Optimising curve fitting techniques to look for standardisation of the analysis of defocus curves derived from multifocal intraocular lenses.

INTRODUCTION: To establish the most appropriate curve fitting method to allow accurate comparison of defocus curves derived from intraocular lenses (IOLs). METHODS: Defocus curves were plotted in five IOL groups (monofocal, extended depth of focus, refractive bifocal, diffractive bifocal and trifocal). Polynomial curves from 2nd to 11th order and cubic splines were fitted. Goodness of fit (GOF) was assessed using five methods: least squares, coefficient of determination (R2adj ), Akaike information criteria (AIC), visual inspection and Snedecor and Cochran. Additional defocus steps at -2.25 D and -2.75 D were measured and compared to the calculated visual acuity (VA) values. Area under the defocus curve and range of focus were also compared. RESULTS: Goodness of fit demonstrated variable results, with more lenient methods such as R2adj leading to overfitting and conservative methods such as AIC resulting in underfitting. Furthermore, conservative methods diminished the inflection points resulting in an underestimation of VA. Polynomial of at least 8th order was required for comparison of area methods, but overfitted the EDoF and monofocal groups; the spline curve was consistent for all IOLs and methods. CONCLUSIONS: This study demonstrates the inherent difficulty of selecting a single polynomial function. The R2 method can be used cautiously along with visual inspection to guard against overfitting. Spline curves are suitable for all IOLs, guarding against the issues of overfitting. Therefore, for analysis of the defocus profile of IOLs, the fitting of a spline curves is advocated and should be used wherever possible.

One-year post-operative comparison of visual function and patient satisfaction with trifocal and extended depth of focus intraocular lenses.

PURPOSE: To evaluate visual performance with trifocal and extended depth of focus IOL at 1 year post-operatively. SETTING: BMI Southend Hospital. DESIGN: Cohort study. METHODS: An age-matched cohort of forty subjects bilaterally implanted with the AT LISA 839MP trifocal IOL (20 patients, 40 eyes) and the Tecnis Symfony extended depth of focus IOL (20 patients, 40 eyes) were assessed at 3-6 months and 12-18 months post-operatively. Primary outcome measures were distance (6 m), intermediate (70 cm), near visual acuity (40 cm), and analysis of defocus profiles. Secondary outcomes included contrast sensitivity, Radner reading performance, quality of vision and assessment of halos. RESULTS: Distance visual acuity (VA) and defocus areas were similar (p = 0.07). No significant difference in intermediate VA was noted but the intermediate area of focus was greater in the EDoF (0.31 ± 0.12 LogMAR*m-1) compared to the trifocal (0.22 ± 0.08LogMAR*m-1) (p = 0.02). However, all near metrics were significantly better in the trifocal group. 80% of trifocal subjects were spectacle independent compared to 50% EDoF subjects. Quality of vision questionnaire found no significant differences between groups, however halo scores were greater at 3-6 months in the trifocal group (p < 0.01) but no differences were noted at 12-18 months. CONCLUSIONS: Near vision is significantly better for the trifocal, thus greater levels of spectacle independence. The range of intermediate vision was greater for the EDoF but no difference in intermediate VA. In the early period, differences in contrast sensitivity and halo size/intensity were noted, however, by one-year these measures were not significantly different.

Predicting the Postoperative Addition Power of a Multifocal Intraocular Lens at the Spectacle Plane.

