Develop. Med. Child Neurol. 1975, 17,434439
Mechanical Efficiency in Bicycle Ergometer Work of Young Adults with Cerebral Palsy Aoke Lundberg
distinguish any difference in mechanical efficiency between patients with various forms of cerebral palsy.
Introduction The spastic forms of cerebral palsy are characterised by augmented stretch reflexes, as evidenced by increased sensitivity of the stretch receptors (Pedersen 1969). In affected people who are able to walk, this leads to a slow, difficult pattern of gait because of the reduced rate of movement and length of individual steps. The dyskinetic forms of cerebral palsy are characterised by frequent changes in muscle tonus which produce involuntary activity, primarily of the extremities. In the ataxic forms there is disordered movement coordination, but muscle tonus is more normal. These differences in motor function are reflected in the dragging gait of those with spasticity, compared with the jerky gait of those with the dyskinetic or ataxic forms. The type of gait could justify the working hypothesis that the spastic individual’s mechanical efficiency is less than that of the dyskinetic or ataxic individual. However, no such difference has been observed in earlier studies (e.g. Berg 1970). The aim of the present study was to investigate, by using a method specially adapted to the restrictions in motor function characteristic of cerebral palsy, whether bicycle ergometer work could ~~
Subjects and Method The subjects were 10 pupils (seven male, three female) with cerebral palsy who were attending Ingemundskolan, an uppersecondary schooI for handicapped young adults (Table I). Their ages ranged from 18 to 30 years (median 21 years). The ratio of body weight to body height was within normal limits, according to the growth chart of Karlberg and Iggbom (1959), although nine of the 10 were shorter than the normal population. Intellectual development was within normal limits in all cases. Six of the 10 subjects (all men) were in the dyskinetic/ataxic group; the other four (three of whom were women) were in the spastic group. They were classified according to the system of Berg (1970) and Hagberg et al. (1972). The degree of motor disability varied from slight (no aids required; Cases 2, 5 , 6, 10) to fairly severe (e.g. assistance required with daily activities or walking; Cases I , 3,4, 7, 8,9). Six non-handicapped people (three men, three women) aged between 18 and 25 years constituted the control group.
~.
~~
Assistant Professor, Medical Department for Adolescents, Ingemundskolan, S-104-01 Stockholm 60, Sweden.
434
~ K LUNDBERC E
TABLE I Subjects
1
Case no.
Height ( e m )
Weight ( k g )
Tvpe of cerebral palsv
58 68 52 52
21 21
I77 I78 I62 171 171 I72
Dyskinetic syndrome Ataxia Dyskinetic syndrome Dyskinetic syndrome Ataxia Ataxia
M F F F
19 21 27 21
I57 I69 I58 149
51
12 13 ~.
F F F
22 19 18
.14 .
M. .
15
M
20 25
178 158 170 174
16
M
21
Sex
Age (vrs)
1
M
2
M M
18 22 20
4 5 6
M
30
M M
7 8 9
3
10
I
11*
1
1
55
59
Spastic t riplegia Spastic diplegia Spastic diplegia Spastic diplegia
58 64 48 68 55
68 58 68
~
186
I
Cases 1 I to 16are non-handicapped controls. TABLE I1 Individual results of bicycle ergometer tests Work load
Case
(kpmlmin)
No.
