Volume 89, Issue 3, Pages 430-434 (March 2008)

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ABSTRACT

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Daily Physical Activity and Heart Rate Response in People With a Unilateral Traumatic Transtibial Amputation

Presented in part to the European Society of Physical and Rehabilitation Medicine, May 20, 2006, Madrid, Spain.

Abstract

Bussmann JB, Schrauwen HJ, Stam HJ. Daily physical activity and heart rate response in people with a unilateral traumatic transtibial amputation.

Objectives

To test the hypothesis that people with a unilateral traumatic transtibial amputation are less active than people without an amputation, and to explore whether both groups have a similar heart rate response while walking.

Design

A case-comparison study.

Setting

General community.

Participants

Nine subjects with a unilateral traumatic transtibial amputation and 9 matched subjects without known impairments.

Interventions

Not applicable.

Main Outcome Measures

Percentage of dynamic activities in 48 hours (expressing activity level). Additionally, we examined heart rate and percentage heart rate reserve during walking (expressing heart rate response) and body motility during walking (expressing walking speed). These parameters were objectively measured at participants’ homes on 2 consecutive days.

Results

Subjects with an amputation showed a lower percentage of dynamic activities (6.0% vs 11.7% in a 48-h period, P=.02). No significant differences were found between the 2 groups in heart rate (91.1bpm vs 89.5bpm, P=.86) and percentage heart rate reserve during walking (28.2% vs 27.5%, P=1.0). Body motility during walking was lower in the amputation group (.14g vs .18g, P<.01).

Conclusions

Our results support our hypothesis that persons with a unilateral traumatic transtibial amputation are considerably less active than persons without known impairments. The results indicate that heart rate response during walking is similar in both groups, and is probably regulated by adapting one’s walking speed.

Key Words: Activities of daily living, Amputation, Exertion, Monitoring, ambulatory, Rehabilitation

Article Outline

• Abstract

• Methods

• Participants

• Protocol

• Instruments and Data Analysis

• Activity monitor

• Data analysis

• Heart rate response

• Statistical Analysis

• Results

• Discussion

• Study Limitations

• Conclusions

• References

• Copyright

LOWER-LIMB AMPUTATIONS remain a common intervention in the treatment of patients with vascular, oncologic, or traumatic etiology. Globally, the incidence of major lower-limb amputation ranges from 3.7 to 58.7 per 100,000 men, and from 0.5 to 32.0 per 100,000 women a year.1 A rate of about 20 persons per 100,000 has been reported in the Netherlands.2, 3 Within this total group of amputations, 94% were of vascular origin, 3% were of a traumatic origin, and 3% were of oncologic origin.2

A lower-limb amputation imposes energy penalties for ambulation.4 Although many people with amputations learn to walk with a prosthesis, their walking is less energy efficient compared with that of able-bodied subjects and results in increased physical strain at a given walking speed.4, 5, 6 Another effect of using a prosthesis may be that people will avoid strenuous activities7, 8 or will perform them at a slower pace (eg, slower walking speed).4, 5, 6, 9

To gain insight into the daily life activity level of, and physical strain on, persons with lower-limb amputations, subjective methods such as questionnaires, interviews, and diaries are used. Research is also performed in a movement laboratory setting; however, these studies do not automatically allow conclusions to be drawn about the level of, and physical strain resulting from, activities during normal daily living. Instruments have been developed in the last decade that provide an objective measurement of activity, gait, or steps outside a laboratory setting.10, 11, 12, 13, 14, 15

One such device is the accelerometry-based activity monitor, an instrument that makes possible the prolonged measurement of body postures and motions in normal daily life; it has been validated and applied in several studies of amputee subjects.16, 17, 18, 19, 20 In 1 study20 of subjects with a transtibial amputation resulting from vascular disease, the activity monitor was used to determine their level of daily physical activity and heart rate response during walking. The results showed that they were considerably less active and that their heart rate response while walking did not differ from that of an able-bodied comparison group. In that study, the body motility during walking (expressing walking speed18, 21) was also lower in the amputation group; therefore, it was hypothesized that patients with vascular transtibial amputations adapt their walking speed to keep the heart rate response within the normative range. Subsequently, the question was asked whether these findings are also applicable to other subgroups of persons with lower-limb amputations; the literature suggests that adaptation strategies of persons with a traumatic amputation may be different.4, 22 Therefore, our purpose in this study was to investigate to what extent persons with a traumatic transtibial amputation are less active than an able-bodied comparison group, and to explore whether they have a similar heart rate response when walking as a result of adjusting their walking speed.

