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The decline of aerobic capacity and muscle strength following fractures of the lower limb
Injury, 11, 219-224
Printed in Great Britain
219
The decline of aerobic capacity and muscle strength following fractures of the lower limb F. J. Imms and S. P. Prestidge Medical Research Council Environmental Physiology Unit
F. B. Mayes Cambridge Military Hospital Aldershot
Summary
Aerobic capacities and muscle strengths of the uninjured limbs have been measured in patients who had suffered fractures of the lower limb. In patients treated in plaster-of-Paris aerobic capacity and strength fell rapidly following injury, to an extent greater than might be expected as a result of resting in bed. Before removal of the plaster-of-Paris, both aerobic capacity and strength had improved. Further improvement occurred in the uninjured limb after resuming use of the injured limb. In patients treated by traction and thus subjected to long periods in bed, the reductions of aerobic capacity and strength, measured shortly after resuming movements, were more profound than in patients treated with plaster-of-Paris. INTRODUCTION ELECTIVE operation temporarily reduces the aerobic capacity of previously healthy individuals (Adolfsson, 1969; Carswell, 1975). This reduction may result from both the effects of surgical injury per se and the associated rest in bed, since confinement of healthy individuals to bed lowers their aerobic capacities (Saltin et al., 1968; Stremel et al., 1976). This change has now been examined in young males who have fractured a lower limb. Patients who had suffered fractures of the shafts of the tibia and fibula or fracture-dislocations of the ankle were usually confined to bed for less than one week. This period was extended if the injury was complicated or the fracture required operative fixation. During the period in bed, the
injured leg was encased in a plaster-of-Paris splint. When this had hardened, the patients were allowed to walk with the aid of crutches. Those patients who had fractures of the femur were treated either by traction alone or by a combination of traction and internal fixation. These treatments required prolonged rest in bed and provided the opportunity to study the physiological effects of prolonged confinement to bed. patients some fifty days after removal of plasterof-Paris or cessation of traction demonstrated reductions of aerobic capacity (Davies and Sargeant, 1975a). The measurements were made during exercise on a bicycle ergometer. At this stage of recovery, most patients were able to cycle using both legs, and maximal oxygen uptake (~o 2 max) was determined in the conventional manner. During one-leg cycling it was shown that the 9o~ max of each limb was reduced at this stage of recovery. Since a patient with a limb encased in plaster-of-Paris can exercise only with the uninjured limb, this one was employed at all stages of the present investigation. For reasons which will be elaborated in the discussion, the oxygen uptake so determined will be considered to represent the function of this limb rather than of the whole body. Limb function was additionally assessed by measurement of maximal voluntary isometric tension ('strength') of the extensor and flexor muscles of .the knee joint and the dorsiflexors of the ankle.
220
Injury: the British Journal of Accident Surgery Vol. 1 1/No. 3
TableL Biographical details (mean ± sd)
Details
Subjects treated in POP
Subjects treated by traction
n
38
Age I nju red side Right Left Internal fixation Initial inpatient treatment (days) Period of immobilization (days) Unfixed Fixed Interval from mobilization until discharge (days) Total t r e a t m e n t time (injury to discharge) (days)
21 + 5
18 24 + 6
21 17 16 2 4 _ 15
8 10 8 8 4 _+ 9
102 ± 4 4 1 0 0 _+ 4 8
103 _+ 4 4 4 0 _+ 2 2
75 _+ 52
116 +__59
176 __ 71
2 1 6 _+ 49
POP, plaster-of-Paris.
PATIENTS A N D M E T H O D S The subjects were 56 young men aged 16-36 years. Of these, 38 had suffered fractures of the shafts of the tibia and fibula, or fractures involving the ankle joint which required immobilization with plaster-of-Paris; 18 had suffered fractures of the femur and were treated by traction. They were all admitted as emergencies to the Cambridge Military Hospital, Aldershot. Particulars of the patients, their treatments, the time spent in hospital and immobilization are given in Table I. A complete set of tests was not performed on each subject at all stages of the investigation. Exercise and strength testing for patients treated in plaster-of-Paris was begun as soon as possible after the period spent resting in bed. Tests were repeated when the patient returned to hospital a few days before or after removal of the plaster-of-Paris and at the completion of treatment. No testing was possible during traction for those patients treated by this method. Estimates of muscle strength and aerobic capacity were made before leaving hospital (within 30 days of ceasing traction) and repeated when treatment was completed. Exercise testing The patients exercised on a Monark bicycle ergometer, using only the injured leg. Pedalling was facilitated by fixing a shoe to the pedal with screws and tying the foot firmly into the shoe.
