Improving the hamstrings, quadriceps, and calf muscles are key

Improving Strength for Vertical
Jumps

According to Woodrup (2017), nearly all your athletic
performance qualities (speed, jump, agility, etc) depend on your base levels of
strength. So, how strong you are drives how well you can run, jump, cut, throw,
tackle etc. When a vertical jump is performed, force is exerted predominantly
from the hip, knee, ankle and lower back. Many models have been constructed to
identify the most important muscles in the vertical jump, with some conflicting
results. Some have suggested that movement is governed by the gluteus maximus
and quadriceps, while others have proposed that the hamstrings, quadriceps, and
calf muscles are key (Beardsley, 2017). Many studies have been conducted to
determine which exercise is optimal for improving maximum vertical jump height,
with many believing the squat or squat variations (squat jump) is as close as
we can get. Olympic barbell deadlifts provide somewhat of the same movement as
a vertical jump, however the centre of mass is in front of the body, which
would imply that it is not an ideal movement to attain maximal vertical jump
height. It is thought by many, that the trap bar deadlift is the most efficient
and useful exercise, as the centre of mass in going up from the heels, straight
through the centre of the body, as it is in the vertical jump. That being said,
with both the squat and squat jump having the centre of mass in a different
place than when performing a vertical jump, it is still unclear what exercise
is most effective for maximal performance.

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There are different elements of strength an athlete can
improve to help maximise vertical jump performance. Cavagna et al (1965)
defines reactive strength as a
concentric contraction following a rapid eccentric contraction resulting in greater
concentric force output. In other words this is being able to absorb force in
one direction and be able to generate and apply more force in the opposite
direction – which is linked with the stretch shortening cycle (SSC). Performing
exercises such as ankle hops or depth jumps is known to increase reactive
strength. Explosive strength refers to an individual’s ability to exert a
maximal amount of force in the shortest possible time interval. This directly
translates to a sprinter coming out of the blocks or an Olympic lifter at the
start of a clean. Clean and snatch variations, box squats (weighted or
unweighted) and hurdle jumps have shown to improve an individual’s explosive
strength.

Counter Movement Jump (CMJ)

The counter movement jump (CMJ) is a very practical and
reliable way to measure the explosive power output in the lower extremities
compared with other jump tests used by Strength and Conditioning professionals
(provided they use the same jump mat/equipment for each test). This test is
used in nearly every sport, as it is a great indicator of lower body explosive
power, and is easy to track and record. The CMJ has been proven to correlate
with maximal strength tests, 1RM maximal strength and maximal speed. The CMJ
can be performed with or without the use of the arm swing.

Vaverka, F. et al. (2016) found that using arm swing in the
CMJ can boost vertical jump height and ground reaction force significantly. The
CMJ is often measured using video analysis, jump mats, force plates, infrared
platforms, linear position transducers or accelerometers – some of which are
far more accurate than others.

For each of the CMJ attempts in this study, the participants
will be using the Optojump (jump mat). To perform this test, the individual
steps onto the jump mat, standing tall with hands on hips at all times, takes a
dip down – closing the angles in the hip, knee and ankle – and with a sharp
burst, explodes up into the air extending at the hip, knee and ankle, while
landing in the centre of the mat.

 

Deadlift

The deadlift is a great way to measure overall body
strength. While the majority of people normally use Olympic barbells to perform
this lift, the trap bar or hex bar deadlift is often overlooked even though the
movement is now thought to be safer to perform than its counterpart. Hex bars
have a hexagon shape with two handles at either side. The lifter stands in the
middle of the hexagon, holding both handles with the hips down and chest up.
There are two sleeves coming from the two middle points in the hexagon to hold
weight plates, ensuring the weight is in line with your body (usually the
heels), as opposed to Olympic bar where the weight is more towards the front of
the body. The hex bar deadlift has more of a neutral grip and is geared more
towards being able to load more weight on and drive through your heels to gain
maximal power while putting as little stress on the lower back as possible.

A study from The Journal of Strength and Conditioning
Research found that when performing hex bar deadlifts, subjects were able to
lift up to 50 pounds heavier than with a traditional Olympic bar. Along with
these findings, they concluded that there was less pressure on the lower back
with hex bar deadlifts as opposed to Olympic bar deadlifts.

The correlation between hex bar deadlifts and vertical jump
has been found to be very high in many studies. Young (2013) examined whether
using either a hex bar deadlift or a back squat is better for maximal lower
extremities output in the vertical jump. His subjects underwent testing pre,
during and post the seven week program. Results found that subjects using the
hex bar program gained more of a power increase in the vertical jump than with
the back squat group.

Blanchard (2015) created a study which compared the effects
of the trap bar deadlift and the leg press in adolescent male strength, power
and speed. He found that both groups improved 6-RM strength as a result of the
resistance training protocols and there was no difference between groups in
regards to strength gains.

Stretch Shortening Cycle (SSC)

During the CMJ, the SSC becomes very important and will help
the individual reach the peak of their jump. The stretch shortening cycle can
be compared to an elastic band – when the band is stretched and under more
tension, there is more force when it is let go. This happens the same way in
the SSC. When the muscle is lengthened and put under tension in an eccentric
way during the countermovement action, the stretch of the muscle provides the
individual to produce more force and move quicker throughout the concentric
phase. The same way when an elastic band is stretched out, there is stored
energy or potential energy. The amount of force used to stretch the band should
be the same as the amount of force the band used to return to its pre-stretched
state. This also work for the muscles, as we stretch, or concentrically
contract them, the amount of force should be equal to bring it back to its
normal state.

