Volume 5- Issue 4: 2018

ISSN: 2574-1241
DOI: 10.26717/BJSTR.2018.10.002022
Hitoshi Koda. Biomed J Sci & Tech Res

Research Article

Open AccessInfluence of Muscle Fatigue on Three-Dimensional
Scapular Kinematics During Repeated Arm Elevation
Hitoshi Koda*1, Yoshihiro Kai2, Noriyuki Kida3, Shin Murata2, Yuichiro Miura4, Hideaki Fukushima4 and Toru
Morihara5
1

Department of Rehabilitation, Faculty of Health Science, Kansai University of Welfare Sciences, Japan2

Department of Physical Therapy, Faculty of Health Science, Kyoto Tachibana University, Japan

3

Graduate School of Science and Technology, Kyoto Institute of Technology, Japan

4

Rehabilitation Unit, Fushimi Okamoto Hospital, Japan

5

Department of Orthopedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Japan

Received:: Octobet 27, 2018; Published:: November 09, 2018

*Corresponding author: Hitoshi Koda, Department of Rehabilitation, Faculty of Health Science, Kansai University of Welfare Sciences,Japan
Abstract
Previous studies have reported that shoulder fatigue leads to scapular dyskinesia and increased mechanical stress. However, none reported theeffect of fatigue resistance. To investigate the effect of fatigue resistance on scapular kinematics during repeated arm elevation. Seventeen healthy
participants carried out repeated arm elevation with a dumbbell in the scapular plane at the elbow extension position. Using an electromagnetic
tracking device, the angle of the scapular upward rotation, scapular posterior tilting, and scapular external rotation were measured. Arm elevation
data were interpolated into 100 frames; the first elevation (0%), 25% of iteration count, 50%, 75%, and the final elevation (100%) were analyzed.
There was a significant increase in the scapular upward rotation angle between the 100% and 0% iteration count, and a decrease in the scapular
posterior tilting angle at 75% and 100%, compared with 0%. There was no significant effect of the condition on the scapular external rotation angle.
Muscle fatigue by repeated arm elevation increased the upward rotation angle, which was maintained until just before complete exhaustion. The
decrease in the posterior tilting angle was observed before (when the iteration count exceeded 50%) the increase in the upward rotation angle.
Keywords: Scapular Dyskinesia; Arm Elevation; Repeated Movement; Fatigue ResistanceIntroduction
The shoulder joint contributes towards the movement of theupper limbs; however, it has poor stability and is easily prone to
injury [1]. Shoulder injuries are common in overhead athletes,with as many as 44% experiencing shoulder problems and 29%
having shoulder pain at some point in their career [2]. The highprevalence of shoulder pain in these athletes is attributed largely torepetitive and excessive stress placed on the shoulder. In this year’sWorld Baseball Classic, repetitive stress due to more pitching was
regarded as a problem and introduced the pitcher use limitation
rules.
Scapular dyskinesia is one of the factors to increase mechanicalstress in the shoulder joint [3-5]. Willmore et al. [5] showed thata decrease in scapula upward rotation and posterior tilting occur
when there is an increase in the compressing and shearing force
under the surface of the acromion. Sanchez et al. [6] found that the
Biomedical Journal of
Scientific & Technical Research (BJSTR)

ratio of scapular dyskinesia in the shoulder pain group was higher
than that in the pain-free group. The reported scapular dyskinesia
is related to an increase in mechanical stress or shoulder injuries.

Scapular dyskinesia is caused by muscle weakness or trunk
misalignment [7,8]. On the other hand, fatigue of the shoulder
muscles due to repetitive and prolonged overhead sports activity
also appears to temporarily alter the scapular kinematics [9-13].
Ebaugh et al. [9] found post-fatigue scapular kinematic alterations,with increased scapular upward rotation and clavicular retraction in
the mid ranges of arm elevation. Chopp et al. [11] showed decreased
scapular posterior tilting and increased scapular external rotation
after a fatiguing task. Thus, previous studies reported that shoulder
fatigue leads to scapular dyskinesia and increased mechanicalstress; however, to our knowledge, none of them researched fatigue
resistance, which is how much fatigue leads to scapular dyskinesia.
8142

Biomedical Journal of Scientific & Technical Research

The purpose of this study was to investigate the effect of fatigue
resistance on scapular kinematics by analyzing the kinematics
during repeated arm elevation. We hypothesized that fatigue
resistance is different by direction of scapular kinematics.

