- Email: [email protected]
Effects of ankle disc training on muscular strength and postural control
Clinical Biomechanics
1988; 3: 88-91
Effects of ankle disc training on muscular strength and postural control Hans Tropp Carl Askling Departments
MD RPT
of Clinical Neurophysiology
and Orthopaedic
Surgery, University Hospital, Linkdping, Sweden
Summary Ankle disc training gave good objective results in patients with functional instability of the ankle joint, that is a feeling of giving way or recurrent sprains. The training programme improved both postural control, as demonstrated by stabilometry, and isokinetic pronator muscle strength. A lo-week training period was apparently sufficient, and further training could not be shown to be beneficial.
Relevance This paper describes previously joint.
the beneficial effects of ankle disc training on two parameters found to be impaired among patients with functional instability of the ankle
Key words: Functional instability, Ankle disc, Pronators, Postural control
Introduction
Residual ankle disability is common after injury to the ankle joint”2. No single factor has been shown to be responsible”. We found previously4 that functional instability, i.e recurrent sprains or a feeling of giving way of the ankle, was correlated with impaired ability to maintain postural equilibrium as demonstrated by stabilometry. Pronator muscle weakness of the affected ankle compared to the normal ankle was found among patients with unilateral functional instability of the ankle joint’. In accordance with Freeman’s theories” of damage to proprioceptive mechanoreceptors, ankle disc training training on an has been suggested”.‘. Coordination ankle disc resulted in improved stabilometry results? and reduced rate of ankle sprains among soccer players’. The aim of the present study was to evaluate some of the mechanisms behind the effect of such training, and to establish some recommendations for the use of ankle disc training. Materials and methods
The series comprised 25 male soccer players in Division VI (the lowest division in the Swedish soccer league). All had functional instability of one or both ankle joints Submirred: 11 May 1987. In revised form: 26 November 1987. Correspondence and reprint requests IO: Dr H Tropp. Dept Orthopaedic Surgery, University Hospital, S-581 85 LinkGping. Sweden. 0 1988 Butterworth & Co (Publishers) Ltd 0268-0033/88/020088-04 $0340
were selected for individual coordination training using an ankle disc. Stabilometry is an objective and quantitative method for the study of postural control. The technique of stabilometry of single limb stance is described elsewhere4*“‘. The total force between foot and ground was measured with the subject standing on a forceplate (Kistler 9281A, Winterthur, Switzerland), and is the result of gravity and accelerations of body segments. The force plate measures both gravity forces and forces caused by the subject in keeping the line of gravity within the area of support. The coordinates of the intersection between the line of action of the total force and the surface of the plate were calculated. This point is called centre of pressure (CP). The mean value and standard deviations of coordinates in the x- and ydirections is calculated. The variation in coordinates is expressed as the area of the two-dimensional confidence ellipse at level l/de. This is an accordance with principles presented by Sahlstrand et al.“. The area of the ellipse is used as a statistical measure of the total amplitude of CP displacements, i.e. the stabilometric value for postural control. The recordings were made in a darkened room to exclude disturbing external stimuli. A light-rod situated 5 m in front of the subject served as a fixation mark; each recording lasted for 60 seconds. Recordings were made in two positions: (1) Standing on the right leg, with the left leg raised and flexed at the knee and the arms crossed over the chest; (2). As (l), but standing on the left foot. The recording in each and
Tropp and Askling:
position was done three times and the mean was calculated . Isokinetic muscle torque was measured with an isokinetic dynamometer (Cybex II, USA). To fuifil our demands we now used a test model other than the one previously described’2.‘3. We measured dorsi-flexion and eversion of the ankle because these motions are the most interesting for preventing inversion injuries14. Lightness of the level arm reduces both gravitational torque and moment of inertia. Torques other than those about the dynamometer axis were minimized by having the foot free on the lever rod. The subjects sat on a special couch stabilizing the upper trunk, thigh and leg with nonelastic straps. Dorsiflexion was recorded with the dynamometer aligned to the talocrural axis by tilting the dynamometer 8”, with an angle of 74” between the axis of rotation of the dynamometer and the sagittal plane through the midline of the foot15. Pronation was recorded with the dynamometer axis of rotation at an angle of 23” medial to the midline of the foot and angled 42” to the horizontal plane through the sole (Figure 1). There was an angle of 23” between the axis of rotation of the dynamometer and the sagittal plane through the foot. The device was tilted 8” forward. The foot hung free from the talocrural joint, and the muscles were relaxed. Attention was then paid to passive plantar flexion at the talocrural joint, altering the angle between the subtalar axis and the tibia. The knee was fixed to create an angle of 34” between the sole of the free-hanging foot and the floor. The angle between foot and floor was measured by a special device with a protractor. A 42” angle was thus obtained between the axis of rotation and the sole. The axis of rotation of the dynamometer was adjusted to the anterior tibialis tendon. The subject was asked to supinate the foot maximally and then to pronate it with maximum force. Because of its construction, the device records mainly eversion torque even though accessory motions such as dorsiflexion may occur. The torques for active dorsiflexion and pronation were recorded by means of a digital paper-writer (ES 1000). The peak torques for 30% and 120% angular velocity were calculated”.
