COMPARISON OF TRUNK KINEMATICS IN TRUNK
TRAINING EXERCISES AND THROWING
DAVID F. STODDEN,1 BRIAN M. CAMPBELL,1 AND TODD M. MOYER2
Bowling Green State University, Bowling Green, Ohio; 2Jacksonville University, Jacksonville, Florida
ABSTRACT both performance outcomes and injury prevention (4,5,8,9).
These studies have also indicated that trunk contributions are
Strength and conditioning professionals, as well as coaches,
vital for both the demonstration of high throwing velocity
have emphasized the importance of training the trunk and the
and for improving throwing velocity within individual pitch-
beneﬁts it may have on sport performance and reducing the
ers. Thus, the notion of enhancing trunk performance char-
potential for injury. However, no data on the efﬁcacy of trunk
acteristics in throwing, via strength training, may augment
training support such claims. The purpose of this study was to the process of attempting to improve throwing velocity.
examine the maximum differential trunk rotation and maximum However, no research to date has examined the efﬁcacy of
angular velocities of the pelvis and upper torso of participants trunk training and its effects on throwing performance.
while they performed 4 trunk exercises (seated band rotations, Elite throwers generate high angular velocities at both the
cross-overs, medicine ball throws, and twisters) and compare pelvis (662 6 148°/s) and upper torso (1180 6 294°/s), and
these trunk exercise kinematics with the trunk kinematics dem- exhibit approximately 50–60° of differentiated rotation
onstrated in actual throwing performance. Nine NCAA Division I between the pelvis and upper torso (2,4,9). In general, more
baseball players participated in this study. Each participant’s advanced pitchers achieve higher pelvis and upper torso veloci-
trunk kinematics was analyzed while he performed 5 repetitions ties than less-developed pitchers (6). Additionally, increases
of each exercise in both dominant and nondominant rotational in ball velocity within pitchers are associated with in-
directions. Results indicated maximum differentiated rotation in creased pelvis and upper torso velocities (9). Theoretically,
increased pelvis and upper torso velocities would allow more
all 4 trunk exercises was similar to maximum differentiated
energy to be transferred from the trunk to the throwing arm,
rotation (approximately 50–60°) demonstrated in throwing per-
and eventually to the ball, which will lead to an increase in
formance. Maximum angular velocities of the pelvis and upper
ball velocity (9). Speciﬁc training that focuses on improving
torso in the trunk exercises were appreciably slower (approx-
both range of motion and velocities of the trunk would seem
imately 50% or less) than the angular velocities demonstrated to be important for augmenting throwing velocity. Further-
during throwing performance. Incorporating trunk training more, integrating speciﬁc trunk exercises that demonstrate
exercises that demonstrate sufﬁcient trunk ranges of motion similar ranges of motion and velocities produced in throwing
and velocities into a strength and conditioning program may may ultimately lead to higher throwing velocities. However,
help to increase ball velocity and/or decrease the risk injury. no research has addressed the idea of attempting to alter
KEY WORDS pelvis, upper torso, differentiated rotation, angular trunk kinematics via speciﬁc trunk training and determine its
effect on trunk performance characteristics and ball velocity.
Additionally, no study has examined trunk kinematics in
typical trunk training exercises that are implemented for
training purposes to examine their assumed efﬁcacy for
INTRODUCTION promoting a training effect. This directs us to the question:
Do current trunk training exercises demonstrate appropriate
trength and conditioning professionals routinely
discuss the importance trunk training and its effect pelvis and upper torso range of motion and velocities that
on performance among many different sports. More would be speciﬁc enough to promote improvements in
speciﬁcally, the importance of trunk strength and performance characteristics?
endurance in overarm throwing is suggested to be vital for The purpose of this study was to examine the maximum
differential trunk rotation and maximum angular velocities of
the pelvis and upper torso of athletes while they performed 4
Address correspondence to David F. Stodden, email@example.com. trunk exercises (seated band rotations, cross-overs, medicine
1533-4287/22(1)/112–118 ball throws, and twisters) and compare these trunk exercise
Journal of Strength and Conditioning Research kinematics with the trunk kinematics demonstrated in actual
Ó 2008, National Strength and Conditioning Association throwing performance.
