Jean P. Boucher

Quadriceps femoris muscle activity in patellofemoral pain syndrome

To elucidate and attempt to dissociate the two mech anisms, neuromuscular and mechanical, underlying pa tellofemoral pain syndrome, 18 subjects, divided into two groups based on a diagnosis of patellofemoral pain syndrome and the knee Q angle, were studied. The control group was asymptomatic and exhibited a nor mal Q angle (mean, 8.25°), whereas the other group, diagnosed as patellofemoral pain syndrome patients, reported knee pain and had an above-normal Q angle (mean, 21.05°). All subjects were tested for isometric maximum knee extension at 90°, 30°, and 15° of knee flexion while they were seated in a special restraining chair. During testing, surface electromyography at the oblique and long fibers of the vastus medialis, and at the vastus lateralis were recorded along with the knee moment of force. The integrated electromyographic signals associated with the peak torque for all of the vastus muscles, along with the vastus medialis obli quus :vastus lateralis and vastus medialis longus:vastus lateralis activity ratios showed no significant differences between groups nor between the three angles, sug gesting that all vasti measured were consistently active throughout the studied range of motion. This suggests that the neural drive was not affected in the patellofem oral pain syndrome patients. However, when the five patients showing the largest Q angles were isolated, they revealed a significantly smaller vastus medialis obliquus:vastus lateralis ratio when compared to the other group. The same ratio was also significantly smaller at 15° compared to 90°. These results did demonstrate that in advanced cases of patellofemoral pain syndrome the vastus medialis may even be less active relative to the vastus lateralis in the last degrees of extension compared to 90°. Furthermore, one may suggest that in patellofemoral pain syndrome the me chanical disturbances are exhibited first, at which time the vastus medialis atrophy, if present, would have a mechanical origin.

HEART RATE VARIABILITY MODULATION AFTER MANIPULATION IN PAIN-FREE PATIENTS VS PATIENTS IN PAIN

BACKGROUND The purpose of this study was to examine heart rate variability (HRV) in the presence or the absence of pain in the lower back, while receiving one chiropractic treatment at L5 from either a manually assisted mechanical force (Activator) or a traditional diversified technique spinal manipulation. METHODS A total of 51 participants were randomly assigned to a control (n = 11), 2 treatment, or 2 sham groups (n = 10 per group). Participants underwent an 8-minute acclimatizing period. The HRV tachygram (RR interval) data were recorded directly into a Suunto watch (model T6; FitzWright Company Ltd, Langley, British Columbia, Canada). We analyzed the 5-minute pretreatment and posttreatment intervals. The spectral analysis of the tachygram was performed with Kubios software. RESULTS All groups decreased in value except the control group that reacted in the opposite direction, when comparing the pretests and posttests for the high-frequency component. The very low frequency increased in all groups except the control group. The low frequency decreased in all groups except the sham pain-free group. The low frequency-high frequency ratio decreased in the treatment pain group by 0.46 and in the sham pain-free group by 0.26. The low frequency-high frequency ratio increase was 0.13 for the sham pain group, 0.04 for the control group, and 0.34 for the treatment pain-free group. The mean RR increased by 11.89 milliseconds in the sham pain-free group, 18.65 milliseconds in the treatment pain group, and 13.14 milliseconds in the control group. The mean RR decreased in the treatment pain-free group by 1.75 milliseconds and by 0.01 milliseconds in the sham pain group. CONCLUSION Adjusting the lumbar vertebrae affected the lumbar parasympathetic nervous system output for this group of participants. Adaptation in the parasympathetic output, reflected by changes in high frequency, low frequency, and very low frequency, may be independent of type of adjustment. Therefore, the group differences found in the modulation of the HRV would seem to be related to the presence or absence of pain. The autonomic nervous system response may be specific and sensitive to its effectors organ.

Pain Effect on Monosynaptic and Polysynaptic Reflex Inhibition

OBJECTIVE Determine the electrophysiological effects of anterior knee pain using monosynaptic and polysynaptic reflexes. DESIGN A pretest/posttest control group experimental design with repeated measures. SETTING All tests were performed in a university laboratory. PARTICIPANTS Six subjects suffering from patello-femoral dysfunction (PFD) composed the experimental group. These patients were diagnosed and referred by medical and chiropractic doctors. Six healthy subjects were recruited for the control group. INTERVENTION Pain relief by cold application (10 minutes) on the knee. MAIN OUTCOME MEASURES Monosynaptic reflex: H reflex of the superficial portions of the quadriceps femoris. Polysynaptic reflexes: nociceptive flexion response (NFR) of the long head of the biceps femoris. RESULTS Cold application, producing significant pain relief (p < 0.05), did not change H-reflex amplitude (p > 0.05) for both groups and did not show modulation of the NFR. However, the PFD group showed significantly lower pain (p < 0.05) and NFR thresholds (p < 0.05) than the control group. Finally, nociceptive stimulation was applied at the sural nerve during an isometric extension of the knee (20% of maximum electromyographic contraction). After this stimulation, uni-articular extensors, especially the distal fibers of the vastus medialis, showed a longer and stronger inhibition than the bi-articular rectus femoris. CONCLUSIONS Pain episodes do not appear to affect monosynaptic responses. NFR threshold differences found between PFD and control group could be explained by the increased excitability of the nervous system in subjects experimenting painful bouts. Functional implications of these findings are discussed.