The injured leg, when in plaster-of-Paris, was supported on a splint attached to the bicycle frame. The subject was asked to pedal at 60 rpm, initially with zero braking on the fly-wheel, and subsequently at a minimum of 3 work loads. The test was continuous, with work loads increased every 5 minutes until the heart beats exceeded 160 per minute. The test was immediately stopped if the patient felt unable to continue. During the last 2 minutes of each work load, expired air was collected in a Douglas bag and an electrocardiogram measured the heart rate. The oxygen content of the expired air (x) was measured using a Servomex analyser. The measurement was repeated (x~) following removal of co 2 with soda lime, and the co 2 content (y) calculated by the formula: y = 100(1 -x/xl) Regression lines were calculated for oxygen consumption and heart rate. Indices of submaximal aerobic capacity were calculated as oxygen consumption at heart rate 140 (~,02 ~4o) and as heart rate at oxygen consumption 1"4 l/min (HR~.4). Mechanical efficiency of exercise was assessed by calculation of ~,02 against mechanical work performed on the bicycle. The oxygen consumption at a work rate of 450 kg/m/min was interpolated (x?o2 450). From this was subtracted the #0 z at zero work load to give net 902 450. Strength testing The strengths of the extensor and flexor muscles
Imms et al.: Lower Limb Fractures
221
Table II. Submaximal aerobic capacity during one-leg cycling (mean ± sd) in patients treated with plaster-of-Paris
n ~0214o(1 min -t)
HRI4 ~0;45o net (1 min -~)
/n POP ( < 20 days)
Ex POP
Discharge
(a)
(b)
(c)
12 1"300 ___0"250 146"1_+14"5 0 ' 9 8 4 ___0 ' 1 4 9
15 1'458 ± 0 " 2 3 2 t 138"8 __ 13"5t 0"956 _+. 0"140
10 1"679 ___0"285" 129"3___11"7 ° 0'941 _+_0"081
POP, plaster-of-Paris; by paired "t'tests: t P < 0"05 (a.v.b), "P < 0.05 (a.v.c)
Table II1. Submaximal aerobic capacity during one-leg cycling (mean ± sd) in patients treated by traction
n ~0~ a4o(1 min -t) HR,.4 ~0245o net (1 rain -t)
Ex traction (a)
Discharge (b)
5 1'166 ___0 - 1 2 7 t 154'1 -+ 8"4t 1"035 ± 0"114
5 1"546 ± 0 - 2 7 9 t 133'6 ___ 13"0 ° 0"948 ___0"095
tSignificantly different (P < 0-01 ) from Table II column (b). °Significant difference (P < 0"01 ) (a v. b).
Table IV. Submaximal aerobic capacity during one-leg cycling (mean + sd) in uninjured subjects Davies and Sargeant (1974b)
Freyschuss and Strandell (1968)
5 1"77 121 0'92
9 1 "61 132 1 "08
n
402140(1 min -I) H Rt.4 ~/02450net ( 1 rain -I)
of the knee and dorsiflexors of the ankle were measured using a modified strain gauge dynamometer (Imms et al., 1977). RESULTS Since control data on aerobic capacity and muscle strength before injury are not available, data obtained following injury must be compared with those obtained at the end of treatment when the patient was considered fit for discharge from further medical supervision. Measurements made within 20 days of injury show that following fractures of the lower leg
which required immobilization in plaster-ofParis there were marked reductions of submaximal aerobic capacity of the uninjured leg as indicated by a low value for ~,02 ~40 and raised HRs.4 (Tables II, III and IV). There were also considerable reductions of strength of the extensor and flexor muscles of the knee and smaller, though statistically significant, reductions of strength of the dorsiflexors of the ankle (Tables V, VI and VII). Repeat determinations of strength made between 21 and 50 days after injury with the patients walking with crutches, showed slight improvements of strength of the
222
Injury: the British Journal of Accident Surgery Vol. 11/No. 3
Table V. Muscle strength of uninjured leg during recovery from fracture of the l o w e r limb (kg/cm; mean _ sd) in patients treated with plaster-of-Paris
n Dorsiflexion of ankle Knee extension Knee flexion
In POP ( < 2 0 days) (a)
In POP ( 2 1 - 5 0 days) (b)
Ex POP
Discharge
,(c)
(d)
19 4 9 2 _+ 105 1 6 3 5 _+ 4 9 5 9 0 5 _+_2 9 4
16 4 9 5 _+ 71 1 8 7 9 _+ 3 7 6 9 1 0 0 8 _+ 58
26 5 3 0 _+ 1 0 8 1981 _ 3 5 6 t 1235 _ 234t
26 5 7 0 _+ 1 2 0 " 2158 _ 423* 1 3 2 8 _+ 2 1 6 "
POP, plaster-of-Paris; by paired "t'tests: ~P < 0"05 (a.v.b), t P < 0"05 (a.v.c), °P < 0.05 (a.v.d)
Table Vl. Muscle strength of uninjured leg during recovery from fracture of the lower limb (kg/cm; mean __ sd) in patients treated by traction
n Dorsiflexion of ankle Knee extension Knee flexion
Ex traction ( < 2 0 days) (a)
Discharge
15 403 _ 112t 1 5 4 0 _+ 4 1 4 t 8 7 7 _+ 1 5 7 t
13 5 1 0 _+ 95"6" 2063 _ 530* 1 1 3 6 _+ 2 0 5 "
(a)
tSignificantly different (P < 0 ' 0 0 1 ) from Table V c o l u m n (c). *by paired "t'test: P < 0"05 (a.v.b).
