Stable Coordination Variability in Overground Walking and Running at Preferred and Fixed Speeds.

Coordination variability (CV) is commonly analyzed to understand dynamical qualities of human locomotion. The purpose of this study was to develop guidelines for the number of trials required to inform the calculation of a stable mean lower limb CV during overground locomotion. Three-dimensional lower limb kinematics were captured for 10 recreational runners performing 20 trials each of preferred and fixed speed walking and running. Stance phase CV was calculated for 9 segment and joint couplings using a modified vector coding technique. The number of trials required to achieve a CV mean within 10% of 20 strides average was determined for each coupling and individual. The statistical outputs of mode (walking vs running) and speed (preferred vs fixed) were compared when informed by differing numbers of trials. A minimum of 11 trials were required for stable mean stance phase CV. With fewer than 11 trials, CV was underestimated and led to an oversight of significant differences between mode and speed. Future overground locomotion CV research in healthy populations using a vector coding approach should use 11 trials as a standard minimum. Researchers should be aware of the notable consequences of an insufficient number of trials for overall study findings.

Comparisons of Segment Coordination: An Investigation of Vector Coding.

The development of a methodology to assess movement coordination has provided gait researchers a tool to assess movement organization. A challenge in analyzing movement coordination using vector coding lies within the inherent circularity of data garnered from this technique. Therefore, the purpose of this investigation was to determine if accurate group comparisons can be made with varying techniques of vector coding analyses. Thigh-shank coordination was analyzed using a modified vector coding technique on data from 2 groups of runners. Movement coordination was compared between groups using 3 techniques: (1) linear average completed with compressed data (0°-180°) and noncompressed data (0°-360°), (2) coordination phase binning analysis; and (3) a circular statistics analysis. Circular statistics (inferential) analysis provided a rigorous comparison of average movement coordination between groups. In addition, the binning analysis provided a metric for detecting even small differences in the time spent with a particular coordination pattern between groups. However, the linear analysis provided erroneous group comparisons. Furthermore, with compressed data, linear analysis led to misclassification of coordination patterns. While data compression may be attractive as a means of simplifying statistical analysis of inherently circular data, recommendations are to use circular statistics and binning methods on noncompressed data.

Oxyma-based phosphates for racemization-free peptide segment couplings.

Glyceroacetonide-Oxyma [(2,2-dimethyl-1,3-dioxolan-4-yl)methyl 2-cyano-2-(hydroxyimino)acetate (1)] displayed remarkable physico-chemical properties as an additive for peptide-forming reactions. Although racemization-free amide-forming reactions have been established for N-urethane-protected α-amino acids with EDCI, 1, and NaHCO3 in water or DMF-water media, amide-forming reactions of N-acyl-protected α-amino acids and segment couplings of oligopeptides still require further development. Diethylphosphoryl-glyceroacetonide-oxyma (DPGOx 3) exhibits relative stability in aprotic solvents and is an effective coupling reagent for N-acyl-protected α-amino acids and oligo peptide segments. The conditions reported here is also effective in lactam-forming reactions. Unlike most of the reported coupling reagents, simple aqueous work-up procedures can remove the reagents and by-products generated in the reactions.

The effect of external loads and biological sex on coupling variability during load carriage.

BACKGROUND: Load carriage is a fundamental requirement for military personnel that commonly results in lower-limb injuries. Coupling variability represents a potential injury mechanism for such repetitive tasks and its unknown whether external loads and biological sex affect coupling variability during load carriage. RESEARCH QUESTION: Is there a sex-by-load interaction during load carriage at self-selected walking speeds? METHODS: Twenty-six participants (13 males, 13 females) completed three 10-minute treadmill-based trials wearing body-borne external load (0 %BM, 20 %BM, and 40 %BM) at load-specific self-selected walking speeds. A Vicon motion capture system tracked markers with a lower-body direct-kinematic model calculating sagittal-plane segment kinematics of the thigh, shank, and foot across 19 strides. Continuous relative phase standard deviation (CRPv) provided a measure of coupling variability for each coupling angle (Thigh-Shank and Shank-Foot). The CRPv for each load and sex was compared using statistical parametric mapping repeated measures ANOVA and paired t tests. RESULTS: Significant sex-by-load interactions were reported for the Thigh-Shank coupling. Males demonstrated no significant load differences in CRPv, however, females displayed significantly higher CRPv in the 40 %BM than the 0 %BM condition. A significant main effect of load was observed in the Shank-Foot coupling, with the 40 %BM having significantly greater CRPv than the other load conditions. SIGNIFICANCE: Both biological sex and external loads significantly affected CRPv during load carriage at self-selected walking speeds. Females demonstrated greater CRPv at the heavier loads, suggesting that the perturbation from the heavier mass increases coupling variability, which may also be amplified by a greater total passive load due to their relatively higher adipose tissue compared to males. The consistent CRPv in males suggests that higher relative loads may be required to change coupling variability. Collectively, these results suggest that external load affects the coupling variability of males and females differently, providing potential for injury screening and monitoring programs.

