The Effects of Thoracolumbar Manipulation on Gluteus Maximus Force Production

Investigators: Steven Casper Logan College of Chiropractic Steven.Casper@ logan.edu Elisabeth Pang Logan College of Chiropractic Elisabeth.Pang@ logan.edu

Advisor: Dr. Donald Christy Logan College of Chiropractic Donald.Christy@ logan.edu ABSTRACT

OBJECTIVE: Evidence has suggested hypertonicity of the psoas muscle is linked to restriction and dysfunction of the joints in the thoracic and lumbar spine. Over activity of the hip flexors has also been correlated with the inhibition gluteus maximus muscle. Following the knowledge from previous studies, the goal of this research is to determine if there is a link between thoracolumbar manipulation and gluteus maximus force production in asymptomatic subjects with hypertonic psoas (left, right or bilateral).

METHODS: The intervention for the manipulation group (n=13) consisted of a side lying manipulation applied from T10-L2. The control group (n=17) received side lying mobilization to the same region without application of a thrust. Before and after the manipulation or mobilization, gluteus maximus force production was measured in pounds utilizing a hand held Nicholas Manual Muscle Tester dynamometer. RESULTS: Statistical analysis revealed no significant changes in force production with either the manipulation or the mobilization group.

CONCLUSIONS: When comparing the data of the mobilization group with the data of the manipulation group, no correlations could be made. The mean change of gluteus maximus force production was insignificant with regards to the null hypothesis. The standard deviations were approximately 10 fold the size of the data, contrary to the Shapiro-Wilk normative test.

KEY INDEXING TERMS: Reciprocal Inhibition, Gluteus Maximus, Manipulation, Hyperrtonicity, Lower Crossed Syndrome.

The Effects of Thoracolumbar Manipulation on Gluteus Maximus Force Production

Background to contribute to an increased lordotic The gluteus maximus is the posture while compressing facet joints largest muscle in the body and serves and intervertebral discs of each an important role in many functional lumbar motion segment. (5) Through activities (14). It mainly acts as an reciprocal inhibition a hypertonic extensor and external rotator of the psoas is thought to lead to inhibited hip, however, in many patients, it is gluteus maximus function. (4) often found weak or inhibited. Methods for improving gluteus Inhibition of the gluteus maximus maximus activation and strength muscles has been linked to numerous should include methods to decrease clinical presentations including low the activity and tension of the back, hip and knee pain. Clinicians antagonist muscles, mainly the psoas. often treat these ailments by Previous studies have related implementing core activation and upper lumbar somatic dysfunction to strengthening exercises, which psoas hypertonicity (2,3). Karel Lewit include exercises centered around the described a chain reaction, in which gluteus maximus. psoas spasms were often associated Though many factors can with thoracolumbar spinal erector contribute to decreased muscle spasms and vice versa. Additionally, if strength and activation a formidable the thoracolumbar spinal erectors cause of inhibition is reciprocal were relaxed, the psoas would relax as inhibition. Reciprocal inhibition is a well (8). Recent research by McGill reflex which results in the inhibition demonstrated decreased surface EMG of antagonistic muscles after the activity in the paraspinal musculature activation of agonistic muscles. following spinal manipulation in Weakness is often reflex-mediated symptomatic subjects (7,10). McGill inhibition secondary to increased also found asymptomatic workers tension of the antagonist (13). with a history of low back pain were Vladamir Janda’s lower crossed more likely to have decreased hip syndrome describes a weak, inhibited extension and internal rotation than gluteus maximus while a tight, their cohorts with no history of low shortened psoas muscle is noted on back pain (9). The combination of the the anterior of the body (13). results from these two studies lead to The psoas muscle is a direct the hypothesis that spinal antagonist to the gluteus maximus. It manipulation will reduce paraspinal originates from the transverse musculature tone, which will in turn processes, lateral aspects of the result in reduced psoas musculature vertebral bodies and intervertebral tone which thus through reciprocal discs of T12-L5 and has innervation inhibition may allow for increased from the lumbar plexus, mainly L1-L3. activation, as measured by strength (11) It serves primarily as a hip flexor and surface EMG of the gluteus but also may function to externally maximus muscles. This hypothesis is rotate the hip. The psoas muscle has also supported by a study in the long been at the scrutiny of clinicians Journal of Manual and Manipulative dealing with low back pain. A Therapy which found that grade IV hypertonic psoas muscle is theorized mobilization of the anterior hip

