John N. Howell

Muscle stiffness, strength loss, swelling and soreness following exercise-induced injury in humans.

1. In order to study injury‐related changes in muscle stiffness, injury to the elbow flexors of thirteen human subjects was induced by a regimen of eccentric exercise. 2. Passive stiffness over an intermediate range of elbow angles was measured with a device which held the relaxed arm of the subject in the horizontal plane and stepped it through the range of elbow angles from 90 deg to near full extension at 180 deg. The relation between static torque and elbow angle was quite linear over the first 50 deg and was taken as stiffness. 3. Stiffness over this range of angles more than doubled immediately after exercise and remained elevated for about 4 days, and may result from low level myofibrillar activation induced by muscle stretch. 4. Arm swelling was biphasic; arm circumference increased by about 3% immediately after exercise, fell back toward normal, then increased by as much as 9% and remained elevated for as long as 9 days. 5. Ultrasound imaging showed most of the swelling immediately following the exercise to be localized to the flexor muscle compartment; subsequent swelling involved other tissue compartments as well. 6. Muscle strength declined by almost 40% after the exercise and recovery was only slight 10 days later; the half‐time of recovery appeared to be as long as 5‐6 weeks.

Relationship between muscle swelling and stiffness after eccentric exercise

PURPOSE The time courses of muscle compartmental swelling and passive stiffness change were measured to determine whether muscle compartmental swelling accounted for increased stiffness. METHODS Eleven untrained female college students exercised eccentrically by lowering a weight with their elbow flexors. Measurements of muscle compartment volume, stiffness, relaxed elbow angle, circumference, and pain were recorded before exercise, immediately after exercise, and 1-5, 7, 9, and 11 d after exercise. Muscle compartment volume was calculated from cross-sectional ultrasound images taken along the upper arm. Stiffness was measured using a device that extended the elbow and recorded the torque required to hold the forearm at successive angles. RESULTS Elbow flexor volume increased gradually to peak on the fourth day (26.1 +/- 4.3%, P < 0.05) and then decreased to baseline values over days 7-11. Stiffness increased immediately after exercise (59.9 +/- 14.1%, P < 0.05) and remained at or above this level until decreasing to pre-exercise levels over days 7-11. CONCLUSIONS This suggests that muscle swelling does not account for the sudden increase in stiffness of the elbow flexor muscles within the first 48 h after exercise but may play a role in the subsequent time course of stiffness.

In vivo Measurement of Fascicle Length and Pennation Angle of the Human Biceps femoris Muscle

The purpose of this investigation was to measure in vivo fascicle length (Lfas) and pennation angle (PA) of the long head of the biceps femoris muscle (BFlh m.) at different hip and knee angles while the muscle was relaxed using ultrasonography (US). Data were collected from 18 healthy females (23.0 ± 1.8 years). To validate the measurements of the Lfas and PA, the US measurements on cadavers (n = 5), embalmed with the hip and knee in anatomical position, were compared to actual fiber lengths and PA from the dissected muscles. US images from volunteer subjects were recorded when the hip joint was positioned at 0°, 45° and 90° of hip flexion, and at each hip position, the knee joint was placed at 0°, 45° and 90° from full extension. The images were digitized to measure Lfas and PA. Results showed no significant differences between US and direct measurements of the Lfas and PA on the cadaver BFlh m. (p > 0.05). Lfas and PA changed significantly between the different hip and knee positions in volunteer subjects (p < 0.05). Changes in the Lfas and PA are more sensitive to changes in hip position with the knee position constant than to changes in knee position with the hip position constant. This difference may be related to the larger muscle moment arm at the hip resulting in greater excursion of the muscle with changing hip position. Based on the changes in Lfas with changing joint positions, BFlh sarcomere length was estimated to occupy a portion of the ascending limb, the plateau and descending limb of the length-tension relationship over the range of motion studied. US scanning is valid and reliable for measuring Lfas and PA of the BFlh m. An understanding of the dynamic nature of muscle architecture will assist in determining effective and efficient clinical evaluation and rehabilitation techniques.