112 Journal of Strength and Conditioning Research
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Trunk musculature important for throwing performance Procedures
include the rectus abdominis, external oblique, internal Testing was conducted during the middle of the participants’
oblique, and transverses abdominis. The roles of this competitive season. Participants wore spandex shorts and no
musculature in throwing are to promote dynamic stabiliza- shirts to aid in marking the correct anatomical landmarks.
tion, rotation, lateral bending, and ﬂexion/extension of the Retroreﬂective markers were placed bilaterally on the lateral
trunk. Improper training or a lack of training could lead to tip of the acromion process and the anterior superior iliac
muscle imbalances and injuries, not only to the trunk, but also spine of each participant. After completing the informed
to the upper extremities (10). In addition, appropriate training consent and health history forms, participants were taken
of the trunk musculature may help to improve sport through a general and speciﬁc warm-up. The speciﬁc warm-
performance. To optimize the contribution of the trunk in up included performing each of the trunk exercises to be
throwing, athletes must be able to effectively use energy tested.
generated by the trunk musculature and optimally transfer The pelvis vector was deﬁned by a line connecting the 2
that energy through their system (1). Maintaining a strong pelvis markers. The upper torso vector was deﬁned by a line
trunk may also decrease the force demanded by the connecting the shoulder markers. Maximum differentiated
musculature associated with the shoulder and elbow joints rotation was deﬁned by the maximum angle difference
to produce velocity (8,9). Applications of kinetic chain between the pelvis vector and upper torso vector in the XY
theory, neuromuscular contributions from stretch-shortening plane (transverse plane). Kinematic data were collected using
cycles, as well as proximal to distal sequencing all support the a 4-camera 3-dimensional video system (Motion Analysis
importance of training in a full range of motion for optimal Corporation, Santa Rosa, Calif.). Video data was sampled at
performance (3,5). 60 Hz. (Eva 7.0 software, Motion Analysis Corporation. Santa
Proper training of trunk musculature should focus on Rosa, Calif.). Maximum angular velocities of the pelvis and
increasing range of motion, strength, endurance, and velocity upper torso in the XY plane were calculated using Kintrac
potential (5). Training for maximum differentiated trunk software (Motion Analysis Corporation, Santa Rosa, Calif.).
rotation and maximum angular pelvis and upper torso Angular velocity of the pelvis was the cross product of the
velocity will help to develop increased force through a greater pelvis vector and its derivative. Angular velocity of the upper
range of motion (7). Increased forces generated by trunk torso was the cross product of the upper torso vector and its
musculature will likely produce higher trunk velocities and, derivative (Kintrac, Motion Analysis Corporation, Santa
more speciﬁcally, pitching velocities. This can be accom- Rosa, Calif.).
plished through sport speciﬁc training.
METHODS The 4 trunk exercises tested in this study represent different
types of trunk training exercises for promoting range of
Experimental Approach to the Problem
motion, rotational velocity, and explosiveness. The exercises
Pelvis and upper torso kinematics, including the amount of
were as follows: (i) seated band rotations, (ii) lying cross-over
differentiated rotation between the pelvis and upper torso and
crunches, (iii) standing medicine ball throws from the hip, and
maximum angular velocities, were examined in 4 speciﬁc
(iv) twisters. The purpose of the seated band trunk rotations
trunk training exercises and compared with pelvis and upper
and the lying cross-over crunches was to demonstrate
torso kinematics in throwing performance. Kinematics of
maximum range of motion within the limitations of the
trunk training exercises, to our knowledge, have not been
exercise and thus, demonstrate maximum differentiated
previously examined. These data may provide an estimation
rotation of the pelvis and upper torso. The purpose of the
of the efﬁcacy of trunk training exercises with respect to the
medicine ball throw was to produce the greatest horizontal
possibility of producing a speciﬁc training effect for improving
distance thrown. The purpose of the twister was to have the
subject rotate the trunk as quickly as possible while still
Subjects placing an emphasis on rotating the upper torso as much as
Nine NCAA Division I male baseball players (8 pitchers and 1 possible. Maximum differentiated trunk rotation was exam-
position player) participated in this study. The participants ined in all four exercises. Maximum upper torso velocities
average age was 19.7 6 1.0 yrs, height of 187.0 6 5.1 cm, and were calculated only for twisters and the medicine ball throw
a mass of 84.7 6 9.7 kg. Informed consent was obtained because they were the only 2 exercises where velocity was
before participation was allowed. All participants were healthy critical for performing the exercise. Maximum pelvis velo-
and had no training restrictions. Six of the participants were cities were examined only in the medicine ball throws because
right hand dominant, and 3 were left hand dominant. of the fact that the pelvis was primarily ﬁxed to the ground in
Dominance was deﬁned by the individuals throwing arm pref- the twister exercise. Participants performed the exercises in
erence. All participants had at least 1 year of training experience random order.
