Description
The first attachement is going to be used to fill in the responses. The ANSWERS attachement has all the answers. Just write the paper in your own words. Add references as well. The other two attachements are articles that could help you if needed.
Unformatted Attachment Preview
Insert APA-formatted title page here
Part 1: Critical Thinking
View the following video illustrating another vertical jump test:
Athlete 1: https://www.youtube.com/watch?v=9JOcnh7aGho
Athlete 2: https://www.youtube.com/watch?v=b7oIHjGjh7A&feature=youtu.be
In paragraph form, answer the following prompts in two to four typed, double-spaced pages.
Please be sure you use numerals 1-4 to separate your answers to each prompt below.
1. Using anatomical terminology, describe the differences seen between athlete #1 and
athlete #2 at the following joints. Exact numbers are not needed, qualitative descriptions
should be used (i.e., “athlete x demonstrates greater knee flexion,” etc.)
Knee:
Hip:
Shoulder:
2. Using the sections in your textbook on Length-Tension Relationships (LTR) and StretchShortening Cycle (SSC) in Chapter 4, describe why the differences in joint angles noted
in question 1 above benefit Athlete #1. How do the LTR and SSC apply to power/force
generation? Explain using summarized and cited textbook support.
3. Using the attached peer-reviewed research article as support (Moran & Wallace, 2007),
answer the following:
a. Identify optimal knee flexion angle if the goal is maximizing vertical jump
performance.
b. Does the ideal joint angle range appear to align with what you see in the two
athlete examples above? Describe similarities and differences.
c. With the above information in mind, what coaching cue(s) might you give to
Athlete #2 to help increase performance? *cue(s) should be simple, short phrases or words that would
direct the athlete towards technique improvement (example: “chest up”)
4. Using the attached peer-reviewed research article as support (Hara et al., 2006), describe
the mechanisms for how the use of an arm-swing assists in vertical jump performance.
References
Part 1: Critical Thinking
View the following video illustrating another vertical jump test:
Athlete 1: https://www.youtube.com/watch?v=9JOcnh7aGho
Athlete 2: https://www.youtube.com/watch?v=b7oIHjGjh7A&feature=youtu.be
In paragraph form, answer the following prompts in two to four typed, double-spaced pages.
Please be sure you use numerals 1-4 to separate your answers to each prompt below.
1. Using anatomical terminology, describe the differences seen between athlete #1 and athlete #2
at the following joints. Exact numbers are not needed, qualitative descriptions should be used
(i.e., “athlete x demonstrates greater knee exion,” etc.)
Knee: Between the two athletes, I see a couple of differences in the knees. For starters, the male
is way more athletic and demonstrates this through his knee exion in the downward phase of the
vertical jump. He is able to squat down lower and his form allows him to generate power to jump
that high. Whereas athlete 2, the female, does not generate as much power in her vertical jump
due to her knees during the downward phase turning inward.
Hip: Since the male athlete had greater knee exion, this also meant his hip exion was also
greater. Again, the male athlete was able to gain more power in his vertical jump due to his hip
exors helping him generate explosive strength. While the female athlete had little to no hip
exion, making her vertical jump less explosive.
Shoulder: During the male athlete’s upward movement, his shoulder joint exhibited abduction in
the concentric phase and shoulder exion in the eccentric phase, aiding him in achieving a high
jump. Conversely, the female athlete experienced only minimal shoulder exion during the
eccentric phase, resulting in insuf cient momentum for her jump. Athlete number 1 displayed a
more signi cant range of shoulder exion and extension compared to athlete number 2. The
video clearly showed that athlete number 2 did not fully execute arm exion throughout the
entire jump.
2. Using the sections in your textbook on Length-Tension Relationships (LTR) and StretchShortening Cycle (SSC) in Chapter 4, describe why the differences in joint angles noted in
question 1 above bene t Athlete #1. How do the LTR and SSC apply to power/force generation?