x ' R
-
Heart rate (heatslmin) .v R
uptake (Ilmin)
Oxygen
R
v
-x
Ventilation (liinin) R
-
Resprruroi ,r
x
qiiotietit
R
-
1
2 3
4 5 6 7 8 9 10
II
-
662 822 681 758 601 609
584-766 809-843 643-766 717-794 578-629 i 600-624 1
445 430 423 308
428463 401462 402-450 287-320
:600
13
300 600
14
600
15
I253 575
12
16
I
~
_
155
177 165 159 166 145
136165 165-187 158-170 144-170 152-182 ' 129-155 ~
I65 150-173 154-168 181 175-185 I66 153-174 164
_
139 142 145 143 I70
I24
~
1.68-2.19 61.5 1.77-2.22 68.1 I .62-2.OO' 57.4 1.67-2.12 60.8 1.56-1.83 52.5 1.42-1.69 47.2
52.0-77'5 0.96 56.2-76.3 1.08 48.7-65.4 0.96 54.5-66.9 0.99 42.7-59.4 0.95 41.7-52.3 0.98
0.91-1.01 I 03-1.14 0.88-1.08 0.97-1.01 0.85-1.01 0.92-1.04
1.69 1.46-2.05 60.4 1.49 1.18-1.93 47.2 1.55 1.36-1.74 50.5 1.17 0.95-1.30 48.7
54'4-67.8 0.96 39.1-54.7 0.96 45.2-56.2 1.03 39'9-60.0 1.08
0.93-1.02 0.88-1.06 0'98-1.08 0.97-1.19
1.94 2.04 1.86 1.90 1.68 1.62
I .40 0.85 I ,48 I .48 3.07 I .62
The investigation was carried out between March and June 1973, with a mean of one working test each month for each person. The tests were performed on a mechanically-braked bicycle ergometer, according to the method of von Dobeln (1954). The apparatus was equipped with a tachometer to determine pedalling rates. For each individual the force used on
34.0 53.1 58.6 32.6 73.1 39.2
0.93 0.95 0.87
0.89 0.97 0.95
the bicycle ergometer was the same from test to test. The load was calculated from the braking force (kg) x distance moved by a point on the rim during one complete revolution of the pedals (6m) r: the pedalling rate. Heart rate was measured by electrocardiograph (Table I I). Oxygen uptake was determined by collecting expired air in Douglas bags for a
435
DEVELOPMENTAL MEDICINE AND CHILD NEUROLOGY.
1975, 17
was 21.1 per cent for the dyskineticl ataxic group and 15-5 per cent for the spastic group (Table 111). The difference between the groups is statistically significant ( p c .OOl). The mean value for the control group was 22.2 per cent,which is in accordance with the value reported by hitrand and Rodahl(l970). Figure 1 illustrates inter-group differences in mechanical efficiency and the variations in efficiency during the spring season (for more than half the students, there was a tendency for mechanical efficiency to drop from March to April.) The difference in mechanical efficiency between the spastic and the dyskinetic/ ataxic groups is illustrated in Figure 2, which also shows the mean value for the control group. It is evident that there was no difference between the dyskinetic/ ataxic group and the control group.
period of two minutes, the collection starting after four minutes of exercise. Volume was measured in a gasometer and the concentrations of CO, and 0, were analysed according to the Haldane technique. The students rested for 30 minutes on an examination table before baseline measurements of expired air (VO,) were taken. The formula used was : mechanical efficiency (%)= kprn/min x 100 4 2 7 X p 4 ~ V VO,) O ~ ~ work basal 427 is the factor for conversion of calories into force, and 4.9 is the calculated value in calories derived from the combustion of one litre of oxygen in the presence of a normal diet. Work loads and oxygen consumption during work are shown in Table 11, and VO, basal measurements are given in Table 111.
Pedalling Rates The mean pedalling rates were 52.9rpm for the dyskineticlataxic group and 48.9 rpm for the spastic group (Table 111).
Results Mechanical Eficiency The mean value for mechanical efficiency
TABLE 111 Oxygen intake, pedalling rates and mechanical efficiency
I
Case no.
i
Oxygen intake, basal (llmin) predicted* measured
I
U'LJ
U'JL
2 3 4
0.25 0.21
5
0.22 0.23
0.23 0.27 0.28 0.27 0.26
-6
0.20
9
-
10
0.20 0.20 0.21 0.18
0.24 0.25 0.24 0.18
X
11 1.