with the exercises, as they were included in their regular Seated band rotations required participants to hold the end
strength and conditioning training program at the University. of an exercise band that was tied around a ﬁxed object and
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Kinematics of Trunk Exercises
rotate the trunk (Figure 1). The participant’s elbows remained The twister required participants to sit on the ground with
fully extended in front of his body and parallel to the the torso at approximately 60° to the ﬂoor with the feet
ground throughout the exercise. From this initial position, approximately 10–15 cm off the ground and the knees bent
participants rotated the upper torso as far as possible away approximately 90° (Figure 4). Participants held a 4.5-kg plate
from the ﬁxed object, thus increasing the tension of the on their chest with both hands. Participants were then told to
band as it lengthened. Participants proceeded to rotate rotate their upper body as far and as fast as possible from side
the trunk back into the starting position and performed to side for 5 complete rotations.
the movement again until 5 repetitions were completed. All data were averaged and categorized into dominant and
Individuals also performed the exercise 5 times in the nondominant rotational directions based on each partic-
opposite direction. ipant’s dominant throwing arm. Average maximum differen-
Lying cross-over exercise required participants to lie in tiated rotation for band rotations, cross-overs, and twisters
a supine position on the ground (Figure 2). To perform right were presented as dominant and nondominant directions.
directional rotation, the subject’s left foot was ﬂat on the Dominant rotation in the exercises for left-handed throwers
ground with the left knee bent approximately 90° and the was band trunk rotations to the right, cross-over to the right,
right ankle was placed over the ﬂexed left knee. The right arm and twisters to the right. Dominant rotation in the exercises
was ﬂat on the ground beside the right hip and the left hand for right-handed throwers was band trunk rotations to the left,
was placed behind the head. From this position, participants crossovers to the left, and twisters to the left. Differentiated
performed the exercise by touching the left elbow to the right rotation for the medicine ball throws are presented as
knee and then returned to the starting position while the left preparatory (countermovement) and throwing movement
hand remained behind the head. Individuals were instructed directions. For right-handed throwers, the preparatory
to rotate as far as possible keeping the right knee stationary. movement was right rotation and the throwing direction
This exercise was completed 5 times in one direction. was left rotation. For left-handed throwers, the preparatory
Participants then completed the exercise 5 times in the movement was left rotation and the throwing direction was
opposite direction. right rotation. Maximum pelvis and upper torso angular
Standing medicine ball throws required participants to velocities for the medicine ball throws were calculated only in
hold a medicine ball at mid-chest level (Figure 3). From this the throwing direction. Maximum upper torso angular
position, participants were instructed to rotate the body velocities for the twister were calculated for both rotational
away from the directed line of the throw, producing movement directions.
a countermovement, then rotate in the opposite direction
and throw the medicine ball for maximum horizontal
distance. Additional instructions were to keep the elbows RESULTS
extended and maintain shoulder ﬂexion at approximately Descriptive statistics for average maximum pelvis and upper
mid-chest height. Participants were told to throw the torso differentiated rotation and average maximum pelvis
medicine ball with maximum effort. Medicine balls ranged and upper torso angular velocities are presented in Figures 5
in mass from 3.7–4.5 kg. This exercise was performed and 6. Intraclass correlation coefﬁcients were calculated
5 times in each direction. to determine the internal consistency of all measures.
Figure 1. Seated band rotation (A = beginning, B = maximum rotation).
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Figure 2. Lying cross-over (A = beginning, B = maximum rotation).