PURPOSE: To establish a simple clinical method of predicting addition power achieved with a multifocal intraocular lens (IOL). METHODS: In this prospective cohort study, 41 patients were bilaterally implanted with the Bi-Flex MY multifocal IOL (Medicontur) with +3.50 diopters (D) near addition power. Monocular defocus curves were plotted for each patient and effective addition power was calculated as the dioptric difference between the distance and near inflection points of the defocus curve. Six biometry formulas (Haigis, Holladay, SRK/T, Hill RBF, Barrett Universal II, and Holladay 2) were used to predict the addition power at the spectacle plane. RESULTS: Mean effective addition power was 2.60 ± 0.29 D, with significant (P < .01) differences between the prediction methods. Significant differences were found between predicted and effective addition when the Holladay, SRK/T, Hill RBF, and Holladay 2 formulas were used. A moderate but significant correlation (r = 0.342, P = .033) was found with the Barrett formula, and this was also the method to show the least proportional bias with Bland-Altman analysis. CONCLUSIONS: The study demonstrates that the effective addition power can be predicted using the proposed simple clinical method derived using the Barrett Universal II formula. The proposed technique may have significant clinical value in screening for patients where ocular biometry may lead to aberrant addition power. [J Refract Surg. 2021;37(5):318-323.].

The effects of training with high-speed interval running on muscle performance are modulated by slope.

We examined changes in selected muscle performance parameters after 8 weeks of interval training using two opposite running inclinations. We hypothesized that the uphill training will affect endurance muscle performance outcomes, whereas the downhill training will affect power muscle performance outcomes. Fourteen physically active volunteers were randomly assigned into either the Uphill group (UG; n = 7; uphill interval running at +10% incline) or the Downhill group (DG; n = 7; downhill interval running at -10% incline) and completed 16 training sessions. Each session consisted of ten 30 s treadmill runs at 90% of maximum aerobic speed (MAS) with a work to rest ratio of 1:2. Vertical jump performance, isometric (MVC) and isokinetic torque of knee extensors and flexors, and fatigue of knee extensors were evaluated pre and post-training. Moreover, body composition (via bioimpedance) and vastus lateralis muscle architecture (via ultrasonography) were assessed pre and post-training. Relative lean tissue mass, relative fat mass, and squat jump (cm) significantly (p < .05) changed from baseline values by +4.5 ± 4.0%, -11.5 ± 9.6%, and +9.5 ± 11.7%, respectively, only in the DG. Similarly, DG improved absolute values of knee extension rate of torque development and impulse (p < .05), whereas knee flexion peak torque angle significantly decreased in both groups (p < .05). On the other hand, the UG increased the number of repetitions achieved during the fatigue protocol and total work by 21.2 ± 32.6% and 13.8 ± 21.2%, respectively (p < .05). No differences were found between groups in muscle architecture. Introducing variations in slope during HIIT could be used to induce specific improvements toward muscle endurance or power performance characteristics.

Difference in the running biomechanics between preschoolers and adults.

BACKGROUND: High vertical loading rate is associated with a variety of running-related musculoskeletal injuries. There is evidence supporting that non-rearfoot footstrike pattern, greater cadence, and shorter stride length may reduce the vertical loading rate. These features appear to be common among preschoolers, who seem to experience lower running injury incidence, leading to a debate whether adults should accordingly modify their running form. OBJECTIVE: This study sought to compare the running biomechanics between preschoolers and adults. METHODS: Ten preschoolers (4.2±1.6 years) and ten adults (35.1±9.5 years) were recruited and ran overground with their usual shoes at a self-selected speed. Vertical average (VALR) and vertical instantaneous loading rate (VILR) were calculated based on the kinetic data. Footstrike pattern and spatiotemporal parameters were collected using a motion capture system. RESULTS: There was no difference in normalized VALR (p=0.48), VILR (p=0.48), running speed (p=0.85), and footstrike pattern (p=0.29) between the two groups. Preschoolers demonstrated greater cadence (p<0.001) and shorter normalized stride length (p=0.01). CONCLUSION: By comparing the kinetic and kinematic parameters between children and adults, our findings do not support the notion that adults should modify their running biomechanics according to the running characteristics in preschoolers for a lower injury risk.

Effect of minimalist and maximalist shoes on impact loading and footstrike pattern in habitual rearfoot strike trail runners: An in-field study.

