Key words
countermovement jump - drop jump - female athlete - performance
Introduction
Lacrosse is a high intensity invasion sport that requires athletes to perform
sprints, changes of direction and execute skills such as passing and shooting often
while undertaking bodily contact [1]
[2]. Lacrosse is considered the fastest growing sport in
the United States and as such participation rates across all levels of competition
are increasing substantially. In fact, in 2018 there were 43,228 participants
combined among men’s and women’s collegiate lacrosse programs [3]. With the increase in participation rates,
specifically at the collegiate level there is a need for additional evidence that
can be used by sports medicine and sport science practitioners to enhance on-field
performance and inform training and rehabilitation programs.
The ability to produce strength and power in the lower limbs underpins the successful
performance of many movements common to lacrosse [1]
[2]
[4]
[5]. It is common within research and practice to
identify specific measures of force production that possess discriminative ability
between higher and lower levels of performers [6]
[7]. For example, previous research has reported that
starting players in elite Australian Rules football possess greater speed, leg power
and endurance compared to their non-starting counterparts [6]. More specific to lacrosse, Sell and colleagues [7] identified that starters in a collegiate
men’s team possessed greater maximal speed, change of direction ability,
vertical jump height and body mass compared to non-starters. In turn, this valuable
information is used by coaches to understand the physical needs of an athlete
required to perform at a specific level of competition and inform training
prescription.
Participation in the sport of lacrosse presents a substantial risk of soft-tissue
injury to the knee and upper leg [8]
[9]. Injuries to the knee are considered more severe
than other lower-limb injuries because they have been found to result in substantial
time loss from training and competition compared to other body regions [8]
[9]. Low levels of
muscular strength, inadequate agonist / antagonist strength ratios and
bilateral strength deficits are commonly noted internal modifiable risk factors for
non-contact lower-extremity injury [10]
[11]. Therefore, Isokinetic strength testing is commonly
used by clinicians and researchers to provide a robust and objective measurement of
muscle strength as it relates to injury risk of injury to the knee [12]
[13]. Currently there
is a need to present isokinetic strength data for the quadriceps and hamstrings of
collegiate lacrosse athletes to serve as a reference point to inform injury
prevention and rehabilitation programs for this quickly expanding cohort of
athletes.
Isokinetic strength, countermovement (CMJ) and drop jump (DJ) testing each measure
different aspects of an athlete’s force generating capacity, which is
valuable for on-field performance and to inform the design of training programs.
Owing to the need for lacrosse athletes to frequently accelerate, change directions
and withstand physical contact, the ability to express lower-limb strength and power
is important for successful performance [1]
[2]
[4]
[5]. Moreover, a comparison of these strength and power
qualities between higher and lower-level performers can help sports performance
practitioners prioritize training methods to maximize on-field performance. To date,
only one study has examined the differences in strength and power characteristics
in
Division I Men’s lacrosse starters and non-starters [7]. Additionally, only one study has investigated these differences in
Women’s Division I lacrosse athletes [14].
However, the investigation conducted by Vescovi et al. [14] was completed 14 years ago and did not include a measure of lower
limb strength. Therefore, the primary aim of this investigation is to compare
isokinetic strength, CMJ and DJ variables between higher contributors and lower
contributors within NCAA Division I Men’s and Women’s lacrosse
athletes. A secondary aim is to compare the lower-limb force generating capabilities
between male and female collegiate lacrosse athletes. With an overarching objective
to provide a lower-limb isokinetic strength and power profile of collegiate lacrosse
athletes. It was hypothesized that statistically significant differences in strength
and power measures would be observed between high-contributing players and their
lower-contributing counterparts. Additionally, it was hypothesized that
statistically significant differences in lower-limb strength and power will be
observed between male and female collegiate lacrosse athletes.
Materials and Methods
Study design
A cross-sectional observational cohort study design was employed to compare the
isokinetic strength of the hamstring and quadriceps muscle groups, CMJ and DJ
variables between high-contributors and low in game contributors within NCAA
Division I men’s and women’s lacrosse athletes and to compare
the male and female athletes. For the first comparison the independent variables
were the level of contribution from the players in competition. For the second
comparison, the independent variable was the athlete’s sex. For both
comparisons the dependent variables from the isokinetic testing were: concentric
isokinetic peak torque of the quadriceps and hamstring muscle groups across
three speeds of 60°·s−1,
180°·s−1 and
300°·s−1
[13]. Dependent variables from the CMJ were jump height (JH) and
relative peak power (RPP). Additionally, reactive strength index (RSI) was the
dependent variable from the drop jump. The CMJ and DJ were performed first
followed by the isokinetic strength testing to minimize the risk of fatigue or
potentiation. All testing occurred over a single day in the pre-competition
phase of the athlete’s periodized training program and all athletes were
free from injury at the time of data collection. Ethical approval was obtained
by the research ethics committee from Southern Connecticut State University and
Yale University.