The relationship between elbow flexor volume and angular stiffness at the elbow

OBJECTIVE: The purpose of this experiment was to determine if a correlation exists between the volume of the elbow flexors and angular stiffness at the elbow, and to determine the contribution of the biceps brachii and the brachialis muscles to angular stiffness. DESIGN: This study is a descriptive, correlational study and presents a graphical model of the passive properties of muscle. BACKGROUND: The correlation between arm volume and angular stiffness has been shown, but the measurement of arm volume was not specific to the structures being strained. Pre-positioning a bi-articular muscle by stretching over one joint decreases the range of motion at the other joint and may affect the stiffness. METHODS: Angular stiffness at the elbow of 14 female and 15 male volunteers was measured, and the volume of the elbow flexors was calculated from compounded ultrasound imaging. Initial biceps length was set by pre-positioning the shoulder in two different positions. RESULTS: A significant linear relationship was observed between the slope of phase 1 of the stiffness curve and volume of the elbow flexors in both horizontal flexion (r = 0.92) and horizontal extension (r = 0.79) of the shoulder. Phase 2 of the stiffness curve showed no linear relationship to muscle volume in either shoulder position (flexion, r = 0.22; extension r = 0.33). The slopes of phases 1 and 2 were significantly greater with the shoulder in horizontal extension than in horizontal flexion. CONCLUSION: The volume of the elbow flexor muscles is a good predictor of angular stiffness in phase 1 of the curve. A model of the additive contribution of the biceps and brachialis muscles is presented to account for the increased stiffness in the shoulder extended position. RELEVANCE: Recognition of the correlation between muscle volume and stiffness, coupled with understanding that pre-positioning a bi-articular muscle may affect muscle stiffness may aid the clinician in accurately assessing muscle stiffness in patients with connective tissue disorders, neurological dysfunction and contractures.

The virtual haptic back for palpatory training

This paper discusses the Ohio University Virtual Haptic Back (VHB) project, including objectives, implementation, and initial evaluations. Haptics is the science of human tactile sensation and a haptic interface provides force and touch feedback to the user from virtual reality. Our multimodal VHB simulation combines high-fidelity computer graphics with haptic feedback and aural feedback to augment training in palpatory diagnosis in osteopathic medicine, plus related training applications in physical therapy, massage therapy, chiropractic therapy, and other tactile fields. We use the PHANToM haptic interface to provide position interactions by the trainee, with accompanying force feedback to simulate the back of a live human subject in real-time. Our simulation is intended to add a measurable, repeatable component of science to the art of palpatory diagnosis. Based on our experiences in the lab to date, we believe that haptics-augmented computer models have great potential for improving training in the future, for various tactile applications. Our main project goals are to: 1. Provide a novel tool for palpatory diagnosis training; and 2. Improve the state-of-the-art in haptics and graphics applied to virtual anatomy.

Intermittent pneumatic compression effect on eccentric exercise-induced swelling, stiffness, and strength loss

OBJECTIVE The purpose was to determine if intermittent pneumatic compression (IPC) affects muscle swelling, stiffness, and strength loss resulting from eccentric exercise-induced injury of the elbow flexors. We hypothesized that the compression would decrease swelling and stiffness. DESIGN Repeated measures design with a before-after trial comparison within each day. SETTING Conducted at a university Somatic Dysfunction Laboratory. SUBJECTS Twenty-two college women students were studied. They had not been lifting weights or otherwise participating in regular arm exercise for the 6 months before the study. They had no history of upper extremity injury or cardiovascular disease. INTERVENTIONS Subjects performed one bout of eccentric exercise at a high load to induce elbow flexor muscle injury. Uniform IPC was applied on the day of exercise and daily for 5 days at 60mmHg, 40 seconds inflation, 20 deflation for 20 minutes. MAIN OUTCOME MEASURES Measurements of arm circumference, stiffness, and isometric strength were recorded before exercise, then before and after IPC for 5 days after exercise. Passive muscle stiffness was measured on a device that extends the elbow stepwise and records the torque required to hold the forearm at each elbow angle. RESULTS Circumference and stiffness increased and strength decreased during the 5 days post-exercise (p < .05). IPC significantly decreased circumference and stiffness most notably on days 2 and 3 after exercise (p < .05). The strength loss was not affected by IPC. CONCLUSION IPC is effective in temporarily decreasing the swelling and stiffness after exercise-induced muscle injury.