Methods

Participants

The study included 9 men with traumatic amputation of the lower leg and 9 matched able-bodied men. Power analysis input for the amputation group was based on an expected maximal average percentage of dynamic activities ± standard deviation (SD) of 7.5%±2.6%.20 Data for the comparison group were derived from a large reference file with data from healthy subjects (mean percentage, 11.5%±4.2%). The α error level was set at .05, the β error level at 0.2.

All participants signed an informed consent form before we began the measurements, and the Medical Ethical Committee of Erasmus Medical Center approved the study. The amputee subjects were recruited from the files of patients of the Department of Rehabilitation Medicine of Erasmus MC and the Rehabilitation Centre Rijndam. Inclusion criteria for these subjects were: unilateral transtibial amputation, traumatic origin of amputation, more than 1 year post-trauma, ability to walk with a prosthesis, age greater than 16 years, completed a rehabilitation program, and able to complete a questionnaire to the best of their ability. An able-bodied comparison subject was matched with an amputee subject. Match criteria were sex, age (±3y), social situation (living alone or with partner), and employment status (school, job, no job). Subjects with an impairment that would affect activity level and/or physical strain—for example, cardiopulmonary, neurologic, or orthopedic problems, assessed by case history—were excluded from the comparison group. Comparison subjects were recruited from among the relatives of the participating amputees, or from members of the hospital department staff or their relatives.

Protocol

All subjects received written study information. All participants visited the hospital for placement of the activity monitor (recorder and sensors),a at which time the measurements began. Afterward, they returned home, where they continued their usual daily activities, except that they could not shower, bathe, or swim during the 48-hour measurement period. Minimally, 48 hours after the beginning of the measurement, a researcher went to the subject’s house to detach the activity monitor. At the end of each measurement day, subjects completed a diary entry about whether that day’s activities were representative of one’s usual daily activities.

Instruments and Data Analysis

Activity monitor

The rationale for the activity monitor–sensor configuration, the subsequent steps of the signal analysis, and the method of activity detection have been described in detail previously.17 The activity monitor is based on long-term ambulatory measurement of signals from body-fixed ADXL202 acceleration sensors.b A sensor (sensitive in the anteroposterior [AP] direction while standing) was attached at the lateral side of each upper leg, 10cm above the lateral femur condyle. If the prosthesis liner prevented attaching the sensor at that specific place, it was attached as distally as possible on the thigh. The sensor on the other leg was attached at the same height. A third acceleration sensor (sensitive in the AP direction and in longitudinal direction while standing) was attached at the lower side of the sternum. All sensors were connected to a recorder based on Vitaport technology.a The acceleration signals were digitally stored on a flash card (SanDisk PCMCIAa) with a sample frequency of 32Hz. Together with the acceleration signals, an electrocardiographic signal was recorded on the same recorder, with a sample frequency of 128Hz. For this, we used a simple 3-electrode bipolar lead system.23 After the measurements, all signals were downloaded to a personal computer for further analysis.

Data analysis

In this study, we analyzed a total of 48 hours of each measurement. Each second a body posture (sitting, standing, lying) or body motion (walking, running, cycling, other movements) was automatically detected from the acceleration signals. Outcome measures derived were the percentage dynamic activities of 48 hours (the sum of performed body motions), the percentage walking, the percentage of dynamic activities other than walking, and the number of sit-to-stand transitions.

Movement of a leg or the trunk is expressed as variability in the measured accelerometer signal. The higher the movement intensity, the more variable the signal and the higher the value of the motility time series derived from it.17 Motility time series are calculated for all 4 acceleration signals, and have a 1-second time resolution. Body motility, which is also expressed in a time series with a 1-second resolution, is subsequently calculated as the average of these 4 motility signals. The overall body motility over the whole measurement period is a general measure of a person’s activity level. Because 2 previous studies showed that the averaged body motility during walking periods is closely and positively related to walking speed, independent from the walking pattern or efficiency,18, 21 we additionally included body motility during walking as an indicator of walking speed.