Running-related injuries among trail runners are very common and footwear selection may modulate the injury risk. However, most previous studies were conducted in a laboratory environment. The objective of this study was to examine the effects of two contrasting footwear designs, minimalist (MIN) and maximalist shoes (MAX), on the running biomechanics of trail runners during running on a natural trail. Eighteen habitual rearfoot strike trail runners completed level, uphill and downhill running at their preferred speeds in both shod conditions. Peak tibial acceleration, strike index and footstrike pattern were compared between the two footwear and slopes. Interactions of footwear and slope were not detected for all the selected variables. There was no significant effect from footwear (F = 1.23, p = 0.27) and slope (F = 2.49, p = 0.09) on peak tibial acceleration and there was no footwear effect on strike index (F = 3.82, p = 0.056). A significant main effect of slope on strike index (F = 13.24, p < 0.001) was found. Strike index during uphill running was significantly greater (i.e. landing with a more anterior foot strike) when compared with level (p < 0.001, Cohen's d = 1.72) or downhill running (p < 0.001, Cohen's d = 1.44) in either MIN or MAX. The majority of habitual rearfoot strike runners switched to midfoot strike during uphill running while maintaining a rearfoot strike pattern during level or downhill running. In summary, wearing either one of the two contrasting footwear (MIN or MAX) demonstrated no effect on impact loading and footstrike pattern in habitual rearfoot strike trail runners running on a natural trail with different slopes.

Visual function and subjective perception of vision after bilateral implantation of monofocal and multifocal IOLs: a randomized controlled trial.

PURPOSE: To examine monocular and binocular visual function and patient-reported outcomes after implantation of multifocal IOLs (mIOLs) or monofocal IOLs, using a rigorous series of clinical assessments. SETTING: BMI Southend Hospital, United Kingdom. DESIGN: Prospective, randomized, double-masked clinical trial. METHODS: One hundred patients were randomized for bilateral implantation of either a Bi-Flex 677MY mIOL or a Bi-Flex 677AB IOL and were assessed at 3 to 6 months (V1) and 12 to 18 months (V2). Primary outcomes included distance, intermediate, and near logarithm of the minimum angle of resolution (logMAR) visual acuities (VAs) and defocus curve profile assessment. Secondary outcomes included reading speed, contrast sensitivity (CS), and the subjective perception of quality of vision. RESULTS: Forty-seven subjects with monofocal IOL and 43 mIOL subjects completed the study. Uncorrected (mIOL: 0.10 ± 0.09 logMAR; IOL: 0.09 ± 0.11 logMAR) and corrected (mIOL: 0.04 ± 0.06 logMAR; IOL: 0.01 ± 0.07 logMAR) distance VAs were comparable (P > .05). Uncorrected near VA (mIOL: 0.23 ± 0.13 logMAR; IOL: 0.55 ± 0.20 logMAR, P < .001) and distance-corrected near VA (mIOL: 0.24 ± 0.13 logMAR; IOL: 0.54 ± 0.17 logMAR, P < .001) were significantly improved with mIOLs. There was no significant difference in distance-corrected intermediate VA (mIOL: 0.38 ± 0.13 logMAR; IOL: 0.39 ± 0.13 logMAR, P = .431). Defocus curves demonstrated an increased range-of-focus among mIOLs (mIOL: 4.14 ± 1.10 diopter [D]; IOL: 2.57 ± 0.77 D). Pelli-Robson CS was different at V1 (P < .001) but similar by V2 (P = .059). Overall satisfaction was high (>90%) in both groups for distance tasks whereas significantly different for near tasks (mIOL, 18.45 ± 16.53 logUnits; IOL, 55.59 ± 22.52 logUnits). CONCLUSIONS: Uncorrected near visual acuity was demonstrably better with mIOLs and there was greater subjective satisfaction with quality of near vision. Halos reported by the mIOL group were significant compared with the IOL group but did not show an adverse effect on overall satisfaction.

Bilateral asymmetry of running gait in competitive, recreational and novice runners at different speeds.

