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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,     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.
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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.
                                                                      Trunk Exercises
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
throwing velocity.
                                                                      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

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Kinematics of Trunk Exercises

towards rotational velocity; thus, a possible way to address                  baseball pitching and football passing. J Appl Biomech 12: 207–224,
this specific focus may be to decrease the mass of the medicine
balls used.                                                                3. Herring, RM and Chapman, AE. Effects of changes in segmental
                                                                              values and timing of both torque and torque reversal in simulated
   On the basis of the results of the limited number and types                throws. J Biomech 25: 1173–1184, 1992.
of exercises included in this study, it would seem that most               4. Hong, D and Roberts, EM. Angular movement characteristics of the
trunk training exercises generally used in strength and                       upper trunk and hips in skilled baseball pitching. In: Biomechanics in
conditioning programs would demonstrate sufficient differ-                     Sports XI: Proceedings of the XI Symposium of the International Society of
                                                                              Biomechanics in Sports 338–343, 1993.
entiated trunk rotation, but an emphasis in these exercises
                                                                           5. Ishida, K and Hirano, Y. Effects of non-throwing arm on trunk and
should include the production of maximum range of motion.                     throwing arm movements in baseball pitching. Int. J Sport Health Sci
In addition, generating more energy in the trunk may                          2: 119–128, 2004.
decrease the risk of injury by decreasing the relative contri-             6. Matsuo, T, Escamilla, RF, Fleisig, GS, Barrentine, SW, and Andrews, JR.
bution of shoulder and elbow musculature that would                           Comparison of kinematic and temporal parameters between
                                                                              different pitch velocity groups. J Appl Biomech 17: 1–13, 2001.
demanded to compensate for the lack of optimal lower
                                                                           7. Neal, RJ, Snyder, CW, and Kroonenberg, PM. Individual differences
extremity involvement. Further assessment of trunk training
                                                                              and segment interactions in throwing. Human Movement Sci 10: 653–
exercises and the effects of training on performance is                       679, 1991.
warranted.                                                                 8. Stodden, DF, Fleisig, GS, McLean SP, and Andrews, JR. Relation-
                                                                              ship of biomechanical factors to baseball pitching velocity: Within
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