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Context Sixty thousand people are diagnosed with Parkinson’s disease (PD) each year, making it the second most common neurodegenerative disorder. PD results in a variety of gait disturbances, including muscular rigidity and decreased range of motion (ROM), that increase the fall risk of those afflicted. Osteopathic manipulative treatment (OMT) emphasizes the central role of the musculoskeletal system, which could be ideal for addressing the somatic dysfunction associated with neurodegeneration in PD. The close anatomical relationship of structures implicated in PD within the skull and the increased frequency of strain patterns raise the question of whether osteopathic cranial manipulative medicine (OCMM) can improve gait performance by improving circulation to the affected nervous tissue. However, there have been few studies in recent years that explore the effects of a standardized OMT protocol on Parkinsonian gait characteristics, and there have been few studies that include OCMM techniques. Objectives This study aims to determine whether a single session of OMT or OMT + OCMM can improve the gait of individuals with PD by addressing joint restrictions in the sagittal plane and by increasing ROM in the lower limb. Methods The following study is a two-group, randomized controlled trial in which individuals with PD (n=45) and age-matched healthy control participants (n=45) were recruited from the community. PD participants were included if they were otherwise healthy, able to stand and walk independently, had not received OMT or physical therapy (PT) within 30 days of data collection, and had idiopathic PD in Hoehn and Yahr stages 1.0–3.0. PD participants were randomly assigned to one of three experimental treatment protocols: a ‘whole-body’ OMT protocol (OMT-WB), which included OMT and OCMM techniques; a ‘neck-down’ OMT protocol (OMT-ND), including only OMT techniques; and a sham treatment protocol. Control participants were age-matched to a PD participant and were provided the same OMT experimental protocol. An 18-camera motion analysis system was utilized to capture 3-dimensional (3D) position data in a treadmill walking trial before and after the assigned treatment protocol. Pretreatment and posttreatment hip, knee, and ankle ROM were compared with paired t-tests, and joint angle waveforms during the gait cycle were analyzed with statistical parametric mapping (SPM), which is a type of waveform analysis. Results Individuals with PD had significantly reduced hip and knee extension in the stance phase compared to controls (32.9–71.2% and 32.4–56.0% of the gait cycle, respectively). Individuals with PD experienced a significant increase in total sagittal hip ROM (p=0.038) following a single session of the standardized OMT-WB treatment protocol. However, waveform analysis found no significant differences in sagittal hip, knee, or ankle angles at individual points of the gait cycle following OMT-WB, OMT-ND, or sham treatment protocols. Conclusions The increase in hip ROM observed following a single session of OMT-WB suggests that OCMM in conjunction with OMT may be useful for improving gait kinematics in individuals with PD. Longitudinal studies over multiple visits are needed to determine the long-term effect of regular OMT and OMT+OCMM treatments on Parkinsonian gait characteristics.

Background Individuals with unilateral transtibial amputations (ITTAs) are asymmetrical in quadriceps strength. It is unknown if this is associated with gait performance characteristics such as walking speed and limb symmetry. Research question Are quadriceps strength asymmetries related to walking speed and/ or gait asymmetries in ITTAs? Methods Knee-extensor isometric maximum voluntary torque (MVT) and rate of torque development (RTD) were measured in eight ITTAs. Gait data were captured as the ITTAs walked at self-selected habitual and fast speeds. Step length and single support time, peak knee extension moments and their impulse and peak vertical ground reaction force (vGRF) in the braking and propulsive phases of stance were extracted. Bilateral Asymmetry Index (BAI) and, for gait variables only, difference in BAI between walking speeds (ΔBAI) were calculated. Correlation analyses assessed the relationships between MVT and RTD asymmetry and (1) walking speed; (2) gait asymmetries. Results Associations between strength and gait BAIs generally became more apparent at faster walking speeds, and when the difference in BAI between fast and habitual walking speed was considered. BAI RTD was strongly negatively correlated with habitual and fast walking speeds (r=∼0.83). Larger BAI RTD was strongly correlated with propulsive vGRF BAI in fast walking, and larger ΔBAIs in vGRF during both the braking and propulsion phases of gait (r = 0.74–0.92). ITTAs who exhibited greater BAI MVT showed greater ΔBAI in single support time (r = 0.83). Significance While MVT and RTD BAI appear to be associated with gait asymmetries in ITTAs, the magnitude of the asymmetry in RTD appears to be a more sensitive marker of walking speed. Based on these results, it’s possible that strengthening the knee-extensors of the amputated limb to improve both MVT and RTD symmetry may benefit walking speed, and reduce asymmetrical loading in gait.