The mechanisms and underlying causes of bilateral asymmetry among healthy runners of different levels remain unclear. This cross-sectional laboratory study aimed to investigate the effects of running speed and running experience or competitive level on bilateral symmetry during running. Eleven competitive runners, 9 recreational runners and 11 novice runners were recruited in this study. They ran on an instrumented treadmill for 3 min at each of 5 fixed speeds (8, 9, 10, 11 and 12 km/h) in a randomized order. Bilateral asymmetry was evaluated and quantified using symmetry index (SI) of temporal and kinetic parameters. Overall, SI ranged between 0.8% for stride time and 21.4% for vertical average loading rate. Significant speed effects were observed on SI of flight time (p = .012), which was significantly higher at 8 km/h than that of the other 4 speeds (p = .023, 0.005, 0.023 and 0.028, respectively). Group-by-speed interactions were detected on SI in time to peak vertical ground reaction force (p = .032) and vertical average loading rate (p = .002). The competitive runners presented linear reduction in the SI with increasing speed from 8 to 12 km/h (R2 > 0.94); for the recreational runners, SI changed nonlinearly and presented a roughly U-shaped trend across speeds (R2 > 0.88); and for the novice runners, changes of SI across speed were inconsistent and dependent on parameters of interest (R2 > 0.64). Bilateral asymmetry was affected by both running speed and runners' running experience or competitive level. The competitive runners were found to run with a more symmetrical manner with a greater running speed, the recreational runners demonstrated the most symmetrical pattern at the critical speed, whereas the novice runners showed inconsistent trends.

The effects of midfoot strike gait retraining on impact loading and joint stiffness.

OBJECTIVE: To assess the biomechanical changes following a systematic gait retraining to modify footstrike patterns from rearfoot strike (RFS) to midfoot strike (MFS). DESIGN: Pre-post interventional study. All participants underwent a gait retraining program designed to modify footstrike pattern to MFS. SETTING: Research laboratory. PARTICIPANTS: Twenty habitual RFS male runners participated. MAIN OUTCOME MEASURES: Gait evaluations were conducted before and after the training. Footstrike pattern, vertical loading rates, ankle and knee joint stiffness were compared. RESULTS: Participants' footstrike angle was reduced (p < 0.001, Cohen's d = 1.65) and knee joint stiffness was increased (p = 0.003, Cohen's d = 0.69). No significant difference was found in the vertical loading rates (p > 0.155). Further subgroup analyses were conducted on the respondents (n = 8, 40% of participants) who exhibited MFS for over 80% of their footfalls during the post-training evaluation. Apart from the increased knee joint stiffness (p = 0.005, Cohen's d = 1.14), respondents exhibited a significant reduction in the ankle joint stiffness (p = 0.019, Cohen's d = 1.17) when running with MFS. CONCLUSIONS: Gait retraining to promote MFS was effective in reducing runners' footstrike angle, but only 40% of participants responded to this training program. The inconsistent training effect on impact loading suggests a need to develop new training protocols in an effort to prevent running injuries.

Impact Loading During Distracted Running Before and After Auditory Gait Retraining.

Visual feedback gait retraining has been reported to successfully reduce impact loading in runners, even when the runners were distracted. However, auditory feedback is more feasible in real life application. Hence, this study compared the peak positive acceleration (PPA), vertical average (VALR) and instantaneous (VILR) loading rate during distracted running before and after a course of auditory feedback gait retraining in 16 runners. The runners were asked to land with softer footfalls with and without auditory feedback. Low or high sound pitch was generated according to the impact of particular footfall, when compared with the preset target. Runners then received a course of auditory gait retraining, and after the gait retraining, runners completed a reassessment. Runners before gait retraining exhibited lower PPA, VALR and VILR with augmented auditory feedback (p<0.049). We found a reduction in PPA, VALR and VILR after gait retraining, regardless of the presence of feedback (p<0.018). However, runners after gait retraining did not demonstrate further reduction in PPA and VALR with auditory feedback (p>0.104). A small effect of auditory feedback on VILR in runners after gait retraining was observed (p=0.032). Real time auditory feedback gait retraining is effective in impact loading reduction, even when the runners were distracted.

