Paul Willems

Lower extremity muscle strength is reduced in people with type 2 diabetes, with and without polyneuropathy, and is associated with impaired mobility and reduced quality of life

AIM The purpose of the present study was to distinguish the effects of both diabetes mellitus type 2 (DM2) and diabetic polyneuropathy (DPN) on mobility, muscle strength and health related quality of life (HR-QoL). METHODS DPN patients (n=98), DM2 patients without DPN (DC) (n=39) and healthy subjects (HC) (n=19) performed isometric and isokinetic lower limb muscle strength tests. Mobility was determined by a timed up and go test (TUGT), a 6 min walk test and the physical activity scale for the elderly questionnaire. HR-QoL was determined by the SF36 questionnaire. RESULTS DPN patients had moderate polyneuropathy. In both DPN and DC patients leg muscle strength was reduced by 30-50% compared to HC. Muscle strength was correlated with mobility tests, and reduced muscle strength as well as impaired mobility were associated with a loss of HR-Qol (all p<0.05). We did not observe major differences in muscle strength, mobility (except for the TUGT, p<0.01) and HR-QoL between diabetic patients with and without DPN. CONCLUSION DM2 patients, with and without DPN, have decreased maximal muscle strength in the lower limbs and impaired mobility. These abnormalities are associated with a loss of HR-QoL. The additional effect of moderate DPN was small in our patients.

Control of rapid aimed hand movements : The one-target advantage

A series of 8 experiments examined the phenomenon that a rapid aimed hand movement is executed faster when it is performed as a single, isolated movement than when it is followed by a second movement (the 1-target advantage). Three new accounts of this effect are proposed and tested: the eye movement hypothesis, the target uncertainty hypothesis, and the movement integration hypothesis. Data are reported that corroborate the 3rd hypothesis, but not the first 2 hypotheses. According to the movement integration hypothesis, the first movement in a series is slowed because control of the second movement may overlap with execution of the first. It is shown that manipulations of target size and movement direction mediate this process and determine the presence and absence of the 1-target advantage. Possible neurophysiological mechanisms and implications for motor control theory are discussed.

Social influence and selection effects in the context of smoking behavior: changes during early and mid adolescence.

OBJECTIVE This article examined the contribution of selection and influence processes in smoking behavior similarity among friends, and changes in these processes during early and mid adolescence. DESIGN Data from 1886 Dutch high school students in the control group of the European Smoking prevention Framework Approach (ESFA) study were used. Changes in selection and influence were examined during three successive waves using structural equation modeling. MAIN OUTCOME MEASURES Smoking behavior of adolescents, best friends, parents, and siblings. RESULTS Most support was found for selection of reciprocal (p(wave1,2,3) < 0.01) and nonreciprocal friends (p(wave1,2) < 0.01; p(wave3) = 0.25), although these effects decreased over time. Support for influence was only found among nonreciprocal (desired) friends during the last wave (p(wave3) < 0.01). Adolescents were influenced by their parents (p(wave2) < 0.01; p(wave1,3) > 0.05) and siblings (p(wave1,2) < 0.01; p(wave3) = 0.16), but influence diminished over time. CONCLUSION Smoking-based selection processes decreased over time while the influence of friends increased. Smoking prevention programs should focus on the structure of peer environments besides promoting social influence skills. During early adolescence parents and siblings should be targeted, while during mid adolescence, the focus should shift toward the adolescents and their dynamic peer environment.

Looking good. BMI, attractiveness bias and visual attention

The aim of this study was to study attentional bias when viewing ones own and a control body, and to relate this bias to body-weight and attractiveness ratings. Participants were 51 normal-weight female students with an unrestrained eating style. They were successively shown pictures of their own and a control body for 30s each, while their eye movements (overt attention) were being measured. Afterwards, participants were asked to identify the most attractive and most unattractive body part of both their own and a control body. The results show that with increasing BMI and where an individual has given a relatively low rating of attractiveness to their own body, participants attended relatively more to their self-identified most unattractive body part and the control bodys most attractive body part. This increasingly negative bias in visual attention for bodies may maintain and/or exacerbate body dissatisfaction.