The calculated values for all measures were between 0.8963 elicited the least amount of trunk rotation (dominant = 45.2 6
and 0.9913. 7.1°, nondominant = 47.0 6 9.2°). Medicine ball throws
Of the 4 exercises tested, seated band rotations produced demonstrated 50 6 7.6° (dominant prep), 55.2 6 9.2°
the greatest amount of differential trunk rotation (dominant = (nondominant prep), and 50.2 6 7.2° (dominant follow
61.6 6 6.8°, nondominant = 59.4 6 7.5°) and cross-overs through), 43.9 6 8.9° (nondominant follow through) of
Figure 3. Medicine ball throw (A = starting, B = preparatory, C = ball release, D = follow through).
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Kinematics of Trunk Exercises
Figure 4. Twister (A = starting, B = left, C = right).
maximum differential trunk rotation, whereas the twisters ball throws achieved greater differential trunk rotation than
demonstrated 52.8 6 12.3° (dominant) and 54.3 6 16.4° the cross-overs. Therefore, cross-overs were determined to be
(nondominant) of maximum differential trunk rotation. the least effective of all 4 exercises with respect to maximum
A second purpose of the twisters and medicine ball throws differentiated rotation. However, because trunk motion in
was to obtain maximal trunk angular velocity (Figure 6). throwing is multiplanar, the crossover exercise exhibits
Average maximum upper torso angular velocities for the motion that corresponds to similar trunk movement
twisters were 436.7 6 101.9°/s (dominant), 415.5 6 85.5°/s demonstrated in throwing. Overall, all of the exercises tested
(nondominant). The average maximum angular velocity of produced range of motion that was similar to the range of
the upper torso while performing the medicine ball throw motion produced in throwing performance and seem
was 493.7 6 45.0°/s (dominant) and 450.7 6 61.6°/s sufﬁcient to promote the range of motion necessary for
(nondominant). The average maximum angular velocity of throwing performance capabilities.
the pelvis while performing the medicine ball throw was Research conducted with elite baseball pitchers has
293.6 6 73.5°/s (dominant) and 301.6 6 64.6°/s demonstrated upper torso angular velocities of approximately
(nondominant). 1100 to 1300°/s during the pitching motion (2,6,9). These
same studies have also indicated that the pelvis achieves
DISCUSSION maximum angular velocities of approximately 500 to 700°/s.
Results of this study show that maximum upper torso angular
The purpose of this study was to examine the maximum velocities in the exercises where the primary goal was trunk
differential trunk rotation and maximum angular velocities of velocity or explosiveness were less than 50% of maximum
the pelvis and upper torso in athletes while they performed 4 upper torso angular velocities exhibited in throwing
trunk exercises (seated band rotations, cross-overs, medicine performance. Maximum pelvis angular velocities in the
ball throws, and twisters) and compare these trunk exercise
kinematics with the trunk kinematics that are demonstrated
in actual throwing performance.
Previous studies have indicated that pitchers demonstrate
maximum differentiated trunk rotation of approximately
47–60° (4,9). Results of this study indicated all 4 trunk exer-
cises demonstrated differential rotation that approximated the
differentiated rotation in throwing performance. The cross-
overs produced the least amount of differentiated trunk rota-
tion of all the exercises tested. This was probably caused by
the anatomical restrictions when performing a cross-over.
The anatomical structure of the vertebrae most likely limited
the amount of rotation within the vertebral column when the
Figure 5. Maximum pelvis and upper torso differentiated rotation. DCO =
spine was ﬂexed. dominant Cross-Over, NDCO = nondominant cross-over, DT = dominant
The goal of the twister exercise was to obtain maximum twister, NDT = nondominant twister, DBR = dominant band rotation,
upper torso velocity and the goal of the medicine ball throw NDBR = nondominant band rotation, MBDP = medicine ball, dominant
preparatory, MBNDP = medicine ball nondominant preparatory, MBDF =
was to produce maximum horizontal distance; thus, the focus medicine ball dominant follow-through, MBNDF = medicine ball non-
of these 2 exercises was not necessarily on maximizing dominant follow-through.
differentiated rotation. However, both twisters and medicine
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an estimate of the effects of adding mass to the distal aspects
of the kinetic chain system and increasing the distance from
the axis of rotation. The twisters represented a somewhat
different type of exercise than the ballistic medicine ball
throw, but the emphasis on rotational velocity remained the
goal. The increased mass that individuals held at their chest
probably affected the velocity of the movement simply
because of the increased inertial properties, but the repetitive
movement of rapidly accelerating and decelerating the trunk
may have resulted in a more controlled movement, as
compared with the ballistic throw. Thus, the ability to
Figure 6. Maximum pelvis and upper torso velocities. TD = twister generate maximal velocity with successive directional changes
dominant, TND = twister nondominant, MBD = medicine ball dominant,
MBND = medicine ball nondominant. was constrained.