Gait Retraining for the Reduction of Injury Occurrence in Novice Distance Runners: 1-Year Follow-up of a Randomized Controlled Trial.

BACKGROUND: The increasing popularity of distance running has been accompanied by an increase in running-related injuries, such that up to 85% of novice runners incur an injury in a given year. Previous studies have used a gait retraining program to successfully lower impact loading, which has been associated with many running ailments. However, softer footfalls may not necessarily prevent running injury. PURPOSE: To examine vertical loading rates before and after a gait retraining program and assess the effectiveness of the program in reducing the occurrence of running-related injury across a 12-month observation period. STUDY DESIGN: Randomized controlled trial; Level of evidence, 1. METHODS: A total of 320 novice runners from the local running club completed this study. All the participants underwent a baseline running biomechanics evaluation on an instrumented treadmill with their usual running shoes at 8 and 12 km/h. Participants were then randomly assigned to either the gait retraining group or the control group. In the gait retraining group (n = 166), participants received 2 weeks of gait retraining with real-time visual feedback. In the control group (n = 154), participants received treadmill running exercise but without visual feedback on their performance. The training time was identical between the 2 groups. Participants' running mechanics were reassessed after the training, and their 12-month posttraining injury profiles were tracked by use of an online surveillance platform. RESULTS: A significant reduction was found in the vertical loading rates at both testing speeds in the gait retraining group ( P < .001, Cohen's d > 0.99), whereas the loading rates were either similar or slightly increased in the control group after training ( P = .001 to 0.461, Cohen's d = 0.03 to -0.14). At 12-month follow-up, the occurrence of running-related musculoskeletal injury was 16% and 38% in the gait retraining and control groups, respectively. The hazard ratio between gait retraining and control groups was 0.38 (95% CI, 0.25-0.59), indicating a 62% lower injury risk in gait-retrained runners compared with controls. CONCLUSION: A 2-week gait retraining program is effective in lowering impact loading in novice runners. More important, the occurrence of injury is 62% lower after 2 weeks of running gait modification. Registration: HKUCTR-1996 (University of Hong Kong Clinical Trials Registry).

Test-Retest Reliability of Measuring the Vertebral Arterial Blood Flow Velocity in People With Cervicogenic Dizziness.

OBJECTIVES: The purpose of this study was to determine the within-session and between-sessions reliability of measuring the vertebral artery blood flow velocities in people with cervicogenic dizziness using Doppler ultrasound at both upper and lower cervical levels. METHODS: Outcome measures were taken on 2 occasions 3 weeks apart with no active treatment provided in between the assessments on 12 participants. Pulsed-wave Doppler ultrasound was used to quantify time-averaged mean velocities through the vertebral artery at upper cervical (C0-1) and lower cervical vertebrae (C5-6). The clinical outcome measures were also recorded in people with cervicogenic dizziness. The intraclass correlation coefficient (ICC) was used to determine the within-session and between-session repeatability. Paired t test was used to determine the differences in the time-averaged mean velocities of blood flow at the same site of the vertebral artery and the clinical outcome measures in 2 sessions 3 weeks apart. RESULTS: In people with cervicogenic dizziness, there was no significant change in both clinical outcome measures and the time-averaged mean velocities when the patients were measured 3 weeks apart (P > .05). This study identified good within-session (ICC: 0.903-0.967) and between-session (ICC: 0.922-0.984) repeatability in measuring the vertical blood flow velocities in patients with cervicogenic dizziness when the clinical outcome measures were unchanged. CONCLUSIONS: This study supports the use of Doppler ultrasound to identify changes in mean vertebral arterial blood flow velocities before and after intervention in people with cervicogenic dizziness in future studies.