Materials and Methods

Seventeen healthy subjects were recruited in this study. Theirmean age was 20.5 ± 0.6 years, mean height was 169.6 ± 4.6cm, andmean body mass was 60.6 ± 5.9kg. No subject had any history ofshoulder pain or injuries before participating in this study.

The study was performed in accordance with the World
Medical Associations Declaration of Helsinki. The purpose, nature,and potential risks of the experiments were fully explained to theparticipants, and all participants gave written, informed consent
prior to their inclusion in the study. The study protocol wasapproved by the research ethics committees of the respective
affiliated institutes (17-3).

Volume 10- Issue 5: 2018the scapular landmarks. Measurement angles were the scapularupward rotation, scapular posterior tilting, scapular externalrotation, arm elevation, and horizontal adduction between thehumeral and scapula plane.

We chose five sets of elevation data: the first elevation (0%),
25% of the iteration count (25%), 50% of the iteration count (50%),
75% of the iteration count (75%), and the final elevation (100%).
Each arm elevation data was interpolated into 100 frames using
the spline function. Scapular upward rotation, posterior tilting,and external rotation were used to examine fatigue resistance on
scapular kinematics (Figure 1A). Additionally, we calculated the
autocorrelation of the arm elevation angle tracking and horizontal
adduction to investigate the statistical stationarity of movement(Figure 1B).

Participants held a dumbbell with their right hand and repeatedarm elevation as much as possible in the scapular plane at the
elbow extension position; movement from the downward position
to the maximum elevated position and the opposite movement was
repeated during constant 3-s periods. Repeated arm elevation was
continued until either the appearance of compensatory movements,
the participants could not fulfill the task within the time or were
offered retirement.

The dumbbell was approximately 15% of the twice maximum
shoulder abduction force. For the measurement of the shoulder
abduction force, we used a hand-held dynamometer, Mobie(SAKAImed, Osaka, Japan); force loading was applied with theshoulder at a 90° elevation in the scapular plane and the elbow
extended 0° with the forearm midway between a thumb-up
and thumb-down position. The belt of the Mobie was fixed tothe distal humerus and the floor. The participants were asked toexert a maximum isometric contraction in the shoulder abduction
direction [14].

Kinematic data were collected during the task using anelectromagnetic tracking device, LIBERTY (Polhemus, Vermont,
USA), and Motion Monitor software® version 8.43 (Innovative
Sports Training., Inc., Chicago, IL). Data were collected at a 120-Hz
sampling rate. The global coordinate system was established by atransmitter mounted on a rigid wooden base frame aligned withthe cardinal planes of the body. Electromagnetic sensors wereattached to the sternum, acromion, and humerus on the right side.
The bony landmarks were palpated and digitized while the subject
sat on a plastic chair and relaxed the arm to the side of the body.
The landmarks were chosen in accordance with the International
Society of Biomechanics [15]: the spinous processes of the 7th
cervical and 8th thoracic vertebrae, suprasternal notch, and xiphoidprocess were the thoracic landmarks, the glenohumeral joint
rotation center (estimated by the rotation method) and medial andlateral epicondyles were the humeral landmarks, and the acromial
angle, root of the spine of the scapula, and the inferior angle were

Figure 1A: Scapula kinematics during one arm elevation.
Example of the scapula kinematics during one arm
elevation. The dashed line represents upward rotation,
the gray line represents posterior tilting, and the black line
represents external rotation.

Figure 1B: Tracking of the arm elevation angle andhorizontal adduction angle. An example of the trackingof the arm elevation angle and horizontal adduction
angle. The black line represents the arm elevation angle
at 0% and the dashed line represents at 25%. The closed
circle represents the horizontal adduction angle at 0%
and the open circle represents at 25%. We calculated eachautocorrelation from the data of 100 tracks.

Cite this article: Hitoshi Koda, Yoshihiro Kai, Noriyuki Kida, Shin Murata, et al. Influence of Muscle Fatigue on Three-Dimensional Scapular Kinematics During Repeated Arm Elevation. Biomed J Sci&Tech Res 10(5)-2018. BJSTR. MS.ID.002022. DOI: 10.26717/ BJSTR.2018.10.002022.

8143

Volume 10- Issue 5: 2018

Biomedical Journal of Scientific & Technical Research

SPSS software for Windows version 24.0 (IBM, Armonk, NY,
USA) was used for data analysis. The effects of the conditions (0%,25%, 50%, 75%, 100%) on scapular upward rotation, posterior
tilting, and external rotation were analyzed using a one-way
repeated measure analysis of variance (ANOVA). When a significant
main effect of the condition was observed, the post-hoc Bonferroni
test was used to determine the significant differences. The level ofstatistical significance was set at p<0.05.