Individuals with a unilateral transtibial amputation (ITTA) often experience greater loading on the intact limb during running and stepping tasks compared to individuals without amputation. This study aimed to investigate the mechanics of load absorption in the intact limb of ITTA and determine if increased ground reaction forces (GRF) persist during a start-stop task which (i) controlled touch-down velocity and (ii) removed the requirement for on-going locomotion. Data were collected using a twelve-camera motion capture system with two Kistler force platforms. Variables were extracted during the final loading phase of a 2-step start-stop task. The intact limb of ITTA and the dominant limb of able-bodied controls were compared using independent t-tests and effect size analysis. ITTA showed lower knee flexion angles at touchdown (p = 0.007, g = -1.43), and peak vertical GRF (p = 0.01, g = -1.33) compared to control subjects. ITTA also exhibited less hip (p = 0.14, g = 0.76) and ankle (p = 0.002, g = 1.82) absorptive power at touchdown and at peak vertical GRF (hip: p = 0.01, g = 1.23; ankle: p = 0.05, g = 0.97). ITTA exhibited greater peak vertical GRF (p = 0.01, g = 1.30) and braking GRF (p = 0.05, g = -0.96) on the intact limb compared to the controls. Our results indicate altered joint mechanics through the intact limb of ITTA are independent of the touchdown conditions or the need for ongoing locomotion. These altered joint mechanics increased loading experienced by the intact limb. Further work should be conducted examining a variety of other dynamic movements to fully understand the involved mechanics, so that intervention studies can be developed to reduce the load experienced by ITTA.

Decreased mechanical work done by the trailing limb when descending a single-step could affect load development and increase injury risk on the leading limb. This study assessed the effect of trailing limb mechanics on the development of lead limb load during a step descent by examining individuals with unilateral transtibial amputations who are known to exhibit reduced work in the prosthetic limb.Eight amputees and 10 able-bodied controls walked 5 m along the length of a raised platform, descended a single-step of 14 cm height, and continued walking. The intact limb of amputees led during descent. Kinematic and kinetic data were recorded using integrated motion capture and force platform system. Lead limb loading was assessed through vertical ground reaction force, and knee moments and joint reaction forces. Sagittal-plane joint work was calculated for the ankle, knee, and hip in both limbs.No differences were found in lead limb loading despite differences in trail limb mechanics evidenced by amputees performing 58% less total work by the trailing (prosthetic) limb to lower the centre of mass (P = 0.004) and 111% less for propulsion (P 0.001). Amputees descended the step significantly slower (P = 0.003) and performed significantly greater lead limb ankle work (P = 0.017). After accounting for speed differences, initial loading at the knee was significantly higher in the lead limb of amputees versus controls.Increasing lead limb work and reducing forward velocity may be effective compensatory strategies to limit lead limb loading during a step descent, in response to reduced trailing limb work.

