1. Biomrchanics Printed in Grtat
Vol. 23, No. 10. pp. 100-1011, Britain
1990.
WRIST LOADING
KEITEI
0
PATTERNS DURING EXERCISES
POMMEL
0021-9290/W 1990 Pe~OIl
S3.00+ .oO Fvaa plc
HORSE
L. MARKOLF, MATTHEW S. SHAPIRO, BERT R. MANDELBAUMand Luc TEURLINGS
Biomechanics Research Section, Division of Orthopaedic Surgery, University of California at Los Angeles, 1000 Veteran Ave., Los Angeles, CA 90024, U.S.A. Ahatraet-Gymnastics is a sport which involves substantial periods of upper extremity support as well as frequent impacts to the wrist. Not surprisingly, wrist pain is a common finding in gymnasts. Of all events, the pommel horse is the most painful. In order to study the forces of wrist impact, a standard pommel horse was instrumented with a specially designed load cell to record the resultant force of the hand on the pommel during a series of basic skills performed by a group of seventeen elite male gymnasts. The highest mean peak forces were recorded during the front scissors and flair exercises (1.5 BW) with peaks of up to 2.0 BW for some gymnasts. The mean peak force for hip circles at the center or end of the horse was 1.1 BW. The mean overall loading rate (initial contact to first loading peak) ranged from 5.2 BW s- 1(hip circles)to 10.6 BW s- ’ (flairs). However, many recordings displayed local&d initial loading spikes which occurred during ‘hard landings on the pommel. When front scissors were performed in an aggressive manner, the initial loading spikes averaged 1.0 BW in magnitude (maximum 1.8 BW) with an average rise time of 8.2 ms; calculated localized loading rates averaged 129 BW s-l (maximum 219 BW s- ‘). These loading parameters are comparable to those encountered at heel strike during running. These impact forces and loading rates are remarkably high for an upper extremity joint not normally exposed to weight-bearing loads, and may contribute to the pathogenesis of wrist injuries in gymnastics.
INTRODUCTION
CYmnastics is unique among all athletic endeavors in the demands it Places on the upper extremity. Men’s gymnastics is comprised of six events, all of which Produce loadings to the wrist. Horizontal bars and rings involve largely suspensory forces in the upper extremity. Floor exercises call for a mixture of upper and lower extremity weight bearing but are performed on a padded and spring-loaded surface. Exem&s on the parallel bars involve upper extremity weight bearing, but the bars are flexible, and capable of attenuating much of the force of @act. While vaulting calls for a single, explosive upper extremity thrust off a firm padded surface, the total number of executions is relatively low. Only the pommel horse demands repetitive, high iIItenSity Wrist hIpaCtS on a rigid structure, with sustained periods of body weight support on the wrist. Not sui’Prisin@Y, wrist problems are Prevalent in men’s gymnastics. In a recent study of elite male gymnasts (Mandelbaum et 4 1989), the pommel horse was the apparatus associated with the most wrist pain. Eighty-eight per cent of these gymnasts complained of wrist pain, while fifty-eight per cent of them required chronic non-steroidal anti-inflammatory drugs to continue participation. The mean amount of positive ulnar variance for this group of gymnasts was greater than that for an age-matched group of controls. Ulnar variance is defined as the height difference between the articular surfaces at the distal radial-ulnar joint. Positive ulnar variance implies that the ulna is relatively longer than the radius, as determined from a radiograph at neutral rotation. Received infinalform 13 March 1990.