The virtual haptic back: A simulation for training in palpatory diagnosis

BackgroundModels and simulations are finding increased roles in medical education. The Virtual Haptic Back (VHB) is a virtual reality simulation of the mechanical properties of the human back designed as an aid to teaching clinical palpatory diagnosis.MethodsEighty-nine first year medical students of the Ohio University College of Osteopathic Medicine carried out six, 15-minute practice sessions with the VHB, plus tests before and after the sessions in order to monitor progress in identifying regions of simulated abnormal tissue compliance. Students palpated with two digits, fingers or thumbs, by placing them in gimbaled thimbles at the ends of PHANToM 3.0® haptic interface arms. The interface simulated the contours and compliance of the back surface by the action of electric motors. The motors limited the compression of the virtual tissues induced by the palpating fingers, by generating counterforces. Users could see the position of their fingers with respect to the back on a video monitor just behind the plane of the haptic back. The abnormal region varied randomly among 12 locations between trials. During the practice sessions student users received immediate feedback following each trial, indicating either a correct choice or the actual location of the abnormality if an incorrect choice had been made. This allowed the user to feel the actual abnormality before going on to the next trial. Changes in accuracy, speed and Weber fraction across practice sessions were analyzed using a repeated measures analysis of variance.ResultsStudents improved in accuracy and speed of diagnosis with practice. The smallest difference in simulated tissue compliance users were able to detect improved from 28% (SD = 9.5%) to 14% (SD = 4.4%) during the practice sessions while average detection time decreased from 39 (SD = 19.8) to 17 (SD = 11.7) seconds. When asked in anonymous evaluation questionnaires if they judged the VHB practice to be helpful to them in the clinical palpation and manual medicine laboratory, 41% said yes, 51% said maybe, and 8% said no.ConclusionThe VHB has potential value as a teaching aid for students in the initial phases of learning palpatory diagnosis.

Muscle functional magnetic resonance imaging and acute low back pain: a pilot study to characterize lumbar muscle activity asymmetries and examine the effects of osteopathic manipulative treatment

BackgroundMuscle functional magnetic resonance imaging (mfMRI) measures transverse relaxation time (T2), and allows for determination of the spatial pattern of muscle activation. The purposes of this pilot study were to examine whether MRI-derived T2 or side-to-side differences in T2 (asymmetries) differ in low back muscles between subjects with acute low back pain (LBP) compared to asymptomatic controls, and to determine if a single osteopathic manipulative treatment (OMT) session alters these T2 properties immediately and 48-hours after treatment.MethodsSubjects with non-specific acute LBP (mean score on 1-10 visual analog score = 3.02 ± 2.81) and asymptomatic controls (n = 9/group) underwent an MRI, and subsequently the LBP subjects received OMT and then underwent another MRI. The LBP subjects reported back for an additional MRI 48-hours following their initial visit. T2 and T2 asymmetry were calculated from regions of interest for the psoas, quadratus lumborum (QL), multifidus, and iliocostalis lumborum/longissimus thoracis (IL/LT) muscles.ResultsNo differences were observed between the groups when T2 was averaged for the left and right side muscles. However, the QL displayed a significantly greater T2 asymmetry in LBP subjects when compared to controls (29.1 ± 4.3 vs. 15.9 ± 4.1%; p = 0.05). The psoas muscle also displayed a relatively large, albeit non-significant, mean difference (22.7 ± 6.9 vs. 9.5 ± 2.8%; p = 0.11). In the subjects with LBP, psoas T2 asymmetry was significantly reduced immediately following OMT (25.3 ± 6.9 to 6.1 ± 1.8%, p = 0.05), and the change in LBP immediately following OMT was correlated with the change in psoas T2 asymmetry (r = 0.75, p = 0.02).ConclusionCollectively, this pilot work demonstrates the feasibility of mfMRI for quantification and localization of muscle abnormalities in patients with acute low back pain. Additionally, this pilot work provides insight into the mechanistic actions of OMT during acute LBP, as it suggests that it may attenuate muscle activity asymmetries of some of the intrinsic low back muscles.