Explain using summarized and cited textbook support.
fl
fl
fl
fl
fl
fl
fl
fl
fi
fi
Athlete number 1 demonstrated a greater advantage in joint angles compared to athlete
number 2, leading to superior vertical jump performance. This advantage was attributed to
fi
fl
fl
CAP 2
multiple factors. Firstly, athlete number 1 effectively utilized arm swings and synchronized steps
to gain momentum prior to the jump. This added momentum played a crucial role in achieving a
higher jump height. Furthermore, during the eccentric portion of the jump, athlete number 1
demonstrated ideal hip and knee exion. They were able to produce and store more potential
energy by properly exing their knees and hips, which led to a stronger and more explosive
jump. Athlete number 1 also demonstrated improved body control and kinesthetic awareness,
which enabled them to assess and improve each body movement involved in the vertical jump.
This thorough examination before, during, and after the jump helped athletes perform better
overall through enhancements to their form and follow-through. To sum up (Whiting, 2018),
both the LTR and SSC generate power and force. While the SSC uses the elastic qualities of
muscles and tendons to increase power output through a quick succession of muscular activities,
the LTR highlights the signi cance of exercising within the ideal length range of muscles.
Athletes can improve their performance in a variety of sports and activities by comprehending
and applying these principles.
3. Using the attached peer-reviewed research article as support (Moran & Wallace, 2007), answer
the following:
A. Identify optimal knee exion angle if the goal is maximizing vertical jump performance.
The ideal knee exion angle to maximize vertical jump height according to Morgan &
Wallace is 70 degrees. The ndings in the article are stated; “Comparable results were also found
for work done at the knee joint from 70° of knee exion. However, from 90° of exion there was
no difference in the amount of knee work done with different magnitudes of eccentric loading”.
This suggests that the knee joint did not play a signi cant role in the observed improvement in
jump height when a wider range of motion was utilized, particularly in relation to the increased
eccentric loading. Therefore, when the knee is in 70 degrees the knee joint’s surrounding muscles
may exert their maximum force at this angle, resulting in an explosive extension during the
jump. In addition, to generate power and lift the body upward, the quadriceps, hamstrings, and
calf muscles can cooperate.
B. Does the ideal joint angle range appear to align with what you see in the two athlete examples
above? Describe similarities and differences.
My observations after watching the two videos between the male and female athlete
doing a vertical jump include that only one of the athletes was at or close to a 70-degree angle.
Athlete 1, the male, was close to the ideal joint angle range of 70-degrees. This is indicated by
how high he reached on his vertical jump. Whereas athlete 2, the female does not even reach an
angle that allowed her to achieve her best performance during the vertical jump. The difference
is that athlete 1, had great knee exion and form that allowed him to generate power to achieve
height, whereas athlete two had bad form, along with terrible knee exion not allowing her to
gain any momentum.
fl
fl
fi
fl
fl
fl
fi
fi
fl
fl
fl
C. With the above information in mind, what coaching cue(s) might you give to Athlete #2 to
help increase performance? *cue(s) should be simple, short phrases or words that would direct
the athlete towards technique improvement (example: “chest up”)
Some coaching cues I would give to athlete 2 to better her performance in a vertical jump
test include knees apart, throw your arms, and drop your hips. I believe these three cues would
better help her performance because the “knees apart” cue will remind her to go down in a full
squat motion without the knees going inward, the “throw your arms” cue will remind her to
swing fully with her arms since Hara et al., states that it is bene cial in achieving a high jump,
and lastly, “drop your hips” will help her have better hip exion also aiding in the momentum/
power during the jump. I would also give her some points to help her have greater knee exion
in order to get a strong push off the ground. In general, these cues will help with her form and
athleticism during the vertical jump test.
4. Using the attached peer-reviewed research article as support (Hara et al., 2006), describe the
mechanisms for how the use of an arm-swing assists in vertical jump performance.
fl
fi
fl
As stated by Hara et al., the arm swing has an impact on the torque, power, and work of
the lower extremities during the vertical jump. In other terms, arm swings assist in increasing the
jump height. The article reveals that the enhanced take-off velocity, enables the arms to
accumulate energy at the initial phase of the jump and subsequently transmit it to the rest of the
body as the jump progresses. As the arms swing downward and backward, they create a force
that aids in propelling the body upward during the jump. The arms act as counterbalances during
the jump, helping to maintain balance and stability. Therefore, arm swings are crucial for an
athlete to perform a good vertical jump and that is shown between the differences in arm swings
from both the female and male athletes in the above videos.