Since many gymnasts start training and competing at a very young age (most between the ages of 5 and lo), a developmental etiology for the observed ulnar variance has been proposed (Mandelbaum et al., 1989). These authors believe that repetitive injury to the radial epiphysis prior to skeletal maturity results in premature closure of the growth plate. Evidence to support this notion comes from several case reports which note radiographic changes in the distal radial epiphyses of young gymnasts. Findings of growth plate widening, metaphyseal cyst formation, and epiphyseal beaking have been related to high stresses placed on the developing wrist (Carter and Aldridge, 1988; ROY et al., 1985). Albanese et d. (1989) noted premature closure of the radial growth plate in three skeletally immature gymnasts, and proposed that these findings are related to repetitive corn-pressive impacts on the distal radius. Progressive radial shortening, with concomitant relative ulnar lengthening, could alter the load transmission in the wrist joint. This could predispose the gymnast’s wrist to injury, particularly on the ulnar side of the wrist where the triangular fibrocartilaginous complex (TFCC) resides. A study done on 36 cadaver forearms found that 73% of wrists with neutral-positive ulnar variance had perforations of the TFCC and lunate or ulnar erosions, while only 17% of the wrists with negative ulnar variance had such findings (Palmer and Werner, 1981). This study suggests that relative positive ulnar variance may be associated with soft tissue injuries to the ulnar side of the wrist. Although a direct cause and effect relationship between high wrist forces and observed pathology has not been established to date, our discussions with elite gymnasts have led us to believe that the pommel horse activity not only aggravates their existing wrist pain,
1001
K. L. MARKOLF
1002
but may have contributed to an over-use syndrome which created the painful condition. This led us to ask what are the magnitudes and rates of wrist forces generated during this activity, and how do they compare with those generated during lower extremity impacts such as running? We hypothesize that wrist forces during pommel horse activity are unusually high for a joint which does not normally experience high intensity compressive impacts. The forces in the wrist during pommel horse exercises are unknown; we have found no published studies describing wrist forces during any gymnastic activity. The purpose of this study was to measure the force exerted by the hand on the pommel during a series of side horse skills in a group of elite male gymnasts. METHODS
et al.
weight was borne on an extended wrist placed flat on the horse body. In general, the pain was intensified when they experienced a ‘hard landing’ on the pommel or when an exercise was performed with high intensity in an aggressive manner. They could not describe which phase of the support cycle was most painful. Each gymnast performed a specific exercise a minimum of three consecutive times with both the dominant and non-dominant hands on the pommel. The dominant hand in gymnastics may be opposite the hand used for writing. It is the hand which the gymnast uses to initiate most of the more difficult exercises on the pommel horse. For the hip circle exercise, the dominant hand was defined as the right hand ifthe gymnast performed hip circles in a counterclockwise direction (as viewed from above), and as the left hand if he circled the horse clockwise. All gymnasts executed hip circles in their preferred directions. Uphill and downhill circles are performed on the end of the horse, with one hand on the end of the horse body, and the other hand on the pommel. By gymnastics convention, when performing hip circles on the end of the horse, a circle was defined as uphill when the dominant hand contacted the instrumented pommel, and as downhill for non-dominant hand contact with the pommel. Front scissors (at the center of the horse) were executed by all gymnasts. Thomas Flairs (a complex combination of hip circles and scissors) were performed by ten gymnasts at the center of the horse. All gymnasts were asked if the instrumented pommel ‘felt different’ in any way which would alter the execution of their exercise: none said that it did. Pommel force data were collected during the above exercises at a sampling rate of 200 HZ using a corn-puterized data acquisition system. In order to more closely study the rate of loading during initial hand contact, additional recordings were taken only during initial impact at a sampling rate of 2000 HZ. In these trials, recordings were taken during 37 scissors and 21 hip circle exercises performed by a single gymnast only; high data rate recordings were not taken for all 17 gymnasts. All calculated resultant forces were scaled to each gymnast’s body weight (BW). Four parameters were analyzed for each exercise: (1) loading rate during the initial contact of the hand and the pommel; (2) peak force attained during the support phase; (3) impulse during pommel contact; and (4) duration of pommel support. An analysis of variance model was used to test for differences in a given parameter between exercises, and for differences in a given parameter between hands for a specific exercise. The significance level for these comparisons was chosen as p
Vol. 23, No. 10. pp. 100-1011, Britain
1990.
