Inter-individual similarities and variations in muscle forces acting on the ankle joint during gait

Muscle forces acting over the ankle joint play an important role in the forward progression of the body during gait. Yet despite the importance of ankle muscle forces, direct in-vivo measurements are neither possible nor practical. This makes musculoskeletal simulation useful as an indirect technique to quantify the muscle forces at work during locomotion. The purpose of this study was to: 1) identify the maximum peaks of individual ankle muscle forces during gait; 2) investigate the order over which the muscles are sorted based on their maximum peak force. Three-dimensional kinematics and ground reaction forces were measured during the gait of 10 healthy subjects, and the data so obtained were input into the musculoskeletal model distributed with the OpenSim software. In all 10 individuals we observed that the soleus muscle generated the greatest strength both in dynamic (1856.1N) and isometric (3549N) conditions, followed by the gastrocnemius in dynamic conditions (1232.5N). For all other muscles, however, the sequence looks different across subjects, so the k-means clustering method was used to obtain one main order over which the muscles’ peak-forces are sorted. The results indicate a common theme, with some variations in the maximum peaks of ankle muscle force across subjects

Influence of a nine-day alpine ski training programme on the postural stability of people with different levels of skills

Study aim: In alpine skiing, balance is one of the key elements that determine the effectiveness of the ride. Because of ski boots, the foot and ankle joint complex is excluded from the process of maintaining the stability of the body. The aim of the study was to determine to what extent a few days of skiing activities and the level of technical skills affect the skiers’ level of postural stability

Evaluation of Postural Stability in Young and Elderly Women

Study aim: Assessment of postural stability performed on an unstable stabilometry platform. Comparison of the results ob­tained by two groups consisting of elderly (OW) (60+ years old) and younger women (YW).Material and methods: Seventy-three female volunteers were divided into two groups: 40 young women (20.2 ± 1.75), and 32 elderly women (68.3 ± 7.43). Participants performed five stability tests on Biodex Balance System SD: three 20-second tries, the Postural Stability Test (PST) and the Fall Risk Test (FRT). Three stability indexes - overall (OSI), anterior-posterior (APSI), and medial-lateral (MLSI) - both with eyes open (EO) and closed (EC) were analyzed. The impact of vision on balance was calculated as EC-EO. Also effect size was calculated and evaluated.Results: All of the parameters differed significantly between groups in favour of YW. The largest difference in significance as well as effect size was noted for FRT, p < 0.001 and 1.86 respectively. Tries measure the impact of vision on balance (EC-EO). The results concerning tries with EC-EO showed the strongest discrimination between groups - OSI p = 0.0088 (relative differ­ence 0.23 ± 0.26) and APSI p = 0.0268 (relative difference 0.17 ± 0.2). YW had a significantly better outcome.Conclusions: YW had better results in all of the parameters taken into consideration, with most of them being significant. This confirms that all of the regressive changes appearing with age influence balance. Lack of visual input (EC) in OW caused sig­nificantly worse results in most of the measured parameters, showing that vision is a very important factor for balance mainte­nance in the elderly

A new method of determination of phases and symmetry in stand-to-sit-to-stand movement

Objectives: Determination of the phases in a stand-to-sit-to-stand task based on a derivative of the parameter with the lowest variance calculated based on the modified symmetry index. Material and Methods: The study group comprised 11 healthy women and 11 healthy men from the University of Physical Education in Warsaw. The examination of the kinematic and kinetic parameters of sitting down and standing up from a chair was carried out using the Vicon Mx system and Kistler force platforms. Results: The modified symmetry index was employed to select the parameters used to choose those with the lowest variance. Consequently, the phases in a stand-to-sit-to-stand task were determined. Conclusions: It was demonstrated that the task of sitting down is a reverse task with respect to standing up in terms of the symmetry of the parameters analyzed