A stiffness discrimination experiment including analysis of palpation forces and velocities.

Introduction: The incorporation of haptics, the sense of touch, into medical simulations increases their capabilities by enabling the users to “feel” the virtual environment. We are involved with haptics-augmented virtual reality training for palpatory diagnosis. We have developed a stiffness discrimination program to train and test users in finding subtle differences in human tissue stiffness for medical diagnoses. In this article, we studied the effect of surface stiffness on the stiffness discrimination task and analyzed the palpation force and speed during haptic exploration. Methods: The ability to discriminate stiffness differences was studied by means of a psychophysical experiment with 13 second-year medical students (eight women and five men). Subjects were asked to identify the stiffer of two virtual computer-generated surfaces (top surfaces of two cylinders) by means of a PHANToM Omni (SensAble Inc.) haptic device with a modified stylus to accommodate their fingers. The modification of the stylus provided the mechanical advantage to simulate surface stiffness values that are beyond the original capability of the haptic device. An adaptive two-alternative forced-choice procedure was used on each trial. Palpation velocity and force vectors were recorded directly from the haptic device for further analyses. Weber fraction was determined by using an automated mastery algorithm. Results: Four standard stiffness values (0.25, 0.50, 1.00, and 1.25 N/mm), typical of the stiffness range of human soft tissues, were used as references. The average experimental Weber fractions observed were 0.20, 0.27, 0.26, and 0.30, respectively, with higher Weber fractions corresponding to lower stiffness discrimination ability. At 1.00 and 1.25 N/mm standard stiffness, the correlation analysis for Weber fraction and the palpation speed revealed significant differences (P < 0.05). These differences suggested that the subjects with a higher palpation velocity tended to have a higher Weber fraction. There was no significant difference between male and female subjects. There was no significant difference between subjects new to the haptic device and those who had used it previously. The average amount of force that was applied by the subjects to the standard stiffness side and the comparison stiffness side within the sessions was not significantly different. However, the subjects increased the average force they applied with increasing standard stiffness value across the sessions (P < 0.05). Conclusions: For the four standard stiffness values investigated, 0.25, 0.50, 1.00, and 1.25 N/mm, the resulting average stiffness-discrimination Weber fractions were 0.20, 0.27, 0.26, and 0.30, respectively. The average of the forces applied by the subjects was constant within a single session (with a single standard stiffness value). This average force monotonically increased as the standard stiffness value increased across the sessions. We also found positive correlation between the Weber fraction and the palpation speed in the sessions tested with 1.00 and 1.25 N/mm standard stiffness. This correlation suggested that higher speed is related to lower sensitivity in discrimination of stiffness differences for these two standard stiffness values. Our results are applicable to tasks involving stiffness discrimination between multiple objects.

Evidence for t-tubular conduction failure in frog skeletal muscle induced by elevated extracellular calcium concentration

SummaryIn order to investigate the mechanism by which elevated extracellular calcium ions decrease tetanus tension in frog skeletal muscle, we made mechanical, electrophysiological and photographic measurements on single fibres or small bundles of fibres. Three lines of evidence point to t-tubular conduction failure as the primary mechanism of action of high calcium. They are (1) a decrease in amplitude of the late afterpotential, (2) attentuation or elimination of the notch and hump configuration of the early afterpotential, and (3) the appearance of wavy myofibrils in the axial core of fibres during tetanus. These effects are fully reversible and are shared by other bivalent cations. High calcium concentration causes a change in the time course of the early afterpotential but does not alter the passive cell membrane characteristics, as reflected by the time course of decay of applied hyperpolarizing pulses.