Taking the squat jump (SJ) as an example of a vertical jump
test without SSC, Van Hooran (2017) states that countermovement jump
performance is almost always better than SJ performance, and the difference in
performance is thought to reflect an effective utilisation of the
stretch-shortening cycle. The SSC has been split into two categories based on
the duration of the ground contact time in the SSC – fast SSC (under 250 milliseconds),
and slow SSC (over 250 milliseconds). The stretch shortening cycle happens very
often in every-day life. For example, hopping over a puddle will be using SSC
when we bend our knee and eccentrically contract our quads, then concentrically
contract to be able to spring up and over.

 

Strength – Jump Relationship

Research has shown the clear relationship between absolute
and relative strength in sprint and jump performances in adult athletes
(Comfort, P. et al), but not much research has been done in youth athletes. The results of Comfort’s study shows how
important it is to develop maximum lower-limb strength to enhance sprint and jump performance in youth soccer players,
with stronger athletes demonstrating superior sprint and jump performances.  There have been many studies comparing both
relative strength and absolute strength with vertical jumps (both squat jump
and countermovement jump).

Young (1999) found that reactive strength is relatively more
important for jumping from a run-up than for the standing VJ. In his study, he
concluded that speed-strength tests correlated significantly with both jump
types, but maximum strength did not. Taking into account that my project is the
relationship between a trap bar 1RM (maximal strength) and CMJ, it will be very
interesting to compare my findings with those of other studies.

 In a study from
Kraska (2009), investigating the relationship between maximum strength and
differences in jump height during weighted and unweighted (body weight) squat
jumps and countermovement jumps, found that stronger athletes jump higher and
show smaller decrements in JH with load.

Wisloff (2004) found that there is a strong correlation
between maximal strength in half squats and sprint performance and jumping
height. In this study, the maximal strength was recorded by performing half
squats. Half squats, along with box squats, are used and have been used by
elite rugby teams to measure maximal strength, and can give a good indicator to
lower limb power and strength. In Wisloff’s study, he found that maximal
strength correlates with vertical jump height and performance.

Well-trained jumpers tend to display 15-20% differences
between SJ and CMJ measures. If the difference between SJ and CMJ are small
(20%), this may indicate that jumping can be
improved by more emphasis on training the contractile elements of the muscles
(Baker, 1996).

               

The Role of Strength in Power

Both strength and power are greatly needed in most, if not
all sports. Strength and power go hand in hand, yet are not the same (although
most people think they are). Absolute strength can contribute to power, and
power can contribute (not as much as strength to power) to absolute strength,
but both characteristics are trained very differently. As you can see from the
Force Velocity Curve (FVC) below, max strength is attained by training at
90-100% of an individual’s 1RM, while power is attained by training at 30-80%.

Taking the FVC (see in Appendix) into account, we can see
that max strength is at the very top of the force axis and the very bottom of
the velocity axis. This means if an athlete is lifting a very heavy weight (max
strength), it will move very slow because of the sheer mass. As we can see peak
power somewhere in the middle of the graph, meaning that the weight being
lifted will move at a faster pace because it is not as heavy, but the force
will be a little lower than max strength.

For example in rugby, there are players who can lift an enormous
amount of weight in the gym, but are not mobile on the pitch, and on the other
scale of the spectrum, there are players who can move around the pitch all day
but get pushed around when it comes to their physical presence. This is where
the power aspect comes into play. As we see above, max strength is the total
amount of force you can make (disregarding speed), and power is how fast you
can produce the force.

For example, rugby is a very power dominant sport, and it is
only getting more powerful as the years go on. The more explosive a player can
be, the better. It does depend on position to position, but each position is
changing, and we now have centres and wingers who would have no problem playing
in the forwards. With rugby, power transfers directly for some positions –
producing explosive power to work their way through a tackle, propelling the
arm forwards to produce a hand off or how fast the prop can drive his legs and
get the second row up in a line-out. Irish provincial rugby teams have been
training lower body force production for a number of years, using Olympic lifts
such as hang snatch, hang clean as well as the box squat.

Delecluse (2012) devised a study to determine the influence
of strength training on sprint running performance. He states in his study that
strength training has a key role in sprint performance. He breaks down sprint
performance into an initial acceleration phase (0 to 10m), a phase of maximum
running speed (36 to 100m) and a transition phase in between. It is stated in
his study that the coach has to keep in mind that strength, power and speed are
inherently related to one another. In the initial acceleration phase, the hip,
knee and ankle are the main drivers of force to generate speed. Delecluse
states that different training methods are put in place to improve the power
output of the muscles used. He goes on to say that hypertrophy, movement
specific and velocity specific strength training are needed to generate
strength and power to aid the sprinter during the initial acceleration phase.

Mala (2015) explored the role of strength and power under
high intensity bouts, both weighted and unweighted. The stronger and more
powerful individuals were more equipped to handle the tasks and challenges both
with and without heavy load carriage. This can be easily transferred to a
sports stance. In many sports is it likely that an athlete will have a load
either hanging off them, on their back, or coming in from the side. This means
it is very beneficial for athletes in contact sports to have a strong strength base
and be able to convert their strength to power to gain as much stability and
explosiveness in their overall gameplay.