Preliminary Analysis of Closed Kinetic Chain Upper Extremity Stability Test Differences Between Healthy and Previously Injured/In-Pain Baseball Pitchers

Abstract

Background:

A comprehensive examination of the kinetic chain during an overhead athlete’s upper extremity assessment, such as the closed kinetic chain upper extremity stability test (CKCUEST), may help clinicians identify potential upper extremity dysfunction.

Hypothesis:

Body position observed on dominant and nondominant hand touch during a CKCUEST trial differs between players with previous injury/pain history compared with healthy counterparts.

Study Design:

Descriptive laboratory study.

Level of Evidence:

Level 5.

Methods:

Seventeen baseball pitchers were recruited to participate (18.03 ± 2.01 years; 185.40 ± 6.57 cm; 83.92 ± 13.87 kg). A medical history questionnaire was used to separate participants into groups, either previous injury/pain or healthy. Kinematic and kinetic data were collected on the participants performing the CKCUEST with an electromagnetic tracking system. Kinematics were analyzed using a pair of 1-way multivariate analyses of variance (MANOVAs).

Results:

The MANOVA for nondominant hand touch in the CKCUEST revealed a significant difference in lumbopelvic-hip complex (LPHC) kinematics between previously injured/pain group and healthy group (Λ = 0.37; F_4,12 = 5.12; P = 0.01).

Conclusions:

The previously injured/pain group displayed less pelvic axial rotation and dominant hip abduction during the nondominant touch indicating more LPHC stability during the nondominant touch. In conclusion, differences were observed in LPHC kinematics during the CKCUEST nondominant touch between a healthy and previously injured/pain group perhaps due to the increased awareness provided through rehabilitative programs for the previously injured/pain group.

Clinical Relevance:

Clinicians can use this information to help address kinetic chain movement efficiency within baseball pitchers. This study provides evidence of LPHC kinematic differences during the nondominant touch of baseball pitchers and may enhance the use of the CKCUEST as a return-to-play assessment.

Focusing on the kinetic chain during assessment and rehabilitation may benefit those attempting to return to play by promoting increased movement efficiency. ²⁰ More efficient movement would require less energy expended by the distal extremity due to an optimally functioning proximal section within the kinetic chain.^3,5,12,14 As the lumbopelvic-hip complex (LPHC) and scapular regions serve as proximal segments in the kinetic chain for the more distal upper extremity in overhand throwers, coaches and clinicians should not neglect these regions within training or rehabilitative programs. A clinician’s ability to assess LPHC instability is vital to determine whether an athlete is susceptible to reinjury or ready to return to action on the field. However, a clinician’s ability to identify modifiable risk factors is limited by the type of assessment performed. The assessment should be task specific when assessing stability in an overhand throwing athlete with an upper extremity injury. ²¹ Assessments for overhand throwing athletes should require upper extremity movement while also challenging stability throughout the entire kinetic chain. The closed kinetic chain upper extremity stability test (CKCUEST) is a low-cost, time-efficient assessment that requires little equipment and is easily administered by coaches and clinicians supplying this type of evaluation. The CKCUEST was created to assess upper extremity stability during closed chain exercise and is practical for upper extremity athletes.^7,22

In addition, the CKCUEST movement requires the proximal segments to stabilize so that the distal segment can move freely. Even with proper sequencing of the kinetic chain, an unstable proximal segment will increase the distal segments’ demands to obtain a maximal number of touches. An athlete unable to stabilize their shoulder joint will often resort to compensations shifting the center of mass to a more stable position to maintain performance. ¹⁸ In order to maintain competition levels, stability and subsequent ability to transmit forces across joints will dissipate among athletes with compromised joints, whether due to fatigue or injury. However, analyzing joint kinetics and kinematics is not feasible in most clinical settings. Therefore, assessing the ability to shift a person’s center of mass over their base of support may provide an avenue to determine an athlete’s reinjury susceptibility. Kinematics such as increased stance width, increased hip ab/adduction range of motion, and increased pelvic axial rotation towards the stance side provide insight into how well a person keeps their center of mass stabilized, thus indicating their proximal stability.

In addition to the average CKCUEST test score quantifying someone’s ability to stabilize their scapula and glenohumeral joint to maximize the number of touches within the test’s allotted time, these aforementioned kinematics will possibly help coaches and clinicians identify an athlete’s upper extremity movement efficiency. Movement efficiency would be determined as someone’s ability to maximize the number of touches through minimum energy expenditure seen through minimizing motion at the LPHC. The purpose of this preliminary study was to examine if kinematics observed during the CKCUEST differ between baseball players with previous injury/pain and healthy controls. We hypothesized that body position observed on dominant and nondominant hand touches (Figure 1) during a CKCUEST trial would differ between players with previous injury/pain history compared with healthy counterparts. Specifically, players in the previous injury/pain category will exhibit different LPHC stability as seen by increased stance width, increased touch-side pelvic axial rotation, increased support side leg hip adduction, and touch side leg hip abduction compared to their healthy counterparts on both dominant and nondominant hand touches.

Figure 1.

