ANEXAMINATION OF TRAINING ON THE VERTIMAX
RESISTED JUMPING DEVICE FOR IMPROVEMENTS
IN LOWER BODY POWER IN HIGHLY TRAINED
MATTHEW R. RHEA,
MARK D. PETERSON,
JEFF R. OLIVERSON,
FERNANDO NACLERIO AYLLO
AND BEN J. POTENZIANO
Department of Interdisciplinary Health Sciences, AT Still University, Mesa, Arizona;
Department of Exercise Science,
Mesa Community College, Mesa, Arizona;
European University of Madrid, Madrid, Spain;
San Francisco Giants, San Francisco, California
Training to develop superior muscular power has become a key
component to most progressive sport conditioning programs.
Conventional resistance training, plyometrics, and speed/agility
modalities have all been employed in an effort to realize super-
lative combinations of training stimuli. New training devices
such as the VertiMax resisted jump trainer are marketed as
a means of improving lower body reactive power. The purpose
of this study was to evaluate the effectiveness of the VertiMax,
in combination with traditional training modalities, for improve-
ments in lower body power among highly trained athletes. Forty
men and women Division I collegiate athletes representing the
sports of baseball, basketball, soccer, gymnastics, and track
completed a 12-week mixed-methods training program. Two
groups were constructed with both groups performing the
same conventional resistance training and strength training
exercises. The training control group performed traditional plyo-
metric exercises while the experimental group performed similar
loaded jump training on the VertiMax. Lower body power was
measured before and after the training program by the TENDO
FiTROdyne Powerlizer and statistically compared for differ-
ences between groups. Data analyses identiﬁed a signiﬁcant
(p,0.05) and meaningful difference between power develop-
ment among the 2 groups, with the VertiMax eliciting a greater
treatment effect (effect size = 0.54) over conventional
resistance and plyometric training alone (effect size = 0.09).
These data convincingly demonstrate that the VertiMax repre-
sents an effective strategy for developing lower body power
among trained college athletes, when combined with traditional
strength and conditioning approaches.
KEY WORDS VertiMax, plyometric exercise, power, speed,
For all athletes, the ability to transfer training-
induced physiological adaptations to performance
in skill-related activity is essential for optimal func-
tioning, injury reduction, and competitive success.
Just as inferior skill limits the extent of athletic succession, for
today’s aspiring athlete, inferior physical ﬁtness will handicap
even the most skilled individual. Clearly, the extent to which
ﬁtness inﬂuences performance is fundamentally distinctive.
For some sports, physical conditioning and athletic practice
are synonymous, as ability is dictated principally by ﬁtness
capacities (i.e., marathon running, sprint cycling, power
lifting). In contrast, many other activities are characterized by
a diverse multidimensional set of physiological competencies,
underscoring the importance of speciﬁc, effectual training
modalities. By combining the appropriate training stimuli
with the appropriate quantity and quality of skilled move-
ment, coaches and sport performance specialists may col-
laborate to optimize training efﬁciency and elicit the most
In combination with quality of movement, training to
stimulate muscular adaptation for peak power output resides
as a principal developmental objective. Collegiate athletes are
traditionally introduced to explosive lifting early in the off-
season as an adjunct to important functional and conventional
power lifting exercises. Ultimately, the inclusion of explosive
lifting as a primary training tenet is done to stimulate neu-
romuscular adaptation, supporting the development and
enhancement of muscular rate of force development and peak
power. This customary training agenda manifests as a shift in
Address correspondence to Matthew R. Rhea, email@example.com.
Journal of Strength and Conditioning Research
Ó2008 National Strength and Conditioning Association
VOLUME 22 | NUMBER 3 | MAY 2008 | 735
emphasis from training the basic force production capacities
of muscle, to developing muscular contraction velocity and
movement speed, and ultimately to preparing the musculo-
skeletal system for performance in powerful athletic events.
However, despite proven efﬁcacy to promote such specialized
adaptations, many professionals have abandoned traditional
explosive lifting techniques, citing safety concerns, and/or
inefﬁcient time expenditure.
