C. Roger James

Effects of injury proneness and task difficulty on joint kinetic variability

PURPOSE The purpose was to investigate the effects of lower extremity overuse injury proneness and landing height on the variability of selected joint moment characteristics. METHODS Ten subjects from each of two groups (healthy and injury prone) performed 10 landings from a platform (heights: 50, 100, and 200% of maximum vertical jump). Force platform (1000 Hz) and video (200 Hz) information were collected and used to compute ankle, knee, and hip joint moment values during impact (0-100 ms post contact). Moment peak, time to peak, and impulse values were used to determine variability across 10 trials for each subject and height. MANOVAs and univariate follow-up tests were used to assess variability differences between groups and among heights. RESULTS Results revealed ankle moment variability differences (P < or = 0.05; Tukey) between groups for peak and time to peak variables at the 100% and 50% heights, respectively. The injury-prone group exhibited greater variability for the peak variable, whereas the healthy group showed greater variability for the temporal variable. Groups also differed on the impulse variables (P < or = 0.02; MANOVA), but follow-up tests failed to determine specific joints or directions of differences. Both groups exhibited tendencies for greater variability (P < or = 0.05; Tukey) with increases in height up to 100% MVJ and decreases in variability with further height increases. CONCLUSIONS Results suggest that groups differed in joint moment variability, possibly indicating a relationship between variability and overuse injuries, although the variables and directions of differences were inconsistent. For some variables, variability increased and then decreased with height increases for both groups, suggesting a range of heights within which the neuromuscular system adapted.

Relationships between clinical measures of static foot posture and plantar pressure during static standing and walking

BACKGROUND Information is limited about the relationships between clinical measures of static foot posture and peak plantar pressures under the medial column of the foot. The purpose was to examine these relationships during static standing and walking. METHODS A single-group exploratory design using correlation and regression was used to determine relationships. Ninety-two healthy volunteers participated. Clinical measures of static foot posture including arch index, navicular drop and navicular drift were obtained during static standing. Peak plantar pressures under the hallux, medial forefoot, medial midfoot, and medial rearfoot were obtained during standing and walking. FINDINGS Static foot posture was related to peak plantar pressures during standing and walking, but the strengths of relationships ranged from poor to fair. During standing, navicular drop was correlated (P≤0.05) with hallux (r=0.29) and medial forefoot (r=-0.17) pressures, while arch index (r=-0.17) and navicular drift (r=0.25) were correlated (P≤0.05) with hallux pressure. During walking, arch index, navicular drop and navicular drift were correlated (P≤0.05) with hallux and medial forefoot pressures (r range -0.30 to 0.41), while arch index (r=-0.15) and navicular drop (r=0.16) were correlated (P≤0.05) with medial midfoot pressure. Regression models predicted (P≤0.05) hallux (R(2)=0.08) and medial midfoot (R(2)=0.05) pressures during standing, and hallux (R(2)=0.18), medial forefoot (R(2)=0.07), and medial rearfoot (R(2)=0.05) pressures during walking. INTERPRETATION In healthy participants, lower arch foot postures are associated with greater pressures under the hallux and medial mid-foot and lower pressures under the medial forefoot, but the strength of these relationships may be only poor to fair.

Effects of Tai Chi on Gait Kinematics, Physical Function, and Pain in Elderly with Knee Osteoarthritis — A Pilot Study

Our previous study has demonstrated that 6 weeks of Tai Chi exercise significantly improves knee pain and stiffness in elderly with knee osteoarthritis. This study also examine the effects of Tai Chi exercise on gait kinematics, physical function, pain, and pain self-efficacy in elderly with knee osteoarthritis. In this prospective, pretest-posttest clinical trial, 40 men and women (64.4+/-8.3 years) diagnosed with knee osteoarthritis participated in 6 weeks of instructed Tai Chi training, 1 hour/session, 2 sessions/week. The following measures were taken at baseline and the conclusion of the intervention: (a) gait kinematics including stride length, stride frequency, and gait speed quantified using video analysis, (b) physical function, (c) knee pain, and (d) pain self-efficacy. Data were analyzed using repeated MANCOVA, MANOVA, ANOVA and Wilcoxon tests. After 6 weeks of Tai Chi exercise, stride length (p=0.023; 1.17+/-0.17 vs. 1.20+/-0.14 m), stride frequency (p=0.014; 0.91+/-0.08 vs. 0.93+/-0.08 strides/s), and consequently gait speed (p<0.025; 1.06+/-0.19 vs. 1.12+/-0.15 m/s) increased in the participants. Physical function was significantly improved (p<0.001) and knee pain was significantly decreased (p=0.002), while no change was observed in pain self-efficacy. In conclusion, these findings support that Tai Chi is beneficial for gait kinematics in elderly with knee osteoarthritis, and a longer term application is needed to substantiate the effect of Tai Chi as an alternative exercise in management of knee osteoarthritis.

Gender differences among sagittal plane knee kinematic and ground reaction force characteristics during a rapid sprint and cut maneuver.