The effect of elastic therapeutic taping on lumbar extensor isokinetic performance.

OBJECTIVES: To investigate the effects of elastic therapeutic tape when applied overlaying the lumbar extensors on different measures of muscle performance, compared to a placebo taping technique and a no-tape control. DESIGN: A cross-sectional experimental study. SETTING: A biomechanics laboratory. PARTICIPANTS: Twenty one participants received three taping conditions in a randomised order: elastic therapeutic tape, a placebo tape and a no-tape control. Peak torque, the time taken to reach peak torque and peak velocity were measured using an isokinetic dynamometer. MAIN OUTCOME MEASURES: Concentric lumbar extension peak torque at 60°/s, time taken to reach peak torque and peak velocity was measured using an isokinetic dynamometer. Friedman's test and post-hoc Wilcoxon signed-rank test were used to determine the statistical differences between the three taping conditions. Level of signicance was set at 0.05.fi. RESULTS: A statistically significant improvement in peak lumbar extensor torque was observed when comparing elastic therapeutic tape with the no-tape control (p < 0.05). However, there was no significant differences in time taken to reach peak torque and peak velocity (p > 0.05). CONCLUSIONS: Results demonstrate that the application of elastic therapeutic tape overlaying the primary lumbar extensors significantly improves the maximal lumbar extension peak torque in healthy, asymptomatic adults.

Humeral elevation reduces the dynamic control ratio of the shoulder muscles during internal rotation.

OBJECTIVES: To determine the differences in the dynamic control ratio of the glenohumeral joint rotators, during internal rotation at 20° and 60° of humeral elevation in the scapular plan. Dynamic control ratio (DCR) is defined as the ratio between eccentric action of the lateral rotators and the concentric action of the medial rotators. DESIGN: A cross-sectional laboratory study. METHODS: Thirty asymptomatic participants (men n=14, women n=16, mean age=29.4±8.9years, BMI: 24.1±5.4) were tested. Peak torque generated by the concentric action of the MR and the eccentric action of the LR of the shoulder joint and the DCR were evaluated on the dominant arm using an isokinetic dynamometer at 20° and 60° of humeral elevation at a speed of 20°/s. RESULTS: There was a significant decrease in the DCR at 60° humeral elevation when compared to 20° humeral elevation (p<0.05). This decrease was due to the significant decrease in eccentric peak torques at 60° humeral elevation when compared to 20° (p<0.05). However, there was no significant difference in the concentric peak torques between 20° and 60° (p>0.05). CONCLUSIONS: The significant decrease in the DCR as a consequence of a decrease in the eccentric peak torque of the LR when the humerus is in a more elevated position suggests that the introduction of humeral elevation can be used as a progression for improving the eccentric action of the shoulder LR and subsequently the dynamic control of the shoulder.

Comparison of reliability and repeatability of corneal curvature assessment with six keratometers.

BACKGROUND: Keratometric methodology varies between instruments and the differences may have a clinical impact. We investigated the agreement and reproducibility of six keratometers. METHODS: Keratometry was performed on 100 subjects at two separate sessions with IOLMaster 500, Pentacam, OPD scanner, Medmont E300, Javal-Schiøtz and TMS-5. A second observer assessed 30 subjects to determine inter-observer variability. A single individual was assessed on 10 separate sessions to determine intra-observer variability. Data were analysed using coefficient of variation (CV) and intra-class correlation coefficient (ICCC) for intra-observer variation. Inter-observer concordance was evaluated by the ICCC. Bland-Altman plots, Pearson's correlation coefficient and repeated measures analysis of variance were used to assess agreement of data produced by the instruments. RESULTS: OPD scanner and Javal-Schiøtz mean spherical equivalent (MSE) results were systematically different (p < 0.001) from other instruments (flatter and steeper, respectively). J0 /J45 were similar for all instruments (p < 0.05). Bland-Altman comparison plots indicated that Pentacam and IOLMaster demonstrated greatest level of agreement (ICC results MSE = 0.992, J0 = 0.934 and J45 = 0.890). Agreement (ICC) between observers for MSE ranged from 0.955 to 0.995 for all instruments; lower levels of agreement were found for J0 /J45 (0.289 to 0.901). IOLMaster showed greatest correlation and Medmont the lowest. All instruments showed high intra-observer repeatability of MSE (CV 0.1 to 0.3 per cent). The J0 /J45 readings showed greater variability (CV range 8.8 to 57.6 per cent). CONCLUSION: When considering MSE alone IOLMaster, Pentacam, OPD scan and Medmont may be considered interchangeable; however, assessment of astigmatism shows greater variability between instruments, sessions and observers.