In an effort to supplement/replace traditional approaches,
various training technologies and prescription innovations
have been devised to elicit similar muscular power adaptation.
Lower load, high-speed training has gained considerable
popularity among professionals, as well as the sport science
community. Although the recommendation to train with
high speed is not a novel approach, little is known about the
optimal implementation strategy. One technique, in partic-
ular, loaded jump training, has received considerable interest,
as of late (9). Conceivably, overloading a vertical jump may
be a superior means for development of rate of force produc-
tion and peak power output, as execution is not heavily
contingent on technique, thus enabling athletes of various
backgrounds to productively train. Many research investi-
gations have supported the use of jump training modalities,
demonstrating signiﬁcant enhancements in peak power
output, jumping ability, sprint acceleration, rate of force
development, and general strength-power proﬁles (9).
Albeit popular for overloading high-velocity concentric
muscle actions and reducing technique vulnerabilities, loaded
jump training may be similarly valuable for development of
muscle eccentric deceleration. Most often considered a pro-
tective barrier to injury, coordinated eccentric muscular
recruitment is also a fundamental requisite for jumping ability
(9). Case in point, during the countermovement phase of
a jump (i.e., the transition phase from eccentric to concentric,
otherwise known as the amortization phase of a plyometric
movement), stored elastic energy from the prestretched
muscle is transferred to optimize mechanical recoil of the
musculotendinous unit. By deliberately accentuating the
eccentric deceleration phase of a multijoint movement, spe-
cialized training interventions may be designed to induce
neuromuscular adaptations in the stretch-shortening cycle
(SSC), supporting both voluntary activation and inhibitory
and/or facilitatory reﬂexes (2). Collectively, these neural
adaptations may support enhanced mechanical efﬁciency of
jumping (1,3,13–16), improved muscle-activation patterning
and dynamic joint stability (4), and increased agonist muscle
innervation through the stretch reﬂex (5,6,12,17), leading to
increased joint moments, greater ground reaction force, and
superior jumping ability (11).
Seemingly, the beneﬁts of loaded jump training have far-
reaching implications for preparing athletes to compete in
similar dynamic activities. However, many dynamic move-
ments rely on explosive contractions involving longer concen-
tric actions than experienced during brief SSC movements,
and may be limited by the ability of the muscle to produce
force during fast contraction velocities (18). Evidence has
suggested that combining heavy resistance training with
high-speed exercises may be the optimal technique for elic-
iting neuromuscular adaptation to support both the stretch
reﬂex and rate of force development, as well as for improve-
ment in a variety of performance variables concerned with
maximal strength and power (8). Independently, heavy-
resistance–low-velocity training as well as low-resistance–
high-velocity training may effectively generate improve-
ments at the high force end of the force-velocity curve and
toward the high-velocity end of the force-velocity curve,
respectively. In combination, it is plausible that training for
strength and speed may elicit a powerful synergistic effect,
and maximize neuromuscular development for peak power
output and explosive athletic performance.
Failure to optimize each of the basic force-producing
characteristics of the neuromuscular and musculoskeletal
systems may diminish the developmental potential of mus-
cular power adaptation and expression across a continuum of
high-force and high-speed movements. Speciﬁcally, the
combination of various training methods to elicit a maximal
transference in power output is critical for explosive athletes.
Of particular importance to advanced trainees such as col-
legiate athletes, a progression in specialized stimuli to accom-
pany increased training experience is essential to sustain
continued adaptation (19,21,23). As athletes become more
highly trained, the stimulus applied during conditioning must
increase to continue to overload the neuromuscular system
and elicit a training adaptation. The development of training
aids to enable this progressive overload is an industrious
pursuit. While many such aids are currently marketed, few
have demonstrated effectiveness among athletic populations.