12 13 14 15
-
16
+0.05
10.03 +0.05
X
7 8
-0.02 +0.06 +0.08
"
LL
0.20 0.22 0.23 0.24 0.27
v L,
0.23 0.20 0.25 0.28 0.26
+O.W +0.05
t0.03
*o +0.03 _~
I n.nt T" v1
+0-03 -0.02 t0.02 +O.W -0.01 $0-01
1
, 1
~
I
Mechanical efficiency (%) Range x
Pedailing rafelmin Range X
-
52'4-56.2 53.7-63.8 47.8-52.9 48.2-52.4 46.7-52.0
54.7 56.8 50.5 50.1 50.1 52.9
47.6-51.4 44.5-51.3 45.1-50.0
49.5 48.0 46.7
I
I
50.6 48.8
I
According to Carpenter (1964)
436
1
,
18.5-23-3 20.4-24.5
19.7 21.8
20.6-23.6
21.7 21.1
12.8-16.6 14.1-18-4 13.8-17.5
15.0 16.5 15.6
91.: L2.J
22.3 22.4 23.6 21.3 20.2 22.2
~ K LUNDBERG E
BasaI 0.uygen Consirniption The mean value for basal oxygen consumption was 0.05 I/min higher for the dyskinetic/ataxic group than the value predicted from the table for non-handicapped adolescents (Carpenter 1964). The spastic students had mean values 0.03 I /min higher than the predicted value. Discussion The dyskinetic/ataxic group pedalled faster than 50rpm and had a mean basal VO, higher than the value predicted from the table for normal adolescents. These findings can be explained by difficulties of perception, neuromuscular dysfunction with involuntary movements, and an inability to relax muscle tonus. However, had it been assumed (incorrectly) that the dyskineticlataxic individual pedals only 50 rpm on the bicycle ergometer and that 25
-
10
-
I
MARCH
APRIL
I
I
M &Y
.IUNL
Fig. 1. Mechanical efficiency in bicycle ergometer work. At top are the six dyskineticiataxic students, below are the four spastic subiects. Mean
IOJ
, , , , , , 1
2
3
4
5
6
CASENO
7
8
9
10
Fig. 2. Mechanical efficiency in bicycle ergometer work. Mean values with range limits during the test period are given for the dyskineticiataxic and spastic groups; mean values only are shown for controls.
437
their basal oxygen consumption was on the same level as non-handicapped adolescents, this calculation would have resulted in a lower mean mechanical efficiency for this group, i.e. 8. 5 per cent lower. The pedalling rate of the spastic group was somewhat less than 50rpm, possibly because of their hypertonus. Basal Y O , was somewhat higher than for nonhandicapped people, but not of the same magnitude as that of the dyskinetic/ataxic group. Had a procedure been used which did not measure pedalling rate or basal VO,, the mean mechanical efficiency for the spastic group would have been 0 . 7 per cent lower. Berg (1970), in bicycle ergometer tests, did not note any differences in mechanical efficiency between the two types of cerebral palsy. The reason may be the differences in composition, diagnostic criteria and ages of the subjects in her study and in our own. In our study, the inclusion of measurements of pedalling rates and basal V O , produced a mean mechanical efficiency for the dyskinetic/ataxic group which was 8.5 per cent higher than if it had been assumed that the people in this group pedalled at 50rpm and had a basal VO, in accordance with the values predicted for non-handicapped people. There was an uneven sex distribution between our handicapped groups, but this is unlikely to have influenced the results since in able-bodied people it has been shown that women have a somewhat lower oxygen intake at a given work-load than do men (Astrand and Rodahl 1970). This is also in agreement with the results in our control group, in which three women had a mean mechanical efficiency of 22.7 per cent, compared with 21 ' 7 per cent for the men. There were similar degrees of disability in our two handicapped groups, in that severe handicap was a necessity for their attending a special school but the handicap
DEVELOPMENTAL MEDICINE AND CHILD NEUROLOGY.
was not severe enough to prevent them performing the bicycle ergometer tests. Within this range, of course, there were variations in the degree of handicap. Patients with dyskinesia often have better function in the legs than in the arms, in contrast to those with spastic diplegia whose equilibration reactions are decreased, resulting in impaired walking ability. These differences in motor performance are closely connected to the type of cerebral palsy and only indirectly influence the observed difference in mechanical efficiency between the two groups. It is
1975. 17
reasonable to conclude, therefore, that the lower mechanical efficiency in the spastic group compared with the dyskineticl ataxic group is explained by the extra amount of energy required to overcome the constant increase in muscle tonus during the bicycle ergometer tests. In the dyskineticlataxic group, on the other hand, less extra energy expenditure was required during the tests. Acknowledgement: This study was carried out with grants from Foreningen for bistHnd Bt lytta och vanfora, Stockholm, and H. K. H. Kronprinsessan Lovisas forening for barnasjukvsrd, Stockholm.
SUMMARY
This study used a method specifically adapted to motor handicap, one which measured pedalling rate and basal oxygen consumption. Its aim was to investigate whether bicycle ergometer work could distinguish any difference in mechanical efficiency between two groups with cerebral palsy. 10 patients aged between 18 and 30 years (six dyskineticlataxic, four spastic) were studied. Six non-handicapped young adults formed a control group. The results showed a highly significant difference between the dyskinetic/ataxic group and the spastic group. Results for the dyskinetic/ataxic group and the control group did not differ significantlyfrom those obtained for a normal population. The observed difference between the two groups with cerebral palsy seems to be the result of the greater amount of energy required to be expended by the spastic group in order to overcome the constant increase in muscle tone during the bicycle ergometer test.