Ankle disc training
Figure 2. The ankle disc used for coordination
89
training.
Functionally unstable joints were trained and studied. The subjects were trained standing on one leg on an ankle disc (LIC. Stockholm, Sweden), consisting of a segment of a sphere (Figure 2). The knee was maximally extended, the arms crossed over the chest, and the other leg raised and flexed at the knee. They were told to make corrections through the ankle if possible. During the first 10 weeks they trained 10 minutes a foot, five times each week. After 10 weeks they trained on each foot for 5 minutes, three times weekly. In 17 men, isokinetic muscle strength was measured initially and then after 10 weeks of training. Stabilometry recordings were made in all men initially and then after 6, 10, and 20 weeks of training. After 20 weeks of training the players completed the training and were examined 30 weeks later, i.e. 50 weeks after the start of the study. Following 10 weeks of training all men filled in a questionnaire rating the changes in their sensation of giving way at the ankle joint as: much worse, worse, unchanged, improved or greatly improved. The players were also asked about changes during the non-training period. A training effect for the test situation is described elsewhere16.“. In the present study a control group of 30 male soccer players underwent stabilometry on two occasions with a 6-week interval. This group performed the same soccer training as the test group, except for ankle disc training. They were also questioned about changes in symptoms. Testing of paired differences was done by sign test and paired r-test, which gave the same significance. Comparison of two samples was done by unpaired t-test and controlled with the Chi-square testlx. Data are given as means + standard deviations. Results
Figure 1. Biomechanical adjustment for isokinetic measurement of pronator muscle strength.
The initial stabilometry readings in the training group (Figure 3) were 317rt78mm2. A significant improvement took place during the first 6 and 10 weeks of
90
C/in. Biomech. 1999; 3: No 2 Torque
Arm
(m$
(Nm)
T
*T
360.
30 260-
200pco.001
150-
L-4
‘“1
1 p~o.ool
0
loo-
10
Time
tweekd Figure 5. lsokinetic muscle strength before and after 10 weeks of ankle disc training: A, dorsiflexion 30% n.s.; 0, dorsiflexion 120% p
soL
0
6
Figure 3. Stabilometry 20 weeks of training.
10
20
Time (weeks)
results initially and after 6,10 and
when the values fell to 250-+66 @
training,
KG 360 300 4
.