Results

The maximum shoulder abduction force was 15.6 ± 2.3kg (13.5- 19.3kg), and the dumbbell weight held by participants was 2.0 ±0.5kg (1.5 - 3.0kg). The iteration count of arm elevation was 25.2 ±10.2 times (10 - 38 times). Table 1 shows the autocorrelation of thearm elevation angle tracking and the horizontal adduction during
repeated arm elevation.

± 7.8°. The results from the ANOVA tests indicated a significant
effect of the condition on posterior tilting. Additionally, post-hoc
analysis revealed the angle to significantly decrease at the 75% and100% iteration counts compared to 0% iteration counts (p=0.021)(Figure 2B).

The external rotation angles were as follows: 0%, 8.8 ± 4.8°;
25%, 7.3 ± 2.8°; 50%, 8.9 ± 2.9°; 75%, 9.9 ± 4.0°; 100%, 11.4 ±4.0°. The results from the ANOVA tests indicated no effect of thecondition on external rotation (Figure 2C).

Table 1: Autocorrelation with the first elevation of the arm
elevation and the horizontal adduction.
Armelevation

Horizontal
adduction

25%

50%

75%

100%

0.95
(0.80 - 0.99)

0.92(0.69 - 0.99)

0.91(0.70 - 0.98)

0.90(0.64 - 0.98)

0.69(0.15 - 0.98)

mean (min - max)

0.60
(0.31 - 0.91)

0.64(0.39 - 0.91)

0.56(0.18 - 0.93)

The upward rotation angles were as follows: 0%, 34.8 ± 5.7°;
25%, 36.2 ± 7.8°; 50%, 37.0 ± 5.5°; 75%, 37.1 ± 6.1°; 100%, 38.1
± 4.7°. The results from the ANOVA tests indicated a significant
effect of the condition on upward rotation. Additionally, there wasa significant difference in the angle between the 100% and 0%
iteration count (p=0.014) (Figure 2A).

Figure 2B: Scapular posterior tilting. Post-hoc analysis
revealed the posterior tilting angle to significantly
decrease at the 75% and 100% compared to 0% (*p < 0.05).

Figure 2C: Scapular external rotation. The results fromthe ANOVA tests indicated no effect of the condition on
external rotation (non-significant [n.s.]).

Discussion
Figure 2A: Scapular upward rotation. Post-hoc analysis
revealed the upward rotation angle to significantly
increase at the 100% compared to 0% (*p < 0.05).
The posterior tilting angles were as follows: 0%, 21.6 ± 7.6°;
25%, 22.1 ± 6.2°; 50%, 20.6 ± 6.3°; 75%, 17.8 ± 8.0°; 100%, 17.7

In the present study, we investigated the effect of fatigue
resistance on the scapula kinematics by analyzing the kinematics
during repeated arm elevation. Our results showed that the degreeof shoulder fatigue contributed to the scapular kinematics. The
most important findings of this study were that the angle of upward
rotation was maintained until 75%, with an increase observed at
100%, and the angle of posterior tilting was maintained until 50%,
with a decrease observed after 75%.

Cite this article: Hitoshi Koda, Yoshihiro Kai, Noriyuki Kida, Shin Murata, et al. Influence of Muscle Fatigue on Three-Dimensional Scapular
Kinematics During Repeated Arm Elevation. Biomed J Sci&Tech Res 10(5)-2018. BJSTR. MS.ID.002022. DOI: 10.26717/ BJSTR.2018.10.002022.