Differences in Walking Pattern during 6-Min Walk Test between Patients with COPD and Healthy Subjects

Background To date, detailed analyses of walking patterns using accelerometers during the 6-min walk test (6MWT) have not been performed in patients with chronic obstructive pulmonary disease (COPD). Therefore, it remains unclear whether and to what extent COPD patients have an altered walking pattern during the 6MWT compared to healthy elderly subjects. Methodology/Principal Findings 79 COPD patients and 24 healthy elderly subjects performed the 6MWT wearing an accelerometer attached to the trunk. The accelerometer features (walking intensity, cadence, and walking variability) and subject characteristics were assessed and compared between groups. Moreover, associations were sought with 6-min walk distance (6MWD) using multiple ordinary least squares (OLS) regression models. COPD patients walked with a significantly lower walking intensity, lower cadence and increased walking variability compared to healthy subjects. Walking intensity and height were the only two significant determinants of 6MWD in healthy subjects, explaining 85% of the variance in 6MWD. In COPD patients also age, cadence, walking variability measures and their interactions were included were significant determinants of 6MWD (total variance in 6MWD explained: 88%). Conclusions/Significance COPD patients have an altered walking pattern during 6MWT compared to healthy subjects. These differences in walking pattern partially explain the lower 6MWD in patients with COPD.

Redistribution of joint moments is associated with changed plantar pressure in diabetic polyneuropathy

BackgroundPatients with diabetic polyneuropathy (DPN) are often confronted with ulceration of foot soles. Increased plantar pressure under the forefoot has been identified as a major risk factor for ulceration. This study sets out to test the hypothesis that changes in gait characteristics induced by DPN related muscle weakness are the origin of the elevated plantar pressures.MethodsThree groups of subjects participated: people diagnosed with diabetes without polyneuropathy (DC), people diagnosed with diabetic polyneuropathy (DPN) and healthy, age-matched controls (HC). In all subjects isometric strength of plantar and dorsal flexors was assessed. Moreover, joint moments at ankle, knee and hip joints were determined while walking barefoot at a velocity of 1.4 m/s. Simultaneously plantar pressure patterns were measured.ResultsCompared to HC-subjects, DPN-participants walked with a significantly increased internal plantar flexor moment at the first half of the stance phase. Also in DPN-subjects the maximal braking and propelling force applied to the floor was decreased. Moreover, in DPN-subjects the ratio of forefoot-to-rear foot plantar pressures was increased. Body-mass normalized strength of dorsal flexors showed a trend to be reduced in people with diabetes, both DC and DPN, compared to HC-subjects. Plantar flexors tended to be less weak in DC compared to HC and in DPN relative to DC.ConclusionThe results of this study suggest that adverse plantar pressure patterns are associated with redistribution of joint moments, and a consequent reduced capacity to control forward velocity at heel strike.

Calculation of plantar pressure time integral, an alternative approach.

In plantar pressure measurement, both peak pressure and pressure time integral are used as variables to assess plantar loading. However, pressure time integral shows a high concordance with peak pressure. Many researchers and clinicians use Novel software (Novel GmbH Inc., Munich, Germany) that calculates this variable as the summation of the products of peak pressure and duration per time sample, which is not a genuine integral of pressure over time. Therefore, an alternative calculation method was introduced. The aim of this study was to explore the relevance of this alternative method, in different populations. Plantar pressure variables were measured in 76 people with diabetic polyneuropathy, 33 diabetic controls without polyneuropathy and 19 healthy subjects. Peak pressure and pressure time integral were obtained using Novel software. The quotient of the genuine force time integral over contact area was obtained as the alternative pressure time integral calculation. This new alternative method correlated less with peak pressure than the pressure time integral as calculated by Novel. The two methods differed significantly and these differences varied between the foot sole areas and between groups. The largest differences were found under the metatarsal heads in the group with diabetic polyneuropathy. From a theoretical perspective, the alternative approach provides a more valid calculation of the pressure time integral. In addition, this study showed that the alternative calculation is of added value, along peak pressure calculation, to interpret adapted plantar pressures patterns in particular in patients at risk for foot ulceration.

Muscles limiting the sit-to-stand movement: an experimental simulation of muscle weakness.