Heart rate response

The heart rate was automatically detected from the electrocardiographic signal. The following measures were calculated: (1) resting heart rate (lowest heart rate during the night, measured over 2min), (2) absolute heart rate during walking (mean heart rate during 5 different walking periods >30s), (3) the normalized heart rate during walking (difference between absolute and resting heart rates), and (4) percentage heart rate reserve (normal heart rate divided by the difference between maximum and resting heart rates), in which maximum heart rate was derived from 220bpm minus age.24

Statistical Analysis

We used nonparametric tests (Mann-Whitney U) to examine differences between the amputation and comparison groups. We used the Spearman rank correlation coefficient to examine the relationships between variables. The statistical procedures were performed with SPSSc for Windows. An α value of .05 was set as the level of significance.

Results

Table 1 shows the characteristics of the amputee group and comparison subjects. One person with an amputation used β-blockers and was therefore excluded from the analysis of heart rate data. Subjects with an amputation were significantly less active compared with the comparison subjects, with the exception of the number of sit-to-stand transitions (table 2). The body motility during walking (related to walking speed) and the overall body motility were significantly lower in the amputee group (see table 2). There was no significant difference in the heart rate response data between the 2 groups (table 3).

Table 1.

Characteristics of the Amputation Group and Comparison Subjects


Characteristics	Amputation Group	Comparison Group
Sex (men/women)	9/0	9/0
Age (y)	55.4 (21–73)	55.9 (21–76)
Time since amputation (y)	15.6 (3–61)
Work (yes/no/school)	5/3/1	6/2/1
Social status (partner/living alone)	8/1	8/1

NOTE. Values are n or median (range).

Table 2.

Physical Activity Data of the Study’s 2 Groups


Activity	Amputation Group	Comparison Group	P
Dynamic activities (% of 48-h period⁎)	7.0±2.8	11.4±4.2	.021
Walking (% of 48-h period⁎)	4.9±1.8	6.9±2.1	.083
Sit-to-stand transitions (n/48-h period)	111.5±48.0	105.3±51.3	.501
Dynamic activities besides walking (% of 48-h period⁎)	2.0±1.2	4.5±2.9	.034
Body motility during walking (g)†	0.14±0.02	0.18±0.02	.003
Overall body motility (g)†	0.016±0.004	0.030±0.010	.007

NOTE. Values are mean ± SD.

⁎

One percent of a 48-hour period represents 14.4min/d.

†

One unit of acceleration equals 9.81m/s2.

Table 3.

Data on Heart Rate Responses of the Study Participants


Heart Rate Response	Amputation Group	Comparison Group	P
Resting heart rate (bpm)	60.9±12.9	62.6±8.7	0.82
HRabs (bpm)	91.1±15.9	89.5±16.1	0.86
HRnorm (bpm)	30.3±17.6	26.9±10.4	0.86
Percentage heart rate reserve	28.2±14.7	27.5±9.4	1.00

NOTE. Values are mean ± SD.

Abbreviations: HRabs, absolute heart rate during walking; HRnorm, normalized heart rate during walking.

Discussion

In this study, we measured the impact of a unilateral traumatic transtibial amputation on activity levels during normal daily life, and we explored the effect on heart rate response. This study was a follow-up to a previous study20 in which we assessed the impact of a vascular transtibial amputation, and which was focused on the hypothesis that people with a transtibial amputation are less active and adapt their walking speed to keep the heart rate response within normal range. Because that study involved people with a unilateral vascular transtibial amputation, and because adaptation strategies of amputee subjects may depend on the cause of amputation,4, 22 we did not generalize the results to other people with amputations. Therefore, the present study was directed at amputees with a traumatic transtibial amputation.