Participants
A convenience sample was obtained from the University’s men’s
(N=36, age=20.1±0.6 yrs,
height=183.8±5.5 cm,
mass=92.6±15.8 kg ) and women’s
(N=30, age=20.2±0.8 yrs ,
height=169.6±6.7 cm,
mass=63.5±7.3 kg) lacrosse programs.
Retrospective from the data collection and following the competitive phase of
the training program, the athletes were then sub-categorized as “higher
contributors” (Men: N=18; Women: N=15) and
“lower contributors” (Men: N=18; Women: N=15)
based upon the number of games they competed in during the regular season.
Specifically, higher contributors were defined as those players that played in
more than eight games which was half of the team’s sixteen regular
season games. Higher contributors and lower contributors were chosen instead of
the traditional “starters and non-starters” delineation to
better align with the tactical decision making of the team’s coaching
staff. The coaching staff frequently alternated the starting players to suit
in-game strategy. Additionally, rules within the sport of lacrosse allow for
frequent in-game substitutions of players providing a clear delineation between
higher and lower-level performers based upon the number of games played in.
Please note that the conference the athletes competed within does not allow for
red shirt players which is a player that trains with the team but is not
eligible to compete in games. Therefore, all members of the team were eligible
to compete in all games. The characteristics of participants is provided in
[Table 1].
Table 1 Characteristics of participants. No statistically
significant difference in characteristics were
observed.
|
Male
|
Female
|
|
Total (N=36)
|
Higher Contributors (N=18)
|
Lower Contributors (N=18)
|
Total (N=30)
|
Higher Contributors (N=15)
|
Lower Contributors (N=15)
|
|
Age (yrs)
|
20.2±0.8
|
20.3±0.4
|
19.5±0.2
|
20.2±0.5
|
20.8±0.8
|
19.7±0.2
|
|
Height (cm)
|
183.8±5.5
|
183.4±5.5
|
184.1±5.6
|
169.6±6.7
|
169.3±6.7
|
169.8±7.01
|
|
Mass (kg)
|
92.6±15.8
|
90.8±5.8
|
87.9±8.1
|
63.5±7.3
|
64.1±7.2
|
62.9±7.5
|
|
BMI (kg/m²)
|
26.9±3.9
|
26.9±1.3
|
27.5±6.5
|
22.1±1.7
|
22.3±1.8
|
21.7±1.7
|
|
Years in program
|
2.29±1.0
|
2.38±1.0
|
2.2±1.0
|
2.3±1.0
|
2.7±1.1
|
1.9±1.0
|
Procedures
Isokinetic Strength
All testing occurred during the pre-competition phase of the
athletes' periodized training program. All participants were
familiar with the testing procedures as they are part of their routine
monitoring of physical capabilities. Each testing session commenced with the
athletes completing a standardized warm-up consisting of three minutes of
moderate intensity jogging followed by dynamic stretching over a
10 m distance targeting the musculature of the lower extremities.
Following completion of the standardized warm-up athletes were provided with
2 minutes of self-directed preparation to target musculature that
they did not feel were adequately addressed during the warm-up.
Isokinetic strength during a concentric muscle action of both the right and
left quadriceps and hamstring muscle groups was assessed across three
velocities: 60°·s−1,
180°·s−1 and
300°·s−1 (Biodex System 3, Biodex
Medical Systems, Shirley New York USA) [13].
The order of the velocities used in the isokinetic strength testing was not
randomized and always started with
60°·s−1 followed by
180°·s−1 and concluding with
300°·s−1. Athletes were comfortably
secured using shin, thigh, pelvic and upper torso stabilization straps. To
isolate force production to the lower extremities and limit the influence of
the upper-body, athletes were instructed to cross their arms over their
chest and not hold the testing chair during repetitions. The axis of
rotation of the knee was aligned with the shaft of the dynamometer with the
ankle resistance pad secured immediately superior to the medial malleolus.
Prior to testing on both the right and left sides a gravity correction for
limb weight was performed and the athlete’s dominant leg was
assessed first. Prior to testing at each velocity, the athlete completed
three submaximal repetitions of increasing effort, followed by five maximal
repetitions. One minute of rest was provided prior to increasing the testing
velocity. Athletes were verbally encouraged throughout each repetition to
ensure a maximal effort was provided. Peak torque (Nm/kg) was
normalized to body mass, and values for both quadriceps and hamstring muscle
groups for each limb at each speed were retained for analysis. Reliability
of isokinetic strength testing on the Biodex System 3 at the velocities used
in this investigation has been previously established [13]. [Figure 1]
provides a visual representation of the setup for isokinetic strength
testing.