The Effects of Thoracolumbar Manipulation on Gluteus Maximus Force Production

capsule resulted in a 14% increase in criteria, the subjects underwent gluteus maximus strength. It was evaluation of the tonicity of their psoas concluded that manual therapy of musculature bilaterally through the use joint restrictions is a valid method for of the Modified Thomas Test. This non- intervention of muscle weakness (15). invasive procedure simply has the Following the knowledge from participant actively fully flex one leg previous studies, the goal of this (hip and knee) into the chest while research is to determine if there is a allowing the other leg to hang link between thoracolumbar neutrally. In this position, the manipulation and gluteus maximus investigators then manually force production as measured by challenged the rectus femoris and dynamometry. psoas musculature and objectively Methods noted any findings. If the subject was Subjects will be recruited from a found to have at least one hypertonic chiropractic college campus. Prior to psoas muscle, then the lower thoracic being screened, they were required to spine and upper lumbar spine were meet the determined inclusion criteria palpated by an investigator in the (Table 1). In addition, subjects were seated position looking for excluded for a variety of previously subluxations, defined as a restriction determined factors (Table 2). of the movement of a specific vertebral motion segment either in Table 1: Inclusion Criteria flexion, extension, lateral flexion or current Logan College of rotation. Upon completion of the Chiropractic student; screening process, if the subject was found to meet the inclusion criteria, 18-50 years of age; and without any of the exclusion criteria, had at least one hypertonic psoas and no low back or pelvic pain. had at least one subluxation of the thoracolumbar region, he/she was

asked to participate in the Table 2: Exclusion Criteria intervention portion of the study. The a diagnosed low back disorder; qualifying subjects were randomly assigned to two groups, one to be a scoliotic curve greater than 20° manipulated, and the other to be currently taking muscle relaxant mobilized. Both groups of subjects pharmaceuticals; were asked to return for one additional intervention within one currently involved in injury week of the original screening litigation; process. The following intervention had history of back surgery; or each subject, regardless of the assigned group, lie prone on a flat currently pregnant. adjusting table. A hand held Nicholas Manual Muscle dynamometer was Upon qualifying for the study held externally against the based on the inclusion and exclusion participant’s mid-thigh posteriorly.

The Effects of Thoracolumbar Manipulation on Gluteus Maximus Force Production

By measuring the torque and prone position by an rotational speed of the movement investigator, and then provided with a simultaneously, the dynamometer is sequence of low velocity, minimal able to calculate the force production force implied movements in a side in pounds. The participant was asked posture position. There were no to extend at the hip with slight significant applied forces or thrusts in external rotation to the greatest attempt to cavitate the patient. Then, degree possible, so as to allow the regardless of the group, following the dynamometer to measure maximum intervention, each subject will have force production. This measurement the gluteus maximus force production was taken a total of three times on measured again using the each hip, allowing an average gluteus dynamometer and the same protocol maximus force production to be as previous. This study had 30 total determined. participating subjects. Of the 30, 17 Following the force production were assigned to the mobilization measurement, subjects were treated group and 13 to the manipulation according to their randomly assigned group. In the mobilization group 3 group. For those in the manipulation were females and 14 were males. In group, subjects were palpated in the the manipulation group, 4 were prone position by an investigator, and females and 9 were males. then provided with a side posture Diversified high velocity, low Results amplitude manipulation in a region of The data (Table 3, 4) were the thoracolumbar junction (T10-L2) analyzed in terms of mean changes in based on the palpatory findings. the force production. The non- Cavitation was not a requirement, and intervention (mobilization group) each patient was only thrusted upon demonstrated a change of 1.773 N once. For those in the mobilization (standard deviation: 6.427) on the left, group, subjects were palpated in the and 0.850 (standard deviation: 8.013)