Table VII. Muscle strength of normal subjects* (kg/cm; mean _+ sd) Normal subjects Dorsiflexion of ankle Knee extension Knee flexion
5 4 0 _+ 80 1 5 5 0 __ 2 8 0 1 3 0 0 _+ 2 1 0
*(Laubach, 1976).
extensors and flexors of the knee. Measurements of aerobic capacity and strength made within a few days of removal of the plaster-of-Paris showed significant improvements of limb function compared with those immediately after injury. Further improvements of both aerobic capacity and strength occurred between removal of the plaster-of-Paris and discharge from medical supervision. Those patients treated by traction were confined to bed for long periods. After cessation of traction both the aerobic capacity and strength of the uninjured limb were considerably lower than following removal of the plaster-ofParis. The increases of strength between
cessation of traction and discharge were greater than the corresponding increases following removal of the plaster-of-Paris, even when the different time intervals are taken into account. The efficiency of working, as demonstrated by ~'024~0 net, did not vary at the different stages of recovery. This efficiency was of the order of 22 per cent. DISCUSSION
Physical fitness has traditionally been assessed by exercising the subject on a bicycle ergometer or a motorized treadmill and measuring his oxygen uptake. It has recently been suggested that the fitness of a subject with a leg injury could be assessed by determination of oxygen uptake and heart rate when working with one leg (Bassey et al., 1973; Bassey and Goldsmith, 1975). The validity of this approach requires careful consideration. Studies on normal subjects show that ~o 2 max determined with one leg working exceeds 70 per cent of the value with two legs working (Davies and Sargeant, 1974a, 1975b). It is likely that the limiting factor with two-leg exercise is the cardiac output, whereas with one-leg work it is the local ability of the limb to utilize oxygen, the
Imms et al.: Lower Limb Fractures
supply of which may not be critical. This view is supported by the findings that arteriovenous oxygen difference in the limb is greater with two legs working than with one (Freyschuss and Strandell, 1968), that increasing the partial pressure of oxygen in inspired air increases twoleg ~'o~ max, but not one-leg #o 2 max (Davies and Sargeant, 1974b) and that the training of one leg increases qzo2 max with one leg working but not with two legs working (Davies and Sargeant, 1975b). VO2 max for working with two legs may be calculated from data obtained with one leg working (Davies and Sargeant, 1974a), but such calculations for injured subjects in which muscle mass of the two legs may be different are subject to considerable errors (Davies and Sargeant 1975c). The most valid interpretation of one-leg 402 measurements is that they represent the work performance of the limb on which they are measured, and give only a general indication of central cardiovascular function. The same general reservation should be placed on the findings of Bassey et al. (1973). A relevant need was to establish control values because no data were available before injury. The only practicable method of control was to use data obtained at the end of treatment. Values for ~,o2140 and HRI.4 obtained at this time were similar to those obtained for uninjured subjects (Table IV) (Freyschuss and Strandell, 1968; Davies and Sargeant, 1974b). The strengths of knee extensors and flexors and of ankle dorsiflexors of patients treated in plaster-of-Paris slightly exceeded values given by Laubach (1976). For patients treated by traction, whilst the strength of knee extensors exceeded the value quoted by Laubach (1976), the strength of the knee flexors was lower. There appear to be three factors contributing to reductions of strength and aerobic capacity of patients following fractures of lower limbs. These are the metabolic response to the injury, confinement to bed and reduced activity whilst up and about. Fracture of a limb, in common with other injuries, results in prolonged catabolism of protein, as exemplified by increased urinary excretion of nitrogen (Davies, 1970). Studies by Bassey et al. (1973) on patients four days after meniscectomy and by Carswell (1975) four days after laparotomy showed marked reductions of one- and two-leg aerobic capacities. However, by fourteen days after meniscectomy the aerobic capacity of the uninjured limb was improved despite the patient remaining in