References
Hara, M., Shibayama, A., Takeshita, D., & Fukashiro, S. (2006). The effect of arm swing on
lower extremities in vertical jumping. Journal of Biomechanics, 39(13), 2503-2511. doi:10.1016/
j.jbiomech.2005.07.030
Moran, K. A., & Wallace, E. S. (2007). Eccentric loading and range of knee joint motion effects
on performance enhancement in vertical jumping. Human Movement Science, 26(6), 824- 840.
doi:10.1016/j.humov.2007.05.001
Whiting, W.C. (2018). Dynamic human anatomy (2nd ed.). Human Kinetics.
Available online at www.sciencedirect.com
Human Movement Science 26 (2007) 824–840
www.elsevier.com/locate/humov
Eccentric loading and range of knee joint motion
effects on performance enhancement
in vertical jumping
Kieran A. Moran a,*, Eric S. Wallace b
a
Sport Science and Health, Department of Health and Science, Dublin City University, Dublin 7, Ireland
b
Sport and Exercise Sciences Research Institute, University of Ulster, Newtownabbey, Co Antrim,
BT37 0QB Northern Ireland, United Kingdom
Available online 24 October 2007
Abstract
The aim of the study was to determine the effects of variations in eccentric loading and knee joint
range of motion on performance enhancement associated with the stretch–shortening cycle in vertical jumping. Seventeen male elite volleyball players performed three variations of the vertical jump
which served as the research model: the squat jump (SJ), countermovement jump (CMJ) and drop
jump from a height of 30 cm (DJ30). Knee joint angle (70! and 90! of flexion) at the commencement
of the propulsive phase for each jump type was experimentally controlled, with the trunk kept as
erect as possible. Force and motion data were recorded for each performance and used to compute
a range of kinematic and kinetic variables, including hip, knee and ankle angles, angular velocities,
work done, net joint moments and a number of temporal variables. The average of 12 trials for each
participant was used in a series of repeated measures ANOVA’s (jump · knee, a = .05). From both
knee joint angles, an increase in eccentric loading resulted in a significant increase in jump height
(DJ30 > CMJ > SJ; p < .05). These enhancements were significantly greater (p < .05) for 70! in comparison to 90! of knee flexion. From 70! of knee flexion, these enhancements were due to significant
increases in work done at all three joints; while from 90! of knee flexion, only the hip and ankle joints
appeared to contribute (p < .05). The amount of enhancement associated with employing the SSC in
jumping is dependent upon the interaction of the magnitude of eccentric loading and the range of
motion used.
" 2007 Elsevier B.V. All rights reserved.
*
Corresponding author. Tel.: +353 1 7008011; fax: +353 1 7008888.
E-mail address: [email protected] (K.A. Moran).
0167-9457/$ - see front matter " 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.humov.2007.05.001
K.A. Moran, E.S. Wallace / Human Movement Science 26 (2007) 824–840
825
PsycINFO classification: 4010; 3720
Keywords: Biomechanics; Countermovement jump; Squat jump; Drop jump; Stretch–shortening cycle
1. Introduction
In performing many sporting movements muscles contract in a stretch–shortening cycle
(SSC) sequence, whereby the concentric contraction phase is immediately preceded by an
eccentric phase (active pre-stretch). Researchers using isolated muscle preparations (Ettema, Huijing, Van Ingen Schenau, & De Haan, 1990) and simple movements in vivo
(Bober, Putnam, & Woodworth, 1987) have shown that under a variety of muscle dynamic
conditions the mechanical work output during the concentric phase is enhanced if it is preceded by an active pre-stretch, in comparison to being preceded by rest or an isometric
contraction. This is important as success in many sport actions is determined by the magnitude of mechanical output produced during the concentric phase. Importantly, researchers using these models have found that: (1) the magnitude of enhancement in mechanical
output of the concentric phase is greater with an increase in eccentric loading (Bober et al.,
1987; Cavagna, Dusman, & Margaria, 1968); (2) the magnitude of enhancement in
mechanical output of the concentric phase is greater with an increase in the range of
stretch, provided the range of shortening is fixed (Ettema et al., 1990); but (3) the magnitude of enhancement in mechanical output of the concentric phase decreases with an
increase in the range of shortening (Bober et al., 1987; Chapman, Caldwell, & Selbie,
1985). However, it is unclear whether these results can be directly applied to multi-joint
complex movements, such as jumping, running and kicking, because complex movements
occur under constraints (i.e., task, goal and mechanical system) and in conditions (i.e.,
sub-maximal contractions and non-isokinetic joint rotations) which differ from those in
isolated muscle and simple movement studies (Van Ingen Schenau, 1989). In addition,
while points 2 and 3 above would indicate that it may be beneficial to increase the range
of motion of the stretching phase and decrease the range of motion of the shortening
phase, in many complex movements this is not possible as an increase in the joint range
of stretching tends to result in an increase in the range of shortening.
