Jump: The Straddle and the Flop
ROTATION OVER THE BAR IN THE FOSBURY-FLOP
More Articles via RSS:
.