Figure 1 Visual representation of setup for the isokinetic
strength test.
Countermovement Jump
Athletes completed a set of four submaximal CMJs with the instruction to increase
the intensity of each jump so that the final jump was a “near maximal
effort”. After two minutes of rest the athlete performed a set of four
maximal CMJs with 10–15 seconds between attempts on a force
plate sampling at 500 Hz (Kistler Quattro Jump, Winterthur Switzerland).
To isolate force production in the lower extremity, each jump was performed with
hands placed on hips. The athletes were instructed to perform a countermovement
to a self-selected depth and jump for maximal height [15]. The average of the two attempts that produced the greatest jump
height were retained for analysis. [Figure 2]
provides visual representation of the CMJ test.
Figure 2 Visual representation of the countermovement jump.
Drop Jump
Drop jumps were performed from a 30 cm box onto a force plate sampling at
500 Hz (Kistler Quattro Jump, Winterthur Switzerland). Although the
athletes were familiar with the drop jump exercise because it is part of their
normal training routine, they were provided with opportunities to practice until
sufficient technique was observed by the tester (i. e. not jumping off,
or stepping down from the box when initiating their jump). For each attempt the
athlete placed their hands on their hips and were provided with the specific
instructions to “jump for maximal height and minimal ground contact
time” [16]. The athlete performed a
minimum of four drop jumps with the attempt that produced the greatest reactive
strength index (RSI) score as determined by jump height divided by contact time
retained for analysis. [Figure 3] provides a
visual representation of the DJ test.
Figure 3 Visual representation of the drop jump.
From previous testing using the same equipment from the same laboratory in a
similar group of collegiate athletes all variables from the CMJ and DJ
demonstrated excellent test-retest reliability. Specifically, the reliability of
the CMJ derived variables were Jump Height (ICC=0.972;
CV=4.2%), Relative Peak Power (ICC=0.983;
CV=3.2%). Variables derived from the DJ were Jump Height
(ICC=0.991; CV=2.5%), Contact Time (ICC=0.997;
CV=4.3%), RSI (ICC=0.975; CV=4.3%).
These measurements are similar to other studies that have investigated the
reliability of jump testing in NCAA Division I collegiate athletes [17]
[18].
Statistical Analysis
All statistical analyses were conducted using the Statistical Package for the
Social Science (SPSS) version 26 (IBM, New York, NY, USA). A Shapiro-Wilk test
was used to assess the normality of the data. All data were distributed
normally; therefore, to compare the differences in isokinetic strength, CMJ and
DJ measures one-way analysis of variance (ANOVA) were utilized with an alpha
level of significance set at p≤ 0.05. Three separate comparisons
were conducted (i) a comparison of higher and lower-level contributors within
the male participants; (ii) a comparison of higher and lower-level contributors
within the female participants; (iii) A comparison between the males and
females. Cohen’s d effect sizes were calculated to determine the
magnitude of the differences between high contributors and low contributors with
the following descriptors used to describe the effect sizes; very
small=0.01–0.19; small=0.20–0.49;
medium=0.50–0.79; large=0.80–1.19; very
large=1.20+[19].
Results
Participant Characteristics
There was no statistically significant difference in the height
(p=0.718; d=0.09) or body mass
(p=0.510; d=0.40) between the male higher contributors
and lower contributors. Additionally, there was no statistically significant
difference in the height (p=0.859; d=0.07) or mass
(p=0.667; d=0.17) between the female higher
contributors and lower contributors. Male players possessed significantly
greater height (p<0.01; d=2.31) and mass (p<0.01;
d=3.7).
High vs Low Contributor Comparison
Isokinetic Strength
The isokinetic strength data for both higher contributing and lower
contributing male and female lacrosse athletes are presented in [Tables 2] and [3], respectively. Isokinetic strength of the left hamstrings
at 300°·s−1 was significantly greater
in the higher contributing male players compared to lower contributing
ones (p=0.05; d=0.69).
Table 2 Lower limb Isokinetic strength and power
profile of men’s higher contributors and lower
contributors. Flex=Flexion; Ext=Extension;
Dif=Difference; H:Q
Ratio=Hamstring:Quadriceps ratio.
*=Statistically different (P≤0.05).