Abstract Women are more prone to anterior cruciate ligament (ACL) injury during cutting sports than men. The purpose of this study was to examine knee kinematic and ground reaction forces (GRF) differences between genders during cutting. Male and female athletes performed cutting trials while force platform and video data were recorded (180 Hz). Differences (p ≤ .05) were observed between groups for knee flexion at contact and GRF at maximum knee flexion. Women averaged 5.8° less flexion at contact and 1.0 N·(kg·m·s1)−1 greater GRF at maximum flexion. Knee range of motion and peak GRF variables were not significantly different, but women had greater values. Women exhibited technique characteristics believed to increase ACL injury risk, but men exhibiting similar characteristics were also observed and could also be at risk.

2006 Young Investigator Award Winner: lumbosacral nerve root displacement and strain: part 2. A comparison of 2 straight leg raise conditions in unembalmed cadavers.

Study Design. An inferential cadaveric study. Objectives. To compare the displacement and strain of the lumbosacral nerve roots during different conditions of straight leg raise (SLR) with intact foraminal ligaments. Summary of Background Data. Clinicians use sensitizing movements such as dorsiflexion during neurodynamic testing, assuming that these prepositions influence the displacement or strain to the lumbosacral nerve roots. Little is known about the effect of these prepositions on neurodynamic behavior. Methods. Lower limbs and associated nerve roots of 5 unembalmed cadavers (n = 10) were used to evaluate the displacement and strain of the L4, L5, and S1 roots during 2 different SLR conditions. Fluoroscopic images of intraneural metal markers were digitized to evaluate displacement and strain during SLR with no preposition (SLR NPP) of the ankle and SLR with dorsiflexion preposition (SLR DF) of the ankle, respectively. Results. SLR NPP produced larger distal displacement at L5 and S1, (P < 0.001) when compared with SLR DF. Displacement comparisons at L4 were nonsignificant (P = 0.051). While nonsignificant, medium to large effect sizes (0.60–0.96) suggest that SLR DF may produce more strain than the SLR NPP condition. Conclusions. Prepositions of the SLR test alter the displacement and possibly the strain of the lumbosacral nerve roots in the lateral recess.

2006 young investigator award winner : Lumbosacral nerve root displacement and strain Part 1. A novel measurement technique during straight leg raise in unembalmed cadavers

Study Design. A descriptive cadaveric study incorporating a novel nerve root marking technique. Objectives. To describe the displacement and strain of the lumbosacral nerve roots in the lateral recess during straight leg raise (SLR) without disrupting the foraminal ligaments. Summary of Background Data. Previous studies document 2 to 8 mm of lumbosacral nerve root displacement during SLR. Prior dissection methods incorporated laminectomy and facetectomy. Methods. Lower limbs and associated nerve roots of 5 unembalmed cadavers (n = 10) were studied. Metal markers were inserted intraneurally within the lateral recess of L4, L5, and S1 with a modified spinal needle. Fluoroscopic images were digitized to evaluate displacement and strain during SLR. Results. The lumbosacral nerve roots in the lateral recess moved less and experienced less strain during SLR than described in previously published reports. Statistically significant distal displacement occurred at hip positions greater than 60° of flexion at all nerve root levels (P < 0.01). Conclusions. The lumbosacral nerve roots (L4, L5, S1) moved less and underwent less strain during SLR testing than previously reported and may require hip motion greater than 60° to produce substantive displacement in the lateral recess. Additional research is needed to examine the effects of prepositioning during SLR.

The effects of neurodynamic mobilization on fluid dispersion within the tibial nerve at the ankle: an unembalmed cadaveric study

Abstract Objective: To evaluate the effects of neurodynamic mobilization on the fluid dynamics of the tibial nerve in cadavers. Background: Evidence showing patients benefit from neural mobilization is limited. Mechanisms responsible for changes in patient symptoms are unclear. Methods: Bilateral lower limbs of six unembalmed cadavers (n = 12) were randomized into matched pairs and dissected to expose the tibial nerve proximal to the ankle. Dye composed of Toulidine blue and plasma was injected into the nerve. The longitudinal dye spread was measured pre‐ and post‐mobilization. The experimental group received the intervention consisting of 30 repetitions of passive ankle range of motion over the course of 1 minute. The matched control limb received no mobilization. Data were analysed using a 2×2 repeated measures ANOVA with subsequent t‐tests for pairwise comparisons. Results: Mean dye spread was 23·8±10·2 mm, a change of 5·4±4·7% in the experimental limb as compared to 20·7±6·0 mm, a change of −1·5±3·9% in the control limb. The ANOVA was significant (P⩽0·02) for interaction between group (experimental/control) and time (pre‐mobilization/post‐mobilization). t‐test results were significant between pre‐ and post‐mobilization of the experimental leg (P = 0·01), and between control and experimental limbs post‐mobilization (P⩽0·02). Conclusion: Passive neural mobilization induces dispersion of intraneural fluid. This may be clinically significant in the presence of intraneural edema found in pathological nerves such as those found in compression syndromes.

