Biomedical subjects

H E Veeger

Publications and source records attributed to H E Veeger.

31 records · Page 2Linked to original sources

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

Handcycling: different modes and gear ratios.

Handrim wheelchair propulsion is a straining form of ambulation. In contrast, arm crank exercise in laboratory settings has shown a higher degree of gross mechanical efficiency and increased levels of peak power output. Moreover, arm crank exercise can be conducted at different gear ratios and in asynchronic or synchronic mode. Although tricycle crank exercise or handcycling has become increasingly popular for recreational use, sports and outdoor wheeling over the last decade, today little is known about the cardiopulmonary strain in handcycling. The physiological and subjective responses during handcycling were evaluated in a group of 12 male non-wheelchair users (age 24.6 +/- 2.7 yr; body weight 73.7 +/- 9.7 kg). During an incremental submaximal exercise test on a motor driven treadmill (velocity: 1.8 ms-1; an incremental slope of 1% per 3 min; 0-3%; mean power output of the subject group varied between 7.6 +/- 1.6 W and 47.5 +/- 6.2 W), effects of asynchronic and synchronic crank settings and three different gear ratios (1:0.42, 1:0.59, 1:0.74 (or 24, 36 and 44 rpm)) were evaluated in a random testing sequence. Significantly lower levels of mean oxygen uptake, ventilation, relative heart rate and oxygen uptake were seen during synchronic arm use and for the lighter gear ratios (i.e. higher movement frequency; 44 rpm). Subjective local perceived discomfort showed similar trends. Conversely, gross mechanical efficiency appeared higher for these conditions. The need for strong medio-lateral stabilizing muscle effort during asynchronic arm use (to ensure a proper wheeling direction as well as simultaneous power transfer to the cranks) and the effective use of the trunk in this subject group may explain the advantage of synchronic arm use. Whether this advantage is consolidated among wheelchair confined individuals needs further study. Apart from the important effects of a shift in force--velocity characteristics of the contracting muscles with varying gear ratios, increased static finger flexor and arm muscle activity may explain the increased strain in the somewhat unnatural heavy gear condition (24 rpm) at the studied velocity. Results need to be re-evaluated for wheelchair user populations and different higher velocities and power conditions. Moreover, other aspects of the wheelchair--user interface must be studied in order to generate optimum fitting and design guidelines for different user groups and conditions of use.

Adult↗

PubMedDate not supplied

Anaerobic work capacity in elite wheelchair athletes.

To study the anaerobic work capacity in wheelchair athletes, 67 elite wheelchair athletes (50 male) were studied in a 30-second sprint test on a computer-controlled wheelchair ergometer during the World Championships and Games for the Disabled in Assen (1990). The experimental set-up (ergometer, protocol) proved to be adequate in terms of power output (P30, P5) velocity and heart rate. Male and female athletes were comparable with respect to personal characteristics (age, body weight, training hours). Track athletes (classified in 4 different functional classes) showed a class-related mean power output (P30: mean power produced during the 30-second sprint period) of 23, 68, 100, and 138 W for the male athletes (n = 38) and 38, 77, and 76 W for females in the upper three classes (n = 10). Sprint power was low for the group of subjects with cerebral palsy (35 W; mixed, n = 6) and relatively high for the amputee group (121 W; mixed, n = 6), female basketball players (81 W; n = 5), and two male field athletes (110 W). Significant differences between male and female athletes were found for P30 and P5 (highest mean power output over any of the six 5-second periods). As was to be expected, mean maximum heart rate in the sprint test varied significantly between the track groups from 112 (high lesion group) to 171 beats/minute(-1) (low lesion group) but not for both genders. The lower P30 in the T1 and T2 groups must be explained not only by the reduced functional muscle mass and impaired coordination but also by phenomena of cardiovascular dysfunction. Based on the performance parameters, the functional classification of the track athletes into four groups seems adequate. P30 was significantly associated with the personal characteristics of gender and hours of training. A significant correlation was found between P30 and sprint performance times for 200 meters (r = -0.79). No correlation was found between either of the forms of power output and the marathon times. Anaerobic wheelchair work capacity can be adequately studied with the 30-second sprint test that was used in this study. Anaerobic work capacity is highly variable among elite wheelchair athletes with different disabilities and from different sports disciplines and appeared quite strongly influenced by functionality, hours of training, and gender.

Adult↗

PubMedDate not supplied

Effectiveness of force application in manual wheelchair propulsion in persons with spinal cord injuries.

The objective of this study was to investigate effectiveness of force application, the ratio power output/energy expenditure, and timing parameters of wheelchair propulsion in persons with tetraplegia (TP, n=17) and paraplegia (PP, n=12), at two different intensity conditions. All subjects performed a maximal exercise test on a wheelchair ergometer. Exercise bouts with an intensity of 30 to 50% and 60 to 80% of the maximal power output were analyzed. Effectiveness of force application, defined as the ratio of the effective force and the total force, was considerably lower in TP, compared with PP. Effectiveness of force application in the plane of the wheel was comparable between TP and PP. TP showed a significantly lower effectiveness of force application in the frontal plane and applied the forces in a more lateromedial direction to the hand rim. The ratio power output/energy expenditure, calculated as an indication of gross mechanical efficiency, was considerably lower in TP and was associated with the effectiveness of force application (r=0.64; P < 0.01). Timing parameters showed that TP positioned their hands in a more backward position on the hand rim. Comparing the different intensity conditions revealed that force was applied more effectively, and the ratio power output/energy expenditure was higher at the higher intensity condition. Push time, relative to cycle time, increased, and beginning angle showed a forward shift with a higher load. TP tended to decrease, whereas PP showed a tendency for an increase in stroke angle with a higher load. The low effectiveness and different pattern of force application in TP should be taken into account when developing other wheelchair propelling mechanisms and training programs for this population.