People with a traumatic amputation are on average younger than people with a vascular amputation4; this is true among patients in our department. Therefore, we expected to include a considerably younger population than the population in our earlier study20 of people with a vascular amputation. Unexpectedly, however, the average age of subjects in the present study was similar to that of the vascular group in our previous study, which permitted us to exclude the effects of age when comparing results of the 2 studies. We found that our amputees were significantly less active compared with the able-bodied subjects. This finding cannot be attributed to the comparison group whose percentage of dynamic activities in this study (11.4%) is similar to the average percentage (11.6%) found in earlier studies.25 In the vascular amputation study,20 the amputees performed dynamic activities for 4.3% of the time, which is considerably less than the 7.0% performance of our traumatic amputees in the present study. This is, however, not unexpected because the traumatic amputees are likely to have better physical fitness compared with vascular amputees.4

In this study, all activity measures showed significant differences between the 2 groups, with the exception of the number of sit-to-stand transfers. The results indicate that this lower activity level could not only be attributed to less walking; significant differences were also found for the parameter “dynamic activities besides walking” (including cycling, body transitions, and other movements, but not walking). There was also no significant difference in the number of sit-to-stand transitions in the people with vascular amputations. This was attributed to the fact that amputee subjects either have no problems with these transfers, or are unable to avoid these transfers in their normal daily life. It should also be noted, however, that the variation in the number of transfers between persons was relatively large, which may have resulted in a type II error.

We found in this study that the amputation group had a resting heart rate similar to that of the comparison group, which indicates that both groups had a similar level of physical fitness,26, 27 contrary to results of our study of vascular amputees, where there was a mean difference in resting heart rate of 9.1bpm. We found no differences in heart rate response during walking between the 2 groups, which also supports the hypothesis that people with a traumatic transtibial amputation keep their heart rate response within normative range while walking. It is generally accepted that walking with a prosthesis is less efficient than walking without one, and at predetermined walking speeds this will result in a higher rate of energy expenditure per distance travelled and per time unit.4, 5, 6 At a self-selected walking speed, however, there may not be a higher rate of energy expenditure per time unit because the effects of lower efficiency can be counterbalanced by a lower self-selected walking speed. This mechanism has been described by others,4, 5, 6 but based on laboratory measurements; it has never been examined during normal daily life. Furthermore, the literature is ambiguous on this point. For example, it has been reported that, in particular, young people with transtibial amputations may choose a walking speed almost similar to healthy subjects, against a higher rate of energy expenditure per time unit.4, 22

This is not supported by our study results; in addition to there being no differences in heart rate response, the evidence suggests a slower walking speed, based on the data on body motility during walking.18, 21 Possible explanations may be that these studies took place in laboratory settings and that the subjects involved were younger. When we compare—without testing of significance—data from the present study with the data of the vascular amputation group, the mean body motility during walking (expressing walking speed18, 21) in the vascular amputation group seems to be considerably lower than in the traumatic group (0.11 and 0.14g, respectively). Traumatic amputees seem to walk slower than healthy controls, but faster than vascular amputees, which has also been reported by others.4, 5, 6, 9

Study Limitations

This study has some potential limitations, of which its relatively small sample size (N=18) is the first. The number of subjects was based on power analysis of data on the percentage of dynamic activities. Almost all activity monitor outcome measures showed significant differences between groups. In contrast, no significant differences were found in heart rate response data and a power problem may be present in this data, especially because of the large between-subject variance. The current data, however, do not indicate that there were any clinically significant differences between the amputation group and comparison subjects. Some caution is needed, however, in interpreting the results and in applying them to other amputee groups. Future studies could investigate other amputation levels, younger age groups, and could include women. A second limitation may be the relatively short 48-hour data collection period that we set because of subjects’ measurement load. Among adults, at least 3 to 5 days of monitoring is recommended in literature.28 These recommendations, however, depend on whether individual-level estimates or population-level estimates, as in the present study, are needed. Furthermore, in our study the issue of measurement days being representative or not was addressed by a diary entry; none of the measurement days were reported to differ significantly from other days. Of course, a longer data collection period would have been preferable, and some of the currently available instruments do allow this. But compared with our system, these instruments generally provide less detailed information on a subject’s activities and the physical strain of performing these activities. The issue of the duration of the collection period will be less important and restrictive in the future because technologic developments will lower the measurement load and provide an increase in detailed data gathered from these types of measurements.

Conclusions

Our results confirm the hypothesis that persons with a unilateral traumatic transtibial amputation are less active than persons without known impairments. The results also indicate that the heart rate response during walking is similar in both groups. This is probably the result of amputees adapting their walking speed.