223
bed. It appears that injury has a specific effect on aerobic capacity in addition to that of the associated rest in bed. Thus Stremel et al. (1976) quote twelve studies in which confinement to bed from 4 to 20 days caused a mean reduction in ~,o~ max of 7"5 per cent. In the present studies on fractures of lower limbs few subjects were confined to bed for longer than 20 days, yet the reduction of#o 2 ~4owas 22"6 per cent. The five subjects treated by traction, on whom studies of aerobic capacity were performed, were confined to bed for 100 days (range 43-178). To our knowledge, there are no studies in the literature describing the physiological effects of such a long time in bed. When the patients got up again, both the aerobic capacity and the muscle strength of the uninjured limb were lower than those of the patients who had been treated in plaster-of-Paris. Since the degree of damage suffered by the two groups was similar, and hence the catabolic effect the same, being up and about whilst in plaster-of-Paris appears to have a highly beneficial effect on both static and dynamic work capacities of the uninjured limb.
Acknowledgements The authors wish to thank the Commandant of the Cambridge Military Hospital for providing research facilities and for allowing us to study patients under his command. REFERENCES
Adolfsson G. (1969) Rehabilitation and convalescence after surgery. Scand. J. Rehabil. Med. 1,14. Bassey E. J., Bennett T., Birmingham A. T. et al. (1973) Effects of surgical operation and bedrest on cardiovascular responses to exercise in hospital patients. Cardiovasc. Res. 7, 588. Bassey E. J. and Goldsmith R. (1975) One-legged pedalling compared with two-legged pedalling on a bicycle ergometer as a basis for assessing physical condition in terms of the cardio-respiratory response to exercise. Scand. J. Rehabil. Med. 7, 32. Carswell S. (1975) Changes in aerobic power in patients undergoingelective surgery. J. Physiol. 251, 42. Davies C. T. M. and Sargeant A. J. (1974a) Indirect determination of maximal aerobic power output during work with one or two limbs. Eur. J. Appl. Physiol. 32,207. Davies C. T. M. and Sargeant A. J. (1974b) Physiological responses to one- and two-leg exercise breathing air and 45 per cent oxygen. J. Appl. Physiol. 36, 142. Davies C. T. M. and Sargeant A. J. (1975a) Physiological responses to exercise in patients following fracture of the lower limb. Scand. J. Rehabil. Meal. 7, 45.
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Injury: the British Journal of Accident Surgery Vol. 11/No. 3
Davies C. T. M. and Sargeant A. J. (1975b) Effects of training on the physiological responses to one- and two-leg work. J. Appl. Physiol. 37, 377. Davies C. T. M. and Sargeant A. J. (1975c) Aerobic power prediction in patients recovering from limb injury. Arch. Phys. Med. Rehabil. 56, 340. Davies J. W. L. (1970) Protein metabolism following injury. J. Clin. Pathol. 23, Suppl. 4, 56. Freyschuss U. and Strandell T. (1968) Circulatory adaptation to one- and two-leg exercise in supine position. J. Appl. Physiol. 25, 5 i 1. Imms F. J., Hackett A. J., Prestidge S. P. et al. (1977) Voluntary isometric muscle strength of patients
undergoing rehabilitation following fractures of the lower limb. Rheumatol. Rehabil. 16, 162. Laubach L. L. (1976) Comparative muscular strength of men and women: a review of the literature. Aviat. Space Environ. Med. 47, 534. Saltin B., Blomquist G., Mitchell J. B. et al. (1968) Response to exercise after bed rest and after training. Circulation 38, Suppl. 1, 1. Stremel R. W., Convertino V. A., Bernauer E. M. et al. (1976) Cardiorespiratory deconditioning with static and dynamic leg exercise during bed rest. J. Appl. Physiol. 41,905.
