Biomedical subjects

H E Veeger

Publications and source records attributed to H E Veeger.

14 recordsLinked to original sources

PubMed1992

Differences in performance between trained and untrained subjects during a 30-s sprint test in a wheelchair ergometer.

To compare physiological responses and propulsion technique of able bodied subjects with no prior experience of wheelchairs (AB) and wheelchair dependent subjects (WD), ten AB and nine WD performed a 30-s sprint test in a wheelchair ergometer. The WD had spinal cord injuries with a lesion at T8 or lower. The WD and AB did not show significantly different physiological responses. The power values averaged for the right wheel over the 30 s of the test were 50.2 (SD 14.7) W and 48.0 (SD 4.4) W for WD and AB, respectively. No significant differences in torque application could be discerned, although WD subjects seemed to have a more flattened torque curve with a smaller negative deflection at the beginning of the push. The WD applied a significantly higher horizontal propulsive force to the handrims but did not apply force more effectively. The percentages of effective force to total propulsive force were 61 (SD 16)% for WD and 57 (SD 4)% for AB. With regard to the kinematic parameters, AB followed the handrims significantly longer than WD (end angle AB 65 degrees, WD 44 degrees), started the push phase with their arms more in retroflexion and flexed their trunks further forward. The AB did however show a movement pattern comparable to that of wheelchair athletes measured in a comparable experiment. It could not be decided conclusively that inexperience in wheelchair propulsion led to a less effective propulsion technique. Despite the selection of WD with respect to lesion level, interindividual differences in terms of level of training may have been responsible for the absence of significant results.

Adolescent↗

PubMed1992

Geometry parameters for musculoskeletal modelling of the shoulder system.

A dynamical finite-element model of the shoulder mechanism consisting of thorax, clavicula, scapula and humerus is outlined. The parameters needed for the model are obtained in a cadaver experiment consisting of both shoulders of seven cadavers. In this paper, in particular, the derivation of geometry parameters from the measurement data is described. The results for one cadaver are presented as a typical example. Morphological structures are modelled as geometrical forms. Parameters describing this form are estimated from 3-D position coordinates of a large number of datapoints on the morphological structure, using a least-squares criterion. Muscle and ligament attachments are represented as a plane or as a (curved) line. Muscle paths are determined by a geometrical form of the bony contour around which the muscle is wrapped. Muscle architecture is determined by the distribution of muscle bundles over the attachment area, mapping the distribution of the origin to the insertion. Joint rotation centers are derived from articular surfaces. Hence, muscle moment arms can be calculated. The result of this study is a set of parameters for each cadaver, describing very precisely the geometry of the shoulder mechanism. This set allows positioning of muscle force vectors a posteriori, and recalculation of position coordinates and moment arms for any position of the shoulder.

Acceleration↗

PubMed1992

Effect of handrim velocity on mechanical efficiency in wheelchair propulsion.

To study the effect of tangential speed of the handrims independent of external power output on gross mechanical efficiency (ME), nine able-bodied subjects performed wheelchair exercise tests on a stationary ergometer. The ergometer allowed for measurement of torque and three-dimensional forces on the rims and tangential velocity of the rear wheels. The experiment comprised two series of submaximal tests against constant external power outputs (0.25 and 0.50 W.kg-1) and four wheelchair speeds (0.83, 1.11, 1.39, and 1.67 m.s-1), which simulated a wheelchair speed of 1.67 m.s-1 and mechanical advantages of 0.43-0.87. ME stayed below 10.5% and changed inversely with speed of movement of the handrims. Peak torques on the right handrim stayed even with speed, leading to a significant increase in peak power output. Energy losses owing to braking torques at the beginning and end of the push phase increased with handrim speed but hardly exceeded 5 W. The effective force component applied to the handrims was below 71% of the magnitude of the total force vector and dropped up to 13% with increasing handrim speed. It is suggested that an ineffective direction of forces on the rims might (partly) be responsible for the low ME and for a decrease in ME in relation to tangential handrim velocity. This suggestion is discussed from a number of theoretical perspectives. It is concluded that the use of handrims with a lower mechanical advantage will increase wheelchair propulsion efficiency.

