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Department of Functional Restoration (Fredericson), Division of Physical Medicine and Rehabilitation (Fredericson), Department of Human Biology (White), and Biomotion Research Laboratory, Department of Mechanical Engineering (MacMahon, Andriacchi), Stanford University, Stanford, CA.
Department of Functional Restoration (Fredericson), Division of Physical Medicine and Rehabilitation (Fredericson), Department of Human Biology (White), and Biomotion Research Laboratory, Department of Mechanical Engineering (MacMahon, Andriacchi), Stanford University, Stanford, CA.
Department of Functional Restoration (Fredericson), Division of Physical Medicine and Rehabilitation (Fredericson), Department of Human Biology (White), and Biomotion Research Laboratory, Department of Mechanical Engineering (MacMahon, Andriacchi), Stanford University, Stanford, CA.
Department of Functional Restoration (Fredericson), Division of Physical Medicine and Rehabilitation (Fredericson), Department of Human Biology (White), and Biomotion Research Laboratory, Department of Mechanical Engineering (MacMahon, Andriacchi), Stanford University, Stanford, CA.
The iliotibial band (ITB) is a thickened fascia that originates at the tubercle of the iliac crest, runs distally down the lateral side of the thigh, and inserts on the lateral patellar retinaculum, tubercle of the tibia, and proximal fibular head. Along its length, the ITB provides attachments for the tensor fascia lata, gluteal muscles, and the vastus lateralis (fig 1).
In dynamic walking or running, the ITB passes over the lateral femoral epicondyle just after foot strike, coinciding with slightly less than 30° of knee flexion.
Patients with ITBFS complain of severe burning at the area around and under the lateral epicondyle secondary to tightness, frictional irritation, and inflammation of the posterior fibers of the ITB and the periosteum of the epicondyle.
This study compares the effectiveness of the traditional standing ITB stretch and 2 modifications to help determine the most efficient and effective stretch for ITBFS recovery protocols.
Methods
Previous studies have been hindered by human measurement error.
This study minimizes such errors by using a new approach developed at the Biomotion Laboratory at Stanford University, Stanford, CA, to evaluate stretch effectiveness.
MacMahon JM, Chaudhari AM, Fadil M, Andriacchi TP. A prospective study of iliotibial band flexibility and abductor strength—implications for marathon training success. In: Proceedings of the 24th Annual Meeting of the American Society of Biomechanics; 2000 July 19-22; Chicago (IL). p 179.
Each subject's biomechanics were captured as a 3-dimensional image by using a 4-camera gait acquisition systema with a forceplate. Change in ITB tissue length and the force generated within the stretched complex were measured for each stretch. The data was combined and analyzed by using kinetic values assessment.
The 3 ITB stretches evaluated in this study were selected for their common usage and prescription, ease of implementation, and effectiveness.
All were standing stretches that can be performed without aid. Stretch A begins with the subject standing upright. The leg being stretched is extended and adducted across the other leg. The subject exhales while slowly flexing the trunk in a direction lateral to the opposite side. This motion continues until a stretch is felt on the side of the hip around the greater trochanter (fig 2).
Stretch B is the same as stretch A except the hands are clasped overhead, and the arm on the same side of the leg being stretched is stretched in the same direction. Stretch C is the same as stretch B except the subject no longer extends arms overhead but diagonally downward.
The effectiveness of each stretch was evaluated based on change in ITB tissue length and the force generated within the stretched ITB complex. The tissue length change was measured as the percentage change between an upright standard and the end point of a stretch. Generated force was measured by using the external adduction moments about the hip and knee, which represent the net torque about the hip and knee centers. It is assumed that the most effective stretch will increase tissue length and overcome the external moments of the lateral complex.
Five athletes were asked to perform each of the stretches. Stretch sequences were randomized for each subject to prevent a warm-up phenomenon. All 5 subjects were male elite-level distance runners with no history of a lower-leg injury that had required them to miss a competitive season and no history of lower-extremity surgery. To minimize measurement error, the athletes were tested at the same time of day before their afternoon workout. While each subject performed the stretches, a 4-camera system captured the X, Y, and Z coordinates of 6 retroreflective markers affixed to lower body landmarks. The first 3 markers coincided with the ITB complex, including the iliac crest, greater trochanter, and lateral midline of the knee. The other 3 markers, used as reference points, were affixed to the lateral malleolus, lateral calcaneous, and fifth metatarsal (fig 3).
Fig. 3Picture of subject, affixed reflective markers, cameras, and the concealed forceplate under the subject's foot.
From anatomic measurements of each subject, centers of the knee and femoral head were approximated from the markers situated at the lateral midline of the knee and the greater trochanter. Coupled to the camera acquisition system, forceplate measurements were also acquired.
In processing the trials, inverse dynamics combined the marker positions and the force data to determine the external moments for each subject in each stretch. These data were used to determine average adduction moments at the hip and knee as previously described
as the 2 places most affected by the ITB stretches. Hip and knee moments were calculated as the product of the ground reaction vector (Newtons) and the moment arm (meters) to the center of the knee and the femoral head, respectively. All moments were normalized by the individual's weight and height.
Normalized hip and knee adduction moment
Normalized hip and knee adduction moment is determined by the formula (moment arm [m] × ground reaction vector [N])/(BW [N] × H [m]) × 100%, where BW is body weight and H is height. The athletes were asked to stand upright on the concealed forceplate with their feet shoulder's width apart for 30 seconds while the cameras captured their ITB reference distance. Then they were instructed on how to perform 1 of the 3 stretches described previously (fig 2). Once the athletes indicated that they understood the instructions, they were asked to place their ipsilateral foot in the upper right corner of the concealed forceplate, facing the cameras, and to perform the stretch. They were instructed to stop once they felt a “good stretch” and to hold the stretch for 30 seconds. In the last 5 seconds of this time period, the measurement data were collected. The athletes were then instructed to slowly come out of the stretch and to move around for 30 seconds to normalize. This protocol was repeated until each athlete had performed 3 repetitions of each stretch. For each subject's series of stretches, their average ITB length and relevant moments were calculated and averaged. Average measures for each stretch were then compared by using pairwise 2-tailed Student t tests. Statistical significance was defined at the P less than.05 level.