When assessing the efﬁcacy of a training program for
athletes where throwing or striking is important, understand-
ing the purpose of the exercises implemented should be
medicine ball throws were approximately 50% as compared addressed. Is the purpose of the trunk training exercises to
with what is demonstrated in throwing performance. maintain or promote increased trunk strength, increased
Two aspects of the trunk training exercises that most likely ROM, increased stability, increased endurance, or increased
affected the trunk angular velocities in the explosive medicine explosiveness? The results of this study provide some
ball throws were the masses of the medicine balls used, which compelling results as to what the exercises may provide in
were between 3.7 kg and 4.5 kg (8–10 lbs) and the nature of terms of a training effect. If the purpose of these exercises and
the movement where the arm are extended in front of the many exercises similar to the ones tested in this study were to
body at approximately mid-chest height. The medicine ball improve ROM, endurance, or stability, then these exercises
masses were chosen because they are typical masses that are would seem to be appropriate. However, if the purpose of
used in explosive type training. This mass, along with the the exercises is to promote enhanced trunk rotational velocity
nature of the movement where the mass is approximately 36 or power that would be speciﬁc to throwing or striking
to 46 cm away from the trunk, would most likely lead to an performance, perhaps these exercises (speciﬁcally, the twist-
increase in muscle stiffness within the trunk and upper ers and medicine ball throws) are not as appropriate as they
extremities throughout the entire movement. This would need to be. Utilizing smaller masses of medicine balls or
occur to both maintain the height of the medicine ball external objects may provide the necessary reduction in
throughout the entire range of motion (ROM) of the exercise inertial characteristics, thus promoting the capability for
and to compensate for the increased inertial forces associated enhanced rotational velocity during these types of exercises.
with the mass of the medicine ball, distance from the trunk
axis of rotation, and acceleration and deceleration aspects PRACTICAL APPLICATIONS
of the countermovement and acceleration phases of the In summary, the trunk training exercises tested in this study
exercise. In throwing, the body compensates for (i.e., demonstrated differentiated trunk rotation similar to what is
temporarily reduces) these inertial characteristics by ﬂexing demonstrated in throwing performance. However, maximum
the elbow during the windup phase of throwing, which pelvis and upper torso angular velocities exhibited in the trunk
reduces the moment of inertia about the longitudinal axis of exercises were generally 50% or less than what is demon-
the trunk. The body also reduces the inertial effect of the strated during throwing performance. These results suggest
upper extremity during trunk rotation through the passive that more careful consideration, relating to the speciﬁc goal
external rotation at the glenohumeral joint during the arm of exercises, should be given when developing a training
cocking phase of throwing, which is where the pelvis and program for sports that speciﬁcally include throwing and
upper torso reach maximum angular velocities. striking (e.g., baseball, softball, and tennis). Incorporating
The effect of increased mass and size of balls thrown on trunk exercises into training programs that promote greater
pelvis and upper torso angular velocities between football differentiated trunk rotation and greater trunk angular
throwing and baseball pitching suggests the same pattern of velocities that are similar to the sport movement may help
decreasing angular velocities as demonstrated in these results to promote increases in throwing velocity. Speciﬁcally,
(2). Fleisig et al. (2) showed that pelvis angular velocities exercises that promote explosive trunk rotation, including
decreased approximately 24% (660°/s vs. 500°/s) and upper torso twists with a partner (i.e., Russian twists) or explosive
torso angular velocities decreased approximately 19% medicine ball explosive throws (as portrayed in the ﬁgures),
(1170°/s vs. 950°/s) when comparing baseball pitching and would seem to be the most appropriate exercises to
football passing. Although the medicine ball throw in this speciﬁcally enhance trunk rotational velocities. The focus of
study is not similar to the actual throwing motion, it provides these ballistic throw type exercises should be directed
VOLUME 22 | NUMBER 1 | JANUARY 2008 | 117
Kinematics of Trunk Exercises
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