Adult↗

PubMed1992

A computerized wheelchair ergometer. Results of a comparison study.

To determine the validity of propulsion simulation on a stationary wheelchair ergometer, nine male able-bodied subjects performed submaximal exercise tests on the ergometer and on a motor driven treadmill (MDT). Oxygen uptake, ventilation and stroke parameters were equal for both devices, but heart rate was lower and trunk movement was less for the ergometer test. Analysis of forces and power output on the ergometer indicated that power output was equal for both wheels. The ratio between applied forces and the effectively directed force component was approximately 80%. Also a small torque was applied by the hand onto the handrim surface which contributed to the total propulsion torque around the axle. It is concluded that the ergometer is capable of simulation of wheelchair propulsion, although the different trunk motion may necessitate sufficient wheelchair propulsion experience. Force analysis results are discussed.

Biomechanical Phenomena↗

PubMed1991

Inertia and muscle contraction parameters for musculoskeletal modelling of the shoulder mechanism.

To develop a musculoskeletal model of the shoulder mechanism, both shoulders of seven cadavers were measured to obtain a complete set of parameters. Using antropometric measurements, the mass and rotational inertia of segments were estimated, followed by three-dimensional measurements of all morphological structures relevant for modelling, i.e. muscle origins and insertions, muscle bundle directions, ligament attachments and articular surfaces; all in relation to selected bony landmarks. Subsequently, muscle contraction parameters as muscle mass and physiological cross-sectional area were measured. The method of data collection and the results for inertia and muscle contraction parameters as prerequisities for modelling are described.

Aged↗

PubMed1991

Peak oxygen uptake and maximal power output of Olympic wheelchair-dependent athletes.

To extend the existing data base on the cardiovascular capacity of wheelchair-dependent athletes, a maximum wheelchair exercise test was conducted by 48 athletes (8 females and 40 males) on a motor driven treadmill. Athletes were selected on availability from the representatives of eight different disciplines. For 36 subjects maximal external power was calculated on the basis of a separate drag test. Maximal oxygen uptake (VO2max) for the male population was 2.23 l.min-1 (32.9 ml.kg-1.min-1). Subjects were divided into functional categories according to the International Stoke Mandeville Classification, with one nonambulatory, nonparaplegic group classified as "LA." The LA group displayed the highest values while the class IC tetraplegic showed the lowest performance level. Classified over sports disciplines, male track and field representatives showed the highest VO2max (2.86 l.min-1, 44.9 ml.kg-1.min-1) and target shooting athletes the lowest (1.32 l.min-1, 16.3 ml.kg-2.min-1). Maximal power output was on average 81.1 W for the male population and varied from 65.8 W for class II athletes to 92.2 W for class LA. Between sports values ranged from 96.8 W for basketball players to 48.2 W for the archery representative. These data are useful for setting standards for maximally attainable performance levels in relation to sport, functional classification, or sex and underline the capability of the wheelchair-dependent to improve cardiovascular fitness.

Adult↗

PubMed1991

Within-cycle characteristics of the wheelchair push in sprinting on a wheelchair ergometer.

To investigate power output and torque production in wheelchair sprinting, six able-bodied subjects performed nine 20-s sprint tests on a stationary wheelchair ergometer (load 0-8 kg). Ergometer data were analyzed and combined with kinematic data and surface electromyography. Of all power and torque parameters investigated, only maximal power output was independent of load (mean peak value 375 W, one-sided). Mean power output is suggested to be a useful indicator for anaerobic power production, but test conditions concerned speed in relation to handrim diameter should be specified. The relevance of the "mechanical constraint principle" for handrim propulsion is discussed. Within one cycle, power and torque curves showed a negative deflection at the beginning and a valley approximately halfway through the push phase. The relation of these phenomena to kinematic parameters and muscle activity is discussed.

Acceleration↗

PubMed1990

Computer-controlled wheelchair ergometer.

A new wheelchair ergometer has been designed in which a combination of realistic simulation of wheelchair propulsion--with adjustable parameters for rolling resistance, air drag, wind speed and slope--and force measurement has been realised. The static solution enables the measurement of physiological and kinesiological parameters. All data from force transducers in seat and backrest, torque transducers in the wheels and force transducers in the wheelframes as well as the acquired speed are sampled in a data-acquisition system. An offline curve processor allows the acquired data to be processed with standard or custom-programmed routines. Preliminary results have been added and are discussed.