Results
All 3 stretches created statistically significant changes in ITB length (P<.05), but stretch B was consistently most effective in both average ITB length change and in average adduction moments at the hip and knee (table 1).
Tabled
1Table 1: Ensemble average measures for each stretch (A, B, C)
Stretches
Measures
A
B
C
ITB length % increase
9.84
11.15
10.52
Hip adduction moment % (BW · H)
6.80
8.25
7.16
Knee adduction moment % (BW · H)
4.86
5.62
4.75
Statistical comparison
A vs B
B vs C
A vs C
ITB length % increase
†
*
*
Hip adduction moment % (BW · H)
†
Knee adduction moment % (BW · H)
†
*P <.05. †P <.01.
Note. Each stretch consisted of 5 subjects each completing 3 repetitions of each stretch. Statistical analyses were performed using pairwise 2-sided Student t tests.
With stretch A, average ITB length increased by 9.84%. With stretch B, average ITB length increased by 11.15%. With stretch C, average ITB length increased by 10.52%. These differences in change in ITB length between the 3 stretches were statistically significant (P<.05). Average adduction moments at the hip (%[BW × H]) were 6.80 for stretch A, 8.25 for stretch B, and 7.16 for stretch C. There was a statistically significant difference in average hip adduction moments between stretches B and C (P<.01), but not between stretches A and C or A and B. Average adduction moments at the knee (%[BW × H]) were 4.86 for stretch A, 5.62 for stretch B, and 4.75 for stretch C. Again, there was a statistically significant difference between stretches B and C (P<.01), but not between stretches A and C or A and B.
Discussion
Myofascial trigger points, hip abductor muscle inhibition, and fascial adhesions can all contribute to increased tension on the ITB and friction at the ITB-epicondyle point of contact.
A comprehensive stretching protocol is thus a component of a comprehensive treatment protocol to decrease ITB complex tension and restore functional tissue length. This study suggests that adding an overhead arm extension (stretch B) to the most common standing ITB stretch increases average ITB length change and average external adduction moments in elite-level distance runners.
The ITB traverses the lateral lower limb and acts as an anterolateral stabilizer of the knee. Any length changes in the distance from the iliac crest to the greater trochanter must act on the ITB and its encompassed tensor fascia lata. External adduction moments about the knee and the hip must be overcome by forces within the ITB as well. Thus, these measures afford a means of quantifying the internal stretch distance of the ITB and also the forces acting on it to accomplish that stretch.
By using advanced methods and apparatus at the Biomotion Laboratory, this study found that the addition of the overhead arm extension with increased lateral trunk flexion, and to a lesser degree the extension of the arms diagonally down and across the body, are simple techniques that can easily be taught in a clinical setting to improve effectiveness of the standing ITB stretch. These modifications achieved the greatest change in tissue length of the ITB complex, helping the runners produce the maximum stretch. This was supported by their anecdotal statements that the overhead arm extension was “felt” to be the best stretch, suggesting that a 1% to 2% difference in tissue length is physiologically detectable. Because our study selectively examined elite male distance runners, we are unable to generalize these recommendations to other patient populations.
One of the limitations of this study was that we did not directly measure ITB length; rather we estimated changes in length from angular changes in markers. It is possible that extensibility of other tissues such as the gluteals, tensor fascia lata, and vastus lateralis could have contributed to the changes. The errors present in using this measurement technique are dominated by placement of the markers. The errors propagate systematically because each individual's markers were exactly the same for each stretch. However, we believe such potential error was minimized in this study because (1) all placements were made by 1 highly experienced individual; (2) comparisons were between individuals (reducing the significance of systematic errors); and (3) in stretching the individual was quite static (unlike gait testing where skin motion can introduce errors), which limits the potential of movement error. In fact, the system used in this study is so sensitive that breathing patterns can be discerned in the data. Previous reliability measurements have shown that, with the techniques used in this study, errors in determining marker centroids is less than 8mm each. The errors in distance between 2 markers add in quadrature and result in an error of the order of 1.1cm for any given distance. With the distances of the ITB running close to 50cm, this introduces a maximum variation of less than 2.2% of overall length.
This study helps answers the question, Which is the best ITB stretch? By using advanced methods and apparatus at the Biomotion Laboratory, this study suggests that adding an overhead arm extension to the most common lateral ITB stretch increases average ITB length change and average external adduction moments in male elite-level distance runners, and that these differences are statistically significant. Additionally, the use of the methods and equipment used by the Biomotion Laboratory can now be applied to other studies of tissue dynamics, flexibility, and stretch assessment to improve our understanding of such issues.
MacMahon JM, Chaudhari AM, Fadil M, Andriacchi TP. A prospective study of iliotibial band flexibility and abductor strength—implications for marathon training success. In: Proceedings of the 24th Annual Meeting of the American Society of Biomechanics; 2000 July 19-22; Chicago (IL). p 179.
☆No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors(s) or upon any organization with which the author(s) is/are associated.
☆☆Reprint requests to Michael Fredericson, MD, Stanford University Medical Center, Division of Physical Medicine and Rehabilitation, 300 Pasteur Dr, Edwards Bldg R107B, Stanford, CA 94305-5336, e-mail: [email protected] .
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