VS=very small; S=small; M=medium;
L=large; VL=Very Large;
CMJ=Countermovement Jump; DJ=Drop
Jump
|
Group
|
|
Measurement (Mean±SD)
|
Higher Contributors (N=18)
|
Lower Contributors (N=18)
|
% Difference
|
P- Value
|
Cohen’s d
|
|
Isokinetic Strength at
60°·s
−1
|
|
Right Flexion (Nm/kg)
|
1.49±0.25
|
1.37±0.32
|
−8.05
|
0.22
|
d=0.41 (S)
|
|
Right Extension (Nm/kg)
|
2.65±0.49
|
2.41±0.71
|
−9.05
|
0.25
|
d=0.39 (S)
|
|
Right H:Q Ratio (%)
|
57.09±7.8
|
54.38±9.3
|
−4.74
|
0.35
|
d=0.31 (S)
|
|
Left Flexion (Nm/kg)
|
1.46±0.20
|
1.35±0.28
|
−7.53
|
0.20
|
d=0.45 (S)
|
|
Left Extension (Nm/kg)
|
2.67±0.48
|
2.50±0.52
|
−6.36
|
0.32
|
d=0.33 (S)
|
|
Left H:Q Ratio (%)
|
55.88±9.5
|
54.5±7.27
|
−2.47
|
0.63
|
d=0.16 (S)
|
|
Isokinetic Strength at
180°·s
−1
|
|
Right Flexion (Nm/kg)
|
1.21±0.24
|
1.06±0.20
|
−12.39
|
0.06
|
d=0.67 (M)
|
|
Right Extension (Nm/kg)
|
1.86±0.33
|
1.72±0.40
|
−7.52
|
0.28
|
d=0.38 (S)
|
|
Right H:Q Ratio (%)
|
65.96±14.00
|
59.63±10.53
|
−9.59
|
0.14
|
d=0.51 (M)
|
|
Left Flexion (Nm/kg)
|
1.16±0.23
|
1.01±0.21
|
−12.93
|
0.06
|
d=0.68 (M)
|
|
Left Extension (Nm/kg)
|
1.85±0.34
|
1.61±0.51
|
−12.97
|
0.11
|
d=0.55 (M)
|
|
Left H:Q Ratio (%)
|
63.88±13.09
|
59.82±9.7
|
−6.35
|
0.30
|
d=0.35 (S)
|
|
Isokinetic Strength at
300°·s
−1
|
|
Right Flexion (Nm/kg)
|
0.99±0.23
|
0.86±0.16
|
−13.13
|
0.06
|
d=0.65 (M)
|
|
Right Extension (Nm/kg)
|
1.45±0.32
|
1.35±0.28
|
−6.89
|
0.33
|
d=0.33 (S)
|
|
Right H:Q Ratio (%)
|
69.68±13.58
|
62.22±12.44
|
−10.70
|
0.10
|
d=0.57 (M)
|
|
Left Flexion (Nm/kg)
|
0.97
±
0.24
|
0.82± 0.19
|
−15.46
|
0.05*
|
d
=0.69 (M)
|
|
Left Extension (Nm/kg)
|
1.47±0.34
|
1.36±0.29
|
−7.48
|
0.29
|
d=0.34 (S)
|
|
Left H:Q Ratio (%)
|
66.73±13.25
|
60.40±11.34
|
−9.48
|
0.14
|
d=0.51 (M)
|
|
CMJ & DJ Measures
|
|
CMJ JH (CM)
|
38.1±14.1
|
37.5±5.7
|
1.5
|
0.86
|
d=0.05 (VS)
|
|
CMJ Relative PP (W/Kg)
|
60.4±
7.1
|
56.1±5.3
|
5.6
|
0.04
|
d
=0.68 (M)
|
|
DJ RSI (cm/sec)
|
155.5±28.8
|
161.7±23.5
|
3.9
|
0.5
|
d=0.23 (S)
|
Table 3 Lower limb Isokinetic strength and power
profile of female higher contributors and lower
contributorsFlex=Flexion; Ext=Extension;
H:Q Ratio=Hamstring:Quadriceps ratio.
*=Statistically different (P≤0.05).