Engineering↗

PubMed1989

Optimum cycle frequencies in hand-rim wheelchair propulsion. Wheelchair propulsion technique.

To study the effect of different cycle frequencies on cardio-respiratory responses and propulsion technique in hand-rim wheelchair propulsion, experienced wheelchair sportsmen (WS group; n = 6) and non-wheelchair users (NW group; n = 6) performed wheelchair exercise tests on a motor-driven treadmill. The WS group wheeled at velocities of 0.55, 0.83, 1.11 and 1.39 m.s-1 and a slope of 2 degrees. The NW group wheeled at 0.83, 1.11 and 1.39 m.s-1 and a 1 degree slope. In each test, a 3-min period at a freely chosen cycle frequency (FCF: 100%) was followed by four 3-min blocks of paced cycle frequencies at 60%, 80%, 120% and 140% FCF. Effects of both cycle frequency and velocity on physiological and propulsion technique parameters were studied. Analysis of variance showed a significant effect (p less than 0.05) of cycle frequency on oxygen cost and gross mechanical efficiency in both the WS and NW group. This indicated the existence of an optimum cycle frequency which is close to the FCF at any given velocity. The optimum cycle frequency increased with velocity from 0.67 to 1.03 cps over the range studied (p less than 0.05). Oxygen cost was approximately 10% less at 100% FCF than at 60% or 140% FCF. Gross mechanical efficiency for the WS group at 100% FCF was 8.5%, 9.7%, 10.4% and 10.1%, respectively, at the four velocities.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

Wheelchair propulsion technique at different speeds.

To study wheelchair propulsion technique at different speeds, five well-trained subjects propelled a wheelchair on a treadmill. Measurements were made at four belt speeds of 0.56-1.39 m/s and against slopes of 2 and 3 degrees. Cardiorespiratory data were collected. Three consecutive strokes were filmed. Using markers on subject, wheelchair and treadmill frame a kinematic analysis was performed. Considerable inter-individual differences in propulsion style were found, but also general changes relative to speed occurred in the group as a whole. Cycle time decreased with speed, predominantly as the result of a shorter push time while push angle remained constant and the movement ranges of trunk and arms shifted with speed. It is concluded that despite different propulsion styles, general and continuous adaptations to speed changes occurred, mainly by flexion of the trunk and arms.

Acceleration↗

PubMed1988

Manual wheelchair propulsion: effects of power output on physiology and technique.

Eight wheelchair sportsmen conducted eight wheelchair exercise tests on a treadmill. Two workload strategies were followed: strategy 1--increments in speed at a constant slope and strategy 2--increments in slope at constant velocity. Thus, data on cardio-respiratory and propulsion technique parameters were obtained on two identical series of 16 speed and slope combinations. Between each two identical speed and slope combinations of strategies 1 and 2, a different workload history is apparent. A four-factor analysis of variance with repeated measures on the factors "strategy" (workload history), "speed," and "slope" was applied (P less than 0.05). No "strategy" effect was seen in the cardio-respiratory parameters (gross mechanical efficiency, ventilation, oxygen consumption, and heart rate), work/cycle, and cycle time. Thus, within the experimental set-up, workload history did not affect the parameters studied and 3-min workload periods appeared sufficiently long for experienced wheelchair users to adapt to the requirements of a given speed and slope combination. Significant effects were found on "speed," "slope," and their interaction in all parameters tested. Moreover, a comparison of two equal levels of power output, but different speed and slope, led to a significantly higher efficiency, cycle time, and work per cycle for the "low speed and high slope" combination. Push time and recovery time appeared highly dependent on speed and slope, respectively. The findings indicate that propulsion technique and cardio-respiratory parameters should not merely be studied in relation to power output, but also with respect to its constituents, speed, and slope/resistance.

Adult↗

PubMed1988

Wheelchair racing: effects of rim diameter and speed on physiology and technique.

