Assessment of the variability of vastii myoelectric activity in young healthy females during walking: a statistical gait analysis.

The study was designed to assess the natural variability of the activation modalities of vastus medialis (VM) and vastus lateralis (VL) during walking at a self-selected speed and cadence of 30 young, healthy, females. This was achieved by conducting statistical gait analysis on the surface electromyographic signals from hundreds of strides for each subject. Results revealed variability in the number of activations, occurrence frequency, and onset-offset instants across the thousands of strides analyzed. However, despite the variability, there was one activation occurrence which remained consistent across subjects for both VM and VL. This occurred from terminal swing to the following loading response (observed in 100% of strides). A second, less frequent, activation occurred between mid-stance up to pre-swing (observed in 39.3±22.4% of strides for VM and in 35.1±20.6% for VL). No significant differences (p>0.05) were observed in the onset-offset instants or in the occurrence frequency, which suggest a simultaneous recruitment of VM and VL. This "normality" pattern represents the first attempt at developing a reference frame for vastii sEMG activity during walking, that is able to include the physiological variability of the phenomenon and control the confounding effects of age and gender.

Functional reach test: movement strategies in diabetic subjects.

Functional reach (FR) is a clinical measure, defined as the maximum distance one can reach, forward beyond arm's length, able to identify elderly subjects at risk of recurrent falls. Subjects, exhibiting the same FR can perform the motor task in different ways: a kinematic analysis of the FR, task can help to identify the motor strategy adopted. The FR test was applied to 17 diabetic non-neuropathic, (CTRL) and 37 neuropathic (DN) subjects. Motor strategies adopted were defined as: "hip" or "other" strategy; the latter included: "mixed" and "trunk rotation" strategies. Principal Component Analysis and non-parametric statistical tests were used to study the different execution modalities of the FR test. Results show that, in CTRL, the most important parameters are those related to trunk flexion in the sagittal plane. Instead, for DN, the main features are related not only to trunk flexion but also to trunk rotation in the transverse plane. Percentages of subjects who used "hip" or "other" strategies are similar for CTRL and DN subjects. However, within the "other" strategy group, the percentage of DN that used a "trunk rotation" strategy was much higher than for CTRL. Results show that individuals, although exhibiting the same reaching distance, adopt different movement strategies. Consequently it is important to evaluate the kinematic behaviour and not only the clinical measure, because the evaluation of the motor strategy might be useful in the early detection of subjects at risk of postural instability.

Assessment of the activation modalities of gastrocnemius lateralis and tibialis anterior during gait: a statistical analysis.

Aim of the study was to identify the different modalities of activation of gastrocnemius lateralis (GL) and tibialis anterior (TA) during gait at self-selected speed, by a statistical analysis of surface electromyographic signal from a large number (hundreds) of strides per subject. The analysis on fourteen healthy adults showed a large variability in the number of activation intervals, in their occurrence rate, and in the on-off instants, within different strides of the same walk. For each muscle, the assessment of the different modalities of activation (five for muscle) allowed to identify a single pattern, common for all the modalities and able to characterize the behavior of muscles during normal gait. The pattern of GL activity centered in two regions of the gait cycle: the transition between flat foot contact and push-off (observed in 100% of total strides) and the final swing (67.1 ± 15.9%). Two regions characterized also the pattern of TA activity: from pre-swing to following loading response (100%), and the mid-stance (30.5 ± 15.0%). This "normality" pattern represents the first attempt for the development in healthy young adults of a reference for dynamic EMG activity of GL and TA, in terms of variability of on-off muscular activity and occurrence rate during gait.