(a) Starting position for the closed kinetic chain upper extremity stability test (hands 36 inches apart). (b) Nondominant hand touch for a right-hand dominant participant. (c) Dominant hand touch for a right-hand dominant participant.

Methods

Seventeen high school and collegiate baseball players (18.03 ± 2.01 years; 185.40 ± 6.57 cm; 83.92 ± 13.87 kg) currently playing competitively participated in this preliminary study as part of a convenience sampling design. The Institutional Review Board of Auburn University approved all testing protocols. Upon arriving at the lab, participants completed a medical history questionnaire before data collection to determine whether they have been free of injury for the past 6 months. No participants recovering from a recent, within the past 6 months, musculoskeletal injury were included in this study. Participants completed the questionnaire without knowledge they would be placed into separate groups (previous injury/pain or healthy). Participants were asked in the questionnaire if (1) they had history of a serious injury (requiring at least 1 month of rest from competitive activity) and (2) they were currently experiencing any pain (either lower back or upper extremity). Participants who answered yes to either of these questions were placed in the previous injury/pain grouping (n = 8; 17.33 ± 1.20 years; 186.49 ± 6.49 cm; 81.95 ± 9.59 kg). All other participants were placed in the healthy group (n = 9; 18.65 ± 2.44 years; 184.44 ± 6.89 cm; 85.67 ± 17.22 kg).

Protocol

Kinematic data were collected at 240 Hz with an electromagnetic tracking system (trakSTAR; Ascension Technologies Inc) synced through The MotionMonitor (Innovative Sports Training). Electromagnetic sensors were attached to various locations using previously established methodologies. ² Raw data regarding sensor position and orientation were transformed to locally based coordinate systems for each body segment. For the world axis, the Y-axis represented the vertical direction; in the direction of movement was the positive X-axis; and orthogonal to X and Y to the right was the positive Z-axis. Orientation of the body segments were obtained with Euler angle sequences that were consistent with the International Society of Biomechanics standards and joint conventions.^30,31 More specifically, a Z, X ′, Y ″ sequence relative to the laboratory reference frame was used to describe pelvic motion. Raw data were independently filtered along each global axis with a fourth-order Butterworth filter with a cutoff frequency of 13.4 Hz.^2,17

Once all electromagnetic sensors were attached and digitized, participants completed the CKCUEST using a protocol that has been proven reliable among a wide range of participants (see Figure 1).^{7,8,13,16,23,25,28} Validity of the CKCUEST has also been established across a population with and without shoulder pain using grip and shoulder rotational isometric strength measures. ¹³ Once starting position was assumed, 15 seconds were allowed per trial to achieve the maximum amount of touches to the opposite hand while keeping 1 hand on tape through the test. The total number of hand touches within each 15-second trial were observed by 3 researchers, confirmed, and recorded. The middle touch, established by Tucci and colleagues, was found for each trial by analyzing the total number of touches and dividing by 2. After the middle touch was found, it was event marked and analyzed. ²⁷ For an odd number of touches, the middle touch was defined as the total number of touches divided by 2 plus 0.5. ²⁷ Kinematic data from all 3 trials of the CKCUEST were averaged at the middle touch event. Handedness was indicated by the participant’s throwing arm.

Data Analysis

Data were processed by MATLAB (version R2013b; The Math Works Inc) and analyzed with JASP 0.10.2. An independent sample t test was run to determine whether any difference existed in the average number of touches for the CKCUEST. Box’s M test for homogeneity of covariance and Shapiro-Wilk test for univariate normality were conducted to check multivariate assumptions. The two events were (1) dominant hand touching the nondominant hand and (2) nondominant hand touching the dominant hand. A pair of 1-way multivariate analyses of variance (MANOVAs) were run for the time points of dominant hand touch and non-dominant hand touch. Testwise error was set at α = 0.05 to detect kinematic differences between groups. Univariate ANOVA with Bonferroni adjustments (α = 0.01) was run following multivariate significance to discover specific group differences.

Results

Descriptive statistics are reported in Table 1. The MANOVA for a dominant hand touching event in the CKCUEST revealed no multivariate significance for LPHC kinematics between previously injured/pain group and healthy group (Λ = 0.56; F_4,12 = 2.36; P = 0.11; η² = 0.44). The MANOVA for nondominant hand touch in the CKCUEST revealed a significance difference in LPHC kinematics between previously injured/pain group and healthy group (Λ = 0.37; F_4,12 = 5.12; P = 0.01). Sixty-three percent of the differences observed between groups at the event of a nondominant hand touch can be attributed to the athlete’s pain/injury history (η ² = 0.63). Following the multivariate test, results revealed no univariate significance. Univariate analyses of variance (ANOVAs) can be found in Table 2. The independent sample t test ran to determine whether a difference existed between groups for the average number of touches in the CKCUEST revealed no significance [t = 0.47; P = 0.65; d = 0.23; 95% CI –0.74 to 1.18].

Table 1.