New findings What is the central question of this study? The effects of long-term muscle disuse on neuromuscular function are unclear because disuse studies are typically short term. In this study, we used a new model (unilateral transtibial amputees) to investigate the effects of long-term disuse on quadriceps neuromuscular function. What is the main finding and its importance? Kinetic analysis (knee-extension moments during gait) indicated habitual disuse of the amputated limb quadriceps, accompanied by lower quadriceps muscle strength (60-76%) and neural activation (32-44%), slower contractile properties and altered muscle architecture in the amputated limb, which could not be predicted from short-term disuse studies. Abstract The purpose of this study was to determine: (i) whether individuals with unilateral transtibial amputations (ITTAs), who habitually disuse the quadriceps muscles of their amputated limb, provide an effective model for assessing the effects of long-term muscle disuse; and (ii) the effects of such disuse on quadriceps muscle strength and neuromuscular function in this population. Nine ITTAs and nine control subjects performed isometric voluntary knee extensions of both limbs to assess maximal voluntary torque (MVT) and the rate of torque development (RTD). The interpolated twitch technique and EMG normalized to maximal M-wave were used to assess neural activation, involuntary (twitch and octet) contractions to assess intrinsic contractile properties, and ultrasound images of the vastus lateralis to assess muscle architecture. Clinical gait analysis was used to measure knee kinetic data during walking at an habitual speed. The ITTAs displayed 54-60% lower peak knee-extensor moments during walking in the amputated compared with intact/control limbs, but the intact and control limbs were comparable for loading during walking and muscle strength variables, suggesting that the intact limb provides a suitable internal control for comparison with the disused amputated limb. The MVT and RTD were ∼60 and ∼75% lower, respectively, in the amputated than intact/control limbs. The differences in MVT appeared to be associated with ∼40 and ∼43% lower muscle thickness and neural activation, respectively, and the differences in RTD appeared to be associated with the decline in MVT coupled with slowing of the intrinsic contractile properties. These results indicate considerable changes in strength and neuromuscular function with long-term disuse that could not be predicted from short-term disuse studies.

Background When stepping down from a raised surface, either a toe or heel contact strategy is performed. Increased vertical momentum is likely to be experienced during a step descent, yet the extent to which these descent strategies influence the development of load at the ground and knee has not been examined. Research Question Does descent strategy influence ground and knee joint loading? Does the contribution from leading and trailing limb joint mechanics differ between descent strategies? Methods Twenty-two healthy male participants (age: 34.0 ± 6.5 years, height: 179 ± 6.3 cm, mass: 83.5 ± 13 kg) walked along a raised platform, stepped down from a 14 cm height utilising either a toe (n = 10) or heel (n = 12) initial contact, and continued walking. Vertical ground reaction forces and knee external adduction and flexor moments were extracted for the duration of the braking phase. Joint work was calculated for the ankle, knee, and hip in both the leading and trailing limbs. Results Waveform analysis of the loading features indicated that a toe-contact strategy resulted in significantly reduced loading rates during early braking (1–32% of the braking phase) and significantly increased magnitude in late braking (55–96% of the braking phase). Individuals performing toe landings completed 33% greater overall work (p = 0.091) in the lead limb and utilised the lead limb ankle joint as the main shock absorber (79% of total lead limb work). Concurrently, the trailing limb performed 29% and 21% less work when lowering the centre of mass and propulsion, respectively, compared to a heel landing. Significance A toe-contact strategy results in reduced limb and knee joint loading rates through greater utilisation of the lead limb ankle joint. A heel-contact strategy, however, can reduce loading during late braking by utilising the functionality of the trailing limb.

Understanding the mechanisms of instability can aid in reducing fall risk. As a sensitive measure of fall risk, the distance between the center of pressure (COP) and center of mass (COM) is currently assessed through discrete points assumed to represent physiological important fall mechanisms. However, it is unclear if these discrete points are appropriate measures of fall risk. Statistical parametric mapping (SPM) is a waveform analysis technique that removes this possibly biased a priori approach. Sixteen healthy young adults (8 males, 8 females; Age: 29 ± 3.6 years, Height: 1.7 ± 0.9 m, Mass: 75 ± 16 kg) performed two tasks that disturbed dynamic stability: voluntary stepping at different step lengths, and forward perturbations at different accelerations. COP-COM distance magnitudes were extracted during the first step in both tasks at discrete points typically assessed in previous research. Discrete point analysis (DPA) was performed on these discrete points and SPM analysis was completed on the COP-COM distance waveform. The results from the study found that SPM analysis identified equivalent significant differences to DPA and identified additional significant differences elsewhere in the COP-COM distance waveform that were not able to be detected by DPA. Two key advantages from using SPM: (1) reduction of possibly biased a priori selection, and (2) increased efficiency and reduced time-cost in data post-processing as inherent variability can limit the detection of discrete points resulting in identifying physiologically different discrete points across trials. This study suggests the use of SPM as a sensitive data analysis approach in detecting fall risk as an alternative to DPA.

