The surface electromyographic evaluation of the Functional Reach in elderly subjects.

This study proposes a comprehensive assessment of myoelectric activity of the main muscles involved in the Functional Reach (FR) test, in 24 elderly subjects. A specific protocol for the surface electromyography (sEMG) signal acquisition during FR-test was developed. Results show that anterior muscles activate following a caudo-cranial order. Tibialis Anterior (TA) is the first to be activated (-18.0±16.3% of the FR-period), together with Rectus Femoris (-10.4±17.9%). Then, Rectus Abdominis (19.7±24.7%) and Sternocleidomastoideus (19.9±15.6%) activate after the FR-start. Hamstrings, Soleus, and L4-level Erectores Spinae (posterior muscles) activate after the FR-start in this order (11.4±16.8%, 17.7±16.6%, and 35.2±29.0%, respectively) and remain active until the movement end. The analysis of the kinematic strategies adopted by subjects revealed an association between TA-activation patterns and two kinematic strategies (hip/mixed strategy), quantified by an increase (p<0.05) of TA-activity duration in subjects adopting the hip strategy (89.9±34.5) vs. subjects adopting the mixed strategy (27.0±16.8). This suggests that TA sEMG activity could be able to discriminate among kinematic strategies, providing different information on balance control. Thus, the present analysis represents the first attempt to quantify the sEMG activity during FR-test in elderly subjects, providing an early contribution in building a reference frame for balance assessment in clinical context.

A statistical approach to discriminate between non-fallers, rare fallers and frequent fallers in older adults based on posturographic data.

BACKGROUND: Identification of future non-fallers, infrequent and frequent fallers among older people would permit focusing the delivery of prevention programs on selected individuals. Posturographic parameters have been proven to differentiate between non-fallers and frequent fallers, but not between the first group and infrequent fallers. METHODS: In this study, postural stability with eyes open and closed on both a firm and a compliant surface and while performing a cognitive task was assessed in a consecutive sample of 130 cognitively able elderly, mean age 77(7)years, categorized as non-fallers (N=67), infrequent fallers (one/two falls, N=45) and frequent fallers (more than two falls, N=18) according to their last year fall history. Principal Component Analysis was used to select the most significant features from a set of 17posturographic parameters. Next, variables derived from principal component analysis were used to test, in each task, group differences between the three groups. FINDINGS: One parameter based on a combination of a set of Centre of Pressure anterior-posterior variables obtained from the eyes-open on a compliant surface task was statistically different among all groups, thus distinguishing infrequent fallers from both non-fallers (P<0.05) and frequent fallers (P<0.05). INTERPRETATION: For the first time, a method based on posturographic data to retrospectively discriminate infrequent fallers was obtained. The joint use of both the eyes-open on a compliant surface condition and this new parameter could be used, in a future study, to improve the performance of protocols and to verify the ability of this method to identify new-fallers in elderly without cognitive impairment.

Muscle activation patterns related to diabetic neuropathy in elderly subjects: A Functional Reach Test study.

BACKGROUND: This study was designed to assess, in healthy elderly, non-neuropathic and neuropathic diabetic subjects, the activation patterns of the main muscles involved in the Functional Reach Test, a well-recognized method to identify elderly subjects at risk of balance impairments. METHODS: Surface electromyographic analysis of Sternocleidomastoideus, Rectus Abdominis, Erectores Spinae at L4 level, Rectus Femoris, Hamstrings, Tibialis Anterior and Soleus was performed in 10 healthy, 10 diabetic non-neuropathic and 10 diabetic neuropathic subjects. FINDINGS: Results showed that in every group the first motor is Tibialis Anterior, that is recruited before the start of the test. An earlier activation of Tibialis Anterior (P<0.05) was detected in diabetic neuropathic (ON at -24% of the test period), compared with healthy (-11%) and diabetic non-neuropathic (-13%) groups. A significant earlier activation of Sternocleidomastoideus and Rectus Abdominis was found in diabetic neuropathic group, only with respect to healthy subjects. No significant difference was found in Rectus Femoris, Soleus, Hamstrings an Erectores Spinae onset among the three groups. INTERPRETATION: Results suggest a trend of diabetic neuropathic patients in earlier anticipation of the activation of the anterior body-muscles. In particular, the earlier onset of Tibialis Anterior is likely to be performed to adjust the movement timing and to compensate for the delay in the recruitment of the motor units. This anticipation might be involved in the altered postural control with increased balance impairment detected in diabetic neuropathic patients, and thereby it might also be proposed as an index of neuropathy, evidenced in a simple and non-invasive manner.

A stereophotogrammetric-based method to assess spatio-temporal gait parameters on healthy and Parkinsonian subjects.