The purpose of this investigation was to examine the effects
of a concurrent mixed-methods training protocol (i.e., tra-
ditional power lifting and explosive lifting) supplemented
with loaded jump training using the VertiMax (VMax) resisted
jump training device compared to a traditional resistance/
plyometric training regimen on jumping ability and peak
power output in collegiate athletes. The VMax (Figure 1) is
a platform-based device with bungee attachments for the
waist, hands, and thighs. Strategic placement and adjustment
of bungee resistance allow for the performance of plyometric
jumping exercises with resistance added.
Experimental Approach to the Problem
Highly trained, NCAA Division I collegiate athletes from
various sports were recruited and assigned to either a standard
mixed-methods training program or a standard training
program plus loaded jump training. Although the men and
women athletes were from different sports and involved in
speciﬁc conditioning programs, both treatments were equally
represented for each involved sport subgroup. The assigned
treatments consisted of a 12-week intervention during each
Journal of Strength and Conditioning Research
VertiMax Jump Training
athlete’s respective off-season, which ultimately coincided
with the basic strength and strength/power phases of
training, respectively. Before and after the training inter-
ventions, athletes were tested on vertical jumping ability and
peak power output in order to assess the effectiveness of
treatment strategy, as well as the differences between groups.
Forty Division I collegiate athletes (n=26men,n=14women)
representing the sports of baseball, gymnastics, soccer, and
basketball were recruited for this 12-week training intervention
study. Before baseline testing, athletes were assigned to 1 of
2 groups: VMax group or training control (TCo) group.
Because there were slight variations in training programs for
each different sport, groups were composed equally of athletes
from each particular sport to protect against a confounded
experimental affect derived through differences in training.
Athletes from each sport were randomly assigned to a respec-
tive group, ensuring that equal numbers of athletes from a given
sport were placed in each group. Therefore, the only difference
in training across the 2 groups was the inclusion of resisted
jumping exercises on the VMax device. Both groups were
composed of 13 men and 7 women, each of whom committed
to adhering to the training protocol and refraining from per-
forming alternative or supplemental workouts. Compliance
with training was monitored by the researchers and strength
and conditioning staff responsible for training sessions. While
athletes in both groups missed training sessions, exclusion
criteria for analyses was set at anything in excess of 2 missed
workouts, over the entire 12-week training intervention;
however, no athlete met such criteria.
Lower body peak power was identiﬁed through the use of
the TENDO FiTROdyne Powerlizer (Fitro-Dyne; Fitronic,
Bratislava, Slovakia) according to protocols suggested by
Jennings et al. (10). Athletes weighed-in immediately prior to
performing a maximal countermovement jump test. In order
to effectively test power output during the counter move-
ment vertical jump, the TENDO unit cord was attached to
the back waistband of each subject’s athletic shorts. This
arrangement allowed for the base of the TENDO FiTRO-
dyne unit to be positioned on the ﬂoor behind the athlete
during the test, in such a way that valid readings could be
obtained without impeding jump technique and/or perfor-
mance. In order to calculate power output in watts, each
athlete’s body mass was imported into the Fitrodyne
microcomputer. The TENDO unit proﬁciently computed
PP according to the speed of movement in the concentric
phase of the jump test, as well as each respective athlete’s
body mass. Certiﬁed strength and conditioning specialists
and investigators oversaw all testing processes to ensure
proper technique and safety (7).
Both groups performed similar training programs composed
of free weight resistance training with lower body compound
exercises (e.g., back squat, powercleans, standard deadlifts,
dumbbell walking lunges, and Romanian deadlifts) (Table 1).
Figure 1. The VertiMax.
