Energy expenditure of ambulation using the Sure-Gait crutch and the standard axillary crutch.

For many patients who must ambulate non-weight bearing (NWB) on one lower extremity the energy expenditure during gait may be a limiting aspect to activity. Patients who use crutches or canes may have physical limitations that impair their ability to meet the metabolic demands of assisted gait. In elderly patients, who generally are less strong and have poorer endurance than younger patients, prolonged crutch walking may be impossible.

Many investigators have examined energy expenditure during ambulation with assistive devices. [1-6] It is well documented that ambulation using assistive gait devices increases energy expenditure [1-8] compared with normal walking. This finding suggests that walking with assistive devices is a significant physiological stressor that should be considered in any therapeutic plan. [7] Ganguli and associates reported that use of axillary crutches imposed a greater metabolic cost for lower extremity amputees during activities of daily living compared with the energy expenditure of healthy subjects or amputees using prostheses. I Waters and associates reported a significantly greater energy expenditure during NWB swing-through crutch gait when compared with the energy demands of walking with a weight-bearing cast. [7] These findings show that the energy, demand is relatively high, and as a result, persons with low physical work capacity may not be able to ambulate with crutches.

Hinton and Cullen determined the energy cost of ambulation using the Ortho crutch and the standard axillary (SA) crutch in comparison with unassisted gait in healthy male college students. [2] Although a significant increase in energy cost was shown between crutch walking and unassisted gait, there was no significant difference between the Ortho crutch and the SA crutch. They reported, however, that during NWB ambulation for short periods of time, the Ortho crutch was less taxing than the SA crutch in energy costs and heart rate (HR) demands. [2]

The Sure-Gait (SG) crutch and the SA crutch are very similar in design. The major structural difference is the weight-bearing "tip" of the SG crutch (Fig. 1). The manufacturer of the SG claims that the device offers superior stability, superior gait, and a revolutionary crutch design. We believe that if the SG does provide increased stability and does represent a new, revolutionary crutch design, those features might be manifested in a gait that is less costly in terms of energy expenditure. To date, no published data comparing the energy demands placed on patients using the SA and SG crutches have been found. The purpose of this study, therefore, was to compare the oxygen consumption (VO[.sub.2]) and HR responses in subjects using the SA crutch compared with subjects using the SG crutch. Comparisons were made to determine whether walking with one crutch type was less demanding in terms of energy expenditure than walking with the other crutch type. The null hypothesis was that there is no significant difference in VO[.sub.2] or HR during ambulation with the SA crutch compared with the SG crutch.

Method

Subjects

The subject selection procedure and subject test conditions met the criteria for acceptable research practice as determined by the Institutional Review Board of Northern Arizona University. Standard advertising methods were used to gather the subject sample from the community of Flagstaff, Ariz.

Ten healthy male volunteers, ranging in age from 40 to 60 years, participated in this study. All subjects completed an extensive medical questionnaire to ensure no history of cardiovascular, respiratory, or orthopedic disorders. After reviewing the medical history and interviewing all volunteers, the subjects were given final clearance by their personal physician to participate in the study. The subjects were fully informed of the potential risks and benefits of the study, and each subject signed a consent form.

To ensure that cardiovascular responses to treadmill walking were not artificially elevated (that is, to reduce test anxiety), all subjects performed a nonassisted normal gait at a constant speed of 1.5 mph for five minutes. Because the volunteers were unfamiliar with crutch walking, all subjects underwent a gait-training instruction period. They were taught a three-point, swing-to, crutch-walking gait pattern that was NWB on the side of their choice. Subjects practiced with both crutch types until they could ambulate freely without the necessity of contact guarding on level ground and on the treadmill. This instruction period familiarized the subjects with the two crutch types and ensured that all of them used the same gait pattern and that they could demonstrate reasonable expertise while using the crutches. in addition, the width of the treadmill belt was 24 in, which allowed easy ambulation with assistive devices.