Effects of repetitive dynamic contractions upon electromechanical delay.

Abstract The effect of repeated maximal effort isotonic contractions on electromechanical delay was studied. Over 4 days, 17 male subjects performed 400 rapid elbow flexion trials. The kinematics and surface electromyographic (EMG) activity of the biceps brachii of these subjects were recorded. The period from the onset of the EMG until the beginning of movement was defined as the electromechanical delay. The period from the beginning of movement until the end of the EMG was defined as the second component of the contraction. Over the 4 day period there was an increase in the speed of limb movement. The mean power frequency and the duration of the EMG during the electromechanical delay did not change, while the root-mean-square amplitude increased. The duration of the EMG during the second component of the contraction remained stable. The mean power frequency and the root-mean-square amplitude of the EMG during the second component of the contraction increased with the speed of limb movement. We conclude that the faster contractions were a result of changes in motor unit recruitment during the second component of the contraction, rather than in the electromechanical delay.

Effects of a manually assisted mechanical force on cutaneous temperature.

OBJECTIVE Digitized infrared segmental thermometry (DIST) is a tool used for measuring cutaneous temperature (CT). This project ascertains the effect of a manually assisted mechanical force producing a chiropractic adjustment in the lumbar spine after the Activator Methods Chiropractic Technique on CT during 2 different time recording periods (TRPs). METHODS Sixty-six healthy subjects (36 women and 30 men) without acute low back conditions or symptoms were recruited. Subjects were randomly divided into 2 groups based on the length of the acclimatization period (8 or 30 minutes; TRP(8) and TRP(30), respectively). In turn, each recording period group was divided into 3 subgroups (n = 11 per subgroup): treatment, sham, and control subgroups. Bilateral DIST was conducted at L-4 (TRP(30)) and L-5 (TRP(8)) using infrared cameras (Subluxation Station Insight 7000; Chiropractic Leadership Alliance, Mahwah, NJ). RESULTS Before treatment (t(-0.5)), the TRP(8) CT was significantly different between the ipsilateral and the contralateral sides for all subgroups. At 10 minutes (t(10)) after intervention, CT increased significantly (P < .05) for the treatment group but not for the sham and control groups. In contrast, there were no significant differences in the TRP(30) CT before treatment between the ipsilateral and the contralateral sides; but at t(10), CT was significantly (P < .05) greater for all 3 subgroups compared with preintervention CT. CONCLUSION Contacting the skin with the instrument with (treatment group TRP(30)) or without (sham group TRP(30)) a thrust with a sustained pressure stronger than the loading principle taught in the Activator Methods Chiropractic Technique protocol or a thrust respecting the standard loading principle (treatment group TRP(8)) of the instrument produced a CT cooling immediately after the adjustment. Furthermore, we observed that when contacting the skin with the instrument with a thrust respecting the standard loading principle (treatment group TRP(8)) of the instrument, it produced a secondary cooling at t(5) followed by a rewarming at t(10). Finally, contacting the skin with the instrument without a thrust and respecting the standard loading principle (sham TRP(8)) of the instrument did not produce a CT change.

PARASPINAL CUTANEOUS TEMPERATURE MODIFICATION AFTER SPINAL MANIPULATION AT L5

OBJECTIVE The purpose of this study was to investigate local paraspinal cutaneous temperature (CT) modifications after spinal manipulative therapy at L5. METHODS Twenty subjects with acute low back symptoms were randomly assigned to either a treatment or a sham group (n = 10 per group). Subjects underwent an 8-minute acclimatizing period. Temperature was measured bilaterally with infrared cameras at the L5 level. In the treatment group, a traditional chiropractic manipulation (lumbar roll technique with a pisiform contact on the ipsilateral mamillary of L5) was delivered, whereas with the sham group, the same technique was used, but no thrust was applied. Cutaneous temperature control measurements were taken 2 minutes before (t(-2)) and immediately after the intervention (t(0)) and at 1, 3, 5, and 10 minutes postintervention (t(1), t(3), t(5), and t(10), respectively). RESULTS At t(0), CT in the treatment group on the treatment side (ipsilateral side) warmed up by 0.2 degrees F, whereas in the sham group, there were no significant temperature modifications on either side. At t(3) relative to t(0), CT in the treatment group on the treatment side warmed by approximately 0.6 degrees F, whereas the contralateral side (nontreatment side) cooled. In the treatment group, significant differences were noted between sides (F = 13.36, P = .002, P = .932) and sides x times (F = 2.97, P = .016, P = .838). CONCLUSION The effects of a lumbar spine manipulation appear noticeable by changes in paraspinal CT measurements at the level of L5. However, the meaning and mechanisms of CT modifications at L5 are still being investigated.