TABLE 1. Lower body exercises performed during
Resistance exercises (2–3 dwk
sets total, 80–90% 1RM)
Dumbbell walking lunges
Sprint and plyometric exercises (1–2 dwk
10–15 repetitions per exercise)
20–40 yd sprints
Front/side hurdle jumps
Additional exercises performed by the VertiMax
training group (1–2 dwk
Resisted quarter jumps: 2–4 sets, 8–10 jumps
Resisted half jumps: 2–4 sets, 5–10 jumps
Resisted split jumps: 2–4 sets, 5–10 jumps
VOLUME 22 | NUMBER 3 | MAY 2008 | 737
Journal of Strength and Conditioning Research
In conjunction with traditional resistance training, the TCo
group also performed running and plyometric drills, includ-
ing variable-distance sprints, split-squat jumps, variable-
height depth-jumps, and hurdle-jumps. Athletes from both
treatments followed a periodized training program with resis-
tance exercises performed 2–3 days per week, and sprint/
plyometric (TCo group) or sprint/VMax (VMax group)
training 1–2 days per week, for 12 total weeks. Volume of
resistance training exercises averaged 8 sets per muscle group
at a mean intensity of 80–90% of 1-repetition maximum
(1RM) (19,25). These training values were selected because
they have been shown to be the most operational com-
bination of training stimuli for eliciting maximal strength
among athletic populations (20). Sets and repetitions for each
exercise were periodized in daily undulating (24) fashion.
In addition to the traditional compound lower body lifts
and equated sprint work, the VMax group performed sup-
plementary exercises on the VMax V-6 training apparatus
(Genetic Potential; Tampa, Fla.). The VMax is a platform-
based unit complete with adjustable bungee chords that can
be attached to a waist belt worn by an athlete. To further
overload each movement, hand straps connected to bungee
chords were worn by all study athletes, allowing accentuated
resistance on the arm swing phase and spinal extension during
all jumping movements. Resistance on the bungee chords was
adjusted to apply more or less resistance when needed.
The 3 supplementary exercises performed by all subjects in
the VMax group were half squat jumps, quarter squat jumps,
and split squat jumps. Half squat jumps involved performing
8–10 jumps with a slight pause between each rep, while
quarter squat jumps were 5–10 jumps done repetitively with
no pauses. Depth of the countermovement for each of the
VMax-resisted squat jump exercises (i.e., half and quarter
squat jumps) was left to the discretion of the individual athlete
and depended on personal jumping technique; however, no
dramatic differences were observed between participants.
Spilt squat jumps were performed by instructing each
athlete to assume a deep lunge position with a ﬂexed knee and
hip of the lead leg and fully extended hip of the trail leg. At his
or her discretion, each athlete then jumped as high as possible
(i.e., vertically) and, while in the air, switched the position of
each leg to decelerate in the oppositely situated lunge
position. Multiple repetitions were performed as quickly as
possible with no rest between
each jump. For all loaded jump
exercises on the VMax, resis-
tance on the bungee chords
was progressively increased
over the duration of 12 weeks
to provide appropriate pro-
gression in stress. Training
sessions on the VMax appara-
tus took place in groups of 4
athletes. After performing the
assigned number of repetitions,
an athlete would be disconnected from the chords and
directed to the end of the line, while the next athlete assumed
his or her place on the platform. This sequence resulted in
approximately 2 minutes of rest between each set of like
exercises on the VMax and approximately 5 minutes between
different loaded jump exercises. Two to 3 sets of each exercise
Descriptive data (mean and SD) for the various tests were
computed. At pre-test, the TCo group demonstrated sig-
niﬁcantly lower power (2211.10 W) than the VMax group
(p,0.05). Therefore, change in power from pre- to post-
testing was calculated and analyzed by independent samples
t-test. Level of statistical signiﬁcance was set at p#0.05, with
meaningfulness of differences determined by the use of effect
sizes (ESs). Effect sizes were calculated by determining the
difference between pre- and posttest means, divided by the
pretest SDs and interpreted according to a scale previously
proposed by Rhea (22).
Descriptive statistics from pre- and post-testing are shown in
Table 2. The average improvement in power observed in the
TCo group (+16.25 642.67 W) resulted in a very small ES of
0.09, which did not reach statistical signiﬁcance (p.0.05).