WRIST LOADING
KEITEI
0
PATTERNS DURING EXERCISES
POMMEL
0021-9290/W 1990 Pe~OIl
S3.00+ .oO Fvaa plc
HORSE
L. MARKOLF, MATTHEW S. SHAPIRO, BERT R. MANDELBAUMand Luc TEURLINGS
Biomechanics Research Section, Division of Orthopaedic Surgery, University of California at Los Angeles, 1000 Veteran Ave., Los Angeles, CA 90024, U.S.A. Ahatraet-Gymnastics is a sport which involves substantial periods of upper extremity support as well as frequent impacts to the wrist. Not surprisingly, wrist pain is a common finding in gymnasts. Of all events, the pommel horse is the most painful. In order to study the forces of wrist impact, a standard pommel horse was instrumented with a specially designed load cell to record the resultant force of the hand on the pommel during a series of basic skills performed by a group of seventeen elite male gymnasts. The highest mean peak forces were recorded during the front scissors and flair exercises (1.5 BW) with peaks of up to 2.0 BW for some gymnasts. The mean peak force for hip circles at the center or end of the horse was 1.1 BW. The mean overall loading rate (initial contact to first loading peak) ranged from 5.2 BW s- 1(hip circles)to 10.6 BW s- ’ (flairs). However, many recordings displayed local&d initial loading spikes which occurred during ‘hard landings on the pommel. When front scissors were performed in an aggressive manner, the initial loading spikes averaged 1.0 BW in magnitude (maximum 1.8 BW) with an average rise time of 8.2 ms; calculated localized loading rates averaged 129 BW s-l (maximum 219 BW s- ‘). These loading parameters are comparable to those encountered at heel strike during running. These impact forces and loading rates are remarkably high for an upper extremity joint not normally exposed to weight-bearing loads, and may contribute to the pathogenesis of wrist injuries in gymnastics.
INTRODUCTION
CYmnastics is unique among all athletic endeavors in the demands it Places on the upper extremity. Men’s gymnastics is comprised of six events, all of which Produce loadings to the wrist. Horizontal bars and rings involve largely suspensory forces in the upper extremity. Floor exercises call for a mixture of upper and lower extremity weight bearing but are performed on a padded and spring-loaded surface. Exem&s on the parallel bars involve upper extremity weight bearing, but the bars are flexible, and capable of attenuating much of the force of @act. While vaulting calls for a single, explosive upper extremity thrust off a firm padded surface, the total number of executions is relatively low. Only the pommel horse demands repetitive, high iIItenSity Wrist hIpaCtS on a rigid structure, with sustained periods of body weight support on the wrist. Not sui’Prisin@Y, wrist problems are Prevalent in men’s gymnastics. In a recent study of elite male gymnasts (Mandelbaum et 4 1989), the pommel horse was the apparatus associated with the most wrist pain. Eighty-eight per cent of these gymnasts complained of wrist pain, while fifty-eight per cent of them required chronic non-steroidal anti-inflammatory drugs to continue participation. The mean amount of positive ulnar variance for this group of gymnasts was greater than that for an age-matched group of controls. Ulnar variance is defined as the height difference between the articular surfaces at the distal radial-ulnar joint. Positive ulnar variance implies that the ulna is relatively longer than the radius, as determined from a radiograph at neutral rotation. Received infinalform 13 March 1990.
