A.P. Hollander

Physical strain in daily life of wheelchair users with spinal cord injuries.

Forty-three men (age 33 +/- 9 yr) with spinal cord injuries (SCI) were observed during a normal workday while heart rate was recorded continuously. Physical strain was estimated using the heart rate response expressed relative to the individual heart rate reserve (%HRR). The mean physical strain during the day for group I (C4-C8, N = 9), II (T1-T5, N = 6), III (T6-T10, N = 15), and IV (T10-L5, N = 13) was 38 +/- 8, 29 +/- 12, 22 +/- 8, and 23 +/- 5%HRR, respectively. Prolonged periods (> 15 min) of high strain (> 60%HRR) that might maintain or improve physical capacity were not identified during activities of daily life (ADL), but only during sports activities. The analysis of activity-related strain revealed that specific ADL such as making transfers, entering/leaving car, and negotiating environmental barriers, provoked high levels of strain, especially in those with quadriplegia. Periods of peak strain (> 60%HRR, < 3 min) occurred frequently, also predominantly in those with quadriplegia. It was concluded that the physical strain during ADL is related to the level of lesion and is not of a magnitude and duration that would maintain or improve physical capacity. The periods of peak strain might restrict the mobility and independence of persons with SCI, and, therefore, reduce their quality of life.

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.

Relationship between physical strain during standardised ADL tasks and physical capacity in men with spinal cord injuries

To describe physical strain during activities of daily living (ADL), 44 men with spinal cord injuries (C4-L5) performed a set of standardised tasks. The physical strain was defined as the highest heart rate response expressed as a percentage of the individual heart rate reserve (%HRR). The physical strain averaged over the subjects who performed all tasks (n = 24) was (mean ± SD): 20.2 ± 7.2 %HRR (washing hands), 20.4 ± 7.3 %HRR (passing a side-hung door), 28.8 ± 10.8 %HRR (transfer to a toilet), 31.2 ± 13.1 %HRR (ascending an 8 cm curb), 33.9 ± 12.0 %HRR (transfer to a shower seat), 35.1 ± 10.5 %HRR (transfer to bed), 36.4 ± 13.3 %HRR (preparing lunch), 37.1 ± 12.0 %HRR (washing up), 38.7 ± 14.9 %HRR (ascending a ramp), 39.8 ± 15.6 %HRR (transfer to a shower wheelchair), 41.4 ± 12.1 %HRR (changing sheets), and 45.9 ± 10.4 %HRR (entering a car). Physical strain could be notably high, but large variations among subjects were present. During all tasks, subjects with tetraplegia had significantly higher levels of strain than subjects with low (T6-L5) lesions. Physical strain was inversely related to parameters of physical capacity: isometric strength (r: -0.34 to -0.72), sprint power (r: —0.34 to -0.69), peak oxygen uptake (r: -0.41 to -0.81) and maximal power output (r: -0.52 to -0.82). Parameters of physical capacity were better predictors of physical strain than was the lesion level, and explained 37-71% of the variance in strain during ADL. It was also concluded that the method used in this study provides a quantitative and objective estimation of physical strain and may therefore be a useful tool to identify task difficulty during rehabilitation and to evaluate the results of task and physical training on the physical strain during ADL.

Physical performance during rehabilitation in persons with spinal cord injuries

PURPOSE The objective of the present study was to evaluate the effect of rehabilitation on physical capacity, mechanical efficiency of manual wheelchair propulsion, and performance of standardized activities of daily living (ADL). METHODS Nineteen recently injured subjects with spinal cord injuries were tested on a wheelchair ergometer (maximal isometric strength, sprint and maximal power output, and peak oxygen uptake) and during standardized ADL (physical strain and performance time) at the beginning (t1) and at the end (t2) of the active rehabilitation period. RESULTS Paired Student t-tests showed significant increases for maximal isometric strength (24%, P < 0.01), sprint power output (l7%, P < 0.001) and maximal power output (38%, P < 0.001). Peak oxygen uptake showed no statistically significant improvement (11%, P = 0.06). Mechanical efficiency of submaximal wheelchair exercise was significantly higher at t2 (9.0%) compared to t1 (7.9%, P < 0.01). No significant differences were found for physical strain during ADL, except for passing a door (P < 0.05). Performance time showed a significant decrease for most tasks. CONCLUSIONS The results of this study show considerable improvements in physical capacity and mechanical efficiency of manual wheelchair propulsion during rehabilitation, and a concomitant lower performance time during standardized ADL. The higher mechanical efficiency and the decrease in performance time during standardized ADL suggest improvement in wheelchair propulsion technique.

