When it comes to an athlete, the first

When
it comes to an athlete, the first thing that comes to a mind is his
performance. It usually being determined by two key factors: rate of force
development, ability to exert a big amount of force during short period of
time, and peak force, absolute maximum amount of force that can be generated.
The perspective through which an athlete is being evaluated specifically
depends on activities that he is involved for example, explosive sprinting or
vertical jumping. Therefore, there
are ongoing debates whether (RFD) is better predictor of an athlete’s
performance compared to (PF). For instance, Weyand et al. 2000, found that rate
of force that is applied to the ground during sprinting is related to how fast
an athlete can run. In addition, Young W.B. 2014, findings also supported Weyand
et al. 2000, results, stating that greater RFD is more important for a faster
running, while PF is more important at the starting phase of sprint. Other
studies also support statement that athletes who are stronger and produce force
faster achieve better results in explosive activity, where peak force didn’t
show significant difference (Dowling J.J & Vamos L. 1993, Tricoli et al.
2005, Kraska et al. 2009, Campillo et al. 2013, Marques et al. 2011). In
contrast, Kawamori et al. 2006, in his case study find out significant
relationship between (PF) and jump height, stating that peak force can be used
to assess athlete’s performance using maximal muscle strength. On the other
hand, West et al. 2011 in his recent study with professional league players
found out that both RFD and PF had significant correlation with sprinting time
and counter movement jump (CMJ) which leads to uncertainty which predictor is
more accurate and reliable.  

Thus,
the aim of this study was to figure out whether rate of force development (RFD)
is a better predictor of performance compared to peak force (PF). It was
hypothesized that (RFD) will be directly related to a greater performance in
sprint, squat jump (SJ) and counter movement jump (CMJ).

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Methods

Experimental
Approach to the Problem

The
main purpose of this study was to investigate (RFD) as a potential predictor of
better performance in athletes. To figure this out four different tests were
selected, who were thought to be most suitable for this research and met all
criteria: easy to access, easy to conduct and are safe. Pearson’s correlation
was used to process data. In this study
participated Middlesex university students with no or little experience in
athletics.

Subjects

Testing
group consisted of twenty Middlesex students (N=20) males – 18 and females – 2
of age (20.5 ± 1.7), weight (107.7 ± 89.0) and height (75.6 ±
13.2). All participants were physical active and were not taking any
supplements at that time, also diet was not considered in testing results. None
of participants had any injuries in past 3 years and were fully able to perform
all test without pain or discomfort. Every participant was informed with
protocols of testing and were taught how to correctly perform each task to get
optimal results. All testing subjects were asked to perform each test three
times, and only maximal vales were taken in this study. During test none of
students reported any pain or discomfort. However, out of 20 participant’s
data, 3 were not readable, therefore couldn’t be assessed. Final number of
subjects were seventeen (n=17) of which males = 15 and females = 2 with results
appropriate for analyzing.

Tests

All
tests were conducted within a period of one day in such an order (CMJ), (SJ),
isometric squat and 20m sprint with at least 4min. rest in between each attempt
(3 repetitions in total) and 10min. break in between each test.  

Countermovement
jump

To get power of lower body
extremities subjects performed countermovement jump on stationary force plate
in the laboratory. Each participant was informed to keep his/her hands-on hips
throughout entire move (acceleration and landing phase) and dip to their
desired depth followed by concentric phase without any break at the lowest
point of squat to reach maximal jump height based on their bodyweight.

Squat
jump

Another lower body test was
conducted in form of squat jump. Desired value of this test was also the same
as from the countermovement jump maximal jump height. Participants had to stand
on a force plate with hands on the hips. Then they were asked to squat into 90°-degree
knee flexion position with straight back looking forward and hold it for three
seconds after which had to perform upward acceleration to reach maximal jump
height. Subjects were asked to keep their hands all the time on the hips to get
most accurate readings and equalize everyone conditions.