Altered trunk and lower extremity movement coordination after neuromuscular training with and without external focus instruction: a randomized controlled trial.

BACKGROUND: This study sought to determine the effects of a 6-week neuromuscular training (NMT) and NMT plus external focus (NMT plus EF) programs on trunk and lower extremity inter-segmental movement coordination in active individuals at risk of injury. METHODS: Forty-six active male athletes (controls = 15, NMT = 16, NMT plus EF = 15) participated (age = 23.26 ± 2.31 years) in this controlled, laboratory study. Three-dimensional kinematics were collected during a drop vertical jump (DVJ). A continuous relative phase (CRP) analysis quantified inter-segmental coordination of the: (1) thigh (flexion/extension)-shank (flexion/extension), (2) thigh (abduction/adduction)-shank (flexion/extension), (3) thigh (abduction/adduction)-trunk (flexion/extension), and (4) trunk (flexion/extension)-pelvis (posterior tilt/anterior tilt). Analysis of covariance compared biomechanical data between groups. RESULTS: After 6 weeks, inter-segmental coordination patterns were significantly different between the NMT and NMT plus EF groups (p < 0.05). No significant differences were observed in CRP for trunk-pelvis coupling comparing between NMT and NMT plus EF groups (p = 0.134), while significant differences were observed CRP angle of the thigh-shank, thigh-trunk couplings (p < 0.05). CONCLUSIONS: Trunk and lower extremity movement coordination were more in-phase during DVJ in the NMT plus EF compared to NMT in active individuals at risk of anterior cruciate ligament injury. TRIAL REGISTRATION: The protocol was prospectively registered at UMIN_RCT website with ID number: UMIN000035050, Date of provisional registration 2018/11/27.

Tibial and calcaneal coupling during walking in those with chronic ankle instability.

BACKGROUND: It is estimated that nearly 2 million individuals sprain their ankle each year in the US. A majority of these are recurrent injuries, which often results in chronic ankle instability. To better understand the cause of instability, previous research has looked at the coupling or coordination between leg and foot motion during locomotion. RESEARCH QUESTION: Determine the coupling between the tibia and the calcaneus during the stance phase of walking in those without a history of ankle instability compared to those with either moderate or severe instability. METHODS: Fifty-four individuals between the age of 18-30 years (15 males; 39 females) participated in this study. Each participant's history of ankle sprains and score on the Cumberland Ankle Instability survey was used to assign them to either a no, moderate or severe instability group. Electromagnetic sensors attached to the tibia and calcaneus recorded three-dimensional movement of their tibia and calcaneus during the stance phase of barefoot over ground walking. The kinematic data was referenced to the subject's standing position and time normalized to each subject's stance phase duration. The relative phase (RP) angle and RP variability between tibia internal/external rotation and calcaneal inversion/eversion motion was then calculated. A one-way analysis of variance test was used to determine if significant differences existed between the three groups of subjects on mean RP angle or variability. An alpha level of .05 was used to determine statistical significance. RESULTS: A significant increase in RP angle and variability was found during the mid-stance phase of walking for those with severe ankle joint instability compared to those with moderate or no instability. SIGNIFICANCE: The observed decreased coordination and increased coupling variability observed for those with severe ankle instability suggests either residual ligamentous damage, inadequate sensorimotor control, or both.