Instrumentation

The subjects were attached to a three-lead electrocardiograph using a modified lead II to monitor HR continuously throughout the exercise period. Oxygen uptake was determined by analyzing the expired gas volumes using a procedure outlined by Rasmussen. [9] Briefly, this procedure involved the following measurement techniques. During the treadmill-walking trials, the subjects' VO[.sub.2] was continuously measured by placing noseclips on the subjects and having them breath through a mouthpiece connected to a Hans-Rudolph Model 2700 one-way valve. [4] During inspiration, air was drawn in through a Parkinson-Cowan flowmeter. Flowmeter readings were recorded on a Gilson Model 5/6 medical recorder. Respiratory minute volumes were then computed from these readings. Air was exhaled through the mouthpiece into a mixing chamber. From the mixing chamber, a small sample of the expired air was pumped through an Applied Electrochemistry Model S-3A oxygen analyzer and Model CD-3A carbon dioxide analyzer, which had previously been calibrated against gas standards of known concentrations. The expired oxygen values obtained from the oxygen analyzer were subtracted from the ambient oxygen concentration to obtain the percentage of oxygen assimilated during exercise. oxygen uptake was calculated by multiplying the assimilated oxygen concentration by the respiratory minute volumes, which were corrected for standard temperature and pressure-dry (STPD) conditions. In a similar fashion, carbon dioxide (CO,) production was calculated by multiplying the exhaled C02 fractions by the respiratory minute volumes, corrected to STPD conditions. All data reduction was done manually, and the results were analyzed using a microcomputer.

Procedure

The SA and SG crutches were adjusted for each subject in a standing position so that a 1-in space was left under the axilla. The handgrips were positioned to accommodate roughly 15 degrees of elbow flexion. The subjects were tested under three separate exercise conditions comprising one bout of unassisted treadmill walking, one bout of ambulation using the SG crutches, and one bout of ambulation with SA crutches. The order of unassisted gait and crutch-ambulation trials for each subject was randomly determined. Each treadmill test lasted five minutes. A rest period was provided between conditions so that each subject's HR returned to its initial baseline value. During the crutch-walking trials, subjects were brought to an increased exercise HR on the treadmill by ambulating without assistive devices at a 2% grade for the first two minutes. The two-minute 2% grade was used to rapidly increase the subject's HR and prevent excessive upper extremity muscle fatigue, which had occurred in earlier pilot trials when subjects ambulated on the treadmill with crutches for the entire five minutes. Once HR had increased, the moving treadmill was lowered to a 0% grade and the subjects performed three minutes of crutch walking at 1.5 mph. We observed that a steady-state HR was achieved by the fifth minute of treadmill walking (Figs. 2, 3). At this time, the trials were terminated.

Data Analysis

The data for minutes 3 through 5 were analyzed using a two-way analysis of variance (ANOVA) for repeated measures on both factors (crutch and time). A Newman-Keuls multiple comparison post hoc test for significance between means was performed following the determination of a significant F-ratio value. All tests were conducted at the .01 alpha level.

Results

Figures 2 and 3 show the mean VO[.sub.2] and HR values, respectively, for the three experimental conditions. Significant differences (p < 01) were found between the three experimental conditions with respect to both VO[.sub.2] HR (Tabs. 1, 2). Post hoc comparisons of each of the dependent variables showed a significant (p < .01) difference between unassisted gait and either crutch gait. During the first minute of crutch walking (minute 3 of the test), there was a significant difference (p < .01) in the energy demands of the two crutch designs (Figs. 2, 3). The SA crutch was found to be metabolically more costly than the SG crutch. That difference, however, was transient and disappeared by the second minute of crutch walking (minute 4 of the test). There was at least a 141% increase in V02 during either crutch-walking condition compared with unassisted gait (Fig. 2). In addition, the subjects experienced a 47% increase in HR during crutch walking compared with unassisted ambulation (Fig. 3).

Discussion

Corcoran and Brengelmann have criticized the use of treadmills for determining VO[.sub.2] during assisted gait in handicapped individuals. [10] They believed that the treadmill belts were too narrow to accommodate awkward gait, especially when the use of canes or crutches was necessary. In addition, Corcoran and Brengelmann believed that handicapped persons feel unstable on a moving treadmill belt and that the anxiety produces artificial increases in their metabolic expenditure. [10] We believe we were able to overcome these difficulties in part by providing a wider treadmill surface (24 in) on which to test our subjects. This adaptation provided an appropriately wide surface moving at a constant speed during the test procedure. None of the subjects related feelings of anxiety or inhibition during ambulation on the treadmill. More than likely, this outcome was a result of the extensive familiarization procedures used in our study. We also believe that by familiarizing our subjects with the test conditions, much test anxiety was minimized, thus reducing the metabolic expenditure. We suggest a thorough familiarization process be considered a standard part of the testing procedure for all future treadmill gait analysis studies.