Variations of the vertical jump have been extensively used as a research model to evaluate aspects of the SSC in complex movements. Three types of jump are commonly
employed: the squat jump (SJ), the countermovement jump (CMJ) and the drop jump
(DJ) (see Fig. 1). The SJ is performed from a semi-squatting position without any preparatory flexion of the joints and therefore utilizes no eccentric loading, as evidenced by a
lack of negative mechanical work being done at any of the joints of the lower extremities.
During the CMJ eccentric loading is imposed by flexing the lower limb joints from an initial upright standing posture, prior to the propulsion phase. Increasing amounts of eccentric loading can be imposed using DJs, which involve dropping from various heights prior
to the propulsion phase.
In agreement with researchers who have examined isolated muscles and simple movements in vivo, some researchers comparing variations of the vertical jump have observed
that, at the group level, the use of a pre-stretch results in an enhancement in task performance (jump height) (Anderson & Pandy, 1993; Bobbert, Gerritsen, Litjens, & Van Soest,
826
K.A. Moran, E.S. Wallace / Human Movement Science 26 (2007) 824–840
DJ30
4
2
1
VGRF (x bw)
3
CMJ
4
2
1
SJ
VGRF (x bw)
3
4
2
1
VGRF (x bw)
3
Fig. 1. Illustration of the depth jump (DJ30), countermovement jump (CMJ) and static jump (SJ), and their
associated vertical ground reaction force (VGRF).
1996; Voigt, Simonsen, Dyhre-Poulsen, & Klausen, 1995) and global kinetic measures
(such as work done and average force and power) (Cavagna, Komarek, Citterio, & Margaria, 1971; Fukashiro & Komi, 1987) of the CMJ in comparison to the SJ. However, in
direct contrast to findings from isolated muscle preparations, the use of a greater magnitude of eccentric loading, as employed in the DJ in comparison to the CMJ or SJ, does not
generally result in a significant increase in jump height (Bobbert, Huijing, & Van Ingen
Schenau, 1987b; Voigt et al., 1995).
These diverse and at times contrasting results may be due in part to the range of joint
motion afforded by the different eccentric loading conditions. Indeed, the range of hip and
knee joint rotation, and vertical translation of the body’s center of mass, have been found
to be greatest in the CMJ, then in the DJ and least in the SJ (Bobbert et al., 1987b; Voigt
et al., 1995). This trend in joint range of motion is similar to the trend in differences in
jump height and mechanical work output between the various jump conditions. Given that
an increase in joint range of motion may facilitate the production of greater joint mechanical work and thus an increase in jump height, it is unclear what effect increases in eccentric
loading have on enhancements associated with the SSC when comparable ranges of
motion are employed. In the few studies where the joint range of motion was experimentally controlled (Anderson & Pandy, 1993; Bobbert et al., 1996), control was generally
only at the intra participant level, resulting in variations across participants. In addition,
the DJ was not compared to the SJ or the CMJ in either of these studies.
The lack of experimental control of joint range of motion in the vast majority of these
previous studies also means that there is a deficit in our understanding of the effect of joint
range of motion itself on enhancement associated with employing the SSC in complex
K.A. Moran, E.S. Wallace / Human Movement Science 26 (2007) 824–840
827
movements. It is not only necessary to examine the relationship between SSC functioning
and range on motion to increase our understanding of neuromuscular mechanics from a
basic science perspective, but also from an applied perspective. Given that the SSC and
joint range of motion are key factors considered by biomechanists, movement specialists
and coaches in evaluating and correcting movement effectiveness (Lees, 2002), their interrelationship requires investigation.
The aims of the present study were (i) to determine if the magnitude of eccentric load
affected jump height and the underlying joint biomechanics, when joint range of motion
was experimentally controlled and matched across jump conditions; and (ii) to investigate
if joint range of motion affected the magnitude of any observed enhancement. It was
hypothesized that increases in eccentric loading would enhance jump height and that
the enhancement would be greater when the range of motion was smaller.