RGSUML Eficience tnkcanique dans un travail de bicyclerte ergomktrique chez de jeunes adultes IMC En utilisant une rnkthode sptcialement adaptee au handicap moteur qui mesure le taux de pedalage et la consommation de base d‘oxyghe, le but de cette etude a cite de chercher si le travail sur bicyclette ergometrique pouvait reveler une difference d’efficience mecanique entre deux types d’mc. 10 sujets de 18 B 30 ans dont six avec une forme ~ I M Cdu type dyskinttiquelataxique et quatre du type spastique ont ete etudies. Un groupe contrble a it6 constitue par six jeunes adultes non handicapes. Le resultat a montrk une difference hautement significative entre les groupes dyskinetique/ ataxique et spastique. Les risultats du groupe dyskinitique/ataxique et du groupe contr6le ne diff6rent pas significativement de ceux d’une population normale. La diffirence observCe entre les deux groupes IMC parait la consequence de la plus grande quantite d’energie necessitee par le groupe spastique pour surmonter I’accroissement constant de tonus musculaire durant le travail sur bicyclette ergomttrique. 438
A K t LUNDBERG
ZUSAMMENFASSUNG
Mecliunisclie Efizienz der Falirrarlergometerarheit hei jirngen Erwdisenen mit Cerrhralparese Unter Anwendung einer speziell fur motorische Behinderung abgestimmten Methode. mit der die Tretrate und der basale Sauerstoffverbrauch gemessen werden, war es das Ziel dieser Studie zu untersuchen, ob durch Fahrradergometerarbeit irgendein Unterschied bei der mechanischen Effizienz zwischen zwei Typen der Cerebralparese zu finden war. 10 Patienten (im Alter von 18 bis 30 Jahren) wurden untersucht, davon hatten sechs eine Cerebralparese vom dyskinetisch-ataktischen Typ und vier eine Cerebralparese vom spastischen Typ. Sechs unbehinderte junge Erwachsene bildeten die Kontrollgruppe. Die Ergebnisse zeigten einen hoch signifikanten Unterschied ( p
Mechanical Efficiency in Bicycle Ergometer Work of Young Adults with Cerebral Palsy Aoke Lundberg
distinguish any difference in mechanical efficiency between patients with various forms of cerebral palsy.
Introduction The spastic forms of cerebral palsy are characterised by augmented stretch reflexes, as evidenced by increased sensitivity of the stretch receptors (Pedersen 1969). In affected people who are able to walk, this leads to a slow, difficult pattern of gait because of the reduced rate of movement and length of individual steps. The dyskinetic forms of cerebral palsy are characterised by frequent changes in muscle tonus which produce involuntary activity, primarily of the extremities. In the ataxic forms there is disordered movement coordination, but muscle tonus is more normal. These differences in motor function are reflected in the dragging gait of those with spasticity, compared with the jerky gait of those with the dyskinetic or ataxic forms. The type of gait could justify the working hypothesis that the spastic individual’s mechanical efficiency is less than that of the dyskinetic or ataxic individual. However, no such difference has been observed in earlier studies (e.g. Berg 1970). The aim of the present study was to investigate, by using a method specially adapted to the restrictions in motor function characteristic of cerebral palsy, whether bicycle ergometer work could ~~
Subjects and Method The subjects were 10 pupils (seven male, three female) with cerebral palsy who were attending Ingemundskolan, an uppersecondary schooI for handicapped young adults (Table I). Their ages ranged from 18 to 30 years (median 21 years). The ratio of body weight to body height was within normal limits, according to the growth chart of Karlberg and Iggbom (1959), although nine of the 10 were shorter than the normal population. Intellectual development was within normal limits in all cases. Six of the 10 subjects (all men) were in the dyskinetic/ataxic group; the other four (three of whom were women) were in the spastic group. They were classified according to the system of Berg (1970) and Hagberg et al. (1972). The degree of motor disability varied from slight (no aids required; Cases 2, 5 , 6, 10) to fairly severe (e.g. assistance required with daily activities or walking; Cases I , 3,4, 7, 8,9). Six non-handicapped people (three men, three women) aged between 18 and 25 years constituted the control group.
~.
~~
Assistant Professor, Medical Department for Adolescents, Ingemundskolan, S-104-01 Stockholm 60, Sweden.
