SOFIE, a bicycle that supports older cyclists?

Older cyclists remain at high risk of sustaining an injury after a fall with their bicycle. A growing awareness for the need and possibilities to support safety of older cyclists has been leading to bicycle design ideas. However, the effectiveness and acceptance of such designs has not been studied yet. This study aims to analyse the effect of 3 support systems: an automatic adjustable saddle height, optimised frame and wheel geometry and drive-off assistance. The support systems are integrated on the SOFIE bicycle, a prototype bicycle designed to support older cyclists during (dis-)mounting and at lower cycling speeds. Nine older cyclists (65-80 years) were asked to cycle on a 'normal' and on the 'SOFIE' bicycle. They cycled on a parking lot to avoid interaction with traffic. The following tasks were analysed: cycling at comfortable and low speed avoiding an obstacle and (dis-)mounting the bicycle. Bicycle and cyclist motions were recorded with 10 Inertial Measurement Units and by 2 video cameras. FUSION software (LABVIEW) was used to assess kinematic parameters. First, a subjective analysis of the different cycling tasks was made, supported by video analysis. Second, differences in cyclist and bicycle kinematic parameters between the normal and SOFIE bicycle were studied for the various cycling tasks. The SOFIE bicycle was experienced as a 'supportive' and comfortable bicycle and objectively performed 'safer' on various cycling tasks. For example: The optimised frame geometry with low step-in enabled a faster (dis-)mounting time and less sternum roll angle and angular acceleration. The adjustable saddle height enabled the participants to keep both feet on the ground till they started cycling with the 'drive-off' support. The latter reduces steering activity: maximum steer angle and angular acceleration. During sudden obstacle avoidance, less upper body and thigh accelerations are recorded. In conclusion, the SOFIE bicycle was able to support older cyclists during various cycling tasks and may reduce fall risk.

Kinematic coupling relationships exist between non-adjacent segments of the foot and ankle of healthy subjects.

Pathologies of foot and ankle structures affect the kinematics at the site of the impaired structure but also influence kinematics elsewhere in the foot and ankle. An understanding of kinematic coupling relationships in the foot could provide insight into mechanisms that explain differences in foot and ankle kinematics between healthy and pathological subjects. The aim of this study was to explore foot and ankle kinematic coupling relationships between adjacent and non-adjacent segments of healthy subjects and evaluate individual variability of and effect of walking speed on these relationships. Gait of 14 subjects was recorded at comfortable and two slower walking speeds to assess individual foot kinematics during stance phase. A qualitative evaluation of the coupling relationships was made using angle-angle plots to determine their consistency, i.e. changes in movement direction of each segment occurred at the same time and the plot returned along the same line after the turning point. The Pearson correlation coefficient of determination (R(2)) was used to provide a quantitative evaluation of coupling. Individual variability was assessed with the coefficient of variation (CV). The Friedman-test was used to test the effect of walking speed. Consistent coupling relationships were observed between hindfoot in/eversion and hallux plantar/dorsiflexion (R(2) 0.7, CV 0.2), between hindfoot in/eversion and forefoot ab/adduction (R(2) 0.5, CV 0.3) and between leg rotation and midfoot collapse/elevation (R(2) 0.5, CV 0.4). Less or non-consistent coupling relationships were observed between the other studied segments. Walking speed significantly influenced coupling relationships between hindfoot and midfoot.

Foot and ankle kinematics in rheumatoid arthritis: influence of foot and ankle joint and leg tendon pathologies.

OBJECTIVE: From early onset of the disease, patients with rheumatoid arthritis (RA) experience walking impairments. Pathologic effects of RA on foot and ankle structures have been studied clinically, but little is known as to how they relate to kinematic changes during gait. The aim of this study was to explore the relationship between clinically observed pathologies of foot and ankle joints and leg tendons and the corresponding gait kinematics. METHODS: The gait of 25 subjects with varying stages of RA was recorded and foot and ankle kinematics were assessed. Magnetic resonance imaging was performed for each subject: first metatarsophalangeal (MTP) joint, midfoot, and hindfoot synovitis, erosion scores, and leg tendon involvement were determined. The joint alignment and motion score represented daily clinical assessment. The 95% confidence intervals of the Spearman's correlation coefficient tests were used to explore the relationships between the clinical and kinematic parameters. RESULTS: Maximum first MTP joint dorsiflexion at preswing was related to reduced first MTP joint passive motion, first MTP joint synovitis and erosion, midfoot synovitis and erosion, and hindfoot erosion. Midfoot pronation range of motion during single stance was related to subtalar alignment and Achilles tendon involvement. Hindfoot eversion range of motion during single stance was related to subtalar alignment and peroneus longus tendon involvement. Involvement of the tibialis posterior tendon could not be identified as an independent factor influencing foot or ankle kinematics. CONCLUSION: Our findings suggest moderate to strong relationships between foot and ankle gait kinematics and structural pathologies.