2. Methods and experimental protocol
2.1. Participants and outline of experimental procedures
Seventeen male elite volleyball players (mean ± SD: age 25 ± 4 years, body mass
81.1 ± 7.1 kg and height 1.81 ± 0.15 m) with at least 2 years experience at the top divisional standard in Ireland volunteered to participate in the study. These highly trained
participants, experienced in vertical jumping including drop jumps, were chosen to attenuate any possible learning effects associated with the testing and to facilitate maximum
benefits associated with the SSC. All participants were free from injury at the time of testing and provided written informed consent in accordance with the research policy statement of the University.
Participants performed three distinct variations of the vertical jump in a randomized
order: the squat jump (SJ), the countermovement jump (CMJ) and the drop jump from
a height of 30 cm (DJ30) (see Fig. 1). Each of the three jump types was performed in a
prescribed manner which dictated a maximum knee joint flexion angle (hKJF) of either
90! (±3!) or 70! (±3!) (see Fig. 2a), thereby giving a total of six jump conditions. For
the SJ, participants held the squat posture for 3 s prior to the propulsion phase. For the
CMJ and DJ30, participants were instructed to minimize the duration between the eccentric loading phase and the propulsion phase. The amount of eccentric loading was determined by examining the amount of negative work done at each joint and on the body’s
center of mass. Following training and in subsequent pilot studies, where feedback was
given immediately after each jump, these prescribed knee joint angles were shown to be
attainable by the participants in over 80% of attempts. Participants were also instructed
to minimize their trunk action and to attempt to keep it as erect as possible. While it
was recognized that it would be impossible to maintain an erect trunk inclination, the purpose was to limit as much as possible the energy gains associated with trunk action. For a
similar reason, participants placed and maintained their hands on their hips during the
jumps, to attenuate arm contributions to performance enhancement, shown to account
for as much as 15% of the work done in maximal jumping (Lees, Vanrenterghem, & De
Clercq, 2006). These experimental controls permitted an investigation of the isolated
effects of a large and a small movement range of motion associated with the two knee joint
angles imposed on each jump type at the start of the propulsion phase. In the present
paper the term range of motion of either a joint or the whole body center of mass
828
K.A. Moran, E.S. Wallace / Human Movement Science 26 (2007) 824–840
a
b
S
θHATSF
θH
H
K
θK
θKJF
A
HL
T
z
θA
x
Fig. 2. (a) Marker locations and experimentally controlled angles and (b) measured joint angles S, H, K, A, HL,
T: shoulder, hip, knee, ankle, heel and toe markers. hHATSF – HAT segment flexion; hKJF – knee joint flexion; hH,
hK and hA: hip, knee and ankle joint angles.
(WBCOM) is used to refer to the combined phases of joint flexion or lowering of the
WBCOM (comprising eccentric loading) and joint extension or raising of the WBCOM
(produced by concentric contractions), even though as in many common movement
actions, including the CMJ and DJ, the range of flexion and extension may differ slightly.
In employing this operational definition, the authors do not negate the fact that both
phases of the same vertical jump will be affected independently by the dynamics of the
SSC; however, because this is a natural occurrence and an increase in the range of flexion
(or lowering of the WBCOM) will clearly result in an increase in the range of extension (or
raising of the WBCOM), this approach seems justified. However, in referring to previous
studies using isolated muscles or simple movements in vivo that have specifically altered
only one of these phases this is explicitly stated.
Each participant initiated the drop jump by hopping off the box using two feet simultaneously and landing on the force plate with both feet simultaneously, allowing the
assumption of bilateral symmetry when calculating joint kinetics. In addition, participants
were instructed to keep their feet parallel and, in conjunction with their chest, directed
along the fore-aft axis of the force plate. Based on a sequential running mean technique
(Hamill & McNiven, 1990) in order to ensure that reliable data could be obtained for analysis, each participant performed 12 acceptable trials for each of the six jump conditions.
Jumps were selected for analysis provided they did not differ by more than 3! from the
knee angle specified by the experimental condition.
To attenuate the possibility of fatigue, at least 20 s rest between individual jumps and
2 min rest between the different jump conditions was imposed (Read & Cisar, 2006).