VS=very small; S=small; M=medium;
L=large; VL=Very Large;
CMJ=Countermovement jump; DJ=Drop
Jump
|
Group
|
|
Measurement (Mean±SD)
|
Higher Contributors (N=15)
|
Lower Contributors (N=15)
|
% Difference
|
P- Value
|
Cohen’s d
|
|
Isokinetic Strength at
60°·s
−1
|
|
Right Flexion (Nm/kg)
|
1.36±0.15
|
1.26±0.18
|
−7.63
|
0.13
|
d=0.60 (M)
|
|
Right Extension (Nm/kg)
|
2.39±0.41
|
2.26±0.23
|
−5.59
|
0.26
|
d=0.39 (S)
|
|
Right H:Q Ratio (%)
|
57.21±7.49
|
56.09±7.36
|
−1.97
|
0.68
|
d=0.15 (S)
|
|
Left Flexion (Nm/kg)
|
1.35±
0.16
|
1.21
±
0.16
|
−10.93
|
0.03 *
|
d
=0.87 (L)
|
|
Left Extension (Nm/kg)
|
2.31±0.31
|
2.12±0.33
|
−8.57
|
0.12
|
d=0.59 (M)
|
|
Left H:Q Ratio
|
59.2±5.6
|
57.7±7.83
|
−2.56
|
0.57
|
d=0.22 (S)
|
|
Isokinetic Strength at
180°·s
−1
|
|
Right Flexion (Nm/kg)
|
1.04±0.07
|
0.98±0.16
|
−5.94
|
0.24
|
d=0.48 (S)
|
|
Right Extension (Nm/kg)
|
1.63±0.23
|
1.55±0.19
|
−5.03
|
0.30
|
d=0.37 (S)
|
|
Right H:Q Ratio (%)
|
64.32±7.61
|
63.32±7.3
|
−1.56
|
0.71
|
d=0.13 (S)
|
|
Left Flexion (Nm/kg)
|
1.04±0.14
|
0.97±0.17
|
−6.95
|
0.20
|
d=0.44 (S)
|
|
Left Extension (Nm/kg)
|
1.62±
0.14
|
1.46
±
0.19
|
−10.38
|
0.01*
|
d
=0.95 (L)
|
|
Left H:Q Ratio (%)
|
64.24±6.96
|
66.22±8.29
|
3.03
|
0.48
|
d=0.22 (S)
|
|
Isokinetic Strength at
300°·s
−1
|
|
Right Flexion (Nm/kg)
|
0.86±0.09
|
0.85±0.15
|
−1.16
|
0.59
|
d=0.09 (VS)
|
|
Right Extension (Nm/kg)
|
1.29±0.20
|
1.30±0.17
|
0.77
|
0.80
|
d=0.01 (VS)
|
|
Right H:Q Ratio (%)
|
67.4±10.11
|
65.5±9.96
|
−2.85
|
0.61
|
d=0.18 (VS)
|
|
Left Flexion (Nm/kg)
|
0.87±0.11
|
0.84±0.13
|
−3.50
|
0.54
|
d=0.24 (S)
|
|
Left Extension (Nm/kg)
|
1.29±
0.20
|
1.30
+±+
0.17
|
0.77
|
0.24
|
d
=0.05 (VS)
|
|
Left H:Q Ratio (%)
|
65.55±7.65
|
69.30±9.1
|
5.56
|
0.23
|
d=0.45 (S)
|
|
CMJ and DJ Measures
|
|
CMJ JH (CM)
|
28.4±3.9
|
26.5±5.1
|
6.6
|
0.26
|
d=0.41 (S)
|
|
CMJ Relative PP (W/Kg)
|
43.3±5.2
|
41.3±5.5
|
4.9
|
0.31
|
d=0.37 (S)
|
|
DJ RSI (cm/sec)
|
96.2±28.3
|
87.5±18.3
|
9.4
|
0.32
|
d=0.36 (S)
|
Within the female athletes, a statistically significant difference
between the higher contributors and lower contributors was observed for
the relative peak torque of the left hamstrings at
60°·s−1 (p=0.03;
d=0.87), peak torque of the left quadriceps at
180°·s−1 (p=0.04;
d=0.95).
There were no statistically significant differences in the hamstring to
quadriceps ratio (H:Q ratio) between higher and lower contributing
players in either the male or female players.
Countermovement Jump
The countermovement and drop jump data for both the higher contributing and lower
contributing male and female players is presented in [Tables 2] & [3]. The relative
peak power of male higher contributors was significantly greater compared to
lower contributors (p=0.04; d=0.68). Within the
females there were no statistically significant differences in the jump height
or relative peak power between high contributing and low contributing
athletes.
Drop Jump
There were no statistically significant differences in the reactive strength
index of male and female high contributing or low contributing athletes.