Since many gymnasts start training and competing at a very young age (most between the ages of 5 and lo), a developmental etiology for the observed ulnar variance has been proposed (Mandelbaum et al., 1989). These authors believe that repetitive injury to the radial epiphysis prior to skeletal maturity results in premature closure of the growth plate. Evidence to support this notion comes from several case reports which note radiographic changes in the distal radial epiphyses of young gymnasts. Findings of growth plate widening, metaphyseal cyst formation, and epiphyseal beaking have been related to high stresses placed on the developing wrist (Carter and Aldridge, 1988; ROY et al., 1985). Albanese et d. (1989) noted premature closure of the radial growth plate in three skeletally immature gymnasts, and proposed that these findings are related to repetitive corn-pressive impacts on the distal radius. Progressive radial shortening, with concomitant relative ulnar lengthening, could alter the load transmission in the wrist joint. This could predispose the gymnast’s wrist to injury, particularly on the ulnar side of the wrist where the triangular fibrocartilaginous complex (TFCC) resides. A study done on 36 cadaver forearms found that 73% of wrists with neutral-positive ulnar variance had perforations of the TFCC and lunate or ulnar erosions, while only 17% of the wrists with negative ulnar variance had such findings (Palmer and Werner, 1981). This study suggests that relative positive ulnar variance may be associated with soft tissue injuries to the ulnar side of the wrist. Although a direct cause and effect relationship between high wrist forces and observed pathology has not been established to date, our discussions with elite gymnasts have led us to believe that the pommel horse activity not only aggravates their existing wrist pain,
1001
K. L. MARKOLF
1002
but may have contributed to an over-use syndrome which created the painful condition. This led us to ask what are the magnitudes and rates of wrist forces generated during this activity, and how do they compare with those generated during lower extremity impacts such as running? We hypothesize that wrist forces during pommel horse activity are unusually high for a joint which does not normally experience high intensity compressive impacts. The forces in the wrist during pommel horse exercises are unknown; we have found no published studies describing wrist forces during any gymnastic activity. The purpose of this study was to measure the force exerted by the hand on the pommel during a series of side horse skills in a group of elite male gymnasts. METHODS
et al.
weight was borne on an extended wrist placed flat on the horse body. In general, the pain was intensified when they experienced a ‘hard landing’ on the pommel or when an exercise was performed with high intensity in an aggressive manner. They could not describe which phase of the support cycle was most painful. Each gymnast performed a specific exercise a minimum of three consecutive times with both the dominant and non-dominant hands on the pommel. The dominant hand in gymnastics may be opposite the hand used for writing. It is the hand which the gymnast uses to initiate most of the more difficult exercises on the pommel horse. For the hip circle exercise, the dominant hand was defined as the right hand ifthe gymnast performed hip circles in a counterclockwise direction (as viewed from above), and as the left hand if he circled the horse clockwise. All gymnasts executed hip circles in their preferred directions. Uphill and downhill circles are performed on the end of the horse, with one hand on the end of the horse body, and the other hand on the pommel. By gymnastics convention, when performing hip circles on the end of the horse, a circle was defined as uphill when the dominant hand contacted the instrumented pommel, and as downhill for non-dominant hand contact with the pommel. Front scissors (at the center of the horse) were executed by all gymnasts. Thomas Flairs (a complex combination of hip circles and scissors) were performed by ten gymnasts at the center of the horse. All gymnasts were asked if the instrumented pommel ‘felt different’ in any way which would alter the execution of their exercise: none said that it did. Pommel force data were collected during the above exercises at a sampling rate of 200 HZ using a corn-puterized data acquisition system. In order to more closely study the rate of loading during initial hand contact, additional recordings were taken only during initial impact at a sampling rate of 2000 HZ. In these trials, recordings were taken during 37 scissors and 21 hip circle exercises performed by a single gymnast only; high data rate recordings were not taken for all 17 gymnasts. All calculated resultant forces were scaled to each gymnast’s body weight (BW). Four parameters were analyzed for each exercise: (1) loading rate during the initial contact of the hand and the pommel; (2) peak force attained during the support phase; (3) impulse during pommel contact; and (4) duration of pommel support. An analysis of variance model was used to test for differences in a given parameter between exercises, and for differences in a given parameter between hands for a specific exercise. The significance level for these comparisons was chosen as p