Reactive
Force Development and Peak Force

Isometric squat in a fixed
rack on a force plate was conducted to find maximal (RFD) and (PF) of each
subject. Bar was fixed at around chest height for every participant separately,
so that knees would be at approximately 45°-degree flexion. Grip of the bar was
set to be around slightly wider that shoulder width, legs were shoulder width
apart with a slight turn outwards. Subjects had to get into squat position and
apply gentle force to the bar prior performing isometric squat, after three
seconds subjects were told to perform maximal push upwards, as they would do
during squat, and hold it for as long as possible to get the most accurate
readings. All data was recorded with (BioWare) program on a laptop.

Sprint
time

To collect sprinting time
participants were asked to perform 20m sprints for 3 times in total at 100% of
their effort.  At the start point were
placed two timing gates and 20 meters away from them were placed finish line
timing gates to record full sprint time. Subjects were tested in indoor track,
so no weather conditions would affect test results.

Analysis

To analyze collected data for
this study, were used 2016 Microsoft Excel and Statistical Package for the Social
Sciences (SPSS) programs.

Results

Results
got from Pearson’s correlation has showed that neither peak force or reactive
force development is a good performance predictor in this case, as they both
didn’t show any significant differences between CMJ, SJ and sprinting time in all
subjects (p>0.05).

RFD has showed no significant relationship
(p>0.05)   with countermovement jump height (r=0.726) (Table
1.)

 There was no significant difference (p>0.05)
between subjects’ RFD and sprinting time (r=0.801) (Table 1).

Also, there was no significant
difference found (p>0.05) in RFD relationship with a squat jump (r=0.941) (Table
1).

No significant relationship
(p>0.05) was found between peak force of subjects and CMJ (r=0.656) (Table
2).

Peak force didn’t show any
significant difference (p>0.05) in participants’ 20m sprint time (r=0.475)
(Table 2).

No significant difference (p>0.05)
was observed   between   PF and SJ (r=0.412) (Table 2).

However,
two
significant differences (p0.05) being
found in both predictors compared to sprint times, countermovement jumps and
squat jumps among all subjects. This can be due to subjects insufficient training
experience or unclear presented instructions how to perform each test individually
and further or repetitive research is required. Moreover, these results, contradicts
with other findings (West et al. 2011, Tricoli et al. 2005, Hori et al. 2011), which
show great RFD influence as valuable predictor on explosive movements. Also, this
study shows that neither one of both values can be used as reliable predictors
to evaluate athlete’s performance.     The main reason for that could be
nonsufficient quality of data that was observed during testing period.

Non-significant
difference (p>0.05) between reactive force development and all measures indicates
that the amount of force that is being transferred to the ground in a short time
period is not enough to predict athlete’s performance, whilst in other studies were
found that RFD is one single best predictor when it comes to an explosive movement
(West et al. 2011, Tricoli et al. 2005, Comfort P. 2011, Andersen L.L & Aagaard
P. 2006, Moir et al. 2004) Thus, these findings deny theoretical approach to
RFD, as it states that the more power is being produced over short time the
greater the outcome is which should appear in an increase in sprint speed, as more
power is being produced though out each stride and less time is being spent on
the ground (Marques et al. 2011, Weyand et al. 2000). Furthermore, no
significant differences (p>0.05) were observed between RFD and squat jump or
countermovement jump in all subjects, which leads to a possible conclusion that
testing were performed not in a right manner and should be repeated with right
instructions and maximal effort. In addition, there were no significant relationship
(p>0.05) found between peak force and other variables, supporting other
research findings that PF is not that important for a performance prediction as
it is being generated over prolonged period of time and almost every explosive
movement requires high force production as fast as possible.   

In
conclusion, the main purpose of this study was to investigate if reactive force
development can be described as a better performance predictor when it comes to
an athlete. However, results of present study showed no significant difference
in any value, denying other findings, that proved RFD importance in performance
evaluation. Thus, present study can be validated as lacking quality data and further
research might be necessary to complement or refuse recent study.

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