Descriptive statistics reported for the events of dominant hand touch and nondominant hand touch during the CKCUEST, mean (standard deviation)

	Dominant Hand Touch		Nondominant Hand Touch
Variable	Healthy	Previous Injury/Pain	Healthy	Previous Injury/Pain
Stance width, m	0.20 (0.10)	0.12 (0.07)	0.17 (0.11)	0.12 (0.06)
Pelvic axial rotation a , deg	–3.61 (7.04)	0.40 (3.88)	–8.81 (7.31)	–2.70 (4.20)
Support side hip ab/adduction b , deg	0.05 (8.69)	6.09 (6.35)	–18.30 (9.49)	–9.27 (6.16)
Touch side hip ab/adduction b , deg	–4.5 (10.46)	–3.19(7.74)	13.38 (11.71)	12.26 (7.19)

^a+, nondominant transverse pelvic girdle rotation; –, dominant transverse pelvic girdle rotation.

^b+, adduction; –, abduction.

Table 2.

Univariate ANOVAs for kinematics during the event of a nondominant hand touch

Variable	SS	df	MS	F	P
Stance width, m	0.01	1	0.01	1.21	0.29
Pelvic axial rotation, deg	158.08	1	158.08	4.31	0.06
Support side hip ab/adduction, deg	345.24	1	345.24	5.25	0.04
Touch side hip ab/adduction, deg	5.30	1	5.30	0.06	0.82

Significance was indicated by P = 0.01.

Discussion

The purpose of this study was to examine whether kinematics observed during the CKCUEST differ between baseball pitchers with previous lower back and upper extremity injury/pain and healthy controls. The hypothesis that LPHC kinematic differences would be observed for the CKCUEST between a previous injury/pain group and a group of healthy participants was partially supported with differences between groups being observed on the nondominant touch (Table 1). Specifically, when examining the descriptive statistics, healthy participants appear to have a less-stable LPHC as indicated by increased deviation from neutral posture via increased dominant side pelvic axial rotation and increased support side hip abduction and a wider stance. This partially supports our hypothesis that differences in LPHC stability would appear between groups. However, the lack of significant difference in CKCUEST scores between groups indicates that the healthy group does not achieve the objective of the motor skill differently than the previously injured/pain group.

Previous research has demonstrated the effectiveness of a LPHC stability program on an individual’s ability to enhance proximal stability.^1,10,15,29 With the need to establish stability of the proximal segments to achieve optimum distal mobility, ¹¹ the possibility exists that those participants in the previous injury/pain group are more focused on stabilizing the LPHC during an upper extremity assessment based on previous rehabilitative experience. Those who had previous injury/pain would likely undergo rehabilitative exercises focusing on the entire kinetic chain and the need to enhance LPHC stability.^19,24 Another possible explanation is an injured or in-pain person’s instinctual retreat to basic skill development. Motor skill progression from proximal to distal is a major milestone in motor development. ⁶ An athlete experiencing pain or coming off of an injury may be reemphasizing the basic need to stabilize the proximal segments, placing an organismic structural constraint on the movement so as not to experience further discomfort. Either of these reasons may explain the observation of a more stable LPHC in the previous injury/pain group during the nondominant hand touch of the CKCUEST and are worth further research endeavors.

All baseball participants experience similar repetitive unilateral rotational motion during overhand throwing and pitching. Therefore, observing similar LPHC kinematics between groups during the dominant hand touching event of the CKCUEST is not surprising. According to the specific adaptation to imposed demands principle, athletes who experience similar demands of an overhand pitch placed on their body will accrue similar movement adaptations.^4,9,26 During the dominant hand touch, much like the pitching motion, the pitcher attempts to stabilize the LPHC, whereas the dominant hand moves in an open-chain fashion. An investigation on LPHC muscle activity may have indicated a distinction in the dominant hand touch of the CKCUEST between healthy and previously injured/pain groups and should be considered for future research.

Limitations of this study include the sample size, retrospective injury history, and grouping of previously injured with those experiencing pain. Most importantly, it is not known whether the stability differences detected are clinically significant. Statistical significance does not necessarily imply clinical significance. With injury being such a broad classification, a more thorough investigation is needed to relate CKCUEST kinematics with injury. However, this preliminary study shows kinematic differences between the previously injured/pain group and healthy group in the CKCUEST serving as ground to direct future research. A definite limitation includes participants being a mixture of pitcher-only baseball athletes and dual-position (pitcher plus another position) baseball athletes. However, Roush and colleagues analyzed the CKCUEST average score among baseball positions and found no difference. ²²

In conclusion, differences were observed in LPHC kinematics during the CKCUEST nondominant touch between a healthy and previously injured/pain group, perhaps due to the increased awareness provided through rehabilitative programs in the need for LPHC stability to optimize distal mobility. In this preliminary study, the previously injured/pain group displayed less pelvic axial rotation and support side hip abduction during the nondominant touch indicating more LPHC stability during the nondominant hand touch. Future research should be conducted to determine the generalizability of these findings across a wider population. Coaches and clinicians should be aware of the differences in kinetic chain symmetry between overhead athletes to optimize training and rehabilitation programs to meet their sport- and position-specific needs.