Effects of different hand rim diameters in wheelchair racing were studied with respect to physiological and technique parameters at five speed levels (N = 8 wheelchair sportsmen). In each of five subsequent 15-min exercise tests on a treadmill, a different sized hand rim was mounted to the rear wheels (0.3, 0.35, 0.38, 0.47, 0.56 m). In each test, speed increased with 0.83 m.s-1 every 3 min, starting at 0.83 m.s-1 and ranging up to 4.17 m.s-1 (slope: 0.5 degrees). Cardiorespiratory responses (ventilation, oxygen cost, heart rate, respiratory exchange ratio, mechanical efficiency) and timing data (cycle time, push time, recovery time, push angle, and work per cycle) were obtained every 3rd min, together with the movement pattern of trunk and arm segments. Clear effects of rim diameter and speed were seen for the physiological parameters (P less than 0.05). In physiological terms, D5 appeared the least beneficial, followed by D4. Moreover, increasing rim diameter had a significant effect on movement pattern of the upper arm in the sagittal as well the frontal plane of motion. However, no timing effects were seen with changing rim diameter. On the other hand, timing parameters varied markedly with speed, whereas the segmental excursions of the upper limb did not show a "speed-effect". In general, small hand rims show lower cardiorespiratory responses. This may be related to the decreased segmental excursions of the upper limb and the lower linear hand velocity. Together with a low rolling and air drag, heart rate, and oxygen cost, these are important prerequisites in racing events.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1984

Role of mono- and biarticular muscles in explosive movements.

From 24 vertical jumps (eight subjects, three jumps each), calculations of forces, torques, and power per joint were combined with EMG data of eight leg muscles and with estimations of their contraction velocities. In the second part of the push-off, a high power output of 3000-4000 W was delivered in the ankle joints during plantar flexion. This is attributed to a sequential energy flow from hip to knee and ankle joints. Through coordinated actions of both the m. gluteus maximus and the m. rectus femoris as well as the m. vastus med., intermedius and lat. (mm. vasti) and the m. gastrocnemius, power delivered by the monoarticular extensors of the hip and knee joints was transported distally via the biarticular muscles to the ankle joints. During the high plantar flexion velocity at the end of the push-off, hip and knee joints showed high extension velocities resulting in relatively low contraction velocities for the biarticular muscles. As a consequence they could deliver high forces, which allowed them to transport energy in a proximodistal direction and allowed them to decelerate the angular velocities of the hip and knee joints without losses due to eccentric contractions. It is concluded that this power transport is essential in the execution of explosive movements.

Ankle Joint↗

PubMedDate not supplied

Propulsion technique in hand rim wheelchair ambulation.

Six male subjects took part in a pilot study on a stationary wheelchair ergometer. They propelled the ergometer at a speed of 0.55, 0.83, 1.11 and 1.39 m/s. The speed increased every 3 min. Inertia and friction force were adjusted proportional to body weight. Every third minute 750 samples of the torque and velocity signals were digitized at a sampling rate of 100 Hz. From the signals mean external power output (Pmean), peak power (Ppeak), mean torque (Mmean) and peak torque (Mpeak), work/cycle, 'time-to-peak torque' (TTP), cycle duration (CT), push time (PT) and recovery time (RT) were determined in relation to mean velocity (speed). For the mean velocity range studied, analysis of variance (P less than 0.05) revealed significant increments in Ppeak, Mpeak, Pmean, Mmean and work/cycle with increasing mean velocity, whereas CT and PT showed a significant decrease. TTP showed a decrease with speed which, however, was not statistically significant. The RT showed no significant variation as well. Our previous research into propulsion techniques mainly focused on movement frequency and timing and was conducted during wheelchair ambulation on a motor driven treadmill. Despite considerable interindividual variation in terms of movement pattern, current and previous studies showed similar trends in the timing pattern (cycle, push, recovery duration) with respect to speed. Theoretical considerations regarding variations in peak torque and work/cycle with respect to velocity are supported by the current results. Both torque and work/cycle are important technique parameters and of relevance in speed regulation. The data also suggest that wheelchair ambulation can be validly simulated and studied with the special purpose wheelchair ergometer.(ABSTRACT TRUNCATED AT 250 WORDS)

Ergonomics↗