8144

Volume 10- Issue 5: 2018

Biomedical Journal of Scientific & Technical Research

Generally, there are many reports suggesting that muscle
fatigue affects the muscle activation pattern and scapula kinematics[9,10,16-19]. Szucs et al. [17] showed that higher upper trapezius
activation may be compensatory for fatigue in the other shoulder
muscles. Joshi et al. [19] investigated the influence of externalrotation fatigue and showed increased scapula upward rotationand decreased lower trapezius activity. However, no researchers
have previously measured fatigue resistance, which is how muchfatigue leads to scapular dyskinesia. Our results showed thatthe scapula upward rotation at 100% significantly increased
compared to the rotation at 0%. Moreover, it was confirmed by ahigh autocorrelation of 0.90-0.95 that participants could perform
unified arm elevation. It was suggested that muscle fatigue by
repeated arm elevation increased the upward rotation, which wasmaintained until complete exhaustion.
Scapular posterior tilting was maintained until 50% and adecrease was observed after 75%. Posterior tilting during arm
elevation plays an important role in extending the acromiohumeral distance; a decrease results in the risk of impingement
syndrome [20,21]. Lukasiewicz et al. [22] reported subjects withimpingement demonstrated a significantly lower posterior tilting
angle using a 3-dimensional electromechanical digitizer, suggestingthat altered posterior tilting may be an important aspect of thescapular kinematics analysis. However, the evaluation of scapularkinematics is generally carried out by measuring the upper rotationor scapula-spine distance; it is difficult to evaluate alterations in
the posterior tilting angle in the clinic [23]. The decrease in theposterior tilting angle was observed before the increase in the
upward rotation angle; the decrease in the posterior tilting angle
appears when it exceeds 50%. These results may help to keep
stress under the surface of the acromion by limiting within 50% of
the iteration count.
No differences were observed in the angle of scapular externalrotation during the fatigue task. These findings on the angle ofexternal rotation were not in agreement with those of the study
by Chopp et al. [11] and Ebaugh et al. [24], who reported anincrease in scapular external rotation. On the other hand, Tsai etal. [25] reported a decrease in the scapular external rotation postfatigue. In this study, we controlled the elevation plane by visualconfirmation during the fatigue task; however, autocorrelation of
the horizontal adduction tracking was 0.56 - 0.69, meaning theelevation may not be in the same plane. These contrasting results
concerning the scapular external rotation angle may be due todifficulty in controlling the elevation plane.

The present study had several limitations. First, ourparticipant sample included young adults who were not athletes;
when analyzing the repeated arm elevation, the tendency ofscapula kinematics might be different depending on the different
sports performed by athletes. Second, we did not perform
electromyography during the fatigue protocol, and it was unknown
which muscles affected the scapula kinematics. In future studies,
the scapula kinematics of more complicated movements, such as thethrowing motion, should be investigated. Furthermore, the muscles
affecting shoulder kinematics should be clarified. Muscle fatigue

by repeated arm elevation resulted in an increased the angle of
upward rotation, which was maintained until just before complete
exhaustion. A decrease in the posterior tilting angle was observed
before (exceeding 50% of the iteration count) the increase in the
upward rotation angle. It is suggested that limiting the posterior
tilting angle within 50% of the iteration count might be importantto prevent scapular dyskinesia caused by muscle fatigue.

Acknowledgement

The authors would like to thank those who participated in the
study.

References

1. Van Andel C, Van Hutten K, Eversdijk M, Veeger D, Harlaar J (2009)
Recording scapular motion using an acromion marker cluster. Gait
Posture 29(1): 123-128.
2. Lo YPC, Hsu YCS, Chan KM (1990) Epidemiology of shoulder impingement
in upper arm sports events. Br J Sports Med 24(3): 173-177.

3. Burn MB, McCulloch PC, Lintner DM, Liberman SR, Harris JD (2016)
Prevalence of scapular dyskinesis in overhead and nonoverheadathletes. Orthop J Sports Med 4(2): 1-8.
4. Kibler WB, McMullen J (2003) Scapular dyskinesis and its relation toshoulder pain. J Am Acad Orthop Surg 11(2): 142-151.
5. Willmore EG, Smith MJ (2016) Scapular dyskinesia: Evolution towards asystems-based approach. Shoulder Elbow 8(1): 61-70.

6. Sanchez HM, Sanchez EG, Tavares LI (2016) Association between
scapular dyskinesia and shoulder pain in young adults. Acta Ortop Bras
24(5): 243-248.

7. Huang TS, Huang CY, Ou HL, Lin JJ (2016) Scapular dyskinesis: Patterns,
functional disability and associated factors in people with shoulder
disorders. Man Ther 26: 165-171.
8. Kibler WB, Sciascia A (2016) The role of the scapula in preventing andtreating shoulder instability. Knee Surg Sports Traumatol Arthrosc
24(2): 390-397.
9. Ebaugh DD, McClure PW, Karduna AR (2006) Scapulothoracic andglenohumeral kinematics following an external rotation fatigue protocol.
J Orthop Sports Phys Ther 36(8): 557-571.

10. Maenhout A, Dhooge F, Van Herzeele M, Palmans T, Cools A (2015)
Acromiohumeral distance and 3-dimensional scapular position change
after overhead muscle fatigue. J Athl Train 50(3): 281-288.
11. Chopp JN, Fischer SL, Dickerson CR (2011) The specificity of fatiguing
protocols affects scapular orientation: Implications for subacromial
impingement. Clin Biomech 26(1): 40-45.

