Spanning set defines variability in locomotive patterns

The purpose of the investigation was to use the spanning set methodology to quantify variability in locomotive patterns and to compare this method with traditional measures of variability. Subjects ran on a treadmill while sagittal plane kinematic data were collected with a high-speed (180 Hz) camera. Changes in variability were evaluated as the subject ran barefoot and in shoes. Mean ensemble curves for the knee angle during the stance period were created for each condition. From these curves, traditional measures of variability were calculated using the coefficients of variation (CVs), and the mean deviation (MD). Spanning set vectors were defined from the coefficients of polynomials that were fitted to the respective standard deviation curves. The magnitude of the spanning set was determined by calculating the norm of the difference between the two vectors. The normalised difference between the two conditions was 6.6%, 6.9% and 98%, for the MD, CV and spanning sets, respectively. The results indicated that the spanning set was capable of statistically (p\u3c0.05) determining differences in variability between the two conditions. CV and MD measures were unable to detect statistical differences (p\u3e0.05) between the two conditions. The spanning set provides an alternative, and sensitive measure for evaluating differences in variability from the mean ensemble curve

The Effect of a Short Duration, High Intensity Exercise Intervention on Gait Biomechanics in Patients With COPD: Findings From a Pilot Study

Previous work has shown that patients with chronic obstructive pulmonary disease (COPD) demonstrate changes in their gait biomechanics as compared to controls. This pilot study was designed to explore the possibility that biomechanical alterations present in COPD patients might be amenable to treatment by exercise training of skeletal muscle. This study investigated the effect of a 6-week exercise intervention on gait biomechanics in patients with COPD under both a rest and a non-rested condition. Seven patients with COPD underwent a supervised cardio-respiratory and strength training protocol 2-3 times per week for 6-weeks for a total of 16-sessions. Spatiotemporal, kinematic and kinetic gait variables were collected prior to and post intervention. All patients demonstrated significant improvements in strength following the intervention. The knee joint biomechanics demonstrated a significant main effect for intervention and for condition. Step width demonstrated a significant interaction as it decreased from pre- to post-intervention under the rest condition and increased under the non-rested condition. It does appear that being pushed (non-rested) has a strong influence at the knee joint. The quadriceps muscles, the primary knee extensors, have been shown to demonstrate muscular abnormalities in patients with COPD and the intervention may have influenced gait patterns through an effect on this skeletal muscle structure and function. Additionally, the intervention influenced step width closer to a more healthy value. Patients with COPD are more likely to fall and step width is a risk factor for falling suggesting the intervention may address fall risk. Whether a longer duration intervention would have more profound effects remains to be tested

Intralimb coordination following obstacle clearance during running: the effect of obstacle height

The purpose of this study was to investigate the different coordination strategies used following obstacle clearance during running. Ten subjects ran over a level surface and over obstacles of six different heights (10, 12.5, 15, 17.5, 20 and 22.5% of their standing height). Analysis based upon the dynamical systems theory (DST) was used and the phasing relationships between lower extremity segments were examined. The results demonstrated that the increasing obstacle height elicited behavioral changes. The foot and the leg became more independent in their actions, while the leg and the thigh strengthened their already stable relationship. The 15% obstacle height seems to be a critical height for the observed changes

Chapter 9: Biomechanics

Biomechanics is a discipline. A discipline deals with understanding, predicting, and explaining phenomena within a content domain, and biomechanics is the study of the human body in motion. By applying principles from mechanics and engineering, biomechanists are able to study the forces that act on the body and the effects they produce (Bates, 1991). Hay (1973) describes biomechanics as the science that examines forces acting on and within a biological structure and the effects produced by such forces, whereas Alt (1967) describes biomechanics as the science that investigates the effect of internal and external forces on human and animal bodies in movement and at rest. Each of these definitions describes the essential relationship between humans and mechanics found in biomechanics

Do lower-extremity joint dynamics change when stair negotiation is initiated with a self-selected comfortable gait speed?

Previous research on the biomechanics of stair negotiation has ignored the effect of the approaching speed. We examined if initiating stair ascent with a comfortable self-selected speed can affect the lower-extremity joint moments and powers as compared to initiating stair ascent directly in front of the stairs. Healthy young adults ascended a custom-built staircase instrumented with force platforms. Kinematics and kinetics data were collected simultaneously for two conditions: starting from farther away and starting in front of the stairs and analyzed at the first and second ipsilateral steps. Results showed that for the first step, participants produced greater peak knee extensor moment, peak hip extensor and flexor moments and peak hip positive power while starting from farther away. Also, for both the conditions combined, participants generated lesser peak ankle plantiflexor, greater peak knee flexor moment, lesser peak ankle negative power and greater peak hip negative power while encountering the first step. These results identify the importance of the starting position in experiments dealing with biomechanics of stair negotiation. Further, these findings have important implications for studying stair ascent characteristics of other populations such as older adults