Practice Effects on the Timing and Magnitude of Antagonist Activity during Ballistic Elbow Flexion to a Target

This study examined changes in antagonist timing and magnitude in response to ballistic elbow flexion practice. Seventeen men performed 400 ballistic elbow flexion trials to a target in the horizontal plane over 4 days of testing. A potentiometer and microswitch system at the elbow axis of rotation of a manipulandum recorded angular displacement and movement onset. Surface electrodes (Beckman Ag/AgCl) monitored the triceps brachii lateral head, and the electromyographic (EMG) signals were bandpassed between 20 and 300 Hz. The antagonist EMG burst was divided in two: early low-level activity (ANT1), and the large portion of the burst which occurs near target achievement (ANT2). Movement time decreased from 178 ms on the first test day to 136 ms on the last session. As practice improved the speed of limb movement, onset of the first component (ANT1) remained unchanged, while the second component (ANT2) started earlier. The magnitude of both portions of the antagonist burst increased from the first to last test day, but the change in ANT2 relative to ANT1 was more pronounced. These findings are used to explain discrepant observations in the literature for the temporal measure.

A Comparison of Statistical Models for Calculating Reliability of the Hoffmann Reflex.

The Hoffmann reflex is obtained through surface electromyographic recordings, and it is one of the most common neurophysiological techniques in exercise science. Measurement and evaluation of the peak-to-peak amplitude of the Hoffmann reflex has been guided by the observation that it is a variable response that requires multiple trials to obtain a stable mean. As a result, reliability assessment of the Hoffmann reflex has thus far been limited to trial-to-trial variability or the mean of multiple trials across test days to evaluate day-to-day variability, without considering how the two dimensions of measurement interact to affect test–retest reliability. This article compares two analysis of variance models for reliability assessment of the peak-to-peak amplitude of the Hoffmann reflex: one model incorporated both days and trials, and the other used the mean of multiple trials on each test day. The intraclass correlation coefficient calculated from an analysis of variance model that incorporated both trial-to-trial and day-to-day error variances was R = .93. Using the mean of the trials for each test day as a single score resulted in a decrease in the intraclass correlation coefficient (R 2,1 = .76). This study demonstrated that an analysis of variance model that accounts for both trial-to-trial and day-to-day error variances provided a higher estimate of reliability. Further, reliability estimation based on the interaction between both trials and days revealed that a schedule with additional test days had a disproportionate impact upon securing a reliable measure of Hoffmann reflex amplitude.

Inflammatory response following a short-term course of chiropractic treatment in subjects with and without chronic low back pain☆

OBJECTIVE Inflammatory markers interleukin-6 (IL-6) and C-reactive protein (CRP) have not been evaluated in response to a short course of lumbar spinal manipulation. The purpose of this study is to observe the responses of inflammatory markers (IL-6 and CRP) after a series of 9 chiropractic spinal manipulations. METHODS Twenty-one participants were assigned to a treatment or a control group. Only the treatment group received 9 chiropractic interventions. Pre- and postintervention measures were recorded for blood samples for detection of proinflammatory cytokines IL-6 and CRP. RESULTS Mediators of inflammation (IL-6 and high-sensitivity CRP) were modified by the intervention received in the treatment group, and the effect size demonstrated a tendency toward the control group values. CONCLUSION A total of 9 chiropractic lower back manipulations caused the mediators of inflammation to present a normalization response in individuals suffering from chronic low back pain.

Consistency of cutaneous thermal scanning measures using prone and standing protocols: a pilot study.

OBJECTIVE The goal of this pilot study was to measure paraspinal cutaneous temperature (PCT) in the prone vs standing position. METHODS Ten symptom-free participants were evaluated. Paraspinal cutaneous temperature was recorded. Subjects were acclimated to the treatment room in a prone position for 8 minutes before the PCT was measured. After the prone PCT reading, patients stood. A standing PCT measurement was then taken. RESULTS Paraspinal cutaneous temperature was marginally warmer when subjects were standing vs prone (PCT difference, 0.25 degrees C +/- 0.64 degrees C and 0.62 degrees C +/- 0.67 degrees C for left and right sides, respectively). The right and left side differential was the same in the prone and standing positions. There was a positive Pearson correlation (0.802-0.803; P < .000) between the standing and prone positions for both left and right sides. CONCLUSION There are no differences between the prone or standing PCT measures if symptom-free subjects are given 8 minutes to acclimate before recording PCT measures.