434
~ K LUNDBERC E
TABLE I Subjects
1
Case no.
Height ( e m )
Weight ( k g )
Tvpe of cerebral palsv
58 68 52 52
21 21
I77 I78 I62 171 171 I72
Dyskinetic syndrome Ataxia Dyskinetic syndrome Dyskinetic syndrome Ataxia Ataxia
M F F F
19 21 27 21
I57 I69 I58 149
51
12 13 ~.
F F F
22 19 18
.14 .
M. .
15
M
20 25
178 158 170 174
16
M
21
Sex
Age (vrs)
1
M
2
M M
18 22 20
4 5 6
M
30
M M
7 8 9
3
10
I
11*
1
1
55
59
Spastic t riplegia Spastic diplegia Spastic diplegia Spastic diplegia
58 64 48 68 55
68 58 68
~
186
I
Cases 1 I to 16are non-handicapped controls. TABLE I1 Individual results of bicycle ergometer tests Work load
Case
(kpmlmin)
No.
x ' R
-
Heart rate (heatslmin) .v R
uptake (Ilmin)
Oxygen
R
v
-x
Ventilation (liinin) R
-
Resprruroi ,r
x
qiiotietit
R
-
1
2 3
4 5 6 7 8 9 10
II
-
662 822 681 758 601 609
584-766 809-843 643-766 717-794 578-629 i 600-624 1
445 430 423 308
428463 401462 402-450 287-320
:600
13
300 600
14
600
15
I253 575
12
16
I
~
_
155
177 165 159 166 145
136165 165-187 158-170 144-170 152-182 ' 129-155 ~
I65 150-173 154-168 181 175-185 I66 153-174 164
_
139 142 145 143 I70
I24
~
1.68-2.19 61.5 1.77-2.22 68.1 I .62-2.OO' 57.4 1.67-2.12 60.8 1.56-1.83 52.5 1.42-1.69 47.2
52.0-77'5 0.96 56.2-76.3 1.08 48.7-65.4 0.96 54.5-66.9 0.99 42.7-59.4 0.95 41.7-52.3 0.98
0.91-1.01 I 03-1.14 0.88-1.08 0.97-1.01 0.85-1.01 0.92-1.04
1.69 1.46-2.05 60.4 1.49 1.18-1.93 47.2 1.55 1.36-1.74 50.5 1.17 0.95-1.30 48.7
54'4-67.8 0.96 39.1-54.7 0.96 45.2-56.2 1.03 39'9-60.0 1.08
0.93-1.02 0.88-1.06 0'98-1.08 0.97-1.19
1.94 2.04 1.86 1.90 1.68 1.62
I .40 0.85 I ,48 I .48 3.07 I .62
The investigation was carried out between March and June 1973, with a mean of one working test each month for each person. The tests were performed on a mechanically-braked bicycle ergometer, according to the method of von Dobeln (1954). The apparatus was equipped with a tachometer to determine pedalling rates. For each individual the force used on
34.0 53.1 58.6 32.6 73.1 39.2
0.93 0.95 0.87
0.89 0.97 0.95
the bicycle ergometer was the same from test to test. The load was calculated from the braking force (kg) x distance moved by a point on the rim during one complete revolution of the pedals (6m) r: the pedalling rate. Heart rate was measured by electrocardiograph (Table I I). Oxygen uptake was determined by collecting expired air in Douglas bags for a
435
DEVELOPMENTAL MEDICINE AND CHILD NEUROLOGY.
1975, 17
was 21.1 per cent for the dyskineticl ataxic group and 15-5 per cent for the spastic group (Table 111). The difference between the groups is statistically significant ( p c .OOl). The mean value for the control group was 22.2 per cent,which is in accordance with the value reported by hitrand and Rodahl(l970). Figure 1 illustrates inter-group differences in mechanical efficiency and the variations in efficiency during the spring season (for more than half the students, there was a tendency for mechanical efficiency to drop from March to April.) The difference in mechanical efficiency between the spastic and the dyskinetic/ ataxic groups is illustrated in Figure 2, which also shows the mean value for the control group. It is evident that there was no difference between the dyskinetic/ ataxic group and the control group.
period of two minutes, the collection starting after four minutes of exercise. Volume was measured in a gasometer and the concentrations of CO, and 0, were analysed according to the Haldane technique. The students rested for 30 minutes on an examination table before baseline measurements of expired air (VO,) were taken. The formula used was : mechanical efficiency (%)= kprn/min x 100 4 2 7 X p 4 ~ V VO,) O ~ ~ work basal 427 is the factor for conversion of calories into force, and 4.9 is the calculated value in calories derived from the combustion of one litre of oxygen in the presence of a normal diet. Work loads and oxygen consumption during work are shown in Table 11, and VO, basal measurements are given in Table 111.