Adult↗

PubMedDate not supplied

Propulsion technique and anaerobic work capacity in elite wheelchair athletes: cross-sectional analysis.

Wheelchair sports and daily manual wheelchair propulsion are dominated by frequent short-term power demands. The purpose of the current cross-sectional study was to determine the variation in propulsion technique in association with sprint power production among elite wheelchair athletes. Therefore, 67 wheelchair athletes (different impairments; 17 female and 50 male athletes; age, 29.1+/-7 yr; body weight, 60.7+/-11.8 kg; training hours, 12.9+/-6.4 h x wk(-1); VO2 peak, 1.7+/-0.7 liter x min(-1); aerobic power output, 72.2+/-36.7 W) were studied during the World Championships and Games for the Disabled in Assen (1990) on propulsion technique and anaerobic work capacity in a 30-s sprint test on a computer controlled wheelchair ergometer. Mean power output (P30) (97+/-45.8 W; range, 8.3-195.3 W) and heart rate (158.6+/-23.6 b x min(-1)) were highly variable and seemed associated with impairment level: track athletes, classified in four different functional classes, showed a class-related P30 of 23, 68, 100, and 138 W for the male athletes (n=38). Sprint power relative to body weight varied between 0.36 W X kg BW(-1)+/-0.04 and 1.85 W X kg BW(-1)+/-0.43 for the different subject groups. Propulsion technique in terms of forces applied to the rim and timing showed significant differences between subject groups for the majority of parameters studied. Apart from the mediolateral force and the negative dip at the start of the push phase, the technique parameters were significantly related to power production. Fraction effective force, the ratio between the total force vector and the effective force applied to the hand rim, appeared low on average (especially for subjects with cerebral palsy and those with a high spinal lesion) but showed a significant correlation with power output (r=0.5). In general, propulsion technique parameters were related to both performance and functionality. The number of training hours showed a small but significant relation with peak power (r=0.31), peak torque (r=0.4), the amount of work per push (r=0.41) and the total force vector (r=0.31), stressing the role of training status, next to disability, as important mediating factor in both propulsion technique as well as performance capacity. No association between training hours and fraction effective force was seen. It can be concluded that propulsion technique and performance parameters are highly variable among wheelchair athletes. Also, propulsion technique is strongly associated with functionality and training hours and does clearly relate to performance. The current results on technique and performance and their possible causal relationship, but also with impairment and sports discipline, must be further substantiated in a longitudinal study design.

Adult↗

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↗

PubMedDate not supplied

Physiological evaluation of a newly designed lever mechanism for wheelchairs.

Lever-propelled wheelchairs have been described as more efficient and less physically demanding than hand-rim-propelled wheelchairs. To evaluate a newly designed lever mechanism (MARC) in both one- and two-arm use, a series of wheelchair exercise tests were performed on a motor-driven treadmill. Eight able-bodied male subjects performed a standard exercise test in the prototype MARC, both in an asynchronic and a synchronic bimanual propelling mode and in an unilateral (left-sided) mode. Subsequently the subjects performed additional exercise tests in a conventional crank-to-rod lever mechanism with unilateral and bimanual propulsion and in a conventional hand rim wheelchair. Analysis of variance was used to study the effect of the different work modes upon power output and cardiorespiratory parameters statistically (p < 0.05). The MARC stood out well in comparison with the conventional lever design. The additional design features which are to be implemented (variable gearing, reverse gear) will make the MARC a useful wheelchair. One-arm wheelchair propulsion is a very strenuous form of locomotion, requiring careful consideration in terms of provision. Mechanical and ergonomic improvements are quite feasible in lever propulsion and may to a certain extent reduce this problem. To improve overall mobility of wheelchair-dependent subjects further, ergonomic and mechanical design improvements are very necessary in lever as well as hand-rim wheelchairs. A combined biomechanical and physiological research approach will help in the definition of design criteria and fitting guidelines.

Adult↗

PubMedDate not supplied

Physical strain and mechanical efficiency in hubcrank and handrim wheelchair propulsion.

The physical strain and mechanical efficiency of manual wheelchair propulsion using handrim and hubcrank propelled racing wheelchairs were studied during a submaximal wheelchair exercise test on a stationary roller ergometer. Ten healthy male able-bodied subjects conducted two exercise tests in a random order and measurements of phyical strain (oxygen uptake, minute ventilation, respiratory exchange ratio, heart rate) and gross mechanical efficiency were obtained. During the experiment torque data, speed and power output were determined at a sample frequency of 0.1 Hz. Analysis of variance for repeated measures (p < 0.05) was used to establish differences. The hubcrank propulsion mechanism showed a significantly lower physical strain and higher gross mechanical efficiency in comparison with the handrim propulsion mechanism. The lower strain and higher efficiency in propelling the hubcrank partly seems to be due to the continuous biphasic cyclic propulsion movement, which allows both push and pull forces to be exerted. This involves flexor and extensor muscles around elbow and shoulder, leading to a reduced tendency to fatigue in individual muscles in the upper extremity. The more natural and neutral wrist-hand orientation also seems to diminish finger flexor activity and wrist-stabilizing muscle activity, and will thus reduce physical strain both with respect to the cardiorespiratory and musculoskeletal systems. The latter may influence the tendency to develop carpal tunnel problems positively. The reduced strain of the hubcrank propulsion mechanism clearly has a number of advantages over handrims for the human engine in the short and long run. However, technical innovation should address current practical problems of steering and braking. Clearly, hubcranks can be used in low-seated wheelchairs (i.e. racing wheelchairs) only, and in subjects with a sufficiently large range of motion in the upper extremity. Moreover, the increased width is a drawback of hubcranks. Care should be taken while negotiating door posts.

Arm↗