Instruction and practice was given on day one while the main test was administered on
day three, with day two acting as a rest day.
2.2. Data collection and processing
Five LED skin-mounted markers were attached to each participant’s right side corresponding to the following anatomical landmarks: fifth metatarsal–phalangeal (M–P) head,
lateral maleollus, lateral femoral condyle, greater trochanter, and glenohumeral joint (see
K.A. Moran, E.S. Wallace / Human Movement Science 26 (2007) 824–840
829
Fig. 2a). These markers were used to map the motion of the joint center of rotation of the
M–P, ankle, knee, hip and shoulder joints, respectively. In addition, a sixth marker was
placed on the heel, in line with the toe marker and 1 cm posterior to the ankle joint marker. The six markers defined a four-segment rigid body model, incorporating the upper
body [head, arms and trunk (HAT)], the thighs, the shanks, and the feet (see Fig. 2b).
The locations of the LED markers throughout the jumps were monitored using a CODA
mpx30 marker location system (Charndyn Dynamics Limited, England), which was calibrated according to the manufacturer’s instructions and located 0.40 m from the ground,
2.5 m from the participant and parallel to the force plate’s medio-lateral axis. A Kistler
force platform (Model 9281B; Kistler Instruments Limited, England) connected to a Kistler amplifier (Model 9863A) was used to determine the vertical and anterior–posterior
components of the ground reaction vector and point of application of force. CODA software (Charndyn Dynamics Limited, England) controlled the simultaneous sampling of
force and marker location data (400 Hz). The software also calculated the joint kinematics
employed in near real time (delay of approximately 2 s). This allowed immediate determination of whether a jump was performed from the appropriate knee joint angle and subsequently permitted acceptance or rejection from the data set. Raw force and marker
position data were filtered using a fourth-order zero-lag Butterworth digital filter (Winter,
2005). Force plate data were filtered at 70 Hz and marker position data were filtered at
different values: M–P 7.4 Hz, heel 7.4 Hz, ankle 8.3 Hz, knee 10.1 Hz, hip 9.4 Hz and
shoulder 6.5 Hz. These values were determined by minimizing the root mean square difference between the vertical acceleration of the body’s center of mass, derived from position
data, and the same measure derived from (the criterion) force plate data. Two-dimensional, sagittal plane kinematic and kinetic variables were calculated. Each variable was
calculated for each trial and then averaged over the 12 trials.
2.3. Kinematic measures
All linear and angular velocities (Eq. (1)) and accelerations (Eq. (2)) were calculated
using the finite difference procedure:
xi ¼ ðhiþ 1 $ hi$1 Þ=ð2 & DtÞ
ð1Þ
where xi is the angular velocity and hi is the angle at point i; Dt is the time between adjacent samples (0.0025 s):
ai ¼ ½hiþ 1 $ ð2 & hi Þ þ hi$1 =Dt2 (
ð2Þ
where ai is the angular acceleration and hi is the angle at point i; Dt is the time between
adjacent samples (0.0025 s).
Performance in vertical jumping was measured as the peak post takeoff vertical position
of the body’s center of mass relative to its position at takeoff. This was determined from
marker coordinate data combined with anthropometric data (Winter, 2005). Coupling
time, generally defined as the isometric contraction period between eccentric and concentric actions, has been shown to be an important factor in determining the magnitude of
enhancement associated with the SSC (Edman, Elzinga, & Noble, 1978). While maximal
effort vertical jumps do not employ a distinct period of isometric contraction, the muscle
dynamics around the transition between the end of the eccentric and start of the concentric
actions do appear to vary between jumps of different eccentric loads and is an important
830
K.A. Moran, E.S. Wallace / Human Movement Science 26 (2007) 824–840
determinant of SSC enhancement in vertical jumps (Bosco, Komi, & Ito, 1981). Bosco
et al. used joint angular velocity to identify coupling time, but they failed to quantify
the precise range of velocities used. In the present study, this transition period was quantified as the duration when the joint angular velocity was between plus and minus 1 rad s$1
(57.3! s$1). This range was arrived at after observing numerous angular displacement–time
and velocity–time curves. To avoid confusion between the use of the term coupling time as
traditionally employed (isometric phase), and the manner in which it is used within this
study (±1 rad s$1), the term ‘transition time’ will be used (Rodacki, Fowler, & Bennett,
2002).