Pedalling Rates The mean pedalling rates were 52.9rpm for the dyskineticlataxic group and 48.9 rpm for the spastic group (Table 111).
Results Mechanical Eficiency The mean value for mechanical efficiency
TABLE 111 Oxygen intake, pedalling rates and mechanical efficiency
I
Case no.
i
Oxygen intake, basal (llmin) predicted* measured
I
U'LJ
U'JL
2 3 4
0.25 0.21
5
0.22 0.23
0.23 0.27 0.28 0.27 0.26
-6
0.20
9
-
10
0.20 0.20 0.21 0.18
0.24 0.25 0.24 0.18
X
11 1.
12 13 14 15
-
16
+0.05
10.03 +0.05
X
7 8
-0.02 +0.06 +0.08
"
LL
0.20 0.22 0.23 0.24 0.27
v L,
0.23 0.20 0.25 0.28 0.26
+O.W +0.05
t0.03
*o +0.03 _~
I n.nt T" v1
+0-03 -0.02 t0.02 +O.W -0.01 $0-01
1
, 1
~
I
Mechanical efficiency (%) Range x
Pedailing rafelmin Range X
-
52'4-56.2 53.7-63.8 47.8-52.9 48.2-52.4 46.7-52.0
54.7 56.8 50.5 50.1 50.1 52.9
47.6-51.4 44.5-51.3 45.1-50.0
49.5 48.0 46.7
I
I
50.6 48.8
I
According to Carpenter (1964)
436
1
,
18.5-23-3 20.4-24.5
19.7 21.8
20.6-23.6
21.7 21.1
12.8-16.6 14.1-18-4 13.8-17.5
15.0 16.5 15.6
91.: L2.J
22.3 22.4 23.6 21.3 20.2 22.2
~ K LUNDBERG E
BasaI 0.uygen Consirniption The mean value for basal oxygen consumption was 0.05 I/min higher for the dyskinetic/ataxic group than the value predicted from the table for non-handicapped adolescents (Carpenter 1964). The spastic students had mean values 0.03 I /min higher than the predicted value. Discussion The dyskinetic/ataxic group pedalled faster than 50rpm and had a mean basal VO, higher than the value predicted from the table for normal adolescents. These findings can be explained by difficulties of perception, neuromuscular dysfunction with involuntary movements, and an inability to relax muscle tonus. However, had it been assumed (incorrectly) that the dyskineticlataxic individual pedals only 50 rpm on the bicycle ergometer and that 25
-
10
-
I
MARCH
APRIL
I
I
M &Y
.IUNL
Fig. 1. Mechanical efficiency in bicycle ergometer work. At top are the six dyskineticiataxic students, below are the four spastic subiects. Mean
IOJ
, , , , , , 1
2
3
4
5
6
CASENO
7
8
9
10
Fig. 2. Mechanical efficiency in bicycle ergometer work. Mean values with range limits during the test period are given for the dyskineticiataxic and spastic groups; mean values only are shown for controls.
437
their basal oxygen consumption was on the same level as non-handicapped adolescents, this calculation would have resulted in a lower mean mechanical efficiency for this group, i.e. 8. 5 per cent lower. The pedalling rate of the spastic group was somewhat less than 50rpm, possibly because of their hypertonus. Basal Y O , was somewhat higher than for nonhandicapped people, but not of the same magnitude as that of the dyskinetic/ataxic group. Had a procedure been used which did not measure pedalling rate or basal VO,, the mean mechanical efficiency for the spastic group would have been 0 . 7 per cent lower. Berg (1970), in bicycle ergometer tests, did not note any differences in mechanical efficiency between the two types of cerebral palsy. The reason may be the differences in composition, diagnostic criteria and ages of the subjects in her study and in our own. In our study, the inclusion of measurements of pedalling rates and basal V O , produced a mean mechanical efficiency for the dyskinetic/ataxic group which was 8.5 per cent higher than if it had been assumed that the people in this group pedalled at 50rpm and had a basal VO, in accordance with the values predicted for non-handicapped people. There was an uneven sex distribution between our handicapped groups, but this is unlikely to have influenced the results since in able-bodied people it has been shown that women have a somewhat lower oxygen intake at a given work-load than do men (Astrand and Rodahl 1970). This is also in agreement with the results in our control group, in which three women had a mean mechanical efficiency of 22.7 per cent, compared with 21 ' 7 per cent for the men. There were similar degrees of disability in our two handicapped groups, in that severe handicap was a necessity for their attending a special school but the handicap
DEVELOPMENTAL MEDICINE AND CHILD NEUROLOGY.