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References

1. 1The Global Lower Extremity Amputation Study Group. Epidemiology of lower extremity amputation in centers in Europe, North America and East Asia. Br J Surg. 2000;87:328–337. MEDLINE | CrossRef

2. 2Rommers GM, Vos LD, Groothoff JW, Schuiling CH, Eisma WH. Epidemiology of lower limb amputees in the north of the Netherlands: aetiology, discharge destination and prosthetic use. Prosthet Orthot Int. 1997;21:92–99. MEDLINE

3. 3van Houtem WH, Rauwerda JA, Ruwaard D, Schaper NC, Bakker K. Reduction in diabetes-related lower-extremity amputations in the Netherlands: 1991-2000. Diabetes Care. 2004;27:1042–1046. MEDLINE | CrossRef

4. 4Waters RL, Mulroy S. The energy expenditure of normal and pathologic gait. Gait Posture. 1999;9:207–231. Abstract | Full Text | Full-Text PDF (278 KB) | CrossRef

5. 5Ward KH, Meyers C. Exercise performance of lower-extremity amputees. Sports Med. 1995;20:207–214. MEDLINE | CrossRef

6. 6Czerniecki JM. Rehabilitation in limb deficiency (1. Gait and motion analysis). Arch Phys Med Rehabil. 1996;77(3 Suppl):S3–S8. Abstract | Full-Text PDF (783 KB) | CrossRef

7. 7Pernot HF, Winnubst GM, Cluitmans JJ, De Witte LP. Amputees in Limburg: incidence, morbidity and mortality, prosthetic supply, care utilisation and functional level after one year. Prosthet Orthot Int. 2000;24:90–96. MEDLINE | CrossRef

8. 8Collin C, Collin J. Mobility after lower-limb amputation. Br J Surg. 1995;82:1010–1011. MEDLINE | CrossRef

9. 9van Velzen JM, van Bennekom CA, Polomski W, Slootman JR, van der Woude LH, Houdijk H. Physical capacity and walking ability after lower limb amputation: a systematic review. Clin Rehabil. 2006;20:999–1016. MEDLINE | CrossRef

10. 10Stam HJ, Eijskoot F, Bussmann JB. A device for long-term ambulatory monitoring in trans-tibial amputees. Prosthet Orthot Int. 1995;19:53–55. MEDLINE

11. 11Hafner BJ, Willingham LL, Buell NC, Allyn KJ, Smith DG. Evaluation of function, performance, and preference as transfemoral amputees transition from mechanical to microprocessor control of the prosthetic knee. Arch Phys Med Rehabil. 2007;88:207–217[published erratum in: Arch Phys Med Rehabil 2007;88:544]. Abstract | Full Text | Full-Text PDF (314 KB) | CrossRef

12. 12Stepien JM, Cavenett S, Taylor L, Crotty M. Activity levels among lower-limb amputees: self-report versus step activity monitor. Arch Phys Med Rehabil. 2007;88:896–900. Abstract | Full Text | Full-Text PDF (203 KB) | CrossRef

13. 13Coleman KL, Boone DA, Laing LS, Mathews DE, Smith DG. Quantification of prosthetic outcomes: elastomeric gel liner with locking pin suspension versus polyethylene foam liner with neoprene sleeve suspension. J Rehabil Res Dev. 2004;41:591–602. MEDLINE | CrossRef

14. 14Armstrong DG, Abu-Rumann PL, Nixon BP, Boulton AJ. Continuous activity monitoring in persons at high risk for diabetes-related lower-extremity amputation. J Am Podiatr Med Assoc. 2001;91:451–455. MEDLINE

15. 15van Dam MS, Kok GJ, Munneke M, Vogelaar FJ, Vliet Vlieland TP, Taminiau AH. Measuring physical activity in patients after surgery for a malignant tumour in the leg (The reliability and validity of a continuous ambulatory activity monitor). J Bone Joint Surg Br. 2001;83:1015–1019. CrossRef

16. 16Bussmann JB, Reuvekamp PJ, Veltink PH, Martnes WL, Stam HJ. Validity and reliability of measurements obtained with an “Activity Monitor” in people with and without a transtibial amputation. Phys Ther. 1998;78:989–998. MEDLINE

17. 17Bussmann JB, Martens WL, Tulen JH, Schasfoort FC, van den Berg-Emons HJ, Stam HJ. Measuring daily behaviour using ambulatory accelerometry: the Activity Monitor. Behav Res Meth Instrum Comp. 2001;33:349–356.