Generally, the study of gait requires the detection of successive heel contacts and toe-off instants. Traditional gait analysis methods obtain these gait events using dynamometric platforms together with stereophotogrammetric data. Usually, are kept valid only those walking trials where the subjects step on each platform by only one foot. For subjects suffering from walking impairments it is very difficult or sometimes impossible to walk naturally and step properly on the dynamometric platforms. The aim of the present study is to propose a new method to identify, in an automatic manner, the initial contact (IC) and the toe-off (TO) time instants using only stereophotogrammetric data and a classic gait analysis protocol. The assessment of spatio-temporal gait variables during natural walking is also performed. The study consisted in analyzing healthy and Parkinsonian elderly subjects. The reliability of the proposed stereophotogrammetric-based method was tested by direct comparison with the IC and TO instants determined by the dynamometric platform data. The absence of any statistically significant differences between the values estimated by the two different modalities, highlights the reliability of the proposed method in the assessment of these two gait events. Results underline, as expected, the reduction of walking velocity in pathological patients during free ambulation. The present study proposes this method as a valid alternative to the traditional technique that use dynamometric platforms to identify main gait events, for subjects unable to walk naturally and to step properly on the platforms.

Assessment of the activation patterns of the muscles involved in the FR test in diabetic neuropathic patients.

This study was designed to assess, in elderly neuropathic diabetic (DN) patients, the activation patterns of the main muscles involved in the Functional Reach (FR) Test, a well-recognized method to identify elderly subjects at risk of recurrent falls. Surface electromyographic (sEMG) analysis of Sternocleidomastoideus (Scm), Rectus Abdominis (RAbd), Erectores Spinae at L4 level (L4), Rectus Femoris (RF), Hamstrings (Ham), Tibialis Anterior (TA) and Soleus (Sol) was performed to this aim. Results in DN patients are compared with a control group (CH) of healthy age-matched subjects. In DN patients, TA is identified as the first muscle to be recruited (ON at -34% of the FR-period) before the movement start, in order to initiate the body forward displacement. RF is the first muscle to be recruited after TA and, togheter with RAbd, showed a progressive earlier onset from CH group. Sol and Ham (ON after the FR-start), followed by L4, act mainly as tonic muscles, opposing the movement and preventing falls. Compared to the CH group, the DN subjects show an anticipatory recruitment (-34%±6%) of TA, showing a statistically significant difference (p<;0.05) in comparison to CH group, together with the Scm activation. Results suggest a trend of DN patients in anticipating the activation of the anterior muscles of the body. This is likely due to an attempt to compensate the neuropathy-related proprioception dysfunction and to adjust the movement timing. In conclusion, the present study shows that sEMG is a suitable tool to deepen the interpretation of the FR-test execution and proposes the earlier start of TA as a possible element to identify the presence of neuropathy in diabetic subjects.

Evaluation of gender-related differences in co-contraction activity of shank muscles during gait.

This study aims to investigate the possible differences between genders in co-contractions of tibialis anterior (TA) and gastrocnemius lateralis (GL), during walking at self-selected speed. To this purpose, the statistical gait analysis (SGA) was performed on seven female (F-group) and seven male (M-group) adults. SGA is a recently developed methodology for the characterization of gait, by averaging spatiotemporal and electromyographic parameters over hundreds of strides per subject. Co-contractions were assessed as the overlapping periods between TA and GL activity. Results showed that four co-contraction intervals are present during gait cycle in both groups. No relevant differences between genders were detected in onset-offset time instants of co-activations or in their temporal length. On the contrary, significant differences were observed in the number of strides where each co-contraction happens (i.e. the occurrence frequency). All the four co-contraction intervals result significantly (p<;0.05) more recurrent in females compared to males. This outcome suggests a larger presence of co-contraction activity in females walking, related to a female tendency for a more complex muscular strategy during gait. These findings could be useful to better understand gender differences in walking mechanisms and to develop separated normal walking reference frames for males and females.

Assessment of walking speed by a goniometer-based method.

A quantitative gait analysis is essential to evaluate the kinematic, kinetic and electromyographic gait patterns. These patterns are strongly related to the individual spatio-temporal parameters that characterize each subject. In particular, gait speed is one of the most important spatio-temporal gait parameters: it influences kinematic, kinetic parameters, and muscle activity too. The aim of the present study is to propose a new method to assess stride speed using only 1-degree-of-freedom electrogoniometers positioned on hip and knee joints. The model validation is performed comparing the model results with those automatically obtained from another gait analysis system: GAITRite. The results underline the model reliability. These results show that essential spatio-temporal gait parameters, and in particular the speed of each stride, can be determined during normal walking using only two 1-dof electrogoniometers. The method is easy-to-use and does not interfere with regular walking patterns.

Integration of smartphones and webcam for the measure of spatio-temporal gait parameters.

A very low cost prototype has been made for the spatial and temporal analysis of human movement using an integrated system of last generation smartphones and a highdefinition webcam, controlled by a laptop. The system can be used to analyze mainly planar motions in non-structured environments. In this paper, the accelerometer signal as captured by the 3D sensor embedded in one smartphone, and the position of colored markers derived by the webcam frames, are used for the computation of spatial-temporal parameters of gait. Accuracy of results is compared with that obtainable by a gold-standard instrumentation. The system is characterized by a very low cost and by a very high level of automation. It has been thought to be used by non-expert users in ambulatory settings.