2.4. Kinetic measures
Net intersegmental forces and moments were calculated using standard inverse dynamics, combining kinematic and ground reaction force data with anthropometric data (Winter, 2005) in an appropriate biomechanical link segment model. Net muscle power
produced at each joint was calculated as the dot product of the net joint moment and
the joint angular velocity (Winter, 2005). The work done by the muscles at each joint
was calculated from the integral of power with respect to time using the Trapezoidal rule
(Eq. (3)). Care was taken to integrate between appropriate time epochs to distinguish
between positive and negative work. Hip extension, knee extension and ankle plantar flexion moments were defined as positive. For kinetic calculations it was assumed that ground
reaction forces from each foot were symmetrical and therefore taken as half that produced
by both feet:
Workdone ¼
i¼n
X
½ðP i þ P iþ 1 Þ=2( & Dt
i¼1
ð3Þ
where Pi is the angular power at point i; Dt is the time between adjacent samples (0.0025 s).
2.5. Data analysis
Differences between the six jump conditions (SJ, CMJ and DJ30 – each from 70! and
90! knee joint flexion) were tested for statistical significance using a two factor analysis
of variance (ANOVA) with repeated measures on the participants (3 · 2 · participants).
The two factors of analysis (main effects) were jump condition (SJ, CMJ and DJ30) and
knee joint angle (70! and 90! flexion). Where a statistically significant main effect of jump
condition was found a repeated measures ANOVA was performed, followed by post hoc
multiple paired t-tests with appropriate Bonferroni adjustment. Where a statistically significant interaction was found planned post hoc comparisons using paired t-tests, with
appropriate Bonferroni adjustment, were completed for the differences between each jump
condition (e.g., DJ30-CMJ, CMJ-SJ and DJ30-SJ) from 70! in comparison to 90!. All p
values less that .05 were considered statistically significant.
3. Results
Fig. 3 illustrates typical angle, moment and power data for a SJ, CMJ and DJ30 from
90! knee flexion.
831
K.A. Moran, E.S. Wallace / Human Movement Science 26 (2007) 824–840
200
4.5
Hip Moment
180
4
160
3.5
1.5
-10
1
60
-20
0.5
40
0
20
-30
-0.5
0
-40
-1
180
5
Knee M oment
25
Knee Power
160
4
20
140
120
1
60
N.m/kg
80
10
2
Degrees
100
15
3
5
0
-5
0
40
-15
-2
0
140
4
Ankle Moment
15
10
N.m/Kg
Degrees
2
5
1.5
0.1
0.05
0.2
0.15
0.26
0.31
0.36
0.41
0.46
0.52
0.57
0.62
0.67
0.72
0.78
0.83
0
0.88
1
-5
0.1
0.05
0.2
0.15
0.26
0.31
0.36
0.41
0.46
0.52
0.57
0.62
0.67
-15
0.72
0
0.78
-10
0
0.83
0.5
0.88
20
0.93
0.1
0.05
0.2
0.15
0.26
0.31
0.36
0.41
0.46
0.52
0.57
0.62
0.67
0.72
0.78
0.83
0.88
20
2.5
40
0.93
25
3
100
60
30
Ankle Power
3.5
120
80
-20
0.93
Ankle Angle
-10
-1
20
W/Kg
Knee Angle
0
W/Kg
2
W/Kg
80
10
2.5
Degrees
100
20
3
140
120
30
Hip Power
N.m/kg
Hip Angle
-20
Fig. 3. Representative time histories for the ankle, knee and hip for angle, moment and power during jumps from
90! knee joint flexion (SJ; CMJ; DJ30).
The analyses of kinematic, positional, temporal and kinetic data are presented to elucidate significant differences for either main effect (jump condition or knee joint angle)
or interaction between them for the different jump conditions. The results are presented,
where appropriate, in terms of the lowering phase of the jump associated with loading,
and the upward phase associated with propulsion. In addition, transition times and peak
jump heights are considered. The accompanying tables, concentrating on the noted effects
on the hip, knee and ankle joints, have been constructed to indicate significant main effects
and relevant post hoc outcomes for the jump conditions. For the analysis of peak negative
angular velocity, negative work done and duration of the transition phase, only the DJ30
and CMJ were statistically compared because the SJ employed