260
,
200. 150 loo
Discussion
so
I
0
6 lime (weeks)
Figure4. Stabilometry results before and after 6 weeks of training. Improvement was significantly better in the training group 0 than in the controls 0 (p
Ankle disc training improved both postural control (demonstrated here by stabilometry), and isokinetic pronator muscle strength. Both these factors are impaired in functional instability of the ankle joint’.“‘, though in a previous study’ the two factors were apparently unrelated. The improvement of postural control might involve central utilization of proprioceptive information and performance of adequate corrections. Imorovement in Ioronator muscle strength could 1
Tropp and Askling: Ankle disc training
reflect rehabilitation of atrophied muscle. The feeling of giving way was significantly reduced after 10 weeks of training. Even if our methods for subjective assessments might be considered inadequate, this improvement is nonetheless important for training motivation. A training period of 10 weeks seems to be sufficient to judge from results of stabilometry; further training had no beneficial effect. Brandt” reported success with balance training, but that acquired balance skills exponentially returned to pretraining values within weeks. However, in the present study neither subjective functional disability nor stabilometric values were impaired after the training period was completed. The lasting effect may be the result of continuing to play soccer. If the player should sustain a new ankle injury, with consequent immobilization and interruption of activity, this would probably negate the training effect and require a new rehabilitation period. The design of the disc is based on a sphere; corrections at the ankle are made through displacement of centre of pressure. Ankle disc training effects corrections of some of the factors important for functional instability, and should be valuable in rehabilitation of acute ankle injuries and chronic functional disability. Since a restricted period of training is sufficient, training seems to be superior to mechanical support.
5
6
7
8
9 10
11
12 13
14
15
References 1 Bosien WR, Staples OS, Russel SW. Residual disability following acute ankle sprains. J Bone Jt Surg 1955; 37A: 1237-43 2 Freeman MAR, Dean MRE, Hanham IEF. The etiology and prevention of functional instability of the foot. J Bone Joint Surg 1965; 47B: 669-77 3 Balduini FC, Tetzlaff J. Historical perspectives on injuries of the ligaments of the ankle. In: Torg JS ed. Ankle and foot problems in the athlete. Clinics in Sports Medicine 1982; 1: 3-12 4 Tropp H, Odenrick P, Gillquist J. Stabilometry
91
recordings in functional and mechanical instability of the ankle joint. Int J Sports Med 1988 (in press) Tropp H. Pronator muscle weakness in functional instability of the ankle joint. Med Sci Sports Med 1986: 7: 291-295 Fiore RD, Leard JS. A functional approach to the rehabilitation of the ankle and rear foot. Athletic Training 1980; 15: 231 Vegso JJ, Herman LE. Nonoperative management of athletic ankle injuries. In: Torg JS ed. Ankle and foot problems in the athlete. Clinics in Sports Medicine 1982; 1: 85-98 Tropp H, Ekstrand J, Gillquist J. Factors affecting stabilometry recordings on single limb stance. Am J Sports Med 1984; 12: 185-8 Tropp H, Askling C, Gillquist J. Prevention of ankle sprains. Am J Sports Med 1988 (in press) Tropp H, Ekstrand J, Gillquist J. Stabilometry in functional instability of the ankle and its value in predicting injury. Med Sci Sports Exercise 1984; 16: 64-6 Sahlstrand T, Ortengren R, Nachemson A. Postural equilibrium in adolescent idiopathic scoliosis. Acta Orthop Stand 1978; 49: 354-6.5 Isolated joint testing and exercise: A handbook for using Cybex II and U.B.X.T. New York: Lumex Inc. 1980 St. Pierre R, Andrews L, Allman F, Fleming LL. The Cybex II evaluation of lateral ankle ligamentous reconstructions. Am J Sports Med 1984; 12: 52-6 Kaumeyer G, Malone T. Ankle injuries: anatomical and biomechanical considerations necessary for the development of an injury prevention program. J Orthop .Sports Phys Ther 1980; 1: 171-l Oberg B, Bergman T, Tropp H. Testing of isokinetic muscle strength in the ankle. Med Sci Sports Exert 1987; 19: 395-98
16 Black FO, Wall C. Rockette HE, Russel K. Normal subject sway during the Romberg test. Am J Otolaryngol 1982; 3: 309-W 17 Holliday PJ, Fernie GR. Changes in the measurement of postural sway resulting from repeated testing. Agressologie 1979; 4: 225-8 18 Swinscow TDV. Statistics at square one. London: Br Med Assoc 1976 19 Brandt Th, Krafczyk S. Malsbenden I. Postural imbalance with head extension: improvement by training as a model for ataxia therapy. Ann NY Acad Sci 1981; 374: 636-9
1988; 3: 88-91
Effects of ankle disc training on muscular strength and postural control Hans Tropp Carl Askling Departments
MD RPT
of Clinical Neurophysiology
and Orthopaedic
Surgery, University Hospital, Linkdping, Sweden
Summary Ankle disc training gave good objective results in patients with functional instability of the ankle joint, that is a feeling of giving way or recurrent sprains. The training programme improved both postural control, as demonstrated by stabilometry, and isokinetic pronator muscle strength. A lo-week training period was apparently sufficient, and further training could not be shown to be beneficial.