Types of falls and strategies for maintaining stability on an unstable surface

Background Falls constitute an important health issue. They cause significant morbidity, mortality and have marked psychological effects on the individual, too. The aim of this study has been to determine parameters describing human movement strategies for balance and the reaction if balance is lost as a result of an unstable ground, and to attempt to describe the types of falls. Material and Methods The study group comprised 20 volunteers. Kinematic parameters of falling and dynamic stability were measured using the Vicon Motion System and the Biodex Balance System SD. During the test, subjects stood for 20 s on the tilting platform. The analysis was conducted based on the first recordings, when the participants were not prepared for the event and their reactions were natural. A cluster analysis tool was applied to divide the behavior of people during the test. Results Based on motion range for kinematic parameters, the cluster analysis revealed 2 types of human behavior: falling (stepping) and restoring balance. Two types of falls were also observed: side and back falls. Moreover, on the basis of angular values for tilting plate, 4 zones were determined. The frequency of access to these zones by each joint revealed 3 strategies to maintain balance: ankle, knee and hip strategy. Conclusions A set of initial conditions that may be used for future numerical simulations was also determined. Furthermore, the results presented in this study are likely to support the analysis of the effects and the falling patterns. Med Pr 2018;69(3):245–25

The Impact of a Vestibular-Stimulating Exercise Regime on Postural Stability in People with Visual Impairment

The aim of the study was to assess the impact of a vestibular-stimulating exercise regime on postural stability in individuals with visual impairment. The study group consisted of 70 people, including 28 persons (15 female and 13 male) with visual impairment and 42 (21 female and 21 male) without visual impairment. Each individual in the group with visual impairment was medically qualified for a 3-month training program. The research methodology included medical examination, anthropometric tests, and stabilometry tests on a Biodex Balance System SD (BBS). The tests were conducted twice: once before the start of training and again after 3 months of rehabilitation. The group with visual impairment showed significantly worse postural stability results than the control group for most of the stability parameters evaluated (OSI, APSI, and MLSI). Differences were noted between the groups with and without visual impairment for dynamic tests in women and for static tests in men. After training, the two groups showed roughly similar results for the stabilometry test with eyes closed. We conclude that exercises stimulating the vestibular system with head and body movements should be recommended for individuals with visual impairments to achieve better balance retention

The impact of a vestibular-stimulating exercise regimen on postural stability in women over 60

Background/Objective: The aim of this study was to assess whether a program of exercise specifically designed to target the vestibular organ improved the postural stability of female participants over 60 years old. Methods: Twenty-eight healthy female volunteers aged from 60 years to 76 years were assigned to a group (n = 15) engaging in vestibular-stimulating exercises, or to a control group (n = 13) engaging in traditional training exercises. Training sessions (∼45 minutes each) occurred twice a week over the course of 3 months. The following parameters were analyzed before and after training for both groups: stabilogram ellipse area and radii, total length of stabilogram, and visual-inspection indicator (eyes open). Results: Results in terms of stabilogram ellipse area and radius without visual control (eyes closed) revealed statistically significant differences in the experimental group between the values before and after the training regimen (74.8 ± 51.6 − 54.5 ± 42.5 for area of ellipse, 6.6 ± 2.8 − 5.8 ± 2.8 for axis minor, 13.2 ± 4.3 − 11.1 ± 3.3 for axis major, respectively). No significant changes were observed in the control group. Conclusion: Exercises stimulating the vestibular organ, such as those described herein, should be a part of efforts to improve balance in older people

Types of falls and strategies for maintaining stability on an unstable surface

Background Falls constitute an important health issue. They cause significant morbidity, mortality and have marked psychological effects on the individual, too. The aim of this study has been to determine parameters describing human movement strategies for balance and the reaction if balance is lost as a result of an unstable ground, and to attempt to describe the types of falls. Material and Methods The study group comprised 20 volunteers. Kinematic parameters of falling and dynamic stability were measured using the Vicon Motion System and the Biodex Balance System SD. During the test, subjects stood for 20 s on the tilting platform. The analysis was conducted based on the first recordings, when the participants were not prepared for the event and their reactions were natural. A cluster analysis tool was applied to divide the behavior of people during the test. Results Based on motion range for kinematic parameters, the cluster analysis revealed 2 types of human behavior: falling (stepping) and restoring balance. Two types of falls were also observed: side and back falls. Moreover, on the basis of angular values for tilting plate, 4 zones were determined. The frequency of access to these zones by each joint revealed 3 strategies to maintain balance: ankle, knee and hip strategy. Conclusions A set of initial conditions that may be used for future numerical simulations was also determined. Furthermore, the results presented in this study are likely to support the analysis of the effects and the falling patterns. Med Pr 2018;69(3):245–25