Methods to Improve the Reliability of the Functional Reach Test in Children and Adolescents With Typical Development

Purpose: Test-retest reliability of the Functional Reach Test was examined in children with typical development by comparing standard and alternate methods. Methods: Eighty subjects ages seven to 16 years were tested and 69 retested for four methods of Functional Reach Test (ie, one-arm finger-to-finger, two-arm finger-to-finger, one-arm toe-to-finger, and two-arm toe-to-finger). Intraclass correlation coefficients and limits of agreement were calculated. Results: Intraclass correlation coefficients were high in toe-to-finger measurement methods (0.97– 0.98) for the entire group and specific age groups (00.83–0.93). Toe-to-finger methods were more reliable than finger-to-finger methods. The two-arm toe-to-finger method had the best limis of agreement with approximately ±5 cm indicated by the 95% confidence interval. Conclusions: Test-retest reliability using a toe-to-finger method of measuring is stronger than previously reported when using traditional methods. Limits of agreement analyses imply a change of 5 cm or more is likely to represent a true clinical difference when using the two-arm toe-to-finger method

Patients with Chronic Obstructive Pulmonary Disease Walk with Altered Step Time and Step Width Variability as Compared with Healthy Control Subjects

Rationale: Compared with control subjects, patients with chronic obstructive pulmonary disease (COPD) have an increased incidence of falls and demonstrate balance deficits and alterations in mediolateral trunk acceleration while walking. Measures of gait variability have been implicated as indicators of fall risk, fear of falling, and future falls. Objectives: To investigate whether alterations in gait variability are found in patients with COPD as compared with healthy control subjects. Methods: Twenty patients with COPD (16 males; mean age, 63.6 ± 9.7 yr; FEV1/FVC, 0.52 ± 0.12) and 20 control subjects (9 males; mean age, 62.5 ± 8.2 yr) walked for 3 minutes on a treadmill while their gait was recorded. The amount (SD and coefficient of variation) and structure of variability (sample entropy, a measure of regularity) were quantified for step length, time, and width at three walking speeds (self-selected and ±20% of self-selected speed). Generalized linear mixed models were used to compare dependent variables. Results: Patients with COPD demonstrated increased mean and SD step time across all speed conditions as compared with control subjects. They also walked with a narrower step width that increased with increasing speed, whereas the healthy control subjects walked with a wider step width that decreased as speed increased. Further, patients with COPD demonstrated less variability in step width, with decreased SD, compared with control subjects at all three speed conditions. No differences in regularity of gait patterns were found between groups. Conclusions: Patients with COPD walk with increased duration of time between steps, and this timing is more variable than that of control subjects. They also walk with a narrower step width in which the variability of the step widths from step to step is decreased. Changes in these parameters have been related to increased risk of falling in aging research. This provides a mechanism that could explain the increased prevalence of falls in patients with COPD

Effects of Varying Amounts of Pronation on the Mediolateral Ground Reaction Forces During Barefoot Versus Shod Running

Despite extensive research on running mechanics, there is still a knowledge gap with respect to the degree of relationship between mediolateral ground reaction forces (ML-GRF) and foot pronation. Our goal was to investigate whether differences exist in ML-GRF among runners that exhibit different degrees of pronation. Seventeen male and 13 female recreational runners ran with and without shoes while ML-GRF and frontal kinematics were collected simultaneously. Subjects were divided into groups based upon their peak eversion (low pronation, middle pronation, high pronation). Discrete parameters from the ML-GRF were peak forces, respective times of occurrence, and impulses. No significant differences were found between groups regarding the magnitude of ML-GRF. Based upon the relative times of occurrence, the peak medial GRF occurred closer to the peak eversion than the peak lateral GRF. Findings support the idea that the ML-GRF have less to do with pronation than previous research suggested

Factors Affecting Functional Reach Scores in Youth with Typical Development

Purpose: Functional Reach Test scores were examined for the effects of traditional and alternate methods and subject characteristics. Methods: Eighty subjects aged 7 to 16 years were tested. Effects of measurement method (from finger-to-finger or from toe-to-finger) and style of reach (1 or 2 arms) were investigated. Five subject variables were analyzed for interactions among the methods and groups defined by subject characteristics. Results: Measurement method and style of reach showed a significant interaction. Interaction of method with subject characteristics was significant for age, height, and base of support only. Height groups by quartile were significantly different and scores increased with height, especially in toes-to-finger methods. Conclusions: Functional Reach Test scores were affected by method of reach and method of measurement. Height categories may be more useful when using the test for discriminative purposes, especially with toes-to-finger methods