Relevance This paper describes previously joint.
the beneficial effects of ankle disc training on two parameters found to be impaired among patients with functional instability of the ankle
Key words: Functional instability, Ankle disc, Pronators, Postural control
Introduction
Residual ankle disability is common after injury to the ankle joint”2. No single factor has been shown to be responsible”. We found previously4 that functional instability, i.e recurrent sprains or a feeling of giving way of the ankle, was correlated with impaired ability to maintain postural equilibrium as demonstrated by stabilometry. Pronator muscle weakness of the affected ankle compared to the normal ankle was found among patients with unilateral functional instability of the ankle joint’. In accordance with Freeman’s theories” of damage to proprioceptive mechanoreceptors, ankle disc training training on an has been suggested”.‘. Coordination ankle disc resulted in improved stabilometry results? and reduced rate of ankle sprains among soccer players’. The aim of the present study was to evaluate some of the mechanisms behind the effect of such training, and to establish some recommendations for the use of ankle disc training. Materials and methods
The series comprised 25 male soccer players in Division VI (the lowest division in the Swedish soccer league). All had functional instability of one or both ankle joints Submirred: 11 May 1987. In revised form: 26 November 1987. Correspondence and reprint requests IO: Dr H Tropp. Dept Orthopaedic Surgery, University Hospital, S-581 85 LinkGping. Sweden. 0 1988 Butterworth & Co (Publishers) Ltd 0268-0033/88/020088-04 $0340
were selected for individual coordination training using an ankle disc. Stabilometry is an objective and quantitative method for the study of postural control. The technique of stabilometry of single limb stance is described elsewhere4*“‘. The total force between foot and ground was measured with the subject standing on a forceplate (Kistler 9281A, Winterthur, Switzerland), and is the result of gravity and accelerations of body segments. The force plate measures both gravity forces and forces caused by the subject in keeping the line of gravity within the area of support. The coordinates of the intersection between the line of action of the total force and the surface of the plate were calculated. This point is called centre of pressure (CP). The mean value and standard deviations of coordinates in the x- and ydirections is calculated. The variation in coordinates is expressed as the area of the two-dimensional confidence ellipse at level l/de. This is an accordance with principles presented by Sahlstrand et al.“. The area of the ellipse is used as a statistical measure of the total amplitude of CP displacements, i.e. the stabilometric value for postural control. The recordings were made in a darkened room to exclude disturbing external stimuli. A light-rod situated 5 m in front of the subject served as a fixation mark; each recording lasted for 60 seconds. Recordings were made in two positions: (1) Standing on the right leg, with the left leg raised and flexed at the knee and the arms crossed over the chest; (2). As (l), but standing on the left foot. The recording in each and
Tropp and Askling:
position was done three times and the mean was calculated . Isokinetic muscle torque was measured with an isokinetic dynamometer (Cybex II, USA). To fuifil our demands we now used a test model other than the one previously described’2.‘3. We measured dorsi-flexion and eversion of the ankle because these motions are the most interesting for preventing inversion injuries14. Lightness of the level arm reduces both gravitational torque and moment of inertia. Torques other than those about the dynamometer axis were minimized by having the foot free on the lever rod. The subjects sat on a special couch stabilizing the upper trunk, thigh and leg with nonelastic straps. Dorsiflexion was recorded with the dynamometer aligned to the talocrural axis by tilting the dynamometer 8”, with an angle of 74” between the axis of rotation of the dynamometer and the sagittal plane through the midline of the foot15. Pronation was recorded with the dynamometer axis of rotation at an angle of 23” medial to the midline of the foot and angled 42” to the horizontal plane through the sole (Figure 1). There was an angle of 23” between the axis of rotation of the dynamometer and the sagittal plane through the foot. The device was tilted 8” forward. The foot hung free from the talocrural joint, and the muscles were relaxed. Attention was then paid to passive plantar flexion at the talocrural joint, altering the angle between the subtalar axis and the tibia. The knee was fixed to create an angle of 34” between the sole of the free-hanging foot and the floor. The angle between foot and floor was measured by a special device with a protractor. A 42” angle was thus obtained between the axis of rotation and the sole. The axis of rotation of the dynamometer was adjusted to the anterior tibialis tendon. The subject was asked to supinate the foot maximally and then to pronate it with maximum force. Because of its construction, the device records mainly eversion torque even though accessory motions such as dorsiflexion may occur. The torques for active dorsiflexion and pronation were recorded by means of a digital paper-writer (ES 1000). The peak torques for 30% and 120% angular velocity were calculated”.