Effects of two neuromuscular fatigue protocols on landing performance.

The purpose of the study was to investigate the effects of two fatigue protocols on landing performance. A repeated measures design was used to examine the effects of fatigue and fatigue protocol on neuromuscular and biomechanical performance variables. Ten volunteers performed non-fatigued and fatigued landings on two days using different fatigue protocols. Repeated maximum isometric squats were used to induce fatigue on day one. Sub-maximum cycling was used to induce fatigue on day two. Isometric squat maximum voluntary contraction (MVC) was measured before and after fatigued landings on each day. During the landings, ground reaction force (GRF), knee kinematics, and electromyographic (EMG) data were recorded. Isometric MVC, GRF peaks, loading rates, impulse, knee flexion at contact, range of motion, max angular velocity, and EMG root mean square (RMS) values were compared pre- and post-fatiguing exercise and between fatigue protocols using repeated ANOVA. Fatigue decreased MVC strength (p0.05), GRF second peak, and initial impulse (p0.01), but increased quadriceps medium latency stretch reflex EMG activity (p0.012). Knee flexion at contact was 5.2 degrees greater (p0.05) during fatigued landings following the squat exercise compared to cycling. Several variables exhibited non-significant but large effect sizes when comparing the effects of fatigue and fatigue protocol. In conclusion, fatigue alters landing performance and different fatigue protocols result in different performance changes.

Changes in spinal height following sustained lumbar flexion and extension postures: a clinical measure of intervertebral disc hydration using stadiometry.

BACKGROUND Decreased intervertebral disc height can result in diminished load carrying capacity of the spinal segment. Clinical means of assessing postures able to rehydrate the discs were investigated. OBJECTIVE The purposes of this study were 3-fold: (1) to determine if our test protocol using a commercially available stadiometer demonstrated findings consistent with prior laboratory-based protocols; (2) to determine if hyperextension in the prone position and trunk flexion in the supine position caused increased spine height after sustained loading; and (3) to compare the effects of hyperextension in the prone position and trunk flexion in the supine position on spine height changes after a period of sustained loading. METHODS This study used a pretest, posttest crossover design. Ten women and 11 men (mean age, 24 +/- 2.6 years) participated. Subjects held either 10 minutes of hyperextension in the prone position or 10 minutes of trunk flexion in the supine position in the recovery phase. Spine height was measured using a commercially available stadiometer. Spinal height change was determined from measurements taken after loaded sitting and measurements taken after hyperextension in the prone position and trunk flexion in the supine position. RESULTS A 1-sample t test indicated no significant difference existed between our mean height change after 5 minutes of sitting and previously published validated findings. A paired t test indicated significant increase in height after both supine flexion and prone extension lying (P< .0001). The mean height gain was 3.11 mm using prone extension and 3.19 mm using the supine flexion protocol. A paired t test indicated no significant difference between these 2 recovery positions (P = .927). CONCLUSION The stadiometer measurement protocol demonstrated that hyperextension in the prone position and trunk flexion in the supine position were easily effective positions for the temporary recovery of spine height after sustained loading. These findings lay the foundation for future research into the viscoelastic creep properties of the intervertebral disk under loading and therapeutic conditions.

Change in spine height measurements following sustained mid-range and end-range flexion of the lumbar spine

Workers lose height during the day. Flexion-based exercises and body positions are commonly prescribed to unload the spine and prevent back pain. Lumbar extension positions have been researched and result in an increase in spine height. End-range lumbar extension postures increase spine height to a greater extent than mid-range lumbar extension postures, but these positions are not always tolerated by patients with lumbar conditions. No study to date has investigated the effect of end-range versus mid-range lumbar flexion postures on spine height changes. The purpose of this study was to investigate the effects of two techniques commonly used in clinical settings to unload the lumbar intervertebral disc (IVD) segments through increasing spine height in: (1) a sidelying mid-range lumbar flexion position; and (2) a sidelying end-range lumbar flexion position. A total of 20 asymptomatic women and 21 asymptomatic men with a mean age of 23.8 years (±2.5) participated in the study. Subjects were randomized systematically into 2 groups to determine the order of testing position. Measurements were taken with a stadiometer in the sitting position to detect change in spine height after each position. Results of the paired t-tests indicated that compared to the spine height in sitting, the sidelying end-range lumbar flexion position resulted in a statistically significant (p < .001) mean spine height gain of 4.78 mm (±4.01) while the sidelying mid-range lumbar flexion position resulted in a statistically significant (p < .001) mean spine height gain of 5.84 mm (±4.4). No significant difference between the height changes observed following the two sidelying positions was found (p = .22). Sidelying lumbar flexion positions offer valuable alternatives to lumbar extension positions to increase spine height, possibly through increasing hydration levels of the lumbar IVD and could be proposed as techniques to offset spinal shrinkage and the biomechanical consequences of sustained loads.