Requestsfor reprintsshould be addressed to: Dr F. J. imms, MRC Environmental PhysiologyUnit (Annexe), 242 Pentonville Road, London, NI 9LB.
Printed in Great Britain
219
The decline of aerobic capacity and muscle strength following fractures of the lower limb F. J. Imms and S. P. Prestidge Medical Research Council Environmental Physiology Unit
F. B. Mayes Cambridge Military Hospital Aldershot
Summary
Aerobic capacities and muscle strengths of the uninjured limbs have been measured in patients who had suffered fractures of the lower limb. In patients treated in plaster-of-Paris aerobic capacity and strength fell rapidly following injury, to an extent greater than might be expected as a result of resting in bed. Before removal of the plaster-of-Paris, both aerobic capacity and strength had improved. Further improvement occurred in the uninjured limb after resuming use of the injured limb. In patients treated by traction and thus subjected to long periods in bed, the reductions of aerobic capacity and strength, measured shortly after resuming movements, were more profound than in patients treated with plaster-of-Paris. INTRODUCTION ELECTIVE operation temporarily reduces the aerobic capacity of previously healthy individuals (Adolfsson, 1969; Carswell, 1975). This reduction may result from both the effects of surgical injury per se and the associated rest in bed, since confinement of healthy individuals to bed lowers their aerobic capacities (Saltin et al., 1968; Stremel et al., 1976). This change has now been examined in young males who have fractured a lower limb. Patients who had suffered fractures of the shafts of the tibia and fibula or fracture-dislocations of the ankle were usually confined to bed for less than one week. This period was extended if the injury was complicated or the fracture required operative fixation. During the period in bed, the
injured leg was encased in a plaster-of-Paris splint. When this had hardened, the patients were allowed to walk with the aid of crutches. Those patients who had fractures of the femur were treated either by traction alone or by a combination of traction and internal fixation. These treatments required prolonged rest in bed and provided the opportunity to study the physiological effects of prolonged confinement to bed. patients some fifty days after removal of plasterof-Paris or cessation of traction demonstrated reductions of aerobic capacity (Davies and Sargeant, 1975a). The measurements were made during exercise on a bicycle ergometer. At this stage of recovery, most patients were able to cycle using both legs, and maximal oxygen uptake (~o 2 max) was determined in the conventional manner. During one-leg cycling it was shown that the 9o~ max of each limb was reduced at this stage of recovery. Since a patient with a limb encased in plaster-of-Paris can exercise only with the uninjured limb, this one was employed at all stages of the present investigation. For reasons which will be elaborated in the discussion, the oxygen uptake so determined will be considered to represent the function of this limb rather than of the whole body. Limb function was additionally assessed by measurement of maximal voluntary isometric tension ('strength') of the extensor and flexor muscles of .the knee joint and the dorsiflexors of the ankle.
220
Injury: the British Journal of Accident Surgery Vol. 1 1/No. 3
TableL Biographical details (mean ± sd)
Details
Subjects treated in POP
Subjects treated by traction
n
38
Age I nju red side Right Left Internal fixation Initial inpatient treatment (days) Period of immobilization (days) Unfixed Fixed Interval from mobilization until discharge (days) Total t r e a t m e n t time (injury to discharge) (days)
21 + 5
18 24 + 6
21 17 16 2 4 _ 15
8 10 8 8 4 _+ 9
102 ± 4 4 1 0 0 _+ 4 8
103 _+ 4 4 4 0 _+ 2 2
75 _+ 52
116 +__59
176 __ 71
2 1 6 _+ 49
POP, plaster-of-Paris.
PATIENTS A N D M E T H O D S The subjects were 56 young men aged 16-36 years. Of these, 38 had suffered fractures of the shafts of the tibia and fibula, or fractures involving the ankle joint which required immobilization with plaster-of-Paris; 18 had suffered fractures of the femur and were treated by traction. They were all admitted as emergencies to the Cambridge Military Hospital, Aldershot. Particulars of the patients, their treatments, the time spent in hospital and immobilization are given in Table I. A complete set of tests was not performed on each subject at all stages of the investigation. Exercise and strength testing for patients treated in plaster-of-Paris was begun as soon as possible after the period spent resting in bed. Tests were repeated when the patient returned to hospital a few days before or after removal of the plaster-of-Paris and at the completion of treatment. No testing was possible during traction for those patients treated by this method. Estimates of muscle strength and aerobic capacity were made before leaving hospital (within 30 days of ceasing traction) and repeated when treatment was completed. Exercise testing The patients exercised on a Monark bicycle ergometer, using only the injured leg. Pedalling was facilitated by fixing a shoe to the pedal with screws and tying the foot firmly into the shoe.