We also disagree with Corcoran and Brengelmann's [10] conclusion that a continuously moving treadmill acts to destabilize awkward gaits in handicapped individuals and, therefore, is not an appropriate tool to measure the energy consumption of walking. Although treadmill walking does not mimic the variable speed of normal, unassisted gait, it does offer a completely flat surface without the standard pitfalls of walking on uneven ground. We also believe that gait speed is an important variable to control because of the relationship between velocity and energy expenditure. [2] Because the treadmill belt moves at a constant speed, it allows the subjects to achieve steady-state work, ensuring an accurate measure of true VO[.sub.2] for a known quantity of work. From our experience, the treadmill is a valuable and appropriate tool to measure VO[.sub.2] during crutch-assisted gait.

It appears from our metabolic data that the upper extremity work demands during steady-state exercise are similar for walking with the two crutch types during much of the test. The significant increase in VO[.sub.2] and HR during ambulation with crutches compared with unassisted gait is consistent with the findings of many other investigators. [1-8] Our findings at the various time periods during the walking trials are similar to those of Hinton and Cullen. [2] They reported that the metabolic cost of walking with either the SA crutch or the Ortho crutch produced different energy demands for the first 2.5 minutes of walking. They suggested that differences in VO[.sub.2] between walking with the two crutch types during the initial 2.5 minutes could he accounted for by the different designs in the two crutches. They did not find differences in VO[.sub.2] with either crutch, however, from minutes 2.5 to 11.5.

Although our data are similar to those reported by Hinton and Cullen, [2] we would suggest an alternative explanation for the differences in VO[.sub.2] between walking with the different types of crutches. We find it difficult to support the contention that differences in crutch design exert a significant oxygen demand in the first one to two minutes of crutch walking but do not exert that same demand with prolonged gait. if a design feature does exist that would make assisted gait more efficient, then that design feature would provide that efficiency throughout the period of crutch walking. If it did not, its benefits would he negligible. The differences in VO[.sub.2] and HR during the initial portion of crutch walking is likely the result of differences among subjects in the rate at which they attain a steady state and not of differences in crutch design. Because of the small sample sizes of this study and of Hinton and Cullen's study,2 additional research of the metabolic demands of different gait devices is warranted. A larger sample would minimize the influence of subject variability and strengthen any conclusions made. Additional research might also focus on the use of a patient population sample, nontreadmill walking, or other dependent variables that may also reflect efficiency of gait (eg, balance, electromyographic activity).

Summary

Within the limitations of the present investigation, we conclude that ambulation with an assistive device results in increased metabolic demand, as represented by increases in VO[.sub.2], and HR. The SA crutch is metabolically more demanding than the SG crutch during the initial minute of use. This difference, however, was not found after two minutes of ambulation. We believe that this initial difference was caused by subject variability rather than differences in crutch design.

References

1 Ganguli S, Bose KS, Datta SR, et al: Biomechanical approach to the functional assessment of the use of crutches for ambulation. Ergonomics 17:365-374, 1974

2 Hinton CA, Cullen KE: Energy expenditure during ambulation with Ortho crutches and axillary crutches. Phys Ther 62:813-819, 1982

3 Cordrey LJ, Ford AB, Ferrer MT: Energy expenditure in assisted ambulation. j Chronic Dis 7:228-233, 1958

4 Bard G, Ralston HJ: Measurement of energy expenditure during ambulation, with special reference to evaluation of assistive devices. Arch Phys Med Rehabil 40:415-420, 1959

5 Fisher SV, Patterson RP: Energy cost of ambulation with crutches. Arch Phys Med Rehabil 62:250-256, 1981

6 McBeath AA, Bahrke M, Balke B: Efficiency of assisted ambulation determined by oxygen consumption measurement. J Bone joint Surg [Am] 56:994-1000, 1974

7 Waters RL, Campbell J, Thomas L, et al: Energy costs of walking in lower-extremity plaster casts. J Bone joint Surg [Am] 64:896-899, 1982

8 Patterson RP, Fisher SV: Cardiovascular stress of crutch walking. Arch Phys Med Reliabil 62:257-260, 1981

9 Rosmussen S: Characteristics of oxygen intake. J Sports Med Phys Fitness 15:105-1 1 1, 1975

10 Corcoran PJ, Brengelmann GL: Oxygen uptake in normal and handicapped subjects, ill relation to speed of walking beside a velocity controlled cart. Arch Phys Med Reliabil 51:7L 87, 1970

(Tables and other figures omitted)