Male vs Female Comparison
Isokinetic strength
The isokinetic strength data for the males and females is presented in
[Table 4]. At
60°·s−1 there were statistically
significant differences in the hamstring strength of male players
compared to female players in the right hamstrings
(p=0.04; d=0.54), left hamstring
(p=0.02; d=0.10) and left quadriceps
(p=0.01; d=0.84). At
180°·s−1 significant differences
in isokinetic strength between males and females were found in the right
hamstrings (p=0.01; d=0.65), the right
quadriceps (p=0.01; d=0.66) and the left
quadriceps (p=0.03; d=0.56). At
300°·s−1 the only statistically
significant difference between the males and females was found in the
left quadriceps (p=0.02; d=0.51).
Isokinetic strength testing results are provided in [Table 4].
Table 4 Lower limb Isokinetic strength and power
comparison of male and female lacrosse
players Flex=Flexion; Ext=Extension; H:Q
Ratio=Hamstring:Quadriceps ratio.
*=Statistically different (P≤0.05).
VS=very small; S=small; M=medium;
L=large; VL=Very Large;
CMJ=Countermovement jump; DJ=Drop
Jump.
|
Group
|
|
Measurement (Mean±SD)
|
Males (N=36)
|
Females (N=30)
|
% Difference
|
P- Value
|
Cohen’s d
|
|
Isokinetic Strength at
60°·s
−1
|
|
Right Flexion (Nm/kg)
|
1.44±
0.29
|
1.31±
0.17
|
−9.02
|
0.04*
|
d
=0.54 (M)
|
|
Right Extension (Nm/kg)
|
2.54±0.61
|
2.33±0.33
|
−8.26
|
0.09
|
d=0.42 (S)
|
|
Right H:Q Ratio (%)
|
55.77±8.50
|
56.53±7.32
|
1.36
|
0.19
|
d=0.09 (VS)
|
|
Left Flexion (Nm/kg)
|
1.41±0.24
|
1.28
±
1.77
|
−9.21
|
0.02*
|
d
=0.10 (VS)
|
|
Left Extension (Nm/kg)
|
2.58
±
0.50
|
2.22
±
0.33
|
−13.95
|
0.01*
|
d
=0.84 (L)
|
|
Left H:Q Ratio (%)
|
55.22±8.40
|
58.48±6.74
|
−5.90
|
0.09
|
d=0.42 (S)
|
|
Isokinetic Strength at
180°·s
−1
|
|
Right Flexion (Nm/kg)
|
1.13
±
0.23
|
1.01
±
0.12
|
−10.61
|
0.01*
|
d
=0.65 (M)
|
|
Right Extension (Nm/kg)
|
1.79
±
0.37
|
1.59
±
0.21
|
−11.17
|
0.01*
|
d
=0.66 (M)
|
|
Right H:Q Ratio (%)
|
62.89±12.67
|
63.82±7.35
|
1.14
|
0.72
|
d=0.08 (VS)
|
|
Left Flexion (Nm/kg)
|
1.09±0.23
|
1.00±0.16
|
−8.52
|
0.09
|
d=0.45 (S)
|
|
Left Extension (Nm/kg)
|
1.73
±
0.44
|
1.54
±
0.18
|
−10.98
|
0.03*
|
d
=0.56 (M)
|
|
Left H:Q Ratio (%)
|
61.9±11.5
|
65.2±7.59
|
5.33
|
0.18
|
d=0.33 (S)
|
|
Isokinetic Strength at
300°·s
−1
|
|
Right Flexion (Nm/kg)
|
0.93±0.21
|
0.86±0.12
|
−7.52
|
0.10
|
d=0.40 (S)
|
|
Right Extension (Nm/kg)
|
1.40±0.30
|
1.29±0.18
|
−7.85
|
0.10
|
d=0.44 (S)
|
|
Right H:Q Ratio (%)
|
66.06±13.39
|
66.47±9.91
|
0.62
|
0.80
|
d=0.03 (VS)
|
|
Left Flexion (Nm/kg)
|
0.90±0.23
|
0.85±0.12
|
−5.55
|
0.33
|
d=0.27 (S)
|
|
Left Extension (Nm/kg)
|
1.42
±
0.31
|
1.26
±
0.17
|
−11.26
|
0.02*
|
d
=0.51 (M)
|
|
Left H:Q Ratio (%)
|
63.65±12.59
|
67.43±8.48
|
5.93
|
0.16
|
d=0.35 (S)
|
|
CMJ & DJ Measures
|
|
CMJ JH (CM)
|
40.70
±
8.65
|
27.40
±
4.59
|
−32.67
|
<0.01*
|
d
=1.92 (L)
|
|
CMJ Relative PP (W/Kg)
|
58.86
±
6.6
|
42.06
±
5.27
|
−28.54
|
<0.01*
|
d
=2.81 (VL)
|
|
DJ RSI (cm/sec)
|
154.53
±
27.48
|
92.21
±
23.33
|
−40.32
|
<0.01*
|
d
=2.44 (VL)
|
Countermovement jump
A large statistically significant difference was observed in countermovement jump
height in males compared to females (p<0.01;
d=1.92). A very large statistically significant difference
(p<0.01; d=2.81) was found in relative peak
power of male players compared to female.