Foot and ankle joint kinematics in rheumatoid arthritis cannot only be explained by alteration in walking speed.

Rheumatoid arthritis (RA) manifests itself in the foot and ankle of RA patients. The foot and ankle joint kinematics of these patients differ from that of healthy subjects. However, the factors that lead to these differences are not yet fully understood. The aim of this study was to analyse the effect of walking speed and the disease process on foot and ankle joint kinematics of RA subjects. Gait recordings of 23 RA and 14 age-matched healthy subjects were performed and their foot and ankle joint kinematics were analysed during the stance phase of the gait cycle. Stance phase characteristics of the group of RA subjects and of the group of healthy subjects were compared. The healthy subjects walked at 100% (Vc), 75% (V75) and 50% (V50) of their comfortable walking speed. In a multi-level linear model significant differences between the two groups due to the factors walking speed and the disease process were analysed. The ankle dorsi-flexion, medial arch and hallux abduction motion at single-stance and toe-off were only influenced by the walking speed. The hallux maximum flexion at toe-off and the midfoot supination at single-stance were influenced by both the walking speed and the disease process. The hindfoot eversion motion at single-stance was only influenced by the disease process. In conclusion, the reduction of walking speed of RA subjects compared to healthy subjects does not explain all of the observed foot and ankle kinematics differences.

The effects of walking speed on forefoot, hindfoot and ankle joint motion.

BACKGROUND: Foot and ankle joint kinematic differences have been identified between healthy subjects and subjects with various pathologies suffering from foot and ankle impairments. Changes in temporal factors such as walking speed and double stance time are also found in these pathological conditions. As such, in theory, these factors would also influence the kinematics and hence make it difficult to ascertain the effects of the disease on the kinematics. The aim of this study was to analyse foot and ankle kinematics from gait recordings of healthy subjects walking at comfortable and slower speeds. METHODS: Gait patterns of 14 healthy subjects were recorded. The subjects were first asked to walk at a comfortable speed and then at predefined speeds of 75% and 50% of their comfortable walking speed respectively. Temporal variables were calculated. Foot and ankle joint kinematics were determined from marker-recordings. FINDINGS: The subjects walked at mean velocities of 1.28 m/s, 0.97 m/s and 0.65 m/s. With decreasing walking speed the minimum tibio-talar plantar-flexion and maximum hallux dorsi-flexion at toe-off decreased significantly between 3 degrees and 9 degrees. The minimum medial arch at toe-off and minimum midfoot supination at mid-stance were significantly affected by the walking speed. The corresponding individual session differences were small (1 degrees -2 degrees), but the reliability was high and hence the differences were considered clinically relevant. INTERPRETATION: Walking speed significantly affected foot and ankle kinematics. Studies aiming to improve the understanding of the effects of foot and ankle pathologies on foot and ankle kinematics should take the walking speed into account.

Prevalence of blindness and visual impairment in the region of Ségou, Mali. A baseline survey for a primary eye care programme.

A community-based cross-sectional study on the prevalence and causes of blindness and visual impairment was conducted between July and August 1990 in three rural districts in Ségou region, Mali. The study population consisted of 5871 villagers. In the study area, the overall prevalence of bilateral blindness was 1.7% (standardized rate for age 2.0% +/- 0.4%), of bilateral visual impairment 1.7% (2.1% +/- 0.4%), of unilateral blindness 1.7% (2.2% +/- 0.4%) and of unilateral visual impairment 1.0% (1.2 +/- 0.3%). No important differences were found between districts. Cataract was the most common cause of visual loss (54%) and was most prevalent among those over 50 years of age. In 43%, unilateral blindness was associated with trauma. Other major eye diseases accounting for high percentages of visual impairment were trachoma and glaucoma. Xerophthalmia appeared to be a major public health problem among children in the age group 0-5. It was concluded that blindness is a major public health problem in this region. Some recommendations are given for strengthening integrated primary eye care at the district level in Ségou region.