Evidence suggests dietary nitrate supplementation enhances low-frequency (≤20 Hz) involuntary, but not voluntary, forces in unfatigued human muscle. We investigated the hypotheses that nitrate supplementation would also attenuate low-frequency fatigue and the loss of explosive voluntary forces in fatigued conditions.In a counterbalanced double-blinded order, 17 male participants completed two experimental trials after 7 d of dietary supplementation with either nitrate-rich (NIT) or nitrate-depleted (PLA) beetroot juice. Each trial consisted of measuring isometric knee extension forces during a series of explosive maximal voluntary contractions (MVC) and involuntary tetanic contractions (at 10, 20 50, and 100 Hz) in unfatigued conditions, followed by a fatigue protocol of 60 MVC and a repeat of the tetanic contractions immediately after the 60 MVC.In unfatigued conditions, there was no effect of NIT on any of the measured dependent variables, including maximal voluntary force, explosive impulse, and tetanic peak forces or peak rate of force developments at any frequency. In contrast, the percentage decline in explosive voluntary impulse from the first to the last 6 MVC in the fatigue protocol was lower in NIT (51.1% ± 13.9%) than in PLA (57.3% ± 12.4%; P = 0.039; d = 0.51). Furthermore, low-frequency fatigue determined via the percentage decline in the 20/50-Hz ratio was attenuated in NIT for tetanic peak force (NIT: 12.3% ± 12.0% vs PLA: 17.0% ± 10.1%; P = 0.110; d = 0.46) and tetanic peak rate force development (NIT: 12.3% ± 10.4% vs PLA: 20.3% ± 9.5%; P = 0.011; d = 0.83).Nitrate supplementation reduced the decline in explosive voluntary forces during a fatiguing protocol and attenuated low-frequency fatigue, likely due to reduced disruption of excitation-contraction coupling. However, contrary to previous findings, nitrate supplementation had no effect on contractile performance in unfatigued conditions.

The purpose of this study was to investigate the benefit of landmark registration when applied to waveform data. We compared the ability of data reduced from time-normalised and landmark registered vertical ground reaction force (vGRF) waveforms captured during maximal countermovement jumps (CMJ) of 53 active male subjects to predict jump height. vGRF waveforms were landmark registered using different landmarks resulting in four registration conditions: (i) end of the eccentric phase, (ii) adding maximum centre of mass (CoM) power, (iii) adding minimum CoM power, (iv) adding minimum vGRF. In addition to the four registration conditions, the non-registered vGRF and concentric phase only were time-normalised and used in subsequent analysis. Analysis of characterising phases was performed to reduce the vGRF data to features that captured the behaviour of each waveform. These features were extracted from each condition’s vGRF waveform, time-domain (time taken to complete the movement), and warping functions (generated from landmark registration). The identified features were used as predictor features to fit a step-wise multilinear regression to jump height. Features generated from the best performing registration condition were able to predict jump height to a similar extent as the concentric phase (86–87%), while all registration conditions could explain jump height to a greater extent than time-normalisation alone (65%). This suggests waveform variability was reduced as phases of the CMJ were aligned. However, findings suggest that over-registration can occur when applying landmark registration. Overall, landmark registration can improve prediction power to performance measures as waveform data can be reduced to more appropriate performance related features.