Table 3: Results of Mobilization Group Left Gluteus Maximus Right Gluteus Maximus Tight Male/ Pre- Post- Force Pre- Post- Force Psoas Female Intervention Intervention Production Intervention Intervention Production (R/L/B) Force Force Change Force Force Change Average Average (Pounds) Average Average (Pounds) (Pounds) (Pounds) (Pounds) (Pounds) B M 55.63 55.47 -0.17 55.67 55.47 -0.20 B M 52.53 47.67 -4.87 48.67 48.70 0.03 L M 43.00 40.07 -2.93 41.03 48.30 7.27 L M 41.57 42.23 0.67 50.00 59.67 9.67 B M 53.60 59.53 5.93 76.63 88.53 11.90 B M 25.63 15.00 -10.63 30.43 10.35 -20.08 R M 61.20 65.07 3.87 55.50 60.67 5.17 B F 44.43 38.93 -5.50 38.07 36.80 -1.27 B F 30.50 30.53 0.03 42.67 33.80 -8.87 B M 45.23 53.23 8.00 59.67 56.43 -3.23 B M 23.03 25.53 2.50 21.00 27.93 6.93 B M 67.93 70.07 2.13 85.23 80.10 -5.13 R M 59.67 69.87 10.20 84.83 81.03 -3.80 L F 39.83 35.10 -4.73 49.53 48.50 -1.03 B M 50.33 52.23 1.90 45.77 46.17 0.40 L M 46.23 58.97 12.73 44.63 53.83 9.20 B M 40.33 51.33 11.00 43.77 51.27 7.50

Table 4: Results of Manipulation Group Left Gluteus Maximus Right Gluteus Maximus Tight Male/ Pre- Post- Force Pre- Post- Force Psoas Female Intervention Intervention Production Intervention Intervention Production (R/L/B) Force Force Change Force Force Change Average Average (Pounds) Average Average (Pounds) (Pounds) (Pounds) (Pounds) (Pounds) B M 44.37 33.73 -10.63 39.53 52.00 12.47 L M 41.43 35.17 -6.27 51.93 37.90 -14.03 B M 59.33 54.43 -4.90 57.77 53.10 -4.67 B M 54.73 40.63 -14.10 48.77 41.57 -7.20 B M 48.60 50.80 2.20 44.90 43.87 -1.03 B M 42.60 49.10 6.50 43.60 63.87 20.27 R M 50.57 58.13 7.57 52.37 64.27 11.90 B F 36.03 35.80 -0.23 34.73 36.25 1.52 R F 34.93 40.53 5.60 43.50 46.60 3.10 L F 42.53 32.80 -9.73 60.17 43.73 -16.43 B M 85.30 91.50 6.20 71.47 87.37 15.90 B M 44.30 48.97 4.67 52.27 42.00 -10.27 B F 47.83 51.03 3.20 50.03 47.87 -2.17 The Effects of Thoracolumbar Manipulation on Gluteus Maximus Force Production 30

Measured 0 Gluteus Maximus -10 Force Production

(Pounds) -20

-30

Mobilization Mobilization Manipulation Manipulation {LEFT} {RIGHT}

Figure 1: Ranges of change of gluteus maximus force production.

on the right. The intervention group the manipulation group. Similarly on who received manipulations the right, the ranges were 31.983N demonstrated a change of -0.764 and 36.700 N respectively. (standard deviation: 7.464) on the left, The median changes of the left and 0.719 (standard deviation: gluteus maximus force production 11.610) on the right. The range of were 1.900N for the mobilization change of mean force production was group, and 2.200N for the less on the left side than on the right manipulation group. On the right, the (Figure 1). On the left, the range of median changes were 0.033N for the mean change was 23.677N for the for mobilization group, and -1.033N mobilization group, and 21.667N for for the manipulation group (Table 5)

Table 5: Summary of Gluteus Maximus Force Production Change Mobilization Group Manipulation Group Left Gluteus Right Left Gluteus Right Maximus Gluteus Maximus Gluteus Maximus Maximus Sample Size 17 17 13 13 Mean (Pounds) 1.773 0.85 -0.764 0.719 Standard Deviation (Pounds) 6.427 8.013 7.464 11.61 Confidence Interval of Mean 3.304 4.120 4.510 7.016 (Pounds) Range (Pounds) 23.367 31.983 21.667 36.700 Maximum (Pounds) 12.733 11.900 7.567 20.267 Minimum (Pounds) -10.633 -20.083 -14.100 -16.423

The Effects of Thoracolumbar Manipulation on Gluteus Maximus Force Production

Median (Pounds) 1.900 0.033 2.200 -1.033 The data was further analyzed the left, and -3.72N (standard in a Shapiro-Wilk normality test to deviation: 4.46N) on the right (Table determine its distribution. This test 6). revealed the data matched the pattern In the manipulation group, expected if the data was drawn from a males demonstrated a mean change of population with a normal distribution. -0.97N (standard deviation: 8.15N) of Males in the mobilization group the left gluteus maximus, and 2.59N had a mean change of left gluteus (standard deviation: 12.64N) of the maximus force production of 2.88N right. Additionally, females of the (standard deviation: 6.48N), and manipulation group demonstrated a 1.83N (standard deviation: 8.37N) of mean change of -0.29N (standard the right side. Females in the same deviation: 6.73N) on the left, and - group exhibited a mean change of - 3.40N (standard deviation 8.90N) on 3.40N (standard deviation: 3.00N) on the right (Table 7).