18. 18Bussmann JB, van den Berg-Emons HJ, Angulo SM, Stijnen T, Stam HJ. Sensitivity and reproducibility of accelerometry and heart rate in physical strain assessment during prosthetic gait. Eur J Appl Physiol. 2004;91:71–78. MEDLINE | CrossRef

19. 19Selles RW, Janssens PJ, Jongenengel CD, Bussmann JB. A randomized controlled trial comparing functional outcome and cost efficiency of a total surface-bearing socket versus a conventional patellar tendon-bearing socket in transtibial amputees. Arch Phys Med Rehabil. 2005;86:154–161. Abstract | Full Text | Full-Text PDF (156 KB) | CrossRef

20. 20Bussmann JB, Grootscholten EA, Stam HJ. Daily physical activity and heart rate response in people with a unilateral transtibial amputation for vascular disease. Arch Phys Med Rehabil. 2004;85:240–244. Abstract | Full Text | Full-Text PDF (66 KB) | CrossRef

21. 21Bussmann JB, Hartgerink I, van der Woude LH, Stam HJ. Measuring physical strain during ambulation with accelerometry. Med Sci Sports Exerc. 2000;32:1462–1471. MEDLINE | CrossRef

22. 22Torburn L, Powers CM, Guiterrez R, Perry J. Energy expenditure during ambulation in dysvascular and traumatic below-knee amputees: a comparison of five prosthetic feet. J Rehabil Res Dev. 1995;32:111–119. MEDLINE

23. 23Drew BJ, Califf RM, Funk M, et al. Practice standards for electrocardiographic monitoring in hospital settings. Circulation. 2004;110:2721–2746. CrossRef

24. 24Miller WC, Wallace JP, Eggert KE. Predicting max HR and HR-VO2 relationship for exercise prescription in obesity. Med Sci Sports Exerc. 1993;25:1077–1081. MEDLINE

25. 25van den Berg-Emons RJ, Schasfoort FC, de Vos LA, Bussmann JB, Stam HJ. Impact of chronic pain on everyday physical activity. Eur J Pain. 2007;11:587–593. Abstract | Full Text | Full-Text PDF (260 KB) | CrossRef

26. 26Mensink GB, Hoffmeister H. The relationship between resting heart rate and all-cause cardiovascular and cancer mortality. Eur Heart J. 1997;18:1404–1410.

27. 27van Mechelen W, Twisk JW, Van Lenthe FJ, Post GB, Snel J, Kemper HC. Longitudinal relationships between resting heart rate and biological risk factors for cardiovascular disease: the Amsterdam Growth and Health Study. J Sports Sci. 1998;16(Suppl 1):S17–S23.

28. 28Ward DS, Evenson KR, Vaughn A, Rodgers AB, Troiano RP. Accelerometer use in physical activity: best practices and research recommendations. Med Sci Sports Exerc. 2005;37(11 Suppl):S582–S588. MEDLINE | CrossRef

a Department of Rehabilitation Medicine, Erasmus University Medical Center Rotterdam, The Netherlands

b Rijndam Rehabilitation Center, Rotterdam, The Netherlands.

Reprint requests to Johannes B. Bussmann, PhD, Dept of Rehabilitation Medicine, Erasmus Medical Center, PO Box 2040, 3000 CA Rotterdam, The Netherlands

No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated.

a TEMEC Instruments, Spekhofstraat 2, PO Box 3011, 6460 HA Kerkrade, the Netherlands.

b Analog Devices, adapted by TEMEC Instruments, Spekhofstraat 2, PO Box 3011, 6460 HA Kerkrade, the Netherlands.

c SPSS Inc, 233 S Wacker Dr, 11th Fl, Chicago, IL 60606.

PII: S0003-9993(07)01802-3

doi:10.1016/j.apmr.2007.11.012

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