Ankle disc training
Figure 2. The ankle disc used for coordination
89
training.
Functionally unstable joints were trained and studied. The subjects were trained standing on one leg on an ankle disc (LIC. Stockholm, Sweden), consisting of a segment of a sphere (Figure 2). The knee was maximally extended, the arms crossed over the chest, and the other leg raised and flexed at the knee. They were told to make corrections through the ankle if possible. During the first 10 weeks they trained 10 minutes a foot, five times each week. After 10 weeks they trained on each foot for 5 minutes, three times weekly. In 17 men, isokinetic muscle strength was measured initially and then after 10 weeks of training. Stabilometry recordings were made in all men initially and then after 6, 10, and 20 weeks of training. After 20 weeks of training the players completed the training and were examined 30 weeks later, i.e. 50 weeks after the start of the study. Following 10 weeks of training all men filled in a questionnaire rating the changes in their sensation of giving way at the ankle joint as: much worse, worse, unchanged, improved or greatly improved. The players were also asked about changes during the non-training period. A training effect for the test situation is described elsewhere16.“. In the present study a control group of 30 male soccer players underwent stabilometry on two occasions with a 6-week interval. This group performed the same soccer training as the test group, except for ankle disc training. They were also questioned about changes in symptoms. Testing of paired differences was done by sign test and paired r-test, which gave the same significance. Comparison of two samples was done by unpaired t-test and controlled with the Chi-square testlx. Data are given as means + standard deviations. Results
Figure 1. Biomechanical adjustment for isokinetic measurement of pronator muscle strength.
The initial stabilometry readings in the training group (Figure 3) were 317rt78mm2. A significant improvement took place during the first 6 and 10 weeks of
90
C/in. Biomech. 1999; 3: No 2 Torque
Arm
(m$
(Nm)
T
*T
360.
30 260-
200pco.001
150-
L-4
‘“1
1 p~o.ool
0
loo-
10
Time
tweekd Figure 5. lsokinetic muscle strength before and after 10 weeks of ankle disc training: A, dorsiflexion 30% n.s.; 0, dorsiflexion 120% p
soL
0
6
Figure 3. Stabilometry 20 weeks of training.
10
20
Time (weeks)
results initially and after 6,10 and
when the values fell to 250-+66 @
training,
KG 360 300 4
.