Table 6: Male Subject Gluteus Maximus Force Production Change Mobilization Group Manipulation Group Left Gluteus Right Gluteus Left Gluteus Right Gluteus Maximus Maximus Maximus Maximus Mean (Pounds) 2.881 1.830 -0.974 2.2593 Standard Deviation 6.477 8.373 8.148 12.635 (Pounds)

Table 7: Female Subject Gluteus Maximus Force Production Change Mobilization Group Manipulation Group Left Gluteus Right Gluteus Left Gluteus Right Gluteus Maximus Maximus Maximus Maximus Mean (Pounds) -3.400 -3.722 -.0292 -3.496 Standard Deviation 2.998 4.457 6.734 8.903 (Pounds)

In addition, the side of psoas 6.28N (standard deviation: 4.98N) on hypertonicity was recorded and the right. Subjects with right psoas correlated with mean changes of force tension only demonstrated changes of production of the subjects of both 7.03N (standard deviation 4.47N) and groups. In the mobilization group, 0.68N (standard deviation: 6.34N) on those subjects exhibiting bilateral the left and right respectively. psoas tension demonstrated a change Subjects in the manipulation of 0.93N (standard deviation: 6.26N) group with bilateral psoas tension on the left, and 1.09N (standard demonstrated a mean change of - deviation: 8.68N) on the right. Those 1.77N (standard deviation: 7.71N) on with left psoas tension only had a the left and 2.76N (standard deviation: mean change of 1.43N (standard 10.83N) in the right gluteus maximus. deviation: 7.86N) on the left and Those with only increased tension of

The Effects of Thoracolumbar Manipulation on Gluteus Maximus Force Production

the left psoas had a mean change of there was a mean change of 6.58N -8.00N (standard deviation: 2.45N) of (standard deviation 1.39N) of left the left gluteus maximus -15.23N gluteus maximus force production and (standard deviation: 1.70N) of the 7.50N (standard deviation: 6.22N) of right. Finally in subjects with the right (Table 8). increased tension of the right psoas

Table 8: Gluteus Maximus Force Production Change Based on Side of Psoas Tension Mobilization Group Manipulation Group Bilateral Left Right Bilateral Left Right Psoas Psoas Psoas Psoas Psoas Psoas Tension Tension Tension Tension Tension Tension Mean Change of 0.939 1.433 7.030 -1.770 -8.000 6.580 Left Gluteus Maximus (Pounds) Standard Deviation 6.261 7.861 4.478 7.711 2.451 1.391 of Change of Left Gluteus Maximus (Pounds) Mean Change of -1.090 6.280 0.680 2.760 -15.230 7.500 Right Gluteus Maximus (Pounds) Standard Deviation 8.680 4.982 6.340 10.826 1.697 6.222 of Change of Right Gluteus Maximus (Pounds)

Discussion production with either type of When comparing the data of intervention be it mobilization or the mobilization group with the data manipulation. The males on the other of the manipulation group, no hand were more likely to experience a correlations could be made. The mean slight increase in force production change of gluteus maximus force with either intervention. This brings production was insignificant with the psychosocial question into the regards to the null hypothesis. The picture, in which these variables could standard deviations were not be controlled in the experimental approximately 10 fold the size of the setting. However, the standard data, contrary to the Shapiro-Wilk deviations were still much larger than normative test. the means indicating a wide range of No clear correlation could be outcomes. identified when the data were Likewise, when the side of grouped to incorporate the variables. psoas tension was taken into account, The female subjects experienced a it could not be determined which side, wide variety of changes but were the if any, exhibited gluteus maximus most likely to have a decrease in force