Isometric strength, sprint power, and aerobic power in individuals with a spinal cord injury

This study investigated in rather specific wheelchair tests the relationships among estimates of isometric upper-body strength (Fiso), sprint power (P30), aerobic power (VO2peak), and maximal power output (POaer) in a group of 44 men (age 34 +/- 12 yr) with longstanding spinal cord injuries ranging from C4/C5 to L5. Fiso was defined as the maximum force that could be exerted on the blocked rims of a stationary wheelchair ergometer. The estimation of P30 involved the measurement of the mean power during a 30-s all-out sprint test on the same wheelchair ergometer. VO2peak and POaer were determined as the peak oxygen uptake and highest sustained power output during a discontinuous progressive maximal exercise test on a motorized treadmill, while subjects used their own daily use wheelchair. Fiso ranged from 1.5 N.kg-1 (mean of both arms) in the group with quadriplegia to 3.4 N.kg-1 in the group with lowest-lesions, and P30 ranged from 0.5 to 1.5 W.kg-1 among the subjects. VO2peak ranged from 13.6 ml.kg-1.min-1 in the group with quadriplegia to 31.3 ml.kg-1.min-1 in the group with lowest-lesions, and POaer ranged from 0.4 to 1.1 W.kg-1. Strong positive relationships (r = 0.81-0.92) were demonstrated among all variables. Regression equations among variables were calculated: P30 = 0.51 Fiso - 0.18 (R2 = 0.75); POaer = 0.34 Fiso - 0.02 (R2 = 0.66); POaer = 0.67 P30 + 0.11 (R2 = 0.81); VO2peak = 6.52 Fiso + 4.15 (R2 = 0.76); VO2peak = 12.03 P30 + 7.43 (R2 = 0.77); VO2peak = 16.81 POaer + 6.44 (R2 = 0.84).(ABSTRACT TRUNCATED AT 250 WORDS)

Consequence of feedback-based learning of an effective hand rim wheelchair force production on mechanical efficiency

OBJECTIVE Investigation of the effect of visual feedback on effective hand rim wheelchair force production and the subsequent effect on gross mechanical efficiency. DESIGN Ten subjects in an experimental group and 10 subjects in a control group practised three weeks (3.wk(-1), i.e., a pre-test and 8 trials) on a computer-controlled wheelchair ergometer. Every trial consisted of two blocks of 4 min at 0.15 and 0.25 W.kg(-1) at 1.11 m.s(-1). On three trials an additional block at 0.40 W.kg(-1) was performed. The experimental group practised with and the control group practised without visual feedback on the effectiveness of force production. BACKGROUND In mechanical terms, the low gross mechanical efficiency of hand rim wheelchair propulsion may be the result of ineffective force production. METHODS During all trials oxygen uptake, power output, forces and torque on the hand rims were measured. RESULTS In comparison with the control group, the experimental group at trial 8 had a significantly more effective force production compared to the control group (90-97% vs. 79-83%, respectively), but showed a significantly lower mechanical efficiency (5.5-8.5% vs. 5.9-9.9%, respectively). CONCLUSION Findings indicate that the most effective force production from a mechanical point of view is not necessarily the most efficient way--in terms of energy cost-- from a biological point of view and that force direction is based on an optimization of cost and effect. RELEVANCE Learning a more effective force production by visual feedback is not useful for increasing the mechanical efficiency of hand rim wheelchair propulsion.

Effect of wheelchair stroke pattern on mechanical efficiency.

de Groot S, Veeger HEJ, Hollander AP, van der Woude LHV: Effect of wheelchair stroke pattern on mechanical efficiency. Am J Phys Med Rehabil 2004;83:640–649. Objective:To investigate the effect of different wheelchair stroke patterns on efficiency and propulsion technique (force application and timing). Design:Inexperienced, able-bodied subjects were randomly divided into two velocity groups (1.11 m/sec [n = 13] and 1.39 m/sec [n = 11]). An external (medium) load was set at 0.23 N/kg. Subjects performed four 4-min exercise blocks on a wheelchair ergometer. The first block was performed with a freely chosen movement pattern of the hand. Thereafter, the pumping, semicircular, or single–looping over propulsion pattern were performed in a counterbalanced order. Gross mechanical efficiency and propulsion technique variables were measured with Oxycon Alpha and an instrumented wheelchair ergometer. Results:A significant difference was found for mechanical efficiency, with pumping showing the highest efficiency and semicircular the lowest efficiency, regardless of velocity. Timing variables and negative power deflections before and after the push phase showed significant differences between the stroke patterns. Conclusions:Pumping is the energetically most efficient stroke pattern in contrast to the semicircular pattern in this subject group. Propulsion technique could not explain the difference in efficiency.

