Postural imbalance: An early sign in HIV-1 infected patients

Summary We have recorded postural performance in 50 HIV-infected patients in different stages of the disease (Walter Reed (WR) stages I–VI) by means of a force measuring platform. The results were compared with 50 age-matched controls. A significant instability was particularly evident when standing on an unstable foot support. In patients standing with eyes closed, postural sway was significantly higher in every patient group (WR I–II:P<0.02, WR III–V:P<0.001, WR VI:P<0.001). Patients in stage WR I–II showed no relevant neurological abnormalities. In agreement with other neurophysiological data in the literature we suggest that postural imbalance could be an early sign of central nervous system penetration of HIV. No correlation with electromyographic or cerebrospinal fluid findings could be found.     

Visuelle Prävention der Bewegungskrankheit im Auto

Zusammenfassung Mit Hilfe von Autoversuchen wurde die früher im Labor für Winkelbeschleunigungen gefundene visuelle Modulation vestibulären Schwindels auf ihre praktische Bedeutung zur physikalischen Prävention von Bewegungskrankheit, vorwiegend durch Linearbeschleunigungen auf der Straße, überprüft.Achtzehn freiwillige Versuchspersonen wurden an drei nicht aufeinanderfolgenden Tagen als Beifahrer in einem Kraftfahrzeug auf einer geraden Autobahn-Teststrecke über 4 × 1,7 km einem festgelegten Muster richtungswechselnder Linearbeschleunigungen (0,1–1,2 g) unter Variation der gleichzeitigen visuellen Reizbedingungen ausgesetzt: I) Augen auf, visuelle Kontrolle der Fahrzeugbeschleunigungen; II) Augen zu; III) Augen auf, künstlicher stationärer Ganzfeldreiz (Kartenlesen).Die Stärke der durch die alternierenden Beschleunigungen ausgelösten Bewegungskrankheit (magnitude estimation 1–10) wurde signifikant durch simultane visuelle Reizbedingungen bestimmt: a) geringe Übelkeit (<1) unter adäquater visueller Bewegungswahrnehmung; b) mittlere Übelkeit (2) bei rein vestibulärer Reizung und geschlossenen Augen; c) starke Übelkeit (>5), wenn die visuelle Information scheinbarer Unbewegtheit den labyrinthären Beschleunigungsreizen widerspricht. Bewegungskrankheit in Autos entsteht vorwiegend durch visuell-vestibuläre Reizkonflikte und läßt sich wirkungsvoll durch visuelle Kontrolle der auftretenden Fahrzeugbeschleunigungen unterdrücken.Mit Unterstützung der Deutschen Forschungsgemeinschaft Br639/3 Bewegungskrankheit und der DFVLR Biomedizinische Untersuchungen des Experiments Space-Sled     

Cardiovascular risk factors in overweight German children and adolescents: relation to gender, age and degree of overweight

OBJECTIVE: So far in Europe, no large studies have been published on the frequencies of the cardiovascular risk factors hypertension and dyslipidaemia in overweight children. METHODS: Diagnosis of hypertension, decreased HDL-cholesterol, increased triglycerides, total and LDL-cholesterol were documented for 1004 overweight children and adolescents (aged 4-8 years, 52% girls, BMI-SDS in median 2.43) referred to four obesity centres. Hypertension and dyslipidaemia were defined by cut off points above the 95th percentile of healthy children. Multivariate linear regression was conducted for the dependent variables systolic and diastolic blood pressure, triglycerides, HDL-, LDL-, and total cholesterol, including gender, degree of overweight (SDS-BMI) and age as independent variables. RESULTS: Thirty-seven percent of the children studied suffered from hypertension, 27% displayed increased total cholesterol, 26% increased LDL-cholesterol, 20% increased triglycerides and 18% decreased HDL-cholesterol. Seventy percent of all children had at least one unfavourable cardiovascular risk factor. Hypertension and dyslipidaemia were observed in any age group and in any degree of overweight at least twofold above the suspected rate of 5%. SDS-BMI was significantly related to blood pressure (systolic: coefficient 7.26, p < 0.001, diastolic: coefficient 3.21, p < 0.001), weakly to triglycerides (coefficient 0.12, p = 0.007), slightly negatively to HDL-cholesterol (coefficient -0.06, p = 0.001) and not related to total and LDL-cholesterol. Age was positively related to blood pressure (systolic: coefficient 2.436, p < 0.001, diastolic: coefficient 0.54, p < 0.001) and negatively to HDL cholesterol (coefficient -0.02, p < 0.001). CONCLUSION: Cardiovascular risk factors were frequently present in a large collective of overweight European children and adolescents. They occurred mostly independently of age, gender and degree of overweight. Therefore, screening for cardiovascular risk factors seems meaningful at any age and degree of overweight in childhood.     