260
,
200. 150 loo
Discussion
so
I
0
6 lime (weeks)
Figure4. Stabilometry results before and after 6 weeks of training. Improvement was significantly better in the training group 0 than in the controls 0 (p
Ankle disc training improved both postural control (demonstrated here by stabilometry), and isokinetic pronator muscle strength. Both these factors are impaired in functional instability of the ankle joint’.“‘, though in a previous study’ the two factors were apparently unrelated. The improvement of postural control might involve central utilization of proprioceptive information and performance of adequate corrections. Imorovement in Ioronator muscle strength could 1
Tropp and Askling: Ankle disc training
reflect rehabilitation of atrophied muscle. The feeling of giving way was significantly reduced after 10 weeks of training. Even if our methods for subjective assessments might be considered inadequate, this improvement is nonetheless important for training motivation. A training period of 10 weeks seems to be sufficient to judge from results of stabilometry; further training had no beneficial effect. Brandt” reported success with balance training, but that acquired balance skills exponentially returned to pretraining values within weeks. However, in the present study neither subjective functional disability nor stabilometric values were impaired after the training period was completed. The lasting effect may be the result of continuing to play soccer. If the player should sustain a new ankle injury, with consequent immobilization and interruption of activity, this would probably negate the training effect and require a new rehabilitation period. The design of the disc is based on a sphere; corrections at the ankle are made through displacement of centre of pressure. Ankle disc training effects corrections of some of the factors important for functional instability, and should be valuable in rehabilitation of acute ankle injuries and chronic functional disability. Since a restricted period of training is sufficient, training seems to be superior to mechanical support.
5
6
7
8
9 10
11
12 13
14
15
References 1 Bosien WR, Staples OS, Russel SW. Residual disability following acute ankle sprains. J Bone Jt Surg 1955; 37A: 1237-43 2 Freeman MAR, Dean MRE, Hanham IEF. The etiology and prevention of functional instability of the foot. J Bone Joint Surg 1965; 47B: 669-77 3 Balduini FC, Tetzlaff J. Historical perspectives on injuries of the ligaments of the ankle. In: Torg JS ed. Ankle and foot problems in the athlete. Clinics in Sports Medicine 1982; 1: 3-12 4 Tropp H, Odenrick P, Gillquist J. Stabilometry
91
recordings in functional and mechanical instability of the ankle joint. Int J Sports Med 1988 (in press) Tropp H. Pronator muscle weakness in functional instability of the ankle joint. Med Sci Sports Med 1986: 7: 291-295 Fiore RD, Leard JS. A functional approach to the rehabilitation of the ankle and rear foot. Athletic Training 1980; 15: 231 Vegso JJ, Herman LE. Nonoperative management of athletic ankle injuries. In: Torg JS ed. Ankle and foot problems in the athlete. Clinics in Sports Medicine 1982; 1: 85-98 Tropp H, Ekstrand J, Gillquist J. Factors affecting stabilometry recordings on single limb stance. Am J Sports Med 1984; 12: 185-8 Tropp H, Askling C, Gillquist J. Prevention of ankle sprains. Am J Sports Med 1988 (in press) Tropp H, Ekstrand J, Gillquist J. Stabilometry in functional instability of the ankle and its value in predicting injury. Med Sci Sports Exercise 1984; 16: 64-6 Sahlstrand T, Ortengren R, Nachemson A. Postural equilibrium in adolescent idiopathic scoliosis. Acta Orthop Stand 1978; 49: 354-6.5 Isolated joint testing and exercise: A handbook for using Cybex II and U.B.X.T. New York: Lumex Inc. 1980 St. Pierre R, Andrews L, Allman F, Fleming LL. The Cybex II evaluation of lateral ankle ligamentous reconstructions. Am J Sports Med 1984; 12: 52-6 Kaumeyer G, Malone T. Ankle injuries: anatomical and biomechanical considerations necessary for the development of an injury prevention program. J Orthop .Sports Phys Ther 1980; 1: 171-l Oberg B, Bergman T, Tropp H. Testing of isokinetic muscle strength in the ankle. Med Sci Sports Exert 1987; 19: 395-98
16 Black FO, Wall C. Rockette HE, Russel K. Normal subject sway during the Romberg test. Am J Otolaryngol 1982; 3: 309-W 17 Holliday PJ, Fernie GR. Changes in the measurement of postural sway resulting from repeated testing. Agressologie 1979; 4: 225-8 18 Swinscow TDV. Statistics at square one. London: Br Med Assoc 1976 19 Brandt Th, Krafczyk S. Malsbenden I. Postural imbalance with head extension: improvement by training as a model for ataxia therapy. Ann NY Acad Sci 1981; 374: 636-9