Drop Jump
A very large statistically significant difference (p<0.01;
d=2.44) was found in reactive strength index between males and
females.
Discussion
This study sought to determine if specific characteristics of lower limb force
generating capacity could discriminate between higher and lower-level players within
the team. Additionally, a secondary objective was to compare the force generating
capacity between male and female collegiate lacrosse athletes. The overarching
objective of the study was to provide sports medicine and science practitioners and
researchers with an isokinetic strength profile of the lower limb for NCAA Division
I Men’s and Women’s lacrosse athletes that can be used to inform
rehabilitation and physical preparation programs.
The main findings from this study were that in the men’s cohort the ability
to produce strength in the left hamstrings at relatively high contraction speeds
(300°·s−1) was significantly greater in the
higher contributing compared to the lower contributing athletes. Additionally,
higher contributing athletes produced significantly greater relative peak power in
the CMJ compared to their lower contributing counterparts. Within the
women’s cohort the ability to produce strength in the left hamstrings at
slow contraction speeds (60°sec) and strength in the left quadriceps at
moderate speeds (180°·s−1) was significantly
greater in the contributors compared to the non-contributors.
Amongst both the male and female athletes the ability of the higher contributing
players to produce greater strength in the left hamstrings was a common trend that
reached statistical significance at moderate speeds for the females and high speeds
for the males. This finding may be linked to the important technical skill of
overhand lacrosse shooting. During this skill when shooting right-handed the left
leg is stepped forward then planted into the ground during the stick acceleration
phase and contributes to force production through a powerful hip extension [20]. Previous research has demonstrated that the biceps
femoris muscle significantly contributes to force production during execution of an
overhand lacrosse shot and that the activation of the muscle increases concomitantly
with shot speed [21]. Additionally, Talpey et al.
[22] found that peak torque of the left hamstrings
increased significantly over the course of a season, a finding that was not observed
in the quadriceps indicating that exposure to high-speed overhand shooting typical
in training and competition may potentially provide a stimulus to enhance force
generating capacity of the hamstrings. This finding may provide impetus to further
investigate the relationship between hamstring strength and overhand shooting in
lacrosse.
Hamstring to quadriceps strength ratio is a valuable metric used to inform the
rehabilitation process [12]. Therefore, an important
finding from this investigation is that regardless of the contribution status of the
athlete for both males and females, the hamstring to quadriceps ratio was within the
typical range of 50–80% presented in the literature for non-injured
collegiate athletes [23]. Additionally, the relative
peak torque values of both the hamstrings and quadriceps across all three speeds in
the current investigation align closely with those reported by Tsuchiya and
colleagues [24] in a cohort of collegiate-aged
lacrosse players. These novel findings from the current investigation provide sports
medicine practitioners within collegiate lacrosse with benchmark isokinetic strength
data to inform their return to play programs.
Comparing physical qualities between higher and lower levels of competition and
starters and non-starters is a commonly used approach to understand important
physical qualities for performance in a particular sport. An important finding from
the current investigation was the higher contributing male players were able to
produce significantly greater relative peak power than non-contributing players.
These findings can be compared to those of Sell et al. [7] who reported starting NCAA Division I lacrosse players had a
significantly greater vertical jump than non-starters. However, within that study
there was no statistically significant difference in one repetition maximum hang
clean as a test of muscular power between starters and nonstarters. The findings
from the current investigation add to those reported by Sell [7] because a countermovement jump performed on a force
plate without an arm swing (as used in the current investigation) is a direct
assessment of lower-limb power whereas performance in a vertical jump with an arm
swing (as used in the study by Sell) is significantly influenced by the use of the
arms and technical factors [25]. In the current
investigation there was no-significant difference in the CMJ jump height between
male high contributors and low contributors, even though there was significant
difference in relative power output. Although it is plausible that other factors
such as injury and illness may influence the discriminative ability of a physical
quality, this finding indicates that physical preparation programs should
specifically target the development of relative peak power. Meaning that any
development in maximal power output achieved through training should also aim for
a
maintenance or reduction in body mass. Reactive strength assessed via a drop jump
was not significantly different between male higher contributors and lesser
contributors. Reactive strength is a specific power quality that is related to an
athlete’s ability to produce power in a short and fast stretch-shortening
cycle [16]. Reactive strength underpins movements such
as jumps from a run-up, sprinting at maximal speeds and changing directions while
jumps from a run-up are not common in lacrosse sprinting and changing directions are
common movements amongst specific position groups [1]
[2]. Therefore, it is somewhat surprising
that this specific power quality did not differ between groups of higher and lesser
contributors. However, future research may consider a comparison between position
groups which may yield different results.