The Effects of Thoracolumbar Manipulation on Gluteus Maximus Force Production

weakness. The comparisons were amount of psoas tension which random and unrevealing. resulted in a positive Modified Perhaps the most significant Thomas Test was not significant observation of this study is the enough to have an effect on the relationship between the gluteus maximus. It has been manipulation group and the range of speculated that a more severe form of the mean changes recorded (Figure 1). shortened psoas may have provided a Analysis revealed the right gluteus better way to analyze. A true psoas maximus force production of the contracture following an event of manipulated group demonstrated a psoas strain might have been a more higher range of mean force production pronounced way to examine the compared to the other three groups. response following manipulation. In However, since this was an incidental this sampling, additional questioning finding and not what was included in of why there was increased psoas the null hypothesis, statistical analysis tension would have been helpful in on the significance of this was not further screening of the participants. If performed. Therefore it cannot be the cause was simply due to a speculated as to the interpretation of shortened muscle from extended this finding. periods of sitting it is possible that this While no significant statistical would not result in the same conclusions can be drawn from the relationship with decreased gluteus data, analysis of this study will drive maximus force production. future research, and address Furthermore, the relatively weaknesses within this study small sample size of this study’s specifically. Further research must participants made it difficult to rule prove that the Modified Thomas Test out the outliers in the results. An is the best method for determining the error in the screening process or the tension of the psoas muscle. recording of force production in a few Additionally, further clarification of individuals might have been enough to the suggested relationship of skew the remainder of the results. hypertonic agonists, and therefore This is in part a portion of the inhibited antagonists, in the form of concerns which the investigators have weakness. The theoretic construct with the controls of the methodology. seems to support this, however the One concern is of the isolation literature is just too scarce of studies of the gluteus maximus muscle when to examine this. Prior to conducting having the subjects extend at the hip interventional experiments, the with slight external rotation, as correlation between the strength of described by Kendal (6). Several the gluteus maximus and psoas muscles in the posterior thigh have a tension should be examined. role of hip extension. Further If it is further suggested that investigation would be required to psoas hypertonicity is in fact related determine the precision of the to gluteus maximus strength, then the investigators isolating the gluteus degree of psoas tension required for maximus as was intended. this inhibition should be investigated. Timing could have also played It is possible that within this study, the a role in data recording. This study

The Effects of Thoracolumbar Manipulation on Gluteus Maximus Force Production

had two examiners and a limited the lasting effects of one manipulation amount of time to assess the subjects are difficult to identify. In clinical due to the constraints of the setting. practice, with less control, effects are The instantaneous neurological effects seldom seen after one treatment. It of manipulation could have been generally takes consistent treatment missed due to the increased time it to change physiology. Expecting took following the manipulation until change in physiology after one the force production measurements intervention is likely unrealistic. were taken. The neurological Future research will benefit by literature of manipulation, though examining similar functional growing, is still relatively scarce. This properties after further understanding deems it difficult to identify what the some of the basic tenants of the optimal window for measuring the original hypothesis. When performed, effects is. Future studies will benefit they should focus on the general from a more diverse understanding of population, taking all possible the timing of changes prior to and precautions to better control the after manipulation, possibly through methods of the interventions. In the use of electromyography. addition to examining the relationship Additionally, the neurological between the psoas and the gluteus differences between manipulation and maximus, this principle can be applied mobilization need further study. In to other agonist and antagonistic this experiment, the control group muscles in the body, taking into was the group receiving a consideration the appropriate spinal mobilization. It has been levels. hypothesized that spinal mobilization affects different sensory beds than References manipulation, though both do have 1. Bolton, Philip S., Budgell, Brian S., effect over the mechanoreceptors. (1) Spinal manipulation and spinal Therefore the mechanoreceptor mobilization influence different axial stimulation in both groups may have sensory beds. Medical Hypothesis 66 affected surrounding muscles, though (2006): 258-262. Web. the results were inconclusive in both 2. Chaitow, Leon. Soft-tissue groups. This study would have Manipulation: a Practitioner's Guide to benefited from an additional control the Diagnosis and Treatment of Soft group in which there was no Tissue Dysfunction and Reflex intervention at all. Activity. Rochester, VT: Healing Arts, Finally, the subjects consisted 1988. Print. of chiropractic students. This 3. DiGiovanna, Eileen L., Stanley population contains people who have Schiowitz, and Dennis J. Dowling. An been receiving spinal manipulations Osteopathic Approach to Diagnosis regularly since being at school. It is and Treatment. Philadelphia: difficult to determine the effect an Lippincott Williams and Wilkins, additional manipulation has on 2005. Print. someone who has been receiving 4. Dvořák, Jiři, Musculoskeletal treatment each week since beginning Manual Medicine Diagnosis and school. Even in a different population,

The Effects of Thoracolumbar Manipulation on Gluteus Maximus Force Production

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