Tibial nerve excursion during lumbar spine and hip flexion measured with diagnostic ultrasound.

Ultrasound imaging provides a method for non-invasive in vivo measurement of nerve motion resulting from joint movement. This study measured the proximal excursion of the tibial branch of the sciatic nerve at the popliteal fossa during forward bending in healthy subjects. Long-axis image sequences of the nerve were analysed using frame-by-frame cross-correlation software that calculated the longitudinal and axial movement of the nerve. Proximal excursion was calculated from the hypotenuse of these values. The mean proximal excursion recorded was 12.2 mm (SD 2.2 mm, n = 24). The reliability of three repeat measurements was found to be excellent (ICC 0.97, 95% CI 0.93-0.99; SEM 0.7 mm, n = 21). The protocol described provides a reliable method for analysing tibial nerve movement that could prove useful in future clinical studies.

The immediate effect of posteroanterior mobilization on reducing back pain and the stiffness of the lumbar spine.

OBJECTIVE: To study the immediate effect of posteroanterior mobilization on back pain and the associated biomechanical changes in the lumbar spine. DESIGN: An experimental between-group study. SETTING: A biomechanics laboratory. PARTICIPANTS: Subjects with low back pain (n=19) and healthy subjects (n=20). INTERVENTIONS: Grade III posteroanterior mobilization (3 cycles of 60s) was applied at the L4 level in people with or without back pain on 1 occasion. MAIN OUTCOME MEASURES: Pain intensity, active lumbar range of motion, the magnitude of the posteroanterior mobilization loads, bending stiffness of the lumbar spine, and the lordotic curvature of the lumbar spine before and after 3 cycles of posteroanterior mobilization. RESULTS: The magnitude of pain of the patients was found to decrease significantly after posteroanterior mobilization treatment. There was also a significant decrease in the bending stiffness of the lumbar spine of the patients, which was derived from the posteroanterior load and the associated change in spine curvature. The stiffness was restored to a level that was similar to that of the asymptomatic subjects. A strong correlation was found between the magnitude of pain and the bending stiffness of the spine before (r=.89) and after posteroanterior mobilization (r=.98). CONCLUSIONS: Posteroanterior mobilization was found to bring about immediate desirable effects in reducing spinal stiffness and the magnitude of back pain. The restoration of the mechanical properties of the spine may be a possible mechanism that explains the improvement in pain after manual therapy.

Efficacy of static stretching and proprioceptive neuromuscular facilitation stretch on hamstrings length after a single session.