The injured leg, when in plaster-of-Paris, was supported on a splint attached to the bicycle frame. The subject was asked to pedal at 60 rpm, initially with zero braking on the fly-wheel, and subsequently at a minimum of 3 work loads. The test was continuous, with work loads increased every 5 minutes until the heart beats exceeded 160 per minute. The test was immediately stopped if the patient felt unable to continue. During the last 2 minutes of each work load, expired air was collected in a Douglas bag and an electrocardiogram measured the heart rate. The oxygen content of the expired air (x) was measured using a Servomex analyser. The measurement was repeated (x~) following removal of co 2 with soda lime, and the co 2 content (y) calculated by the formula: y = 100(1 -x/xl) Regression lines were calculated for oxygen consumption and heart rate. Indices of submaximal aerobic capacity were calculated as oxygen consumption at heart rate 140 (~,02 ~4o) and as heart rate at oxygen consumption 1"4 l/min (HR~.4). Mechanical efficiency of exercise was assessed by calculation of ~,02 against mechanical work performed on the bicycle. The oxygen consumption at a work rate of 450 kg/m/min was interpolated (x?o2 450). From this was subtracted the #0 z at zero work load to give net 902 450. Strength testing The strengths of the extensor and flexor muscles
Imms et al.: Lower Limb Fractures
221
Table II. Submaximal aerobic capacity during one-leg cycling (mean ± sd) in patients treated with plaster-of-Paris
n ~0214o(1 min -t)
HRI4 ~0;45o net (1 min -~)
/n POP ( < 20 days)
Ex POP
Discharge
(a)
(b)
(c)
12 1"300 ___0"250 146"1_+14"5 0 ' 9 8 4 ___0 ' 1 4 9
15 1'458 ± 0 " 2 3 2 t 138"8 __ 13"5t 0"956 _+. 0"140
10 1"679 ___0"285" 129"3___11"7 ° 0'941 _+_0"081
POP, plaster-of-Paris; by paired "t'tests: t P < 0"05 (a.v.b), "P < 0.05 (a.v.c)
Table II1. Submaximal aerobic capacity during one-leg cycling (mean ± sd) in patients treated by traction
n ~0~ a4o(1 min -t) HR,.4 ~0245o net (1 rain -t)
Ex traction (a)
Discharge (b)
5 1'166 ___0 - 1 2 7 t 154'1 -+ 8"4t 1"035 ± 0"114
5 1"546 ± 0 - 2 7 9 t 133'6 ___ 13"0 ° 0"948 ___0"095
tSignificantly different (P < 0-01 ) from Table II column (b). °Significant difference (P < 0"01 ) (a v. b).
Table IV. Submaximal aerobic capacity during one-leg cycling (mean + sd) in uninjured subjects Davies and Sargeant (1974b)
Freyschuss and Strandell (1968)
5 1"77 121 0'92
9 1 "61 132 1 "08
n
402140(1 min -I) H Rt.4 ~/02450net ( 1 rain -I)
of the knee and dorsiflexors of the ankle were measured using a modified strain gauge dynamometer (Imms et al., 1977). RESULTS Since control data on aerobic capacity and muscle strength before injury are not available, data obtained following injury must be compared with those obtained at the end of treatment when the patient was considered fit for discharge from further medical supervision. Measurements made within 20 days of injury show that following fractures of the lower leg
which required immobilization in plaster-ofParis there were marked reductions of submaximal aerobic capacity of the uninjured leg as indicated by a low value for ~,02 ~40 and raised HRs.4 (Tables II, III and IV). There were also considerable reductions of strength of the extensor and flexor muscles of the knee and smaller, though statistically significant, reductions of strength of the dorsiflexors of the ankle (Tables V, VI and VII). Repeat determinations of strength made between 21 and 50 days after injury with the patients walking with crutches, showed slight improvements of strength of the
222
Injury: the British Journal of Accident Surgery Vol. 11/No. 3
Table V. Muscle strength of uninjured leg during recovery from fracture of the l o w e r limb (kg/cm; mean _ sd) in patients treated with plaster-of-Paris
n Dorsiflexion of ankle Knee extension Knee flexion
In POP ( < 2 0 days) (a)
In POP ( 2 1 - 5 0 days) (b)
Ex POP
Discharge
,(c)
(d)
19 4 9 2 _+ 105 1 6 3 5 _+ 4 9 5 9 0 5 _+_2 9 4
16 4 9 5 _+ 71 1 8 7 9 _+ 3 7 6 9 1 0 0 8 _+ 58
26 5 3 0 _+ 1 0 8 1981 _ 3 5 6 t 1235 _ 234t
26 5 7 0 _+ 1 2 0 " 2158 _ 423* 1 3 2 8 _+ 2 1 6 "
POP, plaster-of-Paris; by paired "t'tests: ~P < 0"05 (a.v.b), t P < 0"05 (a.v.c), °P < 0.05 (a.v.d)
Table Vl. Muscle strength of uninjured leg during recovery from fracture of the lower limb (kg/cm; mean __ sd) in patients treated by traction