The increase in power in the VMax group (+109.15 6107.69 W)
represented a moderate ES of 0.54 and was found to be
statistically different (p,0.05) from pretest power. Improv-
ement in power following training was found to differ
between groups (p,0.05) in favor of the VMax group (+92.9
These data clearly demonstrated an added beneﬁt of per-
forming loaded jump training exercises on the VMax appa-
ratus in conjunction with traditional preparatory strength and
conditioning modalities, when compared to strength/power
training alone. The large difference in power improvement
is quite substantial when considering that baseline power
measures in the VMax group were signiﬁcantly higher than
those of the TCo group. Certainly, it was expected that sig-
niﬁcantly greater initial peak power capacities could result in
TABLE 2. Results.
Group Pre-test (W) Post-test (W) Improvement ES
TCo 986.45 6176.11 1002.70 6187.88 +16.25 642.67 0.09
VMax 1197.55 6202.47* 1306.70 6188.67* +109.15 6107.69* 0.54*
ES = pre/post effect size; TCo = control group; VMax = VertiMax group.
*Groups differ at P,0.01.
Journal of Strength and Conditioning Research
VertiMax Jump Training
an overall diminished comparative test-retest improvement
for the VMax group; according to the principle of diminishing
returns. However, such an expectation was not realized at the
completion of the intervention and post-test, lending even
further support to the effectiveness and practical application
of this training device.
Comparing the improvements in power observed in the
current study to a recent study by Hoffman et al. (9) involving
resisted jump training on the Cormax Jump Squat Device
(Cormax Strength Power Systems, Valley City, ND), the
VMax group in the current study exceeded improvements in
lower body power (ES = 0.54) compared to both inter-
vention groups in the Hoffman et al. study (ES = 0.49 and
0.22, respectively). Therefore, it may be concluded that train-
ing on the VMax not only enhances lower body power
improvements compared to conventional resistance training
and plyometrics, it also exceeds the beneﬁts observed with
other resisted jump training devices on the market.
Due to the lack of biometric data acquired during this study,
physiological explanations for the ﬁndings will remain strictly
theoretical. Perhaps such speculation may lead to future
research and improved knowledge in this area. Certainly,
numerous physiological factors inﬂuence rate of force devel-
opment and muscular power output, 2 of which include
activation of muscle tissue and synchronization of ﬁber
recruitment. Recruitment of larger numbers of motor units
and synchronizing their activation would result in much
greater force development in a rapid fashion. Thus, such
adaptations would greatly enhance power output. It is
possible that training on the VMax resulted in greater adap-
tations in such areas. Subsequent research is needed, however,
using EMG measures to verify such a hypothesis.
While strength training and plyometric exercise have been
shown to increase power among athletes, as an individual
becomes more highly trained, the resultant adaptation to
training diminishes. The athletes employed in this study were
very accustomed to conventional sports conditioning meth-
ods as was used by the TCo group. Each athlete had
performed plyometric-type exercises for at least 2 years.
Basketball players and gymnasts in particular are quite
accustomed to performing jumps with only their body
weight as resistance. In such cases, conventional plyometric
exercises are unlikely to provide signiﬁcant amounts of
overloading stimuli to the neuromuscular system. A unique
quality of the VMax apparatus is in the ability to apply
progressive resistance to plyometric jumps. The added resis-
tance, along with the capacity to alter and progress the resis-
tance over time, may certainly be used to enhance the
stimulation of the neuromuscular system and to elicit
adaptations in the areas of activation and synchronization.
Performance of resisted jump exercises on the VMax has been
shown to have a positive effect on power development among
well-trained collegiate athletes. In an arena where maximal
power adaptations are considered necessary, inclusion of such
training to supplement conventional strength and power
training will result in signiﬁcantly greater adaptations. Supe-
rior performance enhancement and injury reduction may be
expected with the incorporation of the VMax apparatus over
other alternatives of jump training. The functional mecha-
nisms responsible for these beneﬁts are as a result of the
versatility of movement that the VMax permits and the
unique capacity to exaggerate jump landing/movement
deceleration as well as the unrestricted ability to progressively
overload the training stimulus.
One VertiMax V-6 unit was provided by Genetic Potential for
this research. No other support, ﬁnancial or other, was
provided by this company nor have the authors received any
compensation related to this research.
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VertiMax Jump Training