This was the second investigation and first in 14 years that has attempted to
identify physical characteristics that can discriminate between higher and
lower-level performers in Division I Women’s lacrosse [14]. Interestingly, the findings from both the current
investigation and the 2007 study by Vescovi [14]
demonstrated homogeneity between higher and lower-level performers within Division
I
Women’s lacrosse players. The lack of significant differences in physical
qualities between starters and non-starters in Division I women’s athletes
has also been recently observed in soccer [26]. This
result may be related to the resistance training habits of the team and indicates
that technical, tactical or psychological aspects of performance rather than
physical characteristics discriminate between higher and lower-level collegiate
women’s athletes [27]. Future research may
focus on understanding aspects of performance in collegiate women’s lacrosse
other than physical qualities that are different between higher and lower levels of
performance. Research in this area would provide valuable information to inform
talent identification and talent development within this rapidly growing sport [27].
Sex differences in isokinetic strength were observed across the different speeds.
The
male athletes produced greater force in all measures of isokinetic strength with
statistically significant differences achieved for the right hamstrings at
60°·s−1 and
180°·s−1, the left hamstring at
60°·s−1, the right quadriceps at
180°·s−1 and the left quadriceps at
60°·s−1,
180°·s−1 and
300°·s−1. This finding is consistent with the
results of previous research that has demonstrated that males produce approximately
45% and 35% greater values in peak torque in their hamstrings and
quadriceps respectively compared to their female counterparts competing in the same
sport [28]. There were “very small” to
“small” non-significant differences in the hamstring to quadriceps
ratio between the males and females. This isokinetic strength variable has received
considerable attention in the literature owing to its diagnostic utility for the
mitigation of risk associated with anterior cruciate ligament (ACL) injury [29]. These ratios for males and females are similar to
those reported in the literature [28]
[29]. However, the H:Q ratios in the present study are
slightly greater than those previously reported [29].
This may be due to the specific strength training program for the female lacrosse
athletes in this study in which hamstring strength training was a targeted
priority.
Measures of lower body power were also significantly greater in the male players
compared to their female counterparts. Specifically, a “large”
statistically significant 27.4% difference was observed in countermovement
jump height, which was accompanied by a “very large” statistically
significant 28.5% difference in relative peak power and a 47%
difference in reactive strength. These findings are closely aligned with those
reported by Abian et al. [30] who found a 27%
difference in relative peak power and 27.8% difference in jump height
between males and females. However, the current study only focused on the outcomes
of the jump test (e. g. jump height and peak power output), future research
comparing male and female athletes in jump based assessments should to investigate
the differences in the phases of the jump through an in-depth force-time curve
analysis [31]. This information would help researchers
and practitioners understand the differing lower-limb force production strategies
between males and females, which in turn can inform training to enhance performance
and reduce the risk of injury.
Limitations
The results of this investigation need to be considered alongside its limitations.
First, this investigation was focused on the Men’s and Women’s
lacrosse teams from one university, and results may not be generalizable across all
Division I lacrosse athletes. Second, testing of physical qualities occurred in the
pre-competition phase of training and future research should incorporate the
assessment of lower limb isokinetic strength and power across multiple time points
within a periodized training plan. Third, a test of limb dominance was not conducted
and may have impacted the results.
Conclusions
Owing to the finding that left hamstring strength was significantly different between
contributing and non-contributing players within both the male and female cohort,
it
appears that strength in this muscle group may underpin an important aspect of
lacrosse performance (e. g. overhand shooting). However, future research in
this area is needed before a definitive conclusion can be made. Additionally, peak
power was significantly greater in the contributing male players compared to their
non-contributing counterparts highlighting power should be a targeted focus of
training programs. Interestingly, this finding was not observed within the
women’s cohort indicating that aspects of performance not related to
physical qualities may be more discriminative. The comparison of lower-limb force
production between male and female lacrosse athletes aligns with findings from
previous research. The isokinetic strength profile presented within this study can
be used to provide benchmarks to inform the rehabilitation process for collegiate
lacrosse athletes returning to play or for sports medicine practitioners screening
athletes for injury risk.