n Dorsiflexion of ankle Knee extension Knee flexion
Ex traction ( < 2 0 days) (a)
Discharge
15 403 _ 112t 1 5 4 0 _+ 4 1 4 t 8 7 7 _+ 1 5 7 t
13 5 1 0 _+ 95"6" 2063 _ 530* 1 1 3 6 _+ 2 0 5 "
(a)
tSignificantly different (P < 0 ' 0 0 1 ) from Table V c o l u m n (c). *by paired "t'test: P < 0"05 (a.v.b).
Table VII. Muscle strength of normal subjects* (kg/cm; mean _+ sd) Normal subjects Dorsiflexion of ankle Knee extension Knee flexion
5 4 0 _+ 80 1 5 5 0 __ 2 8 0 1 3 0 0 _+ 2 1 0
*(Laubach, 1976).
extensors and flexors of the knee. Measurements of aerobic capacity and strength made within a few days of removal of the plaster-of-Paris showed significant improvements of limb function compared with those immediately after injury. Further improvements of both aerobic capacity and strength occurred between removal of the plaster-of-Paris and discharge from medical supervision. Those patients treated by traction were confined to bed for long periods. After cessation of traction both the aerobic capacity and strength of the uninjured limb were considerably lower than following removal of the plaster-ofParis. The increases of strength between
cessation of traction and discharge were greater than the corresponding increases following removal of the plaster-of-Paris, even when the different time intervals are taken into account. The efficiency of working, as demonstrated by ~'024~0 net, did not vary at the different stages of recovery. This efficiency was of the order of 22 per cent. DISCUSSION
Physical fitness has traditionally been assessed by exercising the subject on a bicycle ergometer or a motorized treadmill and measuring his oxygen uptake. It has recently been suggested that the fitness of a subject with a leg injury could be assessed by determination of oxygen uptake and heart rate when working with one leg (Bassey et al., 1973; Bassey and Goldsmith, 1975). The validity of this approach requires careful consideration. Studies on normal subjects show that ~o 2 max determined with one leg working exceeds 70 per cent of the value with two legs working (Davies and Sargeant, 1974a, 1975b). It is likely that the limiting factor with two-leg exercise is the cardiac output, whereas with one-leg work it is the local ability of the limb to utilize oxygen, the
Imms et al.: Lower Limb Fractures
supply of which may not be critical. This view is supported by the findings that arteriovenous oxygen difference in the limb is greater with two legs working than with one (Freyschuss and Strandell, 1968), that increasing the partial pressure of oxygen in inspired air increases twoleg ~'o~ max, but not one-leg #o 2 max (Davies and Sargeant, 1974b) and that the training of one leg increases qzo2 max with one leg working but not with two legs working (Davies and Sargeant, 1975b). VO2 max for working with two legs may be calculated from data obtained with one leg working (Davies and Sargeant, 1974a), but such calculations for injured subjects in which muscle mass of the two legs may be different are subject to considerable errors (Davies and Sargeant 1975c). The most valid interpretation of one-leg 402 measurements is that they represent the work performance of the limb on which they are measured, and give only a general indication of central cardiovascular function. The same general reservation should be placed on the findings of Bassey et al. (1973). A relevant need was to establish control values because no data were available before injury. The only practicable method of control was to use data obtained at the end of treatment. Values for ~,o2140 and HRI.4 obtained at this time were similar to those obtained for uninjured subjects (Table IV) (Freyschuss and Strandell, 1968; Davies and Sargeant, 1974b). The strengths of knee extensors and flexors and of ankle dorsiflexors of patients treated in plaster-of-Paris slightly exceeded values given by Laubach (1976). For patients treated by traction, whilst the strength of knee extensors exceeded the value quoted by Laubach (1976), the strength of the knee flexors was lower. There appear to be three factors contributing to reductions of strength and aerobic capacity of patients following fractures of lower limbs. These are the metabolic response to the injury, confinement to bed and reduced activity whilst up and about. Fracture of a limb, in common with other injuries, results in prolonged catabolism of protein, as exemplified by increased urinary excretion of nitrogen (Davies, 1970). Studies by Bassey et al. (1973) on patients four days after meniscectomy and by Carswell (1975) four days after laparotomy showed marked reductions of one- and two-leg aerobic capacities. However, by fourteen days after meniscectomy the aerobic capacity of the uninjured limb was improved despite the patient remaining in