Adaptations in physiology and propulsion techniques during the initial phase of learning manual wheelchair propulsion

de Groot S, Veeger HEJ, Hollander AP, van der Woude LHV: Adaptations in physiology and propulsion techniques during the initial phase of learning manual wheelchair propulsion. Am J Phys Med Rehabil 2003;82:504–510. ObjectiveThe purpose of this study was to analyze adaptations in gross mechanical efficiency and wheelchair propulsion technique in novice able-bodied subjects during the initial phase of learning hand-rim wheelchair propulsion. DesignNine able-bodied subjects performed three 4-min practice blocks on a wheelchair ergometer. The external power output and velocity of all blocks was, respectively, 0.25 W/kg and 1.11 m/sec. Gross mechanical efficiency, force application, timing, and intercycle variability were measured. ResultsNo change in gross mechanical efficiency was found. However, a decrease in push frequency occurred, which was accompanied by an increase in work per cycle and a decrease in percentage push time. The increase in work per cycle was associated with a higher peak torque. No changes in intercycle variability were visible over time. ConclusionsThe timing variables had already changed during the initial phase of learning manual wheelchair propulsion. However, for other variables, such as force production, gross mechanical efficiency, and intercycle variability, a longer practice period might be necessary to induce a change. The effective force direction seemed to be optimized from the start of the learning process onward.

Changes in lipid, lipoprotein and apolipoprotein profiles in persons with spinal cord injuries during the first 2 years post-injury

Objective: To investigate changes in lipid, lipoprotein and apolipoprotein profiles in persons with spinal cord injury (SCI) during the first 2 years post-injury, and to determine whether changes in risk profiles were associated with sport activity and/or changes in physical capacity parameters. Design: Risk profiles and physical capacity were investigated in 19 subjects with recent SCI during rehabilitation (t1) and ±1 year after discharge from rehabilitation (t2). Main outcome measures: Changes in total plasma cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), apolipoprotein-A1 (ApoA1), apolipoprotein-B (ApoB) concentrations, the ratios TC/HDL-C, LDL-C/HDL-C, ApoA1/ApoB and HDL-C/ApoA1, and physical capacity (maximal isometric strength, sprint power output, maximal power output, aerobic power). Results: Risk profile parameters changed towards more favorable values at t2, except for HDL-C (P=0.06), TG and HDL-C/ApoA1. Sport activity and changes of the physical capacity were the most important determinants of changes in lipid and (apo)lipoprotein profiles, showing more favorable values with larger increases of the physical capacity and in persons who were physically active. Conclusion: Results show that the lipid and (apo)lipoprotein profiles improve in persons with SCI during the first 2 years post-injury, and that improving the physical capacity or being physically active can improve the lipid and (apo)lipoprotein profiles.

The relationship between heart rate and oxygen uptake during non-steady state exercise

In this study the validity of using heart rate (HR) responses to estimate oxygen uptake ([Vdot]O2) during varying non-steady state activities was investigated. Dynamic and static exercise engaging large and small muscle masses were studied in four different experiments. In the first experiment, 16 subjects performed an interval test on a cycle ergometer, and 12 subjects performed a field test consisting of various dynamic leg exercises. Simultaneous HR and [Vdot]O2 measurements were made. Linear regression analyses revealed high correlations between HR and [Vdot]O2 during both the interval test (r= 0.90±0.07) and the field test (r= 0.94±0.04). In the second experiment, 14 non-wheelchair-bound subjects performed both an interval wheelchair test on a motor driven treadmill, and a wheelchair field test consisting of dynamic and static arm exercise. Significant relationships were found for all subjects during both the interval test (r = 0.91±0.06) and the field test (r= 0.86±0.09). During non-steady state exercise using both arms and legs in a third experiment, contradictory results were found. For 11 of the 15 subjects who performed a field test consisting of various nursing tasks no significant relationship between HR and [Vdot]O2 was found (r= 0.42±0.16). All tasks required almost the same physiological strain, which induced a small range in data points. In a fourth experiment, the influence of a small data range on the HR-[Vdot]O2 relationship was investigated: five subjects performed a field test that involved both low and high physiological strain, non-steady state arm and leg exercise. Significant relationships were found for all subjects (r = 0.86±0.04). Although the r-values found in this study were less than under steady state conditions, it can be concluded that [Vdot]O2 may be estimated from individual HR-[Vdot]O2 regression lines during non-steady state exercise.