12. Chopp JN, O’Neill JM, Hurley K, Dickerson CR (2010) Superior humeral
head migration occurs following a protocol designed to fatigue therotator cuff: A radiographic analysis. J Shoulder Elbow Surg 19(8): 11371144.
13. Tse CT, McDonald AC, Keir PJ (2016) Adaptations to isolated shoulder
fatigue during simulated repetitive work. Part I: Fatigue. J Electromyogr
Kinesiol 29: 34-41.
14. Cadogan A, Laslett M, Hing W, McNair P, Williams M (2011) Reliability ofa new hand-held dynamometer in measuring shoulder range of motion
and strength. Man Ther 16(1): 97-101.

15. Wu G, Van Helm FC, Veeger HE, Makhsous M, Van Roy P, et al. (2005) ISB
recommendation on definitions of joint coordinate systems of various
joints for the reporting of human joint motion-Part II: shoulder, elbow,
wrist and hand. J Biomech 38(5): 981-992.
16. Cools AM, Witvrouw EE, De Clercq GA, Danneels LA, Willems TM, etal. (2002) Scapular muscle recruitment pattern: Electromyographic

Cite this article: Hitoshi Koda, Yoshihiro Kai, Noriyuki Kida, Shin Murata, et al. Influence of Muscle Fatigue on Three-Dimensional Scapular Kinematics During Repeated Arm Elevation. Biomed J Sci&Tech Res 10(5)-2018. BJSTR. MS.ID.002022. DOI: 10.26717/ BJSTR.2018.10.002022.

8145

Biomedical Journal of Scientific & Technical Research

response of the trapezius muscle to sudden shoulder movement before
and after a fatiguing exercise. J Orthop Sports Phys Ther 32(5): 221-229.

17. Szucs K, Navalgund A, Borstad JD (2009) Scapular muscle activation andco-activation following a fatigue task. Med Biol Eng Comput 47(5):487495.

18. McQuade KJ, Dawson J, Smidt GL (1998) Scapulothoracic muscle fatigue
associated with alterations in scapulohumeral rhythm kinematics
during maximum resistive shoulder elevation. J Orthop Sports Phys Ther
28(2): 74-80.
19. Joshi M, Thigpen CA, Bunn K, Karas SG, Padua DA (2011) Shoulder
external rotation fatigue and scapular muscle activation and kinematics
in overhead athletes. J Athl Train 46(4): 349-357.
20. Endo K, Ikata T, Katoh S, Takeda Y (2001) Radiographic assessment ofscapular rotational tilt in chronic shoulder impingement syndrome. J
Orthop 6(1): 3-10.

ISSN: 2574-1241

Volume 10- Issue 5: 2018

21. Ludewig PM, Cook TM (2000) Alterations in shoulder kinematics
and associated muscle activity in people with symptoms of shoulder
impingement. Phys Ther 80(3): 276-291.

22. Lukasiewicz AC, McClure P, Michener L, Pratt N, Sennett B (1999)
Comparison of 3-dimensional scapular position and orientation between
subjects with and without shoulder impingement. J Orthop Sports Phys
Ther 29(10): 574-583.
23. Kibler WB, Sciascia A (2010) Current concepts: Scapular dyskinesis. Br J
Sports Med 44(5): 300-305.

24. Ebaugh DD, McClure PW, Karduna AR (2006) Effects of shoulder muscle
fatigue caused by repetitive overhead activities on scapulothoracic andglenohumeral kinematics. J Electromyogr Kinesiol 16(3): 224-235.

25. Tsai NT, McClure PW, Karduna AR (2003) Effects of muscle fatigue on
3-dimensional scapular kinematics. Arch Phys Med Rehabil 84(7): 10001005.

DOI: 10.26717/BJSTR.2018.10.002022

Assets of Publishing with us

Hitoshi Koda. Biomed J Sci & Tech Res• Global archiving of articles

This work is licensed under Creative
Commons Attribution 4.0 License

Submission Link: https://biomedres.us/submit-manuscript.php• Immediate, unrestricted online access• Rigorous Peer Review Process• Authors Retain Copyrights• Unique DOI for all articles

https://biomedres.us/

Cite this article: Hitoshi Koda, Yoshihiro Kai, Noriyuki Kida, Shin Murata, et al. Influence of Muscle Fatigue on Three-Dimensional Scapular
Kinematics During Repeated Arm Elevation. Biomed J Sci&Tech Res 10(5)-2018. BJSTR. MS.ID.002022. DOI: 10.26717/ BJSTR.2018.10.002022.

8146