223
bed. It appears that injury has a specific effect on aerobic capacity in addition to that of the associated rest in bed. Thus Stremel et al. (1976) quote twelve studies in which confinement to bed from 4 to 20 days caused a mean reduction in ~,o~ max of 7"5 per cent. In the present studies on fractures of lower limbs few subjects were confined to bed for longer than 20 days, yet the reduction of#o 2 ~4owas 22"6 per cent. The five subjects treated by traction, on whom studies of aerobic capacity were performed, were confined to bed for 100 days (range 43-178). To our knowledge, there are no studies in the literature describing the physiological effects of such a long time in bed. When the patients got up again, both the aerobic capacity and the muscle strength of the uninjured limb were lower than those of the patients who had been treated in plaster-of-Paris. Since the degree of damage suffered by the two groups was similar, and hence the catabolic effect the same, being up and about whilst in plaster-of-Paris appears to have a highly beneficial effect on both static and dynamic work capacities of the uninjured limb.
Acknowledgements The authors wish to thank the Commandant of the Cambridge Military Hospital for providing research facilities and for allowing us to study patients under his command. REFERENCES
Adolfsson G. (1969) Rehabilitation and convalescence after surgery. Scand. J. Rehabil. Med. 1,14. Bassey E. J., Bennett T., Birmingham A. T. et al. (1973) Effects of surgical operation and bedrest on cardiovascular responses to exercise in hospital patients. Cardiovasc. Res. 7, 588. Bassey E. J. and Goldsmith R. (1975) One-legged pedalling compared with two-legged pedalling on a bicycle ergometer as a basis for assessing physical condition in terms of the cardio-respiratory response to exercise. Scand. J. Rehabil. Med. 7, 32. Carswell S. (1975) Changes in aerobic power in patients undergoingelective surgery. J. Physiol. 251, 42. Davies C. T. M. and Sargeant A. J. (1974a) Indirect determination of maximal aerobic power output during work with one or two limbs. Eur. J. Appl. Physiol. 32,207. Davies C. T. M. and Sargeant A. J. (1974b) Physiological responses to one- and two-leg exercise breathing air and 45 per cent oxygen. J. Appl. Physiol. 36, 142. Davies C. T. M. and Sargeant A. J. (1975a) Physiological responses to exercise in patients following fracture of the lower limb. Scand. J. Rehabil. Meal. 7, 45.
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Davies C. T. M. and Sargeant A. J. (1975b) Effects of training on the physiological responses to one- and two-leg work. J. Appl. Physiol. 37, 377. Davies C. T. M. and Sargeant A. J. (1975c) Aerobic power prediction in patients recovering from limb injury. Arch. Phys. Med. Rehabil. 56, 340. Davies J. W. L. (1970) Protein metabolism following injury. J. Clin. Pathol. 23, Suppl. 4, 56. Freyschuss U. and Strandell T. (1968) Circulatory adaptation to one- and two-leg exercise in supine position. J. Appl. Physiol. 25, 5 i 1. Imms F. J., Hackett A. J., Prestidge S. P. et al. (1977) Voluntary isometric muscle strength of patients
undergoing rehabilitation following fractures of the lower limb. Rheumatol. Rehabil. 16, 162. Laubach L. L. (1976) Comparative muscular strength of men and women: a review of the literature. Aviat. Space Environ. Med. 47, 534. Saltin B., Blomquist G., Mitchell J. B. et al. (1968) Response to exercise after bed rest and after training. Circulation 38, Suppl. 1, 1. Stremel R. W., Convertino V. A., Bernauer E. M. et al. (1976) Cardiorespiratory deconditioning with static and dynamic leg exercise during bed rest. J. Appl. Physiol. 41,905.
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