was not severe enough to prevent them performing the bicycle ergometer tests. Within this range, of course, there were variations in the degree of handicap. Patients with dyskinesia often have better function in the legs than in the arms, in contrast to those with spastic diplegia whose equilibration reactions are decreased, resulting in impaired walking ability. These differences in motor performance are closely connected to the type of cerebral palsy and only indirectly influence the observed difference in mechanical efficiency between the two groups. It is
1975. 17
reasonable to conclude, therefore, that the lower mechanical efficiency in the spastic group compared with the dyskineticl ataxic group is explained by the extra amount of energy required to overcome the constant increase in muscle tonus during the bicycle ergometer tests. In the dyskineticlataxic group, on the other hand, less extra energy expenditure was required during the tests. Acknowledgement: This study was carried out with grants from Foreningen for bistHnd Bt lytta och vanfora, Stockholm, and H. K. H. Kronprinsessan Lovisas forening for barnasjukvsrd, Stockholm.
SUMMARY
This study used a method specifically adapted to motor handicap, one which measured pedalling rate and basal oxygen consumption. Its aim was to investigate whether bicycle ergometer work could distinguish any difference in mechanical efficiency between two groups with cerebral palsy. 10 patients aged between 18 and 30 years (six dyskineticlataxic, four spastic) were studied. Six non-handicapped young adults formed a control group. The results showed a highly significant difference between the dyskinetic/ataxic group and the spastic group. Results for the dyskinetic/ataxic group and the control group did not differ significantlyfrom those obtained for a normal population. The observed difference between the two groups with cerebral palsy seems to be the result of the greater amount of energy required to be expended by the spastic group in order to overcome the constant increase in muscle tone during the bicycle ergometer test.
RGSUML Eficience tnkcanique dans un travail de bicyclerte ergomktrique chez de jeunes adultes IMC En utilisant une rnkthode sptcialement adaptee au handicap moteur qui mesure le taux de pedalage et la consommation de base d‘oxyghe, le but de cette etude a cite de chercher si le travail sur bicyclette ergometrique pouvait reveler une difference d’efficience mecanique entre deux types d’mc. 10 sujets de 18 B 30 ans dont six avec une forme ~ I M Cdu type dyskinttiquelataxique et quatre du type spastique ont ete etudies. Un groupe contrble a it6 constitue par six jeunes adultes non handicapes. Le resultat a montrk une difference hautement significative entre les groupes dyskinetique/ ataxique et spastique. Les risultats du groupe dyskinitique/ataxique et du groupe contr6le ne diff6rent pas significativement de ceux d’une population normale. La diffirence observCe entre les deux groupes IMC parait la consequence de la plus grande quantite d’energie necessitee par le groupe spastique pour surmonter I’accroissement constant de tonus musculaire durant le travail sur bicyclette ergomttrique. 438
A K t LUNDBERG
ZUSAMMENFASSUNG
Mecliunisclie Efizienz der Falirrarlergometerarheit hei jirngen Erwdisenen mit Cerrhralparese Unter Anwendung einer speziell fur motorische Behinderung abgestimmten Methode. mit der die Tretrate und der basale Sauerstoffverbrauch gemessen werden, war es das Ziel dieser Studie zu untersuchen, ob durch Fahrradergometerarbeit irgendein Unterschied bei der mechanischen Effizienz zwischen zwei Typen der Cerebralparese zu finden war. 10 Patienten (im Alter von 18 bis 30 Jahren) wurden untersucht, davon hatten sechs eine Cerebralparese vom dyskinetisch-ataktischen Typ und vier eine Cerebralparese vom spastischen Typ. Sechs unbehinderte junge Erwachsene bildeten die Kontrollgruppe. Die Ergebnisse zeigten einen hoch signifikanten Unterschied ( p