Adapted strategies in rising from a chair occur with muscle weakness. To assess whether muscle weakness caused the strategy change, an experimental simulation was performed that allowed to investigate separately effects of reduced muscle capacity and of strategy change on movement dynamics. It was hypothesized that a sit-to-stand (STS) strategy change spares muscles that become overloaded when muscle weakness develops. Ten healthy females participated; seven of them completed all tests. Muscle weakness causes an increased load-over-capacity ratio. In the present study, this ratio was increased by providing participants with a waist-coat containing 45% of their body mass. Participants performed sit-to-stand manoeuvres with and without added mass; moreover they were instructed to perform two different strategies, the moment-transfer-strategy and the stabilization-strategy. During these STS-tasks sagital 2D-video analysis were made and ground reaction forces (GRF) were measured. Joint moments and powers for ankle, knee and hip joint were calculated. The preferred strategy under the normal condition was the moment-transfer strategy. Increasing the load without adapting the strategy resulted in significantly higher (13%) knee-joint extension moments. Allowing a strategy shift in the loaded condition spared the knee-joint extensors (-6%) and transferred effort to hip-joint extensors (57%) and plantar flexor (67%) muscles. These results suggest that the capacity of knee-joint extensors limits the STS-performance when muscle weakness occurs.

The influence of stride-length on plantar foot-pressures and joint moments.

PURPOSE Joint moments have been acknowledged as key factors in understanding gait abnormalities. Gait velocity is further known to affect joint moments and foot pressures. Keeping gait velocity constant is thus a strategy to cancel out the influence of different preferred gait speed between groups. But even if gait velocity is controlled, individuals can choose different stride length-stride frequency combinations to cope with an imposed gait velocity. SCOPE To understand the influence of stride frequency-stride length on joint moments and plantar pressures. METHODS Twenty healthy young adults had to cross an 8m walkway with a walking speed of 1.3ms(-1). The wooden walkway was equipped with a force and a pressure platform. While walking speed was kept constant each participant walked with five different imposed stride lengths (SL): preferred (SL0); with a decrease of 10% (SL-10); with a decrease of 20% (SL-20); with an increase of 10% (SL+10) and with an increase of 20% (SF+20). RESULTS Ankle and knee joint moments significantly decreased with a decrease in SL. A significant (p<.05) lower peak pressure was achieved with a decreased SL under the heel, toes and midfoot. DISCUSSION/CONCLUSION The results showed that a change in stride lengths alters both, joint moments and foot pressures with clinically interesting indications. Redistribution of joint moments in the elderly for example might rather result from decreased SL than from age.

A highly radiopaque vertebroplasty cement using tetraiodinated o-carborane additive

Bone cements for vertebroplasty must have a much better radiocontrast level than cements for knee or hip arthroplasty. This is generally accomplished by adding a relatively large portion of BaSO(4), although this affects the physical-mechanical and biological properties of the cement. This prompted us to develop an alternative radiopaque cement, on the basis of unique highly radiopaque methacrylic microspheres. These contain iodine in two modalities: (i) covalently linked to the methacrylic polymer, and (ii) as constituent of the stable tetraiodocarborane 8,9,10,12-I(4)-1,2-closo-C(2)B(10)H(8). The total iodine content in these particles exceeded 30% by mass. These radiopaque microspheres as well as the cement made thereof were characterized extensively, e.g., by scanning electron microscopy, X-ray contrast measurements, X-ray photoelectron spectroscopy, measurements of compressive strength, infrared spectroscopy, and solid state (11)B{(1)H} NMR spectroscopy. Furthermore, the new cement was subjected to several biocompatibility tests in vitro. The results show that the new bone cement fulfills all physico-chemical criteria for use in vertebroplasty. Further data on the cements biocompatibility (in vitro), as well as on the handling parameters and doughviscosity, indicate that this material has a potential to become an alternative to vertebroplasty cements with a high BaSO(4) content. The new cement provides two significant advantages: (i) controlled viscosity in the dough phase, which facilitates precise injection during the vertebroplasty procedure; (ii) excellent structural stability, which precludes leaching of contrast post-implantation.