Fahrradfahren Querschnittgelähmter mittels funktioneller Elektrostimulation

Cycling using functional electrical stimulation offers paraplegics the possibility of muscle and cardiovascular training as well as the chance for independent locomotion. To investigate whether this method might be suitable for a large group of paraplegics, the first German feasibility study of functional electrical stimulation (FES) cycling with seven paraplegic patients was started at the beginning of 2003. Even at the beginning of the study, and without training, these patients were able to drive distances of 0.5-1.6 km. To stimulate cardiovascular adaptation processes in the case of FES ergometer training or to cover useful distances in the case of FES cycling, a minimum amount of generated mechanical output power is required, which as a rule cannot be achieved yet. In this study, we point out two particular aspects of FES cycling, which impair power output: prolonged fatigue mode and viscous joint friction of the paraplegic FES cyclist. We discuss current possibilities for increasing output power and endurance.     

Optokinetic stimulation in microgravity: torsional eye movements and subjective visual vertical

INTRODUCTION: Microgravity provides unique sensory inputs to the vestibular and oculomotor systems. We sought to determine the effects of long-term spaceflight on sensing of spatial orientation. METHODS: Two cosmonauts participated in experiments on human vestibulo-visual interactions during a long-term mission (178 d) in the MIR station in 1995. During circular optokinetic stimulation (OKS) the tonic torsional eye position (torsional beating field, TBF) and the subjective visual vertical (SVV) were recorded on several days of the space mission as well as pre- and post-flight. A reference data set was obtained from healthy subjects on Earth, in whom the TBF was measured in upright and in prone positions. RESULTS: Neither cosmonaut showed changes in the SVV or the TBF values during the first days in microgravity. On flight day 149, cosmonaut A showed an increase of both values, which continued to rise by 4- and 10-fold until the end of the flight (TBF: 8.1 degrees; SVV: 216.8 degrees). This cosmonaut reported that the increase was accompanied by a loss of spatial orientation. In contrast, cosmonaut B's values remained at pre-flight levels (TBF: 1.6 degrees; SVV: 4.4 degrees). Post-flight values of the TBF did not significantly differ from pre-flight values for either cosmonaut. Subjects showed an increase of the TBF by more than a factor of 2 in prone position (range -7.7 degrees to +10.2 degrees) compared with upright position (range -3.7 degrees to +3.4 degrees). CONCLUSIONS: Pre-flight, post-flight and during the first part of the flight, both cosmonauts exhibited values similar to those of normal subjects in an upright position. The increased TBF values of cosmonaut A from flight day 110 on were within the range of the normal subjects in prone (face-down) position, when the gravity vector cannot be used to stabilize the TBF against the rotating stimulus (the axis of rotation is parallel to the gravity vector). The increasing deviations of cosmonaut A's SVV values in-flight suggest the presence of an internal body reference system, which weakened throughout the flight and thus lost its stabilizing effect.     

Functional output improvement in FES cycling by means of forced smooth pedaling

PURPOSE: Investigation of the influence of forced smooth and normal (nonsmooth) pedaling on the functional output of outdoor functional neuromuscular electrical stimulation (FES)-propelled cycling of spinal cord-injured subjects. SUBJECTS: Twelve subjects with complete spinal cord injury (T4-T12) and limited previous FES training. METHOD: Each subject participated in two separate outdoor sessions: once while pedaling a tricycle in a fixed gear, and a second time while free pedaling the same tricycle; both times with FES. Data on distance covered until exhaustion, cadence, and pedal forces were collected. Energy balance calculations led to evaluations of jerk loss and joint-related concentric/eccentric work. RESULTS: First-trial and total session distances were 68 and 103% longer, respectively, in the forced smooth cycling session than in the free cycling session (P < 0.001). Significantly more additional crank work (accompanied by increased concentric work production) was generated in nonsteady cycling phases to overcome increased jerk losses during free than during fixed-gear pedaling. During fixed-gear pedaling, timing and joint location of muscle work generation were more similar to the cycling of able-bodied subjects than during freewheel pedaling, because most work was generated by knee extensors in the power phase during the former pedaling mode. CONCLUSIONS: The superiority of forced smooth cycling to free cycling, as regards functional output distance, is based on less energy expenditure (less jerk loss and muscle tension) and on more efficient production of energy (more efficient timing and joint location of work production). Some energetic mechanisms that are advantageous for fixed-gear cycling act predominantly in unsteady phases; others work continuously during all phases of cycling.