A number of studies have investigated the efficacy of several repetitions of proprioceptive neuromuscular facilitation stretching (PNF) and static stretching (SS). However, there is limited research comparing the effects of a single bout of these stretching maneuvers. The aim of this study was to compare the effectiveness of a single bout of a therapist-applied 30-second SS vs. a single bout of therapist-applied 6-second hamstring (agonist) contract PNF. Forty-five healthy subjects between the ages of 21 and 35 were randomly allocated to 1 of the 2 stretching groups or a control group, in which no stretching was received. The flexibility of the hamstring was determined by a range of passive knee extension, measured using a universal goniometer, with the subject in the supine position and the hip at 90° flexion, before and after intervention. A significant increase in knee extension was found for both intervention groups after a single stretch (SS group = 7.53°, p < 0.01 and PNF group = 11.80°, p < 0.01). Both interventions resulted in a significantly greater increase in knee extension when compared to the control group (p < 0.01). The PNF group demonstrated significantly greater gains in knee extension compared to the SS group (mean difference 4.27°, p < 0.01). It can be concluded that a therapist applied SS or PNF results in a significant increase in hamstring flexibility. A hamstring (agonist) contract PNF is more effective than an SS in a single stretching session. These findings are important to physiotherapists or trainers working in clinical and sporting environments. Where in the past therapists may have spent time conducting multiple repetitions of a PNF and an SS, a single bout of either technique may be considered just as effective. A key component of the study methodology was the exclusion of a warm-up period before stretching. Therefore, the findings of efficacy of a single PNF are of particular relevance in sporting environments and busy clinical settings where time may be limited.

Back pain is associated with changes in loading pattern throughout forward and backward bending.

STUDY DESIGN: Experimental study to determine the kinetics of the lumbar spine (LS) and hips during forward and backward bending. OBJECTIVE: To investigate the effects of back pain, with and without a positive straight leg raise (SLR) sign, on the loading patterns in the LS and hip during forward and backward bending. SUMMARY OF BACKGROUND DATA: Forward and backward bending are important components of many functional activities and are part of routine clinical examination. However, there is a little information about the loading patterns during forward and backward bending in people with back pain with or without a positive SLR sign. METHODS: Twenty asymptomatic participants, 20 back pain participants, and 20 participants with back pain and a positive SLR sign performed 3 continuous cycles of forward and backward bending. Electromagnetic sensors were attached to body segments to measure their kinematics while 2 nonconductive force plates gathered ground reaction force data. A biomechanical model was used to determine the loading pattern in LS and hips. RESULTS: Although the loading on the LS at the end of the range decreased significantly, the loading at the early and middle ranges of forward bending actually increased significantly in people with back pain, especially in those with positive SLR sign. This suggests that resistance to movement is significantly increased in people with back pain during this movement. CONCLUSION: This study suggested that it is not sufficient to study the spine at the end of range only, but a complete description of the loading patterns throughout the range is required. Although the maximum range of motion of the spine is reduced in people with back pain, there is a significant increase in the moment acting through the range, particularly in those with a positive SLR sign.

The effect of closed-kinetic chain exercises and open-kinetic chain exercise on the muscle activity of vastus medialis oblique and vastus lateralis.

Patellofemoral pain syndrome (PFPS) is one of the most prevalent musculoskeletal conditions of the lower limb. The muscle imbalance between the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles is one of the main factors leading to the development of PFPS. The disparity in research and the necessity to add to the existing literature base led to the development of this study. The aim of this study was to investigate the effect of 2 closed kinetic chain exercises and 1 open kinetic chain exercise on VMO and VL muscle activity. Twenty-two healthy asymptomatic individuals participated in this study. The surface electromyography (EMG) of VMO and VL was measured and used to calculate the VMO:VL ratio during 3 different quadriceps-strengthening exercises (a double leg squat with isometric hip adduction exercise, an open kinetic chain knee extension exercise, and a lunge exercise). The double leg squat with isometric hip adduction exercise was shown to produce a significantly greater VMO:VL ratio (1.14:1) than the other 2 exercises (p = 0.015 and p = 0.005). The open kinetic chain knee extension exercises produced significantly greater activation of VL than the lunge exercise (p = 0.001 and p = 0.036). The lunge exercise produced the VMO:VL ratio (1.18:1) closest to the idealized ratio of 1:1. Potential clinical recommendations can be made proposing the lunge exercise as a key tool in early rehabilitation when restoring preferential VMO:VL ratio is essential. The double leg squat with isometric hip adduction exercise would be useful in maintaining correct patella tracking and selectively strengthening VMO.